scholarly journals Examining the effects of free gaze and dynamic video stimuli on engagement, eye movements, and EEG signal quality in a visual aesthetic rating task

2021 ◽  
Author(s):  
Dominik Welke ◽  
Edward A. Vessel
Keyword(s):  
Eye Movements ◽  
Signal To Noise Ratio ◽  
Significant Loss ◽  
Signal Quality ◽  
Blink Rate ◽  
Eeg Signal ◽  
Rating Task ◽  
Experimental Conditions ◽  
Neurophysiological Studies ◽  
Fixation Task

Free gaze and the use of dynamically changing video stimuli are typically avoided in EEG exper- iments to avoid artefacts and confounds related to uncontrolled eye movements. Yet, often it is unclear whether these artificial secondary manipulations might have unwanted effects on the pri- mary measures of interest and for a growing number of research questions removing them would be beneficial: Among those is the investigation of visual aesthetic experiences, which typically involve open-ended exploration of highly variable stimuli. Here we aimed to quantify the effect of fixation task and using still vs. movie stimuli on EEG signal quality and several behavioral and physiological measures of interest during an aesthetic rating task. Participants observed scenes from landscapes and dance performances and rated each stimulus for both aesthetic appeal and their state of boredom while watching it. The scenes were presented either as dynamic video clips or static pictures, and participants observed them either with unconstrained gaze or under attempted fixation We recorded EEG, ECG and eyetracking from 43 participants. An auditory stream of 40Hz amplitude modulated pink noise was played during each trial and signal-to-noise-ratio (SNR) of the auditory steady-state response measured at the scalp was extracted as a proxy measure for overall EEG signal quality. The study including hypotheses and a priori power analysis was preregistered. We found that both behavioral ratings were influenced by the experimental conditions: boredom and aesthetic ratings were positively affected by dynamic video stimuli, indicating that these are experienced as more engaging; both these effects were stronger in dance. As already reported before, landscape stimuli were experienced as more appealing. Fixaton task, on the other hand, had no significant effect on the ratings which is encouraging given how canonically it is applied. Eye movements were significantly affected not only by viewing task, but by stimulus dynamics and content as well: we observed fewer eyeblinks, saccades and microsaccades in video stimuli, and fewer saccades but more microsaccades in dance than in landscape stimuli, with several significant interactions. EEG SNR, to our surprise, was barely affected by fixation task - despite only minimal preprocessing and no trial rejection. We nevertheless believe that the new metric is sensitive to capture noise: it was significantly correlated with the number of eye blinks, and after cleaning the dataset with an ICA based preprocessing pipeline the significant effect of fixation task and the correlation with blink rate vanished. We see these as promising results indicating that at least in the lab more liberal experimental conditions could be achieved without significant loss of signal quality. Specifically the use of dynamic video material bears a lot of potential for future investigations in human neurophysiological studies.

Differences in perception and memory for speech fragments in complex versus simple words

2020 ◽  
Vol 15 (2) ◽  
pp. 189-222
Author(s):  
Anne Pycha
Keyword(s):  
Signal To Noise Ratio ◽  
Rating Task ◽  
Signal To Noise ◽  
Eye Fixation ◽  
Complex Word ◽  
Complex Versus ◽  
Spoken Words ◽  
Fixation Task ◽  
Noise Ratio ◽  
Visual Shape

Abstract Two experiments investigated how people perceived and remembered fragments of spoken words that either corresponded to correct lexical entries (as in the complex word drink-er) or did not (as in the simple word glitt-er). Experiment 1 was a noise-rating task that probed perception. Participants heard stimuli such drinker, where strikethrough indicates noise overlaid at a controlled signal-to-noise ratio, and rated the loudness of the noise. Results showed that participants rated noise on certain pseudo-roots (e.g., glitter) as louder than noise on true roots ( drinker), indicating that they perceived them with less clarity. Experiment 2 was an eye-fixation task that probed memory. Participants heard a word such as drink-er while associating each fragment with a visual shape. At test, they saw the shapes again, and were asked to look at the shape associated with a particular fragment, such as drink. Results showed that fixations to shapes associated with pseudo-affixes (-er in glitter) were less accurate than fixations to shapes associated with true affixes (-er in drinker), which suggests that they remembered the pseudo-affixes more poorly. These findings provide evidence that the presence of correct lexical entries for roots and affixes modulates people’s judgments about the speech that they hear.

