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Elul D, Levin N. The Role of Population Receptive Field Sizes in Higher-Order Visual Dysfunction. Curr Neurol Neurosci Rep 2024:10.1007/s11910-024-01375-6. [PMID: 39266871 DOI: 10.1007/s11910-024-01375-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/31/2024] [Indexed: 09/14/2024]
Abstract
PURPOSE OF REVIEW Population receptive field (pRF) modeling is an fMRI technique used to retinotopically map visual cortex, with pRF size characterizing the degree of spatial integration. In clinical populations, most pRF mapping research has focused on damage to visual system inputs. Herein, we highlight recent work using pRF modeling to study high-level visual dysfunctions. RECENT FINDINGS Larger pRF sizes, indicating coarser spatial processing, were observed in homonymous visual field deficits, aging, and autism spectrum disorder. Smaller pRF sizes, indicating finer processing, were observed in Alzheimer's disease and schizophrenia. In posterior cortical atrophy, a unique pattern was found in which pRF size changes depended on eccentricity. Changes to pRF properties were observed in clinical populations, even in high-order impairments, explaining visual behavior. These pRF changes likely stem from altered interactions between brain regions. Furthermore, some studies suggested that pRF sizes change as part of cortical reorganization, and they can point towards future prognosis.
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Affiliation(s)
- Deena Elul
- fMRI Unit, Neurology Department Hadassah Medical Organization, Faculty of Medicine, The Hebrew University of Jerusalem, POB 12000, Jerusalem, 91120, Israel
- Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Netta Levin
- fMRI Unit, Neurology Department Hadassah Medical Organization, Faculty of Medicine, The Hebrew University of Jerusalem, POB 12000, Jerusalem, 91120, Israel.
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2
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Ashtari M, Bennett J, Leopold DA. Central visual pathways affected by degenerative retinal disease before and after gene therapy. Brain 2024; 147:3234-3246. [PMID: 38538211 PMCID: PMC11370797 DOI: 10.1093/brain/awae096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 02/09/2024] [Accepted: 02/20/2024] [Indexed: 09/04/2024] Open
Abstract
Genetic diseases affecting the retina can result in partial or complete loss of visual function. Leber's congenital amaurosis (LCA) is a rare blinding disease, usually inherited in an autosomally recessive manner, with no cure. Retinal gene therapy has been shown to improve vision in LCA patients caused by mutations in the RPE65 gene (LCA2). However, little is known about how activity in central visual pathways is affected by the disease or by subsequent gene therapy. Functional MRI (fMRI) was used to assess retinal signal transmission in cortical and subcortical visual structures before and 1 year after retinal intervention. The fMRI paradigm consisted of 15-s blocks of flickering (8 Hz) black and white checkerboards interleaved with 15 s of blank (black) screen. Visual activation in the brain was assessed using the general linear model, with multiple comparisons corrected using the false discovery rate method. Response to visual stimulation through untreated eyes of LCA2 patients showed heightened fMRI responses in the superior colliculus and diminished activities in the lateral geniculate nucleus (LGN) compared to controls, indicating a shift in the patients' visual processing towards the retinotectal pathway. Following gene therapy, stimuli presented to the treated eye elicited significantly stronger fMRI responses in the LGN and primary visual cortex, indicating some re-engagement of the geniculostriate pathway (GS) pathway. Across patients, the post-treatment LGN fMRI responses correlated significantly with performance on a clinical test measuring light sensitivity. Our results demonstrate that the low vision observed in LCA2 patients involves a shift in visual processing toward the retinotectal pathway, and that gene therapy partially reinstates visual transmission through the GS pathway. This selective boosting of retinal output through the GS pathway and its correlation to improved visual performance, following several years of degenerative retinal disease, is striking. However, while retinal gene therapy and other ocular interventions have given hope to RPE65 patients, it may take years before development of therapies tailored to treat the diseases in other low vision patients are available. Our demonstration of a shift toward the retinotectal pathway in these patients may spur the development of new tools and rehabilitation strategies to help maximize the use of residual visual abilities and augment experience-dependent plasticity.
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Affiliation(s)
- Manzar Ashtari
- Center for Advanced Retinal and Ocular Therapeutics (CAROT), University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jean Bennett
- Center for Advanced Retinal and Ocular Therapeutics (CAROT), University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David A Leopold
- Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
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3
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Lane TJ, Liou TH, Kung YC, Tseng P, Wu CW. Functional blindsight and its diagnosis. Front Neurol 2024; 15:1207115. [PMID: 38385044 PMCID: PMC10879618 DOI: 10.3389/fneur.2024.1207115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 01/22/2024] [Indexed: 02/23/2024] Open
Abstract
Even when brain scans fail to detect a striate lesion, functional evidence for blindsight can be adduced. In the aftermath of an automobile accident, JK became blind. Results of ophthalmic exams indicated that the blindness must be cortical. Nevertheless, multiple MRI scans failed to detect structural damage to the striate cortex. Prior to the accident JK had been an athlete; after the accident he retained some athletic abilities, arousing suspicions that he might be engaged in fraud. His residual athletic abilities-e.g., hitting a handball or baseball, or catching a Frisbee-coupled with his experienced blindness, suggested blindsight. But due to the apparent absence of striate lesions, we designed a series of tasks for temporal and spatial dimensions in an attempt to detect functional evidence of his disability. Indeed, test results revealed compelling neural evidence that comport with his subjective reports. This spatiotemporal task-related method that includes contrasts with healthy controls, and detailed understanding of the patient's conscious experience, can be generalized for clinical, scientific and forensic investigations of blindsight.
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Affiliation(s)
- Timothy Joseph Lane
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Brain and Consciousness Research Centre, Taipei Medical University, Taipei City, Taiwan
- Institute of European and American Studies, Academia Sinica, Taipei City, Taiwan
| | - Tsan-Hon Liou
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Department of Physical Medicine and Rehabilitation, School of Medicine, College of Medicine, Taipei Medical University, Taipei City, Taiwan
- Department of Physical Medicine and Rehabilitation, TMU Shuang Ho Hospital, New Taipei City, Taiwan
| | - Yi-Chia Kung
- Department of Radiology, National Defense Medical Center, Tri-Service General Hospital, Taipei City, Taiwan
- Taiwan Institute of Neuroscience, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
| | - Philip Tseng
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Brain and Consciousness Research Centre, Taipei Medical University, Taipei City, Taiwan
- Department of Psychology, National Taiwan University, Taipei City, Taiwan
- Research Center for Mind, Brain and Learning, National Chengchi University, Taipei City, Taiwan
| | - Changwei W. Wu
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Brain and Consciousness Research Centre, Taipei Medical University, Taipei City, Taiwan
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4
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Willis HE, Ip IB, Watt A, Campbell J, Jbabdi S, Clarke WT, Cavanaugh MR, Huxlin KR, Watkins KE, Tamietto M, Bridge H. GABA and Glutamate in hMT+ Link to Individual Differences in Residual Visual Function After Occipital Stroke. Stroke 2023; 54:2286-2295. [PMID: 37477008 PMCID: PMC10453332 DOI: 10.1161/strokeaha.123.043269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 05/09/2023] [Accepted: 05/31/2023] [Indexed: 07/22/2023]
Abstract
BACKGROUND Damage to the primary visual cortex following an occipital stroke causes loss of conscious vision in the contralateral hemifield. Yet, some patients retain the ability to detect moving visual stimuli within their blind field. The present study asked whether such individual differences in blind field perception following loss of primary visual cortex could be explained by the concentration of neurotransmitters γ-aminobutyric acid (GABA) and glutamate or activity of the visual motion processing, human middle temporal complex (hMT+). METHODS We used magnetic resonance imaging in 19 patients with chronic occipital stroke to measure the concentration of neurotransmitters GABA and glutamate (proton magnetic resonance spectroscopy) and functional activity in hMT+ (functional magnetic resonance imaging). We also tested each participant on a 2-interval forced choice detection task using high-contrast, moving Gabor patches. We then measured and assessed the strength of relationships between participants' residual vision in their blind field and in vivo neurotransmitter concentrations, as well as visually evoked functional magnetic resonance imaging activity in their hMT+. Levels of GABA and glutamate were also measured in a sensorimotor region, which served as a control. RESULTS Magnetic resonance spectroscopy-derived GABA and glutamate concentrations in hMT+ (but not sensorimotor cortex) strongly predicted blind-field visual detection abilities. Performance was inversely related to levels of both inhibitory and excitatory neurotransmitters in hMT+ but, surprisingly, did not correlate with visually evoked blood oxygenation level-dependent signal change in this motion-sensitive region. CONCLUSIONS Levels of GABA and glutamate in hMT+ appear to provide superior information about motion detection capabilities inside perimetrically defined blind fields compared to blood oxygenation level-dependent signal changes-in essence, serving as biomarkers for the quality of residual visual processing in the blind-field. Whether they also reflect a potential for successful rehabilitation of visual function remains to be determined.
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Affiliation(s)
- Hanna E. Willis
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences (H.E.W., I.B.I., A.W., J.C., S.J., W.T.C., H.B.), University of Oxford, United Kingdom
| | - I. Betina Ip
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences (H.E.W., I.B.I., A.W., J.C., S.J., W.T.C., H.B.), University of Oxford, United Kingdom
| | - Archie Watt
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences (H.E.W., I.B.I., A.W., J.C., S.J., W.T.C., H.B.), University of Oxford, United Kingdom
| | - Jon Campbell
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences (H.E.W., I.B.I., A.W., J.C., S.J., W.T.C., H.B.), University of Oxford, United Kingdom
| | - Saad Jbabdi
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences (H.E.W., I.B.I., A.W., J.C., S.J., W.T.C., H.B.), University of Oxford, United Kingdom
| | - William T. Clarke
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences (H.E.W., I.B.I., A.W., J.C., S.J., W.T.C., H.B.), University of Oxford, United Kingdom
| | - Matthew R. Cavanaugh
- Flaum Eye Institute and Center for Visual Science, University of Rochester, NY (M.R.C., K.R.H.)
| | - Krystel R. Huxlin
- Flaum Eye Institute and Center for Visual Science, University of Rochester, NY (M.R.C., K.R.H.)
| | - Kate E. Watkins
- Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology (K.E.W.), University of Oxford, United Kingdom
| | - Marco Tamietto
- Department of Psychology, University of Torino, Italy (M.T.)
- Department of Medical and Clinical Psychology, and CoRPS—Center of Research on Psychology in Somatic Diseases—Tilburg University, the Netherlands (M.T.)
| | - Holly Bridge
- Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences (H.E.W., I.B.I., A.W., J.C., S.J., W.T.C., H.B.), University of Oxford, United Kingdom
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5
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Werth R. A Scientific Approach to Conscious Experience, Introspection, and Unconscious Processing: Vision and Blindsight. Brain Sci 2022; 12:1305. [PMID: 36291239 PMCID: PMC9599441 DOI: 10.3390/brainsci12101305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 09/15/2022] [Accepted: 09/25/2022] [Indexed: 11/17/2022] Open
Abstract
Although subjective conscious experience and introspection have long been considered unscientific and banned from psychology, they are indispensable in scientific practice. These terms are used in scientific contexts today; however, their meaning remains vague, and earlier objections to the distinction between conscious experience and unconscious processing, remain valid. This also applies to the distinction between conscious visual perception and unconscious visual processing. Damage to the geniculo-striate pathway or the visual cortex results in a perimetrically blind visual hemifield contralateral to the damaged hemisphere. In some cases, cerebral blindness is not absolute. Patients may still be able to guess the presence, location, shape or direction of movement of a stimulus even though they report no conscious visual experience. This "unconscious" ability was termed "blindsight". The present paper demonstrates how the term conscious visual experience can be introduced in a logically precise and methodologically correct way and becomes amenable to scientific examination. The distinction between conscious experience and unconscious processing is demonstrated in the cases of conscious vision and blindsight. The literature on "blindsight" and its neurobiological basis is reviewed. It is shown that blindsight can be caused by residual functions of neural networks of the visual cortex that have survived cerebral damage, and may also be due to an extrastriate pathway via the midbrain to cortical areas such as areas V4 and MT/V5.
