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Namgung E, Kwon SU, Han M, Kim G, Kim HY, Park K, Cho M, Choi H, Nah H, Lim HT, Kang D. Digital therapeutics using virtual reality-based visual perceptual learning for visual field defects in stroke: A double-blind randomized trial. Brain Behav 2024; 14:e3525. [PMID: 38773793 PMCID: PMC11109502 DOI: 10.1002/brb3.3525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 04/04/2024] [Accepted: 04/19/2024] [Indexed: 05/24/2024] Open
Abstract
INTRODUCTION Visual field defects (VFDs) represent a debilitating poststroke complication, characterized by unseen parts of the visual field. Visual perceptual learning (VPL), involving repetitive visual training in blind visual fields, may effectively restore visual field sensitivity in cortical blindness. This current multicenter, double-blind, randomized, controlled clinical trial investigated the efficacy and safety of VPL-based digital therapeutics (Nunap Vision [NV]) for treating poststroke VFDs. METHODS Stroke outpatients with VFDs (>6 months after stroke onset) were randomized into NV (defective field training) or Nunap Vision-Control (NV-C, central field training) groups. Both interventions provided visual perceptual training, consisting of orientation, rotation, and depth discrimination, through a virtual reality head-mounted display device 5 days a week for 12 weeks. The two groups received VFD assessments using Humphrey visual field (HVF) tests at baseline and 12-week follow-up. The final analysis included those completed the study (NV, n = 40; NV-C, n = 35). Efficacy measures included improved visual area (sensitivity ≥6 dB) and changes in the HVF scores during the 12-week period. RESULTS With a high compliance rate, NV and NV-C training improved the visual areas in the defective hemifield (>72 degrees2) and the whole field (>108 degrees2), which are clinically meaningful improvements despite no significant between-group differences. According to within-group analyses, mean total deviation scores in the defective hemifield improved after NV training (p = .03) but not after NV-C training (p = .12). CONCLUSIONS The current trial suggests that VPL-based digital therapeutics may induce clinically meaningful visual improvements in patients with poststroke VFDs. Yet, between-group differences in therapeutic efficacy were not found as NV-C training exhibited unexpected improvement comparable to NV training, possibly due to learning transfer effects.
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Affiliation(s)
- Eun Namgung
- Asan Institute for Life SciencesAsan Medical CenterSeoulSouth Korea
| | - Sun U. Kwon
- Department of Neurology, Asan Medical CenterUniversity of Ulsan College of MedicineSeoulSouth Korea
| | - Moon‐Ku Han
- Department of NeurologySeoul National University Bundang Hospital, Seoul National University College of MedicineSeongnamSouth Korea
| | - Gyeong‐Moon Kim
- Department of Neurology, Samsung Medical CenterSungkyunkwan University School of MedicineSeoulSouth Korea
| | - Hahn Young Kim
- Department of NeurologyKonkuk University Medical Center, Konkuk University College of MedicineSeoulSouth Korea
| | - Kwang‐Yeol Park
- Department of NeurologyChung‐Ang University Hospital, Chung‐Ang University College of MedicineSeoulSouth Korea
| | | | | | - Hyun‐Wook Nah
- Department of NeurologyChungnam National University Sejong Hospital, Chungnam National University College of MedicineSejongSouth Korea
| | - Hyun Taek Lim
- Department of Ophthalmology, Asan Medical CenterUniversity of Ulsan College of MedicineSeoulSouth Korea
| | - Dong‐Wha Kang
- Department of Neurology, Asan Medical CenterUniversity of Ulsan College of MedicineSeoulSouth Korea
- Nunaps Inc.SeoulSouth Korea
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Fahrenthold BK, Cavanaugh MR, Tamhankar M, Lam BL, Feldon SE, Johnson BA, Huxlin KR. Training in Cortically Blinded Fields Appears to Confer Patient-Specific Benefit Against Retinal Thinning. Invest Ophthalmol Vis Sci 2024; 65:29. [PMID: 38635245 PMCID: PMC11033601 DOI: 10.1167/iovs.65.4.29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 03/06/2024] [Indexed: 04/19/2024] Open
Abstract
Purpose Damage to the adult primary visual cortex (V1) causes vision loss in the contralateral hemifield, initiating a process of transsynaptic retrograde degeneration (TRD). Here, we examined retinal correlates of TRD using a new metric to account for global changes in inner retinal thickness and asked if perceptual training in the intact or blind field impacts its progression. Methods We performed a meta-analysis of optical coherence tomography data in 48 participants with unilateral V1 stroke and homonymous visual defects who completed clinical trial NCT03350919. After measuring the thickness of the macular ganglion cell and inner plexiform layer (GCL-IPL) and the peripapillary retinal nerve fiber layer (RNFL), we computed individual laterality indices (LI) at baseline and after ∼6 months of daily motion discrimination training in the intact or blind field. Increasingly positive LI denoted greater layer thinning in retinal regions affected versus unaffected by the cortical damage. Results Pretraining, the affected GCL-IPL and RNFL were thinner than their unaffected counterparts, generating LI values positively correlated with time since stroke. Participants trained in their intact field exhibited increased LIGCL-IPL. Those trained in their blind field had no significant change in LIGCL-IPL. LIRNFL did not change in either group. Conclusions Relative shrinkage of the affected versus unaffected macular GCL-IPL can be reliably measured at an individual level and increases with time post-V1 stroke. Relative thinning progressed during intact-field training but appeared to be halted by training within the blind field, suggesting a potentially neuroprotective effect of this simple behavioral intervention.
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Affiliation(s)
- Berkeley K. Fahrenthold
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, New York, United States
| | - Matthew R. Cavanaugh
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, New York, United States
| | - Madhura Tamhankar
- Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Byron L. Lam
- Bascom Palmer Eye Institute, University of Miami, Miami, Florida, United States
| | - Steven E. Feldon
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, New York, United States
| | - Brent A. Johnson
- Department of Biostatistics and Computational Biology, University of Rochester, Rochester, New York, United States
| | - Krystel R. Huxlin
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, New York, United States
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Yang (杨菁艺) J, Saionz EL, Cavanaugh MR, Fahrenthold BK, Melnick MD, Tadin D, Briggs F, Carrasco M, Huxlin KR. Limited restoration of contrast sensitivity with training after V1 damage in humans. eNeuro 2024; 11:ENEURO.0020-24.2024. [PMID: 38395611 PMCID: PMC10941636 DOI: 10.1523/eneuro.0020-24.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 02/15/2024] [Indexed: 02/25/2024] Open
Abstract
Stroke damage to the primary visual cortex (V1) causes severe visual deficits, which benefit from perceptual retraining. However, whereas training with high-contrast stimuli can locally restore orientation and motion direction discrimination abilities at trained locations, it only partially restores luminance contrast sensitivity (CS). Recent work revealed that high-contrast discrimination abilities may be preserved in the blind field of some patients early after stroke. Here, we asked if CS for orientation and direction discrimination is similarly preserved inside the blind field, to what extent, and whether it could benefit from a visual training intervention. Thirteen subacute patients (<3 months post-V1-stroke) and 12 chronic patients (>6 months post-V1-stroke) were pre-tested, then trained to discriminate either orientation or motion direction of Gabor patches of progressively lower contrasts as their performance improved. At baseline, more subacute than chronic participants could correctly discriminate the orientation of high-contrast Gabors in their blind field, but all failed to perform this task at lower contrasts, even when 10Hz flicker or motion direction were added. Training improved CS in a greater portion of subacute than chronic participants, but no-one attained normal CS, even when stimuli contained flicker or motion. We conclude that, unlike the near-complete training-induced restoration of high-contrast orientation and motion direction discrimination abilities, V1 damage in adulthood may severely limit the residual visual system's ability to regain normal CS. Our results support the notion that CS involves different neural substrates and computations than those required for orientation and direction discrimination in V1-damaged visual systems.Significance statement Stroke-induced V1 damage in adult humans induces a rapid and severe impairment of contrast sensitivity for orientation and motion direction discrimination in the affected hemifield, although discrimination of high-contrast stimuli can persist for several months. Adaptive training with Gabor patches of progressively lower contrasts improves contrast sensitivity for both orientation and motion discriminations in the blind-field of subacute (<3 months post-stroke) and chronic (>6 months post-stroke) participants; however, it fails to restore normal contrast sensitivity. Nonetheless, more subacute than chronic stroke participants benefit from such training, particularly when discriminating the orientation of static, non-flickering targets. Thus, contrast sensitivity appears critically dependent on processing within V1, with perceptual training displaying limited potential to fully restore it after V1 damage.