scholarly journals Removing Artifacts From Eeg Signal Using Wavelet Transform and Conventional Filters

2021 ◽  
Vol 15 ◽  
pp. 172-177
Author(s):  
Meryem Felja ◽  
Asmae Bencheqroune ◽  
Mohammed Karim ◽  
Ghita Bennis
Keyword(s):  
Wavelet Transform ◽  
Eye Movements ◽  
Wavelet Transforms ◽  
Signal To Noise Ratio ◽  
Eeg Signal ◽  
Mean Square ◽  
Signal To Noise ◽  
Common Criteria ◽  
Electroencephalogram Eeg ◽  
The Brain

Electroencephalogram (EEG) is a signal of an electrical nature reflecting the neuronal activities of the brain. It is used for the diagnosis of certain cerebral pathologies. However, it becomes more difficult to identify and analyze it when it is corrupted by artifacts of non-cerebral origin such as eye movements, cardiac activities ..., therefore, it is essential to remove these parasitic signals. In literature, there are different techniques for removing artifacts. This paper proposes and discusses a new EEG de-noising technique, based on a combination of wavelet transforms and conventional filters. The results of the proposed method are evaluated using three common criteria: signal-to-noise-ratio (SNR), mean square error (MSE) and cross correletion function (CCF). These experimental results demonstrate that the proposed approach can be an effective tool for removing artifact without suppression of any signal components.

scholarly journals Optimization of Deep Architectures for EEG Signal Classification: An AutoML Approach Using Evolutionary Algorithms

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2096
Author(s):  
Diego Aquino-Brítez ◽  
Andrés Ortiz ◽  
Julio Ortega ◽  
Javier León ◽  
Marco Formoso ◽  
...  
Keyword(s):  
Deep Learning ◽  
Power Distribution ◽  
Signal To Noise Ratio ◽  
Classification Performance ◽  
Signal Classification ◽  
Eeg Signal ◽  
Distribution Profile ◽  
Experimental Conditions ◽  
Vast Number ◽  
Eeg Signal Classification

Electroencephalography (EEG) signal classification is a challenging task due to the low signal-to-noise ratio and the usual presence of artifacts from different sources. Different classification techniques, which are usually based on a predefined set of features extracted from the EEG band power distribution profile, have been previously proposed. However, the classification of EEG still remains a challenge, depending on the experimental conditions and the responses to be captured. In this context, the use of deep neural networks offers new opportunities to improve the classification performance without the use of a predefined set of features. Nevertheless, Deep Learning architectures include a vast number of hyperparameters on which the performance of the model relies. In this paper, we propose a method for optimizing Deep Learning models, not only the hyperparameters, but also their structure, which is able to propose solutions that consist of different architectures due to different layer combinations. The experimental results corroborate that deep architectures optimized by our method outperform the baseline approaches and result in computationally efficient models. Moreover, we demonstrate that optimized architectures improve the energy efficiency with respect to the baseline models.

