Building memories on prior knowledge: behavioral and fMRI evidence of impairment in early Alzheimer's disease

Abstract

Impaired memory is a hallmark of prodromal Alzheimer's disease (AD). Prior knowledge associated with the memoranda improves memory in healthy individuals. However, little is known about its effect in early AD. We used functional MRI to investigate whether prior knowledge enhances memory encoding in early AD, and whether the nature of this prior knowledge matters. 17 patients with early AD and 19 controls underwent a task-based fMRI experiment where they learned face-scene associations. Famous faces carried pre-experimental knowledge (PEK), while unknown faces with which participants were familiarized prior to learning carried experimental knowledge (EK). As expected, PEK enhanced subsequent memory in healthy controls, but not in patients. Importantly, partly nonoverlapping brain networks supported PEK vs. EK encoding in healthy controls. Patients displayed impaired activation in a right subhippocampal region where activity predicted successful associative memory formation for PEK stimuli. Despite the limited sample sizes, these findings underline how prior knowledge impacts learning and suggest that the extent of associative memory impairment in early AD has hitherto been underestimated.

Contextual novelty detection and novelty-related memory enhancement in amnestic mild cognitive impairment

“…The experiment failed to demonstrate novelty-related boosting effect; recognition memory performance was better for well-known than novel stimuli. This suggests that prior knowledge is a more powerful facilitator of encoding in episodic memory than novelty, at least in this kind of paradigm (Bird et al, 2011;Jonin et al, 2022). Moreover, aMCI patients had worse recognition performance than controls for familiar items, but not for novel items.…”

Neuroimaging modalities in the detection of Alzheimer's disease-associated biomarkers

“…Furthermore, some studies have shown reduced posterior cingulate gyrus/precuneus activation and hyperactivation in frontal regions, including the precentral gyrus, in MCI patients in comparison to CN individuals during memory tasks (Hampstead et al ., 2011 ; Jin et al ., 2012 ; Terry et al ., 2015 ). In AD, MTL hypoactivation, reduced posterior cingulate gyrus/praecuneus deactivation and frontal hyperactivation are approximately consistent findings during memory tasks (Canário et al ., 2022 ; Jonin et al ., 2022 ; Parra et al ., 2013 ; Petrella et al ., 2007 ; Pihlajamäki and Sperling, 2009 ; Yetkin et al ., 2006 ).…”