Memory-induced subcortical modulation of early visual evoked activity in temporal lobectomy patients

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Abstract
It has been demonstrated that the early components of visual evoked potential may be modulated by cognitive processes related to memory. This memory-induced modulation could reflect the influence of descending connections from the associative cortex to the subcortical relays. Considering the importance of the temporal cortex in memory processing the effect of unilateral temporal lesions on early evoked activity during a visual memory task was investigated. Results show that memory-induced modulation of three previously identified early components (P45, P75, and N100) is affected by both left and right temporal lobectomies. However, the right lobectomy mainly affects the P45 and P75 components, while the left temporal lobectomy affects the P75 and N100 components. The present data provide evidence that the activity in the subcortical visual relays is modulated by lateralized specific inputs from left and right temporal lobes. Early memory-induced modulation may therefore depend on some complex pathways involving both cortico-subcortical projections and interhemispheric connections.