Theta-Band Oscillatory Responses to the Onset and Offset of Cyclic Sound Motion

In this study, wavelet analysis of EEG was performed during cyclic motion of auditory stimuli. EEG was recorded during passive listening to stimuli designed to model binaural beats by means of cyclic changes in interaural time differences (ΔT). We analyzed the changes in event-related spectral perturbation (ERSP) and phase coherence (ITC) of oscillatory activity underlying the responses to motion onset (motion-onset response, MOR) and motion offset (omitted-stimulus response, OSR). In the response to motion onset, the ERSP and ITC of theta oscillations were highest when the stimulus was near the head midline, and decreased when the stimulus was 45 or 90 deg away from the midline. Right-hemispheric ERSP and ITC were most sensitive to the motion onset position. Responses to motion offset were similar for all spatial positions of the stimulus, and were mainly generated by the phase synchronization (ITC) of theta oscillations that continued after the motion offset.