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Affiliation(s)
- Jingyi Yang (杨菁艺)
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Elizabeth L. Saionz
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Matthew R. Cavanaugh
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Berkeley K. Fahrenthold
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Michael D. Melnick
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
| | - Duje Tadin
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
| | - Farran Briggs
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
| | - Marisa Carrasco
- Department of Psychology and Center for Neural Science, New York University, New York, New York 10003
| | - Krystel R. Huxlin
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
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Namgung E, Kim YH, Lee EJ, Sasaki Y, Watanabe T, Kang DW. Functional connectivity interacts with visual perceptual learning for visual field recovery in chronic stroke. Sci Rep 2024; 14:3247. [PMID: 38332042 PMCID: PMC10853510 DOI: 10.1038/s41598-024-52778-x] [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: 09/27/2023] [Accepted: 01/23/2024] [Indexed: 02/10/2024] Open
Abstract
A reciprocal relationship between perceptual learning and functional brain changes towards perceptual learning effectiveness has been demonstrated previously; however, the underlying neural correlates remain unclear. Further, visual perceptual learning (VPL) is implicated in visual field defect (VFD) recovery following chronic stroke. We investigated resting-state functional connectivity (RSFC) in the visual cortices associated with mean total deviation (MTD) scores for VPL-induced VFD recovery in chronic stroke. Patients with VFD due to chronic ischemic stroke in the visual cortex received 24 VPL training sessions over 2 months, which is a dual discrimination task of orientation and letters. At baseline and two months later, the RSFC in the ipsilesional, interhemispheric, and contralesional visual cortices and MTD scores in the affected hemi-field were assessed. Interhemispheric visual RSFC at baseline showed the strongest correlation with MTD scores post-2-month VPL training. Notably, only the subgroup with high baseline interhemispheric visual RSFC showed significant VFD improvement following the VPL training. The interactions between the interhemispheric visual RSFC at baseline and VPL led to improvement in MTD scores and largely influenced the degree of VFD recovery. The interhemispheric visual RSFC at baseline could be a promising brain biomarker for the effectiveness of VPL-induced VFD recovery.
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Affiliation(s)
- Eun Namgung
- Asan Institute for Life Sciences, Asan Medical Center, Seoul, South Korea
| | | | - Eun-Jae Lee
- Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - Yuka Sasaki
- Department of Cognitive, Linguistic and Psychological Sciences, Brown University, Providence, USA
| | - Takeo Watanabe
- Department of Cognitive, Linguistic and Psychological Sciences, Brown University, Providence, USA
| | - Dong-Wha Kang
- Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
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Fahrenthold BK, Cavanaugh MR, Tamhankar M, Lam BL, Feldon SE, Johnson BA, Huxlin KR. Training in cortically-blind fields confers patient-specific benefit against retinal thinning after occipital stroke. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.12.19.23298260. [PMID: 38196617 PMCID: PMC10775322 DOI: 10.1101/2023.12.19.23298260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Purpose Damage to the adult primary visual cortex (V1) causes vision loss in the contralateral hemifield, initiating a process of trans-synaptic retrograde degeneration (TRD). Here, we examined retinal correlates of TRD using a new metric to account for global changes in inner retinal thickness, and asked if perceptual training in the intact or blind field impacts its progression. Methods We performed a meta-analysis of optical coherence tomography (OCT) data in 48 participants with unilateral V1 stroke and homonymous visual defects, who completed clinical trial NCT03350919. After measuring the thickness of the macular ganglion cell and inner plexiform layers (GCL-IPL), and the peripapillary retinal nerve fiber layer (RNFL), we computed individual laterality indices (LI) at baseline and after ~6 months of daily motion discrimination training in the intact- or blind-field. Increasingly positive LI denoted greater layer thinning in retinal regions affected versus unaffected by the cortical damage. Results Pre-training, the affected GCL-IPL and RNFL were thinner than their unaffected counterparts, generating LI values positively correlated with time since stroke. Participants trained in their intact-field exhibited increased LIGCL-IPL. Those trained in their blind-field had no significant change in LIGCL-IPL. LIRNFL did not change in either group. Conclusions Relative shrinkage of the affected versus unaffected macular GCL-IPL can be reliably measured at an individual level and increases with time post-V1 stroke. Relative thinning progressed during intact-field training, but appeared to be halted by training within the blind field, suggesting a potentially neuroprotective effect of this simple behavioral intervention.
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Affiliation(s)
- Berkeley K. Fahrenthold
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, USA
| | - Matthew R. Cavanaugh
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, USA
| | - Madhura Tamhankar
- Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA, USA
| | - Byron L. Lam
- Bascom Palmer Eye Institute, University of Miami, Miami, FL, USA
| | - Steven E. Feldon
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, USA
| | - Brent A. Johnson
- Department of Biostatistics and Computational Biology, University of Rochester, Rochester, NY, USA
| | - Krystel R. Huxlin
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, USA
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Schmid D, Hesse C, Schenk T. The redundant target paradigm and its use as a blindsight-test: A meta-analytic study. Cortex 2023; 169:326-352. [PMID: 37981442 DOI: 10.1016/j.cortex.2023.08.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 08/04/2023] [Accepted: 08/30/2023] [Indexed: 11/21/2023]
Abstract
The redundant target effect (RTE) is the well-known effect whereby a single target is detected faster when a second, redundant target is presented simultaneously. The RTE was shown in different experimental designs and applied in various clinical contexts. However, there are also studies showing non-effects or effects in the opposite direction. Our meta-analysis aims to investigate the replicability of the RTE. Herein, we focused on the clinical context within which the RTE has been applied most often and for which it gained particular prominence: The research on blindsight and other forms of residual vision in patients with damage to the neuronal visual system. The application of the RTE in clinical contexts assumes that whenever vision is present, an RTE will be found. Put differently, the RTE as a tool to uncover residual vision presumes that the RTE is a consistent feature of vision in the healthy population. We found a significant summary effect size of the RTE in healthy participants. The effect size depended on certain experimental features: task type, target configuration in the redundant condition, and how reaction times were computed in the single condition. A specific feature combination is typically used in blindsight research. Analyzing studies with this feature combination revealed a significant summary effect size in healthy participants predicting positive RTEs for future studies. A power-analysis revealed a required sample size of 14 participants to obtain an RTE with high reliability. However, the required sample size is rarely reached in blindsight research. Rather, blindsight research is mostly based on single-case studies. In summary, the RTE is a robust effect on group level but does not occur in every single individual. This means failure to obtain an RTE in a single patient should not be interpreted as evidence for the absence of residual vision in this patient.
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Affiliation(s)
- Doris Schmid
- Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.
| | - Constanze Hesse
- School of Psychology, University of Aberdeen, King's College, Aberdeen, United Kingdom.
| | - Thomas Schenk
- Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.
