Design and Characterization of an EEG-Hat for Reliable EEG Measurements

Kawana, Takumi; Yoshida, Yuri; Kudo, Yuta; Iwatani, Chiho; Miki, Norihisa

doi:10.3390/mi11070635

Cited by 11 publications

(9 citation statements)

References 56 publications

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“…Limitations of the current cap and electrode systems will be further investigated and addressed in future studies. The reduced mechanical flexibility of the dry electrode cap, as well as the adduction requirements of the electrodes (Fiedler et al, 2018;Kawana, Yoshida, Kudo, Iwatani, & Miki, 2020;Kimura et al, 2020)…”

Section: Discussionmentioning

confidence: 99%

“…, require finer grading of the cap sizes for fabric caps or the development of alternative, dedicated cap systems addressing both aspects. Persons with very thick hair (i.e., high hair density and/or hair follicle diameter) may require adapted electrode designs in terms of electrode pin length, density, or orientation Kawana et al, 2020. studied hair occupancy and orientation, reporting considerable inter-and intraindividual differences suggesting further electrode design optimization.…”

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confidence: 99%

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A high‐density 256‐channel cap for dry electroencephalography

Fiedler

Fonseca

Supriyanto

et al. 2021

Human Brain Mapping

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High-density electroencephalography (HD-EEG) is currently limited to laboratory environments since state-of-the-art electrode caps require skilled staff and extensive preparation. We propose and evaluate a 256-channel cap with dry multipin electrodes for HD-EEG. We describe the designs of the dry electrodes made from polyurethane and coated with Ag/AgCl. We compare in a study with 30 volunteers the novel dry HD-EEG cap to a conventional gel-based cap for electrode-skin impedances, resting state EEG, and visual evoked potentials (VEP). We perform wearing tests with eight electrodes mimicking cap applications on real human and artificial skin. Average impedances below 900 kΩ for 252 out of 256 dry electrodes enables recording with state-of-the-art EEG amplifiers. For the dry EEG cap, we obtained a channel reliability of 84% and a reduction of the preparation time of 69%. After exclusion of an average of 16% (dry) and 3% (gel-based) bad channels, resting state EEG, alpha activity, and pattern reversal VEP can be recorded with less than 5% significant differences in all compared signal characteristics metrics. Volunteers reported wearing comfort of 3.6 ± 1.5 and 4.0 ± 1.8 for the dry and 2.5 ± 1.0 and 3.0 ± 1.1 for the gel-based cap prior and after the EEG recordings, respectively (scale 1-10).Wearing tests indicated that up to 3,200 applications are possible for the dry electrodes. The 256-channel HD-EEG dry electrode cap overcomes the principal limitations of HD-EEG regarding preparation complexity and allows rapid application by not medically trained persons, enabling new use cases for HD-EEG.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

A high‐density 256‐channel cap for dry electroencephalography

Fiedler

Fonseca

Supriyanto

et al. 2021

Human Brain Mapping

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“…Furthermore, when re-applying the Arch electrode caps on the same volunteer, the preparation time of Multipin-shaped and Arch-shaped electrodes was comparable. The initial preparation time may be reduced by ensuring an initial orientation of the electrodes at each head region according to the most common hair orientation ( Kawana et al, 2020 ). Therefore, the Arch electrodes are specifically suited for headsets and head caps intended for repetitive application by the same user, e.g., for BCI and neurofeedback.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2021

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Electroencephalography (EEG) is increasingly used for repetitive and prolonged applications like neurofeedback, brain computer interfacing, and long-term intermittent monitoring. Dry-contact electrodes enable rapid self-application. A common drawback of existing dry electrodes is the limited wearing comfort during prolonged application. We propose a novel dry Arch electrode. Five semi-circular arches are arranged parallelly on a common baseplate. The electrode substrate material is a flexible thermoplastic polyurethane (TPU) produced by additive manufacturing. A chemical coating of Silver/Silver-Chloride (Ag/AgCl) is applied by electroless plating using a novel surface functionalization method. Arch electrodes were manufactured and validated in terms of mechanical durability, electrochemical stability, in vivo applicability, and signal characteristics. We compare the results of the dry arch electrodes with dry pin-shaped and conventional gel-based electrodes. 21-channel EEG recordings were acquired on 10 male and 5 female volunteers. The tests included resting state EEG, alpha activity, and a visual evoked potential. Wearing comfort was rated by the subjects directly after application, as well as at 30 min and 60 min of wearing. Our results show that the novel plating technique provides a well-adhering electrically conductive and electrochemically stable coating, withstanding repetitive strain and bending tests. The signal quality of the Arch electrodes is comparable to pin-shaped dry electrodes. The average channel reliability of the Arch electrode setup was 91.9 ± 9.5%. No considerable differences in signal characteristics have been observed for the gel-based, dry pin-shaped, and arch-shaped electrodes after the identification and exclusion of bad channels. The comfort was improved in comparison to pin-shaped electrodes and enabled applications of over 60 min duration. Arch electrodes required individual adaptation of the electrodes to the orientation and hairstyle of the volunteers. This initial preparation time of the 21-channel cap increased from an average of 5 min for pin-like electrodes to 15 min for Arch electrodes and 22 min for gel-based electrodes. However, when re-applying the arch electrode cap on the same volunteer, preparation times of pin-shaped and arch-shaped electrodes were comparable. In summary, our results indicate the applicability of the novel Arch electrode and coating for EEG acquisition. The novel electrode enables increased comfort for prolonged dry-contact measurement.

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“…Either the initial impedance or the time spent to reach a stable impedance was less than that of the long hair subjects. According to [41], the amount of hair between the scalp and the electrode does affect the impedance values. Thus, it is best to push aside the hair before placing the PreG electrode to decrease the impedance and the stable period.…”

Section: A Contact Impedancementioning

confidence: 99%

A Pre-Gelled EEG Electrode and Its Application in SSVEP-Based BCI

Zhang²,

Zha³

et al. 2022

IEEE Trans. Neural Syst. Rehabil. Eng.

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Electroencephalogram (EEG) electrodes are critical devices for brain-computer interface and neurofeedback. A pre-gelled (PreG) electrode was developed in this paper for EEG signal acquisition with a short installation time and good comfort. A hydrogel probe was placed in advance on the Ag/AgCl electrode before wearing the EEG headband instead of a time-consuming gel injection after wearing the headband. The impedance characteristics were compared between the PreG electrode and the wet electrode. The PreG electrode and the wet electrode performed the Brain-Computer Interface (BCI) application experiment to evaluate their performance. The average impedance of the PreG electrode can be decreased to 43 k or even lower, which is higher than the wet electrode with an impedance of 8 k. However, there is no significant difference in classification accuracy and information transmission rate (ITR) between the PreG electrode and the wet electrode in a 40 target BCI system based on Steady State Visually Evoked Potential (SSVEP). This study validated the efficiency of the proposed PreG electrode in the SSVEP-based BCI. The proposed PreG electrode will be an excellent substitute for wet electrodes in an actual application with convenience and good comfort.

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Design and Characterization of an EEG-Hat for Reliable EEG Measurements

Cited by 11 publications

References 56 publications

A high‐density 256‐channel cap for dry electroencephalography

A high‐density 256‐channel cap for dry electroencephalography

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

A Pre-Gelled EEG Electrode and Its Application in SSVEP-Based BCI

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