Flex-printed forehead EEG sensors (fEEGrid) for long-term EEG acquisition

Abstract

Objective. In this report we present the fEEGrid, an electrode array applied to the forehead that allows convenient long-term recordings of electroencephalography (EEG) signals over many hours. Approach. Twenty young, healthy participants wore the fEEGrid and completed traditional EEG paradigms in two sessions on the same day. The sessions were eight hours apart, participants performed the same tasks in an early and a late session. For the late session fEEGrid data were concurrently recorded with traditional cap EEG data. Main results. Our analyses show that typical event-related potentials responses were captured reliably by the fEEGrid. Single-trial analyses revealed that classification was possible above chance level for auditory and tactile oddball paradigms. We also found that the signal quality remained high and impedances did not deteriorate, but instead improved over the course of the day. Regarding wearing comfort, all participants indicated that the fEEGrid was comfortable to wear and did not cause any pain even after 8 h of wearing it. Significance. We show in this report, that high quality EEG signals can be captured with the fEEGrid reliably, even in long-term recording scenarios and with a signal quality that may be considered suitable for online brain-computer Interface applications.

Flex-Printed Ear-EEG Sensors for Adequate Sleep Staging at Home

“…To improve on the design, extending the electrode array to include near-eye positions, or possibly emulating EOG by using two cEEGrids (one on each ear) and cross-referencing between the two may be advantageous ( 22 ). A recent adaptation of the cEEGrid to flex-printed forehead EEG delivered high-quality EEG signals of forehead and facial positions with minimal discomfort or inconvenience over the course of 8 h ( 32 ). Encompassing standard EOG positions in the grid, this electrode array may provide a signal suitable for detection of REM, though it has not been tested for wear during sleep.…”

The Arch Electrode: A Novel Dry Electrode Concept for Improved Wearing Comfort

“…Novel electrode technologies are critical directions of research for signal quality improvement, rapid, and prolonged biopotential measurements. Screen- or flex-printed dry composite electrodes have been proposed and successfully validated for applications with low hair density, including electrocardiography ( Chlaihawi et al, 2018 ), electromyography ( Pani et al, 2019 ) and below-hairline EEG ( Bleichner and Debener, 2017 ; Blum et al, 2020 ). Furthermore, design alternatives have been proposed to overcome the problems of the electrolyte gels at hairy areas of the head.…”

Optimal Versus Approximate Channel Selection Methods for EEG Decoding With Application to Topology-Constrained Neuro-Sensor Networks

“…While using a large number of electrodes allows to record at a high spatial resolution, such high-density recordings also come with several disadvantages; they require more expensive equipment, they lead to longer set-up times, they require more data storage/processing, and the higher dimensionality may cause overfitting in data-driven algorithms. Furthermore, when making the transition towards wearable EEG applications with devices that measure EEG during daily-life activities [3]- [8] [9], [10], a low channel count is important for miniaturization and to minimize power and bandwidth requirements [10], [11]. Therefore, there is a need for efficient and robust data-driven channel selection or electrode placement methods to reduce the number of EEG channels while having minimal impact on the application performance.…”

“…While channel selection can be done post-hoc to reduce the dimensionality of the data, it can also be used for electrode placement in a context of wearable EEG. Considerable research is ongoing to make wearable miniature-EEG (mini-EEG) devices which allow to record EEG 24/7 in daily-life activities [3]- [8]. Although these mini-EEG devices only cover small skin areas due to their far-driven miniaturization, the concept of neuro-sensor networks enables the simultaneous use of multiple such mini-EEG devices connected wirelessly thereby increasing the spatial resolution [10], [19].…”