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Spiteri S, Crewther D. Neural Mechanisms of Visual Motion Anomalies in Autism: A Two-Decade Update and Novel Aetiology. Front Neurosci 2021; 15:756841. [PMID: 34790092 PMCID: PMC8591069 DOI: 10.3389/fnins.2021.756841] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 10/11/2021] [Indexed: 11/13/2022] Open
Abstract
The 21st century has seen dramatic changes in our understanding of the visual physio-perceptual anomalies of autism and also in the structure and development of the primate visual system. This review covers the past 20 years of research into motion perceptual/dorsal stream anomalies in autism, as well as new understanding of the development of primate vision. The convergence of this literature allows a novel developmental hypothesis to explain the physiological and perceptual differences of the broad autistic spectrum. Central to these observations is the development of motion areas MT+, the seat of the dorsal cortical stream, central area of pre-attentional processing as well as being an anchor of binocular vision for 3D action. Such development normally occurs via a transfer of thalamic drive from the inferior pulvinar → MT to the anatomically stronger but later-developing LGN → V1 → MT connection. We propose that autistic variation arises from a slowing in the normal developmental attenuation of the pulvinar → MT pathway. We suggest that this is caused by a hyperactive amygdala → thalamic reticular nucleus circuit increasing activity in the PIm → MT via response gain modulation of the pulvinar and hence altering synaptic competition in area MT. We explore the probable timing of transfer in dominance of human MT from pulvinar to LGN/V1 driving circuitry and discuss the implications of the main hypothesis.
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Affiliation(s)
- Samuel Spiteri
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, VIC, Australia
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2
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Scott JT, Bourne JA. Modelling behaviors relevant to brain disorders in the nonhuman primate: Are we there yet? Prog Neurobiol 2021; 208:102183. [PMID: 34728308 DOI: 10.1016/j.pneurobio.2021.102183] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 10/27/2021] [Accepted: 10/27/2021] [Indexed: 12/30/2022]
Abstract
Recent years have seen a profound resurgence of activity with nonhuman primates (NHPs) to model human brain disorders. From marmosets to macaques, the study of NHP species offers a unique window into the function of primate-specific neural circuits that are impossible to examine in other models. Examining how these circuits manifest into the complex behaviors of primates, such as advanced cognitive and social functions, has provided enormous insights to date into the mechanisms underlying symptoms of numerous neurological and neuropsychiatric illnesses. With the recent optimization of modern techniques to manipulate and measure neural activity in vivo, such as optogenetics and calcium imaging, NHP research is more well-equipped than ever to probe the neural mechanisms underlying pathological behavior. However, methods for behavioral experimentation and analysis in NHPs have noticeably failed to keep pace with these advances. As behavior ultimately lies at the junction between preclinical findings and its translation to clinical outcomes for brain disorders, approaches to improve the integrity, reproducibility, and translatability of behavioral experiments in NHPs requires critical evaluation. In this review, we provide a unifying account of existing brain disorder models using NHPs, and provide insights into the present and emerging contributions of behavioral studies to the field.
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Affiliation(s)
- Jack T Scott
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, Australia
| | - James A Bourne
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, Australia.
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3
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Visual Cortical Area MT Is Required for Development of the Dorsal Stream and Associated Visuomotor Behaviors. J Neurosci 2021; 41:8197-8209. [PMID: 34417331 DOI: 10.1523/jneurosci.0824-21.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 07/07/2021] [Accepted: 08/09/2021] [Indexed: 01/11/2023] Open
Abstract
The middle temporal (MT) area of the extrastriate visual cortex has long been studied in adulthood for its distinctive physiological properties and function as a part of the dorsal stream, yet interestingly it possesses a similar maturation profile as the primary visual cortex (V1). Here, we examined whether an early-life lesion in MT of marmoset monkeys (six female, two male) altered the dorsal stream development and the behavioral precision of reaching-to-grasp sequences. We observed permanent changes in the anatomy of cortices associated with both reaching (parietal and medial intraparietal areas) and grasping (anterior intraparietal area), as well as in reaching-and-grasping behaviors. In addition, we observed a significant impact on the anatomy of V1 and the direction sensitivity of V1 neurons in the lesion projection zone. These findings indicate that area MT is a crucial node in the development of primate vision, affecting both V1 and areas in the dorsal visual pathway known to mediate visually guided manual behaviors.SIGNIFICANCE STATEMENT Previous studies have identified a role for the MT area of the visual cortex in perceiving motion, yet none have examined its central role in the development of the visual cortex and in the establishment of visuomotor behaviors. To address this, we used a unilateral MT lesion model in neonatal marmosets before examining the anatomic, physiological, and behavioral consequences. In adulthood, we observed perturbations in goal-orientated reach-and-grasp behavior, altered direction selectivity of V1 neurons, and changes in the cytoarchitecture throughout dorsal stream areas. This study highlights the importance of MT as a central node in visual system development and consequential visuomotor activity.
