Thesis (M.Sc. in Physiol.) -- Mahidol University, 1971.

This paper describes an electro-oculometer and analyzes the electronic circuits required to process the signal. This electro-oculometer is a passive, two-channel device which detects the eye orientation using commercially available electrodes attached near the eyes. The electro-oculometer is composed of a special amplifier followed by a parabolic filter. The amplifier has high common mode rejection ratio, low drift, and low input bias current. Both DC and AC analyses of the electro-oculometer have been performed. The common mode rejection ratio (CMRR) of the input stage of the device is computed both at low and high frequencies. The experimental data were then compared with theoretical results. A parabolic low pass filter was designed and implemented as part of the electro-oculometer. A parabolic filter was chosen because it gives a minimum overshoot step response. The input stage (preamplifier) of the electro-oculometer is modified so as to prevent a latch up problem. This latch up is a saturated state of the system. When the output of the system reaches saturation, the system cannot reset itself. The new configuration of the preamplifier does not require any extra active elements.

Thesis (M. S.)--Psychology, Georgia Institute of Technology, 2009. / Committee Chair: Dr. Paul Corballis, Ph.D.; Committee Member: Dr. Daniel Spieler, Ph.D.; Committee Member: Dr. Eric Schumacher, Ph.D.; Committee Member: Dr. Krish Sathian, M.D., Ph.D.; Committee Member: Dr. Randall Engle, Ph.D.

This master’s thesis deals with muscles physiology of eye movement and questions of surface electromyography measurement. Physiology and analysis of eye movement are described here. Furthermore the paper deals with a variety of electrooculographic measuring techniques and also with resulting evaluation of measured signal.

The eye movements of expert and novice chess players were recorded by electrooculography (EOG) technique as they attempted to find the mate in fifteen tactically active simple chess positions. In the analysis part of the data gathered from EOG recordings, the effect of the drift, which is an important problem for EOG, was reduced. The processed data were converted into coordinates of the display on which the chess positions were demonstrated. In the test phase, the players were asked to fixate the white king which appeared on a different square on an empty chess board for one second. It was predicted on which square the subject fixated by the method developed. The predictions and the actual location of the white king were compared and the results revealed that EOG technique can be used reliably to track the eye movements of the chess players while they fixated on a chess board. It has been revealed that experts produced more fixations on the relevant squares than did the novices as the fixations were investigated. The difference between fixation duration was not significant across skill groups. The results provide evidence for an early perceptual encoding advantage for expert players attributable to chess experience.

The master´s thesis deals with fatigue evaluation in electrooculography records (EOG). The theoretical part focuses on electrooculography itself, fatigue and methods used for fatigue detection from EOG. The practical part includes a plan of optimal methodology for fatigue evaluation using EOG. The EOG signals are recorded during the volunteers are watching prepared scenes. Those scenes are desribed here. There is also definition of signal processing methods with relevant block diagrams. Laboratory protocol describing EOG signals recording using Biopac data acquisition system is included. Ten volunteers were measured according to this protocol and the signal database was created. In brief questionnaire volunteers were supposed to evaluate fatigue and discomfort of the measurment. Recorded signals were processed and acquired parameters were statistically evaluated. Then the parameters were discussed in terms of fatigue detection ability. On the basis of that software application was created. This application detects fatigue in selected signal. The thesis includes detailed laboratory manual for students.

Deafferented cortical visual areas exhibit topographical plasticity such that their constituent neural populations adapt to the loss of sensory input through the expansion and eventual remapping of receptive fields to new regions of space. Such representational plasticity is most compelling in the long-term (months or years) but begins within seconds of retinal deafferentation (short-term plasticity). The neural mechanism proposed to underlie topographical plasticity is one of disinhibition whereby long-range horizontal inputs are "unmasked" by a reduction in local inhibitory drive. In this dissertation, four experiments investigated the neural mechanisms of short-term visual plasticity and disinhibition in humans using a combination of psychophysics and event-related potentials (ERPs). Short-term visual plasticity was induced using a stimulus-induced analog of retinal deafferentation known as an artifical scotoma. Artificial scotomas provide a useful paradigm for the study of short-term plasticity as they induce disinhibition but are temporary and reversible. Experiment 1 measured contrast response functions from within the boundaries of an artificial scotoma and evaluated them relative to a sham control condition. Changes in the contrast response function suggest that disinhibition can be conceived of in terms of two dependent but separable processes: receptive field expansion and unrestricted neural gain. A two-process model of disinhibition is proposed. A complementary ERP study (Experiment 2) recorded visual evoked potentials elicited by probes appearing within the boundaries of an artificial scotoma. Results revealed a neural correlate of disinhibition consistent with origins in striate and extrastriate visual areas. Experiment 3 and 4 were exploratory examinations of the representation of space surrounding an artificial scotoma and revealed a neural correlate of invading activity from normal cortex. Together, the results of these four studies strengthen the understanding of the neural mechanisms that underlie short-term plasticity and provide a conceptual framework for their evaluation.

