scholarly journals Ultra-conformal skin electrodes with synergistically enhanced conductivity for long-time and low-motion artifact epidermal electrophysiology

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yan Zhao ◽  
Song Zhang ◽  
Tianhao Yu ◽  
Yan Zhang ◽  
Guo Ye ◽  
...  
Keyword(s):  
Brain Activity ◽  
Motion Artifact ◽  
Polystyrene Sulfonate ◽  
Facial Skin ◽  
Electrical Stability ◽  
Molecular Ordering ◽  
Electrophysiological Signals ◽  
Long Time ◽  
High Degree ◽  
Enhanced Conductivity

AbstractAccurate and imperceptible monitoring of electrophysiological signals is of primary importance for wearable healthcare. Stiff and bulky pregelled electrodes are now commonly used in clinical diagnosis, causing severe discomfort to users for long-time using as well as artifact signals in motion. Here, we report a ~100 nm ultra-thin dry epidermal electrode that is able to conformably adhere to skin and accurately measure electrophysiological signals. It showed low sheet resistance (~24 Ω/sq, 4142 S/cm), high transparency, and mechano-electrical stability. The enhanced optoelectronic performance was due to the synergistic effect between graphene and poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), which induced a high degree of molecular ordering on PEDOT and charge transfer on graphene by strong π-π interaction. Together with ultra-thin nature, this dry epidermal electrode is able to accurately monitor electrophysiological signals such as facial skin and brain activity with low-motion artifact, enabling human-machine interfacing and long-time mental/physical health monitoring.

scholarly journals Ultra-Conformal Skin Electrodes with Synergistically Enhanced Conductivity for Low-Motion Artifact Epidermal Electrophysiology

2020 ◽  
Author(s):  
Yan Zhao ◽  
Song Zhang ◽  
Tianhao Yu ◽  
Yan Zhang ◽  
Guo Ye ◽  
...  
Keyword(s):  
Electrochemical Impedance ◽  
Chemical Vapor ◽  
Motion Artifact ◽  
Electrical Stability ◽  
Dry Electrodes ◽  
Molecular Ordering ◽  
Electrophysiological Signals ◽  
Grown Graphene ◽  
Electrophysiological Signal ◽  
High Degree

Abstract Accurate and imperceptible monitoring of electrophysiological signals is of primary importance for wearable healthcare. Stiff and bulky pregelled electrodes are now commonly used in clinical diagnosis, causing severe discomfort to users as well as artifact signals in motion. Here, we report a ~ 100 nm ultrathin dry epidermal electrode that is able to conformably adhere to skin and accurately measure electrophysiological signals. This dry epidermal electrode was fabricated by direct transfer of Chemical Vapor Deposition (CVD) - grown graphene (~ 1 nm) by poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS, ~ 100 nm) as the transfer medium, namely PTG. It showed low sheet resistance (45 Ω/sq), high transparency (80%), and mechano-electrical stability. The enhanced optoelectronic performance was due to the synergistic effect between graphene and PEDOT:PSS, which induced a high degree of molecular ordering on PEDOT and charge transfer on graphene by strong π-π interaction. Together with ultra-thin nature, PTG exhibited a low electrochemical impedance when interfacing with skin, thereby leading to accurate electrophysiological signal detection with low motion artifact, as well as controlling robotic claws. This strategy to synergistically incorporate graphene and PEDOT:PSS together as ultra-conformal dry electrodes will have a significant impact on the development of epidermal electronics.

An Adaptive and Learning System for Feedback-Controlled Evoked Response Studies

1981 ◽  
Vol 20 (03) ◽  
pp. 169-173
Author(s):  
J. Wagner ◽  
G. Pfurtscheixer
Keyword(s):  
Brain Activity ◽  
Evoked Response ◽  
Learning System ◽  
Time Interval ◽  
Electrical Brain Activity ◽  
Long Time ◽  
The Subject ◽  
Eeg Power ◽  
Stimulation System ◽  
Background Eeg

The shape, latency and amplitude of changes in electrical brain activity related to a stimulus (Evoked Potential) depend both on the stimulus parameters and on the background EEG at the time of stimulation. An adaptive, learnable stimulation system is introduced, whereby the subject is stimulated (e.g. with light), whenever the EEG power is subthreshold and minimal. Additionally, the system is conceived in such a way that a certain number of stimuli could be given within a particular time interval. Related to this time criterion, the threshold specific for each subject is calculated at the beginning of the experiment (preprocessing) and adapted to the EEG power during the processing mode because of long-time fluctuations and trends in the EEG. The process of adaptation is directed by a table which contains the necessary correction numbers for the threshold. Experiences of the stimulation system are reflected in an automatic correction of this table. Because the corrected and improved table is stored after each experiment and is used as the starting table for the next experiment, the system >learns<. The system introduced here can be used both for evoked response studies and for alpha-feedback experiments.