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4
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Cortical Visual Impairment in Childhood: 'Blindsight' and the Sprague Effect Revisited. Brain Sci 2021; 11:brainsci11101279. [PMID: 34679344 PMCID: PMC8533908 DOI: 10.3390/brainsci11101279] [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: 08/09/2021] [Revised: 09/14/2021] [Accepted: 09/24/2021] [Indexed: 11/29/2022] Open
Abstract
The paper discusses and provides support for diverse processes of brain plasticity in visual function after damage in infancy and childhood in comparison with injury that occurs in the adult brain. We provide support and description of neuroplastic mechanisms in childhood that do not seemingly exist in the same way in the adult brain. Examples include the ability to foster the development of thalamocortical connectivities that can circumvent the lesion and reach their cortical destination in the occipital cortex as the developing brain is more efficient in building new connections. Supporting this claim is the fact that in those with central visual field defects we can note that the extrastriatal visual connectivities are greater when a lesion occurs earlier in life as opposed to in the neurologically mature adult. The result is a significantly more optimized system of visual and spatial exploration within the ‘blind’ field of view. The discussion is provided within the context of “blindsight” and the “Sprague Effect”.
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5
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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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6
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Homman-Ludiye J, Bourne JA. The Marmoset: The Next Frontier in Understanding the Development of the Human Brain. ILAR J 2021; 61:248-259. [PMID: 33620074 DOI: 10.1093/ilar/ilaa028] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 11/13/2020] [Accepted: 11/20/2020] [Indexed: 12/22/2022] Open
Abstract
Rodent models, particularly mice, have dominated the field of developmental neuroscience for decades, like they have in most fields of biomedicine research. However, with 80 million years since rodents and primates last shared a common ancestor, the use of mice to model the development of the human brain is not without many shortcomings. The human brain diverges from the mouse brain in many aspects and is comprised of novel structures as well as diversified cellular subtypes. While these newly evolved features have no equivalent in rodents, they are observed in nonhuman primates. Therefore, elucidating the cellular mechanisms underlying the development and maturation of the healthy and diseased human brain can be achieved using less complex nonhuman primates. Historically, macaques were the preferred nonhuman primate model. However, over the past decade, the New World marmoset monkey (Callithrix jacchus) has gained more importance, particularly in the field of neurodevelopment. With its small size, twin or triplet birth, and prosocial behavior, the marmoset is an ideal model to study normal brain development as well as neurodevelopmental disorders, which are often associated with abnormal social behaviors. The growing interest in the marmoset has prompted many comparative studies, all demonstrating that the marmoset brain closely resembles that of the human and is perfectly suited to model human brain development. The marmoset is thus poised to extend its influence in the field of neurodevelopment and will hopefully fill the gaps that the mouse has left in our understanding of how our brain forms and how neurodevelopmental disorders originate.
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Affiliation(s)
- Jihane Homman-Ludiye
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - James A Bourne
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
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7
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de Souza BOF, Frigon ÉM, Tremblay-Laliberté R, Casanova C, Boire D. Laminar distribution of cortical projection neurons to the pulvinar: A comparative study in cats and mice. J Comp Neurol 2020; 529:2055-2069. [PMID: 33226127 DOI: 10.1002/cne.25072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 11/04/2020] [Accepted: 11/12/2020] [Indexed: 01/19/2023]
Abstract
The cortical processing of visual information is thought to follow a hierarchical framework. This framework of connections between visual areas is based on the laminar patterns of direct feedforward and feedback cortico-cortical projections. However, this view ignores the cortico-thalamo-cortical projections to the pulvinar nucleus in the thalamus, which provides an alternative transthalamic information transfer between cortical areas. It was proposed that corticothalamic (CT) pathways follow a similar hierarchical pattern as cortico-cortical connections. Two main types of CT projections have been recognized: drivers and modulators. Drivers originate mainly in Layer 5 whereas modulators are from Layer 6. Little is known about the laminar distribution of these projections to the pulvinar across visual cortical areas. Here, we analyzed the distribution of CT neurons projecting to the lateral posterior (LP) thalamus in two species: cats and mice. Injections of the retrograde tracer fragment B of cholera toxin (CTb) were performed in the LP. The morphology and cortical laminar distribution of CTb-labeled neurons was assessed. In cats, neurons were mostly found in Layer 6 except in Area 17, where they were mostly in Layer 5. In contrast, CT neurons in mice were mostly located in Layer 6 across all areas. Thus, our results demonstrate that CT projections in mice do not follow the same organization as cats suggesting that the transthalamic pathways play distinct roles in these species.
