The Continuum of Detection and Awareness of Visual Stimuli Within the Blindfield: From Blindsight to the Sighted-Sight

Sahraie, Arash; Trevethan, Ceri T.; MacLeod, Mary Joan; Weiskrantz, Lawrence; Hunt, Amelia R.

doi:10.1167/iovs.12-11231

Cited by 28 publications

(33 citation statements)

References 35 publications

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“…The majority reported some increase in awareness over the period of multiple training sessions, though in one out of the 12 patients, a complete lack of awareness accompanied marked recovery in forced choice detection performance. Subsequently, Sahraie and others (2013) further explored the relationship between detection training and awareness in a new cohort of 5 patients; 4/5 improved on stimulus detection, but subjects fell into one of two “awareness” groups: blindsight type I (lack of awareness in spite of near-normal detection) or blindsight type II (some awareness of stimuli accompanying detection). This highlights potential differences between recovered sight and intact vision.…”

Section: How Normal Is Recovered Vision?mentioning

confidence: 99%

“…Assessment of the comparative merits of different retraining paradigms is complicated by the fact that different groups have used different visual training and testing methods as well as different outcome measures. An exception is Humphrey automated perimetry with eye tracking, which has been used as an outcome measure by several groups (Chokron and others 2008; Das and others 2014; Huxlin and others 2009; Sahraie and others 2010; Sahraie and others 2013; Sahraie and others 2006; Trevathan and others 2012; Vaina and others 2014). However, beyond providing a measure of luminance detection sensitivity used to assess the size of visual field defects, it gives little information as to the quality of recovered vision.…”

Section: How Normal Is Recovered Vision?mentioning

confidence: 99%

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Relearning to See in Cortical Blindness

2015

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The incidence of cortically induced blindness (CB) is increasing as our population ages. The major cause of CB is stroke affecting the primary visual cortex. While the impact of this form of vision loss is devastating to quality of life, the development of principled, effective rehabilitation strategies for this condition lags far behind those used to treat motor stroke victims. Here we summarize recent developments in the still emerging field of visual restitution therapy, and compare the relative effectiveness of different approaches. We also draw insights into the properties of recovered vision, its limitations and likely neural substrates. We hope that these insights will guide future research and bring us closer to the goal of providing much-needed rehabilitation solutions for this patient population.

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Section: How Normal Is Recovered Vision?mentioning

confidence: 99%

Section: How Normal Is Recovered Vision?mentioning

confidence: 99%

Relearning to See in Cortical Blindness

2015

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“…That the preserved vision is consciously accessible to the patients was evident both because of their verbal reports, accurately describing the visual stimuli presented in their blind fields, and because their performance on the two-alternative forced-choice tasks used here far exceeded chance levels, going so far as to generate reliable, measurable discrimination thresholds (35,36), despite a relatively short stimulus presentation (37) and in some cases, varying stimulus contrast (38).…”

Section: Discussionmentioning

confidence: 89%

Time is vision: functional preservation and enhanced capacity for recovery in subacute occipital stroke

Saionz

Tadin

Melnick

et al. 2019

Preprint

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One Sentence Summary: The first 3 months after an occipital stroke are characterized by a gradual -not sudden -loss of visual perceptual abilities and increased rehabilitative potential if visual discrimination training is administered in the blind field. Abstract:Stroke damage to the primary visual cortex (V1) causes a loss of vision known as hemianopia or cortically-induced blindness (CB). While early, spontaneous, perimetric improvements can occur, by 6 months post-stroke, the deficit is considered chronic and permanent. Despite evidence from sensorimotor stroke showing that early injury responses heighten neuroplastic potential, to date, rehabilitation research has focused only on chronic CB patients. Consequently, little is known about the functional properties of subacute, post-stroke visual systems, and whether they can be harnessed to enhance visual recovery. Here, for the first time, we show that conscious visual discrimination abilities are partially preserved inside subacute, perimetrically-defined blind fields, disappearing by 6 months post-stroke. Complementing this discovery, we show that global motion discrimination training initiated subacutely leads to comparable magnitude of recovery as that initiated in chronic CB. However, it does so 6 times faster, generalizes to deeper, untrained regions of the blind field, and to other [untrained] aspects of motion perception, preventing their degradation upon reaching the chronic period. Untrained subacutes exhibited only spontaneous improvements in perimetry -spontaneous recovery of motion discriminations was never observed.Thus, in CB, the early post-stroke period appears characterized by gradual -rather than suddenloss of visual processing. Subacute training stops this degradation, and is dramatically more efficient at eliciting recovery than identical training in the chronic period. Finally, spontaneous improvements in subacutes appear restricted to luminance detection, whereas recovering discrimination abilities requires deliberate training. Simply stated, after an occipital stroke, "time is VISION".

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“…Recent reports on animal models (19) and a human patient (20) with lesions extending to the lateral geniculate nucleus showed the absence of any residual visual processing within the field defect. However, in cases of postgeniculate lesions where some visual capacities are maintained, there is more likelihood of benefiting from rehabilitation techniques (21).…”

Section: Discussionmentioning

confidence: 90%

Pupil response as a predictor of blindsight in hemianopia

Sahraie

Trevethan

MacLeod

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Significance The paper follows up the suggestion that pupillometry may reveal the presence of residual visual function of which subjects are unaware (blindsight) in the field defects caused by visual cortex lesions. In a group of 19 subjects with hemi-field cortical blindness, the pupil responses in the majority matched the psychophysical findings for the sensitive spatial frequencies, indicating that it is useful to carry out pupillometry in cortical blind fields as a predictor of intact visual psychophysical function for further rehabilitation procedures.

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The Continuum of Detection and Awareness of Visual Stimuli Within the Blindfield: From Blindsight to the Sighted-Sight

Cited by 28 publications

References 35 publications

Relearning to See in Cortical Blindness

Relearning to See in Cortical Blindness

Time is vision: functional preservation and enhanced capacity for recovery in subacute occipital stroke

Pupil response as a predictor of blindsight in hemianopia

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