Material specific learning during electrical stimulation of the human hippocampus

Material specific learning was assessed during unilateral electrical stimulation of the hippocampus through intracerebrally implanted electrodes in 30 patients with unilateral temporal lobe epilepsy (TLE). Verbal learning significantly decreased in patients with right TLE after stimulation of the left, but not the right, hippocampus. No verbal learning impairment was observed in left TLE patients following stimulation of either hippocampus. Visuospatial memory performance significantly decreased following stimulation of the right hippocampus regardless of the side of seizure onset. Results suggest that the contralateral "nonepileptic" hippocampus does not assume the material specific mnestic functions of the dysfunctional hippocampus associated with longstanding epilepsy.