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Inverted U-shaped prefrontal activation during speech-in-noise perception reflects neural inefficiency in older adults

Poster Session C - Sunday, March 8, 2026, 5:00 – 7:00 pm PDT, Fairview/Kitsilano Ballroom

Maxime Perron¹ (), Danielle L. Kloepfer¹, Frank A. Russo^1,2; ¹Toronto Metropolitan University, ²University of Toronto

Older adults often have difficulty understanding speech in noisy environments, even in cases where there is no discernible peripheral hearing impairment. Successful speech perception in noise depends on the coordinated engagement of perceptual and cognitive control systems, which may become less efficient with age. The present study used functional near-infrared spectroscopy (fNIRS) to examine prefrontal oxygenation (oxyhemoglobin; HbO) during a speech-in-noise recognition task in 34 older adults (age range: 63–83 years). Participants listened to sentences presented at five levels of background noise corresponding to signal-to-noise ratios (SNRs) of +4, +2, 0, −2, and −4 dB and repeated the final word of each sentence. fNIRS signals were recorded over the bilateral prefrontal cortex to index cortical activation associated with listening effort. Linear mixed-effects analyses revealed a significant inverted U-shaped relationship between HbO and listening difficulty. Bilateral prefrontal activation increased with rising noise levels but declined at the most adverse condition, indicating that neural engagement intensified with task demands until processing capacity was exceeded. Higher left prefrontal activation near the peak of the curve was associated with lower speech recognition accuracy. While both age and hearing loss predicted poorer accuracy, only age significantly predicted stronger HbO responses. These findings provide evidence for neural inefficiency in aging; whereby increased prefrontal activation represents greater resource expenditure without corresponding behavioral benefit. Overall, age-related difficulties in understanding speech in noise appear to stem from altered efficiency of cortical resource allocation, reflecting a shift from efficient to effortful neural recruitment.

Topic Area: PERCEPTION & ACTION: Development & aging