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Affiliation(s)
- Reinhard Werth
- Social Pediatrics and Adolescent Medicine, Ludwig-Maximilians-University of Munich, Haydnstr. 5, D-80336 München, Germany
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6
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Wu D, Wang Y, Liu N, Wang P, Sun K, Xiao W. High-definition transcranial direct current stimulation of the left middle temporal complex does not affect visual motion perception learning. Front Neurosci 2022; 16:988590. [PMID: 36117616 PMCID: PMC9474993 DOI: 10.3389/fnins.2022.988590] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 08/15/2022] [Indexed: 11/13/2022] Open
Abstract
Visual perceptual learning (VPL) refers to the improvement in visual perceptual abilities through training and has potential implications for clinical populations. However, improvements in perceptual learning often require hundreds or thousands of trials over weeks to months to attain, limiting its practical application. Transcranial direct current stimulation (tDCS) could potentially facilitate perceptual learning, but the results are inconsistent thus far. Thus, this research investigated the effect of tDCS over the left human middle temporal complex (hMT+) on learning to discriminate visual motion direction. Twenty-seven participants were randomly assigned to the anodal, cathodal and sham tDCS groups. Before and after training, the thresholds of motion direction discrimination were assessed in one trained condition and three untrained conditions. Participants were trained over 5 consecutive days while receiving 4 × 1 ring high-definition tDCS (HD-tDCS) over the left hMT+. The results showed that the threshold of motion direction discrimination significantly decreased after training. However, no obvious differences in the indicators of perceptual learning, such as the magnitude of improvement, transfer indexes, and learning curves, were noted among the three groups. The current study did not provide evidence of a beneficial effect of tDCS on VPL. Further research should explore the impact of the learning task characteristics, number of training sessions and the sequence of stimulation.
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Affiliation(s)
- Di Wu
- Department of Medical Psychology, Air Force Medical University, Xi’an, China
| | - Yifan Wang
- Department of Medical Psychology, Air Force Medical University, Xi’an, China
| | - Na Liu
- Department of Nursing, Air Force Medical University, Xi’an, China
| | - Panhui Wang
- Department of Medical Psychology, Air Force Medical University, Xi’an, China
| | - Kewei Sun
- Department of Medical Psychology, Air Force Medical University, Xi’an, China
| | - Wei Xiao
- Department of Medical Psychology, Air Force Medical University, Xi’an, China
- *Correspondence: Wei Xiao,
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7
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Spared perilesional V1 activity underlies training-induced recovery of luminance detection sensitivity in cortically-blind patients. Nat Commun 2021; 12:6102. [PMID: 34671032 PMCID: PMC8528839 DOI: 10.1038/s41467-021-26345-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 09/29/2021] [Indexed: 11/19/2022] Open
Abstract
Damage to the primary visual cortex (V1) causes homonymous visual-field loss long considered intractable. Multiple studies now show that perceptual training can restore visual functions in chronic cortically-induced blindness (CB). A popular hypothesis is that training can harness residual visual functions by recruiting intact extrageniculostriate pathways. Training may also induce plastic changes within spared regions of the damaged V1. Here, we link changes in luminance detection sensitivity with retinotopic fMRI activity before and after visual discrimination training in eleven patients with chronic, stroke-induced CB. We show that spared V1 activity representing perimetrically-blind locations prior to training predicts the amount of training-induced recovery of luminance detection sensitivity. Additionally, training results in an enlargement of population receptive fields in perilesional V1, which increases blind-field coverage and may support further recovery with subsequent training. These findings uncover fundamental changes in perilesional V1 cortex underlying training-induced restoration of conscious luminance detection sensitivity in CB. In humans, stroke damage to V1 causes large visual field defects. Spared V1 activity prior to training predicts the amount of training-induced recovery in luminance detection sensitivity. Moreover, visual training changes population receptive field properties within residual V1 circuits.
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8
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Hagan MA, Chaplin TA, Huxlin KR, Rosa MGP, Lui LL. Altered Sensitivity to Motion of Area MT Neurons Following Long-Term V1 Lesions. Cereb Cortex 2021; 30:451-464. [PMID: 31211357 DOI: 10.1093/cercor/bhz096] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 04/16/2019] [Accepted: 04/16/2019] [Indexed: 02/04/2023] Open
Abstract
Primates with primary visual cortex (V1) damage often retain residual motion sensitivity, which is hypothesized to be mediated by middle temporal area (MT). MT neurons continue to respond to stimuli shortly after V1 lesions; however, experimental and clinical studies of lesion-induced plasticity have shown that lesion effects can take several months to stabilize. It is unknown what physiological changes occur in MT and whether neural responses persist long after V1 damage. We recorded neuronal responses in MT to moving dot patterns in adult marmoset monkeys 6-12 months after unilateral V1 lesions. In contrast to results obtained shortly after V1 lesions, we found that fewer MT neurons were direction selective, including neurons expected to still receive projections from remaining parts of V1. The firing rates of most cells increased with increases in motion strength, regardless of stimulus direction. Furthermore, firing rates were higher and more variable than in control MT cells. To test whether these observations could be mechanistically explained by underlying changes in neural circuitry, we created a network model of MT. We found that a local imbalance of inhibition and excitation explained the observed firing rate changes. These results provide the first insights into functional implications of long-term plasticity in MT following V1 lesions.
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Affiliation(s)
- Maureen A Hagan
- Department of Physiology, Monash University, Clayton, VIC 3800, Australia.,Neuroscience Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia.,Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Clayton, VIC 3800, Australia
| | - Tristan A Chaplin
- Department of Physiology, Monash University, Clayton, VIC 3800, Australia.,Neuroscience Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia.,Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Clayton, VIC 3800, Australia.,Sainsbury Wellcome Centre for Neural Circuits and Behaviour, University College London, 25 Howland Street, London W1T 4JG, United Kingdom
| | - Krystel R Huxlin
- Flaum Eye Institute, University of Rochester, Rochester, NY 14642, USA
| | - Marcello G P Rosa
- Department of Physiology, Monash University, Clayton, VIC 3800, Australia.,Neuroscience Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia.,Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Clayton, VIC 3800, Australia
| | - Leo L Lui
- Department of Physiology, Monash University, Clayton, VIC 3800, Australia.,Neuroscience Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia.,Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Clayton, VIC 3800, Australia
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9
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Is the primary visual cortex necessary for blindsight-like behavior? Review of transcranial magnetic stimulation studies in neurologically healthy individuals. Neurosci Biobehav Rev 2021; 127:353-364. [PMID: 33965459 DOI: 10.1016/j.neubiorev.2021.04.038] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 04/28/2021] [Accepted: 04/29/2021] [Indexed: 12/20/2022]
Abstract
The visual pathways that bypass the primary visual cortex (V1) are often assumed to support visually guided behavior in humans in the absence of conscious vision. This conclusion is largely based on findings on patients: V1 lesions cause blindness but sometimes leave some visually guided behaviors intact-this is known as blindsight. With the aim of examining how well the findings on blindsight patients generalize to neurologically healthy individuals, we review studies which have tried to uncover transcranial magnetic stimulation (TMS) induced blindsight. In general, these studies have failed to demonstrate a completely unconscious blindsight-like capacity in neurologically healthy individuals. A possible exception to this is TMS-induced blindsight of stimulus presence or location. Because blindsight in patients is often associated with some form of introspective access to the visual stimulus, and blindsight may be associated with neural reorganization, we suggest that rather than revealing a dissociation between visually guided behavior and conscious seeing, blindsight may reflect preservation or partial recovery of conscious visual perception after the lesion.
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10
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Pedersini CA, Lingnau A, Cardobi N, Sanchez-Lopez J, Savazzi S, Marzi CA. Neural bases of visual processing of moving and stationary stimuli presented to the blind hemifield of hemianopic patients. Neuropsychologia 2020; 141:107430. [PMID: 32173624 DOI: 10.1016/j.neuropsychologia.2020.107430] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 02/28/2020] [Accepted: 03/03/2020] [Indexed: 12/12/2022]
Abstract
Unilateral damage to post-chiasmatic visual pathways or cortical areas results in the loss of vision in the contralateral hemifield, known as hemianopia. Some patients, however, may retain the ability to perform an above chance unconscious detection or discrimination of visual stimuli presented to the blind hemifield, known as "blindsight". An important finding in blindsight research is that it can often be elicited by moving stimuli. Therefore, in the present study, we wanted to test whether moving stimuli might yield blindsight phenomena in patients with cortical lesions resulting in hemianopia, in a discrimination task where stimulus movement is orthogonal to the feature of interest. This could represent an important strategy for rehabilitation because it might improve discrimination ability of stimulus features different but related to movement, e.g. line orientation. We tested eight hemianopic patients and eight age-matched healthy controls in an orientation discrimination task with moving or static visual stimuli. During performance of the task we carried out fMRI scanning and tractography. Behaviourally, we did not find a reliable main effect of motion on orientation discrimination; however, an important result was that in different patients blindsight could occur only with moving or stationary stimuli or with both. As to brain imaging results, following presentation of moving stimuli to the blind hemifield, a widespread fronto-parietal bilateral network was recruited including areas of the dorsal stream and in particular bilateral motion area hMT + whose activation positively correlated with behavioural performance. This bilateral network was not activated in controls suggesting that it represents a compensatory functional change following brain damage. Moreover, there was a higher activation of ipsilesional area hMT+ in patients who performed above chance in the moving condition. By contrast, in patients who performed above chance in the static condition, we found a higher activation of contralesional area V1 and extrastriate visual areas. Finally, we found a linear relationship between structural integrity of the ipsilesional pathway connecting lateral geniculate nucleus (LGN) with motion area hMT+ and both behavioural performance and ipsilesional hMT + activation. These results support the role of LGN in modulating performance as well as BOLD amplitude in the absence of visual awareness in ipsilesional area hMT+ during an orientation discrimination task with moving stimuli.
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Affiliation(s)
- Caterina A Pedersini
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
| | - Angelika Lingnau
- Faculty of Psychology, Education and Sport Science, Institute of Psychology, University of Regensburg, Germany; Centre for Mind/Brain Sciences (CIMeC), University of Trento, Trento, Italy
| | - Nicolò Cardobi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Javier Sanchez-Lopez
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Silvia Savazzi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; Perception and Awareness (PandA) Laboratory, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy
| | - Carlo A Marzi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy
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11
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Fox DM, Goodale MA, Bourne JA. The Age-Dependent Neural Substrates of Blindsight. Trends Neurosci 2020; 43:242-252. [PMID: 32209455 DOI: 10.1016/j.tins.2020.01.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 01/22/2020] [Accepted: 01/23/2020] [Indexed: 12/15/2022]
Abstract
Some patients who are considered cortically blind due to the loss of their primary visual cortex (V1) show a remarkable ability to act upon or discriminate between visual stimuli presented to their blind field, without any awareness of those stimuli. This phenomenon is often referred to as blindsight. Despite the range of spared visual abilities, the identification of the pathways mediating blindsight remains an active and contentious topic in the field. In this review, we discuss recent findings of the candidate pathways and their relative contributions to different forms of blindsight across the lifespan to illustrate the varied nature of unconscious visual processing.
