Retrograde amnesia for facts and events: findings from four new cases.

Two patients with presumed hippocampal formation lesions and two patients with more extensive temporal lobe damage, all of whom became amnesic in a known year, were given tests of anterograde and retrograde memory function. The two patients with hippocampal formation lesions had moderately severe anterograde amnesia and limited retrograde amnesia for facts and events that affected, at most, the decade preceding the onset of amnesia. Content analysis could not distinguish the autobiographical recollections of the patients from the recollections of control subjects. The two patients with more extensive temporal lobe damage had severe anterograde amnesia and extensive retrograde memory loss for both facts and events. The results suggest that whether retrograde amnesia is temporally limited or very extensive depends on whether the damage is restricted to the hippocampal formation or also involves additional temporal cortex.