There is considerable controversy concerning the theoretical basis of retrograde amnesia (R.A.). In the present paper, we compare medial temporal, medial plus lateral temporal, and frontal lesion patients on a new autobiographical memory task and measures of the more semantic aspects of memory (famous faces and news events). Only those patients with damage extending beyond the medial temporal cortex into the lateral temporal regions showed severe impairment on free recall remote memory tasks, and this held for both the autobiographical and the more semantic memory tests. However, on t-test analysis, the medial temporal group was impaired in retrieving recent autobiographical memories. Within the medial temporal group, those patients who had combined hippocampal and parahippocampal atrophy (H + ) on quantified MRI performed somewhat worse on the semantic tasks than those with atrophy confined to the hippocampi (H − ), but scores were very similar on autobiographical episodic recall. Correlational analyses with regional MRI volumes showed that lateral temporal volume was correlated significantly with performance on all three retrograde amnesia tests. The findings are discussed in terms of consolidation, reconsolidation, and multiple trace theory: We suggest that a widely distributed network of regions underlies the retrieval of past memories, and that the extent of lateral temporal damage appears to be critical to the emergence of a severe remote memory impairment.The neural bases of retrograde amnesia and long-term memory functions remain key issues in cognitive neuroscience. In particular, the time course of medial temporal lobe (MTL) involvement in the storage and retrieval of remote memories has not been resolved. The present study examines performance across a range of measures of remote memory in amnesic patients with focal medial temporal lobe pathology, more widespread temporal lobe damage, and frontal lobe damage. The purpose is to test theoretical predictions concerning the nature of retrograde amnesia.Despite a proliferation of studies on memory and its disorders over the last three to four decades, many of the critical issues are still widely debated (Kopelman 2002(Kopelman , 2006. There are two main theoretical positions currently discussed in the literature regarding the role of MTL structures in the retrieval of remote memories, each of which makes distinct predictions about how remote memory is affected by the physical location and extent of brain damage. According to the consolidation model (ZolaMorgan and Squire 1990; Squire 1992; Squire and Alvarez 1995), episodic (autobiographical events) and semantic memories are processed in the same way, initially dependent on the hippocampal formation, but over time they become represented in the neocortex, independently of medial temporal structures. In contrast, multiple trace theory Moscovitch 1997, 2001;Nadel et al. 2000;Moscovitch et al. 2006) proposes a critical distinction between semantic and episodic memory. Retrieval of episodic (and spatial) memo...

There are many controversies concerning the structural basis of retrograde amnesia (RA). One view is that memories are held briefly within a medial temporal store ("hippocampal complex") before being "consolidated" or reorganised within temporal neocortex and/or networks more widely distributed within the cerebral cortex. An alternative view is that the medial temporal lobes are always involved in the storage and retrieval (reactivation) of autobiographical memories (multiple trace theory). The present study used quantitative magnetic resonance imaging (MRI) in 40 patients with focal pathology/volume loss in different sites, to examine the correlates of impairment on three different measures of RA. The findings supported the view that widespread neural networks are involved in the storage and retrieval of autobiographical and other remote memories. Brain volume measures in critical structures could account for 60% of variance on autobiographical memory measures (for incidents and facts) in diencephalic patients and for 60-68% of variance in patients with frontal lesions. Significant correlations with medial temporal lobe volume were found only in the diencephalic group, in whom they were thought to reflect thalamic changes, but not in patients with herpes encephalitis or hypoxia in whom the temporal lobes were particularly implicated. The latter finding fails to support one of the main predictions of multiple trace theory, as presently expounded.

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