Endogenous auditory and motor brain rhythms predict individual speech tracking

Slow, endogenous brain rhythms in the auditory cortex are hypothesized to track acoustic amplitude modulations during speech comprehension. Temporal predictions from the motor system are thought to enhance this tracking. However, direct evidence for the involvement of endogenous auditory and motor brain rhythms is lacking. Combining magnetoencephalographic recordings with behavioral data, we here show that endogenous peak frequencies of individuals' resting-state theta rhythm in superior temporal gyrus predict speech tracking during comprehension. Importantly, endogenous rates of speech motor areas predicted auditory-cortical speech tracking only in individuals with high auditory-motor synchronization profiles. Higher rates in the supplementary motor area and lower rates in inferior frontal gyrus predicted stronger tracking. These findings provide support for oscillatory accounts of auditory-motor interactions during speech perception. Behaviorally, higher auditory-motor synchronization was related to higher comprehension, with effects of the spontaneous speech motor production rate only in high synchronizers. Working memory capacity predicted speech comprehension performance only in individuals with low auditory-motor synchronization profiles. No significant relationship between the neural data and behavioral readouts was observed. The findings highlight differential speech processing preferences across individuals, with an auditory-motor route related to enhanced comprehension performance.