Listening to subject’s commentaries can be a useful spur to novel scientific departures, as in studies of blindsight. Recently further testing has been possible with subject DB, who was a blindsight patient tested intensively over a period of 10 years and who was the subject of the book, . Essentially his original capacity is the same or somewhat more sensitive. Some further types of discriminations have now been tested that were not possible in the original study. But a new feature (...) was discovered, namely that he describes conscious after-images of a wide range of inducing stimuli of which he is unconscious. The properties of the after-images are briefly described, such as their occurrence following unseen colour patches, luminance changes, shape, spatial frequency, their long durations, showing inter-ocular transfer, as well as their conforming to Emmert’s Law. Various approaches are discussed towards finding the source of their generation, such as the use of after-images of colour mixes of separate inputs to the two eyes . They are also discussed in terms of after-images in normal subjects that are generated by imagination. The discovery offers a rare potential opportunity to compare the brain activity associated with both the conscious and unconscious attributes of the precisely the same stimuli in the same locus in the same subject. (shrink)

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 sf, moving textures of low contrast were accepted to match the response to a moving contrast-defined bar, sm. Orientation and motion direction discrimination of the perceptually matched stimuli [sm and T(sm)] was closely similar. We suggest that the existence of a satisfactory match indicates that GY has phenomenal vision. (shrink)

It has often been assumed that when we use vision to become aware of an object or event in our surroundings, this must be accompanied by a corresponding visual experience (i.e., seeing). The studies reported here show that this assumption is incorrect. When observers view a sequence of displays alternating between an image of a scene and the same image changed in some way, they often feel (or sense) the change even though they have no visual experience of it. The (...) subjective difference between sensing and seeing is mirrored in several behavioral differences, suggesting that these are two distinct modes of conscious visual perception. (shrink)