Quantitative evaluation of slow fluctuations of the volume of liquids inside cranial cavity

2019 ◽  
pp. 51-63 ◽  
Author(s):  
Yu. E. Moskalenko ◽  
T. I. Kravchenko ◽  
Yu. V. Novozhilova
Keyword(s):  
Brain Activity ◽  
Sampling Rate ◽  
Age Groups ◽  
Pulse Amplitude ◽  
Cranial Cavity ◽  
Current Frequency ◽  
Physiological Indicators ◽  
Physiological Phenomenon ◽  
Long Time ◽  
Manned Space

Introduction. Slow fl uctuations in the volume and pressure of liquids in the cranial cavity have been known for a long time and have been studied for more than 100 years. However, their quantitative indicators and their practical signifi cance remain unclear until now due to the diffi culties of research. Nevertheless, it was found that they were connected with the brain activity, which made it possible to use them as one of the physiological indicators in studying the problems of manned space fl ights. Goal of research — to study the possibility of using spectral analysis of slow fl uctuations of the volume of liquids inside the cranium in order to realize the quantitative assessment of their indicators with the use of modern microelectronics and computer technology.Materials and methods. In order to solve this problem we created a complex, in which rheoencephalograph-RG-01 («Mizar») was used as a converter-modulator of physiological signals into electrical oscillations. The device was connected with the ADC (Firm «ADIstrument»), Its software allows to calculate the spectrogram with a sampling rate of 128 kHz. Studies were conducted on volunteers of younger, middle and older age groups. The respiratory rate and the electrocardiography were registered together with the rheoencephalography. Electrodes were fi xed on the volonteers′ fronto-mastoid area.Results. Slow fl uctuations the cranium representan independent physiological phenomenon. The most considerable and valuable were fl uctuations in 0,1–0,3 Hz. It was found that current frequency of 100 or 200 kHz and frequency for quantization of 80–100 kHz was optimal for performing their spectrograms. The structure of such diagram consists of 4–7 peaks with amplitude of 0,4–0,7 units compared with REG pulse amplitude. They depend on age and are characterized by hemispheric asymmetry. Spectral diagrams of slow fl ucation inside cranium are representing inpendent physiological phenomenon. These fl uctuations are not connected by common origin, with heart activity and respiration. They are connected by nature with brain activity and PRM.Conclusion. Can be an informative method for diagnostic and assessment of general status of osteopathic patients well as for the assessment of mechanisms of action of some osteopathic techniques.

scholarly journals The Neural Basis of Vivid Memory Is Patterned on Perception

2012 ◽  
Vol 24 (9) ◽  
pp. 1867-1883 ◽  
Author(s):  
Bradley R. Buchsbaum ◽  
Sabrina Lemire-Rodger ◽  
Candice Fang ◽  
Hervé Abdi
Keyword(s):  
Brain Activity ◽  
Sensory Perception ◽  
Direct Perception ◽  
Neural Basis ◽  
Activation Patterns ◽  
Short Video ◽  
Initial Perception ◽  
Experiential Quality ◽  
High Degree

When we have a rich and vivid memory for a past experience, it often feels like we are transported back in time to witness once again this event. Indeed, a perfect memory would exactly mimic the experiential quality of direct sensory perception. We used fMRI and multivoxel pattern analysis to map and quantify the similarity between patterns of activation evoked by direct perception of a diverse set of short video clips and the vivid remembering, with closed eyes, of these clips. We found that the patterns of distributed brain activation during vivid memory mimicked the patterns evoked during sensory perception. Using whole-brain patterns of activation evoked by perception of the videos, we were able to accurately classify brain patterns that were elicited when participants tried to vividly recall those same videos. A discriminant analysis of the activation patterns associated with each video revealed a high degree (explaining over 80% of the variance) of shared representational similarity between perception and memory. These results show that complex, multifeatured memory involves a partial reinstatement of the whole pattern of brain activity that is evoked during initial perception of the stimulus.

