Patrique Fiedler

Technische Universität Ilmenau | TUI · Institut für Biomedizinische Technik und Informatik

Background EEG may be affected by artefacts hindering the analysis of brain signals. Data-driven methods like independent component analysis (ICA) are successful approaches to remove artefacts from the EEG. However, the ICA-based methods developed so far are often affected by limitations, such as: the need for visual inspection of the separated ind...

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...

Objective: The aim of the present study was to elucidate the brain dynamics underlying the maintenance of a constant force level exerted during a visually guided isometric contraction task by optimizing a predictive multivariate model based on global and spectral brain dynamics features. Approach: Electroencephalography (EEG) was acquired in eig...

The cognitive performance of the crew has a major impact on mission safety and success in space flight. Monitoring of cognitive performance during long-duration space flight therefore is of paramount importance and can be performed using compact state-of-the-art mobile EEG. However, signal quality of EEG may be compromised due to the vicinity to va...

Investigating the neural mechanisms underlying both cooperative and competitive joint actions may have a wide impact in many social contexts of human daily life. An effective pipeline of analysis for hyperscanning data recorded in a naturalistic context with a cooperative and competitive motor task has been missing. We propose an analytical pipelin...

Evaluations of new dry, high-density EEG caps have only been performed so far with serial measurements and not with simultaneous (parallel) measurements. For a first comparison of gel-based and dry electrode performance in simultaneous high-density EEG measurements, we developed a new EEG cap comprising 64 gel-based and 64 dry electrodes and perfor...

A novel multimodal experimental setup and dyadic study protocol were designed to investigate the neurophysiological underpinnings of joint action through the synchronous acquisition of EEG, ECG, EMG, respiration and kinematic data from two individuals engaged in ecologic and naturalistic cooperative and competitive joint actions involving face-to-f...

Dry electroencephalography (EEG) electrodes provide rapid, gel-free, and easy EEG preparation, but with limited wearing comfort. We propose a novel dry electrode comprising multiple tilted pins in a flower-like arrangement. The novel Flower electrode increases wearing comfort and contact area while maintaining ease of use. In a study with 20 volunt...

Electroencephalography (EEG) can detect changes in cerebral activity during spaceflight. This study evaluates the effect of spaceflight on brain networks through analysis of the Default Mode Network (DMN)'s alpha frequency band power and functional connectivity (FC), and the persistence of these changes. Five astronauts' resting state EEGs under th...

Extensive evidence supports the notion that physical activity (PA) promotes healthy aging and contributes to the prevention of brain damage and dementia. However, there are relevant differences in individual response to exercise that could mediate the extent of the PA‐induced benefits. Here, we propose the application of the novel technology that i...

Dry electrodes for electroencephalography (EEG) allow new fields of application, including telemedicine, mobile EEG, emergency EEG, and long-term repetitive measurements for research, neurofeedback, or brain–computer interfaces. Different dry electrode technologies have been proposed and validated in comparison to conventional gel-based electrodes....

Due to the direct contact between electrode and scalp, dry EEG electrodes are exposed to increased mechanical wear compared to conventional gel-based electrodes. However, state-of-the-art commercial cap systems commonly use permanently fixated electrodes which can lead to downtime of the EEG cap during professional repair and replacement as well as...

DC potential shifts are the shifts observed in the EEG baseline which can last from seconds to minutes. The significance of these low-frequency components in healthy as well as pathological states of human physiology is getting more and more attention not only in scientific research but also in clinical applications. In this paper, we present our n...

Electroencephalography (EEG) is widely used in clinical applications and basic research. Dry EEG opened the application area to new fields like self-application during gaming and neurofeedback. While recording, the signals are always affected by artefacts. Manual detection of bad channels is the gold standard in both gel-based and dry EEG but is ti...

In a new era for digital health, dry electrodes for biopotential measurement enable the monitoring of essential vital functions outside of specialized healthcare centers. In this paper, a new type of nanostructured titanium-based thin film is proposed, revealing improved biopotential sensing performance and overcoming several of the limitations of...

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...

Current developments towards multipin, dry electrodes in electroencephalography (EEG) are promising for applications in non-laboratory environments. Dry electrodes do not require the application of conductive gel, which mostly confines the use of gel EEG systems to the laboratory environment. The aim of this study is to validate soft, multipin, dry...

Dry electrodes enable a shorter preparation time for infant EEG. Since infant skin is more sensitive than adult skin, soft electrodes are required to reduce the mechanical stress for this sensitive skin. Thus, soft electrodes are crucial for eventual repetitive and long-term use like in neonatal intensive care units. A biocompatible polyurethane (P...

