scholarly journals tACS facilitates flickering driving by boosting steady-state visual evoked potentials

2021 ◽  
Vol 18 (6) ◽  
pp. 066042
Author(s):  
Bingchuan Liu ◽  
Xinyi Yan ◽  
Xiaogang Chen ◽  
Yijun Wang ◽  
Xiaorong Gao
Keyword(s):  
Steady State ◽  
Visual Stimulation ◽  
Signal To Noise Ratio ◽  
Human Subjects ◽  
Brain State ◽  
Healthy Human ◽  
Rhythmic Stimulation ◽  
Before And After ◽  
Transcranial Alternating Current Stimulation ◽  
Visual Evoked

Abstract Objective. There has become of increasing interest in transcranial alternating current stimulation (tACS) since its inception nearly a decade ago. tACS in modulating brain state is an active area of research and has been demonstrated effective in various neuropsychological and clinical domains. In the visual domain, much effort has been dedicated to brain rhythms and rhythmic stimulation, i.e. tACS. However, less is known about the interplay between the rhythmic stimulation and visual stimulation. Approach. Here, we used steady-state visual evoked potential (SSVEP), induced by flickering driving as a widely used technique for frequency-tagging, to investigate the aftereffect of tACS in healthy human subjects. Seven blocks of 64-channel electroencephalogram were recorded before and after the administration of 20min 10Hz tACS, while subjects performed several blocks of SSVEP tasks. We characterized the physiological properties of tACS aftereffect by comparing and validating the temporal, spatial, spatiotemporal and signal-to-noise ratio (SNR) patterns between and within blocks in real tACS and sham tACS. Main results. Our result revealed that tACS boosted the 10Hz SSVEP significantly. Besides, the aftereffect on SSVEP was mitigated with time and lasted up to 5 min. Significance. Our results demonstrate the feasibility of facilitating the flickering driving by external rhythmic stimulation and open a new possibility to alter the brain state in a direction by noninvasive transcranial brain stimulation.

scholarly journals Improved Spatial Resolution of Electroencephalogram Using Tripolar Concentric Ring Electrode Sensors

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Xiang Liu ◽  
Oleksandr Makeyev ◽  
Walter Besio
Keyword(s):  
Spatial Resolution ◽  
Signal To Noise Ratio ◽  
Human Subjects ◽  
Region Of Interest ◽  
Ring Electrode ◽  
Brain Diseases ◽  
Concentric Ring ◽  
Healthy Human ◽  
Good Spatial Resolution ◽  
Visual Evoked

The electroencephalogram (EEG) is broadly used for research of brain activities and diagnosis of brain diseases and disorders. Although EEG provides good temporal resolution of millisecond or less, it does not provide good spatial resolution. There are two main reasons for the poor spatial resolution: the blurring effects of the head volume conductor and poor signal-to-noise ratio. We have developed a tripolar concentric ring electrode (TCRE) Laplacian sensor and now report on computer simulations comparing spatial resolution between conventional EEG disc electrode sensors and TCRE Laplacian sensors. We also performed visual evoked stimulus experiments and acquired visual evoked potentials (VEPs) from healthy human subjects. From the simulations, we found that TCRE Laplacian sensors can provide approximately a tenfold improvement in spatial resolution and pass signals from specific volumes. Placing TCRE sensors near the brain region of interest will allow passage of the wanted signals and rejection of distant interference signals. We were also able to detect VEPs on the scalp surface and show that TCREs separated VEP sources better than conventional disc electrodes.

scholarly journals Distinct neural sources underlying visual word form processing as revealed by steady state visual evoked potentials (SSVEP)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fang Wang ◽  
Blair Kaneshiro ◽  
C. Benjamin Strauber ◽  
Lindsey Hasak ◽  
Quynh Trang H. Nguyen ◽  
...  
Keyword(s):  
Steady State ◽  
Word Recognition ◽  
Visual Word Recognition ◽  
Time Course ◽  
Signal To Noise Ratio ◽  
Visual Word ◽  
High Signal ◽  
Hierarchical Processing ◽  
Form Processing ◽  
Visual Evoked

