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At least 253 records · Page 14Linked to original sources
PubMed1992

Direct imaging of the tricuspid valve annular motions by fiberoptic cardioscopy in dogs with tricuspid regurgitation. II. Does flexible ring annuloplasty preserve the annular motions?

Applying the technology of direct imaging by fiberoptic cardioscopy in a working-heart condition, we studied the tricuspid valve annular motions with flexible rings in nine dogs with chronic tricuspid regurgitation. Three annuloplasty studies with a totally flexible polytetrafluoroethylene ring, an elastic silicone ring, and a rigid metal ring were compared with a nonannuloplasty study. The annuloplasty was performed by reducing tricuspid valve annular area to 65% of that of nonannuloplasty condition. The anuli were observed and recorded on a videotape in real time. The three rings effectively reduced and remodeled the dilated anuli and improved the valve coaptation. The patterns of annular motions with the polytetrafluoroethylene and silicone ring were similar to that of normal anulus; the free wall anulus contracted centripetally, and the septal anulus moved toward the free wall side during systole. Pliability of both the anteroseptal and posteroseptal commissures with the flexible rings made these motions possible. The polytetrafluoroethylene ring followed a natural undulation of the anulus, whereas the silicone and rigid metal rings forced the annular planes to horizontal ones. Percent reductions of tricuspid valve annular area were 25%, 21%, and 23% in the nonannuloplasty, polytetrafluoroethylene, and silicone ring studies, respectively, without significant differences in annular contraction. In contrast, rigid metal rings completely disturbed the annular motions. These findings indicated that the two flexible rings did preserve the physiologic annular motions to the degree that the anuli had in the chronic tricuspid regurgitation condition. Especially, the totally flexible polytetrafluoroethylene ring preserved not only the annular motions but also the natural undulation, which resulted in reinforcing the valve coaptation. We believe that the flexible ring, especially a totally flexible one, is superior to the rigid ring in the aspect of reinforcing the valve coaptation to prevent further regurgitation.

Animals↗
PubMed1990

Motion characteristic of the normal lumbar spine in young adults: instantaneous axis of rotation and vertebral center motion analyses.

To determine the motion characteristic of the normal lumbar spine, 61 of 612 optimal radiographs of healthy young Japanese adults in the neutral erect, active maximum flexion and maximum extension positions were carefully selected. The coordinates of the instantaneous axis of rotation (IAR) and vertebral center from L1 to L5 vertebra were analyzed. The directional shifts in IAR in the x-axis and the y-axis closely reflected translational and rotational movements of the vertebra. The IAR showed qualitative values with very large, 95%, probability ellipses in the normal lumbar spine. Analysis of coordinates of the vertebral center provided quantitative data of the extension-to-flexion motion of each vertebra. In extension-to-flexion motion, the L4 vertebra showed a translation-predominant motion characteristic. The L5 vertebra had a rotation-predominant motion characteristic. The patterns of motion of the L1-L4 vertebrae were correlated to the intervertebral disc height and the inclination angle of the facet joint. The L5 vertebra alone showed some specific patterns suggestive of the involvement of a separate ligamentous stabilizer, the iliolumbar ligaments, which reduces translation.

Adolescent↗
PubMed1983

[New approach for quantifying left ventricular regional wall motion in ischemic heart disease: motion vector analysis of endocardial surface by two-dimensional echocardiography].

