Processing of spatial locations: hemispace effects during encoding but notrecall

Traditionally, functional differences in the visual modality between the tw o hemispheres are investigated by tachistoscopic procedures. In these exper iments, the stimuli reach the contralateral hemisphere first, and results a re commonly interpreted on the basis of neuroanatomical access models. Howe ver, numerous studies demonstrated that the hemispace where the stimulus is perceived also plays a critical role in producing laterality effects ("hem ispace effects"). In the present experiment, subjects were instructed to me morize the relative spatial positions of six figures horizontally aligned o n a presentation board. The presentation board was located either to the le ft, to the right or in front of the subjects (left, right and central learn ing positions). During a recall phase, each figure was presented in the cen ter of a computer screen and subjects were required to indicate by keypress whether a figure had been located in the left or right half of the present ation board. As in the learning phase, the computer screen was located to t he left, the right or in front of the subjects (left, right and central rec all positions). We found that the positions of the figures initially memori zed in the left hemispace were recalled faster than figures initially memor ized in the right hemispace. Hemispatial position during recall had no effe ct on performance. These results are discussed with respect to hemispheric specialization and theories of hemispace effects. (C) 2000 Elsevier Science Ltd, All lights reserved.