LOCALIZATION AND LATERALIZATION OF STEREOSCOPIC PROCESSING IN THE HUMAN BRAIN

POSITRON emission tomography was used to investigate the neural substr ate of stereopsis. Changes in cerebral blood flow were measured in nin e volunteers while they judged the orientation of a rectangular cyclop ean shape in random dot stereograms. This experimental condition was c ompared with two control conditions, one having a two-dimensional shap e but no cyclopean stimulus, the other having neither shape nor cyclop ean stimulus. Blood flow increases were observed in areas 17 and 18 in the right hemisphere when comparing experimental with control conditi ons; blood flow decreases occurred in the right inferotemporal cortex. Results indicate that stereopsis begins in posterior visual areas in the right cerebral hemisphere. Under ambiguous stereoscopic conditions , participation of more anterior areas in the temporal lobe may be eli cited.