Segregated in perception, integrated for action: immunity of rhythmic sensorimotor coordination to auditory stream segregation.

Auditory stream segregation can occur when tones of different pitch (A, B) are repeated cyclically: The larger the pitch separation and the faster the tempo, the more likely perception of two separate streams is to occur. The present study assessed stream segregation in perceptual and sensorimotor tasks, using identical ABBABB ... sequences. The perceptual task required detection of single phase-shifted A tones; this was expected to be facilitated by the presence of B tones unless segregation occurred. The sensorimotor task required tapping in synchrony with the A tones; here the phase correction response (PCR) to shifted A tones was expected to be inhibited by B tones unless segregation occurred. Two sequence tempi and three pitch separations (2, 10, and 48 semitones) were used with musically trained participants. Facilitation of perception occurred only at the smallest pitch separation, whereas the PCR was reduced equally at all separations. These results indicate that auditory action control is immune to perceptual stream segregation, at least in musicians. This may help musicians coordinate with diverse instruments in ensemble playing.