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Description
Slow, endogenous auditory cortex brain rhythms are hypothesized to track acoustic amplitude modulations during speech comprehension. The tracking may be modulated by temporal predictions from the motor system. However, direct evidence for the involvement of endogenous auditory and motor brain rhythms is lacking. Using magnetoencephalographic recordings (n=57) we show that endogenous peak frequencies (spectral profile clustering approach) of individuals’ resting-state theta rhythm in superior temporal gyrus predict speech tracking (Gaussian Copula Mutual Information) during comprehension. Importantly, only for individuals with high auditory–motor synchronization profiles, endogenous rates of speech motor areas (supplementary motor area, inferior frontal gyrus) predicted auditory-cortical speech tracking. These findings align with participants’ behavioural data. Furthermore, working memory capacity predicted speech comprehension performance only in individuals with low auditory–motor synchronization profiles. The findings highlight partially independent speech processing route preferences across individuals: an auditory–motor route, related to enhanced comprehension performance, and an auditory working-memory route.