Speed of lexical access relates to quality of neural response to sound, not cognitive abilities, in younger and older adults

Abstract

Previous work has demonstrated a relationship between age-related declines in inhibitory control and difficulties identifying words of low lexical frequency and high neighborhood density (Sommers & Danielson, 1999). We hypothesized that declines in consistency of the auditory brainstem response (ABR; neural response to a repeated sound; Anderson et al., 2012) might also impede lexical access in older adults. We measured audiometric thresholds, ABR consistency, vocabulary, inhibitory control, and working memory in two groups (younger: 18-23yo, n = 41; older: 54-76yo, n = 41). We used mean target fixation proportion from 200 to 750 ms after word onset in a visual world task as a proxy for lexical access speed as listeners identified spoken words (varying on low/high: lexical frequency, neighborhood density, and cohort density; Magnuson et al., 2007). ABR consistency significantly predicted speed of word identification across variations in neighborhood and cohort densities, but contra previous findings, cognitive measures did not improve model fits. Interactions involving age, vocabulary, and lexical frequency suggest age-related linguistic expertise influences lexical access of uncommon words. We conclude that older adults exhibit increases in phonological competition due to declines in auditory encoding, suggesting that a consistent neural response to sounds leads to more efficient speech processing and lexical access.