Low-Level Phenomenal Vision Despite Unilateral Destruction of Primary Visual Cortex

✍ Scribed by Petra Stoerig; Erhardt Barth

• Book ID: 102569827
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 215 KB
• Volume: 10
• Category: Article
• ISSN: 1053-8100
• DOI: 10.1006/ccog.2001.0526

✦ Synopsis

GY, an extensively studied human hemianope, is aware of salient visual events in his cortically blind field but does not call this "vision." To learn whether he has low-level conscious visual sensations or whether instead he has gained conscious knowledge about, or access to, visual information that does not produce a conscious phenomenal sensation, we attempted to image process a stimulus s presented to the impaired field so that when the transformed stimulus T(s) was presented to the normal hemifield it would cause a sensation similar to that caused by s in the impaired field. While degradation of contrast, spatio-temporal filtering, contrast reversal, and addition of smear and random blobs all failed to match the response to a flashed bar s(f), moving textures of low contrast were accepted to match the response to a moving contrast-defined bar, s(m). Orientation and motion direction discrimination of the perceptually matched stimuli [s(m) and T(s(m))] was closely similar. We suggest that the existence of a satisfactory match indicates that GY has phenomenal vision.