scholarly journals Performance of a Self-Paced Brain Computer Interface on Data Contaminated with Eye-Movement Artifacts and on Data Recorded in a Subsequent Session

2008 ◽  
Vol 2008 ◽  
pp. 1-13 ◽  
Author(s):  
Mehrdad Fatourechi ◽  
Rabab K. Ward ◽  
Gary E. Birch
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
High Frequency ◽  
Large Amplitude ◽  
Low Frequency ◽  
Computer Interface ◽  
Robust Performance ◽  
Contaminated Data ◽  
Online Test ◽  
Movement Artifacts

The performance of a specific self-paced BCI (SBCI) is investigated using two different datasets to determine its suitability for using online: (1) data contaminated with large-amplitude eye movements, and (2) data recorded in a session subsequent to the original sessions used to design the system. No part of the data was rejected in the subsequent session. Therefore, this dataset can be regarded as a “pseudo-online” test set. The SBCI under investigation uses features extracted from three specific neurological phenomena. Each of these neurological phenomena belongs to a different frequency band. Since many prominent artifacts are either of mostly low-frequency (e.g., eye movements) or mostly high-frequency nature (e.g., muscle movements), it is expected that the system shows a fairly robust performance over artifact-contaminated data. Analysis of the data of four participants using epochs contaminated with large-amplitude eye-movement artifacts shows that the system's performance deteriorates only slightly. Furthermore, the system's performance during the session subsequent to the original sessions remained largely the same as in the original sessions for three out of the four participants. This moderate drop in performance can be considered tolerable, since allowing artifact-contaminated data to be used as inputs makes the system available for users at ALL times.

Distinct Subsystems for the Parafoveal Processing of Spatial and Linguistic Information during Eye Fixations in Reading

2003 ◽  
Vol 56 (5) ◽  
pp. 803-827 ◽  
Author(s):  
Albrecht W. Inhoff ◽  
Ralph Radach ◽  
Brianna M. Eiter ◽  
Barbara Juhasz
Keyword(s):  
Eye Movement ◽  
High Frequency ◽  
Word Length ◽  
Spatial Information ◽  
Low Frequency ◽  
Visual Object ◽  
Additive Effects ◽  
Linguistic Information ◽  
Object Selection ◽  
Eye Fixations

Two experiments examined readers’ use of parafoveally obtained word length information for word recognition. Both experiments manipulated the length (number of constituent characters) of a parafoveally previewed target word so that it was either accurately or inaccurately specified. In Experiment 1, previews also either revealed or denied useful orthographic information. In Experiment 2, parafoveal targets were either high- or low-frequency words. Eye movement contingent display changes were used to show the intact target upon its fixation. Examination of target viewing duration showed completely additive effects of word length previews and of ortho-graphic previews in Experiment 1, viewing duration being shorter in the accurate-length and the orthographic preview conditions. Experiment 2 showed completely additive effects of word length and word frequency, target viewing being shorter in the accurate-length and the high-frequency conditions. Together these results indicate that functionally distinct subsystems control the use of parafoveally visible spatial and linguistic information in reading. Parafoveally visible spatial information appears to be used for two distinct extralinguistic computations: visual object selection and saccade specification.

CHARACTERISTICS OF Μ-RHYTHM FREQUENCY MODULATION UNDER IMAGINARY MOVEMENTS

2021 ◽  
pp. 143-152
Author(s):  
Ya.A. Turovskiy ◽  
A.S. Davydova ◽  
V.Yu. Alekseev
Keyword(s):  
Correlation Analysis ◽  
Frequency Modulation ◽  
High Frequency ◽  
Brain Computer Interface ◽  
Low Frequency ◽  
Computer Interface ◽  
Program Instruction ◽  
And Cluster Analysis ◽  
Frequency Modulations ◽  
Μ Rhythm