A comparative study on the cold type and thermal type field emission guns used in the same electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 58-59
Author(s):  
M. Iwatsuki ◽  
Y. Kokubo ◽  
Y. Harada
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Signal To Noise Ratio ◽  
Electron Source ◽  
Resolving Power ◽  
Optical Source ◽  
Experimental Conditions ◽  
High Brightness ◽  
Illumination System ◽  
Transmission Electron

On accout of its high brightness, small optical source size, and minimal energy spread, the field emission gun (FEG) has the advantage that it provides the conventional transmission electron microscope (TEM) with a highly coherent illumination system and directly improves the resolving power and signal-to-noise ratio of the scanning electron microscope (SEM). The FEG is generally classified into two types; the cold field emission (C-FEG) and thermal field emission gun (T-FEG). The former, in which a field emitter is used at the room temperature, was successfully developed as an electron source for the SEM. The latter, in which the emitter is heated to the temperature range of 1000-1800°K, was also proved to be very suited as an electron source for the TEM, as well as for the SEM. Some characteristics of the two types of the FEG have been studied and reported by many authors. However, the results of the respective types have been obtained separately under different experimental conditions.

scholarly journals Signal quality as Achilles’ heel of graph theory in functional magnetic resonance imaging in multiple sclerosis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Johan Baijot ◽  
Stijn Denissen ◽  
Lars Costers ◽  
Jeroen Gielen ◽  
Melissa Cambron ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Signal To Noise Ratio ◽  
Pearson Correlation ◽  
Signal Quality ◽  
Network Parameters ◽  
Fmri Signal ◽  
Noise Ratio ◽  
Global And Local ◽  
The Brain ◽  
Local Brain

AbstractGraph-theoretical analysis is a novel tool to understand the organisation of the brain.We assessed whether altered graph theoretical parameters, as observed in multiple sclerosis (MS), reflect pathology-induced restructuring of the brain's functioning or result from a reduced signal quality in functional MRI (fMRI). In a cohort of 49 people with MS and a matched group of 25 healthy subjects (HS), we performed a cognitive evaluation and acquired fMRI. From the fMRI measurement, Pearson correlation-based networks were calculated and graph theoretical parameters reflecting global and local brain organisation were obtained. Additionally, we assessed metrics of scanning quality (signal to noise ratio (SNR)) and fMRI signal quality (temporal SNR and contrast to noise ratio (CNR)). In accordance with the literature, we found that the network parameters were altered in MS compared to HS. However, no significant link was found with cognition. Scanning quality (SNR) did not differ between both cohorts. In contrast, measures of fMRI signal quality were significantly different and explained the observed differences in GTA parameters. Our results suggest that differences in network parameters between MS and HS in fMRI do not reflect a functional reorganisation of the brain, but rather occur due to reduced fMRI signal quality.

scholarly journals Photonic resonator interferometric scattering microscopy

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nantao Li ◽  
Taylor D. Canady ◽  
Qinglan Huang ◽  
Xing Wang ◽  
Glenn A. Fried ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Scattered Light ◽  
Near Field ◽  
Field Enhancement ◽  
Protein Detection ◽  
Significant Loss ◽  
Photonic Band Structure ◽  
Large Intensity ◽  
Photonic Band ◽  
Intensity Contrast

AbstractInterferometric scattering microscopy is increasingly employed in biomedical research owing to its extraordinary capability of detecting nano-objects individually through their intrinsic elastic scattering. To significantly improve the signal-to-noise ratio without increasing illumination intensity, we developed photonic resonator interferometric scattering microscopy (PRISM) in which a dielectric photonic crystal (PC) resonator is utilized as the sample substrate. The scattered light is amplified by the PC through resonant near-field enhancement, which then interferes with the <1% transmitted light to create a large intensity contrast. Importantly, the scattered photons assume the wavevectors delineated by PC’s photonic band structure, resulting in the ability to utilize a non-immersion objective without significant loss at illumination density as low as 25 W cm−2. An analytical model of the scattering process is discussed, followed by demonstration of virus and protein detection. The results showcase the promise of nanophotonic surfaces in the development of resonance-enhanced interferometric microscopies.

