Enhanced temporal response properties of anteroventral cochlear nucleus neurons to broadband noise.

Compared with auditory nerve (AN) fibers, trapezoid body (TB) fibers of the cat show enhanced synchronization to low-frequency tones. This phenomenon probably contributes to the high temporal resolution of binaural processing. We examined whether enhanced synchronization also occurs to sustained broadband noise. We recorded responses to a reference Gaussian noise and its polarity-inverted version in the TB of barbiturate-anesthetized cats. From these we constructed shuffled autocorrelograms (SACs) and quantified spike timing by measuring the amplitude and width of their central peak. Many TB fibers with low characteristic frequency (CF) showed SACs with higher and narrower central peaks than ever observed in the AN, indicating better consistency and precision of temporal coding. Larger peaks were also observed in TB fibers with high CF, but this was mostly caused by higher average firing rates, resulting in a larger number of coincident spikes across stimulus repetitions. The results document monaural preprocessing of the temporal information delivered to binaural nuclei in the olivary complex, which likely contributes to the high sensitivity to interaural time differences.