Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Motion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,261 records · Page 70Linked to original sources

Quantitative analysis of regional motion and thickening by gated myocardial perfusion SPECT: normal heterogeneity and criteria for abnormality.

UNLABELLED: Quantitation of regional myocardial function is valuable in patients with coronary artery disease. This study assessed normal heterogeneity and developed and validated normal limits for quantitative regional motion and thickening by gated myocardial perfusion SPECT. METHODS: Patients underwent rest (201)Tl/exercise (99m)Tc-sestamibi gated SPECT. Reference values of motion and thickening for 20 myocardial segments were obtained in 105 patients with <5% likelihood of coronary disease (low-likelihood group). Criteria for abnormality of motion and thickening were defined for each segment, using receiver operator characteristic analysis, in 101 patients with coronary disease (training group). Semiquantitative visual interpretation was used as the gold standard. These criteria were prospectively validated in 100 patients (validation group). Criteria for grading motion and thickening abnormalities by severity levels were also defined and validated. RESULTS: Normal thickening decreased substantially along the longitudinal axis of the left ventricle, from 69% +/- 13% at the apex to 25% +/- 11% at the basal segments, whereas normal motion varied within the same ventricular plane. Validation of the criteria for abnormality yielded high accuracy in the detection of motion abnormalities (sensitivity, 88%; specificity, 92%) and thickening abnormalities (sensitivity, 87%; specificity, 89%). Quantitative motion and thickening segmental scores showed good agreement with visual scores. CONCLUSION: Normal regional myocardial contraction by gated myocardial perfusion SPECT is characterized by a substantial apex-to-base decline in thickening and by circumferential heterogeneity in endocardial motion. The assignment of segment-specific threshold values for defining motion and thickening abnormalities provided reasonably accurate identification and grading of regional myocardial dysfunction.

Aged↗

Early changes in wall motion and wall thickness during percutaneous transluminal coronary angioplasty in man.

Epicardial wall motion, myocardial wall thickness and segmental wall motion during percutaneous transluminal coronary angioplasty, a situation which resembles the experimental abrupt occlusion of a major coronary artery in the animal laboratory, have been studied in patients undergoing the procedure. Epicardial wall motion was analyzed using biplane cineradiography with frame to frame measurements of distances between pairs of radiopaque epicardial markers, placed at the time of previous cardiac surgery in a patient with a stenosis of a coronary artery bypass graft. Bypass graft occlusion led to early onset of biphasic epicardial late systolic lengthening and early diastolic shortening similar to the regional wall motion abnormality preceding the procedure. Continuous M-mode echocardiogram throughout coronary luminal occlusion, showed a decreased systolic thickening in the septum with a concomitant, prominent notch in early diastole occurring after the seventh beat following occlusion. At the 28th beat, septal systolic motion was absent while only an early diastolic septal motion was observed. Contemporaneously the end-diastolic septal thickness results decreased. Segmental wall motion analysis during ischemia was carried out performing a left ventricular angiogram before, 20 and 50 seconds after the onset of balloon inflation, 5 minutes after completion of the procedure. During the early phase of ischemia, in the ischemic segments, a late systolic lengthening with an early diastolic shortening was observed. We refer to this biphasic motion as the "W" phenomenon which appears to be the early and characteristic change in wall motion and thickness during coronary angioplasty in man.

Angioplasty, Balloon↗

Influence of velocity, temporal frequency and initial phase position of grating patterns on motion VEP.

The cortical potential visually evoked by motion of a periodic grating (motion VEP) is composed of a transient component which decays within 500 ms of stimulus-onset (motion-on VEP) and a sustained component. Amplitude and peak latency of wave N2 of the motion-on VEP are functions of grating velocity. Both remain constant at spatial frequencies between 0.6 and 4.3 c/deg and at temporal frequencies within the equivalent intervals. The transient component of the motion VEP is independent of the spatial phase position of the grating before motion onset. The sustained component can only be seen in the averaged motion VEP at constant phase position of the grating before motion onset. This potential consists of periodical fluctuations with a main frequency equal to the temporal frequency of the moving grating. As a result of psychophysical investigations some authors suggest pattern velocity is the relevant variable of velocity perception, others temporal frequency. The motion VEP is dependent on both velocity and temporal frequency, the transient component is a function of velocity, the sustained component of temporal frequency.