To quantify regional wall motion of the left ventricle with two-dimensional echocardiography, the motion of an endocardial surface point in echocardiograms was analyzed throughout systole on frame by frame using video motion analyzer. With a fixed external reference system and in the "69% point (C)" by Ingels et al, the motion vector (M) of a point was expressed in two components; the contracting component (Y) directed toward the point C, and the component vertical to it, the shearing component (X). In the control group, the magnitude of M and its contracting component were widely varied with the location along the endocardial surface (5.6 +/- 1.6, 5.0 +/- 1.5 mm in the apex, 10.9 +/- 2.2, 10.4 +/- 2.0 mm in the inferior base, p less than 0.001 and p less than 0.001, respectively). The shearing component and the angle theta at which M and Y meet, showed narrow normal ranges (1.9 +/- 1.4 mm, 15.1 +/- 1.4 mm, 15.1 +/- 11.2 degrees), and were independent of their locations. In the ischemic group, however, the points of non-ischemic regions showed low values of theta (14.9 +/- 8.9 degrees), which were not significantly different from those of the control group, while the points of ischemic regions showed high values of theta (over 2SD of the control group). The distribution of these points with abnormal theta values was well correlated to that of the segments with asynergic motion evaluated by both real-time two-dimensional echocardiography and left ventriculography (p less than 0.001 and p less than 0.001, respectively). These results suggest that this new approach with quantitative echocardiography is sensitive and specific for the assessment of regional wall motion of the left ventricle and may provide accurate clinical information for the evaluation of ischemic heart disease.

Adolescent↗
PubMed1995

[Motion of the mitral anulus and suitability of the motion amplitude for determination of left ventricular function in Q-type myocardial infarct].

Cardiac apex hardly changes its location during the time of cardiac cycle, but the mitral anulus--representing cardiac base--has a systolic descent toward the apex and in diastole moves to the left atrium. The whole amplitude of mitral anulus motion is so useful indicator of left ventricular systolic function as ejection fraction derived from enddiastolic and endsystolic parameters. Mitral anulus motion amplitude easy to measure noninvasively by echocardiography. Authors examined 110 patients with their first, Q-type acute myocardial infarction 7-10 days after the onset of symptoms. In the same time ejection fraction value was assessed by radionuclide ventriculography. Data of ejection fraction and mitral anulus motion amplitude were compared. Their conclusions: 1. mitral anulus motion amplitude well correlated with left ventricular ejection fraction 2. patients had a decreased mitral anulus motion amplitude at the site of infarction 3. investigation of mitral anulus motion amplitude is an useful and easy to make method to assess of systolic function of left ventricle in acute myocardial infarction.

Echocardiography↗
PubMed1988

A two dimensional field theory for motion computation. First order approximation; translatory motion of rigid patterns.

The local extraction of motion information from brightness patterns by individual movement detectors of the correlation-type is considered in the first part of the paper. A two-dimensional field theory of movement detection is developed by treating the distance between two adjacent photoreceptors as a differential. In the first approximation of the theory we only consider linear terms of the time interval between the reception of a contrast element and its delayed representation by the detector and linear terms of the spatial distances between adjacent photoreceptors. As a result we may neglect terms of higher order than quadratic in a Taylor series development of the brightness pattern. The responses of pairs of individual movement detectors are combined to a local response vector. In the first approximation of the detector field theory the response vector is proportional to the instantaneous pattern velocity vector and linearly dependent on local properties of the moving pattern. The linear dependence on pattern properties is represented by a two by two tensor consisting of elements which are nonlinear, local functionals of the moving pattern. Some of the properties of the tensor elements are treated in detail. So, for instance, it is shown that the off-diagonal elements of the tensor disappear when the moving pattern consists of x- and y-dependent separable components. In the second part of the paper the tensor relation leading to the output of a movement detector pair is spatially integrated. The result of the integration is an approximation to a summation of the outputs of an array of detector pairs. The spatially integrated detector tensor relates the translatory motion vector to the resultant output vector. It is shown that the angle between the motion vector and the resultant output vector is always smaller than +/- 90 degrees whereas the angle between the motion vector and local response vectors, elicited by detector pairs, may cover the entire angular range. In the discussion of the paper the limits of the field theory for motion computation as well as its higher approximations are pointed out in some detail. In a special chapter the dependence of the detector response on the pattern properties is treated and in another chapter questions connected with the so called aperture problem are discussed. Furthermore, properties for compensation of the pattern dependent deviation angle by spatial physiological integration are mentioned in the discussion.

Animals↗
PubMed2003

Normal and anomalous development of visual motion processing: motion coherence and 'dorsal-stream vulnerability'.

