Improved detection following Neuro-Eye Therapy in patients with post-geniculate brain damage

Sahraie, Arash; MacLeod, Mary Joan; Trevethan, Ceri T.; Robson, Siân E.; Olson, John A.; Callaghan, Paula; Yip, Bak Sau

doi:10.1007/s00221-010-2395-z

Cited by 40 publications

(51 citation statements)

References 36 publications

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“…Azzopardi & Cowey, 1998; P. Azzopardi & Cowey, 2001; Holmes, 1918; Perenin & Jeannerod, 1975; Pöppel, Held, & Frost, 1973; Riddoch, 1917; Weiskrantz, 1996; Weiskrantz, Barbur, & Sahraie, 1995; Weiskrantz, et al, 1974; Zeki & ffytche, 1998) - we and others have shown that it is possible to re-train both simple and complex visual discriminations in portions of the blind field using moving or flickering stimuli (Huxlin et al, 2009; Raninen, Vanni, Hyvärinen, & Näsänen, 2006; Sahraie et al, 2010; Sahraie et al, 2006). However, these findings raise many questions.…”

Section: Introductionmentioning

confidence: 84%

Role of inter-hemispheric transfer in generating visual evoked potentials in V1-damaged brain hemispheres

et al. 2015

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Partial cortical blindness is a visual deficit caused by unilateral damage to the primary visual cortex, a condition previously considered beyond hopes of rehabilitation. However, recent data demonstrate that patients may recover both simple and global motion discrimination following intensive training in their blind field. The present experiments characterized motion-induced neural activity of cortically blind (CB) subjects prior to the onset of visual rehabilitation. This was done to provide information about visual processing capabilities available to mediate training-induced visual improvements. Visual Evoked Potentials (VEPs) were recorded from two experimental groups consisting of 9 CB subjects and 9 age-matched, visually-intact controls. VEPs were collected following lateralized stimulus presentation to each of the 4 visual field quadrants. VEP waveforms were examined for both stimulus-onset (SO) and motion-onset (MO) related components in postero-lateral electrodes. While stimulus presentation to intact regions of the visual field elicited normal SO-P1, SO-N1, SO-P2 and MO-N2 amplitudes and latencies in contralateral brain regions of CB subjects, these components were not observed contralateral to stimulus presentation in blind quadrants of the visual field. In damaged brain hemispheres, SO-VEPs were only recorded following stimulus presentation to intact visual field quadrants, via inter-hemispheric transfer. MO-VEPs were only recorded from damaged left brain hemispheres, possibly reflecting a native left/right asymmetry in inter-hemispheric connections. The present findings suggest that damaged brain hemispheres contain areas capable of responding to visual stimulation. However, in the absence of training or rehabilitation, these areas only generate detectable VEPs in response to stimulation of the intact hemifield of vision.

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Section: Introductionmentioning

confidence: 84%

Role of inter-hemispheric transfer in generating visual evoked potentials in V1-damaged brain hemispheres

et al. 2015

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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). Therefore, fast and effective screening for the presence of blindsight may be a useful and effective way of determining the probability of a successful rehabilitation outcome.…”

Section: Discussionmentioning

confidence: 99%

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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“…Previous research on a number of cases with blindness after brain injury shows that repeated exposure to first-order stimuli over a period, using an experimental paradigm similar to those reported here, can lift performance from chance to well-above-chance levels, but without awareness (type I blindsight). Further systematic exposure to first-order stimuli over extended periods of time can result in type II performance (19,20). It would be of interest to investigate whether transition from type I to type II would be less likely with repeated stimulation with second-order stimuli.…”

Section: Discussionmentioning

confidence: 99%

Consciousness of the first order in blindsight

Sahraie

Hibbard

Trevethan³

et al. 2010

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

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At suprathreshold levels, detection and awareness of visual stimuli are typically synonymous in nonclinical populations. But following postgeniculate lesions, some patients may perform above chance in forced-choice detection paradigms, while reporting not to see the visual events presented within their blind field. This phenomenon, termed "blindsight," is intriguing because it demonstrates a dissociation between detection and perception. It is possible, however, for a blindsight patient to have some "feeling" of the occurrence of an event without seeing per se. This is termed blindsight type II to distinguish it from the type I, defined as discrimination capability in the total absence of any acknowledged awareness. Here we report on a well-studied patient, D.B., whose blindsight capabilities have been previously documented. We have found that D.B. is capable of detecting visual patterns defined by changes in luminance (first-order gratings) and those defined by contrast modulation of textured patterns (textured gratings; second-order stimuli) while being aware of the former but reporting no awareness of the latter. We have systematically investigated the parameters that could lead to visual awareness of the patterns and show that mechanisms underlying the subjective reports of visual awareness rely primarily on low spatial frequency, first-order spatial components of the image.S ince the early reports in the 1970s of brain-damaged human subjects who are able to discriminate visual events in the absence of self-reported conscious awareness (1, 2), an obvious but difficult question has arisen as to what stimulus properties would drive visual awareness. In nonclinical populations, a number of paradigms have been developed to examine the prerequisites. For example, in attentional-blink paradigms (3), rapid serial visual presentation demonstrates that letters or words presented within a short temporal window following a task-relevant target may be degraded. As is well known, manipulating the functional significance of targets by using the participant's name (4) or emotional stimuli (5) modulates reported perception and discrimination of stimuli. More recently, the flash suppression technique in binocular rivalry, where one eye is presented with a rapid random sequence of abstract shapes while a specific stimulus is presented to the other eye (6), has been used to demonstrate that some classes of stimuli can break through and elicit awareness (7,8). Common among tasks presented to nonclinical subjects is the assumption that awareness of the stimuli and their discrimination, if not identical, cannot be dissociated from each other.The blindsight phenomenon in human subjects is unique: following visual cortical lesions, the detection and discrimination of stimulus features can occur in the absence of subjective awareness. For this reason, the research relies on "heroic" approaches such as forced-choice guessing (9). The reported awareness is then recorded using a commentary key paradigm on either a binary (10) or a mult...

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Improved detection following Neuro-Eye Therapy in patients with post-geniculate brain damage

Cited by 40 publications

References 36 publications

Role of inter-hemispheric transfer in generating visual evoked potentials in V1-damaged brain hemispheres

Role of inter-hemispheric transfer in generating visual evoked potentials in V1-damaged brain hemispheres

Pupil response as a predictor of blindsight in hemianopia

Consciousness of the first order in blindsight

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