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: 8.45). 10/2008; 34(5):907-26. DOI: 10.1093/schbul/sbn093
Source: PubMed


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,
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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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    • "Similarly, recent research using advanced methods for time-frequency analysis of event-related oscillations (EROs) has provided evidence that ERP waveforms can be at least partially accounted for by phase resetting of EEG oscillations (Freunberger et al. , 2007, Freunberger et al. , 2008, Gruber et al. , 2005, Klimesch et al. , 2007, Klimesch et al. , 2004, Sauseng and Klimesch, 2008, Yeung et al. , 2004, Yeung et al. , 2007). It has also been demonstrated that averaged ERPs provide limited representation of the underlying event-related neural dynamics, whereas ERO analysis permits the separation of phase and amplitude effects of different frequencies that contribute to the averaged ERP waveform and therefore provide important insights into the neural dynamics underlying the ERP response (Fell et al. , 2004, Makeig et al. , 2004, Makeig et al. , 2002, Onton and Makeig, 2006, Roach and Mathalon, 2008). Another advantage of ERO analyses is the potential for transfer of knowledge obtained by the analysis of spontaneous EEG to findings of ERP research and vice versa (e.g., Button et al. , 2007), thereby facilitating the understanding of how different cortical networks are integrated in response to an external stimulus and how information can be transferred between such circuits (e.g., Carr et al. , 2004), as well as dissociating cognitive processes which were not dissociable by ERPs (e.g., Branchey et al. , 1988, see for review Sauseng and Klimesch, 2008). "
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    ABSTRACT: Higher impulsivity observed in alcoholics is thought to be due to neurocognitive functional deficits involving impaired inhibition in several brain regions and/or neuronal circuits. Event-related Oscillations (EROs) offer time-frequency measure of brain rhythms during perceptual and cognitive processing, which provide a detailed view of neuroelectric oscillatory responses to external/internal events. The present study examines evoked power (temporally locked to events) of oscillatory brain signals in alcoholics during an equal probability Go/NoGo task, assessing their functional relevance in execution and inhibition of a motor response. The current study hypothesized that increases in the power of slow frequency bands and their topographical distribution is associated with tasks that have increased cognitive demands, such as the execution and inhibition of a motor response. Therefore, it is hypothesized that alcoholics would show lower spectral power in their topographical densities compared to controls. The sample consisted of 20 right-handed abstinent alcoholic males and 20 age and gender-matched healthy controls. Evoked delta (1.0-3.5Hz; 200-600ms), theta (4.0-7.5Hz; 200-400ms), slow alpha (8.0-9.5Hz; 200-300ms), and fast alpha (10.0-12.5Hz; 100-200ms) ERO power were compared across group and task conditions. Compared to controls, alcoholics had higher impulsiveness scores on the Barrett Impulsiveness Scale (BIS-11) and made more errors on Go trials. Alcoholics showed significantly lower evoked delta, theta, and slow alpha power compared to controls for both Go and NoGo task conditions, and lower evoked fast alpha power compared to controls for only the NoGo condition. The results confirm previous findings and are suggestive of neurocognitive deficits while executing and suppressing a motor response. Based on findings in the alpha frequency ranges, it is further suggested that the inhibitory processing impairments in alcoholics may arise from inadequate early attentional processing with respect to the stimulus related aspects/semantic memory processes, which may be reflected in lower posterio-temporal evoked fast alpha power. It can thus be concluded that alcoholics show neurocognitive deficits in both execution and suppression of a motor response and inadequate early attentional processing with respect to the semantic memory/stimulus related aspects while suppressing a motor response.
    Progress in Neuro-Psychopharmacology and Biological Psychiatry 10/2015; 65. DOI:10.1016/j.pnpbp.2015.10.002 · 3.69 Impact Factor
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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 · 3.30 Impact Factor
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