Background:
It has been proposed that auditory hallucinations result from cortical or corticosubcorti-cal disconnection. The results presented here are an initial event-related potential (ERP) exploration of data examining central auditory function and cortical connectivity.
Methods:
Twenty-two controls, 26 nonhallucinating patients with psychosis and 22 currently hallucinating patients (AVH) with psychosis were recruited. ERPs to words and tones (left ear, right ear and bilaterally) were recorded during a passive listening task. Data from the left and right ear stimuli are presented here.
Results:
The auditory N1 ERP was measured in two seven-channel composite regions – left temporal and right temporal. Words: N1 is enhanced contralater-ally in the control group. With left words, both patient groups show reduced N1 in the right hemisphere. With right words, both patient groups show a reduction in the left hemisphere. Only AVH patients show a reduction in the ipsilateral hemisphere. Tones: No contralateral N1 enhancement is evident. With left stimuli, both patient groups show reduced N1 compared with controls in both contra- and ipsilateral hemispheres. With right stimuli, only the AVH group shows a reduction in both hemispheres.
Conclusions:
The tones data confirm previous studies showing a reduced right ear advantage behaviourally in patients with schizophrenia, especially in those who hallucinate, suggesting a neurobiological origin for such behaviour. The word data suggest that more complex stimuli have a unique linguistic quality that has been more strongly lateralized. Having shown ERP differences in processing of lateralized words and tones, our next step is to look at left-right hemisphere connectivity.