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Affiliation(s)
- Dylan M Fox
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Melvyn A Goodale
- The Brain and Mind Institute, The University of Western Ontario, Western Interdisciplinary Research Building, London, Ontario, Canada
| | - James A Bourne
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia.
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12
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Thorudottir S, Sigurdardottir HM, Rice GE, Kerry SJ, Robotham RJ, Leff AP, Starrfelt R. The Architect Who Lost the Ability to Imagine: The Cerebral Basis of Visual Imagery. Brain Sci 2020; 10:E59. [PMID: 31972965 PMCID: PMC7071355 DOI: 10.3390/brainsci10020059] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 01/17/2020] [Accepted: 01/19/2020] [Indexed: 11/17/2022] Open
Abstract
While the loss of mental imagery following brain lesions was first described more than a century ago, the key cerebral areas involved remain elusive. Here we report neuropsychological data from an architect (PL518) who lost his ability for visual imagery following a bilateral posterior cerebral artery (PCA) stroke. We compare his profile to three other patients with bilateral PCA stroke and another architect with a large PCA lesion confined to the right hemisphere. We also compare structural images of their lesions, aiming to delineate cerebral areas selectively lesioned in acquired aphantasia. When comparing the neuropsychological profile and structural magnetic resonance imaging (MRI) for the aphantasic architect PL518 to patients with either a comparable background (an architect) or bilateral PCA lesions, we find: (1) there is a large overlap of cognitive deficits between patients, with the very notable exception of aphantasia which only occurs in PL518, and (2) there is large overlap of the patients' lesions. The only areas of selective lesion in PL518 is a small patch in the left fusiform gyrus as well as part of the right lingual gyrus. We suggest that these areas, and perhaps in particular the region in the left fusiform gyrus, play an important role in the cerebral network involved in visual imagery.
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Affiliation(s)
- Sandra Thorudottir
- Icelandic Vision Lab, Department of Psychology, University of Iceland, 102 Reykjavik, Iceland; (S.T.); (H.M.S.)
| | - Heida M. Sigurdardottir
- Icelandic Vision Lab, Department of Psychology, University of Iceland, 102 Reykjavik, Iceland; (S.T.); (H.M.S.)
| | - Grace E. Rice
- Cognition and Brain Sciences Unit, University of Cambridge, Cambridge CB27EF, UK;
| | - Sheila J. Kerry
- Institute of Cognitive Neuroscience, University College London, London WC1N3AZ, UK; (S.J.K.); (A.P.L.)
| | - Ro J. Robotham
- Department of Psychology, University of Copenhagen, 1726 Copenhagen, Denmark;
| | - Alex P. Leff
- Institute of Cognitive Neuroscience, University College London, London WC1N3AZ, UK; (S.J.K.); (A.P.L.)
| | - Randi Starrfelt
- Department of Psychology, University of Copenhagen, 1726 Copenhagen, Denmark;
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13
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Pedersini CA, Guàrdia-Olmos J, Montalà-Flaquer M, Cardobi N, Sanchez-Lopez J, Parisi G, Savazzi S, Marzi CA. Functional interactions in patients with hemianopia: A graph theory-based connectivity study of resting fMRI signal. PLoS One 2020; 15:e0226816. [PMID: 31905211 PMCID: PMC6944357 DOI: 10.1371/journal.pone.0226816] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 12/05/2019] [Indexed: 12/12/2022] Open
Abstract
The assessment of task-independent functional connectivity (FC) after a lesion causing hemianopia remains an uncovered topic and represents a crucial point to better understand the neural basis of blindsight (i.e. unconscious visually triggered behavior) and visual awareness. In this light, we evaluated functional connectivity (FC) in 10 hemianopic patients and 10 healthy controls in a resting state paradigm. The main aim of this study is twofold: first of all we focused on the description and assessment of density and intensity of functional connectivity and network topology with and without a lesion affecting the visual pathway, and then we extracted and statistically compared network metrics, focusing on functional segregation, integration and specialization. Moreover, a study of 3-cycle triangles with prominent connectivity was conducted to analyze functional segregation calculated as the area of each triangle created connecting three neighboring nodes. To achieve these purposes we applied a graph theory-based approach, starting from Pearson correlation coefficients extracted from pairs of regions of interest. In these analyses we focused on the FC extracted by the whole brain as well as by four resting state networks: The Visual (VN), Salience (SN), Attention (AN) and Default Mode Network (DMN), to assess brain functional reorganization following the injury. The results showed a general decrease in density and intensity of functional connections, that leads to a less compact structure characterized by decrease in functional integration, segregation and in the number of interconnected hubs in both the Visual Network and the whole brain, despite an increase in long-range inter-modules connections (occipito-frontal connections). Indeed, the VN was the most affected network, characterized by a decrease in intra- and inter-network connections and by a less compact topology, with less interconnected nodes. Surprisingly, we observed a higher functional integration in the DMN and in the AN regardless of the lesion extent, that may indicate a functional reorganization of the brain following the injury, trying to compensate for the general reduced connectivity. Finally we observed an increase in functional specialization (lower between-network connectivity) and in inter-networks functional segregation, which is reflected in a less compact network topology, highly organized in functional clusters. These descriptive findings provide new insight on the spontaneous brain activity in hemianopic patients by showing an alteration in the intrinsic architecture of a large-scale brain system that goes beyond the impairment of a single RSN.
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Affiliation(s)
- Caterina A. Pedersini
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Joan Guàrdia-Olmos
- Department of Social Psychology and Quantitative Psychology, School of Psychology, Institute of Neuroscience, Institute of Complex Systems, University of Barcelona, Barcelona, Spain
| | - Marc Montalà-Flaquer
- Department of Social Psychology and Quantitative Psychology, School of Psychology, Institute of Complex Systems, University of Barcelona, Barcelona, Spain
| | - Nicolò Cardobi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Javier Sanchez-Lopez
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Giorgia Parisi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Silvia Savazzi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
- Perception and Awareness (PandA) Laboratory, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
- National Institute of Neuroscience, Verona, Italy
| | - Carlo A. Marzi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
- National Institute of Neuroscience, Verona, Italy
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14
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Prasad S, Dinkin M. Higher Cortical Visual Disorders. Continuum (Minneap Minn) 2019; 25:1329-1361. [PMID: 31584540 DOI: 10.1212/con.0000000000000774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE OF REVIEW This article reviews the disorders that result from disruption of extrastriate regions of the cerebral cortex responsible for higher visual processing. For each disorder, a historical perspective is offered and relevant neuroscientific studies are reviewed. RECENT FINDINGS Careful analysis of the consequences of lesions that disrupt visual functions such as facial recognition and written language processing has improved understanding of the role of key regions in these networks. In addition, modern imaging techniques have built upon prior lesion studies to further elucidate the functions of these cortical areas. For example, functional MRI (fMRI) has identified and characterized the response properties of ventral regions that contribute to object recognition and dorsal regions that subserve motion perception and visuospatial attention. Newer network-based functional imaging studies have shed light on the mechanisms behind various causes of spontaneous visual hallucinations. SUMMARY Understanding the regions and neural networks responsible for higher-order visual function helps the practicing neurologist to diagnose and manage associated disorders of visual processing and to identify and treat responsible underlying disease.
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15
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Bridge H, Bell AH, Ainsworth M, Sallet J, Premereur E, Ahmed B, Mitchell AS, Schüffelgen U, Buckley M, Tendler BC, Miller KL, Mars RB, Parker AJ, Krug K. Preserved extrastriate visual network in a monkey with substantial, naturally occurring damage to primary visual cortex. eLife 2019; 8:e42325. [PMID: 31120417 PMCID: PMC6533062 DOI: 10.7554/elife.42325] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 04/27/2019] [Indexed: 12/13/2022] Open
Abstract
Lesions of primary visual cortex (V1) lead to loss of conscious visual perception with significant impact on human patients. Understanding the neural consequences of such damage may aid the development of rehabilitation methods. In this rare case of a Rhesus macaque (monkey S), likely born without V1, the animal's in-group behaviour was unremarkable, but visual task training was impaired. With multi-modal magnetic resonance imaging, visual structures outside of the lesion appeared normal. Visual stimulation under anaesthesia with checkerboards activated lateral geniculate nucleus of monkey S, while full-field moving dots activated pulvinar. Visual cortical activation was sparse but included face patches. Consistently across lesion and control monkeys, functional connectivity analysis revealed an intact network of bilateral dorsal visual areas temporally correlated with V5/MT activation, even without V1. Despite robust subcortical responses to visual stimulation, we found little evidence for strengthened subcortical input to V5/MT supporting residual visual function or blindsight-like phenomena.
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Affiliation(s)
- Holly Bridge
- Wellcome Centre for Integrative Neuroimaging, FMRIBOxford UniversityOxfordUnited Kingdom
- Nuffield Department of Clinical NeurosciencesOxford UniversityOxfordUnited Kingdom
| | - Andrew H Bell
- Wellcome Centre for Integrative Neuroimaging, FMRIBOxford UniversityOxfordUnited Kingdom
- Department of Experimental PsychologyOxford UniversityOxfordUnited Kingdom
- MRC Cognition and Brain Sciences UnitCambridgeUnited Kingdom
| | - Matthew Ainsworth
- Department of Experimental PsychologyOxford UniversityOxfordUnited Kingdom
- MRC Cognition and Brain Sciences UnitCambridgeUnited Kingdom
| | - Jerome Sallet
- Wellcome Centre for Integrative Neuroimaging, FMRIBOxford UniversityOxfordUnited Kingdom
- Department of Experimental PsychologyOxford UniversityOxfordUnited Kingdom
| | - Elsie Premereur
- Laboratory for Neuro- and PsychophysiologyKU LeuvenLeuvenBelgium
| | - Bashir Ahmed
- Department of Physiology, Anatomy and GeneticsOxford UniversityOxfordUnited Kingdom
| | - Anna S Mitchell
- Department of Experimental PsychologyOxford UniversityOxfordUnited Kingdom
| | - Urs Schüffelgen
- Wellcome Centre for Integrative Neuroimaging, FMRIBOxford UniversityOxfordUnited Kingdom
- Department of Experimental PsychologyOxford UniversityOxfordUnited Kingdom
| | - Mark Buckley
- Department of Experimental PsychologyOxford UniversityOxfordUnited Kingdom
| | - Benjamin C Tendler
- Wellcome Centre for Integrative Neuroimaging, FMRIBOxford UniversityOxfordUnited Kingdom
- Nuffield Department of Clinical NeurosciencesOxford UniversityOxfordUnited Kingdom
| | - Karla L Miller
- Wellcome Centre for Integrative Neuroimaging, FMRIBOxford UniversityOxfordUnited Kingdom
- Nuffield Department of Clinical NeurosciencesOxford UniversityOxfordUnited Kingdom
| | - Rogier B Mars
- Wellcome Centre for Integrative Neuroimaging, FMRIBOxford UniversityOxfordUnited Kingdom
- Nuffield Department of Clinical NeurosciencesOxford UniversityOxfordUnited Kingdom
- Donders Institute for Brain, Cognition and BehaviourRadboud University NijmegenNijmegenNetherlands
| | - Andrew J Parker
- Department of Physiology, Anatomy and GeneticsOxford UniversityOxfordUnited Kingdom
| | - Kristine Krug
- Department of Physiology, Anatomy and GeneticsOxford UniversityOxfordUnited Kingdom
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16
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Sanchez-Lopez J, Pedersini CA, Di Russo F, Cardobi N, Fonte C, Varalta V, Prior M, Smania N, Savazzi S, Marzi CA. Visually evoked responses from the blind field of hemianopic patients. Neuropsychologia 2019; 128:127-139. [PMID: 28987906 PMCID: PMC5845440 DOI: 10.1016/j.neuropsychologia.2017.10.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 10/02/2017] [Accepted: 10/03/2017] [Indexed: 11/28/2022]
Abstract
Hemianopia is a visual field defect characterized by decreased vision or blindness in the contralesional visual field of both eyes. The presence of well documented above-chance unconscious behavioural responses to visual stimuli presented to the blind hemifield (blindsight) has stimulated a great deal of research on the neural basis of this important phenomenon. The present study is concerned with electrophysiological responses from the blind field. Since previous studies found that transient Visual Evoked Potentials (VEPs) are not entirely suitable for this purpose here we propose to use Steady-State VEPs (SSVEPs). A positive result would have important implications for the understanding of the neural bases of conscious vision. We carried out a passive SSVEP stimulation with healthy participants and hemianopic patients. Stimuli consisted of four black-and-white sinusoidal Gabor gratings presented one in each visual field quadrant and flickering one at a time at a 12Hz rate. To assess response reliability a Signal-to-Noise Ratio analysis was conducted together with further analyses in time and frequency domains to make comparisons between groups (healthy participants and patients), side of brain lesion (left and right) and visual fields (sighted and blind). The important overall result was that stimulus presentation to the blind hemifield yielded highly reliable responses with time and frequency features broadly similar to those found for cortical extrastriate areas in healthy controls. Moreover, in the intact hemifield of hemianopics and in healthy controls there was evidence of a role of prefrontal structures in perceptual awareness. Finally, the presence of different patterns of brain reorganization depended upon the side of lesion.
