Learning to see 3-D: psychophysics and brain electrical activity

WE investigated human perceptual learning with stereoscopic stimuli present ed below threshold. Different visual patterns were shown as dynamic random dot stereograms in a forced-choice design in order to determine the psychop hysical thresholds of 16 adults. Brain electrical activity was recorded fro m 30 electrodes over parieto-occipital areas while stereograms were present ed with horizontal disparities below threshold. During the observation of s ub-threshold stimuli, we tested repeatedly whether implicit perceptual lear ning occurred. More than half of the subjects learned to see stereoscopic t argets. This was accompanied by topographic changes in the pattern of activ ation of neural assemblies in the visual cortex where the center of activit y shifted towards the right hemisphere. Subjects who did not improve in per ception, displayed no such effects. (C) 1999 Lippincott Williams & Wilkins.