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Affiliation(s)
| | - Éve-Marie Frigon
- Département d'Anatomie, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada
| | | | | | - Denis Boire
- Département d'Anatomie, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.,École d'Optométrie, Université de Montréal, Montréal, Québec, Canada
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8
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9
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The influence of subcortical shortcuts on disordered sensory and cognitive processing. Nat Rev Neurosci 2020; 21:264-276. [PMID: 32269315 DOI: 10.1038/s41583-020-0287-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/28/2020] [Indexed: 12/14/2022]
Abstract
The very earliest stages of sensory processing have the potential to alter how we perceive and respond to our environment. These initial processing circuits can incorporate subcortical regions, such as the thalamus and brainstem nuclei, which mediate complex interactions with the brain's cortical processing hierarchy. These subcortical pathways, many of which we share with other animals, are not merely vestigial but appear to function as 'shortcuts' that ensure processing efficiency and preservation of vital life-preserving functions, such as harm avoidance, adaptive social interactions and efficient decision-making. Here, we propose that functional interactions between these higher-order and lower-order brain areas contribute to atypical sensory and cognitive processing that characterizes numerous neuropsychiatric disorders.
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10
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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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11
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Retinotopic specializations of cortical and thalamic inputs to area MT. Proc Natl Acad Sci U S A 2019; 116:23326-23331. [PMID: 31659044 DOI: 10.1073/pnas.1909799116] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Retinotopic specializations in the ventral visual stream, especially foveal adaptations, provide primates with high-acuity vision in the central visual field. However, visual field specializations have not been studied in the dorsal visual stream, dedicated to processing visual motion and visually guided behaviors. To investigate this, we injected retrograde neuronal tracers occupying the whole visuotopic representation of the middle temporal (MT) visual area in marmoset monkeys and studied the distribution and morphology of the afferent primary visual cortex (V1) projections. Contrary to previous reports, we found a heterogeneous population of V1-MT projecting neurons distributed in layers 3C and 6. In layer 3C, spiny stellate neurons were distributed mainly in foveal representations, while pyramidal morphologies were characteristic of peripheral eccentricities. This primate adaptation of the V1 to MT pathway is arranged in a way that we had not previously understood, with abundant stellate projection neurons in the high-resolution foveal portions, suggesting rapid relay of motion information to visual area MT. We also describe that the medial portion of the inferior pulvinar (PIm), which is the main thalamic input to area MT, shows a retinotopic organization, likely reflecting the importance of this pathway during development and the establishment of area MT topography.
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12
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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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13
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McFadyen J. Investigating the Subcortical Route to the Amygdala Across Species and in Disordered Fear Responses. J Exp Neurosci 2019; 13:1179069519846445. [PMID: 31068755 PMCID: PMC6495431 DOI: 10.1177/1179069519846445] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/04/2019] [Indexed: 01/08/2023] Open
Abstract
Over the past few decades, evidence has come to light that there is a rapid subcortical shortcut that transmits visual information to the amygdala, effectively bypassing the visual cortex. This pathway purportedly runs from the superior colliculus to the amygdala via the pulvinar, and thus presents a methodological challenge to study noninvasively in the human brain. Here, we present our recent work where we reliably reconstructed the white matter structure and directional flow of neural signal along this pathway in over 600 healthy young adults. Critically, we found structure-function relationships for the pulvinar-amygdala connection, where people with greater fibre density had stronger functional neural coupling and were also better at recognising fearful facial expressions. These results tie together recent anatomical evidence from other visual primates with very recent optogenetic research on rodents demonstrating a functional role of this pathway in producing fear responses. Here, we discuss how this pathway might operate alongside other thalamo-cortical circuits (such as pulvinar to middle temporal area) and how its structure and function may change according to the sensory input it receives. This newly established circuit might play a potentially important role in autism and/or anxiety disorders.