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Affiliation(s)
- Javier Sanchez-Lopez
- Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy.
| | - Caterina A Pedersini
- Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy
| | - Francesco Di Russo
- Department. of Movement, Human and Health Sciences, University of Rome "Foro Italico", Rome, Italy; IRCCS Santa Lucia Foundation, Rome, Italy
| | - Nicolò Cardobi
- Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy
| | - Cristina Fonte
- Neuromotor and Cognitive Rehabilitation Research Center, Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy
| | - Valentina Varalta
- Neuromotor and Cognitive Rehabilitation Research Center, Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy
| | | | - Nicola Smania
- Neuromotor and Cognitive Rehabilitation Research Center, Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy
| | - Silvia Savazzi
- Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy; Perception and Awareness (PandA) Laboratory, Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy; National Institute of Neuroscience, Verona, Italy
| | - Carlo A Marzi
- Department of Neuroscience, Biomedicine and Movement, University of Verona, Italy; National Institute of Neuroscience, Verona, Italy
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17
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More than blindsight: Case report of a child with extraordinary visual capacity following perinatal bilateral occipital lobe injury. Neuropsychologia 2019; 128:178-186. [DOI: 10.1016/j.neuropsychologia.2017.11.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 09/26/2017] [Accepted: 11/12/2017] [Indexed: 11/18/2022]
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18
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Bienkowski MS, Benavidez NL, Wu K, Gou L, Becerra M, Dong HW. Extrastriate connectivity of the mouse dorsal lateral geniculate thalamic nucleus. J Comp Neurol 2019; 527:1419-1442. [PMID: 30620046 DOI: 10.1002/cne.24627] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 11/14/2018] [Accepted: 12/10/2018] [Indexed: 12/12/2022]
Abstract
The mammalian visual system is one of the most well-studied brain systems. Visual information from the retina is relayed to the dorsal lateral geniculate nucleus of the thalamus (LGd). The LGd then projects topographically to primary visual cortex (VISp) to mediate visual perception. In this view, the VISp is a critical network hub where visual information must traverse LGd-VISp circuits to reach higher order "extrastriate" visual cortices, which surround the VISp on its medial and lateral borders. However, decades of conflicting reports in a variety of mammals support or refute the existence of extrastriate LGd connections that can bypass the VISp. Here, we provide evidence of bidirectional extrastriate connectivity with the mouse LGd. Using small, discrete coinjections of anterograde and retrograde tracers within the thalamus and cortex, our cross-validated approach identified bidirectional connectivity between LGd and extrastriate visual cortices. We find robust reciprocal connectivity of the medial extrastriate regions with LGd neurons distributed along the "ventral strip" border with the intergeniculate leaflet. In contrast, LGd input to lateral extrastriate regions is sparse, but lateral extrastriate regions return stronger descending projections to localized LGd areas. We show further evidence that axons from lateral extrastriate regions can overlap onto medial extrastriate-projecting LGd neurons in the ventral strip, providing a putative subcortical LGd pathway for communication between medial and lateral extrastriate regions. Overall, our findings support the existence of extrastriate LGd circuits and provide novel understanding of LGd organization in rodent visual system.
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Affiliation(s)
- Michael S Bienkowski
- USC Stevens Neuroimaging and Informatics Institute, Center for Integrative Connectomics, Keck School of Medicine of University of Southern California, Los Angeles, California
| | - Nora L Benavidez
- USC Stevens Neuroimaging and Informatics Institute, Center for Integrative Connectomics, Keck School of Medicine of University of Southern California, Los Angeles, California
| | - Kevin Wu
- USC Stevens Neuroimaging and Informatics Institute, Center for Integrative Connectomics, Keck School of Medicine of University of Southern California, Los Angeles, California
| | - Lin Gou
- USC Stevens Neuroimaging and Informatics Institute, Center for Integrative Connectomics, Keck School of Medicine of University of Southern California, Los Angeles, California
| | - Marlene Becerra
- USC Stevens Neuroimaging and Informatics Institute, Center for Integrative Connectomics, Keck School of Medicine of University of Southern California, Los Angeles, California
| | - Hong-Wei Dong
- USC Stevens Neuroimaging and Informatics Institute, Center for Integrative Connectomics, Keck School of Medicine of University of Southern California, Los Angeles, California
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19
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Larcombe SJ, Kennard C, O'Shea J, Bridge H. No Effect of Anodal Transcranial Direct Current Stimulation (tDCS) Over hMT+ on Motion Perception Learning. Front Neurosci 2019; 12:1044. [PMID: 30705617 PMCID: PMC6344419 DOI: 10.3389/fnins.2018.01044] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 12/24/2018] [Indexed: 11/23/2022] Open
Abstract
Background: Human visual cortical area hMT+, like its homolog MT in the macaque monkey, has been shown to be particularly selective to visual motion. After damage to the primary visual cortex (V1), patients often exhibit preserved ability to detect moving stimuli, which is associated with neural activity in area hMT+. As an anatomical substrate that underlies residual function in the absence of V1, promoting functional plasticity within hMT+ could potentially boost visual performance despite primary visual cortical damage. Objective: To establish in healthy participants whether it is possible to use transcranial direct current stimulation (tDCS) over hMT+ to potentiate learning of visual motion direction discrimination. Methods: Twenty-one participants were trained daily for 5 days on a visual motion direction discrimination task. Task difficulty was increased as performance improved, by decreasing the proportion of coherently moving dots, such that participants were always performing at psychophysical threshold. tDCS, either anodal or sham, was applied daily during 20 min of training. Task performance was assessed at baseline and at the end of the training period. Performance was also compared with a third group of 10 participants from an earlier study who had undergone the same procedures but without tDCS. Results: All participants showed improved task performance both during and after training. Contrary to our hypothesis, anodal tDCS did not further improve performance compared to sham stimulation or no stimulation. Bayesian statistics indicated weak evidence in favor of the null hypothesis. Conclusion: This study found no evidence for a robust effect of anodal tDCS over hMT+ on visual motion direction discrimination learning in the young healthy visual system, although more subtle effects may have been missed in the relatively small sample size.
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Affiliation(s)
- Stephanie J Larcombe
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Christopher Kennard
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Jacinta O'Shea
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Wellcome Centre for Integrative Neuroimaging - Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Holly Bridge
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Wellcome Centre for Integrative Neuroimaging - Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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20
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Stereoscopic visual area connectivity: a diffusion tensor imaging study. Surg Radiol Anat 2018; 40:1197-1208. [PMID: 30088052 DOI: 10.1007/s00276-018-2076-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 07/23/2018] [Indexed: 10/28/2022]
Abstract
PURPOSE To study the white matter tracts connecting the different stereoscopic visual areas of the brain by diffusion tensor imaging. METHODS In a previous study, we identified the cortical activations to a visual 3D stimulation in 12 subjects using functional MRI (fMRI). These areas of cortical activations [V5, V6, lateral occipital complex (LOC) and intra parietal sulcus areas (IPS)] in addition to the lateral geniculate nucleus (LGN) and the primary visual area V1 were chosen as regions of interest (ROIs). We studied by deterministic tractography the connections existing between these ROIs. RESULTS Found connections were divided into three groups. The first group entails the geniculo-extrastriate connections. LGN was connected to V5, V6, IPS and LOC. These fibers course in the inferior longitudinal fascicule. The second group comprises the associative fibers. V1 was connected to V5 and LOC through the transverse occipital fascicule on one hand, and, to V6 and IPS through the stratum proprium cuni on the other hand. Connections between V5 and LOC, and V6 and IPS course within the vertical occipital fascicule. The third group contains commissural fibers. Forceps major entailed the connections between both V1, both V6, both IPS and IPS and contralateral V6. LGN was connected to contralateral LGN, V1, V6, IPS and LOC. CONCLUSIONS We have elucidated numerous connections between the visual areas and the LGN. Generalization of these results to the remainder of the population must remain prudent due to the limited number of subjects in this study.
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21
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Ajina S, Bridge H. Blindsight relies on a functional connection between hMT+ and the lateral geniculate nucleus, not the pulvinar. PLoS Biol 2018; 16:e2005769. [PMID: 30044775 PMCID: PMC6078309 DOI: 10.1371/journal.pbio.2005769] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 08/06/2018] [Accepted: 07/09/2018] [Indexed: 12/23/2022] Open
Abstract
When the primary visual cortex (V1) is damaged, the principal visual pathway is lost, causing a loss of vision in the opposite visual field. While conscious vision is impaired, patients can still respond to certain images; this is known as 'blindsight'. Recently, a direct anatomical connection between the lateral geniculate nucleus (LGN) and human motion area hMT+ has been implicated in blindsight. However, a functional connection between these structures has not been demonstrated. We quantified functional MRI responses to motion in 14 patients with unilateral V1 damage (with and without blindsight). Patients with blindsight showed significant activity and a preserved sensitivity to speed in motion area hMT+, which was absent in patients without blindsight. We then compared functional connectivity between motion area hMT+ and a number of structures implicated in blindsight, including the ventral pulvinar. Only patients with blindsight showed an intact functional connection with the LGN but not the other structures, supporting a specific functional role for the LGN in blindsight.
