Abstract :
[en] The perirhinal (PrC) and the anterolateral entorhinal (alErC) cortex are among the first brain regions impacted by Alzheimer’s Disease (AD). While their role in cognition remains unclear, recent models propose that these regions support episodic and lifetime (or absolute) familiarity when discriminating highly overlapping concepts is necessary. The present study assessed episodic familiarity judgments (task 1) and lifetime familiarity judgments (task 2), using materials with varying levels of conceptual overlap and lifetime familiarity for lures and targets (task 3). The study involved 57 older participants (aged 55+), including healthy individuals and those with either Subjective or Mild Cognitive Impairment. Volumes of the PrC, alErC, and hippocampal subfields were measured using structural MRI. As hypothesized, results suggest the PrC and the alErC volumes are linked with familiarity processes when discriminating highly overlapping concepts is required. This can be interpreted in line with recent ideas suggesting that familiarity feelings emerge from distinct neural pathways depending on the type of representations–PrC being involved in fine-grained representations. Moreover, clustering analysis revealed three distinct subgroups: one including healthy individuals, another including predominantly patients with established memory impairment, and a third, more heterogeneous group, which may represent preclinical cognitive decline. Participants in this subgroup appear to rely on familiarity to compensate for impaired recollection and commit more false alarms. Their recognition accuracy also decreases as conceptual overlap increases. We discuss how the pattern of performance across our three tasks highlights the promise of combining familiarity-related tasks to detect subtle cognitive changes associated with preclinical AD.
