Poster C87, Sunday, March 25, 1:00-3:00 pm, Exhibit Hall C
Concurrent temporal channels for auditory processing: behavioral and neurophysiological evidence reveals segregation of function at different scales
Xiangbin Teng1, David Poeppel1,2; 1Max Planck Institute, Frankfurt, Germany, 2Department of Psychology, New York University, New York, NY
Natural sounds convey perceptually relevant information over multiple timescales, and the necessary extraction of multi-timescale information requires the auditory system to work over distinct ranges. The simplest hypothesis suggests that temporal modulations are encoded in an equivalent manner within a reasonable intermediate range. We show that the human auditory system selectively and preferentially tracks acoustic dynamics concurrently at two timescales corresponding to the neurophysiological theta band (4–7 Hz) and gamma band ranges (31–45 Hz) - but, contrary to expectation, not at the timescales corresponding to alpha (8–12 Hz) and beta (13-30 Hz). While undergoing magnetoencephalography recording, listeners heard synthetic acoustic stimuli with temporally modulated structures at timescales from ~30 to ~190 ms and performed a 3-IFC match to sample study with timescale as the critical variable. MEG analyses of evoked power and intertrial phase coherence illuminate the differential encoding – only theta and gamma bands, but not other frequency bands, show robust responses to sounds. Further analyses - classification, decoding, and mutual information – demonstrate that temporal dynamics of sounds can be only read out from theta and gamma bands but not others. Source-space analysis further shows that prominent entrainment of theta and gamma bands can be localized in functionally early auditory cortex. These result echo our previous behavioral findings and lend strong support to a discrete multi-scale coding scheme on the cortical level of auditory processing (Poeppel, 2003).
Topic Area: PERCEPTION & ACTION: Audition