Directional motion processing is a pervasive and functionally important feature of the visual system. Behavioural and VEP studies indicate that it appears as a cortical function after about 7 weeks of age, with global processing, motion based segmentation, and the use of motion in complex perceptual tasks emerging shortly afterwards. A distinct, subcortical motion system controls optokinetic nystagmus (OKN) from birth, showing characteristic monocular asymmetries which disappear as binocular cortical function takes over in normal development. Asymmetries in cortical responses are linked to this interaction in a way that is not yet fully understood. Beyond infancy, a range of developmental disorders show a deficit of global motion compared to global form processing which we argue reflects a general 'dorsal-stream vulnerability'.

Animals↗
PubMed1998

Modelling motion sickness and subjective vertical mismatch detailed for vertical motions.

In an attempt to predict the amount of motion sickness given any kind of motion stimulus, we describe a model using explicit knowledge of the vestibular system. First, the generally accepted conflict theory is restated in terms of a conflict between a vertical as perceived by the sense organs like the vestibular system and the subjective vertical as determined on the basis of previous experience. Second, this concept is integrated with optimal estimation theory by the use of an internal model. If detailed for vertical motions only, the model does predict typical observed motion sickness characteristics, irrespective the parameter setting. By adjusting the nonvestibular parameters, the model can also quantitatively be adapted to seasickness data from the literature. With this concept, sickness severity hypothetically can also be predicted for other motions, irrespective of their origin and complexity.

Conflict, Psychological↗
PubMed2002

Effect of a passive jaw motion device on pain and range of motion in TMD patients not responding to flat plane intraoral appliances.

This study was designed to compare the effectiveness of a passive jaw motion device, the Therabite, and wooden tongue depressors (WTD), in patients with temporomandibular joint and muscle disorders, who did not improve after manual manipulation of the mandible and flat bite plane therapy. Forty-three patients were enrolled in the study and were classified as joint or muscle groups according to the Research Diagnostic Criteria for TMD. Twenty-four were assigned to the joint group, and 19 patients were assigned to the muscle group. The patients were assigned at random to three treatment subgroups: 1. passive jaw motion device therapy (Therabite); 2. wooden tongue depressors therapy (WTD); and 3. control group. All subjects received flat bite plane appliance therapy throughout the treatment period. Mandibular range of motion was measured for maximum opening (MO), right and left lateral (Rt. Lateral, Lt. Lateral) and protrusive (Pr) movements. Pain level was also assessed at the beginning and at the end of the treatment. The results suggested that a passive jaw motion device is effective in increasing range of motion in both groups of temporomandibular disorder patients, joint (intracapsular) and muscle (extracapsular). It also appears to decrease pain in patients with temporomandibular disorders. Pain was relieved to a greater degree in the muscle group than the joint group.

Analysis of Variance↗
PubMed2002

Motion perception and motion estimation by total-least squares.

A computational model of motion perception is proposed. The model, which is gradient-based, adheres to the neural constraint that transmitted signals are positive-valued functions by posing the estimation of image motion as a quadratic programming problem combined with total-least squares: a model that assumes that image signals are contaminated by noise in both the spatial and temporal dimensions. By shrinking motion estimates with a regularizer whose subtractive effect introduces a contrast dependent speed threshold into motion computations, it is shown that the total-least squares model when posed as a quadratic programming problem, is capable of explaining both increases and decreases in perceived speed as these effects were reported by Thompson (1982) to vary as a function of image contrast and temporal frequency. The correlation that exists between the model's contrast speed response and results reported from visual psychophysics is consistent with the view that the visual system assumes that image signals may be contaminated by noise in both the spatial and the temporal domain, and that visual motion is influenced by the consequence of these assumptions.

Humans↗
PubMed1988

Finding motion parameters from spherical motion fields (or the advantages of having eyes in the back of your head).

