Previous event-related potential (ERP) studies have reported evidence of impaired auditory information processing in patients with schizophrenia. Some of these findings, such as the impaired P50 sensory gating, are consistent with a loss of inhibitory function. In auditory ERP studies using pairs of stimuli the size of the second response relative to the first response has been taken to indicate the extent to which responsiveness has recovered after a period of time. This variation of responsiveness has been termed the 'recovery cycle,' and is regarded as a measure of the time course of recovery of excitability of cortical neurons after stimulation. The recovery cycle of the auditory N1 ERP component was measured in 17 patients with schizophrenia and 17 age- and sexmatched healthy volunteers, and 12 patients with bipolar disorder and 12 age- and sex-matched healthy volunteers. Subjects performed a visual distraction task while listening to tone pairs, presented with intra-pair intervals of 1, 3, 5 or 7 s, with inter-pair intervals ranging between 9-13 s. Patients with schizophrenia had significantly reduced N1 amplitudes for S1 stimuli compared to healthy volunteers. For N1 amplitudes elicited by S2 stimuli there was a significant group effect whilst the main effect of intra-pair interval was not significant. A significant quadratic effect across ISI intervals was present in the healthy volunteer group, which was not significant in the schizophrenia group. Patients with bipolar disorder did not differ in N1 amplitudes elicited by S1 stimuli compared to healthy volunteers. There was no evidence of significant group differences in the recovery cycle effect between bipolar patients and matched healthy volunteers. The results provide evidence of inhibitory auditory processing deficits in schizophrenia, and further suggest that deficits in attention found in patients with schizophrenia, as indexed by reductions of auditory N1 amplitude, may be associated with impairments in inhibitory processes. In addition, different recovery cycle effects were found in patients with schizophrenia and those with bipolar disorder. Further study of the recovery cycle paradigm used in this study may lead to the development of an objective diagnostic tool.
| Identifer | oai:union.ndltd.org:ADTP/215464 |
| Date | January 2007 |
| Creators | Clunas, Nathan, Psychiatry, Faculty of Medicine, UNSW |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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