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Li Y, Harrison J, Headrick S, Craigie M, Ooi L. Visual Field Recovery in Ischemic Stroke Associated With Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy Syndrome. J Neuroophthalmol 2023; 43:e271-e273. [PMID: 35427296 DOI: 10.1097/wno.0000000000001574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Ye Li
- Departments of Ophthalmology (YL, JH, LO), Neurology (SH), and Radiology (MC), Princess Alexandra Hospital, Brisbane, Australia
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Yang J, Saionz EL, Cavanaugh MR, Fahrenthold BK, Melnick MD, Tadin D, Briggs F, Carrasco M, Huxlin KR. Contrast sensitivity: a fundamental limit to vision restoration after V1 damage. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.08.31.23294827. [PMID: 37693553 PMCID: PMC10491352 DOI: 10.1101/2023.08.31.23294827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Stroke damage to the primary visual cortex (V1) causes severe visual deficits, which benefit from perceptual retraining. However, whereas training with high-contrast stimuli can locally restore orientation and direction discrimination abilities at trained locations, it only partially restores luminance contrast sensitivity (CS). Recent work revealed that high-contrast discrimination abilities may be preserved in the blind field of some patients early after stroke. Here, we asked if CS for orientation and direction discrimination is similarly preserved inside the blind field, to what extent, and whether it could benefit from a visual training intervention. Thirteen subacute (<3 months post-V1-stroke) and 12 chronic (>6 months post-V1-stroke) participants were pre-tested, then trained to discriminate either orientation or motion direction of Gabor patches of progressively lower contrasts. At baseline, more subacute than chronic participants could correctly discriminate the orientation of high-contrast Gabors in their blind field, but all failed to perform this task at lower contrasts, even when 10Hz flicker or motion direction were added. Training improved CS in a greater portion of subacute than chronic participants, but no-one attained normal CS, even when stimuli contained flicker or motion. We conclude that, unlike the near-complete training-induced restoration of high-contrast orientation and direction discrimination, there is limited capacity for restoring CS after V1 damage in adulthood. Our results suggest that CS involves different neural substrates and computations than those required for orientation and direction discrimination in V1-damaged visual systems.
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Affiliation(s)
- Jingyi Yang
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Elizabeth L. Saionz
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Matthew R. Cavanaugh
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Berkeley K. Fahrenthold
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Michael D. Melnick
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Duje Tadin
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Farran Briggs
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York 14642
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
- Center for Visual Science, University of Rochester, Rochester, New York 14627
| | - Marisa Carrasco
- Department of Psychology and Center for Neural Science, New York University, NY, NY 10003
| | - Krystel R. Huxlin
- Flaum Eye Institute, University of Rochester Medical Center, Rochester, New York 14642
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York 14642
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, New York 14627
- Center for Visual Science, University of Rochester, Rochester, New York 14627
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Bevilacqua M, Huxlin KR, Hummel FC, Raffin E. Pathway and directional specificity of Hebbian plasticity in the cortical visual motion processing network. iScience 2023; 26:107064. [PMID: 37408682 PMCID: PMC10319215 DOI: 10.1016/j.isci.2023.107064] [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: 06/23/2022] [Revised: 02/14/2023] [Accepted: 06/02/2023] [Indexed: 07/07/2023] Open
Abstract
Cortico-cortical paired associative stimulation (ccPAS), which repeatedly pairs single-pulse transcranial magnetic stimulation (TMS) over two distant brain regions, is thought to modulate synaptic plasticity. We explored its spatial selectivity (pathway and direction specificity) and its nature (oscillatory signature and perceptual consequences) when applied along the ascending (Forward) and descending (Backward) motion discrimination pathway. We found unspecific connectivity increases in bottom-up inputs in the low gamma band, probably reflecting visual task exposure. A clear distinction in information transfer occurred in the re-entrant alpha signals, which were only modulated by Backward-ccPAS, and predictive of visual improvements in healthy participants. These results suggest a causal involvement of the re-entrant MT-to-V1 low-frequency inputs in motion discrimination and integration in healthy participants. Modulating re-entrant input activity could provide single-subject prediction scenarios for visual recovery. Visual recovery might indeed partly rely on these residual inputs projecting to spared V1 neurons.
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Affiliation(s)
- Michele Bevilacqua
- Defitech Chair in Clinical Neuroengineering, Neuro-X Institute (NRX) and Brain Mind Institute, EPFL, Geneva, Switzerland
- Defitech Chair in Clinical Neuroengineering, Neuro-X Institute (NRX) and Brain Mind Institute, Clinique Romande de Readaptation (CRR), EPFL Valais, Sion, Switzerland
| | - Krystel R. Huxlin
- The Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, USA
| | - Friedhelm C. Hummel
- Defitech Chair in Clinical Neuroengineering, Neuro-X Institute (NRX) and Brain Mind Institute, EPFL, Geneva, Switzerland
- Defitech Chair in Clinical Neuroengineering, Neuro-X Institute (NRX) and Brain Mind Institute, Clinique Romande de Readaptation (CRR), EPFL Valais, Sion, Switzerland
- Clinical Neuroscience, University of Geneva Medical School, Geneva, Switzerland
| | - Estelle Raffin
- Defitech Chair in Clinical Neuroengineering, Neuro-X Institute (NRX) and Brain Mind Institute, EPFL, Geneva, Switzerland
- Defitech Chair in Clinical Neuroengineering, Neuro-X Institute (NRX) and Brain Mind Institute, Clinique Romande de Readaptation (CRR), EPFL Valais, Sion, Switzerland
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Leitner MC, Ladek AM, Hutzler F, Reitsamer H, Hawelka S. Placebo effect after visual restitution training: no eye-tracking controlled perimetric improvement after visual border stimulation in late subacute and chronic visual field defects after stroke. Front Neurol 2023; 14:1114718. [PMID: 37456634 PMCID: PMC10339290 DOI: 10.3389/fneur.2023.1114718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 06/13/2023] [Indexed: 07/18/2023] Open
Abstract
Introduction A significant number of Restitution Training (RT) paradigms claim to ameliorate visual field loss after stroke by re-activating neuronal connections in the residual visual cortex due to repeated bright light-stimulation at the border of the blind and intact fields. However, the effectiveness of RT has been considered controversial both in science and clinical practice for years. The main points of the controversy are (1) the reliability of perimetric results which may be affected by compensatory eye movements and (2) heterogeneous samples consisting of patients with visual field defects and/or visuospatial neglect. Methods By means of our newly developed and validated Virtual Reality goggles Salzburg Visual Field Trainer (SVFT) 16 stroke patients performed RT on a regular basis for 5 months. By means of our newly developed and validated Eye Tracking Based Visual Field Analysis (EFA), we conducted a first-time full eye-movement-controlled perimetric pre-post intervention study. Additionally, patients subjectively rated the size of their intact visual field. Results Analysis showed that patients' mean self-assessment of their subjective visual field size indicated statistically significant improvement while, in contrast, objective eye tracking controlled perimetric results revealed no statistically significant effect. Discussion Bright-light detection RT at the blind-field border solely induced a placebo effect and did not lead to training-induced neuroplasticity in the visual cortex of the type needed to ameliorate the visual field size of stroke patients.
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Affiliation(s)
- Michael Christian Leitner
- Salzburg University of Applied Sciences, Salzburg, Austria
- Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria
- Department of Psychology, University of Salzburg, Salzburg, Austria
| | - Anja-Maria Ladek
- Research Program for Experimental Ophthalmology and Glaucoma Research, Department of Ophthalmology and Optometry, University Hospital of the Paracelsus Medical University Salzburg, Salzburg, Austria
- Department of Ophthalmology and Optometry, SALK, University Hospital of the Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Florian Hutzler
- Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria
- Department of Psychology, University of Salzburg, Salzburg, Austria
| | - Herbert Reitsamer
- Research Program for Experimental Ophthalmology and Glaucoma Research, Department of Ophthalmology and Optometry, University Hospital of the Paracelsus Medical University Salzburg, Salzburg, Austria
- Department of Ophthalmology and Optometry, SALK, University Hospital of the Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Stefan Hawelka
- Centre for Cognitive Neuroscience (CCNS), University of Salzburg, Salzburg, Austria
- Department of Psychology, University of Salzburg, Salzburg, Austria
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Takami A, Goya R, Aoyama C, Komiyama T, Kawajiri T, Shimegi S. Daily fluctuations in visual motion discriminability contribute to daily fluctuations in continuous visuomotor performance. Front Sports Act Living 2022; 4:1009763. [PMID: 36406773 PMCID: PMC9666672 DOI: 10.3389/fspor.2022.1009763] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 10/04/2022] [Indexed: 01/24/2023] Open
Abstract
In ball sports such as table tennis, in which a ball moving at high speed is hit, an athlete's brain needs to process the motion information of the ball, predict the arrival point, and form a motor command to direct the racket there. Therefore, day-to-day fluctuations in visuomotor performance may be ascribed to fluctuations in visual motion discriminability, but it is not clear how the two are related. To examine this point, university table tennis players performed a motion direction discrimination (MDD) task and continuous visuomotor (CVM) task over 10 days as an estimation of visual motion discriminability and visuomotor performance, respectively. In the MDD task, using a joystick, participants distinguished the direction of a global coherent motion of target dots moving in the same direction on a PC monitor from innumerable dots moving in random directions. In the CVM task, participants hit sequential targets moving fast from right to left on the PC monitor by operating the cursor on the left side of the monitor up and down using the prehensile force of their thumb and index finger. The scores in the MDD and CVM tasks fluctuated day by day and showed a significant and moderate correlation between the MDD task score for the visual field in which the participants captured the target in the CVM task and the CVM task score. This correlation was confirmed even with the target moving from left to right. The fluctuations in the onset latency and the endpoint position of the cursor movement approaching the target were correlated with those of the visual motion discriminability, suggesting the contribution of motion vision to the speed and accuracy of the visuomotor performance. Moreover, these relationships were prominent in veteran players. For table tennis athletes, especially experienced players, fluctuations in the visual motion discrimination performance in a visual field specific for capturing a ball may be responsible for the fluctuations in continuous visuomotor (striking) performance.