Electroencephalography↗

[M-mode echocardiographic standardization of interventricular septal motion and its clinical significance].

Systolic and diastolic motions of the interventricular septum (IVS), especially of its lower portion at the level of the chordae tendineae, were evaluated by M-mode echocardiography in normal subjects and in patients with various cardiac disorders. The following conclusions were derived from this study. In normal subjects, downward motion of the IVS exhibited three patterns; namely, P1, between the onset of electrical depolarization and the onset of the second heart sound; P2, between the onset of the second heart sound and the E point of the anterior mitral leaflet; and P3, between the E point of the anterior mitral leaflet and the end of the left ventricular rapid filling phase, during each cardiac cycle. The systolic IVS pattern (P1) of atrial septal defect was classified as follows: Normal type: nearly normal posterior motion during ventricular systole, Flat type: flat motion during ventricular systole, Paradoxical (early systolic) type: anterior motion during the first half of ventricular systole, followed by normal posterior motion, Paradoxical (pansystolic) type: anterior motion during ventricular systole. In atrial septal defect, the right ventricular dimension was markedly increased in the flat and paradoxical (pansystolic) types compared with those of the normal and paradoxical (early systolic) types. Marked downward IVS motion (P2) was observed in cor pulmonale with paradoxical pulse, pulmonary hypertension, Ebstein's anomaly, pulmonic insufficiency, atrial septal defect, funnel chest, tricuspid insufficiency and constrictive pericarditis. In cor pulmonale with paradoxical pulse, the deep downward motion (P2) was observed more distinctly during inspiration compared to expiration, and right ventricular inflow velocity pattern was characterized by an apparent increase in peak flow in velocity of the diastolic rapid filling wave during inspiration. Two interesting findings were a deep "y" trough of the jugular pulse tracing and prominent P2 in funnel chest. Therefore, it was likely that exaggerated P2 seemed to be direct evidence of a marked increase in right ventricular rapid filling in the presence of normal or decreased left ventricular rapid filling. The augmented septal dip of P3 was observed in cases with the third heart sound as in normal subjects, and those with mitral insufficiency, and ventricular septal defect, constrictive pericarditis and mitral stenosis. We theorized that exaggerated P3 results from the "sucking action" secondary to increased left ventricular rapid filling velocity in cases with the third heart sound or constrictive pericarditis.(ABSTRACT TRUNCATED AT 400 WORDS)

Diastole↗

Spontaneous ordering of DNA. Effects of intermolecular interactions on DNA motional dynamics monitored by 13C and 31P nuclear magnetic resonance spectroscopy.

Effects of intermolecular DNA interactions on the motional dynamics of defined length (147-, 234-, and 437-nucleotide pair (np)) double-stranded DNA were examined by 13C and 31P nuclear magnetic resonance spectroscopy. At a critical high concentration varying inversely with length, DNA undergoes a spontaneous transition to an ordered, liquid crystalline-like state. Ordering is accompanied by the appearance of distinct opalescence, and an increase in solution viscosity. An apparent standard heat of fusion of -38 kcal/mol of helix (-0.13 kcal/mol of DNA phosphate) and an entropy change of -0.13 entropy units (per mol of helix) were determined from the temperature dependence of the phase transition of 147-np DNA. The average phosphodiester configuration, monitored by Raman spectroscopy, was typical of B-form DNA above and below the phase transition. NMR spectra and relaxation data show that intermolecular interactions are strong at concentrations well below the phase transition and cause stepwise uncoupling of internal motions at specific sites. Motions of the exocyclic C5' carbon, but not other sugar carbons, are frozen in approximately 50% of 147-np DNA molecules at concentrations as low as 6.5 mg/ml. Motions of backbone ring carbons (C3', C4') are frozen in a progressively larger fraction of molecules at concentrations above 46 mg/ml. Rapid C2' motions are unaffected below the critical concentration (193 mg/ml at 32 degrees C), and still occur in the ordered phase. We conclude that rapid internal motions of DNA monitored by NMR consist mostly of coupled, periodic bending deformations and partially uncoupled local motions within the sugar ring. Rapid, extensive C2' motions can occur without strong coupling to other sugar carbon motions. From a comparison of 13C and 31P NMR data, we conclude that 31P NMR at best yields an incomplete representation of DNA dynamics.

