The auditory peripheral system filters broadband sounds into narrowband waves, and decomposes narrowband waves into quickly-varying temporal fine structures (TFSs) and slowly-varying envelopes. When a noise is presented binaurally (with the interaural correlation being 1), human listeners can detect a transient break in interaural correlation (BIC), which does not alter monaural inputs substantially. The central correlates of BIC are unknown. This study examined whether phase-locking based frequency-following responses (FFRs) of neuron populations in the rat auditory midbrain (inferior colliculus, IC) to interaurally correlated steady-state narrowband noises are modulated by introducing a BIC. The results showed that the noise-induced FFR exhibited both a TFS component (FFRTFS) and an envelope component (FFREnv), signaling the center frequency and bandwidth, respectively. Introducing either a BIC or an interaurally correlated amplitude-gap (which had the summated amplitude matched to the BIC) significantly reduced both FFRTFS and FFREnv. However, the BIC-induced FFRTFS reduction and FFREnv reduction were not correlated with the amplitude-gap-induced FFRTFS reduction and FFREnv reduction, respectively. Thus, although introducing a BIC does not affect monaural inputs, it causes a temporary reduction in sustained responses of IC neuron populations to the noise. This BIC-induced FFR reduction is not based on a simple linear summation of noise signals.

Wang, Q., & Li, L. (2015). Auditory Midbrain Representation of a Break in Interaural Correlation. Journal of neurophysiology , jn-00645.