The aim of the paper is to assess the phenomena of EEG frequency modulation while performing real and imaginary movements necessary for BCI control. Materials and Methods. The study enrolled a group of 30 volunteers of both sexes, aged 17 to 23. The subjects had to execute four commands and to run them randomly following the program instruction. The experiment was carried out in two ways: physically and mentally. Firstly, each command corresponded to a certain subject’s movement. Secondly, the same commands were not performed, they were only imaginary. The command was considered successfully executed if a volunteer was able to follow the program instruction and to hold the position for 2 seconds. The analysis of the results was carried out for five frequency ranges: 7–10 Hz, 9–12 Hz, 12–15 Hz, 15–20 Hz, 20–25 Hz. Results. Correlation analysis and exploratory statistics (namely, correspondence analysis and cluster analysis) were used to process the generated electroencephalographic parameters. The actually performed subjects’ movements were associated with a high number of low-frequency modulations in the 12–20 Hz range in the absence of modulating influences in the range below 12 Hz. Pronounced patterns of high-frequency modulation were peculiar for unexecuted commands. Conclusion. The results of the correlation analysis demonstrate a positive relationship between the number of cases of high-frequency modulation in the range of 9–12 Hz with the number of cases of low-frequency modulation in all other studied signal ranges in case of successful command execution. Key words: brain-computer interface, μ-rhythm, frequency modulation, EEG. Цель – оценка феноменов частотной модуляции ЭЭГ в условиях выполнения реальных и воображаемых движений, необходимых для управления ИМК. Материалы и методы. Для получения данных была сформирована группа из 30 добровольцев обоих полов в возрасте от 17 до 23 лет. Участники эксперимента должны были выполнить четыре команды и повторить их в неизвестном для них порядке, заданном программой. Эксперимент проводился двумя способами: физически и мысленно. То есть при первом способе каждая команда соответствовала определенному движению человека, при втором те же команды выполнялись воображаемо, движение представлялось мысленно. Команда считалась успешно исполненной, если добровольцу удавалось повторить и удержать заданное программой положение в течение 2 с. Анализ результатов проводился для пяти частотных диапазонов: 7–10 Гц, 9–12 Гц, 12–15 Гц, 15–20 Гц, 20–25 Гц. Результаты. Сгенерированные электроэнцефалографические показатели обрабатывались методом корреляционного анализа и методами разведочной статистики, такими как анализ соответствий и кластерный анализ. Реально выполняемые движения испытуемых связаны с высоким количеством низкочастотных модуляций в диапазоне 12–20 Гц при отсутствии модулирующих влияний в диапазоне ниже 12 Гц. Для случаев невыполнения команд характерны выраженные паттерны высокочастотной модуляции. Выводы. Результаты корреляционного анализа демонстрируют положительную связь между числом случаев высокочастотной модуляции в диапазоне 9–12 Гц с числом случаев низкочастотной модуляции во всех других исследуемых диапазонах сигнала в случае успешного выполнения команд. Ключевые слова: интерфейс «мозг – компьютер», μ-ритм, частотная модуляция, ЭЭГ.

scholarly journals Nonlinear low-frequency gravity waves in a water-filled cylindrical vessel subjected to high-frequency excitations

2013 ◽  
Vol 469 (2153) ◽  
pp. 20120536 ◽  
Author(s):  
Chunyan Zhou ◽  
Dajun Wang ◽  
Song Shen ◽  
Jing Tang Xing
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Water Waves ◽  
Large Amplitude ◽  
Low Frequency ◽  
Approximation Model ◽  
Fluid Structure Interactions ◽  
Governing Equations ◽  
Low Frequencies ◽  
Nonlinear Fluid

In the experiments of a water storage cylindrical shell, excited by a horizontal external force of sufficient large amplitude and high frequency, it has been observed that gravity water waves of low frequencies may be generated. This paper intends to investigate this phenomenon in order to reveal its mechanism. Considering nonlinear fluid–structure interactions, we derive the governing equations and the numerical equations describing the dynamics of the system, using a variational principle. Following the developed generalized equations, a four-mode approximation model is proposed with which an experimental case example is studied. Numerical calculation and spectrum analysis demonstrate that an external excitation with sufficient large amplitude and high frequency can produce gravity water waves with lower frequencies. The excitation magnitude and frequencies required for onset of the gravity waves are found based on the model. Transitions between different gravity waves are also revealed through the numerical analysis. The findings developed by this method are validated by available experimental observations.