Animals↗

Comparison of four motion correction techniques in SPECT imaging of the heart: a cardiac phantom study.

UNLABELLED: The aim of this study was to evaluate the accuracy of four different motion correction techniques in SPECT imaging of the heart. METHODS: We evaluated three automated techniques: the cross-correlation (CC) method, diverging squares (DS) method and two-dimensional fit method and one manual shift technique (MS) using a cardiac phantom. The phantom was filled with organ concentrations of 99mTc closely matching those seen in patient studies. The phantom was placed on a small sliding platform connected to a computer-controlled stepping motor. Linear, random, sinusoidal and bounce motions of magnitude up to 2 cm in the axial direction were simulated. Both single- and dual-detector 90 degrees acquisitions were acquired using a dual 90 degrees detector system. Data were acquired over 180 degrees with 30 or 15 frames/detector (single-/dual-head) at 30 sec/frame in a 64x64 matrix. RESULTS: The simulated single-detector system, CC method, failed to accurately correct for any of the simulated motions. The DS technique overestimated the magnitude of phantom motion, particularly for images acquired between 45 degrees left anterior oblique and 45 degrees left posterior oblique. The two-dimensional and MS techniques accurately corrected for motion. The simulated dual 90 degrees detector system, CC method, only partially tracked random or bounce cardiac motion and failed to detect sinusoidal motion. The DS technique overestimated motion in the latter half of the study. Both the two-dimensional and MS techniques provided superior tracking, although no technique was able to accurately track the rapid changes in cardiac location simulated in the random motion study. Average absolute differences between true and calculated position of the heart on single- and dual 90 degrees -detectors were 1.7 mm and 1.5 mm for the two-dimensional and MS techniques, respectively. The corresponding values for the DS and CC techniques were 5.7 and 8.9 mm, respectively. CONCLUSION: Of the four techniques evaluated, manual correction by an experienced technologist proved to be the most accurate, although results were not significantly different from those observed with the two-dimensional method. Both techniques accurately determined cardiac location and permitted artifact-free reconstruction of the simulated cardiac studies.

Heart↗

Physiological evidence of interaction of first- and second-order motion processes in the human visual system: a magnetoencephalographic study.

Humans have several mechanisms for the visual perception of motion, including one that is luminance-based (first-order) and another that is luminance-independent (second-order). Recent psychophysical studies have suggested that significant interaction occurs between these two neural processes. We investigated whether such interactions are represented as neural activity measured by magnetoencephalography (MEG). The second-order motion of a drifting sinusoidal grating, which is defined by the speed of the dot motion, did not generate a response. Apparent motion (AM) of the square area, defined by the speed of randomly moving dots, evoked a magnetic response whose latency and amplitude changed with the distance that the area moved (a second-order characteristic), though the response properties were significantly different from those for the first-order AM. AM, defined by both first- and second-order attributes, evoked an MEG response and the latencies and the amplitudes were distributed between those for the first- and second-order motions. The cortical source of the response was estimated to be around MT+. The results show a distinct difference in the neural processing of the second-order motion that cannot be explained by the difference in visibility, and they indicate that the interaction of the neural processes underlying first- and second-order motion detection occurs before the MEG response. Our study provides the first physiological evidence of a neural interaction between the two types of early motion detection.

Adult↗

The relation of motion sickness to the spatial-temporal properties of velocity storage.

