Evidence for dysregulated high-frequency oscillations during sensory processing in medication-naïve, first episode
Limin Sun1, Nazareth Castellanos, Christine Grützner
1Department of Neurophysiology, Max-Planck Institute for Brain Research, Deutschordenstr, 46, Frankfurt am Main, 60528, Germany; Department of Radiology, Massachusetts General Hospital, Harvard University, Cambridge, MA 02129, USA.
Introduction:
High-frequency oscillations are important for sensory processing and dysfunctions in the amplitude and synchrony of beta- and gamma-band oscillations have been demonstrated in schizophrenia (ScZ). However, the presence of aberrant high-frequency oscillations in first-episode (FE), medication-naive patients during sensory processing is unclear.
Methods:
Magnetoencephalographic (MEG) data were recorded from 15 never-medicated, FE-ScZ patients and 20 matched healthy controls during the perception of Mooney faces. MEG data were analysed for spectral power and single-sensor phase-locking in the beta (13-25Hz) and gamma- (25-140Hz) frequency range.
Results:
FE-ScZ patients were characterized by significantly impaired sensory processing as indicated by a reduced discrimination index (A'). Impaired behavioural performance in ScZ-patients was accompanied by decreased spectral power in the high- (60-120Hz) gamma-band range. In contrast, oscillations in the lower (25-60Hz) gamma-band were largely intact and beta-band oscillations were increased. Analysis of cross-frequency coupling showed a reduced correlation between 60 and 120Hz amplitude values and beta-band power in FE-ScZ-patients relative to controls.
Discussion:
Our findings show that impaired sensory processing in medication-naive, FE-schizophrenia is related to a dysregulation of neural oscillations which involves both an impairment in the generation of high gamma-band activity as well as a failure to downregulate task-irrelevant beta-band activity. Because of the interrelationship of these dysfunctions and the role of inhibitory networks in the shaping of high-frequency activity, aberrant neural oscillations in FE-schizophrenia may be linked to dysfunctions in the excitation-inhibition (E/I)-balance.
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