Semantic Memory Space Becomes Denser with Age.

Semantic memory, a repository for concepts and factual information, plays a vital role in acquiring and retrieving knowledge. This study explores the impact of age-related knowledge accumulation on semantic cognition, investigating whether a denser representational space affects retrieval processes. Using a semantic feature verification task, we employ both behavioral (reaction time; RT) and neurophysiological (event-related potential; ERP) measures to explore these dynamics across young and older adults. Findings revealed an age-related RT difference in retrieval of semantically incongruent features, indicative of increased semantic search demands with age. ERP results show attenuated N400 responses in older adults for congruent features, possibly reflecting increased semantic relatedness. The late frontal effect (LFE) shows sustained modulation in older adults, indicative of enhanced post-retrieval monitoring. We propose that this extended search through semantic memory reflects an increase in the number of features to evaluate. These results support the idea that aging leads to a more densely packed semantic space, impacting the speed and dynamics of semantic retrieval.