No description available.

The electro-oculogram (EOG) is the most widely used technique for recording eye movements in clinical settings. It is inexpensive, practical, and non-invasive. Use of EOG is usually restricted to horizontal recordings as vertical EOG contains eyelid artefact (Oster & Stern, 1980) and blinks. The ability to analyse two dimensional (2D) eye movements may provide additional diagnostic information on pathologies, and further insights into the nature of brain functioning. Simultaneous recording of both horizontal and vertical EOG also introduces other difficulties into calibration of the eye movements, such as different gains in the two signals, and misalignment of electrodes producing crosstalk. These transformations of the signals create problems in relating the two dimensional EOG to actual rotations of the eyes. The application of an artificial neural network (ANN) that could map 2D recordings into 2D eye positions would overcome this problem and improve the utility of EOG. To determine whether ANNs are capable of correctly calibrating the saccadic eye movement data from 2D EOG (i.e. performing the necessary inverse transformation), the ANNs were first tested on data generated from mathematical models of saccadic eye movements. Multi-layer perceptrons (MLPs) with non-linear activation functions and trained with back propagation proved to be capable of calibrating simulated EOG data to a mean accuracy of 0.33° of visual angle (SE = 0.01). Linear perceptrons (LPs) were only nearly half as accurate. For five subjects performing a saccadic eye movement task in the upper right quadrant of the visual field, the mean accuracy provided by the MLPs was 1.07° of visual angle (SE = 0.01) for EOG data, and 0.95° of visual angle (SE = 0.03) for infrared limbus reflection (IRIS®) data. MLPs enabled calibration of 2D saccadic EOG to an accuracy not significantly different to that obtained with the infrared limbus tracking data.

<p>У тези је предложена метода мерења ЕОГ сигнала на интервалу са<br />преклапањем временских прозора, која представља модификацију<br />дигиталне стохастичке методе мерења (ДСММ). Хардвер којим се<br />предложена метода може имплементирати заснован је на рачунарској<br />платформи и микроконтролерској структури. Метода је испитана бројним<br />симулацијама и експериментима. Хипотеза ове тезе &ndash; да модел мерења<br />ЕОГ сигнала на интервалу са преклапањем временских прозора<br />омогућава пројектовање ЕОГ мерног уређаја који је отпорнији на утицај<br />шума него ЕОГ мерни уређаји засновани на класичном дигиталном<br />мерењу &ndash; потпуно је потврђена.</p> / <p>U tezi je predložena metoda merenja EOG signala na intervalu sa<br />preklapanjem vremenskih prozora, koja predstavlja modifikaciju<br />digitalne stohastičke metode merenja (DSMM). Hardver kojim se<br />predložena metoda može implementirati zasnovan je na računarskoj<br />platformi i mikrokontrolerskoj strukturi. Metoda je ispitana brojnim<br />simulacijama i eksperimentima. Hipoteza ove teze &ndash; da model merenja<br />EOG signala na intervalu sa preklapanjem vremenskih prozora<br />omogućava projektovanje EOG mernog uređaja koji je otporniji na uticaj<br />šuma nego EOG merni uređaji zasnovani na klasičnom digitalnom<br />merenju &ndash; potpuno je potvrđena.</p> / <p>EOG signal measurement method over an interval using overlapping time<br />windows, which represents the modification of the digital stochastic<br />measurement method (DSMM), has been proposed in this thesis. The<br />hardware that can implement the proposed method is based on a computer<br />platform and a microcontroller structure. The method has been tested with<br />numerous simulations and experiments. Hypothesis of this thesis - the model<br />of EOG signal measurement over an interval using overlapping time windows<br />allows a design of EOG measuring device more resistant to the noise impact<br />than the EOG measuring devices based on classical digital measurement -<br />has been fully confirmed.</p>