MEMORY-INDUCED SUBCORTICAL MODULATION OF EARLY VISUAL-EVOKED ACTIVITYIN TEMPORAL LOBECTOMY PATIENTS

It has been demonstrated that the early components of visual evoked po tential may be modulated by cognitive processes related to memory. Thi s memory-induced modulation could reflect the influence of descending connections from the associative cortex to the subcortical relays. Con sidering the importance of the temporal cortex in memory processing th e effect of unilateral temporal lesions on early evoked activity durin g a visual memory task was investigated. Results show that memory-indu ced modulation of three previously identified early components (P45, P 75, and N100) is affected by both left and right temporal lobectomies. However, the right lobectomy mainly affects the P45 and P75 component s, while the left temporal lobectomy affects the P75 and N100 componen ts. The present data provide evidence that the activity in the subcort ical visual relays is modulated by lateralized specific inputs from le ft and right temporal lobes. Early memory-induced modulation may there fore depend on some complex pathways involving both cortico-subcortica l projections and interhemispheric connections.