The second face of blindness: Processing speed deficits in the intact visual field after pre- and post-chiasmatic lesions

Bola, Michał; Gall, Carolin; Sabel, Bernhard A.

doi:10.1016/j.jns.2013.07.1952

Cited by 5 publications

(8 citation statements)

References 58 publications

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“…Regarding visual detection and analysis, Paramei and Sabel (2008) reported that these patients exhibited diminished abilities to detect fragmented targets among a noisy background in the IVF, whereas Schadow et al (2009) found deficits in the early and late visual processing of Gestalt patterns in the IVF. More recently, Bola et al (2013b) confirmed these findings and reported processing-speed deficits in a simple detection task in the IVF. The authors termed this phenomenon sightblindness , as the reverse situation of blindsight ( Bola et al, 2013a ): the former refers to visuo-attentional deficits in the IVF, whereas the latter refers to residual (although implicit) visual abilities in the contralesional visual field (CVF) that are highlighted in forced-choice tasks (e.g., Weiskrantz et al, 1974 ).…”

Section: Less-studied Consequences Of Unilateral Occipital Lesionssupporting

confidence: 55%

“…Conversely to the case of blindsight, which has been extensively studied in hemianopia patients, vision quality in the central visual field and in the IVF of these patients has scarcely been assessed, and moreover, it has traditionally been assumed to remain intact. However, as recently proposed, neither the central visual field ( Cavézian et al, 2010 ; Perez et al, 2013 ), nor the IVF of hemianopic patients ( Bola et al, 2013a , b , Clatworthy et al, 2013 ; Cavézian et al, 2015 ) actually appear to be fully intact or functional. Moreover, as we recently proposed, and as discussed below, the nature of the task, the type of stimulus and the side of the occipital lesion might determine the central and ipsilesional visual deficit in hemianopic patients ( Cavézian et al, 2010 , 2015 ; Perez et al, 2013 ).…”

Section: Less-studied Consequences Of Unilateral Occipital Lesionsmentioning

confidence: 83%

“…Interestingly, they observed that patients with a left medial occipital lesion exhibited hemianopic alexia, whereas patients whose lesion reached the fusiform gyrus suffered from pure alexia ( McDonald et al, 2006 ). Nonetheless, in addition to the deleterious consequences of contralesional visual field defect on the ensemble of activities in which vision is crucial, it was recently discovered that HH patients can also exhibit impairments in their central visual field and in their ipsilesional visual field ( Cavézian et al, 2010 ; Bola et al, 2013b ). This phenomenon, which has been named sightblindness (an approximate inversion of the term blindsight ; see below), refers to the existence of visual deficits in the visual field that is (mistakenly) considered to be unaffected ( Bola et al, 2013a ).…”

Section: Behavioral Consequences Of a Unilateral Occipital Lesionmentioning

confidence: 99%

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Behavioral Consequences and Cortical Reorganization in Homonymous Hemianopia

Chokron

Perez

Peyrin

2016

Front. Syst. Neurosci.

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The most common visual defect to follow a lesion of the retrochiasmal pathways is homonymous hemianopia (HH), whereby, in each eye, patients are blind to the contralesional visual field. From a behavioral perspective, in addition to exhibiting a severe deficit in their contralesional visual field, hemianopic patients can also present implicit residual capacities, now usually referred to collectively as blindsight. It was recently demonstrated that HH patients can also suffer from a subtle deficit in their ipsilesional visual field, called sightblindness (the reverse case of blindsight). Furthermore, the nature of the visual deficit in the contralesional and ipsilesional visual fields, as well as the pattern of functional reorganization in the occipital lobe of HH patients after stroke, all appear to depend on the lesion side. In addition to their contralesional and ipsilesional visual deficits, and to their residual capacities, HH patients can also experience visual hallucinations in their blind field, the physiopathological mechanisms of which remain poorly understood. Herein we review blindsight in terms of its better-known aspects as well as its less-studied clinical signs such as sightblindness, hemispheric specialization and visual hallucinations. We also discuss the implications of recent experimental findings for rehabilitation of visual field defects in hemianopic patients.

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Section: Less-studied Consequences Of Unilateral Occipital Lesionssupporting

confidence: 55%

Section: Less-studied Consequences Of Unilateral Occipital Lesionsmentioning

confidence: 83%

Section: Behavioral Consequences Of a Unilateral Occipital Lesionmentioning

confidence: 99%

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Behavioral Consequences and Cortical Reorganization in Homonymous Hemianopia

Chokron

Perez

Peyrin

2016

Front. Syst. Neurosci.

