Auditory lateralization in schizophrenia--mismatch negativity and behavioral evidence of a selective impairment in encoding interaural time cues.

OBJECTIVE: Behavioural evidence suggests that individuals with schizophrenia may exhibit impairment in the encoding of cues to sound location. There are three primary cues used by the auditory system to locate the position of a sound in space: interaural differences in the arrival-time (ITD), phase (IPD), and the loudness (ILD) of the sound at the two ears. The goal in this study was to obtain an electrophysiological index of preattentive detection of change in sound lateralization created by these cues.
METHODS: The amplitude of mismatch negativity (MMN) was measured in 18 individuals with schizophrenia and 19 healthy comparison subjects to changes in sound lateralization produced by interaural temporal cues (ITD and IPD) and interaural loudness cues (ILD). Performance was also investigated on a target detection task, where targets were defined by ITD, IPD, or ILD cues.
RESULTS: Individuals with schizophrenia had reduced MMN amplitudes and decreased hit rates when deviants were created by interaural temporal cues, but not when loudness cues were used.
CONCLUSIONS: Results from both the MMN and behavioural task revealed a selective impairment in the use of temporal cues to sound lateralization in individuals with schizophrenia. SIGNIFICANCE: This finding supports previous research that suggests impairment in the encoding of the temporal information in schizophrenia.