Function-based modeling of binaural processing: Interaural level

The function-based modeling approach applies optimal estimation theory to sensory phenomena for determining how relevant sensory parameters are extracted from stimuli and how the characteristics of the resulting optimal processing system compare with those of the sensory system. This approach is applied to the neural system involved in the binaural localization of sustained high-frequency sound sources: the lateral superior olive (LSO) of the cat. The sufficient statistic produced by the optimal processor is shown to be related to the interaural level difference. This level difference is processed optimally when the inputs are excitatory from one ear and inhibitory from the opposite ear. Response characteristics of LSO single units are remarkably similar, thereby strongly supporting the notion that LSO units are intimately involved in high-frequency binaural hearing. Optimal processor theory is also used to assess lateralization performance when the hearing thresholds of the two ears differ.