Frontal and parietal EEG alpha asymmetry: a large-scale investigation of short-term reliability on distinct EEG systems

Dorothea Metzen,Stephan Getzmann,Mauro F Larra,Erhan Genç,Edmund Wascher,Sebastian Ocklenburg

doi:10.1007/s00429-021-02399-1

Abstract

EEG resting-state alpha asymmetry is one of the most widely investigated forms of functional hemispheric asymmetries in both basic and clinical neuroscience. However, studies yield inconsistent results. One crucial prerequisite to obtain reproducible results is the reliability of the index of interest. There is a body of research suggesting a moderate-to-good reliability of EEG resting-state alpha asymmetry, but unfortunately sample sizes in these studies are typically small. This study presents the first large-scale short-term reliability study of frontal and parietal EEG resting-state alpha asymmetry. We used the Dortmund Vital Study data set containing 370 participants. In each participant, EEG resting state was recorded eight times, twice with their eyes opened, twice with their eyes-closed, each on two different EEG systems. We found good reliability of EEG alpha power and alpha asymmetry on both systems for electrode pairs. We also found that alpha power asymmetry reliability is higher in the eyes-closed condition than in the eyes-open condition. The frontomedial electrode pair showed weaker reliability than the frontolateral and parietal electrode pairs. Interestingly, we found no population-level alpha asymmetry in frontal electrodes, one of the most investigated electrode sites in alpha asymmetry research. In conclusion, our results suggest that while EEG alpha asymmetry is an overall reliable measure, frontal alpha asymmetry should be assessed using multiple electrode pairs.

Highlights

Researchers have investigated frontal EEG alpha band (8–13 Hz) asymmetry and its role in psychopathology, motivation, and personality (Allen et al 2018; Davidson et al 1979; Gable et al 2018; Harmon-Jones and Gable 2018; Reznik and Allen 2018)
One crucial requirement for replicability of associations between EEG alpha asymmetries and cognitive or clinical variables is a high reliability of the alpha asymmetry laterality quotient (LQ)
While a body of previous research on EEG alpha asymmetry reliability exists, most studies rely on rather small sample sizes

Summary

Introduction

Researchers have investigated frontal EEG alpha band (8–13 Hz) asymmetry and its role in psychopathology, motivation, and personality (Allen et al 2018; Davidson et al 1979; Gable et al 2018; Harmon-Jones and Gable 2018; Reznik and Allen 2018). Relatively higher right to left alpha power has commonly been interpreted as relatively higher left to right activity, and vice versa (Reznik and Allen 2018). To determine the extent of individual EEG alpha asymmetry, a laterality quotient (LQ) is calculated by subtracting left alpha power from right alpha power (ln[R] − ln[L]) (Reznik and Allen 2018). This way, positive LQ values represent higher relative right alpha power (left activity), while negative LQ values represent higher relative left alpha power (right activity). The amount of EEG alpha activity in the brain is influenced by the eye-status of the participant. EEG alpha activity is more pronounced when eyes are closed than

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