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

• Published in: Neurobiology of aging Vol. 110; pp. 1 - 12
• Main Authors: Jonin, Pierre-Yves, Duché, Quentin, Bannier, Elise, Corouge, Isabelle, Ferré, Jean-Christophe, Belliard, Serge, Barillot, Christian, Barbeau, Emmanuel J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2022; Elsevier
• Subjects: Age of Onset; Aged; Alzheimer Disease - diagnostic imaging; Alzheimer Disease - physiopathology; Alzheimer Disease - psychology; Alzheimer's disease; Association Learning - physiology; Behavior - physiology; Bioengineering; Face - physiology; Female; fMRI; Healthy Aging - physiology; Healthy Aging - psychology; Healthy Volunteers - psychology; Hippocampus - physiology; Hippocampus - physiopathology; Humans; Knowledge; Life Sciences; Magnetic Resonance Imaging; Male; Memory - physiology; Perirhinal cortex; Photic Stimulation; Prior knowledge; Recognition memory; Source memory; Prior knowledge; fMRI; Recognition memory; Perirhinal cortex; Source memory; Alzheimer's disease
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/j.neurobiolaging.2021.10.013

Impaired memory is a hallmark of prodromal Alzheimer's disease (AD). Prior knowledge associated with the memoranda improves memory in healthy individuals, but we ignore whether the same occurs 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. Patients with early AD and 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). Surprisingly, PEK strongly enhanced subsequent memory in healthy controls, but importantly not in patients. Partly nonoverlapping brain networks supported PEK vs. EK associative encoding in healthy controls. No such networks were identified in patients. In addition, patients displayed impaired activation in a right sub hippocampal region where activity predicted successful associative memory formation for PEK stimuli. Despite the limited sample sizes of this study, these findings suggest that the role prior knowledge in new learning might have been so far overlooked and underestimated in AD patients. Prior knowledge may drive critical differences in the way healthy elderly and early AD patients learn novel associations. •We asked if prior knowledge lessens the learning deficit observed in prodromal AD•AD patients did not benefit from pre-experimental knowledge (PEK; famous faces)•Distinct networks subtended associative encoding of (pre-)experimental knowledge•Controls exhibited a memory effect in the perirhinal cortex for PEK associations•By using unfamiliar items to probe memory in AD, a deficit may be underestimated