AbstractEEG has been central to investigations of the time course of various neural functions underpinning visual word recognition. Recently the steady-state visual evoked potential (SSVEP) paradigm has been increasingly adopted for word recognition studies due to its high signal-to-noise ratio. Such studies, however, have been typically framed around a single source in the left ventral occipitotemporal cortex (vOT). Here, we combine SSVEP recorded from 16 adult native English speakers with a data-driven spatial filtering approach—Reliable Components Analysis (RCA)—to elucidate distinct functional sources with overlapping yet separable time courses and topographies that emerge when contrasting words with pseudofont visual controls. The first component topography was maximal over left vOT regions with a shorter latency (approximately 180 ms). A second component was maximal over more dorsal parietal regions with a longer latency (approximately 260 ms). Both components consistently emerged across a range of parameter manipulations including changes in the spatial overlap between successive stimuli, and changes in both base and deviation frequency. We then contrasted word-in-nonword and word-in-pseudoword to test the hierarchical processing mechanisms underlying visual word recognition. Results suggest that these hierarchical contrasts fail to evoke a unitary component that might be reasonably associated with lexical access.

scholarly journals Measurement of renal tissue oxygenation with blood oxygen level-dependent MRI and oxygen transit modeling

2014 ◽  
Vol 306 (6) ◽  
pp. F579-F587 ◽  
Author(s):  
Jeff L. Zhang ◽  
Glen Morrell ◽  
Henry Rusinek ◽  
Lizette Warner ◽  
Pierre-Hugues Vivier ◽  
...  
Keyword(s):  
Tissue Oxygenation ◽  
Human Subjects ◽  
Blood Oxygen Level Dependent ◽  
Renal Tissue ◽  
Blood Oxygen ◽  
Oxygen Level ◽  
Blood Oxygen Level ◽  
Healthy Human ◽  
Bold Mri ◽  
Before And After

Blood oxygen level-dependent (BOLD) MRI data of kidney, while indicative of tissue oxygenation level (Po2), is in fact influenced by multiple confounding factors, such as R2, perfusion, oxygen permeability, and hematocrit. We aim to explore the feasibility of extracting tissue Po2 from renal BOLD data. A method of two steps was proposed: first, a Monte Carlo simulation to estimate blood oxygen saturation (SHb) from BOLD signals, and second, an oxygen transit model to convert SHb to tissue Po2. The proposed method was calibrated and validated with 20 pigs (12 before and after furosemide injection) in which BOLD-derived tissue Po2 was compared with microprobe-measured values. The method was then applied to nine healthy human subjects (age: 25.7 ± 3.0 yr) in whom BOLD was performed before and after furosemide. For the 12 pigs before furosemide injection, the proposed model estimated renal tissue Po2 with errors of 2.3 ± 5.2 mmHg (5.8 ± 13.4%) in cortex and −0.1 ± 4.5 mmHg (1.7 ± 18.1%) in medulla, compared with microprobe measurements. After injection of furosemide, the estimation errors were 6.9 ± 3.9 mmHg (14.2 ± 8.4%) for cortex and 2.6 ± 4.0 mmHg (7.7 ± 11.5%) for medulla. In the human subjects, BOLD-derived medullary Po2 increased from 16.0 ± 4.9 mmHg (SHb: 31 ± 11%) at baseline to 26.2 ± 3.1 mmHg (SHb: 53 ± 6%) at 5 min after furosemide injection, while cortical Po2 did not change significantly at ∼58 mmHg (SHb: 92 ± 1%). Our proposed method, validated with a porcine model, appears promising for estimating tissue Po2 from renal BOLD MRI data in human subjects.

scholarly journals Association betweenFaecalibacterium prausnitziiand dietary fibre in colonic fermentation in healthy human subjects