Wearable electronics and sensors are increasingly popular for personal health monitoring, including smart shirts containing electrocardiography (ECG) electrodes. Optimal electrode performance requires careful selection of the electrode position. On top of the electrophysiological aspects, practical aspects must be considered due to the dynamic reco...

Monitoring brain activity at home using electroencephalography (EEG) is an increasing trend for both medical and non-medical applications. Gel-based electrodes are not suitable due to the gel application requiring extensive preparation and cleaning support for the patient or user. Dry electrodes can be applied without prior preparation by the patie...

Electrodes of silver/silver chloride (Ag/AgCl) are dominant in clinical settings for surface electromyography (sEMG) recordings. These electrodes need a conductive electrolyte gel to ensure proper performance, which dries during long-term measurements inhibiting the immediate electrode’s reuse and is often linked to skin irritation episodes. To ove...

Novel state-of-the-art amplifier and cap systems enable Electroencephalography (EEG) recording outside of stationary lab systems during physical exercise and body motion. However, extensive preparation time, cleaning, and limited long-term stability of conventional gel-based electrode systems pose significant limitations in out-of-the-lab condition...

Measuring the heart rate of animals is an important area of research which can be applied to numerous analyses. In this work we evaluate the performance of two dry contact electrocardiogram (ECG) electrode structures for monitoring the heart rate of domestic pets. The aim was to improve the operation of previously evaluated electrodes with some mod...

The functionality of three dry electrocardiogram electrode constructions was evaluated by measuring canine heart rate during four different behaviors: Standing, sitting, lying and walking. The testing was repeated (n = 9) in each of the 36 scenarios with three dogs. Two of the electrodes were constructed with spring-loaded test pins while the third...

Neuromodulation induced by transcranial electric stimulation (TES) exhibited promising potential for clinical practice. However, the underlying mechanisms remain subject of research. The combination of TES and electroencephalography (EEG) offers great potential for investigating these mechanisms and brain function in general, especially when perfor...

Background and Objectives Current developments in electroencephalography (EEG) foster medical and nonmedical applications outside the hospitals. For example, continuous monitoring of mental and cognitive states can contribute to avoid critical and potentially dangerous situations in daily life. An important prerequisite for successful EEG at home i...

Data contamination due to physiological artifacts such as those generated by eyeblinks, eye movements, and muscle activity continues to be a central concern in the acquisition and analysis of electroencephalographic (EEG) data. This issue is further compounded in EEG sports science applications where the presence of artifacts is notoriously difficu...

Dry and gel-based (“wet”) electrode montages worn by participants during training data acquisitions (a,b) and during cycling data acquisitions (c,d).

In state-of-the-art Electroencephalography (EEG) Silver/Silver-Chloride electrodes are applied together with electrolyte gels or pastes. Their application requires extensive preparation, trained medical staff and limits measurement time and mobility. We recently proposed a novel multichannel cap system for dry EEG electrodes for mobile and out-of-t...

Statistical performance of the ten SVMs trained to classify eyeblinks The statistical performance of the individual SVM classifiers trained to classify ICs containing eyeblinks is reported separately for the wet and dry testing EEG datasets and for the three decomposition levels (20, 50 and 80 ICs).

Descriptive statistics of individual features in eye movement fingerprints Descriptive statistics of the individual features of the reference and non-artifactual fingerprints for eye movements are given separately for wet and dry EEG datasets.

Groups of training and testing datasets Composition of the groups of EEG datasets used to train and test each SVM classifier for each artifact. Training and testing groups include wet and dry EEG datasets. Each dataset is identified only by the number. The type of artifact and electrode can be inferred from the position in the table. Datasets used...

Statistical performance of the ten SVMs trained to classify cardiac interference The statistical performance of the individual SVM classifiers trained to classify ICs containing cardiac interference is reported separately for the wet and dry testing EEG datasets and for the three decomposition levels (20, 50 and 80 ICs).

Descriptive statistics of individual features in eyeblink fingerprints Descriptive statistics of the individual features of the reference and non-artifactual fingerprints for eyeblinks are given separately for wet and dry EEG datasets.

Descriptive statistics of individual features in myogenic artifact fingerprints Descriptive statistics of the individual features of the reference and non-artifactual fingerprints for myogenic artifacts are given separately for wet and dry EEG datasets.

