Right hippocampal impairment in the recall of spatial location: encoding deficit or rapid forgetting?

The recall of spatial location in patients with left or right temporal-lobe lesions was studied in two experiments, in which recall was tested either immediately after presentation of an array of objects, or after an intervening verbal task, a spatial task or an unfilled interval. Deficits were found only in patients with right temporal-lobe lesions that included extensive removal of the hippocampal region, and only when recall was tested after a delay. The presence of an intervening task in the delay interval did not accentuate the deficit. The results show that, despite a normal ability to encode location, patients with large right hippocampal lesions demonstrate an abnormally rapid forgetting of such information.