Transient effects during the chopping response of LSO neurons.

The initial transient chopping response of LSO neuron discharges to both monaural and binaural tone-burst stimuli in the context of a previously developed point process model of the later sustained response is analyzed and modeled. The analysis reveals the nature of the initial transient response to stimulus onset: The model's stimulus-dependent parameters vary with poststimulus-onset time while the neuron's intrinsic recovery characteristics remain constant throughout the response. By applying maximum-likelihood estimation techniques to determine the time course of the stimulus-dependent parameters, it was found that the initial excitatory and inhibitory effects decay exponentially, with their ratio determining the instantaneous rate of firing and their relative latency determining the extent of the initial chopping pattern. The "absolute" and apparent deadtime also vary exponentially during the transient portion of the response. It is concluded that the recovery characteristics of LSO neurons and, the exponential nature of the transient effects give rise to a tightly distributed latency period and a regular chopping response pattern that could encode azimuthal information.