Memory for scenes in stroke patients. Hemisphere processing of semantic organization in pictures

Twenty-one patients with cerebrovascular lesions in posterior regions of the left or right cerebral hemispheres and nonfluent aphasics with damage in anterior regions of the left hemisphere were administered a specially designed multiple-object pictorial test which measured long-term memory for scenes depicting real world schemata versus jumbled unorganized scenes. The units in the pictures were familiar figures. Memory was tested separately for single details and for whole scenes. The results showed that within the left posterior group there was significantly poorer memory for unorganized relative to organized stimuli, especially for whole scenes. There was also a selective dissociation between the left and right posterior patients on the detail versus whole scene probes in the unorganized stimuli. At the same time, organized scenes depicting real world schemata were not selectively impaired in any of the patient groups. Further, the overall memory scores on the Memory for Pictorial Scenes Test obtained by the aphasic patients were not significantly lower than those obtained by the control subjects, while scores of both posterior groups were lower than the control group. Taken together, the data suggest the following. Pictorial semantics, like linguistic semantics, are functions processed by the left posterior cortex. While the posterior region in the left hemisphere plays a special role in remembering visual situational schemata that are newly encountered, familiar visual situational schemata may be bilaterally represented.