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Affiliation(s)
- Sara Ajina
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Holly Bridge
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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22
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Organization of area hV5/MT+ in subjects with homonymous visual field defects. Neuroimage 2018; 190:254-268. [PMID: 29627591 DOI: 10.1016/j.neuroimage.2018.03.062] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Revised: 03/05/2018] [Accepted: 03/26/2018] [Indexed: 11/21/2022] Open
Abstract
Damage to the primary visual cortex (V1) leads to a visual field loss (scotoma) in the retinotopically corresponding part of the visual field. Nonetheless, a small amount of residual visual sensitivity persists within the blind field. This residual capacity has been linked to activity observed in the middle temporal area complex (V5/MT+). However, it remains unknown whether the organization of hV5/MT+ changes following early visual cortical lesions. We studied the organization of area hV5/MT+ of five patients with dense homonymous defects in a quadrant of the visual field as a result of partial V1+ or optic radiation lesions. To do so, we developed a new method, which models the boundaries of population receptive fields directly from the BOLD signal of each voxel in the visual cortex. We found responses in hV5/MT+ arising inside the scotoma for all patients and identified two possible sources of activation: 1) responses might originate from partially lesioned parts of area V1 corresponding to the scotoma, and 2) responses can also originate independent of area V1 input suggesting the existence of functional V1-bypassing pathways. Apparently, visually driven activity observed in hV5/MT+ is not sufficient to mediate conscious vision. More surprisingly, visually driven activity in corresponding regions of V1 and early extrastriate areas including hV5/MT+ did not guarantee visual perception in the group of patients with post-geniculate lesions that we examined. This suggests that the fine coordination of visual activity patterns across visual areas may be an important determinant of whether visual perception persists following visual cortical lesions.
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23
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Abstract
Much remains to be understood about visual system malfunction following injury. The resulting deficits range from dense, visual field scotomas to mild dysfunction of visual perception. Despite the predictive value of anatomical localization studies, much patient-to-patient variability remains regarding (a) perceptual abilities following injury and (b) the capacity of individual patients for visual rehabilitation. Visual field perimetry is used to characterize the visual field deficits that result from visual system injury. However, standard perimetry mapping does not always precisely correspond to underlying anatomical or functional deficits. Functional magnetic resonance imaging can be used to probe the function of surviving visual circuits, allowing us to classify better how the pattern of injury relates to residual visual perception. Identifying pathways that are potentially modifiable by training may guide the development of improved strategies for visual rehabilitation. This review discusses primary visual cortex lesions, which cause dense contralateral scotomas.
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Affiliation(s)
- Stelios M Smirnakis
- Department of Neurology, Brigham and Women's Hospital, Boston, Massachusetts 02115.,Department of Neurology, Jamaica Plain Campus, Veterans Administration Boston Healthcare System, Boston, Massachusetts 02130.,Harvard Medical School, Boston, Massachusetts 02115;
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24
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Ajina S, Bridge H. Subcortical pathways to extrastriate visual cortex underlie residual vision following bilateral damage to V1. Neuropsychologia 2018; 128:140-149. [PMID: 29320715 PMCID: PMC6562274 DOI: 10.1016/j.neuropsychologia.2018.01.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 12/18/2017] [Accepted: 01/05/2018] [Indexed: 11/29/2022]
Abstract
Residual vision, or blindsight, following damage to the primary visual cortex (V1) has been investigated for almost half a century. While there have been many studies of patients with unilateral damage to V1, far fewer have examined bilateral damage, mainly due to the rarity of such patients. Here we re-examine the residual visual function and underlying pathways of previously studied patient SBR who, as a young adult, suffered bilateral damage restricted to V1 which rendered him cortically blind. While earlier work compared his visual cortex to healthy, sighted participants, here we consider how his visual responses and connections compare to patients with unilateral damage to V1 in addition to sighted participants. Detection of drifting Gabor patches of different contrasts (1%, 5%, 10%, 50% and 100%) was tested in SBR and a group of eight patients with unilateral damage to V1. Performance was compared to the neural activation in motion area hMT+ measured using functional magnetic resonance imaging. Diffusion tractography was also used to determine the white matter microstructure of the visual pathways in all participants. Like the patients with unilateral damage, patient SBR showed increased % BOLD signal change to the high contrast stimuli that he could detect compared to the lower contrast stimuli that were not detectable. Diffusion tractography suggests this information is conveyed by a direct pathway between the lateral geniculate nucleus (LGN) and hMT+ since this pathway had microstructure that was comparable to the healthy control group. In contrast, the pathway between LGN and V1 had reduced integrity compared to controls. A further finding of note was that, unlike control participants, SBR showed similar patterns of contralateral and ipsilateral activity in hMT+, in addition to healthy white matter microstructure in the tract connecting hMT+ between the two hemispheres. This raises the possibility of increased connectivity between the two hemispheres in the absence of V1 input. In conclusion, the pattern of visual function and anatomy in bilateral cortical damage is comparable to that seen in a group of patients with unilateral damage. Thus, while the intact hemisphere may play a role in residual vision in patients with unilateral damage, its influence is not evident with the methodology employed here. Bilaterally hemianopic patient SBR has neural patterns like unilateral patients. hMT+ activity increases with stimulus contrast and better stimulus detection. Like in unilateral patients, the pathway between LGN and hMT+ is intact in SBR.
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Affiliation(s)
- Sara Ajina
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, UK
| | - Holly Bridge
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, UK.
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25
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Arrigo A, Calamuneri A, Milardi D, Mormina E, Rania L, Postorino E, Marino S, Di Lorenzo G, Anastasi GP, Ghilardi MF, Aragona P, Quartarone A, Gaeta M. Visual System Involvement in Patients with Newly Diagnosed Parkinson Disease. Radiology 2017; 285:885-895. [PMID: 28696183 DOI: 10.1148/radiol.2017161732] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Purpose To assess intracranial visual system changes of newly diagnosed Parkinson disease in drug-naïve patients. Materials and Methods Twenty patients with newly diagnosed Parkinson disease and 20 age-matched control subjects were recruited. Magnetic resonance (MR) imaging (T1-weighted and diffusion-weighted imaging) was performed with a 3-T MR imager. White matter changes were assessed by exploring a white matter diffusion profile by means of diffusion-tensor imaging-based parameters and constrained spherical deconvolution-based connectivity analysis and by means of white matter voxel-based morphometry (VBM). Alterations in occipital gray matter were investigated by means of gray matter VBM. Morphologic analysis of the optic chiasm was based on manual measurement of regions of interest. Statistical testing included analysis of variance, t tests, and permutation tests. Results In the patients with Parkinson disease, significant alterations were found in optic radiation connectivity distribution, with decreased lateral geniculate nucleus V2 density (F, -8.28; P < .05), a significant increase in optic radiation mean diffusivity (F, 7.5; P = .014), and a significant reduction in white matter concentration. VBM analysis also showed a significant reduction in visual cortical volumes (P < .05). Moreover, the chiasmatic area and volume were significantly reduced (P < .05). Conclusion The findings show that visual system alterations can be detected in early stages of Parkinson disease and that the entire intracranial visual system can be involved. © RSNA, 2017 Online supplemental material is available for this article.
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Affiliation(s)
- Alessandro Arrigo
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Alessandro Calamuneri
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Demetrio Milardi
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Enricomaria Mormina
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Laura Rania
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Elisa Postorino
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Silvia Marino
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Giuseppe Di Lorenzo
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Giuseppe Pio Anastasi
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Maria Felice Ghilardi
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Pasquale Aragona
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Angelo Quartarone
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
| | - Michele Gaeta
- From the Department of Opthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, via Olgettina 60, Milan, 20132, Italy (A.A.); Department of Biomedical Science and Morphological and Functional Images, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy (A.A., A.C., D.M., E.M., L.R., E.P., G.P.A., P.A., A.Q., M.G.); IRCCS Centro Neurolesi Bonino Pulejo, Messina, Italy (D.M., S.M., G.D.L.); and Sophie Davis School for Biomedical Education at CCNY, City University of New York, New York, NY (M.F.G.)
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26
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Rokem A, Takemura H, Bock AS, Scherf KS, Behrmann M, Wandell BA, Fine I, Bridge H, Pestilli F. The visual white matter: The application of diffusion MRI and fiber tractography to vision science. J Vis 2017; 17:4. [PMID: 28196374 PMCID: PMC5317208 DOI: 10.1167/17.2.4] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 12/12/2016] [Indexed: 12/19/2022] Open
Abstract
Visual neuroscience has traditionally focused much of its attention on understanding the response properties of single neurons or neuronal ensembles. The visual white matter and the long-range neuronal connections it supports are fundamental in establishing such neuronal response properties and visual function. This review article provides an introduction to measurements and methods to study the human visual white matter using diffusion MRI. These methods allow us to measure the microstructural and macrostructural properties of the white matter in living human individuals; they allow us to trace long-range connections between neurons in different parts of the visual system and to measure the biophysical properties of these connections. We also review a range of findings from recent studies on connections between different visual field maps, the effects of visual impairment on the white matter, and the properties underlying networks that process visual information supporting visual face recognition. Finally, we discuss a few promising directions for future studies. These include new methods for analysis of MRI data, open datasets that are becoming available to study brain connectivity and white matter properties, and open source software for the analysis of these data.
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Affiliation(s)
- Ariel Rokem
- The University of Washington eScience Institute, Seattle, WA, ://arokem.org
| | - Hiromasa Takemura
- Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, and Osaka University, Suita-shi, JapanGraduate School of Frontier Biosciences, Osaka University, Suita-shi,
| | | | | | | | | | - Ione Fine
- University of Washington, Seattle, WA,
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27
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Ruffieux N, Ramon M, Lao J, Colombo F, Stacchi L, Borruat FX, Accolla E, Annoni JM, Caldara R. Residual perception of biological motion in cortical blindness. Neuropsychologia 2016; 93:301-311. [DOI: 10.1016/j.neuropsychologia.2016.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 10/19/2016] [Accepted: 11/09/2016] [Indexed: 11/25/2022]
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28
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Ajina S, Bridge H. Blindsight and Unconscious Vision: What They Teach Us about the Human Visual System. Neuroscientist 2016; 23:529-541. [PMID: 27777337 DOI: 10.1177/1073858416673817] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Damage to the primary visual cortex removes the major input from the eyes to the brain, causing significant visual loss as patients are unable to perceive the side of the world contralateral to the damage. Some patients, however, retain the ability to detect visual information within this blind region; this is known as blindsight. By studying the visual pathways that underlie this residual vision in patients, we can uncover additional aspects of the human visual system that likely contribute to normal visual function but cannot be revealed under physiological conditions. In this review, we discuss the residual abilities and neural activity that have been described in blindsight and the implications of these findings for understanding the intact system.
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Affiliation(s)
- Sara Ajina
- 1 Oxford Centre for Functional MRI of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Holly Bridge
- 1 Oxford Centre for Functional MRI of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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29
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Hagan MA, Rosa MGP, Lui LL. Neural plasticity following lesions of the primate occipital lobe: The marmoset as an animal model for studies of blindsight. Dev Neurobiol 2016; 77:314-327. [PMID: 27479288 DOI: 10.1002/dneu.22426] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/21/2016] [Accepted: 07/29/2016] [Indexed: 12/15/2022]
Abstract
For nearly a century it has been observed that some residual visually guided behavior can persist after damage to the primary visual cortex (V1) in primates. The age at which damage to V1 occurs leads to different outcomes, with V1 lesions in infancy allowing better preservation of visual faculties in comparison with those incurred in adulthood. While adult V1 lesions may still allow retention of some limited visual abilities, these are subconscious-a characteristic that has led to this form of residual vision being referred to as blindsight. The neural basis of blindsight has been of great interest to the neuroscience community, with particular focus on understanding the contributions of the different subcortical pathways and cortical areas that may underlie this phenomenon. More recently, research has started to address which forms of neural plasticity occur following V1 lesions at different ages, including work using marmoset monkeys. The relatively rapid postnatal development of this species, allied to the lissencephalic brains and well-characterized visual cortex provide significant technical advantages, which allow controlled experiments exploring visual function in the absence of V1. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 314-327, 2017.
