Mapping of cortical brain activity—the use of dynamic random dot stereograms

Abstract

Three-dimensional perception (3-D) partly relies on the binocular fusion of horizontally disparate stimuli presented to the left and right eye. In humans, the input of the two eyes is fused only at the level of the visual cortex, thus, evoked potentials that are exclusively generated by cortical structures may be explored with dynamic random dot stereograms (dRDS). We determined the scalp topography of the dRDS-evoked brain activity in different groups of healthy subjects, and we found major differences between stereoscopic- and contrast-evoked brain activity: the strength of the potential fields, as well as their topography, significantly differs. Our data suggest that there are fewer neurons in the human visual cortex that are responsive to horizontal disparity, and that higher visual areas (like V2 and V3) are more engaged with stereoscopic processing than the primary visual cortex. The latencies of evoked components show no effect indicating that the binocular information flow to the visual cortex has a similar time course for both the processing of binocular dRDS and contrast information. In addition, we could show that healthy subjects improve to discriminate 3-D stimuli by training. Such changes in perceptual ability are paralleled by systematic alterations in the topography of stereoscopically evoked potential fields.