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Affiliation(s)
- Ayaka Takami
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Ryoma Goya
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan,Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan
| | - Chisa Aoyama
- Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Takaaki Komiyama
- Center for Education in Liberal Arts and Sciences, Osaka University, Osaka, Japan
| | | | - Satoshi Shimegi
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan,Center for Education in Liberal Arts and Sciences, Osaka University, Osaka, Japan,*Correspondence: Satoshi Shimegi
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12
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Kim Y, Im S, Oh J, Jung Y, Jun SY. Detection of post-stroke visual field loss by quantification of the retrogeniculate visual pathway. J Neurol Sci 2022; 439:120297. [DOI: 10.1016/j.jns.2022.120297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 04/28/2022] [Accepted: 05/22/2022] [Indexed: 11/28/2022]
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13
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Ye C, Kwapong WR, Tao W, Lu K, Pan R, Wang A, Liu J, Liu M, Wu B. Alterations of optic tract and retinal structure in patients after thalamic stroke. Front Aging Neurosci 2022; 14:942438. [PMID: 35966790 PMCID: PMC9363922 DOI: 10.3389/fnagi.2022.942438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 06/30/2022] [Indexed: 11/13/2022] Open
Abstract
ObjectivesTo investigate the association between degeneration of retinal structure and shrinkage of the optic tract in patients after thalamic stroke.Materials and methodsPatients with unilateral thalamic stroke were included. Structural magnetic resonance imaging (MRI) and optical coherence tomography (OCT) were performed to obtain parameters of optic tract shrinkage (lateral index) and retina structural thickness (retinal nerve fiber layer, RNFL; peripapillary retinal nerve fiber layer, pRNFL; ganglion cell-inner plexiform layer, GCIP), respectively. Visual acuity (VA) examination under illumination was conducted using Snellen charts and then converted to the logarithm of the minimum angle of resolution (LogMAR). We investigated the association between LI and OCT parameters and their relationships with VA.ResultsA total of 33 patients and 23 age-sex matched stroke-free healthy controls were enrolled. Patients with thalamic stroke showed altered LI compared with control participants (P = 0.011) and a significantly increased value of LI in the subgroup of disease duration more than 6 months (P = 0.004). In these patients, LI were significantly associated with pRNFL thickness (β = 0.349, 95% confidence interval [CI]: 0.134–0.564, P = 0.002) after adjusting for confounders (age, sex, hypertension, diabetes, dyslipidemia, and lesion volume). LI and pRNFL were both significantly associated with VA in all patients (LI: β = −0.275, 95% CI: −0.539 to −0.011, P = 0.041; pRNFL: β = −0.023, 95% CI: −0.046 to −0.001, P = 0.040) and in subgroup of disease duration more than 6 months (LI: β = −0.290, 95% CI: −0.469 to −0.111, P = 0.002; pRNFL: β = −0.041, 95% CI: −0.065 to −0.017, P = 0.003).ConclusionShrinkage of the optic tract can be detected in patients with thalamic stroke, especially after 6 months of stroke onset. In these patients, the extent of optic tract atrophy is associated with pRNFL thickness, and they are both related to visual acuity changes.
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Kwon S, Fahrenthold BK, Cavanaugh MR, Huxlin KR, Mitchell JF. Perceptual restoration fails to recover unconscious processing for smooth eye movements after occipital stroke. eLife 2022; 11:67573. [PMID: 35730931 PMCID: PMC9255960 DOI: 10.7554/elife.67573] [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: 02/15/2021] [Accepted: 06/21/2022] [Indexed: 11/28/2022] Open
Abstract
The visual pathways that guide actions do not necessarily mediate conscious perception. Patients with primary visual cortex (V1) damage lose conscious perception but often retain unconscious abilities (e.g. blindsight). Here, we asked if saccade accuracy and post-saccadic following responses (PFRs) that automatically track target motion upon saccade landing are retained when conscious perception is lost. We contrasted these behaviors in the blind and intact fields of 11 chronic V1-stroke patients, and in 8 visually intact controls. Saccade accuracy was relatively normal in all cases. Stroke patients also had normal PFR in their intact fields, but no PFR in their blind fields. Thus, V1 damage did not spare the unconscious visual processing necessary for automatic, post-saccadic smooth eye movements. Importantly, visual training that recovered motion perception in the blind field did not restore the PFR, suggesting a clear dissociation between pathways mediating perceptual restoration and automatic actions in the V1-damaged visual system.
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Affiliation(s)
- Sunwoo Kwon
- Herbert Wertheim School of Optometry and Vision Science, University of California, Berkeley, Berkeley, United States
| | | | - Matthew R Cavanaugh
- Center for Visual Science, University of Rochester, Rochester, United States
| | - Krystel R Huxlin
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, United States
| | - Jude F Mitchell
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, United States
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15
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Schmid D, Schneider S, Schenk T. How to test blindsight without light-scatter artefacts? Neuropsychologia 2022; 173:108308. [PMID: 35716799 DOI: 10.1016/j.neuropsychologia.2022.108308] [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: 11/09/2021] [Revised: 06/01/2022] [Accepted: 06/13/2022] [Indexed: 11/27/2022]
Abstract
Light-scatter artefacts are a methodological problem in testing residual visual capacities (RVCs), for instance blindsight, in patients with homonymous visual field defects (HVFDs). The term light-scatter artefact describes the phenomenon that light from targets directed towards the HVFD can stray into the sighted visual field. This might enable an observer to respond correctly to information directed at her blind field despite the fact that she is unable to process that information in the blind field itself. In this manuscript, we present a review of the relevance of light-scatter in visual neuroscience, discuss factors that influence the impact of light-scatter and evaluate means to test for light-scatter artefacts. Furthermore, we present findings from an empirical study that was aimed at developing tests for RVCs that are free of light-scatter artefacts. Previous studies on light scatter only used small sample sizes and equipment that is no longer in use. Hence, their results cannot be generalized to future experiments making it necessary to run laborious light-scatter tests for every new study on RVCs. To avoid this, we hereby start a pool of stimuli and paradigms which demonstrably do not elicit light-scatter artefacts. To this end, we investigated 21 healthy young participants in three frequently used RVC-paradigms: (1) temporal 2AFC task, (2) movement direction discrimination, and (3) redundant target paradigm. For each paradigm, we applied the blind-spot method. But first, we had to establish that our testing paradigm was sufficiently sensitive to detect light-scatter artefacts. For this, we used conditions that are known to produce strong light scatter and a paradigm that is very sensitive to such effects. Specifically, we presented white targets on a black background in a dark room. The stimuli were presented to observers' blind spot. To check for light-scatter artefacts, we used a target-detection task in a temporal 2AFC format. We obtained clear light-scatter artefacts. Participants produced reliably above-chance detection performance under these conditions. The other two luminance conditions, measured in an illuminated room, did not produce light-scatter artefacts. Accuracy in the temporal 2AFC task was at chance level for white targets on a grey background at the blind-spot position. Additionally, black targets on a grey background avoided light-scatter artefacts in all three RVC-paradigms. In future, researchers can apply these stimulus and illumination conditions when using one of the three above paradigms in their studies. Using these conditions, they will be able to avoid light-scatter artefacts without having to perform their own blind-spot tests.