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Affiliation(s)
- Maureen A Hagan
- Department of Physiology, Monash University, Victoria, 3800, Australia.,Neuroscience Program, Biomedicine Discovery Institute, Monash University, Victoria, 3800, Australia.,Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Victoria, 3800, Australia
| | - Marcello G P Rosa
- Department of Physiology, Monash University, Victoria, 3800, Australia.,Neuroscience Program, Biomedicine Discovery Institute, Monash University, Victoria, 3800, Australia.,Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Victoria, 3800, Australia
| | - Leo L Lui
- Department of Physiology, Monash University, Victoria, 3800, Australia.,Neuroscience Program, Biomedicine Discovery Institute, Monash University, Victoria, 3800, Australia.,Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Victoria, 3800, Australia
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30
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Gilaie-Dotan S. Visual motion serves but is not under the purview of the dorsal pathway. Neuropsychologia 2016; 89:378-392. [PMID: 27444880 DOI: 10.1016/j.neuropsychologia.2016.07.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 06/14/2016] [Accepted: 07/17/2016] [Indexed: 10/21/2022]
Abstract
Visual motion processing is often attributed to the dorsal visual pathway despite visual motion's involvement in almost all visual functions. Furthermore, some visual motion tasks critically depend on the structural integrity of regions outside the dorsal pathway. Here, based on numerous studies, I propose that visual motion signals are swiftly transmitted via multiple non-hierarchical routes to primary motion-dedicated processing regions (MT/V5 and MST) that are not part of the dorsal pathway, and then propagated to a multiplicity of brain areas according to task demands, reaching these regions earlier than the dorsal/ventral hierarchical flow. This not only places MT/V5 at the same or even earlier visual processing stage as that of V1, but can also elucidate many findings with implications to visual awareness. While the integrity of the non-hierarchical motion pathway is necessary for all visual motion perception, it is insufficient on its own, and the transfer of visual motion signals to additional brain areas is crucial to allow the different motion perception tasks (e.g. optic flow, visuo-vestibular balance, movement observation, dynamic form detection and perception, and even reading). I argue that this lateral visual motion pathway can be distinguished from the dorsal pathway not only based on faster response latencies and distinct anatomical connections, but also based on its full field representation. I also distinguish between this primary lateral visual motion pathway sensitive to all motion in the visual field, and a much less investigated optic flow sensitive medial processing pathway (from V1 to V6 and V6A) that appears to be part of the dorsal pathway. Multiple additional predictions are provided that allow testing this proposal and distinguishing between the visual pathways.
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Affiliation(s)
- Sharon Gilaie-Dotan
- UCL Institute of Cognitive Neuroscience, London WC1N 3AR, UK; Visual Science and Optometry, Bar Ilan University, Ramat Gan, Israel.
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31
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de Gelder B, Tamietto M, Pegna AJ, Van den Stock J. Visual imagery influences brain responses to visual stimulation in bilateral cortical blindness. Cortex 2015; 72:15-26. [DOI: 10.1016/j.cortex.2014.11.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 08/29/2014] [Accepted: 11/18/2014] [Indexed: 11/29/2022]
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32
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Hervais-Adelman A, Legrand LB, Zhan M, Tamietto M, de Gelder B, Pegna AJ. Looming sensitive cortical regions without V1 input: evidence from a patient with bilateral cortical blindness. Front Integr Neurosci 2015; 9:51. [PMID: 26557059 PMCID: PMC4614319 DOI: 10.3389/fnint.2015.00051] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 09/25/2015] [Indexed: 11/26/2022] Open
Abstract
Fast and automatic behavioral responses are required to avoid collision with an approaching stimulus. Accordingly, looming stimuli have been found to be highly salient and efficient attractors of attention due to the implication of potential collision and potential threat. Here, we address the question of whether looming motion is processed in the absence of any functional primary visual cortex and consequently without awareness. For this, we investigated a patient (TN) suffering from complete, bilateral damage to his primary visual cortex. Using an fMRI paradigm, we measured TN's brain activation during the presentation of looming, receding, rotating, and static point lights, of which he was unaware. When contrasted with other conditions, looming was found to produce bilateral activation of the middle temporal areas, as well as the superior temporal sulcus and inferior parietal lobe (IPL). The latter are generally thought to be involved in multisensory processing of motion in extrapersonal space, as well as attentional capture and saliency. No activity was found close to the lesioned V1 area. This demonstrates that looming motion is processed in the absence of awareness through direct subcortical projections to areas involved in multisensory processing of motion and saliency that bypass V1.
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Affiliation(s)
- Alexis Hervais-Adelman
- Laboratory of Experimental Neuropsychology, Neurology Clinic, Department of Clinical Neuroscience, University of Geneva Geneva, Switzerland ; Brain and Language Lab, Department of Clinical Neuroscience, University of Geneva Geneva, Switzerland
| | - Lore B Legrand
- Laboratory of Experimental Neuropsychology, Neurology Clinic, Department of Clinical Neuroscience, University of Geneva Geneva, Switzerland ; Faculty of Psychology and Educational Sciences, University of Geneva Geneva, Switzerland
| | - Minye Zhan
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands
| | - Marco Tamietto
- Department of Psychology, University of Torino Torino, Italy ; Cognitive and Affective Neuroscience Laboratory, Center of Research on Psychology in Somatic Diseases, Tilburg University Tilburg, Netherlands ; Department of Experimental Psychology, University of Oxford Oxford, UK
| | - Beatrice de Gelder
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands
| | - Alan J Pegna
- Laboratory of Experimental Neuropsychology, Neurology Clinic, Department of Clinical Neuroscience, University of Geneva Geneva, Switzerland ; Faculty of Psychology and Educational Sciences, University of Geneva Geneva, Switzerland ; School of Psychology, University of Queensland Brisbane, QLD, Australia
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Ajina S, Pestilli F, Rokem A, Kennard C, Bridge H. Human blindsight is mediated by an intact geniculo-extrastriate pathway. eLife 2015; 4. [PMID: 26485034 PMCID: PMC4641435 DOI: 10.7554/elife.08935] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 10/20/2015] [Indexed: 11/30/2022] Open
Abstract
Although damage to the primary visual cortex (V1) causes hemianopia, many patients retain some residual vision; known as blindsight. We show that blindsight may be facilitated by an intact white-matter pathway between the lateral geniculate nucleus and motion area hMT+. Visual psychophysics, diffusion-weighted magnetic resonance imaging and fibre tractography were applied in 17 patients with V1 damage acquired during adulthood and 9 age-matched controls. Individuals with V1 damage were subdivided into blindsight positive (preserved residual vision) and negative (no residual vision) according to psychophysical performance. All blindsight positive individuals showed intact geniculo-hMT+ pathways, while this pathway was significantly impaired or not measurable in blindsight negative individuals. Two white matter pathways previously implicated in blindsight: (i) superior colliculus to hMT+ and (ii) between hMT+ in each hemisphere were not consistently present in blindsight positive cases. Understanding the visual pathways crucial for residual vision may direct future rehabilitation strategies for hemianopia patients. DOI:http://dx.doi.org/10.7554/eLife.08935.001 Visual information from our eyes projects to a region at the back of the brain called the primary visual cortex, which is where the information is processed to allow us to see the world around us. If a person suffers a stroke that affects this primary visual cortex, he or she can become blind on one side. However, some people can still detect images within this ‘blind’ area, even if they are not consciously aware of it. This phenomenon is known as ‘blindsight’, but it remains unclear which pathways and structures in the brain might allow this information to be detected. Ajina et al. have now examined the brains of a large group of patients with damage to the visual cortex. The results for the patients with blindsight were compared to those without, and to a group of sighted control participants. This analysis identified a pathway that seems to underlie blindsight. This pathway (which runs between an area of the brain called the lateral geniculate nucleus and another called the motion area hMT+) was present in all patients with blindsight, but was missing or disrupted in those patients without blindsight. Ajina et al. then examined other pathways that had previously been suggested to support blindsight and revealed that they were unlikely to do so. This is because the suggested connections were not identifiable in all patients with blindsight, and were often intact in those patients without blindsight. So far, this work has addressed the structure of the pathways rather than their activity. Future work will attempt to determine whether it is possible to strengthen such pathways to improve visual ability. DOI:http://dx.doi.org/10.7554/eLife.08935.002
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Affiliation(s)
- Sara Ajina
- Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom.,Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Franco Pestilli
- Department of Psychological and Brain Sciences, Programs in Neuroscience and Cognitive Science, Indiana University Network Science Institute, Indiana University, Bloomington, United States
| | - Ariel Rokem
- Department of Psychology, Stanford University, Stanford, United States.,eScience Institute, University of Washington, Seattle, United States
| | - Christopher Kennard
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Holly Bridge
- Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom.,Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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34
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He XF, Lan Y, Zhang Q, Liang FY, Luo CM, Xu GQ, Pei Z. GABA-ergic interneurons involved in transcallosal inhibition of the visual cortices in vivo in mice. Physiol Behav 2015; 151:502-8. [PMID: 26318391 DOI: 10.1016/j.physbeh.2015.08.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 08/17/2015] [Accepted: 08/18/2015] [Indexed: 01/17/2023]
Abstract
In the current study we investigated the role of the corpus callosum, particularly the gamma-aminobutyric acid-ergic (GABAergic) projection neurons involved in interhemispheric inhibition (IHI). In order to explore IHI in primary visual cortices, we adopted a protocol whereby we performed a direct current lesion of the unilateral primary visual cortex with or without posterior callosotomy, and used two-photon Ca(2+)in vivo imaging on the opposite unaffected region to detect neural activities in mice. Following this procedure, the numbers of vesicular GABAergic transporters (VGATs) and GABAergic interneurons in the unaffected primary cortex were determined using immunofluorescence staining. Results indicated that following unilateral visual cortical lesioning without callosotomy, the neuronal Ca(2+) activities in the opposite side were significantly increased. However, the neuronal activities of the unaffected visual cortex in animals with unilateral cortical lesion with callosotomy were not significantly different. Additionally, there was no significant difference in the numbers of GABAergic interneurons in the unaffected region between each group, while the number of VGATs in the unaffected region was significantly decreased following unilateral visual cortical lesion without callosotomy, which was unchanged once with callosotomy. Finally, callosotomy alone without cortical lesioning produced no change in neuronal activities, the number of GABAergic interneurons or VGATs. Our results demonstrate that IHI between the homologous primary visual cortices occurs via the corpus callosum, and further indicate the important involvement of long-range GABAergic interneurons in transcallosal inhibition.
