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Microtremor

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https://www.readbyqxmd.com/read/25674709/simultaneous-drift-microsaccades-and-ocular-microtremor-measurement-from-a-single-noncontact-far-field-optical-sensor
#1
James P Ryle, Brian Vohnsen, John T Sheridan
We report on the combined far-field measurement of the three involuntary eye movements, drift, microsaccades, and ocular microtremor (OMT), using a noncontact far-field optical method. We review the significance of the smallest and least measured, and thus least understood, of the three, OMT. Using modern digital imaging techniques, we perform detailed analysis, present experimental results, and examine the extracted parameters using a noncontact far-field sensor. For the first time, in vivo noncontact measurements of all fixational in-plane movements of the human eye are reported, which simultaneously provide both the horizontal (left-right) and vertical (up-down) displacement results...
February 2015: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/25003146/ambient-vibration-tests-of-an-arch-dam-with-different-reservoir-water-levels-experimental-results-and-comparison-with-finite-element-modelling
#2
Sergio Vincenzo Calcina, Laura Eltrudis, Luca Piroddi, Gaetano Ranieri
This paper deals with the ambient vibration tests performed in an arch dam in two different working conditions in order to assess the effect produced by two different reservoir water levels on the structural vibration properties. The study consists of an experimental part and a numerical part. The experimental tests were carried out in two different periods of the year, at the beginning of autumn (October 2012) and at the end of winter (March 2013), respectively. The measurements were performed using a fast technique based on asynchronous records of microtremor time-series...
2014: TheScientificWorldJournal
https://www.readbyqxmd.com/read/24853319/non-contact-in-vivo-measurement-of-ocular-microtremor-using-laser-speckle-correlation-metrology
#3
E Kenny, D Coakley, G Boyle
Ocular microtremor (OMT) is a small involuntary eye movement present in all subjects. In this paper we present the results of in vivo OMT measurement using a novel non-contact laser speckle technique. OMT signals have not previously been measured from the sclera using this laser speckle correlation technique. To verify the system's ability to record eye movements, it is first tested using a large angle eye rotation. Next, the system is tested with a group of 20 subjects and OMT parameters are extracted. The results of OMT measurements gave a mean frequency of 78 ± 3...
July 2014: Physiological Measurement
https://www.readbyqxmd.com/read/23638348/simultaneous-recordings-of-ocular-microtremor-and-microsaccades-with-a-piezoelectric-sensor-and-a-video-oculography-system
#4
Michael B McCamy, Niamh Collins, Jorge Otero-Millan, Mohammed Al-Kalbani, Stephen L Macknik, Davis Coakley, Xoana G Troncoso, Gerard Boyle, Vinodh Narayanan, Thomas R Wolf, Susana Martinez-Conde
Our eyes are in continuous motion. Even when we attempt to fix our gaze, we produce so called "fixational eye movements", which include microsaccades, drift, and ocular microtremor (OMT). Microsaccades, the largest and fastest type of fixational eye movement, shift the retinal image from several dozen to several hundred photoreceptors and have equivalent physical characteristics to saccades, only on a smaller scale (Martinez-Conde, Otero-Millan & Macknik, 2013). OMT occurs simultaneously with drift and is the smallest of the fixational eye movements (∼1 photoreceptor width, >0...
2013: PeerJ
https://www.readbyqxmd.com/read/23389811/ocular-tremor-in-parkinson-s-disease-is-due-to-head-oscillation
#5
Diego Kaski, Tabish A Saifee, David Buckwell, Adolfo M Bronstein
BACKGROUND: We investigated the origin of a recently reported ocular microtremor in patients with Parkinson's disease (PD). METHODS: Eye movements were recorded in 2 unselected patients with PD. Two recording techniques were used to control for artifacts: infrared video-oculography and infrared scleral reflection techniques. Head movements were also recorded with 2 different accelerometers. RESULTS: We recorded ocular oscillations in both patients (microtremor)...
April 2013: Movement Disorders: Official Journal of the Movement Disorder Society
https://www.readbyqxmd.com/read/23306826/ocular-microtremor-measurement-using-laser-speckle-metrology
#6
Emer Kenny, Davis Coakley, Gerard Boyle
We describe a novel, noninvasive measurement approach for recording a small involuntary tremor of the eye known as ocular microtremor. The method is based on measuring out-of-plane angular displacements of a target by using laser-speckle correlation of images recorded in the Fourier plane of a lens. The system has a dynamic range of 4 to 5000 μrad, resolution of 4 μrad, and a bandwidth of 250 Hz. The design and optimization of the system is presented with an in vitro validation of the system against its specification...
January 2013: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/23302805/saccadic-intrusions-review-and-update
#7
REVIEW
João Lemos, Eric Eggenberger
PURPOSE OF REVIEW: This work reviews saccadic intrusions focusing on recent developments in pathophysiology and treatment. RECENT FINDINGS: Saccadic intrusions have been recognized as features of oculomotor apraxia type 2 and neuromyelitis optica. Novel fixation instabilities have been identified such as 'staircase' square wave jerks, or the pervasive ocular microtremor seen in Parkinson's disease. Although evidence supports a network underlying the pathophysiology of square wave jerks involving cerebral hemispheres, subcortex, brainstem and cerebellum, the debate regarding the pathogenesis of ocular flutter and opsoclonus centres on a cerebellar and brainstem hypotheses...