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Affiliation(s)
- Jessica McFadyen
- Queensland Brain Institute, University of Queensland, Brisbane, QLD, Australia
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14
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Collins E, Freud E, Kainerstorfer JM, Cao J, Behrmann M. Temporal Dynamics of Shape Processing Differentiate Contributions of Dorsal and Ventral Visual Pathways. J Cogn Neurosci 2019; 31:821-836. [PMID: 30883289 DOI: 10.1162/jocn_a_01391] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Although shape perception is primarily considered a function of the ventral visual pathway, previous research has shown that both dorsal and ventral pathways represent shape information. Here, we examine whether the shape-selective electrophysiological signals observed in dorsal cortex are a product of the connectivity to ventral cortex or are independently computed. We conducted multiple EEG studies in which we manipulated the input parameters of the stimuli so as to bias processing to either the dorsal or ventral visual pathway. Participants viewed displays of common objects with shape information parametrically degraded across five levels. We measured shape sensitivity by regressing the amplitude of the evoked signal against the degree of stimulus scrambling. Experiment 1, which included grayscale versions of the stimuli, served as a benchmark establishing the temporal pattern of shape processing during typical object perception. These stimuli evoked broad and sustained patterns of shape sensitivity beginning as early as 50 msec after stimulus onset. In Experiments 2 and 3, we calibrated the stimuli such that visual information was delivered primarily through parvocellular inputs, which mainly project to the ventral pathway, or through koniocellular inputs, which mainly project to the dorsal pathway. In the second and third experiments, shape sensitivity was observed, but in distinct spatio-temporal configurations from each other and from that elicited by grayscale inputs. Of particular interest, in the koniocellular condition, shape selectivity emerged earlier than in the parvocellular condition. These findings support the conclusion of distinct dorsal pathway computations of object shape, independent from the ventral pathway.
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Affiliation(s)
- Elliot Collins
- Carnegie Mellon University, Pittsburgh, PA.,School of Medicine University of Pittsburgh
| | - Erez Freud
- Carnegie Mellon University, Pittsburgh, PA.,York University, Toronto, Canada
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15
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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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16
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Karl JM, Wilson AM, Bertoli ME, Shubear NS. Touch the table before the target: contact with an underlying surface may assist the development of precise visually controlled reach and grasp movements in human infants. Exp Brain Res 2018; 236:2185-2207. [PMID: 29797280 DOI: 10.1007/s00221-018-5293-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 05/16/2018] [Indexed: 11/28/2022]
Abstract
Multiple motor channel theory posits that skilled hand movements arise from the coordinated activation of separable neural circuits in parietofrontal cortex, each of which produces a distinct movement and responds to different sensory inputs. Prehension, the act of reaching to grasp an object, consists of at least two movements: a reach movement that transports the hand to a target location and a grasp movement that shapes and closes the hand for target acquisition. During early development, discrete pre-reach and pre-grasp movements are refined based on proprioceptive and tactile feedback, but are gradually coordinated together into a singular hand preshaping movement under feedforward visual control. The neural and behavioural factors that enable this transition are currently unknown. In an attempt to identify such factors, the present descriptive study used frame-by-frame video analysis to examine 9-, 12-, and 15-month-old infants, along with sighted and unsighted adults, as they reached to grasp small ring-shaped pieces of cereal (Cheerios) resting on a table. Compared to sighted adults, infants and unsighted adults were more likely to make initial contact with the underlying table before they contacted the target. The way in which they did so was also similar in that they generally contacted the table with the tip of the thumb and/or pinky finger, a relatively open hand, and poor reach accuracy. Despite this, infants were similar to sighted adults in that they tended to use a pincer digit, defined as the tip of the thumb or index finger, to subsequently contact the target. Only in infants was this ability related to their having made prior contact with the underlying table. The results are discussed in relation to the idea that initial contact with an underlying table or surface may assist infants in learning to use feedforward visual control to direct their digits towards a precise visual target.
