Neuromagnetic evidence of broader auditory cortical tuning in schizophrenia.

Deficits in basic auditory perception have been described in schizophrenia. Previous electrophysiological imaging research has documented a structure-function disassociation in the auditory system and altered tonotopic mapping in schizophrenia. The present study examined auditory cortical tuning in patients with schizophrenia. Eighteen patients with schizophrenia and 15 comparison subjects were recorded in a magnetoencephalographic (MEG) experiment of auditory tuning. Auditory cortical tuning at 1 kHz was examined by delivering 1 kHz pure tones in conjunction with pure tones at 5 frequencies surrounding and including 1 kHz. Source reconstruction data were examined for evidence of frequency specificity for the M100 component. There was a significant broadening of tuning in the schizophrenia group evident for the source amplitude of the M100. The frequently reported reduction in anterior-posterior source asymmetry for individuals with schizophrenia was replicated in this experiment. No relationships between symptom severity ratings and MEG measures were observed. This finding suggests that the frequency specificity of the M100 auditory evoked field is disturbed in schizophrenia, and may help explain the relatively poor behavioral performance of schizophrenia patients on simple frequency discrimination tasks.