Remote episodic memory deficits in patients with unilateral temporal lobe epilepsy and excisions

The nature of remote memory impairment in patients with medial temporal lob e damage is the subject of some debate. While some investigators have found that retrograde amnesia in such patients is temporally graded, with relati ve sparing of remote memories (Squire and Alvarez, 1995), others contend th at impairment is of very long duration and that remote memories are not nec essarily spared (Sanders and Warrington, 1971; Nadel and Moscovitch, 1997). In this study, remote memory was assessed in 25 patients with unilateral t emporal lobe epilepsy and 22 non-neurologically impaired controls using the Autobiographical Memory Interview (Kopelman et al., 1989). Results indicat e that patients have impaired personal episodic memory but intact personal semantic memory. The impairment extends even to the most remote time period s in early childhood, long before seizure onset in many patients. As well, patients awaiting temporal lobectomy for control of seizures perform as poo rly as those who have already undergone resective surgery. These results su pport the hypothesis that temporal lobe damage or dysfunction, caused by re current seizures or surgical excision, results in extensive retrograde amne sia for personal episodic memories. Interestingly, patients with radiologic al evidence of hippocampal sclerosis were not significantly more impaired t han those without obvious sclerosis. These results indicate that even minim al damage to medial temporal lobes results in significant impairment to aut obiographical episodic memory. These findings are more compatible with a me mory loss or retrieval deficit rather than a consolidation account of remot e memory impairment.