Early Auditory Processing Deficits in Schizophrenics: An fMRI Study

Abstract:
Abstract: Auditory hallucinations and thought disorder are a frequent symptom of schizophrenia and have been linked to volumetric abnormalities of the superior temporal gyrus (STG). An important question is whether or not abnormalities are present in early auditory processing stages. The mismatch negativity (MMN) is an early negative component of the auditory event-related potential that is thought to be generated in primary auditory cortex and adjacent regions of the STG. Event-related potential (ERP) recording found an abnormality in this potential that was localized to the left temporal region in schizophrenics. The MMN task and a control task in which only the dominant tone was presented repeatedly were used in conjunction with fMRI in control and schizophrenic subjects. Subjects were right handed males and consisted of 10 chronic medicated schizophrenic patients and 10 matched controls. The fMRI EPIBOLD images were acquired with a blocked task design. The auditory stimuli were presented using sound-insulated earphones (Silent Scan, Avotec). Results of cross-correlation analyses showed abnormal left STG activation in schizophrenics during the MMN task, but not during the control tone task. The results show that auditory processing in schizophrenic subjects is abnormal at a fairly early stage.