High-frequency evoked oscillations during pitch and duration deviance detection are differentially altered in schizophrenia
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1
Institute of Psychology, University of Szeged, Hungary
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2
Department of Psychiatry, University of Szeged, Hungary
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3
Department of Cognitive Science, University of Technology and Economics, Hungary
INTRODUCTION:Impaired automatic context-dependent deviance detection as reflected by alterations of the mismatch negativity (MMN) auditory event related potential is a well-known deficit in schizophrenia. While it seems that both pitch (pMMN) and duration (dMMN) deviant MMNs are normal at illness onset, they show progressive amplitude reduction with dMMN being more sensitive to ongoing neurodegenerative changes. Despite the large literature on MMN, its underlying neural processes still remain controversial. Time-frequency analysis is an ideal tool for deconstructing event related brain activity into different frequency bands, where high-frequency oscillations (HFOs) in the beta and gamma frequency range are supposed to reflect network binding and have also been implicated in object representation. In healthy subjects, a shift from early evoked gamma (30-80 Hz) to beta 1 (12-20 Hz) activity can be observed during pitch deviancy detection (Haenschel et al., 2000). Given that several studies reported abnormal beta/gamma activity in schizophrenic patients, the aim of our study was to investigate whether pMMN and dMMN are characterized by similar HFO patterns and if they are altered in schizophrenia.
METHODSTwenty-seven DSM-IV schizophrenic patients and 22 matched healthy control subjects participated in the study. Standard (100 ms, 1000 Hz), pitch deviant (100 ms, 1500 Hz) and duration deviant (250 ms, 1000 Hz) tones were presented binaurally in a fixed 9:1 stimulus sequence. EEG was recorded with 19 scalp electrodes; time-frequency analysis was performed with complex Morlet wavelet analysis.
RESULTS:Both pMMN and dMMN showed significant amplitude reductions in the patient group. Regarding MMN latencies, no significant changes were observed, however, dMMN was slightly prolonged in the patient group (F=1.76, p=0.06). Wavelet analysis revealed three high-frequency oscillations (with peak amplitudes at 16, 30 and 40 Hz respectively) for pitch deviant and two (peak frequencies: 16 and 30 Hz) for duration deviant sounds. In the patient group right frontal beta1 (16 Hz) activity and frontocentral gamma2 (40 Hz) power was significantly reduced for pMMN, whereas right frontal gamma1 (30 Hz) decreased for dMMN.
DISCUSSION:According to our results, reduced pMMN in schizophrenia is accompanied by an altered gamma-to-beta shift, primarily over right frontal brain areas. This phenomenon is absent during duration deviancy detection in both groups, and dMMN is characterized by a decreased HFO centered at 30 Hz. The functional significance of these HFOs is rather speculative, but their better understanding might help in unraveling the neural mechanisms of auditory deviancy detection and its pathology in schizophrenia.
Conference:
MMN 09
Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009.
Presentation Type:
Poster Presentation
Topic:
Poster Presentations
Citation:
Csifcsak
G,
Domján
N,
Garab
E,
Szendi
I and
Janka
Z
(2009). High-frequency evoked oscillations during pitch and duration deviance detection are differentially altered in schizophrenia.
Conference Abstract:
MMN 09
Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications.
doi: 10.3389/conf.neuro.09.2009.05.065
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Received:
24 Mar 2009;
Published Online:
24 Mar 2009.
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Correspondence:
Gabor Csifcsak, Institute of Psychology, University of Szeged, Szeged, Hungary, gaborcsifcsak@yahoo.co.uk