The nature of recollection across months and years and after medial temporal lobe damage

Abstract

We studied the narrative recollections of memory-impaired patients with medial temporal lobe (MTL) damage who took a 25-min guided walk during which 11 planned events occurred. The recollections of the patients, recorded directly after the walk, were compared with the recollections of controls tested directly after the walk (C1), after one month (C2), or after 2.6 years (C3). With respect to memory for the walk, the narrative recollections of the patients were impoverished compared with C1 but resembled the recollections of volunteers tested after long delays (C2 and C3). In addition, how language was used by the patients in their recollections resembled how language was used by groups C2 and C3 (higher-frequency words, less concrete words, fewer nouns, more adverbs, more pronouns, and more indefinite articles). These findings appear to reflect how individuals, either memory-impaired patients or controls, typically speak about the past when memory is weak and lacks detail and need not have special implications about language use and MTL function beyond the domain of memory. A notable exception to the similarity between patient narratives and the narratives of C2 and C3 was that the control groups reported the events of the walk in correct chronological order, whereas the order in which patients reported events bore no relationship to the order in which events occurred. We suggest that the MTL is especially important for accessing global information about events and the relationships among their elements.

Semantic Memory and the Hippocampus: Revisiting, Reaffirming, and Extending the Reach of Their Critical Relationship

“…This was found even when controlling for number of overall features in the narrative and word frequency. This finding fits with data from Heyworth and Squire (2019) who found that in narrative recollections of a guided walk, patients with amnesia used higher-frequency and less concrete words than controls. Thus, even in semi-naturalistic speaking contexts, patients with amnesia demonstrate language use that is semantically impoverished.…”

Evidence of impaired naming in patients with hippocampal amnesia

“…These results suggest that the integrity of the hippocampal‐dependent declarative memory representation being communicated affects the words used to communicate it (Hilverman et al, 2017). This finding also fits with data from Heyworth and Squire (2019) who found that in narrative recollections of a guided walk, patients with amnesia used higher‐frequency and less concrete words than healthy participants. Thus, even in semi‐naturalistic speaking contexts, patients with amnesia demonstrate language use that is semantically impoverished.…”

“…Based on Klooster and Duff (2015) we predicted that patients with amnesia would perform significantly worse than healthy comparison participants. Further, based on the findings of Hilverman et al (2017) and Heyworth and Squire (2019), we predicted that patients with hippocampal amnesia would have particularly impaired performance on words that were lower in familiarity, as this variable tends to be highly correlated with word frequency. If patients demonstrate impaired naming performance relative to healthy comparison participants, this would indicate that the hippocampus is involved in remote semantic memory beyond initial acquisition.…”

Memory disorders.

“…Yet other language production deficits may be more closely linked to impairments in long-term memory. For instance, patients with amnesia use words that are less imageable in their descriptions of experienced and imagined events (Duff et al, 2011;Heyworth & Squire, 2019). This finding has been tied to the impoverished nature of the underlying memory representations.…”