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. 2021 May:231:73-81.
doi: 10.1016/j.schres.2021.03.007. Epub 2021 Mar 27.

Abnormal phase discontinuity of alpha- and theta-frequency oscillations in schizophrenia

Daisuke Koshiyama  1 , Makoto Miyakoshi  2 , Kumiko Tanaka-Koshiyama  1 , Yash B Joshi  3 , Joyce Sprock  3 , David L Braff  3 , Gregory A Light  3
Affiliations

Abnormal phase discontinuity of alpha- and theta-frequency oscillations in schizophrenia

Daisuke Koshiyama et al. Schizophr Res. 2021 May.

Abstract

Background: Schizophrenia patients have abnormal electroencephalographic (EEG) power over multiple frequency bands, even at rest, though the primary neural generators and spatiotemporal dynamics of these abnormalities are largely unknown. Disturbances in the precise synchronization of oscillations within and across cortical sources may underlie abnormal resting-state EEG activity in schizophrenia patients.

Methods: A novel assessment method was applied to identify the independent contributing sources of resting-state EEG and assess the phase discontinuity in schizophrenia patients (N = 148) and healthy subjects (N = 143).

Results: A network of 11 primary contributing sources of scalp EEG was identified in both groups. Schizophrenia patients showed abnormal elevations of EEG power in the temporal region in the theta, beta, and gamma-bands, as well as the posterior cingulate gyrus in the delta, theta, alpha, and beta-bands. The higher theta-band power in the middle temporal gyrus was significantly correlated with verbal memory impairment in patients. The peak frequency of alpha was lower in patients in the cingulate and temporal regions. Furthermore, patients showed a higher rate of alpha phase discontinuity in the temporal region as well as a lower rate of theta phase discontinuity in the temporal and posterior cingulate regions.

Conclusions: Abnormal rates of phase discontinuity of alpha- and theta-band, abnormal elevations of EEG power in multiple bands, and a lower peak frequency of alpha were identified in schizophrenia patients at rest. Clarification of the mechanistic substrates of abnormal phase discontinuity may clarify core pathophysiologic abnormalities of schizophrenia and contribute to the development of novel biomarkers for therapeutic interventions.

Keywords: Alpha oscillation; Phase discontinuity; Resting-state electroencephalography (EEG); Schizophrenia; Source level analysis; Theta oscillation.

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Conflict of interest statement

Declaration of competing interest G.A. Light reported consulting for Astellas Pharma, Inc., Heptares Therapeutics, NeuroSig, Neurocrine, and Novartis.

Figures

Figure 1
Figure 1
Procedures of the source-level EEG analysis. Abbreviation: EEG, electroencephalogram; ICs, independent components; ICA, independent component analysis.
Figure 2
Figure 2. Phase Discontinuity Index.
Phase Discontinuity Index is a ratio of (large phase change between segment t and segment t+1)/(small phase change between segment t and segment t+1).
Figure 3
Figure 3. EEG band power in 11 estimated source locations.
The power spectral density of healthy subjects and schizophrenia patients in 11 estimated source locations is shown. The significant difference of EEG band power between the groups was colored (p < 0.05, a false discovery rate corrected). Blue or red color shade along the power spectral density indicates a standard error in patients with schizophrenia and healthy comparison subjects, respectively. Abbreviation: Ant, anterior; EEG, electroencephalogram; L, left; Mid, middle; Post, posterior; R, right; Supp, supplementary.
Figure 4
Figure 4. Phase Discontinuity Indices (PDI) that are significantly different between patients with schizophrenia and healthy comparison subjects.
The black horizontal line indicates the means of the PDI. Asterisks indicate a statistically significant difference in PDI between patients with schizophrenia and healthy comparison subjects (p < 0.05, a false discovery rate corrected). Abbreviation: A, anterior; HCS, healthy comparison subjects; L, left; Mid, middle; P, posterior; R, right; Supp, supplementary; SZ, schizophrenia.
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