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Affiliation(s)
- Doris Schmid
- Department of Psychology, Ludwig-Maximilians-Universität München, Leopoldstr. 13, 80802, Munich, Germany.
| | - Sebastian Schneider
- Department of Psychology, Ludwig-Maximilians-Universität München, Leopoldstr. 13, 80802, Munich, Germany.
| | - Thomas Schenk
- Department of Psychology, Ludwig-Maximilians-Universität München, Leopoldstr. 13, 80802, Munich, Germany.
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16
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Characterization of Macular Structural and Microvascular Changes in Thalamic Infarction Patients: A Swept-Source Optical Coherence Tomography-Angiography Study. Brain Sci 2022; 12:brainsci12050518. [PMID: 35624906 PMCID: PMC9139152 DOI: 10.3390/brainsci12050518] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 04/02/2022] [Accepted: 04/17/2022] [Indexed: 02/05/2023] Open
Abstract
Background: The retina and brain share similar neuronal and microvascular features. We aimed to investigate the retinal thickness and microvasculature in patients with thalamic infarcts compared with control participants. Material and methods: Swept-source optical coherence tomography (SS-OCT) was used to image the macular thickness (retinal nerve fiber layer, RNFL; ganglion cell-inner plexiform layer, GCIP), while OCT angiography was used to image the microvasculature (superficial vascular plexus, SVP; intermediate capillary plexus, ICP; deep capillary plexus, DCP). Inbuilt software was used to measure the macular thickness (µm) and microvascular density (%). Lesion volumes were quantitively assessed based on structural magnetic resonance images. Results: A total of 35 patients with unilateral thalamic infarction and 31 age−sex-matched controls were enrolled. Compared with control participants, thalamic infarction patients showed a significantly thinner thickness of RNFL (p < 0.01) and GCIP (p = 0.02), and a lower density of SVP (p = 0.001) and ICP (p = 0.022). In the group of patients, ipsilateral eyes showed significant reductions in SVP (p = 0.033), RNFL (p = 0.01) and GCIP (p = 0.043). When divided into three groups based on disease duration (<1 month, 1−6 months, and >6 months), no significant differences were found among these groups. After adjusting for confounders, SVP, ICP, DCP, RNFL, and GCIP were significantly correlated with lesion volume in patients. Conclusions: Thalamic infarction patients showed significant macular structure and microvasculature changes. Lesion size was significantly correlated with these alterations. These findings may be useful for further research into the clinical utility of retinal imaging in stroke patients, especially those with damage to the visual pathway.
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17
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Cavanaugh MR, Tadin D, Carrasco M, Huxlin KR. Benefits of Endogenous Spatial Attention During Visual Double-Training in Cortically-Blinded Fields. Front Neurosci 2022; 16:771623. [PMID: 35495043 PMCID: PMC9046589 DOI: 10.3389/fnins.2022.771623] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 03/08/2022] [Indexed: 12/12/2022] Open
Abstract
Recovery of visual discrimination thresholds inside cortically-blinded (CB) fields is most commonly attained at a single, trained location at a time, with iterative progress deeper into the blind field as performance improves over several months. As such, training is slow, inefficient, burdensome, and often frustrating for patients. Here, we investigated whether double-location training, coupled with a covert spatial-attention (SA) pre-cue, could improve the efficiency of training. Nine CB participants completed a randomized, training assignment with either a spatial attention or neutral pre-cue. All trained for a similar length of time on a fine direction discrimination task at two blind field locations simultaneously. Training stimuli and tasks for both cohorts were identical, save for the presence of a central pre-cue, to manipulate endogenous (voluntary) SA, or a Neutral pre-cue. Participants in the SA training cohort demonstrated marked improvements in direction discrimination thresholds, albeit not to normal/intact-field levels; participants in the Neutral training cohort remained impaired. Thus, double-training within cortically blind fields, when coupled with SA pre-cues can significantly improve direction discrimination thresholds at two locations simultaneously, offering a new method to improve performance and reduce the training burden for CB patients. Double-training without SA pre-cues revealed a hitherto unrecognized limitation of cortically-blind visual systems’ ability to improve while processing two stimuli simultaneously. These data could potentially explain why exposure to the typically complex visual environments encountered in everyday life is insufficient to induce visual recovery in CB patients. It is hoped that these new insights will direct both research and therapeutic developments toward methods that can attain better, faster recovery of vision in CB fields.
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Affiliation(s)
- Matthew R. Cavanaugh
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, United States
| | - Duje Tadin
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, United States
- Department of Brain and Cognitive Sciences and Center for Visual Science, University of Rochester, Rochester, NY, United States
| | - Marisa Carrasco
- Department of Psychology and Center for Neural Science, New York University, New York, NY, United States
| | - Krystel R. Huxlin
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY, United States
- Department of Brain and Cognitive Sciences and Center for Visual Science, University of Rochester, Rochester, NY, United States
- *Correspondence: Krystel R. Huxlin,
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18
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He Q, Gan S. Neural Mechanisms of Visual Field Recovery after Perceptual Training in Cortical Blindness. J Neurosci 2022; 42:1886-1887. [PMID: 35264430 PMCID: PMC8916751 DOI: 10.1523/jneurosci.1953-21.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 01/08/2022] [Accepted: 01/12/2022] [Indexed: 11/21/2022] Open
Affiliation(s)
- Qing He
- School of Psychological and Cognitive Sciences, Peking University, Beijing, 100871, China
| | - Shuoqiu Gan
- Department of Medical Imaging, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
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19
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Rina A, Papanikolaou A, Zong X, Papageorgiou DT, Keliris GA, Smirnakis SM. Visual Motion Coherence Responses in Human Visual Cortex. Front Neurosci 2022; 16:719250. [PMID: 35310109 PMCID: PMC8924467 DOI: 10.3389/fnins.2022.719250] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 01/17/2022] [Indexed: 01/24/2023] Open
Abstract
Random dot kinematograms (RDKs) have recently been used to train subjects with cortical scotomas to perform direction of motion discrimination, partially restoring visual motion perception. To study the recovery of visual perception, it is important to understand how visual areas in normal subjects and subjects with cortical scotomas respond to RDK stimuli. Studies in normal subjects have shown that blood oxygen level-dependent (BOLD) responses in human area hV5/MT+ increase monotonically with coherence, in general agreement with electrophysiology studies in primates. However, RDK responses in prior studies were obtained while the subject was performing fixation, not a motion discrimination condition. Furthermore, BOLD responses were gauged against a baseline condition of uniform illumination or static dots, potentially decreasing the specificity of responses for the spatial integration of local motion signals (motion coherence). Here, we revisit this question starting from a baseline RDK condition of no coherence, thereby isolating the component of BOLD response due specifically to the spatial integration of local motion signals. In agreement with prior studies, we found that responses in the area hV5/MT+ of healthy subjects were monotonically increasing when subjects fixated without performing a motion discrimination task. In contrast, when subjects were performing an RDK direction of motion discrimination task, responses in the area hV5/MT+ remained flat, changing minimally, if at all, as a function of motion coherence. A similar pattern of responses was seen in the area hV5/MT+ of subjects with dense cortical scotomas performing direction of motion discrimination for RDKs presented inside the scotoma. Passive RDK presentation within the scotoma elicited no significant hV5/MT+ responses. These observations shed further light on how visual cortex responses behave as a function of motion coherence, helping to prepare the ground for future studies using these methods to study visual system recovery after injury.
