Aging-related reconfiguration of auditory working-memory control under converging phonological and executive demands:...

Difficulties understanding speech in noise are common in healthy aging, even among older adults with audiometrically normal hearing, suggesting a contribution from higher-order control processes, including auditory working memory (WM). Guided by the Dual Mechanisms of Control (DMC) framework and Baddeley's multicomponent model, we recorded electroencephalography (EEG) while young and older adults performed an auditory n-back task that crossed stimulus type (digits vs. syllables) with executive load (1-back vs. 2-back). Behaviorally, older adults were slower, less accurate, and lower performance index (PI). Critically, accuracy showed a Group × Stimulus × Load interaction: older adults exhibited an excessive decrement when high phonological demand coincided with high executive load. Event-related potentials (ERPs) revealed age-related differences at multiple processing stages. In the early window, older adults showed enhanced N1 amplitudes, and N1 stimulus modulation (syllables > digits) emerged only in older adults. At mid-to-late latencies, older adults exhibited enlarged frontal P3a responses, delayed peak latencies of sustained frontal negativity (SFN) and parietal P3b. Moreover, hemispheric asymmetries dissociated across components (rightward frontal P3a vs. leftward parietal P3b), supporting partially separable control processes. Notably, this reorganization was modulated by phonological-loop demand. Brain-behavior analyses showed that larger frontal P3a was associated with lower PI for digits in older adults. Importantly, PI was also functionally relevant: in older adults, higher 1-back PI was associated with better speech-in-noise performance. Together, these findings indicate an aging-related reweighting from sustained proactive maintenance toward event-triggered reactive control in auditory WM, with selective vulnerability when phonological and executive demands converge.