PP1018 - Neural Aging Effects in American English Monolinguals and Spanish-English Bilinguals

Abstract:
Aging is a risk factor for language comprehension decline, impacting social functionality and quality of life. This study examines the effect of aging on speech perception in older Spanish-English bilinguals and American English monolinguals, addressing the needs of a growing bilingual population. Bilinguals generally face additional cognitive challenges processing their second language, especially in noise. Using the neurophysiological marker mismatch negativity (MMN), this study explores age-related effects on vowel perception. Preliminary findings suggest bilingualism may support cognitive processing with age, contributing to our understanding of auditory processing in aging and in those speaking English as a second language.

Summary:
Background
Previous research suggests age-related deteriorations of central auditory processing, reduced cognitive capacity, and decline in speech discrimination abilities and memory (e.g., Choi et al., 2022). Aging is a risk factor for language comprehension decline, impacting social functionality and quality of life. Several studies have shown that mismatch negativity (MMN), an automatic neural response recorded within the electroencephalography (EEG) might reflect discrimination at a pre-attentive, automatic level of processing (e.g., Näätänen et al., 2012; Bartha-Doering et al., 2015; Partanen et al., 2011).

This study aimed to understand how cognitive exercises impact speech processing differences associated with aging and automatic electrophysiological response. The goal was to identify differences in vowel sound discrimination between American-English monolingual and Spanish-English bilingual in different aging groups. The study examined the following: 1) the impact that bilingualism has on neurophysiological effects of the aging process on speech perception with the contribution of cognitive demand, 2) the effectiveness of innate ability versus bilingual experience as predictors of speech perception in older adults. Specific questions  were a) Are there differences in speech perception, as indexed by MMN, between older bilinguals and older monolinguals? and b) Are there aging effects in speech perception in monolinguals and bilinguals?

Methods
Neural encoding of the acoustic features and neural discrimination were examined using the modified oddball paradigm. Age-related speech processing deficits were studied from two different bilingual and monolingual aging groups: younger (18-39y) and older (50y+). The MMN responses (amplitude/latency) were recorded utilizing a 32-channel BrainVision actiCAP system (Brain Products GmbH). A phonological memory repetition task (cognitive exercise) was inserted between two EEG sessions (Part 1 and Part 2). The Quick Speech in Noise (QuickSIN) test and the Montreal Cognitive Assessment (MoCA) test were also administered to examine their correlation with EEG data.

Results
Preliminary results show that there was no change in MMN before and after the phonological task in the younger bilingual and monolingual groups, as expected. Both younger groups showed larger MMNs in Part 1. In contrast, older bilinguals exhibited a larger MMN in Part 2, while older monolinguals showed a diminished MMN and poor waveform morphology, particularly in frontal regions.

Conclusion
This study highlights key differences in auditory processing between monolingual and bilingual older adults, demonstrating that bilingualism may influence resilience in speech perception as we age. While younger adults maintained stable MMN responses, older bilinguals showed a larger MMN following cognitive tasks, suggesting a retained sensitivity to speech sounds. Conversely, older monolinguals displayed diminished MMN responses and poor waveform morphology, particularly in frontal regions, indicating potential age-related declines in auditory discrimination. These findings suggest that bilingual experience may mitigate some age-related deficits in speech perception, informing strategies for auditory rehabilitation and interventions aimed at supporting communication in aging populations.

This study contributes to the understanding of auditory processing in aging persons with cognitive decline and in those who speak English as a second language. Ultimately, the goal of this experiment is to improve the likelihood of success of auditory rehabilitation and aural therapy techniques.