Abstract
Hemianopia is a visual field defect characterized by decreased vision or blindness in the contralesional visual field of both eyes. The presence of well documented above-chance unconscious behavioural responses to visual stimuli presented to the blind hemifield (blindsight) has stimulated a great deal of research on the neural basis of this important phenomenon. The present study is concerned with electrophysiological responses from the blind field. Since previous studies found that transient Visual Evoked Potentials (VEPs) are not entirely suitable for this purpose here we propose to use Steady-State VEPs (SSVEPs). A positive result would have important implications for the understanding of the neural bases of conscious vision. We carried out a passive SSVEP stimulation with healthy participants and hemianopic patients. Stimuli consisted of four black-and-white sinusoidal Gabor gratings presented one in each visual field quadrant and flickering one at a time at a 12. Hz rate. To assess response reliability a Signal-to-Noise Ratio analysis was conducted together with further analyses in time and frequency domains to make comparisons between groups (healthy participants and patients), side of brain lesion (left and right) and visual fields (sighted and blind).The important overall result was that stimulus presentation to the blind hemifield yielded highly reliable responses with time and frequency features broadly similar to those found for cortical extrastriate areas in healthy controls. Moreover, in the intact hemifield of hemianopics and in healthy controls there was evidence of a role of prefrontal structures in perceptual awareness. Finally, the presence of different patterns of brain reorganization depended upon the side of lesion.
| Original language | English |
|---|---|
| Journal | Neuropsychologia |
| DOIs | |
| Publication status | Accepted/In press - Jan 1 2017 |
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Keywords
- Extrastriate visual areas
- Hemianopia
- Perceptual awareness
- Steady-state visual evoked potentials
ASJC Scopus subject areas
- Experimental and Cognitive Psychology
- Cognitive Neuroscience
- Behavioral Neuroscience
Cite this
Visually evoked responses from the blind field of hemianopic patients. / Sanchez-Lopez, Javier; Pedersini, Caterina A.; Di Russo, Francesco; Cardobi, Nicolò; Fonte, Cristina; Varalta, Valentina; Prior, Massimo; Smania, Nicola; Savazzi, Silvia; Marzi, Carlo A.
In: Neuropsychologia, 01.01.2017.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Visually evoked responses from the blind field of hemianopic patients
AU - Sanchez-Lopez, Javier
AU - Pedersini, Caterina A.
AU - Di Russo, Francesco
AU - Cardobi, Nicolò
AU - Fonte, Cristina
AU - Varalta, Valentina
AU - Prior, Massimo
AU - Smania, Nicola
AU - Savazzi, Silvia
AU - Marzi, Carlo A.
PY - 2017/1/1
Y1 - 2017/1/1
N2 - Hemianopia is a visual field defect characterized by decreased vision or blindness in the contralesional visual field of both eyes. The presence of well documented above-chance unconscious behavioural responses to visual stimuli presented to the blind hemifield (blindsight) has stimulated a great deal of research on the neural basis of this important phenomenon. The present study is concerned with electrophysiological responses from the blind field. Since previous studies found that transient Visual Evoked Potentials (VEPs) are not entirely suitable for this purpose here we propose to use Steady-State VEPs (SSVEPs). A positive result would have important implications for the understanding of the neural bases of conscious vision. We carried out a passive SSVEP stimulation with healthy participants and hemianopic patients. Stimuli consisted of four black-and-white sinusoidal Gabor gratings presented one in each visual field quadrant and flickering one at a time at a 12. Hz rate. To assess response reliability a Signal-to-Noise Ratio analysis was conducted together with further analyses in time and frequency domains to make comparisons between groups (healthy participants and patients), side of brain lesion (left and right) and visual fields (sighted and blind).The important overall result was that stimulus presentation to the blind hemifield yielded highly reliable responses with time and frequency features broadly similar to those found for cortical extrastriate areas in healthy controls. Moreover, in the intact hemifield of hemianopics and in healthy controls there was evidence of a role of prefrontal structures in perceptual awareness. Finally, the presence of different patterns of brain reorganization depended upon the side of lesion.
AB - Hemianopia is a visual field defect characterized by decreased vision or blindness in the contralesional visual field of both eyes. The presence of well documented above-chance unconscious behavioural responses to visual stimuli presented to the blind hemifield (blindsight) has stimulated a great deal of research on the neural basis of this important phenomenon. The present study is concerned with electrophysiological responses from the blind field. Since previous studies found that transient Visual Evoked Potentials (VEPs) are not entirely suitable for this purpose here we propose to use Steady-State VEPs (SSVEPs). A positive result would have important implications for the understanding of the neural bases of conscious vision. We carried out a passive SSVEP stimulation with healthy participants and hemianopic patients. Stimuli consisted of four black-and-white sinusoidal Gabor gratings presented one in each visual field quadrant and flickering one at a time at a 12. Hz rate. To assess response reliability a Signal-to-Noise Ratio analysis was conducted together with further analyses in time and frequency domains to make comparisons between groups (healthy participants and patients), side of brain lesion (left and right) and visual fields (sighted and blind).The important overall result was that stimulus presentation to the blind hemifield yielded highly reliable responses with time and frequency features broadly similar to those found for cortical extrastriate areas in healthy controls. Moreover, in the intact hemifield of hemianopics and in healthy controls there was evidence of a role of prefrontal structures in perceptual awareness. Finally, the presence of different patterns of brain reorganization depended upon the side of lesion.
KW - Extrastriate visual areas
KW - Hemianopia
KW - Perceptual awareness
KW - Steady-state visual evoked potentials
UR - http://www.scopus.com/inward/record.url?scp=85031405131&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85031405131&partnerID=8YFLogxK
U2 - 10.1016/j.neuropsychologia.2017.10.008
DO - 10.1016/j.neuropsychologia.2017.10.008
M3 - Article
AN - SCOPUS:85031405131
JO - Neuropsychologia
JF - Neuropsychologia
SN - 0028-3932
ER -