PINPOINT SOURCE LOCALIZATION FOR OCULAR NONSELECTIVE ATTENTION WITH COMBINATION OF ERP AND fNIRI MEASUREMENTS

2008 ◽  
Vol 01 (02) ◽  
pp. 195-206 ◽  
Author(s):  
TING LI ◽  
LI LI ◽  
PENG DU ◽  
QINGMING LUO ◽  
HUI GONG
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Brain Activity ◽  
Event Related Potential ◽  
Reliable Technique ◽  
Brain Mechanism ◽  
Electrophysiological Signals ◽  
Series Of Experiments ◽  
A New Technique ◽  
Hemodynamic Information

Compared with event-related potential (ERP) which is widely used in psychology research, functional near-infrared imaging (fNIRI) is a new technique providing hemodynamic information related to brain activity, except for electrophysiological signals. Here, we use both these techniques to study ocular attention. We conducted a series of experiments with a classic paradigm of ocular nonselective attention, and monitored responses with fNIRI and ERP respectively. The results showed that fNIRI measured brain activations in the left prefrontal lobe, while ERPs showed activation in frontal lobe. More importantly, only with the combination measurements of fNIRI and ERP, we were then able to find the pinpoint source of ocular nonselective attention, which is in the left and upper corner in Brodmann area 10. These results demonstrated that fNIRI is a reliable technique in psychology, and the combination of fNIRI and ERP can be promising to reveal more information in the research of brain mechanism.

scholarly journals Beta-band desynchronization reflects uncertainty in effector selection during motor planning

2021 ◽  
Author(s):  
Milou J.L. van Helvert ◽  
Leonie Oostwoud Wijdenes ◽  
Linda Geerligs ◽  
W. Pieter Medendorp
Keyword(s):  
Time Window ◽  
Brain Activity ◽  
Motor Planning ◽  
Reaction Times ◽  
Motor Preparation ◽  
Motion Artifact ◽  
Theta Band ◽  
Beta Band ◽  
Target Uncertainty ◽  
Band Power

AbstractWhile beta-band activity during motor planning is known to be modulated by uncertainty about where to act, less is known about its modulations to uncertainty about how to act. To investigate this issue, we recorded oscillatory brain activity with EEG while human participants (n = 17) performed a hand choice reaching task. The reaching hand was either predetermined or of participants’ choice, and the target was close to one of the two hands or at about equal distance from both. To measure neural activity in a motion-artifact-free time window, the location of the upcoming target was cued 1000-1500 ms before the presentation of the target, whereby the cue was valid in 50% of trials. As evidence for motor planning during the cueing phase, behavioral observations showed that the cue affected later hand choice. Furthermore, reaction times were longer in the choice than in the predetermined trials, supporting the notion of a competitive process for hand selection. Modulations of beta-band power over central cortical regions, but not alpha-band or theta-band power, were in line with these observations. During the cueing period, reaches in predetermined trials were preceded by larger decreases in beta-band power than reaches in choice trials. Cue direction did not affect reaction times or beta-band power, which may be due to the cue being invalid in 50% of trials, retaining effector uncertainty during motor planning. Our findings suggest that effector uncertainty, similar to target uncertainty, selectively modulates beta-band power during motor planning.New & NoteworthyWhile reach-related beta-band power in central cortical areas is known to modulate with the number of potential targets, here we show, using a cueing paradigm, that the power in this frequency band, but not in the alpha or theta-band, is also modulated by the uncertainty of which hand to use. This finding supports the notion that multiple possible effector-specific actions can be specified in parallel up to the level of motor preparation.

scholarly journals Low-frequency unsteadiness in the wake of a normal flat plate

1998 ◽  
Vol 370 ◽  
pp. 101-147 ◽  
Author(s):  
F. M. NAJJAR ◽  
S. BALACHANDAR
Keyword(s):  
Shear Layer ◽  
Flat Plate ◽  
Free Stream ◽  
Low Frequency ◽  
Separated Flow ◽  
Phase Mismatch ◽  
Streamwise Vortices ◽  
Long Time ◽  
Drag And Lift ◽  
High Degree

