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Event-Related EEG Time-Frequency Analysis: An Overview of Measures and An Analysis of Early Gamma Band Phase Locking in Schizophrenia

Mental Health Service, VAMC, San Francisco, CA 94121, USA.
Schizophrenia Bulletin (Impact Factor: 8.61). 10/2008; 34(5):907-26. DOI: 10.1093/schbul/sbn093
Source: PubMed

ABSTRACT An increasing number of schizophrenia studies have been examining electroencephalography (EEG) data using time-frequency analysis, documenting illness-related abnormalities in neuronal oscillations and their synchronization, particularly in the gamma band. In this article, we review common methods of spectral decomposition of EEG, time-frequency analyses, types of measures that separately quantify magnitude and phase information from the EEG, and the influence of parameter choices on the analysis results. We then compare the degree of phase locking (ie, phase-locking factor) of the gamma band (36-50 Hz) response evoked about 50 milliseconds following the presentation of standard tones in 22 healthy controls and 21 medicated patients with schizophrenia. These tones were presented as part of an auditory oddball task performed by subjects while EEG was recorded from their scalps. The results showed prominent gamma band phase locking at frontal electrodes between 20 and 60 milliseconds following tone onset in healthy controls that was significantly reduced in patients with schizophrenia (P = .03). The finding suggests that the early-evoked gamma band response to auditory stimuli is deficiently synchronized in schizophrenia. We discuss the results in terms of pathophysiological mechanisms compromising event-related gamma phase synchrony in schizophrenia and further attempt to reconcile this finding with prior studies that failed to find this effect.

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Available from: Daniel H Mathalon, Aug 30, 2015
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    • "Coherence indices are the most widely used measures of EEG interregional functional connectivity. There are several ways to compute coherence (Chorlian et al. 2009; Roach & Mathalon, 2008) but it is generally computed based on the time-frequency cross-spectra between two time-series, reflecting not only synchronization of phase but also amplitude of the EEG signal. Unlike this conventional computation of coherence, phase coherence is isolated to the phase relationships of two signals and excludes amplitude information, thus it provides a measure of functional connectivity uncontaminated by signal strength (Lachaux et al., 1999; Aviyente et al., 2011). "
    12/2015; 1(1). DOI:10.1186/s40810-015-0009-5
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    • "Wilcoxon signed-rank test Mann–Whitney U-test Parameter Band SCH Patients Controls SCH Versus controls θ p > 0.1 p = 0.0402 p = 0.0963 α p > 0.1 p = 0.0730 p > 0.1 WC β 1 p > 0.1 p > 0.1 p > 0.1 β 2 p > 0.1 p = 0.0467 p = 0.0963 γ p > 0.1 p > 0.1 p > 0.1 θ p > 0.1 p = 0.0281 p = 0.0448 α p > 0.1 p = 0.0992 p > 0.1 PLV β 1 p > 0.1 p = 0.0289 p > 0.1 β 2 p > 0.1 p = 0.0281 p = 0.0448 γ p > 0.1 p > 0.1 p > 0.1 θ p > 0.1 p = 0.0045 p = 0.0019 α p > 0.1 p = 0.0010 p > 0.1 ED β 1 p > 0.1 p = 0.0187 p > 0.1 β 2 p > 0.1 p = 0.0010 p > 0.1 γ p > 0.1 p = 0.0045 p > 0.1 (Schmiedt et al 2005, Roach and Mathalon 2008, Hirano et al 2008, Bachiller et al 2014 "
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    ABSTRACT: Objective. The aim of this research is to explore the coupling patterns of brain dynamics during an auditory oddball task in schizophrenia (SCH). Approach. Event-related electroencephalographic (ERP) activity was recorded from 20 SCH patients and 20 healthy controls. The coupling changes between auditory response and pre-stimulus baseline were calculated in conventional EEG frequency bands (theta, alpha, beta-1, beta-2 and gamma), using three coupling measures: coherence, phase-locking value and Euclidean distance. Main results. Our results showed a statistically significant increase from baseline to response in theta coupling and a statistically significant decrease in beta-2 coupling in controls. No statistically significant changes were observed in SCH patients. Significance. Our findings support the aberrant salience hypothesis, since SCH patients failed to change their coupling dynamics between stimulus response and baseline when performing an auditory cognitive task. This result may reflect an impaired communication among neural areas, which may be related to abnormal cognitive functions.
    Journal of Neural Engineering 12/2014; 12(1):016007. DOI:10.1088/1741-2560/12/1/016007 · 3.42 Impact Factor
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    • "power) and fire in synchrony with other regions (i.e. phase-locking and phase coherence; Roach and Mathalon, 2008) can be used to index DMN connectivity. "
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    ABSTRACT: This study assessed whether individual differences in self-oriented neural processing were associated with performance perceptions of minority students under stereotype threat. Resting electroencephalographic activity recorded in white and minority participants was used to predict later estimates of task errors and self-doubt on a presumed measure of intelligence. We assessed spontaneous phase-locking between dipole sources in left lateral parietal cortex (LPC), precuneus/posterior cingulate cortex (P/PCC), and medial prefrontal cortex (MPFC); three regions of the default mode network (DMN) that are integral for self-oriented processing. Results revealed that minorities with greater LPC-P/PCC phase-locking in the theta band reported more accurate error estimations. All individuals experienced less self-doubt to the extent they exhibited greater LPC-MPFC phase-locking in the alpha band but this effect was driven by minorities. Minorities also reported more self-doubt to the extent they overestimated errors. Findings reveal novel neural moderators of stereotype threat effects on subjective experience. Spontaneous synchronization between DMN regions may play a role in anticipatory coping mechanisms that buffer individuals from stereotype threat.
    Social Cognitive and Affective Neuroscience 11/2014; 10(7). DOI:10.1093/scan/nsu145 · 5.88 Impact Factor
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