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“…Although our patients all performed at ceiling for detection of 1% contrast in their intact visual field, slight differences in fMRI responses compared with controls could reflect impairments in this mechanism. However, the importance of scotoma size (and thus probably lesion size) on the degree of impairment and the lack of any difference when comparing retinotopically equivalent responses with nonequivalent regions in a large group of quadrantanopes (Bola et al, 2013) suggest a more global effect that may reflect additional regions of cortical damage.…”

Section: Intact Hemisphere Responses For the Sighted Field Are Mostlymentioning

confidence: 99%

Abnormal Contrast Responses in the Extrastriate Cortex of Blindsight Patients

et al. 2015

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When the human primary visual cortex (V1) is damaged, the dominant geniculo-striate pathway can no longer convey visual information to the occipital cortex. However, many patients with such damage retain some residual visual function that must rely on an alternative pathway directly to extrastriate occipital regions. This residual vision is most robust for moving stimuli, suggesting a role for motion area hMTϩ. However, residual vision also requires high-contrast stimuli, which is inconsistent with hMTϩ sensitivity to contrast in which even low-contrast levels elicit near-maximal neural activation. We sought to investigate this discrepancy by measuring behavioral and neural responses to increasing contrast in patients with V1 damage. Eight patients underwent behavioral testing and functional magnetic resonance imaging to record contrast sensitivity in hMTϩ of their damaged hemisphere, using Gabor stimuli with a spatial frequency of 1 cycle/°. The responses from hMTϩ of the blind hemisphere were compared with hMTϩ and V1 responses in the sighted hemisphere of patients and a group of age-matched controls. Unlike hMTϩ, neural responses in V1 tend to increase linearly with increasing contrast, likely reflecting a dominant parvocellular channel input. Across all patients, the responses in hMTϩ of the blind hemisphere no longer showed early saturation but increased linearly with contrast. Given the spatiotemporal parameters used in this study and the known direct subcortical projections from the koniocellular layers of the lateral geniculate nucleus to hMTϩ, we propose that this altered contrast sensitivity in hMTϩ could be consistent with input from the koniocellular pathway.

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“…The fact that detection accuracy gains in glaucoma were not predominantly found in ARVs (as was seen in hemianopia 6 ) suggests that surviving retinal ganglion cells deep in the damaged zones might contribute to vision restoration or changes in intact visual field sectors. 66,67 To clearly delineate the mechanisms of vision restoration requires further study using an electroencephalogram or magnetic resonance imaging recordings.…”

Section: Research Original Investigationmentioning

confidence: 99%

Vision Restoration Training for Glaucoma

Sabel

Gudlin

2014

JAMA Ophthalmol

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IMPORTANCE Visual field loss due to retinal damage is considered irreversible, and methods are needed to achieve vision restoration. Behavioral vision training, shown to improve visual fields in hemianopia and optic nerve damage, might comprise such a method. OBJECTIVE To determine if behavioral activation of areas of residual vision using daily 1-hour vision restoration training for glaucoma for 3 months improves detection accuracy compared with placebo. DESIGN AND SETTING Prospective, double-blind, randomized, placebo-controlled clinical trial in an ambulatory care and home training setting. PARTICIPANTS Volunteer sample of patients with glaucoma (mean age, 61.7 years; age range, 39-79 years) with stable visual fields and well-controlled intraocular pressure. After randomization, 4 patients withdrew from the trial because of mild headaches (n = 2) or lack of time to complete the schedule (n = 2). INTERVENTIONS Computer-based vision restoration training for glaucoma (n = 15) or visual discrimination placebo training in the intact visual field (n = 15). MAIN OUTCOMES AND MEASURESThe primary end point was change in detection accuracy in high-resolution perimetry. Secondary end points were 30°white-on-white and 30°b lue-on-yellow near-threshold perimetry, as well as reaction time, eye movements, and vision-related and health-related quality of life.RESULTS Vision restoration training for glaucoma led to significant detection accuracy gains in high-resolution perimetry (P = .007), which were not found with white-on-white or blue-on-yellow perimetry. Furthermore, the pre-post differences after vision restoration training for glaucoma were greater compared with placebo in all perimetry tests (P = .02 for high-resolution perimetry, P = .04 for white on white, and P = .04 for blue on yellow), and these results were independent of eye movements. Vision restoration training for glaucoma (but not placebo) also led to faster reaction time (P = .009). Vision-related quality of life was unaffected, but the health-related quality-of-life mental health domain increased in both groups.CONCLUSIONS AND RELEVANCE Visual field defects caused by glaucoma can be improved by repetitively activating residual vision through training the visual field borders and areas of residual vision, thereby increasing their detection sensitivity. Our randomized clinical trial revealed evidence that visual field loss is in part reversible by behavioral, computer-based, online controlled vision training, comprising a new rehabilitation treatment option in glaucoma. Neuroplasticity of the visual cortex or higher cortical areas is the proposed mechanism of action.TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01799707.

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The second face of blindness: Processing speed deficits in the intact visual field after pre- and post-chiasmatic lesions

Cited by 5 publications

References 58 publications

Behavioral Consequences and Cortical Reorganization in Homonymous Hemianopia

Behavioral Consequences and Cortical Reorganization in Homonymous Hemianopia

Abnormal Contrast Responses in the Extrastriate Cortex of Blindsight Patients

Vision Restoration Training for Glaucoma

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