Neural activity reveals effects of aging on inhibitory processes during word retrieval

Word retrieval difficulties are one of the most frustrating problems for older adults. Poorer access to phonological representation of the target word has been postulated as the underlying deficit, supported by findings of improved word retrieval after phonological priming. To better understand aging effects in the underlying neurophysiology associated with word retrieval, this study examined electrophysiological correlates of phonological priming and word retrieval in adults. Young, middle-aged, and older adults viewed pictures that were preceded by pseudo-word primes that either shared initial phonemes with or were unrelated to the picture's name. Participants made phonological judgments regarding the prime and picture prior to naming the picture. Behavioral and event-related potential correlates of phonological priming and word retrieval were recorded. All groups benefitted similarly from phonological priming, evidenced by faster phonological judgment response times and increased ease of word retrieval for primed pictures, indexed by the N400 priming effect. The peak latency of the N2, however, showed an incremental delay with age. High correlation between N2 peak latency and clinical measures of inhibition suggested an age-related delay in the inhibition of primed lexical competitors. Taken together, our results indicated intact activation of phonological representation of the picture's name but age-related delays in inhibition of primed competitors. Interestingly, our findings revealed that delays in inhibiting lexical competitors may begin as early as middle age, highlighting the importance of including multiple age groups to better represent the aging trajectory.