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Affiliation(s)
- Jenni M Karl
- Department of Psychology, Thompson Rivers University, 805 TRU Way, Kamloops, BC, V2C 0C8, Canada.
| | - Alexis M Wilson
- Department of Psychology, Thompson Rivers University, 805 TRU Way, Kamloops, BC, V2C 0C8, Canada
| | - Marisa E Bertoli
- Department of Psychology, Thompson Rivers University, 805 TRU Way, Kamloops, BC, V2C 0C8, Canada
| | - Noor S Shubear
- Department of Psychology, Thompson Rivers University, 805 TRU Way, Kamloops, BC, V2C 0C8, Canada
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17
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Psychophysical and neuroimaging responses to moving stimuli in a patient with the Riddoch phenomenon due to bilateral visual cortex lesions. Neuropsychologia 2018; 128:150-165. [PMID: 29753019 DOI: 10.1016/j.neuropsychologia.2018.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 05/07/2018] [Accepted: 05/07/2018] [Indexed: 01/31/2023]
Abstract
Patients with injury to early visual cortex or its inputs can display the Riddoch phenomenon: preserved awareness for moving but not stationary stimuli. We provide a detailed case report of a patient with the Riddoch phenomenon, MC. MC has extensive bilateral lesions to occipitotemporal cortex that include most early visual cortex and complete blindness in visual field perimetry testing with static targets. Nevertheless, she shows a remarkably robust preserved ability to perceive motion, enabling her to navigate through cluttered environments and perform actions like catching moving balls. Comparisons of MC's structural magnetic resonance imaging (MRI) data to a probabilistic atlas based on controls reveals that MC's lesions encompass the posterior, lateral, and ventral early visual cortex bilaterally (V1, V2, V3A/B, LO1/2, TO1/2, hV4 and VO1 in both hemispheres) as well as more extensive damage to right parietal (inferior parietal lobule) and left ventral occipitotemporal cortex (VO1, PHC1/2). She shows some sparing of anterior occipital cortex, which may account for her ability to see moving targets beyond ~15 degrees eccentricity during perimetry. Most strikingly, functional and structural MRI revealed robust and reliable spared functionality of the middle temporal motion complex (MT+) bilaterally. Moreover, consistent with her preserved ability to discriminate motion direction in psychophysical testing, MC also shows direction-selective adaptation in MT+. A variety of tests did not enable us to discern whether input to MT+ was driven by her spared anterior occipital cortex or subcortical inputs. Nevertheless, MC shows rich motion perception despite profoundly impaired static and form vision, combined with clear preservation of activation in MT+, thus supporting the role of MT+ in the Riddoch phenomenon.
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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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Cavanaugh MR, Barbot A, Carrasco M, Huxlin KR. Feature-based attention potentiates recovery of fine direction discrimination in cortically blind patients. Neuropsychologia 2017; 128:315-324. [PMID: 29237554 DOI: 10.1016/j.neuropsychologia.2017.12.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 12/02/2017] [Accepted: 12/04/2017] [Indexed: 01/23/2023]
Abstract
Training chronic, cortically-blind (CB) patients on a coarse [left-right] direction discrimination and integration (CDDI) task recovers performance on this task at trained, blind field locations. However, fine direction difference (FDD) thresholds remain elevated at these locations, limiting the usefulness of recovered vision in daily life. Here, we asked if this FDD impairment can be overcome by training CB subjects with endogenous, feature-based attention (FBA) cues. Ten CB subjects were recruited and trained on CDDI and FDD with an FBA cue or FDD with a neutral cue. After completion of each training protocol, FDD thresholds were re-measured with both neutral and FBA cues at trained, blind-field locations and at corresponding, intact-field locations. In intact portions of the visual field, FDD thresholds were lower when tested with FBA than neutral cues. Training subjects in the blind field on the CDDI task improved FDD performance to the point that a threshold could be measured, but these locations remained impaired relative to the intact field. FDD training with neutral cues resulted in better blind field FDD thresholds than CDDI training, but thresholds remained impaired relative to intact field levels, regardless of testing cue condition. Importantly, training FDD in the blind field with FBA lowered FDD thresholds relative to CDDI training, and allowed the blind field to reach thresholds similar to the intact field, even when FBA trained subjects were tested with a neutral rather than FBA cue. Finally, FDD training appeared to also recover normal integration thresholds at trained, blind-field locations, providing an interesting double dissociation with respect to CDDI training. In summary, mechanisms governing FBA appear to function normally in both intact and impaired regions of the visual field following V1 damage. Our results mark the first time that FDD thresholds in CB fields have been seen to reach intact field levels of performance. Moreover, FBA can be leveraged during visual training to recover normal, fine direction discrimination and integration performance at trained, blind-field locations, potentiating visual recovery of more complex and precise aspects of motion perception in cortically-blinded fields.
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Affiliation(s)
- Matthew R Cavanaugh
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA; Neuroscience Graduate Program, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Antoine Barbot
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA
| | - Marisa Carrasco
- Department of Psychology and Center for Neural Science, New York University, New York, NY 10003, USA
| | - Krystel R Huxlin
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA
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