A model for sound lateralization

Recent studies of multiple sclerosis (MS) and stroke patients suggested a c orrelation between two patterns of abnormal performance in lateralization t asks and two sites of pontine lesions. Most patients who had lesions below or at the superior olivary complex (SOC) perceived all interaural differenc es in binaural. stimuli as small, while most patients who had lesions above the SOC perceived all interaural differences as large. The two. abnormal p erformance patterns occurred for interaural time differences (ITD) and/or f or interaural level differences (ILD). The present model proposes a multi-l evel hierarchical brainstem structure that estimates ITD and ILD. The first level seeks dissimilarity between the left and right inputs and a second l evel looks for similarity between the two sides' inputs. Each level is mode led as an ensemble of neural arrays in which each unit performs a logic or arithmetic function. The inputs are simulations of auditory nerve responses to broadband stimuli. Simulations yield good correspondence to the effect of both locations of pontine lesions on binaural performance. (C) 2001 Acou stical Society of America.