Representation of a Break in Interaural Correlation

20 The auditory peripheral system filters broadband sounds into narrowband waves, and 21 decomposes narrowband waves into quickly-varying temporal fine structures (TFSs) and 22 slowly-varying envelopes. When a noise is presented binaurally (with the interaural 23 correlation being 1), human listeners can detect a transient break in interaural correlation 24 (BIC), which does not alter monaural inputs substantially. The central correlates of BIC are 25 unknown. This study examined whether phase-locking based frequency-following responses 26 (FFRs) of neuron populations in the rat auditory midbrain (inferior colliculus, IC) to 27 interaurally correlated steady-state narrowband noises are modulated by introducing a BIC. 28 The results showed that the noise-induced FFR exhibited both a TFS component (FFRTFS) 29 and an envelope component (FFREnv), signaling the center frequency and bandwidth, 30 respectively. Introducing either a BIC or an interaurally correlated amplitude-gap (which had 31 the summated amplitude matched to the BIC) significantly reduced both FFRTFS and FFREnv. 32 However, the BIC-induced FFRTFS reduction and FFREnv reduction were not correlated with 33 the amplitude-gap-induced FFRTFS reduction and FFREnv reduction, respectively. Thus, 34 although introducing a BIC does not affect monaural inputs, it causes a temporary reduction 35 in sustained responses of IC neuron populations to the noise. This BIC-induced FFR 36 reduction is not based on a simple linear summation of noise signals. 37 38