Amount, not strength of recollection, drives hippocampal activity: A problem for apparent word familiarity‐related hippocampal activation

Abstract

The role of the hippocampus in recollection and familiarity remains debated. Using functional magnetic resonance imaging (fMRI), we explored whether hippocampal activity is modulated by increasing recollection confidence, increasing amount of recalled information, or both. We also investigated whether any hippocampal differences between recollection and familiarity relate to processing differences or amount of information in memory. Across two fMRI tasks, we separately compared brain responses to levels of confidence for cued word recall and word familiarity, respectively. Contrary to previous beliefs, increasing confidence/accuracy of cued recall of studied words did not increase hippocampal activity, when unconfounded by amount recollected. In contrast, additional recollection (i.e., recollecting more information than the word alone) increased hippocampal activity, although its accuracy matched that of word recall alone. Unlike cued word recall, increasing word familiarity accuracy did increase hippocampal activity linearly, although at an uncorrected level. This finding occurred although cued word recall and familiarity memory seemed matched with respect to information in memory. The detailed characteristics of these effects do not prove that word familiarity is exceptional in having hippocampal neural correlates. They suggest instead that participants fail to identify some aspects of recollection, misreporting it as familiarity, a problem with word‐like items that have strong and recallable semantic associates.

Thalamic-medial temporal lobe connectivity underpins familiarity memory

“…ArtRepair. The inclusion of response times (RTs) as regressors (to account for variance explained by the variability in RTs characterizing each trial) did not produce any change in the main findings, consistent with our previous studies with similar methodology (e.g., Montaldi 2012, 2014;Kafkas et al 2017;Mayes et al 2019). Finally, the data were high-pass filtered using a cut-off of 128s.…”

Differential effects of sleep on explicit and implicit memory for potential trauma reminders: findings from an analogue study

“…Thus, we hypothesize that sleep selectively enhances recollection (Atienza & Cantero, 2008;Daurat et al, 2007;Drosopoulos et al, 2005; but see Groch, Wilhelm, Diekelmann, & Born, 2013). As previous findings indicate that familiaritybased recognition and priming do not rely on the hippocampus (Wang, Ranganath, & Yonelinas, 2014; but see Mayes et al, 2019;Merkow, Burke, & Kahana, 2015), we assume that these memory processes (often referred to as 'non-episodic memory'; see e.g., de Vanssay-Maigne et al, 2011;Eldridge, Knowlton, Furmanski, Bookheimer, & Engel, 2000;Rasch, Papassotiropoulos, & de Quervain, 2010) are not enhanced across sleep. As such, we assume that sleep enhances explicit recollection-based memory without affecting implicit memory (Casey et al, 2016;Giganti et al, 2014; but see Plihal & Born, 1999).…”

Progression from feature-specific brain activity to hippocampal binding during episodic encoding

“…As such, while left IFG may control organizational strategies, hippocampus may act upon this organizational structure to bind an item with its context. Previous research supports this distinction, showing that IFG generates associations whereas hippocampus is sensitive to an existing relational structure (Addis and McAndrews, 2006), with the former tracking subsequent memory confidence and the latter the number of details remembered (Qin et al, 2011;Mayes et al, 2019). Another interesting contrast suggests that IFG may actively control encoding processes while hippocampal signals are driven by inherent memorability of a scene's perceptual features (Bainbridge et al, 2017).…”