Measurement and modeling of phase synchronization of ASSR in MEG evoked by repeated chirps

Magnetoencephalography (MEG) was recorded to detect the 40 Hz component in auditory steady-state responses (ASSRs) to Dau's chirp sound regularly repeated 40 times/s. The phase coherence of the 40 Hz component increased with the chirp intensity until the latter reached about 30 dB above its absolute hearing threshold and then saturated. We constructed a differential-equation model for the phase dynamics which showed similar behavior to the experimental result in terms of the phase coherence. One of the two parameters in the model was seen to be influenced by the stimulus intensity while the other seemed unaffected.