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Affiliation(s)
- Andriani Rina
- Department of Neurology Brigham and Women’s Hospital and Jamaica Plain Veterans Administration Hospital, Harvard Medical School, Boston, MA, United States
- Visual and Cognitive Neuroscience, Faculty of Science, University of Tübingen, Tuebingen, Germany
| | - Amalia Papanikolaou
- Department of Experimental Psychology, Institute of Behavioral Neuroscience, University College London, London, United Kingdom
| | - Xiaopeng Zong
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Dorina T. Papageorgiou
- Department of Physical Medicine and Rehabilitation, Neuroscience, Psychiatry Baylor College of Medicine, Houston, TX, United States
- Department of Electrical and Computer Engineering, Neuroengineering Research Initiative and Applied Physics, Rice University, Houston, TX, United States
| | - Georgios A. Keliris
- Bio-Imaging Lab, University of Antwerp, Antwerp, Belgium
- Max-Planck Institute for Biological Cybernetics, Physiology of Cognitive Processes, Tübingen, Germany
| | - Stelios M. Smirnakis
- Department of Neurology Brigham and Women’s Hospital and Jamaica Plain Veterans Administration Hospital, Harvard Medical School, Boston, MA, United States
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20
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Awada A, Bakhtiari S, Legault C, Odier C, Pack CC. Training with optic flow stimuli promotes recovery in cortical blindness. Restor Neurol Neurosci 2022; 40:1-16. [PMID: 35213337 DOI: 10.3233/rnn-211223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Cortical blindness is a form of severe vision loss that is caused by damage to the primary visual cortex (V1) or its afferents. This condition has devastating effects on quality of life and independence. While there are few treatments currently available, accumulating evidence shows that certain visual functions can be restored with appropriate perceptual training: Stimulus sensitivity can be increased within portions of the blind visual field. However, this increased sensitivity often remains highly specific to the trained stimulus, limiting the overall improvement in visual function. OBJECTIVE Recent advances in the field of perceptual learning show that such specificity can be overcome with training paradigms that leverage the properties of higher-level visual cortical structures, which have greater capacity to generalize across stimulus positions and features. This targeting can be accomplished by using more complex training stimuli that elicit robust responses in these visual structures. METHODS We trained cortically blind subjects with a complex optic flow motion stimulus that was presented in a location of their blind field. Participants were instructed to train with the stimulus at home for approximately 30 minutes per day. Once performance plateaued, the stimulus was moved deeper into the blind field. A battery of pre- and post-training measures, with careful eye tracking, was performed to quantify the improvements. RESULTS We show that 1) optic flow motion discrimination can be relearned in cortically blind fields; 2) training with an optic flow stimulus can lead to improvements that transfer to different tasks and untrained locations; and 3) such training leads to a significant expansion of the visual field. The observed expansion of the visual field was present even when eye movements were carefully controlled. Finally, we show that regular training is critical for improved visual function, as sporadic training reduced the benefits of training, even when the total numbers of training sessions were equated. CONCLUSIONS These findings are consistent with the hypothesis that complex training stimuli can improve outcomes in cortical blindness, provided that patients adhere to a regular training regimen. Nevertheless, such interventions remain limited in their ability to restore functional vision.
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Affiliation(s)
- Asmara Awada
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Shahab Bakhtiari
- Department of Computer Science, McGill University, Montreal, Canada
| | - Catherine Legault
- McGill University Health Center (MUHC), Montreal, Canada.,Montreal Neurological Institute and Hospital, Montreal, Canada
| | - Celine Odier
- Neurovascular Health Program, Department of Medicine (Neurology), Centre Hospitalier de l'Universite de Montreal, Montreal, Canada
| | - Christopher C Pack
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
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21
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Remodeling of lateral geniculate nucleus projections to extrastriate area MT following long-term lesions of striate cortex. Proc Natl Acad Sci U S A 2022; 119:2117137119. [PMID: 35058366 PMCID: PMC8794847 DOI: 10.1073/pnas.2117137119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2021] [Indexed: 01/04/2023] Open
Abstract
Lesions of the primary visual area (V1) in primates cause blindness by severing the main pathway which brings information from the thalamus to the cortex. However, some visual abilities remain, which are hypothesized to be mediated by thalamic neurons that innervate surviving areas such as the middle temporal (MT) cortex. We found that V1 lesions trigger long-term plasticity in the connections between the thalamus and cortex, including the emergence of a pathway that brings information to MT from cell populations that would normally project to V1. These results reveal potential targets for rehabilitation strategies to ameliorate the consequences of cortical blindness. Here, we report on a previously unknown form of thalamocortical plasticity observed following lesions of the primary visual area (V1) in marmoset monkeys. In primates, lateral geniculate nucleus (LGN) neurons form parallel pathways to the cortex, which are characterized by the expression of different calcium-binding proteins. LGN projections to the middle temporal (MT) area only originate in the koniocellular layers, where many neurons express calbindin. In contrast, projections to V1 also originate in the magnocellular and parvocellular layers, where neurons express parvalbumin but not calbindin. Our results demonstrate that this specificity is disrupted following long-term (1 to 3 y) unilateral V1 lesions, indicating active rearrangement of the geniculocortical circuit. In lesioned animals, retrograde tracing revealed MT-projecting neurons scattered throughout the lesion projection zone (LPZ, the sector of the LGN that underwent retrograde degeneration following a V1 lesion). Many of the MT-projecting neurons had large cell bodies and were located outside the koniocellular layers. Furthermore, we found that a large percentage of magno- and parvocellular neurons expressed calbindin in addition to the expected parvalbumin expression and that this coexpression was present in many of the MT-projecting neurons within the LPZ. These results demonstrate that V1 lesions trigger neurochemical and structural remodeling of the geniculo-extrastriate pathway, leading to the emergence of nonkoniocellular input to MT. This has potential implications for our understanding of the neurobiological bases of the residual visual abilities that survive V1 lesions, including motion perception and blindsight, and reveals targets for rehabilitation strategies to ameliorate the consequences of cortical blindness.
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22
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Rehabilitation of visual perception in cortical blindness. HANDBOOK OF CLINICAL NEUROLOGY 2022; 184:357-373. [PMID: 35034749 DOI: 10.1016/b978-0-12-819410-2.00030-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Blindness is a common sequela after stroke affecting the primary visual cortex, presenting as a contralesional, homonymous, visual field cut. This can occur unilaterally or, less commonly, bilaterally. While it has been widely assumed that after a brief period of spontaneous improvement, vision loss becomes stable and permanent, accumulating data show that visual training can recover some of the vision loss, even long after the stroke. Here, we review the different approaches to rehabilitation employed in adult-onset cortical blindness (CB), focusing on visual restoration methods. Most of this work was conducted in chronic stroke patients, partially restoring visual discrimination and luminance detection. However, to achieve this, patients had to train for extended periods (usually many months), and the vision restored was not entirely normal. Several adjuvants to training such as noninvasive, transcranial brain stimulation, and pharmacology are starting to be investigated for their potential to increase the efficacy of training in CB patients. However, these approaches are still exploratory and require considerably more research before being adopted. Nonetheless, having established that the adult visual system retains the capacity for restorative plasticity, attention recently turned toward the subacute poststroke period. Drawing inspiration from sensorimotor stroke rehabilitation, visual training was recently attempted for the first time in subacute poststroke patients. It improved vision faster, over larger portions of the blind field, and for a larger number of visual discrimination abilities than identical training initiated more than 6 months poststroke (i.e., in the chronic period). In conclusion, evidence now suggests that visual neuroplasticity after occipital stroke can be reliably recruited by a range of visual training approaches. In addition, it appears that poststroke visual plasticity is dynamic, with a critical window of opportunity in the early postdamage period to attain more rapid, more extensive recovery of a larger set of visual perceptual abilities.
