Semantic memory in healthy apolipoprotein ε4 carriers: A systematic review

Area of Science:

• Neuroscience
• Genetics
• Cognitive Psychology

Background:

• The Apolipoprotein E (APOE) ε4 allele is a significant genetic risk factor for Alzheimer's Disease (AD).
• Research on APOE ε4's cognitive effects in healthy adults often focuses on episodic memory, with less attention paid to semantic memory.
• Understanding subtle cognitive changes in ε4 carriers may reveal preclinical AD pathology.

Purpose of the Study:

• To systematically review and synthesize existing research on the influence of the APOE ε4 allele on semantic memory functioning in non-clinical adult populations.
• To identify specific semantic memory tasks sensitive to APOE ε4 effects.
• To explore potential links between APOE ε4, semantic memory, and executive functions.

Main Methods:

• Systematic literature review adhering to PRISMA guidelines.
• Inclusion of 17 studies assessing semantic memory in healthy adults with varying APOE genotypes.
• Analysis of semantic memory performance based on task complexity and type (e.g., category fluency, naming, autobiographical memory).

Main Results:

• High heterogeneity was observed in the conceptualization and assessment of semantic memory across studies.
• No significant differences in semantic memory performance were found between APOE ε4 carriers and non-carriers on standard neuropsychological tests.
• APOE ε4 carriers exhibited poorer performance on more complex semantic memory tasks, including extended category fluency and autobiographical memory measures.

Conclusions:

• The effect of APOE ε4 on semantic memory appears task-dependent, primarily manifesting in more demanding tasks.
• These findings suggest that complex semantic memory assessments might be more sensitive to APOE ε4-related cognitive variations.
• Future research should investigate autobiographical memory retrieval and consider the mediating role of executive functions in APOE ε4 carriers.