Verbal memory performance following unilateral electrical stimulation of the human hippocampus

Verbal memory performance was studied in 12 temporal lobe epilepsy (TLE) patients during unilateral stimulation of the hippocampus. Verbal memory was assessed during baseline, left hippocampal stimulation, and right hippocampal stimulation. In left TLE patients, no effect on memory performance was observe during stimulation of either left or right hippocampus. In contrast, left hippocampal stimulation in right TLE patients produced a decrement in memory performance. By producing verbal memory impairment in right TLE patients during low-level electrical stimulation of the left hippocampus, this technique may aid in the confirmation of right temporal lobe seizure onset. Furthermore, the lack of response in left TLE patients during left hippocampal stimulation confirms left hippocampal dysfunction in left TLE patients. In addition, these results suggest that verbal memory is not simply transferred to homologous regions of the right hippocampus.