Apparent Dissociation Between Saccadic Eye Movements and the Firing Patterns of Premotor Neurons and Motoneurons

1999 ◽  
Vol 82 (5) ◽  
pp. 2808-2811 ◽  
Author(s):  
Leo Ling ◽  
Albert F. Fuchs ◽  
James O. Phillips ◽  
Edward G. Freedman
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
High Frequency ◽  
Action Potentials ◽  
Saccadic Eye Movements ◽  
Line Of Sight ◽  
Movement Amplitude ◽  
Burst Neurons ◽  
Premotor Neurons ◽  
Motoneuron Activity

Saccadic eye movements result from high-frequency bursts of activity in ocular motoneurons. This phasic activity originates in premotor burst neurons. When the head is restrained, the number of action potentials in the bursts of burst neurons and motoneurons increases linearly with eye movement amplitude. However, when the head is unrestrained, the number of action potentials now increase as a function of the change in the direction of the line of sight during eye movements of relatively similar amplitudes. These data suggest an apparent uncoupling of premotor neuron and motoneuron activity from the resultant eye movement.

Design and Research on the New Combining Vibrating Screen

2011 ◽  
Vol 201-203 ◽  
pp. 504-509 ◽  
Author(s):  
Nian Qin Guo ◽  
Hong Min Lou ◽  
Wei Ping Huang
Keyword(s):  
High Frequency ◽  
Large Amplitude ◽  
Small Amplitude ◽  
Low Frequency ◽  
The Other ◽  
Vibration Exciter ◽  
Vibrating Screen ◽  
Screening Efficiency ◽  
New Type ◽  
Equal Thickness

Basing on the traditional vibrating screen with double amplitudes and different frequency, a new type vibrating screen called combining vibrating screen is developed. It consists of two vibrating screen units. Each unit has an independent vibration exciter, realizing that one screen unit has a parameter of high-frequency with small-amplitude while the other screen unit has a parameter of low-frequency with large-amplitude. The two screen units are installed at different obliquities, so that the equal thickness screening principle can be realized. And comparing with the traditional vibrating screen, its screening efficiency and capacity are greatly improved. This new kind vibrating screen is especially suitable for the dry screening to moist particles.

Reading Disappearing Text

2003 ◽  
Vol 14 (4) ◽  
pp. 385-388 ◽  
Author(s):  
Keith Rayner ◽  
Simon P. Liversedge ◽  
Sarah J. White ◽  
Dorine Vergilino-Perez
Keyword(s):  
Eye Movement ◽  
Cognitive Processes ◽  
High Frequency ◽  
Visual Information ◽  
Low Frequency ◽  
Movement Control ◽  
Oculomotor Control ◽  
Frequency Effect ◽  
Normal Reading ◽  
Control Models

Participants read sentences containing high- or low-frequency target words under normal reading conditions or disappearing-text conditions (in which the word that was fixated disappeared after 60 ms). Even though the fixated word had disappeared after 60 ms, there was still a robust frequency effect wherein readers fixated longer on low-frequency words than on high-frequency words. Thus, the results are consistent with cognitive-control models of eye movement control and inconsistent with visual/oculomotor-control models. Although the uptake of visual information is clearly important for reading, it is the cognitive processes associated with understanding the fixated words that drive the eyes through the text.

Theory of stimulated scattering of large-amplitude waves

1999 ◽  
Vol 61 (1) ◽  
pp. 129-134 ◽  
Author(s):  
L. STENFLO
Keyword(s):  
Dispersion Relation ◽  
High Frequency ◽  
Large Amplitude ◽  
Pump Wave ◽  
Low Frequency ◽  
Nonlinear Dispersion ◽  
Stimulated Scattering ◽  
Nonlinear Dispersion Relation

A nonlinear dispersion relation that governs the interaction between a high-frequency pump wave and the low-frequency modes in a plasma is derived. Previous results are generalized and discussed.

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