Repetition Priming in Individuals with Amnestic Mild Cognitive Impairment and Alzheimer’s Dementia: a Systematic Review and Meta-Analysis

Abstract

The literature on repetition priming in Alzheimer’s disease (AD) is inconsistent, with some findings supporting spared priming while others do not. Several factors may explain these inconsistencies, including AD severity (e.g., dementia vs. Mild Cognitive Impairment; MCI) and priming paradigm-related characteristics. This systematic review and meta-analysis provides a quantitative summary of repetition priming in AD. We examined the between-group standard mean difference comparing repetition priming in AD dementia or amnestic MCI (aMCI; presumably due to AD) to controls. Thirty-two studies were selected, including 590 individuals with AD dementia, 267 individuals with amnestic MCI, and 703 controls. Our results indicated that both individuals with aMCI and AD dementia perform worse on repetition priming tasks than cognitively older adults. Paradigm-related moderators suggested that the effect size between studies comparing the combined aMCI or AD dementia group to cognitively healthy older adults was the highest for paradigms that required participants to produce, rather than identify, primes during the test phase. Our results further suggested that priming in AD is impaired for both conceptual and perceptual priming tasks. Lastly, while our results suggested that priming in AD is impaired for priming tasks that require deep processing, we were unable to draw firm conclusions about whether priming is less impaired in aMCI or AD dementia for paradigms that require shallow processing.

Declarative Learning, Priming, and Procedural Learning Performances comparing Individuals with Amnestic Mild Cognitive Impairment, and Cognitively Unimpaired Older Adults

“…In line with the typical spread in AD pathology, declarative learning and memory decline in the early stages of AD as atrophy tends to occur first in the hippocampus and entorhinal cortex (Stoub, Rogalski, Leurgans, Bennett, & deToledo-Morrell, 2010). Brain structures involved in priming tasks are dependent on task characteristics (Schacter, Dobbins, & Schnyer, 2004), however, conceptual repetition priming is thought to rely on the inferior frontal and temporal regions including the fusiform gyrus and parahippocampal gyrus (Buckner, Koutstaal, Schacter, & Rosen, 2000;De Wit et al, 2021;Schacter, Wig, & Stevens, 2007), which are likely impacted once the AD pathology spreads throughout the temporal lobe. Procedural learning is thought to rely on the subcortical brain areas that are thought to remain intact until the severe stages of AD (Knowlton et al, 1996;Sanes et al, 1990;Seger, 2006).…”

“…Procedural learning was shown to be similar in individuals with aMCI/AD dementia and controls, with no statistical or meaningful differences, suggesting sparing in aMCI/AD dementia (De Wit et al, 2020). However, the literature on repetition priming in AD dementia is less conclusive (De Wit et al, 2021) and, therefore, more studies on repetition priming in the MCI phase of AD are needed.…”

“…Procedural learning is thought to rely on the subcortical brain areas that are thought to remain intact until the severe stages of AD (Knowlton et al, 1996;Sanes et al, 1990;Seger, 2006). As a result, both repetition priming and procedural learning are thought to remain intact in the very early stages of AD, with procedural learning remaining intact until the disease progresses to the severe stages (De Wit et al, 2021.…”

“…However, the literature regarding the degree of sparing in procedural learning and repetition priming across the AD severity spectrum remains inconclusive, which may prevent the incorporation of techniques based on these memory systems into clinical practice. Two meta-analyses that assessed procedural learning and repetition priming comparing individuals with aMCI or AD dementia to controls highlighted that only three studies assessed procedural learning and only four studies thus far assessed repetition priming in MCI compared to controls (De Wit et al, 2021. Procedural learning was shown to be similar in individuals with aMCI/AD dementia and controls, with no statistical or meaningful differences, suggesting sparing in aMCI/AD dementia (De Wit et al, 2020).…”

Set Size of Information in Long-Term Memory Similarly Modulates Retrieval Dynamics in Young and Older Adults

“…Along these lines, studies in amnesic patients, who have difficulties in recalling information, show intact semantic priming in a word-completion test (Graf et al, 1985). In contrast, patients with Alzheimer's disease, but not healthy older subjects, may be impaired in the word-completion test (Fleischman and Gabrieli, 1998;Millet et al, 2010;De Wit et al, 2021).…”