Tilting the head in roll to or from the upright while rotating at a constant velocity (roll while rotating, RWR) alters the position of the semicircular canals relative to the axis of rotation. This produces vertical and horizontal nystagmus, disorientation, vertigo, and nausea. With recurrent exposure, subjects habituate and can make more head movements before experiencing overpowering motion sickness. We questioned whether promethazine lessened the vertigo or delayed the habituation, whether habituation of the vertigo was related to the central vestibular time constant, i.e., to the time constant of velocity storage, and whether the severity of the motion sickness was related to deviation of the axis of eye velocity from gravity. Sixteen subjects received promethazine and placebo in a double-blind, crossover study in two consecutive 4-day test series 1 month apart, termed series I and II. Horizontal and vertical eye movements were recorded with video-oculography while subjects performed roll head movements of approx. 45 degrees over 2 s to and from the upright position while being rotated at 138 degrees /s around a vertical axis. Motion sickness was scaled from 1 (no sickness) to an endpoint of 20, at which time the subject was too sick to continue or was about to vomit. Habituation was determined by the number of head movements that subjects made before reaching the maximum motion sickness score of 20. Head movements increased steadily in each session with repeated testing, and there was no difference between the number of head movements made by the promethazine and placebo groups. Horizontal and vertical angular vestibulo-ocular reflex (aVOR) time constants declined in each test, with the declines being closely correlated to the increase in the number of head movements. The strength of vertiginous sensation was associated with the amount of deviation of the axis of eye velocity from gravity; the larger the deviation of the eye velocity axis from gravity, the more severe the motion sickness. Thus, promethazine neither reduced the nausea associated with RWR, nor retarded or hastened habituation. The inverse relationship between the aVOR time constants and number of head movements to motion sickness, and the association of the severity of motion sickness with the extent, strength, and time of deviation of eye velocity from gravity supports the postulate that the spatiotemporal properties of velocity storage, which are processed between the nodulus and uvula of the vestibulocerebellum and the vestibular nuclei, are likely to represent the source of the conflict responsible for producing motion sickness.

Adult↗

Motion and space sickness: intestinal and autonomic correlates.

The purpose of this paper is to provide an overview of autonomic nervous system and gastrointestinal changes that occur during motion sickness. It is important to consider that motion sickness is a syndrome that can vary between individuals and within individuals and between and within motion sickness-inducing stimuli. Vomiting should be considered a discrete event of the motion sickness syndrome. Given so much variability in motion sickness symptoms, it should be expected that the physiological response to motion sickness will vary as well. This appears to be the case with the autonomic nervous system and gastrointestinal changes during motion sickness. Although much research remains to be done, it appears undeniable that the physiological expression of motion sickness is mediated by the autonomic nervous system, and when nausea is a predominant symptom, the stomach in general shuts down in a response characterized by decreased normal gastric myoelectrical activity and delayed gastric emptying.

Animals↗

Effects of motion and configural complexity on color transparency perception.

We tested whether motion and configural complexity affect perceived transparency. A series of five coherent chromatic transformations in color space was applied across a figure: translation, convergence, shear, divergence and rotation. The stimuli consisted of a bipartite or a checkerboard configuration (10 x 10 degrees), with a central static or moving overlay (5 x 5 degrees). Three different luminance conditions (the plane of chromatic transformation oriented toward higher, lower, or equal luminances) were also tested for each of three modulation depths. For each stimulus, the observer judged whether the overlay appeared transparent or not. The main results indicated an interaction between the type of chromatic transformation and stimulus motion and complexity. For example, convergences are judged to appear transparent significantly more often when motion is added for bipartite configurations, or when they are generated in a checkerboard configuration. Surprisingly, shears that have been reported to appear opaque, are more frequently reported to appear transparent with short vector lengths and when combined with motion. Other transformations are also affected by motion, although the effectiveness of figural complexity on transparency seems to depend on both the type of color shifts and the presence of motion. The results indicate that adding motion and stimulus complexity are not necessarily neutral with respect to the chromatic shifts evoking transparency. Thus, studies that have used motion to enhance transparency may yield different results about the color shifts supporting transparency perception from those that did not. The same might be supposed for stimulus complexity under some conditions.

Color Perception↗

Motion sickness susceptibility associated with visually induced postural instability and cardiac autonomic responses in healthy subjects.