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23
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Pandey A, Neupane S, Adhikary S, Vaidya K, Pack CC. Cortical visual impairment at birth can be improved rapidly by vision training in adulthood: A case study. Restor Neurol Neurosci 2022; 40:261-270. [PMID: 37038774 DOI: 10.3233/rnn-221294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
Abstract
BACKGROUND Cortical visual impairment (CVI) is a severe loss of visual function caused by damage to the visual cortex or its afferents, often as a consequence of hypoxic insults during birth. It is one of the leading causes of vision loss in children, and it is most often permanent. OBJECTIVE Several studies have demonstrated limited vision restoration in adults who trained on well-controlled psychophysical tasks, after acquiring CVI late in life. Other studies have shown improvements in children who underwent vision training. However, little is known about the prospects for the large number of patients who acquired CVI at birth but received no formal therapy as children. METHODS We, therefore, conducted a proof-of-principle study in one CVI patient long after the onset of cortical damage (age 18), to test the training speed, efficacy and generalizability of vision rehabilitation using protocols that had previously proven successful in adults. The patient trained at home and in the laboratory, on a psychophysical task that required discrimination of complex motion stimuli presented in the blind field. Visual function was assessed before and after training, using perimetric measures, as well as a battery of psychophysical tests. RESULTS The patient showed remarkably rapid improvements on the training task, with performance going from chance to 80% correct over the span of 11 sessions. With further training, improved vision was found for untrained stimuli and for perimetric measures of visual sensitivity. Some, but not all, of these performance gains were retained upon retesting after one year. CONCLUSIONS These results suggest that existing vision rehabilitation programs can be highly effective in adult patients who acquired CVI at a young age. Validation with a large sample size is critical, and future work should also focus on improving the usability and accessibility of these programs for younger patients.
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Affiliation(s)
- Ashim Pandey
- Department of Neuro-ophthalmology, Tilganga Institute of Ophthalmology, Kathmandu, Nepal
| | - Sujaya Neupane
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Boston, USA
| | - Srijana Adhikary
- Department of Pediatric Ophthalmology and Strabismus, Tilganga Institute of Ophthalmology, Kathmandu, Nepal
| | - Keepa Vaidya
- Department of Neuro-ophthalmology, Tilganga Institute of Ophthalmology, Kathmandu, Nepal
| | - Christopher C Pack
- Department of Neurology & Neurosurgery, McGill University, Montreal, Canada
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Hurme M, Railo H. Promise and challenges for discovering transcranial magnetic stimulation induced "numbsense"-Commentary on Ro & Koenig (2021). Conscious Cogn 2021; 98:103265. [PMID: 34971969 DOI: 10.1016/j.concog.2021.103265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 11/18/2021] [Accepted: 12/20/2021] [Indexed: 11/19/2022]
Abstract
The notion that behavioral responses to stimuli can be mediated by separate unconscious and conscious sensory pathways remains popular, but also hotly debated. Recently, Ro and Koenig (2021) reported that when activity in somatosensory cortex was interfered with transcranial magnetic stimulation (TMS), participants could discriminate tactile stimuli they reported not consciously feeling. The study launches an interesting new area of research, helping to uncover mechanisms of unconscious perception that possibly generalize across different sensory modalities. However, we argue here that the study by Ro and Koenig also has several significant shortcomings, and it fails to provide evidence that pathways bypassing primary somatosensory cortex enable unconscious tactile discrimination. By referring to numerous studies investigating TMS-induced blindsight, we outline challenges in demonstrating unconscious sensory pathways using TMS. By facing to these challenges, research investigating TMS-induced numbsense has potential to stimulate progress in stubborn debates and reveal modality-general mechanisms of unconscious perception.
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Affiliation(s)
- Mikko Hurme
- Turku Brain and Mind Center, University of Turku, Turku, Finland.
| | - Henry Railo
- Turku Brain and Mind Center, University of Turku, Turku, Finland; Department of Psychology and Speech-Language Pathology, University of Turku, Turku 20014, Finland
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25
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Raffin E, Witon A, Salamanca-Giron RF, Huxlin KR, Hummel FC. Functional Segregation within the Dorsal Frontoparietal Network: A Multimodal Dynamic Causal Modeling Study. Cereb Cortex 2021; 32:3187-3205. [PMID: 34864941 DOI: 10.1093/cercor/bhab409] [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: 04/20/2021] [Revised: 10/12/2021] [Accepted: 10/15/2021] [Indexed: 12/27/2022] Open
Abstract
Discrimination and integration of motion direction requires the interplay of multiple brain areas. Theoretical accounts of perception suggest that stimulus-related (i.e., exogenous) and decision-related (i.e., endogenous) factors affect distributed neuronal processing at different levels of the visual hierarchy. To test these predictions, we measured brain activity of healthy participants during a motion discrimination task, using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). We independently modeled the impact of exogenous factors (task demand) and endogenous factors (perceptual decision-making) on the activity of the motion discrimination network and applied Dynamic Causal Modeling (DCM) to both modalities. DCM for event-related potentials (DCM-ERP) revealed that task demand impacted the reciprocal connections between the primary visual cortex (V1) and medial temporal areas (V5). With practice, higher visual areas were increasingly involved, as revealed by DCM-fMRI. Perceptual decision-making modulated higher levels (e.g., V5-to-Frontal Eye Fields, FEF), in a manner predictive of performance. Our data suggest that lower levels of the visual network support early, feature-based selection of responses, especially when learning strategies have not been implemented. In contrast, perceptual decision-making operates at higher levels of the visual hierarchy by integrating sensory information with the internal state of the subject.
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Affiliation(s)
- Estelle Raffin
- Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, EPFL, Geneva CH-1201, Switzerland.,Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, Clinique Romande de Readaptation (CRR), EPFL Valais, Sion CH-1950, Switzerland
| | - Adrien Witon
- Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, EPFL, Geneva CH-1201, Switzerland.,Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, Clinique Romande de Readaptation (CRR), EPFL Valais, Sion CH-1950, Switzerland.,Health IT, IT Department, Hôpital du Valais, Sion, Switzerland
| | - Roberto F Salamanca-Giron
- Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, EPFL, Geneva CH-1201, Switzerland.,Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, Clinique Romande de Readaptation (CRR), EPFL Valais, Sion CH-1950, Switzerland
| | - Krystel R Huxlin
- The Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY-14642, USA
| | - Friedhelm C Hummel
- Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, EPFL, Geneva CH-1201, Switzerland.,Defitech Chair in Clinical Neuroengineering, Center for Neuroprosthetics and Brain Mind Institute, Clinique Romande de Readaptation (CRR), EPFL Valais, Sion CH-1950, Switzerland.,Clinical Neuroscience, University of Geneva Medical School, Geneva CH-1205, Switzerland
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26
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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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27
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Fahrenthold BK, Cavanaugh MR, Jang S, Murphy AJ, Ajina S, Bridge H, Huxlin KR. Optic Tract Shrinkage Limits Visual Restoration After Occipital Stroke. Stroke 2021; 52:3642-3650. [PMID: 34266305 PMCID: PMC8545836 DOI: 10.1161/strokeaha.121.034738] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Supplemental Digital Content is available in the text. Background and Purpose: Damage to the adult primary visual cortex (V1) causes vision loss in the contralateral visual hemifield, initiating a process of trans-synaptic retrograde degeneration. The present study examined functional implications of this process, asking if degeneration impacted the amount of visual recovery attainable from visual restoration training in chronic patients, and if restoration training impacted optic tract (OT) shrinkage. Methods: Magnetic resonance imaging was used to measure OT volumes bilaterally in 36 patients with unilateral occipital stroke. From OT volumes, we computed laterality indices (LI), estimating the stroke-induced OT shrinkage in each case. A subset of these chronic patients (n=14, 13±6 months poststroke) underwent an average of nearly 1 year of daily visual restoration training, which repeatedly stimulated vision in their blind field. The amount of visual field recovery was quantified using Humphrey perimetry, and post training magnetic resonance imaging was used to assess the impact of training on OT shrinkage. Results: OT LI was correlated with time since stroke: it was close to 0 (no measurable OT shrinkage) in subacute participants (<6 months poststroke) while chronic participants (>6 months poststroke) exhibited LI >0, but with significant variability. Visual training did not systematically alter LI, but chronic patients with baseline LI≈0 (no OT shrinkage) exhibited greater visual field recovery than those with LI>0. Conclusions: Unilateral OT shrinkage becomes detectable with magnetic resonance imaging by ≈7 months poststroke, albeit with significant interindividual variability. Although visual restoration training did not alter the amount of degeneration already sustained, OT shrinkage appeared to serve as a biomarker of the potential for training-induced visual recovery in chronic cortically blind patients.