Réponses évoquées par les mouvements oculaires d'exploration (réponse lambda): Rôle des afférences intervenant à divers moments du processus oculo-moteur

Perception ◽  
1972 ◽  
Vol 1 (2) ◽  
pp. 167-175 ◽  
Author(s):  
Nicole Lesèvre ◽  
A Rémond
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Visual Effects ◽  
Experimental Conditions ◽  
Initial Portion ◽  
Vertical Movements ◽  
Black Field ◽  
Fixation Points ◽  
Lambda Response

Experiments are reported the aim of which was to elucidate the cause of each of the components of the lambda response, and particularly to evaluate the role of ‘on’ and ‘off’ visual effects which appear at various times during the oculomotor process and also the possible influence of non-visual mechanisms. Eight subjects with normal sight were studied under the following conditions: (i) horizontal eye movements of 12° were guided by fixation points placed on a dimly-lit uniform black field of 20°; a checkerboard of 6° aperture was placed in this field so as to be integrated into the oculomotor process at different times—at the beginning, during and at the end of the eye movement; (ii) successive horizontal eye movements of 3°, 7° and 11° scanned a checkerboard of 20°, each square of which had a 40′ aperture; (iii) the checkerboard was moved with an amplitude and period similar to those of the eye movements in (ii), but this time with gaze fixed. Horizontal and vertical movements of both eyes were recorded with an EOG. An EEG of the parieto-occipital regions was obtained using eight linked bipolar derivations in line on two montages, median longitudinal and right-left transverse. The EEG and EOG data were digitalized and a numerical programme of waveform recognition was used to identify the beginning of the saccade which triggers the averaging out of the EEG before (100 ms) and after (500 ms) the eye movement. A discussion of the results, taking into account the latency of the different components and their reinforcements or inhibition depending on experimental conditions, suggests that the two initial components of lambda response (including the initial portion of the classical lambda wave) might be due to visual effects (‘off effect’) that arise at the start of the movement or slightly before it at the time that the saccadic suppression begins. The later components could be attributed to visual effects brought into play towards the end of the movement (‘on effect’), when perception becomes normal again. It is, however, difficult to explain some of the results related to the amplitude of lambda components without bringing in a mechanism of non-visual origin (corollary discharge).

Covert orienting of attention in macaques. I. Effects of behavioral context

1993 ◽  
Vol 70 (1) ◽  
pp. 431-443 ◽  
Author(s):  
E. M. Bowman ◽  
V. J. Brown ◽  
C. Kertzman ◽  
U. Schwarz ◽  
D. L. Robinson
Keyword(s):  
Cognitive Processes ◽  
Reaction Times ◽  
Orienting Response ◽  
Validity Effect ◽  
Experimental Conditions ◽  
Covert Orienting ◽  
Cognitive Influences ◽  
Attentional Effect ◽  
Peripheral Cues ◽  
Neurophysiological Studies

1. A task was used by Posner (1980) to measure shifts of attention that occurred covertly, in the absence of an eye movement or other orienting response. This paradigm was used here to assess the nature of covert attentional orienting in monkeys to develop an animal model for neurophysiological studies. Shifts of attention were measurable in monkeys and were consistent across a variety of experimental conditions. 2. The paradigm required that monkeys fixate and release a bar at the appearance of a target, which was preceded by a cue. Reaction times to targets that followed peripheral cues at the same location (validly cued) were significantly faster than those that followed cues in the opposite visual field (invalidly cued). This difference was defined as the validity effect, which as in humans, is used as the measure of a covert attentional shift. 3. When the proportion of validly to invalidly cued targets was decreased, no change was seen in the validity effect of the monkeys. This is in contrast to humans, for whom the ratio of validly to invalidly cued targets affected the magnitude of the validity effect. When 80% of the targets were preceded by cues at the same location, the validity effect was greatest. The effect was reversed when the proportions were reversed. From this result, it is concluded that cognitive processes can affect covert orienting to peripheral cues in humans, whereas in trained monkeys, performance was automatic. 4. To test whether cognitive influences on attention could be demonstrated in the monkey, an animal was taught to use symbolic, foveal signals to covertly direct attention. The magnitude of this validity effect was greater than that obtained with peripheral cues. 5. The effects of motivational and perceptual processes were tested. Although overall reaction times could be modified, the facilitating effects of the cues persisted. This constancy across motivational and perceptual levels supports the notion that the monkeys were performing the task in an automatic way, under the exogenous control of peripheral cues. 6. Most visual cuing has been tested with visual landmarks at the locations of cues and targets. These monkeys were trained with such landmarks, and when tested without them, the attentional effect of the cues was nearly abolished. These data suggest that local visual features can be important for covert orienting. 7. To determine the spatial extent of the effect of the cue, monkeys and humans were tested with four cue-target distances (0-60 degrees).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Determination of DVB-T2 Signal Quality in Nigeria: A Case Study of Jos, Plateau State, Nigeria

