Abstract
Stimuli presented in one visual hemifield are usually transferred from the contralateral to the ipsilateral hemisphere. However, it is not evident that such transfer always occurs and, if it does, what is the kind of information that is transferred. Presenting faces and chairs randomly in the right or in the left visual hemifield while healthy participants monitored the screen for occasionally appearing flowers elicited a robust bilateral N170-effect (N170 elicited by faces was larger than that elicited by watches), regardless where the stimuli were presented. The latency of the N170 was faster by about 10 ms in the hemisphere contralateral to the stimulus location. When the N170 elicited by two faces presented simultaneously one in the left and one in the right visual field was compared with that elicited by two simultaneously presented chairs, the bilateral N170 effect occurred at the same latency in each hemisphere. However, when a face and a chair were simultaneously presented one in the left and the other in the right visual field, comparing such composite stimuli with stimuli composed of two chairs yielded an N170-effect only in the hemisphere contralateral to the location of the face. In the hemisphere contralateral to the chair an N1 emerged, which did not distinguish the chair-face pair from the chair-chair pair. This pattern suggests that when each hemisphere receives different information and the task requires only a shallow categorization, there is no transfer of categorical information from one hemisphere to another. It is assumed that when the task involves a deeper level of analysis (such as person identification) the hemispheres should cooperate and categorical information should be transferred from one hemisphere to another even with competing bilateral stimulation. If so, a bilateral N170 effect should be observed even when a face-chair stimuli are compared with chair-chair stimuli
Meeting abstract presented at VSS 2012