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Affiliation(s)
- Xiao-fei He
- Department of Rehabilitation Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Yue Lan
- Department of Rehabilitation Medicine, Guangzhou First People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Qun Zhang
- Department of Rehabilitation Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Feng-yin Liang
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Chuan-ming Luo
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Guang-qing Xu
- Department of Rehabilitation Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
| | - Zhong Pei
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
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35
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Abstract
When the human primary visual cortex (V1) is damaged, the dominant geniculo-striate pathway can no longer convey visual information to the occipital cortex. However, many patients with such damage retain some residual visual function that must rely on an alternative pathway directly to extrastriate occipital regions. This residual vision is most robust for moving stimuli, suggesting a role for motion area hMT+. However, residual vision also requires high-contrast stimuli, which is inconsistent with hMT+ sensitivity to contrast in which even low-contrast levels elicit near-maximal neural activation. We sought to investigate this discrepancy by measuring behavioral and neural responses to increasing contrast in patients with V1 damage. Eight patients underwent behavioral testing and functional magnetic resonance imaging to record contrast sensitivity in hMT+ of their damaged hemisphere, using Gabor stimuli with a spatial frequency of 1 cycle/°. The responses from hMT+ of the blind hemisphere were compared with hMT+ and V1 responses in the sighted hemisphere of patients and a group of age-matched controls. Unlike hMT+, neural responses in V1 tend to increase linearly with increasing contrast, likely reflecting a dominant parvocellular channel input. Across all patients, the responses in hMT+ of the blind hemisphere no longer showed early saturation but increased linearly with contrast. Given the spatiotemporal parameters used in this study and the known direct subcortical projections from the koniocellular layers of the lateral geniculate nucleus to hMT+, we propose that this altered contrast sensitivity in hMT+ could be consistent with input from the koniocellular pathway.
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Nonlinear population receptive field changes in human area V5/MT+ of healthy subjects with simulated visual field scotomas. Neuroimage 2015; 120:176-90. [PMID: 26146195 PMCID: PMC5327354 DOI: 10.1016/j.neuroimage.2015.06.085] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 05/25/2015] [Accepted: 06/29/2015] [Indexed: 11/23/2022] Open
Abstract
There is extensive controversy over whether the adult visual cortex is able to reorganize following visual field loss (scotoma) as a result of retinal or cortical lesions. Functional magnetic resonance imaging (fMRI) methods provide a useful tool to study the aggregate receptive field properties and assess the capacity of the human visual cortex to reorganize following injury. However, these methods are prone to biases near the boundaries of the scotoma. Retinotopic changes resembling reorganization have been observed in the early visual cortex of normal subjects when the visual stimulus is masked to simulate retinal or cortical scotomas. It is not known how the receptive fields of higher visual areas, like hV5/MT+, are affected by partial stimulus deprivation. We measured population receptive field (pRF) responses in human area V5/MT+ of 5 healthy participants under full stimulation and compared them with responses obtained from the same area while masking the left superior quadrant of the visual field (“artificial scotoma” or AS). We found that pRF estimations in area hV5/MT+ are nonlinearly affected by the AS. Specifically, pRF centers shift towards the AS, while the pRF amplitude increases and the pRF size decreases near the AS border. The observed pRF changes do not reflect reorganization but reveal important properties of normal visual processing under different test-stimulus conditions.
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Abed Rabbo F, Koch G, Lefèvre C, Seizeur R. Direct geniculo-extrastriate pathways: a review of the literature. Surg Radiol Anat 2015; 37:891-9. [DOI: 10.1007/s00276-015-1450-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/19/2015] [Indexed: 01/23/2023]
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Kavcic V, Triplett RL, Das A, Martin T, Huxlin KR. Role of inter-hemispheric transfer in generating visual evoked potentials in V1-damaged brain hemispheres. Neuropsychologia 2015; 68:82-93. [PMID: 25575450 DOI: 10.1016/j.neuropsychologia.2015.01.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 12/11/2014] [Accepted: 01/05/2015] [Indexed: 11/16/2022]
Abstract
Partial cortical blindness is a visual deficit caused by unilateral damage to the primary visual cortex, a condition previously considered beyond hopes of rehabilitation. However, recent data demonstrate that patients may recover both simple and global motion discrimination following intensive training in their blind field. The present experiments characterized motion-induced neural activity of cortically blind (CB) subjects prior to the onset of visual rehabilitation. This was done to provide information about visual processing capabilities available to mediate training-induced visual improvements. Visual Evoked Potentials (VEPs) were recorded from two experimental groups consisting of 9 CB subjects and 9 age-matched, visually-intact controls. VEPs were collected following lateralized stimulus presentation to each of the 4 visual field quadrants. VEP waveforms were examined for both stimulus-onset (SO) and motion-onset (MO) related components in postero-lateral electrodes. While stimulus presentation to intact regions of the visual field elicited normal SO-P1, SO-N1, SO-P2 and MO-N2 amplitudes and latencies in contralateral brain regions of CB subjects, these components were not observed contralateral to stimulus presentation in blind quadrants of the visual field. In damaged brain hemispheres, SO-VEPs were only recorded following stimulus presentation to intact visual field quadrants, via inter-hemispheric transfer. MO-VEPs were only recorded from damaged left brain hemispheres, possibly reflecting a native left/right asymmetry in inter-hemispheric connections. The present findings suggest that damaged brain hemispheres contain areas capable of responding to visual stimulation. However, in the absence of training or rehabilitation, these areas only generate detectable VEPs in response to stimulation of the intact hemifield of vision.
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Affiliation(s)
- Voyko Kavcic
- Institute of Gerontology, Wayne State University, Detroit, USA
| | - Regina L Triplett
- Hobart and William Smith Colleges, Geneva, NY, USA; Flaum Eye Institute, University of Rochester, Rochester, NY, USA
| | - Anasuya Das
- Flaum Eye Institute, University of Rochester, Rochester, NY, USA
| | - Tim Martin
- Dept. Psychology, Kennesaw State University, Kennesaw, GA, USA
| | - Krystel R Huxlin
- Flaum Eye Institute, University of Rochester, Rochester, NY, USA; Center for Visual Science, University of Rochester, Rochester, NY, USA.
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Ajina S, Kennard C, Rees G, Bridge H. Motion area V5/MT+ response to global motion in the absence of V1 resembles early visual cortex. ACTA ACUST UNITED AC 2014; 138:164-78. [PMID: 25433915 PMCID: PMC4285193 DOI: 10.1093/brain/awu328] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Motion area V5/MT+ shows a variety of characteristic visual responses, often linked to perception, which are heavily influenced by its rich connectivity with the primary visual cortex (V1). This human motion area also receives a number of inputs from other visual regions, including direct subcortical connections and callosal connections with the contralateral hemisphere. Little is currently known about such alternative inputs to V5/MT+ and how they may drive and influence its activity. Using functional magnetic resonance imaging, the response of human V5/MT+ to increasing the proportion of coherent motion was measured in seven patients with unilateral V1 damage acquired during adulthood, and a group of healthy age-matched controls. When V1 was damaged, the typical V5/MT+ response to increasing coherence was lost. Rather, V5/MT+ in patients showed a negative trend with coherence that was similar to coherence-related activity in V1 of healthy control subjects. This shift to a response-pattern more typical of early visual cortex suggests that in the absence of V1, V5/MT+ activity may be shaped by similar direct subcortical input. This is likely to reflect intact residual pathways rather than a change in connectivity, and has important implications for blindsight function. It also confirms predictions that V1 is critically involved in normal V5/MT+ global motion processing, consistent with a convergent model of V1 input to V5/MT+. Historically, most attempts to model cortical visual responses do not consider the contribution of direct subcortical inputs that may bypass striate cortex, such as input to V5/MT+. We have shown that the signal change driven by these non-striate pathways can be measured, and suggest that models of the intact visual system may benefit from considering their contribution.
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Affiliation(s)
- Sara Ajina
- 1 FMRIB Centre, University of Oxford, UK 2 Nuffield Department of Clinical Neurosciences, University of Oxford, UK
| | | | - Geraint Rees
- 3 Wellcome Trust Centre for Neuroimaging, University College London, UK 4 Institute of Cognitive Neuroscience, University College London, UK
| | - Holly Bridge
- 1 FMRIB Centre, University of Oxford, UK 2 Nuffield Department of Clinical Neurosciences, University of Oxford, UK
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Braunitzer G, Őze A, Nagy T, Eördegh G, Puszta A, Benedek G, Kéri S, Nagy A. The effect of simultaneous flickering light stimulation on global form and motion perception thresholds. Neurosci Lett 2014; 583:87-91. [PMID: 25250539 DOI: 10.1016/j.neulet.2014.09.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 09/12/2014] [Indexed: 11/28/2022]
Abstract
The question regarding the exact function of the primary visual cortex (V1) in vision has been around ever since the description of residual vision after damage to this cortical area by Riddoch in 1917. In 2002, Schoenfeld and colleagues proposed that V1 can be saturated by flashes of light, by which the function of V1-bypassing visual pathways can be "unmasked". The Schoenfeld group found that light flashes applied on stimulus onset led to the elevation of brightness increment detection thresholds, but left motion detection thresholds unaltered. Although the proposed method (i.e. the use of light flashes to induce refractoriness in V1) could be a simple, cheap and elegant way of exploring V1 functions, no study has followed up on this. Therefore it is not known if it works at all with other types of stimuli. For that reason, we decided to revisit the idea in a modified form. Global form and motion perception thresholds were assessed with static Glass pattern stimuli and random dot kinematograms, with and without 12Hz flickering light stimulation. Global motion thresholds were almost unaltered by flickering stimulation, while a significant threshold elevation was caused in the global form perception task. The strongest conclusion allowed by our data is that simultaneous flickering photostimulation elevates global form perception thresholds but not global motion perception thresholds. This is in some way related to the refractoriness generated in an unsatisfactorily defined part of V1. We suggest that this does not necessarily reflect the activity of V1-bypassing pathways, and propose that the application of light flashes is a method that deserves more attention in the exploration of the V1-dependent and independent elements of visual consciousness in human subjects.
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Affiliation(s)
- Gábor Braunitzer
- University of Szeged, Faculty of Medicine, Department of Physiology, Hungary.
| | - Attila Őze
- University of Szeged, Faculty of Medicine, Department of Physiology, Hungary
| | - Tibor Nagy
- University of Szeged, Faculty of Medicine, Department of Physiology, Hungary
| | - Gabriella Eördegh
- University of Szeged, Faculty of Medicine, Department of Psychiatry, Hungary
| | - András Puszta
- University of Szeged, Faculty of Medicine, Department of Physiology, Hungary
| | - György Benedek
- University of Szeged, Faculty of Medicine, Department of Physiology, Hungary
| | - Szabolcs Kéri
- University of Szeged, Faculty of Medicine, Department of Physiology, Hungary
| | - Attila Nagy
- University of Szeged, Faculty of Medicine, Department of Physiology, Hungary
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Urbanski M, Coubard OA, Bourlon C. Visualizing the blind brain: brain imaging of visual field defects from early recovery to rehabilitation techniques. Front Integr Neurosci 2014; 8:74. [PMID: 25324739 PMCID: PMC4179723 DOI: 10.3389/fnint.2014.00074] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 09/03/2014] [Indexed: 01/04/2023] Open
Abstract
Visual field defects (VFDs) are one of the most common consequences observed after brain injury, especially after a stroke in the posterior cerebral artery territory. Less frequently, tumors, traumatic brain injury, brain surgery or demyelination can also determine various visual disabilities, from a decrease in visual acuity to cerebral blindness. Visual field defects is a factor of bad functional prognosis as it compromises many daily life activities (e.g., obstacle avoidance, driving, and reading) and therefore the patient's quality of life. Spontaneous recovery seems to be limited and restricted to the first 6 months, with the best chance of improvement at 1 month. The possible mechanisms at work could be partly due to cortical reorganization in the visual areas (plasticity) and/or partly to the use of intact alternative visual routes, first identified in animal studies and possibly underlying the phenomenon of blindsight. Despite processes of early recovery, which is rarely complete, and learning of compensatory strategies, the patient's autonomy may still be compromised at more chronic stages. Therefore, various rehabilitation therapies based on neuroanatomical knowledge have been developed to improve VFDs. These use eye-movement training techniques (e.g., visual search, saccadic eye movements), reading training, visual field restitution (the Vision Restoration Therapy, VRT), or perceptual learning. In this review, we will focus on studies of human adults with acquired VFDs, which have used different imaging techniques (Positron Emission Tomography, PET; Diffusion Tensor Imaging, DTI; functional Magnetic Resonance Imaging, fMRI; Magneto Encephalography, MEG) or neurostimulation techniques (Transcranial Magnetic Stimulation, TMS; transcranial Direct Current Stimulation, tDCS) to show brain activations in the course of spontaneous recovery or after specific rehabilitation techniques.
