Alterations in tonotopy and auditory cerebral asymmetry in schizophrenia

Background: Deficits in basic auditory perception have been described in schizophrenia. Previous electrophysiologic imaging research has documented a structure-function disassociation in the auditory system in schizophrenia. This study examines whether the most fundamental level of auditory cortical organization, tonotopy, is altered in schizophrenia. Methods: The tonotopic organization for five tone frequencies in 19 patients with schizophrenia and 22 comparison subjects was evaluated using magnetoencephalography. Auditory evoked magnetic field dipole locations were examined for the N100m component for each frequency. Results: The expected linear relationship between depth and frequency was found in the comparison subjects but not in the schizophrenia group (p< .004). In addition, normal anterior-posterior asymmetry of the N100m was found to be reduced at all five stimulation frequencies employed in the study (p< .04). No relationships between clinical symptom ratings and either tonotopy or asymmetry were observed. Conclusions: This finding suggests that the tonotopic organization of the auditory cortex in schizophrenia is disturbed and may help explain the relatively poor behavioral performance of schizophrenia patients on simple frequency discrimination tasks. Alterations in fundamental sensory organization may underlie or interact with higher order cognitive mechanisms to produce changes in cognitive task performance.