Mu rhythm dynamics suggest automatic activation of motor and premotor brain regions during speech processing

Results are mixed regarding the question of whether listening to speech activates automatic speech specific neural processes, or whether such activity is due to general cognitive mechanisms such as attention and memory. We suggest that analyzing the dynamics of mu rhythms over the course of a trial using event-related spectral perturbations (ERSPs) is useful for disentangling the competing hypotheses. Our findings suggest that there is automatic activation of motor and premotor areas of the brain that occurs while passively listening to speech, and that this activation is not present while listening to noise. Moreover, this activation is more strongly present in the low alpha frequencies, which are associated with attention, when participants engage in active discrimination of stimuli, and late in the trial prior to a button press.