Abstract
Electroencephalography (EEG) has emerged as a powerful tool for quantitatively studying the brain that enables natural and mobile experiments. Recent advances in EEG have allowed for the use of dry electrodes that do not require a conductive medium between the recording electrode and the scalp. The overall goal of this research was to gain an understanding of the overall usability and signal quality of dry EEG headsets compared to traditional gel-based systems in an unconstrained environment. EEG was used to collect Mobile Brain-body Imaging (MoBI) data from 432 people as they experienced an art exhibit in a public museum. The subjects were instrumented with either one of four dry electrode EEG systems or a conventional gel electrode EEG system. Each of the systems was evaluated based on the signal quality and usability in a real-world setting. First, we describe the various artifacts that were characteristic of each of the systems. Second, we report on each system's usability and their limitations in a mobile setting. Third, to evaluate signal quality for task discrimination and characterization, we employed a data driven clustering approach on the data from 134 of the 432 subjects (those with reliable location tracking information and usable EEG data) to evaluate the power spectral density (PSD) content of the EEG recordings. The experiment consisted of a baseline condition in which the subjects sat quietly facing a white wall for 1 min. Subsequently, the participants were encouraged to explore the exhibit for as long as they wished (piece-viewing). No constraints were placed upon the individual in relation to action, time, or navigation of the exhibit. In this freely-behaving approach, the EEG systems varied in their capacity to record characteristic modulations in the EEG data, with the gel-based system more clearly capturing stereotypical alpha and beta-band modulations.
Highlights
Technological advances in Mobile Brain-body Imaging (MoBI) technology allow the study of natural cognition and action in real-world complex environments
The spectral clustering for electrodes Fp1 (Figure 4) and Fp2 (Supplementary Materials) revealed a typical 1/f curve in the clusters that contain a majority of Power Spectral Density (PSD) associated with headsets BPG, Brain Products actiCAP Xpress (BPD), and M4S
The PSDs from M4S and BPD are grouped in the same cluster, with a 1/f shape in the curve
Summary
Technological advances in Mobile Brain-body Imaging (MoBI) technology allow the study of natural cognition and action in real-world complex environments. MoBI technology is expected to overcome technical constraints arising from limitations of traditional brain/body imaging modalities that restrict subjects to limited or no movement during cognitive or motor tasks. This restriction may contradict the very goal of such studies, which seek to elucidate the underlying neural activity “in action and in context” involved in natural human cognition or movement. It is imperative to deploy both hardware and software that allow for the simultaneous, reliable, and user-friendly recording of brain activity and body movements during mobile applications
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