When seeing is feeling: Acquired synaesthesia or phantom touch?

Abstract We report the case of a man (DN) who suffered a right hemisphere stroke which resulted In left hemiparesis, and in a dense left hemisensory loss when he was tested without visual feedback. By contrast, when DN saw and ‘believed’ that he was being touched, he invariably reported that he felt the appropriate tactile sensation. In this latter condition, DN could reliably estimate the pressure with which light touch was applied to his left hand. Furthermore, there was reliable transfer of tactile sensation from the left to the right hand without conscious awareness of touch on the left. Some of these findings are akin to previous reports of acquired synaesthesia; one dissimilarity is that in both developmental and acquired synaesthesia the relationship between the perceptual content experienced in the two modalities is arbitrary. An alternative Interpretation of DN's performance is that it is determined by the output of bimodal visual-somatosensory cells that have been partially deprived of their som...