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Affiliation(s)
- Marika Urbanski
- Service de Médecine et de Réadaptation Gériatrique et Neurologique, Hôpitaux de Saint-Maurice Saint-Maurice, France ; Inserm, U 1127, ICM FrontLab Paris, France ; CNRS, UMR 7225, ICM FrontLab Paris, France ; Sorbonne Universités, UPMC Univ Paris 06, UMRS 1127 Paris, France ; Institut du Cerveau et de la Moelle Épinière, ICM FrontLab Paris, France
| | - Olivier A Coubard
- The Neuropsychological Laboratory, CNS-Fed Paris, France ; Laboratoire Psychologie de la Perception, UMR 8242 CNRS-Université Paris Descartes Paris, France
| | - Clémence Bourlon
- Service de Médecine et de Réadaptation, Clinique Les Trois Soleils Boissise-le-Roi, France
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Millington RS, Yasuda CL, Jindahra P, Jenkinson M, Barbur JL, Kennard C, Cendes F, Plant GT, Bridge H. Quantifying the pattern of optic tract degeneration in human hemianopia. J Neurol Neurosurg Psychiatry 2014; 85:379-86. [PMID: 24163431 DOI: 10.1136/jnnp-2013-306577] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND The existence of transsynaptic retrograde degeneration (TRD) in the human visual system has been established, however the dependence of TRD on different factors such as lesion location, size and manner of lesion acquisition has yet to be quantified. METHODS We obtained T1-weighted structural and diffusion-weighted images for 26 patients with adult-acquired or congenital hemianopia and 12 age-matched controls. The optic tract (OT) was defined and measured in the structural and diffusion-weighted images, and degeneration assessed by comparing the integrity of tracts in the lesioned and in the undamaged hemisphere. RESULTS OT degeneration was found in all patients with established lesions, regardless of lesion location. In patients with acquired lesions, the larger the initial lesion, the greater is the resulting TRD. However, this was not the case for congenital patients, who generally showed greater degeneration than would be predicted by lesion size. A better predictor of TRD was the size of the visual field deficit, which was correlated with degeneration across all patients. Interestingly, although diffusion-weighted imaging (DWI) is more frequently used to examine white matter tracts, in this study the T1-weighted scans gave a better indication of the extent of tract degeneration. CONCLUSIONS We conclude that TRD of the OT occurs in acquired and congenital hemianopia, is correlated with visual field loss, and is most severe in congenital cases. Understanding the pattern of TRD may help to predict effects of any visual rehabilitation training.
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Affiliation(s)
- Rebecca S Millington
- Oxford Centre for functional Magnetic Resonance Imaging of the Brain (FMRIB), University of Oxford, , Oxford, UK
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Millington RS, Ajina S, Bridge H. Novel brain imaging approaches to understand acquired and congenital neuro-ophthalmological conditions. Curr Opin Neurol 2014; 27:92-97. [PMID: 24300791 PMCID: PMC3983755 DOI: 10.1097/wco.0000000000000050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
PURPOSE OF REVIEW The arrival of large datasets and the on-going refinement of neuroimaging technology have led to a number of recent advances in our understanding of visual pathway disorders. This work can broadly be classified into two areas, both of which are important when considering the optimal management strategies. The first looks at the delineation of damage, teasing out subtle changes to (specific components of) the visual pathway, which may help evaluate the severity and extent of disease. The second uses neuroimaging to investigate neuroplasticity, via changes in connectivity, cortical thickness, and retinotopic maps within the visual cortex. RECENT FINDINGS Here, we give consideration to both acquired and congenital patients with damage to the visual pathway, and how they differ. Congenital disorders of the peripheral visual system can provide insight into the large-scale reorganization of the visual cortex: these are investigated with reference to disorders of the optic chiasm and anophthalmia (absence of the eyes). In acquired conditions, we consider the recent work describing patterns of degeneration, both following single insult and in neurodegenerative conditions. We also discuss the developments in functional neuroimaging, with particular reference to work on hemianopia and the controversial suggestion of cortical reorganization following acquired retinal injury. SUMMARY Techniques for comparing neuro-ophthalmological conditions with healthy visual systems provide sensitive metrics to uncover subtle differences in grey and white matter structure of the brain. It is now possible to compare the massive reorganization present in congenital conditions with the apparent lack of plasticity following acquired damage.
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Affiliation(s)
| | - Sara Ajina
- Corresponding author: Dr Sara Ajina, Oxford Centre for FMRI of the Brain, John Radcliffe Hospital, Oxford, OX3 9DU, UK. Tel: +44-1865-740348;
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d'Almeida OC, Mateus C, Reis A, Grazina MM, Castelo-Branco M. Long term cortical plasticity in visual retinotopic areas in humans with silent retinal ganglion cell loss. Neuroimage 2013; 81:222-230. [DOI: 10.1016/j.neuroimage.2013.05.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 04/27/2013] [Accepted: 05/05/2013] [Indexed: 01/29/2023] Open
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Clatworthy PL, Warburton EA, Tolhurst DJ, Baron JC. Visual contrast sensitivity deficits in 'normal' visual field of patients with homonymous visual field defects due to stroke: a pilot study. Cerebrovasc Dis 2013; 36:329-35. [PMID: 24193224 DOI: 10.1159/000354810] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 08/05/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Homonymous visual field defects (VFD) are common following stroke, and often recover, partially or fully, by unknown mechanisms. In clinical practice, visual field recovered on perimetry is often considered perceptually normal. However, studies have shown contrast sensitivity (CS) deficits in patients with stroke and homonymous VFD. This study investigated the origin of visual CS loss in patients with VFD due to stroke. We hypothesised that CS deficits would be found in visual field areas appearing normal on perimetry, in patients with ischaemic stroke affecting the retrochiasmal visual system, and that the spatiotemporal properties of this CS loss would be consistent with those of 'blindsight', perhaps suggesting similar underlying mechanisms. METHODS CS measurements were made in 20 healthy participants, and in 7 patients with stroke causing homonymous VFD sparing foveal vision, measured using Humphrey static perimetry (SITA-Fast 24-2 procedure). Importantly, patients with concomitant visuospatial neglect were excluded. CS measurements were made using a modification of the method of increasing contrast, corrected for reaction time. Three spatial stimuli were used, at several spatial frequencies: (1) large sinusoidal gratings; (2) foveal Gabor patches; and (3) Gabor patches presenting in the putatively recovered visual field, near VFD. Stimuli with different temporal profiles were used to selectively stimulate transient and sustained visual channels, to provide insight into mechanisms of visual loss and/or recovery. Analysis of variance (ANOVA) was used in the analysis of the measurements, allowing for correction for age and stimulus eccentricity. RESULTS ANOVA for sustained grating stimuli showed orientation-selective (horizontal) CS loss (p = 0.025); no such loss was apparent in the central visual field (foveal Gabor stimuli). Localised CS close to VFD was reduced in stroke-affected hemifields compared with unaffected hemifields (p ≤ 0.005), though these areas appeared normal on perimetry. In these areas, CS was relatively preserved for transient compared with sustained stimuli (Wilcoxon signed rank tests). CONCLUSIONS The finding of specific CS deficits in the normal-appearing visual field of patients with homonymous VFD due to stroke suggests that static perimetry provides an inadequate assessment of visual function in these patients, with clear implications for testing of vision in clinical practice. The results are consistent with relative sparing of the transient/magnocellular visual channel. These findings demand further investigation. If confirmed in larger, longitudinal studies, this will have important implications for the mechanisms of recovery, and may provide a target for visual rehabilitation - for example, using repeated detection practice ('perceptual learning').
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Affiliation(s)
- Philip L Clatworthy
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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Martin T, Das A, Huxlin KR. Visual cortical activity reflects faster accumulation of information from cortically blind fields. Brain 2013; 135:3440-52. [PMID: 23169923 DOI: 10.1093/brain/aws272] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Brain responses (from functional magnetic resonance imaging) and components of information processing were investigated in nine cortically blind observers performing a global direction discrimination task. Three of these subjects had responses in perilesional cortex in response to blind field stimulation, whereas the others did not. We used the EZ-diffusion model of decision making to understand how cortically blind subjects make a perceptual decision on stimuli presented within their blind field. We found that these subjects had slower accumulation of information in their blind fields as compared with their good fields and to intact controls. Within cortically blind subjects, activity in perilesional tissue, V3A and hMT+ was associated with a faster accumulation of information for deciding direction of motion of stimuli presented in the blind field. This result suggests that the rate of information accumulation is a critical factor in the degree of impairment in cortical blindness and varies greatly among affected individuals. Retraining paradigms that seek to restore visual functions might benefit from focusing on increasing the rate of information accumulation.
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Affiliation(s)
- Tim Martin
- Department of Psychology, Kennesaw State University, Kennesaw, GA 30144, USA.
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47
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Abstract
The primary visual cortex (V1) is the principal telencephalic recipient of visual input in humans and monkeys. It is unique among cortical areas in that its destruction results in chronic blindness. However, certain patients with V1 damage, though lacking visual awareness, exhibit visually guided behavior: blindsight. This phenomenon, together with evidence from electrophysiological, neuroimaging, and psychophysical experiments, has led to speculation that V1 activity has a special or direct role in generating conscious perception. To explore this issue, this article reviews experiments that have used two powerful paradigms--stimulus-induced perceptual suppression and chronic V1 ablation--each of which disrupts the ability to perceive salient visual stimuli. Focus is placed on recent neurophysiological, behavioral, and functional imaging studies from the nonhuman primate that shed light on V1's role in conscious awareness. In addition, anatomical pathways that relay visual information to the cortex during normal vision and in blindsight are reviewed. Although the critical role of V1 in primate vision follows naturally from its position as a bottleneck of visual signals, little evidence supports its direct contribution to visual awareness.
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Affiliation(s)
- David A Leopold
- Section on Cognitive Neurophysiology and Imaging, Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, USA.
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Bridge H, Harrold S, Holmes EA, Stokes M, Kennard C. Vivid visual mental imagery in the absence of the primary visual cortex. J Neurol 2011; 259:1062-70. [PMID: 22064977 PMCID: PMC3366182 DOI: 10.1007/s00415-011-6299-z] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 10/18/2011] [Indexed: 11/26/2022]
Abstract
The role of the primary visual cortex in visual mental imagery has provided significant debate in the imagery literature. Functional neuroimaging studies show considerable variation depending on task and technique. Patient studies can be difficult to interpret due to the diverse nature of cortical damage. The type of cortical damage in patient SBR is exceedingly rare as it is restricted to the gray matter of the calcarine sulcus. In this study, we show that in spite of his near-complete cortical blindness, SBR exhibits vivid visual mental imagery both behaviorally and when measured with functional magnetic resonance imaging. The pattern of cortical activation to visual mental imagery in SBR is indistinguishable from individual sighted subjects, in contrast to the visual perceptual responses, which are greatly attenuated.
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Affiliation(s)
- Holly Bridge
- FMRIB Centre, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK.
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