2021 ◽  
Vol 40 (1) ◽  
pp. 81-88
Author(s):  
E.E.C. Igbonoba ◽  
O. Omoifo
Keyword(s):  
Signal To Noise Ratio ◽  
Empirical Method ◽  
Signal Quality ◽  
Television System ◽  
Jos Plateau ◽  
Television Signal ◽  
Service Areas ◽  
Noise Ratio ◽  
Plateau State

This study presents the evaluation of digital video broadcasting-terrestrial second generation (DVB-T2) Television signal quality in Jos using Integrated Television Services Limited signal. The delivery of quality Television signal remains problematic in Nigeria due to signal attenuation and degradation between the transmitter and receiver station. This is primarily due to environmental and atmospheric perturbations prevalent along the signal paths. This research aim is to determine the signal quality of DVB-T2 Television system in Jos, Plateau State. The simple field measurement methodology was adopted in measuring field strength and channel power parameters. These measurement parameters were used to calculate for carrier-to-noise ratio (CNR) and signal-to-noise ratio (SNR) through empirical method. Finally, CNR and SNR were used to determine the signal quality of DVB-T2 signal in Jos. The result of the research shows that DVB-T2 signal in the primary service areas has good and reliable signal apart from the rocky environments.

scholarly journals Overground Walking Decreases Alpha Activity and Entrains Eye Movements in Humans

2020 ◽  
Vol 14 ◽  
Author(s):  
Liyu Cao ◽  
Xinyu Chen ◽  
Barbara F. Haendel
Keyword(s):  
Eye Movements ◽  
Neuronal Activity ◽  
Walking Speed ◽  
Alpha Activity ◽  
Alpha Power ◽  
Electrode Impedance ◽  
Blink Rate ◽  
Double Support ◽  
Support Phase ◽  
Double Support Phase

Experiments in animal models have shown that running increases neuronal activity in early visual areas in light as well as in darkness. This suggests that visual processing is influenced by locomotion independent of visual input. Combining mobile electroencephalography, motion- and eye-tracking, we investigated the influence of overground free walking on cortical alpha activity (~10 Hz) and eye movements in healthy humans. Alpha activity has been considered a valuable marker of inhibition of sensory processing and shown to negatively correlate with neuronal firing rates. We found that walking led to a decrease in alpha activity over occipital cortex compared to standing. This decrease was present during walking in darkness as well as during light. Importantly, eye movements could not explain the change in alpha activity. Nevertheless, we found that walking and eye related movements were linked. While the blink rate increased with increasing walking speed independent of light or darkness, saccade rate was only significantly linked to walking speed in the light. Pupil size, on the other hand, was larger during darkness than during light, but only showed a modulation by walking in darkness. Analyzing the effect of walking with respect to the stride cycle, we further found that blinks and saccades preferentially occurred during the double support phase of walking. Alpha power, as shown previously, was lower during the swing phase than during the double support phase. We however could exclude the possibility that the alpha modulation was introduced by a walking movement induced change in electrode impedance. Overall, our work indicates that the human visual system is influenced by the current locomotion state of the body. This influence affects eye movement pattern as well as neuronal activity in sensory areas and might form part of an implicit strategy to optimally extract sensory information during locomotion.

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