eterminants of autobiographical memory in patients with unilateral temporal obe epilepsy or excisions

Patients with unilateral temporal lobe epilepsy from hippocampal origin and patients with unilateral surgical excision of an epileptic focus located in the medial temporal lobe were compared to healthy controls on a version of the Autobiographical Interview (AI) adapted to assess memory for event-specific and generic personal episodes. For both types of episodes, patients with unilateral (left and right) temporal lobe epilepsy or excision (TLE) reported fewer internal details, which are bits of information pertaining to the recollected episode. The source of this deficit was mainly the paucity of perceptual information about the personal episodes, but temporal and spatial information was also deficient. Information about the episode’s story elements was preserved in both AM conditions. Participants were also tested on a script generation task to assess retrieval of semantic information. Patients with TLE excision, but not pre-surgical pisodic memory emantic memory ultiple Trace Theory patients, reported significantly fewer actions per script in comparison to controls, suggesting that the temporal neocortex is more involved than mesial temporal structures in recall of this type of information. Together, these results indicate that the hippocampus is essential to the recollection of sensory perceptual aspects of past experiences. Detailed story elements and gist information, as collected during the AI and the script generation task, respectively, are more resilient to hippocampal damage. The similarity of the impairment between the event-specific and the generic memory conditions also suggests that temporal termi specificity is not a key de Autobiographical memory (AM) represents knowledge about acts and events that concern an individual. Theorists have classied AM according to dimensions such as temporal specificity, which efers to how precisely a memory is bound in time (e.g. a single fternoon versus a life-period or a relative’s name), and recollecive or re-experiential qualities, which allow one to re-experience n event in a vivid, richly-detailed manner (Brewer, 1986, 1996; onway, 1996; Conway & Pleydell-Pearce, 2000). In his seminal ork on recollection, Tulving (1985) emphasized that retrieval of xperiential detail was a critical feature separating recollective xperience from familiarity. Although temporal context could cerainly be postulated as a core attribute of recollected events, there s nothing in Tulving’s original formulation that specifies that recolection must refer to a single instance versus a ‘blended’ experience; The study was carried out at the Krembil Neuroscience Center, University Health etwork, Canada. ∗ Corresponding author at: Rm 4F-409, Toronto Western Hospital (UHN), 399 athurst Street, Toronto, Ontario, Canada M5T 2S8. Tel. : +1 416 603 5800x5796; ax: +1 416 603 5321. E-mail address: marie.st.laurent@utoronto.ca (M. St-Laurent). 028-3932/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. oi:10.1016/j.neuropsychologia. 2009.01. 032 nant of hippocampal engagement in autobiographical retrieval. © 2009 Elsevier Ltd. All rights reserved. that is, whether Proust’s madeleine evokes a particular prior experience or a conjunction of similar experiences (see also Neisser, 1981). In either case, according to Tulving, the re-experiencing is akin to mental time travel. Here, we examine Tulving’s key construct of retrieval of episodic detail in the context of normal and disordered autobiographical memory. A considerable amount of evidence indicates that the hippocampus plays a central role in AM, but the nature of its role is debated. Multiple Trace Theory (MTT) was formulated to explain variability in retrograde amnesia for different types of memories seen in association with hippocampal damage (Nadel & Moscovitch, 1997). This theory stipulates that the hippocampus is involved in the encoding and subsequent retrieval of memory for personal episodes, or event-specific AM. MTT suggests that when event-specific AM is encoded in a defined spatial and temporal context, it forms a hippocampal trace. The hippocampus supports the recollection of event-specific AM by reactivating the trace and retrieving the memory along with detailed contextual information. MTT also stipulates that forms of declarative memories that are not temporally specific and lack contextual information, also known as semantic memories, can be supported by other neural structures, and thus retrieved without a functioning hippocampus (Moscovitch et al., 2005; Nadel