Direction discrimination of moving gratings and plaids and coherence in dot displays without primary visual cortex (V1)

• Published in: The European journal of neuroscience Vol. 10; no. 12; pp. 3767 - 3772
• Main Authors: Benson, Philip J., Guo, Kun, Blakemore, Colin
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.12.1998; Wiley Subscription Services, Inc
• Subjects: Adult; Blindness - physiopathology; blindsight; Discrimination; Discrimination Learning - physiology; Eye movements; first-order motion; Humans; Male; motion; motion coherence; Motion Perception - physiology; Pattern Recognition, Visual - physiology; Photic Stimulation; plaids; second-order motion; Space life sciences; Visual Cortex - physiology; Visual Fields - physiology; United Kingdom > UK
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1046/j.1460-9568.1998.00383.x

We present new experimental observations of G.Y., a well‐tested patient with unilateral loss of primary visual cortex. We stimulated G.Y.'s blind hemifield using first‐ and second‐order motion stimuli at velocities around psychophysical threshold. Using a dual response paradigm (awareness level of visual motion, motion direction discrimination) psychophysical performance improved with increasing velocity and dot coherence. We were also able to influence directly G.Y.'s performance for the better and at will, by placing the emphasis solely on direction discrimination. In the absence of V1, graduated detection and discrimination of stimuli known to activate both V1 and extrastriate motion areas MT/V5 and MST is still possible. These results are in line with residual visual processing but did not show evidence of unconscious processing of motion stimuli characteristic of ‘blindsight’.