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Affiliation(s)
- Berkeley K. Fahrenthold
- Flaum Eye Institute (B.K.F., M.R.C., S.J., K.R.H.), University of Rochester, NY. Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, United Kingdom. Department of Neurorehabilitation and Therapy Services, The National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
| | - Matthew R. Cavanaugh
- Flaum Eye Institute (B.K.F., M.R.C., S.J., K.R.H.), University of Rochester, NY. Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, United Kingdom. Department of Neurorehabilitation and Therapy Services, The National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
| | - Subin Jang
- Flaum Eye Institute (B.K.F., M.R.C., S.J., K.R.H.), University of Rochester, NY. Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, United Kingdom. Department of Neurorehabilitation and Therapy Services, The National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
| | - Allison J. Murphy
- Neuroscience Graduate Program (A.J.M.), University of Rochester, NY. Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, United Kingdom. Department of Neurorehabilitation and Therapy Services, The National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
| | | | | | - Krystel R. Huxlin
- Flaum Eye Institute (B.K.F., M.R.C., S.J., K.R.H.), University of Rochester, NY. Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, United Kingdom. Department of Neurorehabilitation and Therapy Services, The National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
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28
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Rehabilitation of visual disorders. HANDBOOK OF CLINICAL NEUROLOGY 2021; 178:361-386. [PMID: 33832686 DOI: 10.1016/b978-0-12-821377-3.00015-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
While there is a long history of rehabilitation for motor deficits following cerebral lesions, less is known about our ability to improve visual deficits. Vision therapy, prisms, occluders, and filters have been advocated for patients with mild traumatic brain injury, on the premise that some of their symptoms may reflect abnormal visual or ocular motor function, but the evidence for their efficacy is modest. For hemianopia, attempts to restore vision have had unimpressive results, though it appears possible to generate blindsight through training. Strategic approaches that train more efficient use of visual search in hemianopia have shown consistent benefit in visual function, while prism aids may help some patients. There are many varieties of alexia. Strategic adaptation of saccades can improve hemianopic alexia, but there has been less work and mixed results for pure alexia, neglect dyslexia, attentional dyslexia, and the central dyslexias. A number of approaches have been tried in prosopagnosia, with recent studies of small groups suggesting that face perception of prosopagnosic subjects can be enhanced through perceptual learning.
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Abstract
PURPOSE OF REVIEW Homonymous visual field defects are a common sequela of stroke, and are assumed to be permanent within a few weeks of the event. Because consensus about the efficacy of rehabilitation is lacking, visual therapy is rarely prescribed. Here, we review current rehabilitation options and strategies in the translational pipeline that could change these perspectives. RECENT FINDINGS The mainstays of available therapy for homonymous visual defects are compensation training and substitution, which allow patients to better use their spared vision. However, early clinical studies suggest that vision can partially recover following intensive training inside the blind field. Research into the relative efficacy of different restorative approaches continues, providing insights into neurophysiologic substrates of recovery and its limitations. This, in turn, has led to new work examining the possible benefits of earlier intervention, advanced training procedures, noninvasive brain stimulation, and pharmacological adjuvants, all of which remain to be vetted through properly powered, randomized, clinical trials. SUMMARY Research has uncovered substantial visual plasticity after occipital strokes, suggesting that rehabilitative strategies for this condition should be more aggressive. For maximal benefit, poststroke vision-restorative interventions should begin early, and in parallel with strategies that optimize everyday use of an expanding field of view.
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Affiliation(s)
| | - Steven E Feldon
- Flaum Eye Institute
- Center for Visual Science, University of Rochester, Rochester, NY, USA
| | - Krystel R Huxlin
- Flaum Eye Institute
- Center for Visual Science, University of Rochester, Rochester, NY, USA
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Efficacy of Visual Retraining in the Hemianopic Field after Stroke: Results of a Randomized Clinical Trial. Ophthalmology 2020; 128:1091-1101. [PMID: 33242498 DOI: 10.1016/j.ophtha.2020.11.020] [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: 09/28/2020] [Revised: 11/16/2020] [Accepted: 11/17/2020] [Indexed: 11/21/2022] Open
Abstract
PURPOSE To evaluate the efficacy of motion discrimination training as a potential therapy for stroke-induced hemianopic visual field defects. DESIGN Clinical trial. PARTICIPANTS Forty-eight patients with stroke-induced homonymous hemianopia (HH) were randomized into 2 training arms: intervention and control. Patients were between 21 and 75 years of age and showed no ocular issues at presentation. METHODS Patients were trained on a motion discrimination task previously evidenced to reduce visual field deficits, but not in a randomized clinical trial. Patients were randomized with equal allocation to receive training in either their sighted or deficit visual fields. Training was performed at home for 6 months, consisting of repeated visual discriminations at a single location for 20 to 30 minutes daily. Study staff and patients were masked to training type. Testing before and after training was identical, consisting of Humphrey visual fields (Carl Zeiss Meditech), macular integrity assessment perimetry, OCT, motion discrimination performance, and visual quality-of-life questionnaires. MAIN OUTCOME MEASURES Primary outcome measures were changes in perimetric mean deviation (PMD) on Humphrey Visual Field Analyzer in both eyes. RESULTS Mean PMDs improved over 6 months in deficit-trained patients (mean change in the right eye, 0.58 dB; 95% confidence interval, 0.07-1.08 dB; mean change in the left eye 0.84 dB; 95% confidence interval, 0.22-1.47 dB). No improvement was observed in sighted-trained patients (mean change in the right eye, 0.12 dB; 95% confidence interval, -0.38 to 0.62 dB; mean change in the left eye, 0.10 dB; 95% confidence interval, -0.52 to 0.72 dB). However, no significant differences were found between the alternative training methods (right eye, P = 0.19; left eye, P = 0.10). CONCLUSIONS To date, no widely accepted therapy is available to treat HH. This study evaluated the efficacy of a promising potential treatment, visual perceptual training. We failed to find a difference between treatment training within the deficit field and control training within the sighted field when performed in a home environment.
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31
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Donovan I, Shen A, Tortarolo C, Barbot A, Carrasco M. Exogenous attention facilitates perceptual learning in visual acuity to untrained stimulus locations and features. J Vis 2020; 20:18. [PMID: 32340029 PMCID: PMC7405812 DOI: 10.1167/jov.20.4.18] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 01/08/2020] [Indexed: 12/11/2022] Open
Abstract
Visual perceptual learning (VPL) refers to the improvement in performance on a visual task due to practice. A hallmark of VPL is specificity, as improvements are often confined to the trained retinal locations or stimulus features. We have previously found that exogenous (involuntary, stimulus-driven) and endogenous (voluntary, goal-driven) spatial attention can facilitate the transfer of VPL across locations in orientation discrimination tasks mediated by contrast sensitivity. Here, we investigated whether exogenous spatial attention can facilitate such transfer in acuity tasks that have been associated with higher specificity. We trained observers for 3 days (days 2-4) in a Landolt acuity task (Experiment 1) or a Vernier hyperacuity task (Experiment 2), with either exogenous precues (attention group) or neutral precues (neutral group). Importantly, during pre-tests (day 1) and post-tests (day 5), all observers were tested with neutral precues; thus, groups differed only in their attentional allocation during training. For the Landolt acuity task, we found evidence of location transfer in both the neutral and attention groups, suggesting weak location specificity of VPL. For the Vernier hyperacuity task, we found evidence of location and feature specificity in the neutral group, and learning transfer in the attention group-similar improvement at trained and untrained locations and features. Our results reveal that, when there is specificity in a perceptual acuity task, exogenous spatial attention can overcome that specificity and facilitate learning transfer to both untrained locations and features simultaneously with the same training. Thus, in addition to improving performance, exogenous attention generalizes perceptual learning across locations and features.
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Affiliation(s)
- Ian Donovan
- Department of Psychology and Neural Science, New York University,New York,NY,USA
| | - Angela Shen
- Department of Psychology, New York University,New York,NY,USA
| | | | - Antoine Barbot
- Department of Psychology, New York University,New York,NY,USA
- Center for Neural Science, New York University,New York,NY,USA
| | - Marisa Carrasco
- Department of Psychology, New York University,New York,NY,USA
- Center for Neural Science, New York University,New York,NY,USA
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