Characterizing memory loss in patients with autoimmune limbic encephalitis hippocampal lesions

Abstract

Since the publication of Scoville and Milner's (1957) seminal paper, the precise functional role played by the hippocampus in support of human memory has been fiercely debated. For instance, the single question of whether the hippocampus plays a time‐limited or an indelible role in the recollection of personal memories led to a deep and tenacious schism within the field. Similar polarizations arose between those who debated the precise nature of the role played by the hippocampus in support of semantic relative to episodic memories and in recall/recollection relative to familiarity‐based recognition. At the epicenter of these divisions lies conflicting neuropsychological findings. These differences likely arise due to the consistent use of heterogeneous patient populations to adjudicate between these positions. Here we utilized traditional neuropsychological measures in a homogenous patient population with a highly discrete hippocampal lesion (i.e., VGKCC‐Ab related autoimmune limbic encephalitis patients). We observed consistent impairment of recent episodic memories, a present but less striking impairment of remote episodic memories, preservation of personal semantic memory, and recall but not recognition memory deficits. We conclude that this increasingly well‐characterized patient group may represent an important homogeneous population in which the functional role played by the hippocampus may be more precisely delineated.

Determinants of cognition in autoimmune limbic encephalitis—A retrospective cohort study

“…This is problematic especially when establishing a multiple linear regression model to predict nonverbal learning capacity with 6 predictors and complete data sets of just 38 patients, resulting in an overestimation of the explained variance. As another disadvantage we were limited in the choice and temporal relation of dependent variables and predictors; (ii) since different kinds of cognitive impairments have been reported to occur in ALE (Hansen, 2019), it might be possible that learning ability is not the most appropriate parameter of hippocampal impairment in ALE (see e.g., Helmstaedter et al, 2019; Lad et al, 2019). Moreover, cognitive domains other than declarative memory, attentional, and executive functioning may be even more affected in ALE, for instance affective responses to emotional stimulation (see e.g., (Holtmann et al, 2018).…”

Systems consolidation, transformation and reorganization: Multiple Trace Theory, Trace Transformation Theory and their Competitors

“…Compromised hippocampal function led to a reduction in episodic aspects of recent and remote memories, whether for events or for environments, across the lifespan, with relative sparing of semantic or schematic aspects. This pattern of impoverished contextual details specific to an episode or location, with retention of general, non-specific information was observed in patients with extensive hippocampal damage whether caused by excisions or trauma (Sekeres et al, 2018;Wincour & Moscovitch, 2011), by infection by herpes simplex (Fujii et al, 2019) or by autoimmune disorders (Argyropoulos & Butler, 2020;Argyropoulos et al, 2019;Lad et al, 2019;Miller et al, 2020), by dementia (Piolino et al, 2009), by amnestic mild cognitive impairment (Murphy et al, 2008) or atrophy and dysfunction in normal aging (Levine et al, 2002;Viard et al, 2007), by accelerated long term forgetting and epilepsy (Butler & Zeman, 2008), by electroconvulsive therapy (ECT, Lomas et al, 2021) and by psychiatric disorders such as depression (Söderlund et al, 2014;Williams, et al, 2007) and schizophrenia (McLeod et al, 2006;Herold et al 2015).…”

Primate memory, from simple associations to abstract concepts

“…This apparent behavioral dissociation observed in amnesic patients could mostly result of the specialization of neocortex for storing long term memories. A recent study in the human shows that specific lesions of the hippocampus mostly impair the recall of newly formed episodic memories, with a preservation of personal semantic memory [18].…”

“…Cette dissociation comportementale apparente observée chez les patients amnésiques pourrait résulter de la spécialisation du néocortex dans le stockage des mémoires à long terme. Une étude récente chez l'homme montre que des lésions spécifiques de l'hippocampe affectent principalement le rappel de souvenirs épisodiques nouvellement formés, avec une préservation de la mémoire sémantique personnelle [18]. Si notre analyse est correcte, ces patients devraient présenter des déficits similaires dans le rappel de concepts nouvellement formés.…”