February 2013: Current Opinion in Neurology
https://www.readbyqxmd.com/read/21149100/superior-oblique-myokymia-characteristics-and-treatment-options
#8
Daren Mickelson, Neil Lucchese, Mansoor Movaghar
Superior oblique myokymia (SOM) is an unusual eye movement disorder characterized by recurring episodes of vertical and torsional microtremor of an eye. Visual symptoms include vertical and torsional diplopia, monocular oscillopsia, and tremerous sensations. The disorder is caused by an abnormal firing of the superior oblique muscle in the affected eye. Three cases of SOM will be presented. One of these patients had improvement of her symptoms from the antidepressant drug mirtazapine (Remeron).
2004: American Orthoptic Journal
https://www.readbyqxmd.com/read/19256709/compact-portable-ocular-microtremor-sensor-design-development-and-calibration
#9
James P Ryle, Mohammed Al-Kalbani, Niamh Collins, Unnikrishnan Gopinathan, Gerard Boyle, Davis Coakley, John T Sheridan
Ocular microtremor (OMT) is a physiological high-frequency (up to 150 Hz) low-amplitude (25-2500 nm peak-to-peak) involuntary motion of the human eye. Recent studies suggest a number of clinical applications for OMT that include monitoring the depth of anesthesia of a patient in surgery, prediction of outcome in coma, and diagnosis of brain stem death. Clinical OMT investigations to date have used mechanical piezoelectric probes or piezoelectric strain gauges that have many drawbacks which arise from the fact that the probe is in contact with the eye...
January 2009: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/18356988/interferometry-for-ocular-microtremor-measurement
#10
G Boyle, D Coakley, J F Malone
The eyes of all normal subjects undergo a continuous, low-amplitude, high-frequency tremor called ocular microtremor (OMT). A number of potential clinical applications of OMT have been identified, including the prediction of outcome in coma. To date, OMT has been investigated primarily with an eye-contacting piezoelectric probe. We describe a laser-based, noncontacting, interferometric technique for the measurement of OMT. The technique employs an in-plane-sensitive, phase-modulating speckle interferometer to detect the movement of the sclera, or white of the eye...
January 1, 2001: Applied Optics
https://www.readbyqxmd.com/read/18173910/non-invasive-brainstem-monitoring-the-ocular-microtremor
#11
REVIEW
James Robertson, Shelly Timmons
The ocular microtremor (OMT) is mediated by the oculomotor area of the brainstem and is altered in several pathologic states, including traumatic brain injury, general anesthesia, brain death, coma, Parkinsonism and multiple sclerosis. The EYETECT tremor monitor is a non-invasive means of measuring the frequency and amplitude of this microscopic tremor. It has been clinically tested in these clinical scenarios and has been found to be a reliable means of detecting the depth of anesthesia, and has been useful in predicting outcome in coma and traumatic brain injury patients and in confirming brain death...
October 2007: Neurological Research
https://www.readbyqxmd.com/read/18002589/an-automated-ocular-microtremor-feature-extraction-using-the-gabor-thresholding-technique
#12
M Al-Kalbani, N Collins, G Boyle, F Hegarty, T Foran, N Sheahan, D Coakley
Ocular Microtremor (OMT) is a very fine continuous eye movement which has potential in monitoring and identifying a number of clinical conditions. There is a need for improved analysis and processing techniques to extract useful, quantifiable parameters from the OMT signal. A number of papers have shown the clinical significance of looking at the 'bursts' and 'baseling' patterns of the OMT signal. Analysis to date relies on visual inspection alone. This paper introduces an automated approach to burst/baseline identification based on a time-varying filter using the Gabor transform...
2007: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/17767509/noise-improved-signal-detection-in-cat-primary-visual-cortex-via-a-well-balanced-stochastic-resonance-like-procedure
#13
Klaus Funke, Nicolas J Kerscher, Florentin Wörgötter
Adding noise to a weak signal can paradoxically improve signal detection, a process called 'stochastic resonance' (SR). In the visual system, noise might be introduced by the image jitter resulting from high-frequency eye movements, like eye microtremor and microsaccades. To test whether this kind of noise might be beneficial or detrimental for cortical signal detection, we performed single-unit recordings from area 17 of anaesthetized cats while jittering the visual stimulus in a frequency and amplitude range resembling the possible range of eye movements...
