Auditory midbrain representation of a break in interaural correlation.
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 introduction of 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. Introduction of 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 introduction of 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.
Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, People's Republic of China;
Qian
Q
Wang
Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, People's Republic of China; Speech and Hearing Research Center, Key Laboratory on Machine Perception (Ministry of Education), Peking University, Beijing, People's Republic of China; PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, People's Republic of China; and Beijing Institute for Brain Disorders, Beijing, People's Republic of China liangli@pku.edu.cn.
Liang
L
Li
D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D004423:Ear; D016057:Evoked Potentials, Auditory, Brain Stem; D007839:Functional Laterality / Q000502:physiology*; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D017207:Rats, Sprague-Dawley
envelope; frequency-following responses; inferior colliculus; interaural correlation; temporal fine structure