2010 ◽  
Vol 104 (5) ◽  
pp. 693-700 ◽  
Author(s):  
Robin F. J. Benus ◽  
Tjip S. van der Werf ◽  
Gjalt W. Welling ◽  
Patricia A. Judd ◽  
Moira A. Taylor ◽  
...  
Keyword(s):  
Intestinal Microbiota ◽  
Dietary Fibre ◽  
Human Subjects ◽  
Healthy Human ◽  
Formulated Diets ◽  
Disease States ◽  
Before And After ◽  
Complex Ecosystem ◽  
Positive Correlations ◽  
Proportional Reduction

The intestinal microbiota are a complex ecosystem influencing the immunoregulation of the human host, providing protection from colonising pathogens and producing SCFA as the main energy source of colonocytes. Our objective was to investigate the effect of dietary fibre exclusion and supplementation on the intestinal microbiota and SCFA concentrations. Faecal samples were obtained from healthy volunteers before and after two 14 d periods of consuming formulated diets devoid or supplemented with fibre (14 g/l). The faecal microbiota were analysed using fluorescentin situhybridisation and SCFA were measured using GLC. There were large and statistically significant reductions in the numbers of theFaecalibacterium prausnitzii(P ≤ 0·01) andRoseburiaspp. (P ≤ 0·01) groups during both the fibre-free and fibre-supplemented diets. Significant and strong positive correlations between the proportion ofF. prausnitziiand the proportion of butyrate during both baseline normal diets were found (pre-fibre freer0·881,P = 0·001; pre-fibre supplementedr0·844,P = 0·002). A significant correlation was also found between the proportional reduction inF. prausnitziiand the proportional reduction in faecal butyrate during both the fibre-free (r0·806;P = 0·005) and the fibre-supplemented diet (r0·749;P = 0·013). These findings may contribute to the understanding of the association between fibre, microbiota and fermentation in health, during enteral nutrition and in disease states such as Crohn's disease.

The steady-state levels of oxidative DNA damage and of lipid peroxidation (F2-isoprostanes) are not correlated in healthy human subjects

2000 ◽  
Vol 32 (4) ◽  
pp. 355-362 ◽  
Author(s):  
Timothy England ◽  
Emily Beatty ◽  
Almas Rehman ◽  
Jaffar Nourooz-Zadeh ◽  
Paulo Pereira ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Dna Damage ◽  
Steady State ◽  
Oxidative Dna Damage ◽  
Human Subjects ◽  
Healthy Human ◽  
Healthy Human Subjects ◽  
Steady State Levels

DECODING OF STEADY-STATE VISUAL EVOKED POTENTIALS BY FRACTAL ANALYSIS OF THE ELECTROENCEPHALOGRAPHIC (EEG) SIGNAL

Fractals ◽  
2018 ◽  
Vol 26 (06) ◽  
pp. 1850092 ◽  
Author(s):  
HAMIDREZA NAMAZI ◽  
TIRDAD SEIFI ALA ◽  
HOVAGIM BAKARDJIAN
Keyword(s):  
Steady State ◽  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Fractal Structure ◽  
Visual Stimulation ◽  
Fractal Theory ◽  
Objective Assessment ◽  
Eeg Signal ◽  
Brain Response ◽  
Visual Evoked

Analysis of the brain response to different types of external stimuli has always been one of the major research areas in behavioral neuroscience. The electroencephalography (EEG) technique combined with different signal analysis approaches has been especially successful in revealing the detailed dynamic properties of the neural response to exogenous stimulation. In this analysis, we evaluated the nonlinear structure of the EEG signal using fractal theory in rest and visual stimulation (checkerboard reversal at 8, 14 and 28[Formula: see text]Hz). Our analysis showed a significant influence of stimulation on the fractal structure of EEG signal. On comparison between different conditions, 14-Hz steady-state visual evoked potentials (SSVEPs), previously shown to trigger an optimal brain response, exhibited the greatest influence on the complexity of the EEG signal. On the other hand, we observed the lowest complexity of EEG signal in the post-stimulation rest period. Statistical analysis confirmed significant differences in the fractal structure of the EEG signal between rest and different stimulation conditions. These findings demonstrate for the first time a direct relationship between the efficiency of brain processing and the complexity of the measured EEG signal, which could be employed for objective assessment and classification in various experimental paradigms.