Descriptive statistics of individual features in cardiac interference fingerprints Descriptive statistics of the individual features of the reference and non-artifactual fingerprints for cardiac interference are given separately for wet and dry EEG datasets.

Layout of the caps used for EEG acquisitions Layout of the caps used for EEG acquisitions: (A) the novel dry electrode cap with 97 dry Multipin Polyurethane electrodes with an Ag/AgCl coating, arranged in an equidistant layout; (B) the commercial wet cap (Waveguard, Advanced Neuro Technologies B.V., Enschede, Netherlands) with 128 Ag/AgCl electrode...

Statistical performance of the ten SVMs trained to classify eye movements The statistical performance of the individual SVM classifiers trained to classify ICs containing eye movements is reported separately for the wet and dry testing EEG datasets and for the three decomposition levels (20, 50 and 80 ICs).

Statistical performance of the ten SVMs trained to classify myogenic artifacts The statistical performance of the individual SVM classifiers trained to classify ICs containing myogenic artifacts is reported separately for the wet and dry testing EEG datasets and for the three decomposition levels (20, 50 and 80 ICs).

SNR values of individual EEG datasets before and after artifact removal Panel 1: For each artifact type, we report the average SNR values of the filtered EEG signals and of the artifact-free EEG signals for the individual datasets used to test the SVM classifier with the best performance. For each dataset, the SNR is calculated on the representativ...

Multichannel Electroencephalography (EEG) is widely used in clinical neurology and neuroscientific research. EEG caps with 64 wet Silver/Silver-Chloride (Ag/AgCl) electrodes represent an often-used standard in the field. Reproducible electrode-skin contact for these electrodes is ensured by electrolyte gel or paste. Thus, these electrodes require s...

Physical head phantoms allow the assessment of source reconstruction procedures in electroencephalography and electrical stimulation profiles during transcranial electric stimulation. Volume conduction in the head is strongly influenced by the skull, which represents the main conductivity barrier. Realistic modeling of its characteristics is thus i...

A novel quasi-dry electrode prototype, based on a polymer wick structure filled with a specially designed hydrating solution is proposed for electroencephalography (EEG) applications. The new electrode does not require the use of a conventional electrolyte paste to achieve a wet, low-impedance scalp contact. When compared to standard commercial Ag/...

We propose a novel alginate based hydrogel as an alternative to the traditional EEG electrolytic gels. The new product is injected into the electrode cap cavities in the form of a viscous liquid, just like a commercial electrolytic gel, but it forms a solid and homogeneous hydrogel shortly after application. The solid hydrogel substantially reduces...

Electrode and cap concepts for continuous and ubiquitous monitoring of brain activity will open up new fields of application and contribute to increased use of electroencephalography (EEG) in clinical routine, neurosciences, brain-computer-interfacing and out-of-the-lab monitoring. However, mobile and unobtrusive applications are currently hindered...

Several plasma treatments using argon, oxygen, and nitrogen are studied in order to increase the interfacial adhesion of the polyurethane/Ag:TiN system to be used as biopotential electrodes. The optimized plasma treatments conditions (100 W, 15 min, regardless of the gas) promote a steep decrease of the water contact angle values. The observed chem...

Current usage of electroencephalography (EEG) is limited to laboratory environments. Self-application of a multichannel wet EEG caps is practically impossible, since the application of state-of-the-art wet EEG sensors requires trained laboratory staff. We propose a novel EEG cap system with multipin dry electrodes overcoming this problem. We descri...

Important requirements for the analysis of multichannel EEG data are efficient techniques for signal enhancement, signal decomposition, feature extraction, and dimensionality reduction. We propose a new approach for spatial harmonic analysis (SPHARA) that extends the classical spatial Fourier analysis to EEG sensors positioned non-uniformly on the...

A potential new area of routine application for electroencephalography (EEG) is the brain‐computer interface, which might enable disabled people to interact with their environment, based on measured brain signals. However, conventional electroencephalography is not suitable here due to limitations arising from complicated, time‐consuming and error‐...

The present work reports on the development of a novel polymer-based electrode prototype for electroencephalography (EEG). The new electrode concept lies between the classic "wet" and "dry" electrodes, allowing addressing most of their drawbacks, while keeping the advantages of both. A localized skin hydration effect at the electrode/scalp contact...

Conventional Silver/Silver-Chloride electrodes are inappropriate for routine high-density EEG and emerging new fields of application like brain computer interfaces. A novel multipin electrode design is proposed. It enables rapid and easy application while maintaining signal quality and patient comfort. The electrode design is described and impedanc...