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Review of the Human Brain and EEG Signals
Published in Teodiano Freire Bastos-Filho, Introduction to Non-Invasive EEG-Based Brain–Computer Interfaces for Assistive Technologies, 2020
Alessandro Botti Benevides, Alan Silva da Paz Floriano, Mario Sarcinelli-Filho, Teodiano Freire Bastos-Filho
As the spatial filters cannot eliminate all artifacts components, some methods for avoiding, detecting, and discarding or minimizing the EOG and eye blink artifacts will be discussed here. The first consideration for avoiding EOG artifact is to provide a fixation point during the mental tasks that helps to avoid eye movement artifacts. For example, an efficient strategy is to instruct subjects, during their mental tasks, to observe a cross in the center of the screen [13], in order to prevent eye movements.
Basic science, investigations and lasers
Published in Mostafa Khalil, Omar Kouli, The Duke Elder Exam of Ophthalmology, 2019
Tarek Khalil, Bilal Ibrahim, Stewart Gillan, Obaid Kousha
Electroretinogram (ERG) tests the electrical activity of the retina in response to a light stimulus. Electro-oculogram (EOG) reflects the activity of photoreceptors and RPE; thus retinal diseases proximal to the photoreceptors give normal EOG readings. ERG and EOG may be useful in aiding diagnosis in conditions such as Best disease and retinitis pigmentosa.
Sleep research recording methods
Published in Philip N. Murphy, The Routledge International Handbook of Psychobiology, 2018
EOG electrodes are placed 1 cm outside the outer canthus of each eye. EOG records electrical potential between the cornea and Bruch’s membrane, which translates into micro-voltage changes based on eye orientation. The two EOG electrodes are offset so that one records vertical and the other horizontal eye movements, which are useful for identifying several sleep stages. Specifically, N1 is defined in part based on the onset of slow eye movements and N2 on the absence of these movements. During REM sleep, eye movements are relatively rapid and, although they are not necessary to identify REM sleep, their presence can be sufficient to confirm this stage.
Evaluating the Vestibulo-Ocular Reflex Following Traumatic Brain Injury: A Scoping Review
Published in Brain Injury, 2021
Adrienne Crampton, A. Garat, H. A. Shepherd, M. Chevignard, K. J. Schneider, M. Katz-Leurer, I.J. Gagnon
More objective measures, such as the rotary chair test and caloric irrigation that use videonystagmography to measure eye movement, have been considered the gold standard for detecting bilateral and unilateral vestibular impairment (32). The rotary chair test and caloric irrigation provide objective measures of horizontal SCC function; however, they do so at low frequencies and the former does not allow one to determine the side of vestibular hypofunction. When evaluating the VOR it is important to stimulate the SCCs at high frequencies to best isolate the VOR and better mimic normal head movement frequencies (33). The scleral search coil and electronystagmography/electrooculography (ENG/EOG) are objective tools previously used to support eye-movement measurement at high frequencies. While enabling higher frequency stimulation of all SCCs, these tools are seldom used. Limitations are the scleral search coil’s invasiveness and EOG/ENG’s inability to measure specific positional variables of the eyes.
Mental tasking and rotary Chair-Induced vestibular nystagmus utilizing Video-Oculography
Published in International Journal of Audiology, 2020
Steven M. Doettl, Mary K. Easterday, Patrick N. Plyler, Lacey L. Behn, Allison S. Poget
However, recent changes in vestibular testing measurement techniques suggest the need to evaluate the use of mental tasking using the most current evaluation techniques. EOG is a measurement technique that relies on the opposing electrical charges of the cornea and the retina (Wallace and Norris 1966). This method utilises electrodes placed around the eyes and nose on the face in order to compare the movements of the eye to the ground electrode in the experimental setup with tracings representing deviations from the baseline behaviour represented through computer software (Ganança, Caovilla, and Ganança 2010; Wallace and Norris 1966). EOG testing is completed in a darkened room in order to prevent visual suppression of the nystagmus which is most often achieved by closing the eyes (Jacobson, Newman, and Kartush 1997).
Neuropsychological, electrophysiological, and neuroimaging biomarkers for REM behavior disorder
Published in Expert Review of Neurotherapeutics, 2019
Luigi Ferini-Strambi, Elisabetta Fasiello, Marco Sforza, Maria Salsone, Andrea Galbiati
Another study showed a negative correlation between amount of REM stability and severity of disease, assessed with the RBD Screening Questionnaire (RBDSQ) [78]. Some of these studies have focused on eye movements (EMs), which are controlled by neurons in brainstem during sleep [79]. Therefore through EMs, both REMs and slow EMs, it is possible to discriminate between early forms of neurodegeneration and healthy condition, and between early and advanced stages of PD [80]. Christensen and collaborators [76] showed that both in PD, and less markedly in iRBD patients, EMs are less visible and less present than in healthy controls. All these findings suggest that neurons located in basal brain regions, that determine EEG and electrooculography (EOG) sleep features and the ability to maintain NREM and REM sleep, are damaged in iRBD, but even more in PD patients [78]. Thus, iRBD can be considered as a transitional stage between a healthy condition and the clinic onset of PD, according with Braak’s staging theory [75]. Sleep macrostructure features, such as the ability to maintain NREM and REM sleep, and the amount of REM and SWS sleep, may represent hallmarks of PD in iRBD subjects. Despite the above-mentioned findings, EMs alone fail to provide specific, sensible and reliable information [77]. To differentiate more accurately between patients with neurodegeneration and disease-free, it is still necessary the combined use of EOG with EEG [77].