Human memory and the medial temporal region of the brain.

A clear double dissociation between the effects of left and right temporal-lobe excisions was demonstrated for two identically-designed learning tasks that utilized different memoranda.Patients with left temporal-lobe lesions showed a deficit for the verbal task and normal performance for the non-verbal analogue, whereas the converse was evident for patients with right temporal-lobe lesions.Again, on two formally similar tests of short-term recall with interpolated activity, this same pattern of dissociation was observed for the retention of verbal as compared with non-verbal information.For both pairs of experiments, the severity of the materialspecifie learning and retention deficits was directly related to the extent of surgical encroachment upon the hippocampal zone of the affected hemisphere.These studies implicate the hippocampal region in the crucial transfer of experience from a temporary storage system (primary memory) to more permanent long-term storage (secondary memory)... .