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From Compensation to Inefficiency: Rethinking Age-Related Prefrontal Involvement in Speech-in-Noise Comprehension
Poster Session A, Friday, September 12, 11:00 am - 12:30 pm, Field House
Maxime Perron1, Hannah Schatzer1, Michael Zara1, Frank Russo1.2; 1Toronto Metropolitan University, 2University of Toronto
Understanding speech in noisy environments becomes increasingly difficult with age, even for individuals without clinically significant hearing loss. Older adults often show increased activation in prefrontal cortical (PFC) regions during speech processing under adverse listening conditions. However, the functional significance of this activation remains controversial: it may represent compensatory support for degraded auditory input or an inefficient allocation of cognitive resources that fails to improve comprehension. In this study, we used functional near-infrared spectroscopy (fNIRS) to examine age-related differences in PFC activation during sentence-level speech comprehension in noise. In addition, we examined whether individual differences in hearing sensitivity and cognitive ability predicted these neural activation patterns. Twenty-one young adults and thirty-five older adults listened to sentences presented in moderate or high noise and repeated the last word of each sentence. The sentences varied in contextual predictability, with the last words either highly predictable or less predictable. Throughout the task, fNIRS measured changes in oxygenated hemoglobin concentration in the PFC while behavioral speech comprehension accuracy was recorded. Older adults showed increased PFC activation specifically in high-noise conditions, whereas younger adults showed no significant neural modulation across noise levels. In older adults, greater right lateralized activation was associated with poorer comprehension accuracy. Mediation analyses revealed that bilateral PFC overactivation partially explained age-related declines in comprehension performance, suggesting that such activation represents maladaptive rather than compensatory processing. Although hearing thresholds and general cognitive ability did not predict overall PFC activation levels, both factors influenced neural modulation across noise conditions. Older adults with greater hearing loss or lower cognitive scores showed less differentiation in PFC activation across noise levels, indicating inefficient neural processing regardless of task difficulty. Conversely, those with better hearing sensitivity and cognitive performance showed maladaptive neural responses only in the most challenging listening conditions. Taken together, these results provide novel evidence that increased PFC activation during speech-in-noise comprehension in older adults reflects neural inefficiency, particularly when activation is right-lateralized and unresponsive to task demands. Importantly, this study highlights the potential of fNIRS to explore the neural mechanisms underlying communication difficulties in aging, and underscores the importance of developing targeted, evidence-based interventions to mitigate maladaptive PFC overactivation to promote more effective communication in older adults.
Topic Areas: Speech Perception,