Statistical analysis and interpretation of the initial response of cochlear nucleus neurons to tone bursts

1. Subject of investigation is the initial response of cochlear nucleus neurons and units presumed to be auditory nerve fibres to CF tone burst stimulation. 2. The initial response is characterized by computing the distribution of the latency of the first spike and of the duration of the first interval in the ensemble of responses to a large number of stimuli. 3. In many of the neurons the properties of both distributions appear to be related. The presumed auditory nerve fibres and spontaneously active cochlear nucleus neurons showing only activation responses to tonal stimuli (A type) exhibit irregularity in both response onset and intervals. Minimum latency and minimum first intervals are short. On the other hand, spontaneously active neurons with both activation and suppression in the response area (AS type) and silent neurons showing only activation (A(S) type) often show a more precisely timed onset of response and narrow interval distributions. In many neurons this leads to oscillations in the PSTH (chopping). In these neurons minimum latency and minimum first interval have higher values. The longer minimum latency cannot be attribute-d to longer pure time delays in these neurons. 4. The results are interpreted as speaking in favour of temporal integration as an important mechanism in many of the AS and A(S) neurons, particularly those in the DCN. The firing patterns of A neurons are thought to indicate virtual absence of this mechanism. 5. Using pure time delay estimates derived from cross-correlation functions, computed from the responses to stationary noise, an attempt is made to estimate the integration time in the cochlear and in the cochlear nucleus neurons.