Analyzing Steady-State Visual Evoked Potentials for Effective User Response Detection for Brain-Computer Interfaces

2013 ◽  
Author(s):  
Pouria Riyahi ◽  
Azim Eskandarian
Keyword(s):  
Steady State ◽  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Time Windows ◽  
Time Step ◽  
Response Detection ◽  
Source Signals ◽  
Visual Evoked

This article evaluates an M-order Adaptive Kalman filter analysis on Steady-State Visual Evoked Potentials (SSVEPs). This model is based on finding the original brain source signals from their combined observed EEG signals. At each time step, observed brain signals are filtered according to their ideal reference signals measured from 10, 11, 12 and 13 Hz LED stimuli. SSVEP response detection is based on maximum Signal to Noise Ratio (SNR) of the brain source signals. In each test, the average system accuracy is calculated with and without overlapped time-windows along with system Information Transfer Rate (ITR). The overall system accuracy and ITR are showing promising level of SSVEP detection for future online BCI systems.

Effects of Two Anticholinergic Drugs on Electroretinograms and Visual Evoked Potentials in Healthy Human Subjects

1990 ◽  
Vol 24 (4) ◽  
pp. 205-209 ◽  
Author(s):  
Peter Bartel ◽  
Marie Blom ◽  
Elna Robinson ◽  
C. van der Meyden ◽  
Klerk Sommers ◽  
...  
Keyword(s):  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Human Subjects ◽  
Anticholinergic Drugs ◽  
Healthy Human ◽  
Healthy Human Subjects ◽  
Visual Evoked

O3-induced change in bronchial reactivity to methacholine and airway inflammation in humans

1986 ◽  
Vol 60 (4) ◽  
pp. 1321-1326 ◽  
Author(s):  
J. Seltzer ◽  
B. G. Bigby ◽  
M. Stulbarg ◽  
M. J. Holtzman ◽  
J. A. Nadel ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Bronchoalveolar Lavage ◽  
Airway Inflammation ◽  
Bronchoalveolar Lavage Fluid ◽  
Human Subjects ◽  
Lavage Fluid ◽  
Airway Responsiveness ◽  
Airway Epithelial ◽  
Healthy Human ◽  
Before And After

The increase in airway responsiveness induced by O3 exposure in dogs is associated with airway epithelial inflammation, as evidenced by an increase in the number of neutrophils (polymorphonuclear leukocytes) found in epithelial biopsies and in bronchoalveolar lavage fluid. We investigated in 10 healthy, human subjects whether O3-induced hyperresponsiveness was similarly associated with airway inflammation by examining changes in the types of cells recovered in bronchoalveolar lavage fluid obtained after exposure to air or to O3 (0.4 or 0.6 ppm). We also measured the concentrations of cyclooxygenase and lipoxygenase metabolites of arachidonic acid in lavage fluid. We measured airway responsiveness to inhaled methacholine aerosol before and after each exposure and performed bronchoalveolar lavage 3 h later. We found more neutrophils in the lavage fluid from O3-exposed subjects, especially in those in whom O3 exposure produced an increase in airway responsiveness. We also found significant increases in the concentrations of prostaglandins E2, F2 alpha, and thromboxane B2 in lavage fluid from O3-exposed subjects. These results show that in human subjects O3-induced hyperresponsiveness to methacholine is associated with an influx of neutrophils into the airways and with changes in the levels of some cyclooxygenase metabolites of arachidonic acid.

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