Long-Term Test-Retest Reliability of Auditory Gamma Oscillations Between Different Clinical EEG Systems.

Shunsuke Tamura,Yoji Hirano,Toshiaki Onitsuka,Itta Nakamura

doi:10.3389/fpsyt.2020.00876

Shunsuke Tamura, Yoji Hirano + Show 2 more

Open Access

https://doi.org/10.3389/fpsyt.2020.00876

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Abstract

ObjectiveThere is increasing interest in the utility of gamma-band activity for assessing various brain functions, including perception, language, memory, and cognition. The auditory steady-state response (ASSR) involves neural activity in the brain elicited by trains of a click sound, and its maximum response is obtained at 40 Hz (40-Hz ASSR). Abnormalities of the 40-Hz ASSR are also widely reported in patients with schizophrenia. Thus, the test-retest reliability of the ASSR is important for its clinical and translational application. However, there are only limited studies reporting the short-term reliability between acquisitions at two time points made using the same electroencephalogram (EEG) system. Furthermore, the long-term reliability between multiple EEG systems and the reliability of spontaneous gamma activity are unknown but are crucial for multicenter collaborative research.MethodsWe examined the long-term test–retest reliability of 40-Hz ASSR oscillatory activities indexed by the phase locking factor (PLF), evoked power, and (non-phase-locked) induced power between two clinical 19-electrode EEG systems [recorded twice for EEG-1 (time1 and time2) and EEG-2 (time3 and time4)] at four time points from 14 healthy controls over a duration of 5 months. Test-retest reliability was examined using intraclass correlation coefficients (ICCs).ResultsBoth PLF and evoked power showed good to excellent ICCs (>0.60), mainly in the Fz-electrode, both within each EEG system—EEG-1 [(time1 vs. time2) PLF: ICC = 0.66, evoked power: ICC = 0.88] and EEG-2 [(time3 vs. time4) PLF: ICC = 0.82, evoked power: ICC = 0.77]—and between the two EEG systems [(EEG-1 vs. EEG-2) PLF: ICC = 0.73, evoked power: ICC = 0.84]. In contrast, induced power showed the highest (excellent) ICC between the two EEG systems (ICC = 0.95) mainly in the Cz-electrode. For PLF, the Fz-electrode showed better test-retest reliability across all EEG recordings than the Cz-electrode (Fz: ICC = 0.67, Cz: ICC = 0.63), whereas we found similar excellent reproducibility across all EEG recordings from both electrodes for evoked power (Fz: ICC = 0.79, Cz: ICC = 0.77) and induced power (Fz: ICC = 0.79, Cz: ICC = 0.80).ConclusionThe 40-Hz ASSR oscillatory activities, including induced power, showed excellent test-retest reliability, even when using different EEG systems over a duration of 5 months. These findings confirm the utility of the 40-Hz ASSR as a reliable clinical and translatable biomarker for multicenter collaborative research.

Highlights

Gamma-band (30−100 Hz) neural oscillations are implicated in normal perception, cognition, and memory, while recent empirical studies suggest that gamma-band activity is disrupted in patients with schizophrenia [1]
The distribution of the 40-Hz auditory steady-state response (ASSR) activity topography was largely similar at the four different time points
The induced powers in the gamma range measured by EEG-1 seemed to be smaller than those measured by EEG-2

Summary

Introduction

Gamma-band (30−100 Hz) neural oscillations are implicated in normal perception, cognition, and memory, while recent empirical studies suggest that gamma-band activity is disrupted in patients with schizophrenia [1]. The gammaaminobutyric acid (GABA) transmission system plays an important role in gamma-band oscillations, and GABAergic interneurons, especially GABAergic parvalbumin-expressing interneurons, can control the firing timing of pyramidal neurons [2]. The reciprocal balance between excitability and inhibition is essential for the generation of gamma-band activity [4]. Normal neuronal information processes rely on a functional excitability/inhibitory balance (E/I-balance), while failure to maintain this balance is hypothesized to cause abnormalities in gamma-band activity in patients with schizophrenia. Such abnormalities may be the neurophysiological basis of sensory processing deficits in this disorder [5, 6]. Among the neural oscillation indices, the auditory steady-state response (ASSR), which can elicit strong synchronous activities with the corresponding stimulus frequency during constant click sounds, is useful in evaluating gamma-band activity [7]

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