Concealed Around-the-Ear EEG Captures Cognitive Processing in a Visual Simon Task.

Marlene Pacharra,Edmund Wascher,Stefan Debener

doi:10.3389/fnhum.2017.00290

Abstract

In theory, miniaturized systems such as the around-the-ear electrode arrays (cEEGrids) enable mobile monitoring of the electroencephalogram (EEG) in a variety of real life situations without interfering with the natural setting. However, the research benefit of such cEEGrid recordings critically depends on their validity. To investigate whether visual and motor processing are reflected in the cEEGrid-EEG, a direct comparison of EEG that was concurrently recorded with the cEEGrids and with a high-density cap setup was conducted. Thirteen participants performed a classic Simon task in which letters were presented laterally and a lateralized choice response was executed. N1, P1 and P300 event-related potential (ERP) waveforms were extracted from cEEGrid-EEG: they were found to be strongly correlated with corresponding waveforms extracted from cap-EEG but with lower signal strength and lower signal-to-noise-ratio (SNR). Event-related lateralizations (ERLs) recorded at posterior scalp sites were well reflected in middle cEEGrid pairs. Moreover, the effect size of the Simon correspondence effect on the extracted ERLs was similar between the two systems. However, lateralizations at central cap sites were less well reflected in the cEEGrid-EEG indicating a difficulty in capturing motor response preparation and execution. These results show that well-described visual and cognitive ERPs and ERLs can be measured using the cEEGrids, while motor-related cortical potentials are not well captured. This study further demonstrates the potential and possible limitations of unobtrusive cEEGrid-EEG recordings.

Highlights

Due to their size and limited portability, most brain imaging technologies are restricted to highly artificial and controlled laboratory conditions
Average correlation coefficients ranged from −0.79 to 0.64 with negative correlations found with outer cEEGrid electrodes and positive correlations with middle cEEGrid electrodes
Differences in signal strength are apparent between cap PO7/PO8 and cEEGrids: peak amplitudes for P1 were significantly higher when recorded at PO7/PO8 compared to cEEGrid L8, t(12) = 4.1, p = 0.001, and cEEGrid R4, t(12) = 3.7, p = 0.003

Summary

Introduction

Due to their size and limited portability, most brain imaging technologies are restricted to highly artificial and controlled laboratory conditions. Two further studies with a focus on auditory processing demonstrated the validity of cEEGrid-EEG for capturing auditory selective attention effects (Bleichner et al, 2016; Mirkovic et al, 2016). At present, it is not well known whether signals from other sensory modalities or motor processes are captured as well in cEEGrid-EEG. It is not well known whether signals from other sensory modalities or motor processes are captured as well in cEEGrid-EEG If this could be demonstrated, other applications for the cEEGridEEG — beyond auditory rehabilitation — would arise. Brain-computer-interfaces (BCI) as well as applications in neuroergonomics would benefit from the possibility of covertly and continuously monitoring neuronal activity (Mehta and Parasuraman, 2013)

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