Low-frequency oscillations in frontocentral EEG responses associated with auditory motion processing

This study investigated the oscillatory dynamics underlying sound motion processing in a delayed motion paradigm. Auditory motion was simulated by linear changes in interaural time difference. EEG was recorded while stimuli moved at seven velocities from 90 deg/s to 450 deg/s plus an abrupt displacement. We aimed to determine how the timing and magnitude of oscillatory responses scale with motion velocity, and how they relate to motion-onset response (MOR) components. The analysis focused on MOR deflections (cN1 and cP2) and oscillatory dynamics measured via event-related spectral perturbations (ERSP) and inter-trial phase coherence (ITC) in theta and lower alpha bands. Velocity dependence was quantified using the time required for the stimulus to traverse one degree of azimuth, termed 1-degree shift time. ITC peaked earlier than ERSP, with peak latencies increasing linearly with 1-degree shift time. Nonlinear regression showed that response magnitudes followed a hyperbolic decline as a function of 1-degree shift time, which is equivalent to linear growth with velocity. Together, our findings indicate that auditory motion processing relies on common temporal integration mechanisms across evoked and oscillatory responses, with ITC showing the highest sensitivity to velocity. The observed relationships between response magnitude, latency, and velocity can be explained by the joint activity of neural populations with broad unilateral receptive fields that differ in spatial thresholds and in integration time after the stimulus enters the receptive field.