The effect of cross-channel synchrony on the perception of temporal regularity

Temporal models of pitch are based on the assumption that the auditory system measures the time intervals between neural events, and that pitch corresponds to the most common time interval. The current experiments were designed to test whether time intervals are analyzed independently in each peripheral channel, or whether the time-interval analysis in one channel is affected by synchronous activity in other channels. Regular and irregular click trains were filtered into narrow frequency bands to produce target and flanker stimuli. The threshold for discriminating a regular target from an irregular distracter click train was measured in the presence of an irregular masker click train in the target band, as a function of the frequency separation between the target band and a flanker band. The flanker click train was either regular or irregular. The threshold for detecting the regular target was 5-7 dB lower when the flanker was regular. The data indicate that the detection of temporal regularity (and thus, pitch) involves cross-channel processes that can operate over widely separated channels. Model simulations suggest that these cross-channel processes occur after the time-interval extraction stage and that they depend on the similarity, or consistency, of the time-interval patterns in the relevant channels.