Autobiographical memory in temporal lobe epilepsy: Role of hippocampal and temporal lateral structures

The present study was aimed at investigating the impact of hippocampal and temporal cortical lesions on remote autobiographical memories in temporal lobe epilepsy (TLE). Episodic specificity, episodic richness, and personal semantic memory from different life periods were assessed using a modified version of the Autobiographical Memory Interview (AMI) (M.D. Kopelman, A.E. Wilson, A. Baddeley, The autobiographical memory interview. Bury St. Edmunds: Thames Valley Test Co.; 1990) in 47 patients with unilateral mesial or lateral TLE and 38 healthy controls. Patients with TLE performed significantly more poorly than controls. Patients with left and right mTLE were equally moderately impaired, but patients with left lateral TLE had the most severe episodic memory deficits, particularly for childhood memories. With respect to personal semantic memory, patients with left TLE were significantly more impaired than those with right TLE, most pronounced for childhood memories. Both autobiographical memory aspects, episodic and personal semantic memory, were significantly intercorrelated, but both did not correlate with anterograde memory, indicating a structural dissociation between both functions.

Research HighlightsThe impact of temporal mesial and neocortical networks for consolidation and recall of remote autobiographical memories and its emotional valence is still poorly understood. In view of the presented results, it appears that
► Both hippocampi are necessary for autobiographical memory performance, with unilateral damage being sufficient to cause mild impairment.
► The actual functional status of the hippocampus, as reflected by anterograde memory integrity, is insufficient to explain impairment in autobiographical memory.
► Considerable impairment is caused by lesions in the left temporal neocortex, which seems to play an important role in the storage of remote episodic memories. Therefore, left neocortical temporal structures should be sparingly removed in epilepsy surgery.