The separated flow past a zero-thickness flat plate held normal to a free stream at Re=250 has been investigated through numerical experiments. The long-time signatures of the drag and lift coefficients clearly capture a low-frequency unsteadiness with a period of approximately 10 times the primary shedding period. The amplitude and frequency of drag and lift variations during the shedding process are strongly modulated by the low frequency. A physical interpretation of the low-frequency behaviour is that the flow gradually varies between two different regimes: a regime H of high mean drag and a regime L of low mean drag. It is observed that in regime H the shear layer rolls up closer to the plate to form coherent spanwise vortices, while in regime L the shear layer extends farther downstream and the rolled-up Kármán vortices are less coherent. In the high-drag regime three-dimensionality is characterized by coherent Kármán vortices and reasonably well-organized streamwise vortices connecting the Kármán vortices. With a non-dimensional spanwise wavelength of about 1.2, the three-dimensionality in this regime is reminiscent of mode-B three-dimensionality. It is observed that the high degree of spanwise coherence that exists in regime H breaks down in regime L. Based on detailed numerical flow visualization we conjecture that the formation of streamwise and spanwise vortices is not in perfect synchronization and that the low-frequency unsteadiness is the result of this imbalance (or phase mismatch).

scholarly journals Fast and Accurate Finite Transducer Analysis Method for Wireless Passive Impedance-Loaded SAW Sensors

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3988
Author(s):  
Wei Luo ◽  
Yang Yuan ◽  
Yi Wang ◽  
Qiuyun Fu ◽  
Hui Xia ◽  
...  
Keyword(s):  
Computation Time ◽  
Processing Unit ◽  
Bulk Wave ◽  
Analysis Method ◽  
Accurate Analysis ◽  
Central Processing ◽  
Finite Transducer ◽  
Long Time ◽  
High Degree ◽  
Element Method

An accurate and fast simulation tool plays an important role in the design of wireless passive impedance-loaded surface acoustic wave (SAW) sensors which have received much attention recently. This paper presents a finite transducer analysis method for wireless passive impedance-loaded SAW sensors. The finite transducer analysis method uses a numerically combined finite element method-boundary element method (FEM/BEM) model to analyze non-periodic transducers. In non-periodic transducers, FEM/BEM was the most accurate analysis method until now, however this method consumes central processing unit (CPU) time. This paper presents a faster algorithm to calculate the bulk wave part of the equation coefficient which usually requires a long time. A complete non-periodic FEM/BEM model of the impedance sensors was constructed. Modifications were made to the final equations in the FEM/BEM model to adjust for the impedance variation of the sensors. Compared with the conventional method, the proposed method reduces the computation time efficiently while maintaining the same high degree of accuracy. Simulations and their comparisons with experimental results for test devices are shown to prove the effectiveness of the analysis method.

scholarly journals Expectations, Coordination Failures and Macro Crises

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Daniel Heymann ◽  
Juan Pablo Brichetti ◽  
Pedro Juarros ◽  
Gustavo Montero
Keyword(s):  
Rational Expectations ◽  
Central Element ◽  
Critical Periods ◽  
Social Concern ◽  
Coordination Failures ◽  
Economic Changes ◽  
Macroeconomic Analysis ◽  
The People ◽  
Long Time ◽  
High Degree

AbstractDeep recessions and disruptions in credit markets have caused social concern and motivated research for a long time. They still challenge macroeconomic analysis. We map some observable features of a set of such episodes, trying to find common elements of the whole family of events. The different macroeconomic experiences show a high degree of heterogeneity. Given that, what emerges as a central element of crises is their character as a life-changing episode for the people concerned, which remains in their memory and triggers a search for lessons, as they frustrate past expectations and force widespread reevaluations of wealth and income prospects. Critical periods involve dynamics at different time scales, as economic changes with lasting implications take place in an environment of dramatic day-to-day variability. Crises tend to be associated with breaks in the growth trends of the economies in question, in a way that may surprise not only agents inclined to eccentric behavior, but also those who held beliefs based on prevalent economic analysis. Macroeconomic disturbances of this sort raise strong questions about the pertinence, and the logic, of usual rational expectations assumptions and modeling practices. These issues are briefly discussed in an opening section.

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