Unlike in clinical blindsight patients, unconscious processing of chromatic information depends on early visual cortex in healthy humans.

Research paper by Henry H Railo, Eki E Andersson, Valtteri V Kaasinen, Teemu T Laine, Mika M Koivisto

Indexed on: 05 Apr '14Published on: 05 Apr '14Published in: Brain Stimulation


Large amount of data concerning the neural mechanisms that mediate unconscious vision come from cortically blind patients who can process stimuli presented in their blind visual field. How well the findings generalize to neurologically healthy humans remains open.Using transcranial magnetic stimulation (TMS), we studied whether chromatic processing depends on the early visual cortex in healthy participants.We employed a phenomenon called the redundant target effect (RTE): simple reaction times to two stimuli are faster than to one stimulus, even when one of the stimuli is presented outside consciousness.The RTE produced by chromatically defined stimuli disappeared when the contralateral stimulus of two bilateral stimuli was suppressed from consciousness.In contrast to studies on blindsight patients, the results imply that the early visual cortex is necessary for the processing of chromatic information in neurologically healthy humans.