The Post Auricular Muscle Response

Rhythmic Modulation of the Post Auricular Muscle Response in Humans

​

          The post auricular muscle, located behind the ear above the mastoid processes, produces a brief, involuntary reflex at sudden sounds. This vestigial muscle’s electrical activity, the post auricular muscle response (PAMR), is detected as a muscle action potential using electrodes placed above the mastoids. To investigate modulation during musical performance, we used electroencephalography (EEG) to monitor neural and muscular signals while human participants listened passively or actually produced sequences of drumbeats. Participants listened to and produced alternating non-rhythmic patterns and rhythmic drumbeats at 100 beats/minute. PAMR amplitudes ranged from 5-200 microvolts during active trials, and 3-70 microvolts during passive trials. We observed no statistically significant correlation between PAMR magnitude and inter-beat interval duration, nor any beat-by-beat basis for PAMR modulation. We observed that active drumming produces a larger PAMR than passive listening. We are conducting research to identify whether this modulation is attentional in nature, adding a third task condition involving oddball bass drumbeats randomly generated instead of snares. Participants will indicate the change in timbre. This will determine whether we observe the effect because participants ignore sounds during passive listening, or whether the PAMR reflects motor planning in the auditory system.