September 2007: European Journal of Neuroscience
https://www.readbyqxmd.com/read/16120778/existing-motor-state-is-favored-at-the-expense-of-new-movement-during-13-35-hz-oscillatory-synchrony-in-the-human-corticospinal-system
#14
COMPARATIVE STUDY
Thomas Gilbertson, Elodie Lalo, Louise Doyle, Vincenzo Di Lazzaro, Beatrice Cioni, Peter Brown
Oscillations in local field potentials in the beta-frequency band (13-35 Hz) are a pervasive feature of human and nonhuman primate motor cortical areas. However, the function of such synchronous activity across populations of neurons remains unknown. Here, we test the hypothesis that beta activity may promote existing motor set and posture while compromising processing related to new movements. Three experiments were performed. First, healthy subjects were instructed to make reaction time movements of the outstretched index finger in response to imperative cues triggered by transient increases in corticospinal synchrony, as evidenced by phasic elevations of beta-frequency band microtremor and intermuscular synchrony...
August 24, 2005: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/15622740/intentional-tremor-on-a-helium-oxygen-chamber-dive-to-49-5-ata
#15
T E Berghage, L E Lash, W R Braithwaite, E D Thalmann
Tremor is a well-recognized manifestation of the high pressure nervous syndrome (HPNS). As such, its measurement and analysis during deep hyperbaric exposures can be an important index of central nervous system integrity. During the U.S. Navy's experimental chamber dive to a depth equivalent to 1600 fsw (49.5 ATA), objective measures of intentional tremor were obtained at several depths. Six subjects were pressurized in 6 days to 49.5 ATA. After spending 7 days at this pressure, they were decompressed in 19 days to the surface...
September 1975: Undersea Biomedical Research
https://www.readbyqxmd.com/read/15333410/ocular-microtremor-during-general-anesthesia-results-of-a-multicenter-trial-using-automated-signal-analysis
#16
MULTICENTER STUDY
Mairead Heaney, Leo G Kevin, Alex R Manara, Tracey J Clayton, Shelly D Timmons, John J Angel, Kenneth R Smith, Brent Ibata, Ciaran Bolger, Anthony J Cunningham
Ocular microtremor (OMT) is a fine physiologic tremor of the eye related to neuronal activity in the reticular formation of the brainstem. The frequency of OMT is suppressed by propofol and sevoflurane and predicts the response to command at emergence from anesthesia. Previous studies have relied on post hoc computer analysis of OMT wave forms or on real-time measurements confirmed visually on an oscilloscope. Our overall aim was to evaluate an automated system of OMT signal analysis in a diverse patient population undergoing general anesthesia...
September 2004: Anesthesia and Analgesia
https://www.readbyqxmd.com/read/12825645/decomposition-of-vocal-cycle-length-perturbations-into-vocal-jitter-and-vocal-microtremor-and-comparison-of-their-size-in-normophonic-speakers
#17
J Schoentgen
A statistical method that enables raw vocal cycle length perturbations to be decomposed into perturbations ascribed to vocal jitter and vocal tremor is presented, together with a comparison of the size of jitter and tremor. The method is based on a time series model that splits the vocal cycle length perturbations into uncorrelated cycle-to-cycle perturbations ascribed to vocal jitter and supra-cycle perturbations ascribed to vocal tremor. The corpus was composed of 114 vocal cycle length time series for sustained vowels [a], [i], and [u] produced by 22 male and 16 female normophonic speakers...
June 2003: Journal of Voice: Official Journal of the Voice Foundation
https://www.readbyqxmd.com/read/12612849/-myokymia-of-the-obliquus-superior-muscle-and-cryptogenetic-epilepsy
#18
Eckbert S Schnitzler, Gabriele C Gusek-Schneider, Christoph J G Lang
BACKGROUND: Myokymia of the obliquus superior muscle is a rare episodic microtremor caused by uncontrolled activities of the trochlearis nerve fibres. Epilepsy is also caused by spontaneous discharges of neurons. In our report we present an associated epilepsy which to the best of our knowledge is described for the first time. PATIENT: An 61-year old man with twitches of the right eye for 6 weeks and a subjective feeling of eye movement was investigated at our hospital...
January 2003: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/12393354/comparison-of-ocular-microtremor-and-bispectral-index-during-sevoflurane-anaesthesia
#19
COMPARATIVE STUDY
L G Kevin, A J Cunningham, C Bolger
BACKGROUND: A practical and reliable monitor of depth of anaesthesia would be a major advance on current clinical practice. None of the present monitors is both simple to use and accurate. Ocular microtremor (OMT) is a physiological tremor that is suppressed by propofol in a dose-dependent manner. We studied OMT during propofol induction and nitrous oxide-oxygen-sevoflurane maintenance of anaesthesia in 30 patients, and compared OMT with the bispectral index (BIS) as a predictor of response to verbal command...
October 2002: British Journal of Anaesthesia
https://www.readbyqxmd.com/read/12186048/modulation-frequency-and-modulation-level-owing-to-vocal-microtremor
#20
Jean Schoentgen
Vocal microtremor designates a normal slow modulation of the vocal cycle lengths of speakers who do not suffer from pathological tremor of the limbs and whose voices are not perceived as tremulous. Vocal microtremor is therefore distinct from pathological vocal tremor. The objective is to report data about the modulation frequency and modulation level owing to vocal microtremor. The modulation data have been obtained for vowels [a], [i], and [u] sustained by normophonic and mildly dysphonic male and female speakers...
August 2002: Journal of the Acoustical Society of America
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