CONCLUSIONS: This study supports the hypothesis that postural sway and autonomic responses to moving visual stimuli may be associated with motion sickness susceptibility. Characteristics of the cardiac sympathovagal balance during exposure to provocative stimulation may be a marker of individual susceptibility to motion sickness. OBJECTIVE: To assess the relationship between postural and autonomic responses to a simulated visual motion environment and reported susceptibility to motion sickness. MATERIAL AND METHODS: Fifteen healthy subjects were exposed to sinusoidally oscillating visual motion in roll at frequencies of 0.1-0.4 Hz. Recordings were made of postural sway and respiratory frequency and electrocardiograms were obtained from which heart rate variability (HRV) was computed in order to probe cardiac sympathetic and parasympathetic activity. RESULTS: In subjects with a low susceptibility to motion sickness as rated using a standardized questionnaire, there was no significant effect of visual stimulus on postural sway or HRV at any frequency of motion. Subjects with a high susceptibility to motion sickness showed significant postural instability induced by visual stimuli (p < 0.01). Visual stimuli presented at a frequency of 0.1 Hz significantly increased the low-frequency power (LF) of HRV, decreased the high-frequency power (HF) of HRV and increased the LF:HF ratio in these subjects (p < 0.05).

Adult↗

Grating and plaid chrominance motion influences the suppressed ocular following response.

Involuntary eye movements to foveal stimulation were measured in a monkey while it performed a fixation task. Second-order plaid motion generated higher velocities of eye movements than did first-order gratings, yet the latency of the early following response was no different for grating or plaid motion. Nevertheless, early suppressed ocular following responses to isoluminant motion continue to be titrated by stimulus velocity and spatial frequency. Motion defined by 60% luminance contrast gratings and plaids generated a motion signal gain of 60% over chrominance motion. The 20% longer latency of eye movements to chrominance motion may reflect the longer conduction latency of the parvocellular channel and an additional stage in cortical processing en route to motion areas and eye movement control.

Analysis of Variance↗

Prospective randomized clinical trial of continuous passive motion after total knee arthroplasty.

The authors report the results of a prospective randomized clinical trial using continuous passive motion after total knee arthroplasty. One hundred twenty patients were assigned randomly to one treatment group: No continuous passive motion (Group I), continuous passive motion from 0 degrees to 50 degrees and increased as tolerated (Group II), and continuous passive motion from 70 degrees to 110 degrees (Group III). The continuous passive motion was initiated in the recovery room and was maintained for a maximum of 24 hours at which point all patients began identical postoperative physiotherapy regimens. Patients were assessed preoperatively, during their hospital stay, at 6 weeks, 12 weeks, 26 weeks, and 52 weeks after their surgery. There were no statistical differences between any of the treatment groups regarding cumulative analgesic requirements, range of motion at any measured interval, length of stay (Group I, 5.1 days; Group II, 5.2 days; Group III, 5 days) or Knee Society scores. The current study does not support the use of short-term continuous passive motion after total knee replacement. A standard and a high flexion continuous passive motion protocol failed to show any advantage over physiotherapy alone in the parameters evaluated.

Analgesics↗

Spatial integration of visual motion with separate speed and direction information.

We present evidence to support the possibility that motion information is divided into two scalars: direction and speed, to integrate local motions over a wide spatial range. With various motion stimuli composed of numerous red and green dots, observers perceived that peripheral dots moved similar to central dots on the basis of the same direction or speed, even when speed or direction was different. The results indicate that the direction and speed of local motion can be processed separately and that the distributions are analyzed independently to integrate the local motions. This process, based on two motion scalars, may be useful for the perception of complex motions that would be difficult to perceive with a process based on motion vectors.

Adult↗

A fast biologically inspired algorithm for recurrent motion estimation.

We have previously developed a neurodynamical model of motion segregation in cortical visual area V1 and MT of the dorsal stream. The model explains how motion ambiguities caused by the motion aperture problem can be solved for coherently moving objects of arbitrary size by means of cortical mechanisms. The major bottleneck in the development of a reliable biologically inspired technical system with real-time motion analysis capabilities based on this neural model is the amount of memory necessary for the representation of neural activation in velocity space. We propose a sparse coding framework for neural motion activity patterns and suggest a means by which initial activities are detected efficiently. We realize neural mechanisms such as shunting inhibition and feedback modulation in the sparse framework to implement an efficient algorithmic version of our neural model of cortical motion segregation. We demonstrate that the algorithm behaves similarly to the original neural model and is able to extract image motion from real world image sequences. Our investigation transfers a neuroscience model of cortical motion computation to achieve technologically demanding constraints such as real-time performance and hardware implementation. In addition, the proposed biologically inspired algorithm provides a tool for modeling investigations to achieve acceptable simulation time.

Algorithms↗

Airsickness and aircraft motion during short-haul flights.

BACKGROUND: There is little quantitative information that can be used to predict the incidence of airsickness from the motions experienced in military or civil aviation. This study examines the relationship between low-frequency aircraft motion and passenger sickness in short-haul turboprop flights within the United Kingdom. METHODS: A questionnaire survey of 923 fare-paying passengers was conducted on 38 commercial airline flights. Concurrent measurements of aircraft motion were made on all journeys, yielding approximately 30 h of aircraft motion data. RESULTS: Overall, 0.5% of passengers reported vomiting, 8.4% reported nausea (range 0% to 34.8%) and 16.2% reported illness (range 0% to 47.8%) during flight. Positive correlations were found between the percentage of passengers who experienced nausea or felt ill and the magnitude of low-frequency lateral and vertical motion, although neither motion uniquely predicted airsickness. The incidence of motion sickness also varied with passenger age, gender, food consumption and activity during air travel. No differences in sickness were found between passengers located in different seating sections of the aircraft, or as a function of moderate levels of alcohol consumption. CONCLUSIONS: The passenger responses suggest that a useful prediction of airsickness can be obtained from magnitudes of low frequency aircraft motion. However, some variations in airsickness may also be explained by individual differences between passengers and their psychological perception of flying.

Acceleration↗

Direct evidence that "speedlines" influence motion mechanisms.

Determining the direction of visual motion poses a serious problem for any visual system, given the inherent ambiguities. Geisler (1999) has suggested that motion streaks left in the wake of a moving target provide a rich source of potential information that could aid in resolving direction ambiguities. Here we provide strong experimental evidence that the human visual system does in fact exploit motion streaks in direction discrimination. Masks comprising oriented random noise impeded direction discrimination of moving dots when the masks were oriented parallel to the direction of motion but had very little effect when oriented orthogonal to the direction of motion. The masking effect decreased systematically with increasing bandwidth for the parallel masks and increased with bandwidth for the orthogonal masks. Importantly, these masks had little effect on neither contrast sensitivity for detecting the moving stimuli nor for speed discrimination. Experiments with "Glass patterns" (moiré patterns constructed from random dot pairs) confirmed that misleading pattern information can impede motion detection. The results show that the oriented streaks left by moving stimuli provide fundamental information about the direction of visual motion; removing these streaks or augmenting them with erroneous streaks severely confounds motion direction discrimination.

Contrast Sensitivity↗

The role of vection, eye movements and postural instability in the etiology of motion sickness.

Motion sickness is a term that is commonly used to describe the ill effects of many provocative motion (e.g. seagoing or air travel) and apparent motion (e.g. IMAX movies and virtual reality) environments on human well-being and performance. It can be extremely debilitating and yet we do not have a precise understanding of its cause. This study evaluates the importance of three factors that are purported to be involved in the etiology of motion sickness (MS). Most provocative motion environments cause three distinct, but possibly related, responses: reflexive eye movements (EM), sensory conflict (SC), and postural instability (PS). Three current theories, concerning the etiology of motion sickness, emphasize one of these responses, but deny the importance of the others. Such theoretical approaches preclude the possibility of a synergistic interaction of these factors. This experiment employed a three-factor experimental design wherein each factor was manipulated alone or in combination with the others. The independent variables involved two levels of: PS (induced by having the subject stand on a stationary platform or on a posturally challenging platform mounted atop a partially inflated rubber inner tube); SC (with or without illusory self movement elicited visually by whole field stimulation); and EM (unrestricted or controlled by a stable fixation point). Analysis of measures of PS, SC and EM confirmed the effectiveness of these manipulations. Analysis of MS measures (questionnaires, magnitude ratings, tolerance times) revealed a main effect of SC (p < 0.01), increased MS found with illusory self motion conditions. In addition, measures of MS symptomatology revealed a significant three-way interaction between SC, PS and EM (p < 0.05), greater amounts of MS found with conditions of illusory self motion, postural challenge, and unrestricted EM. This suggests support for a multi-factorial approach to the study of MS etiology. These findings suggest a major role of SC in the elicitation of MS, but also suggest important contributions from the EM and PS mechanisms.

Adolescent↗