A theory is developed for determining the motion of an observer given the motion field over a full 360 degree image sphere. The method is based on the fact that for an observer translating without rotation, the projected circular motion field about any equator can be divided into disjoint semicircles of clockwise and counterclockwise flow, and on the observation that the effects of rotation decouple around the three equators defining the three principal axes of rotation. Since the effect of rotation is geometrical, the three rotational parameters can be determined independently by searching, in each case, for a rotational value for which the derotated equatorial motion field can be partitioned into 180 degree arcs of clockwise and counterclockwise flow. The direction of translation is also obtained from this analysis. This search is two dimensional in the motion parameters, and can be performed relatively efficiently. Because information is correlated over large distances, the method can be considered a pattern recognition rather than a numerical algorithm. The algorithm is shown to be robust and relatively insensitive to noise and to missing data. Both theoretical and empirical studies of the error sensitivity are presented. The theoretical analysis shows that for white noise of bounded magnitude M, the expected errors is at worst linearly proportional to M. Empirical tests demonstrate negligible error for perturbations of up to 20% in the input, and errors of less than 20% for perturbations of up to 200%.

Humans↗
PubMed1997

Quantitative assessment of the motion of the lumbar spine in the low back pain population and the effect of different spinal pathologies of this motion.

There are few objective means by which disability caused by low back pain (LBP) can be quantified. The purpose of this study was to investigate the usefulness of motion measurements in the assessment of LBP. The motion characteristics of 138 LBP subjects were investigated, and the data compared with a previously published database of normal subjects. Values of range of motion and angular velocity were obtained for all subjects in each plane of motion. Analysis of these motion characteristics demonstrated significant differences (P < 0.0001) between the two populations; however both populations demonstrated considerable intersubject variation. Multiple regression analysis revealed that some of the variance in the LBP population was attributable to the underlying diagnosis. Patients with a spondylolisthesis tended to be hypermobile whilst those with spinal stenosis, disc prolapse or degenerative disc disease tended to be hypomobile. All diagnostic groups showed impairments in their velocity characteristics.

Adult↗
PubMed1987

Moving contexts do affect the perceived direction of apparent motion in motion competition displays.

Three experiments were performed to test Ullman's [The Interpretation of Visual Motion. MIT Press, Cambridge, Mass. (1979)] independence hypothesis, used in the minimal mapping theory of motion correspondence. Subjects were required to detect the direction of motion (left vs right) of an element in a motion competition display. In control conditions, threshold interelement distances were obtained for this task in the absence of any moving context. In experimental conditions, context elements that moved either to the left or to the right were added to the display. This resulted in changes in thresholds (relative to the control condition) that indicated that a context moving in one direction increased the probability of seeing the competition element move in the same direction. The magnitude of the context effect was shown to be related to the proximity of the context to the competition display, as well as to the number of elements in the context. These results are in conflict with Ullman's independence hypothesis. An alternative model of the motion correspondence process, which uses information about interdependencies between element movements, is briefly discussed.

Humans↗
PubMed1990

Influence of visual blur on object-motion detection, self-motion detection and postural balance.

We have compared the influence of visual blurring (either by use of plastic foils or by plus lenses) on detection of object-motion and self-motion, and on visual control of postural balance. Three experiments were performed--in all of which object-motion and self-motion detection latencies (response times) and postural sway (sway path) increased with increasing visual blurring. We conclude that visual blurring either by foils or by glasses affects object- and self-motion perception and postural sway in a similar way.

Attention↗
PubMed2005

Measurement of cervical range of motion pattern during cyclic neck movement by an ultrasound-based motion system.

Goniometers and radiographic imaging have been used to measure active or passive cervical range of motion (ROM) in asymptomatic adults. However, the ultrasound-based coordinate measuring system (CMS) can measure continuous neck motion in three dimensions. The aims of this investigation are to evaluate the reliability and validity of ultrasound-based CMS (Zebris, CMS 70P), and to compare the cervical ROM patterns of asymptomatic young and middle-aged adults during continuous neck motions in the three cardinal planes. The ROM reciprocal ratio was defined as the ratio of the ROM from neutral position in one direction versus that in the opposite direction at the same cardinal plane. This study demonstrated the high test-retest reliability and validity of CMS during cervical motion in Chinese participants. Middle-aged adults exhibit reduced ROM ratios in the sagittal and frontal planes. The advantages and limitations of the CMS measurement tool and the potential future applications are documented. The measurement of neck motion pattern by ultrasound-based CMS may provide information on the management of neck dysfunction during functional movements.

Adult↗
PubMed2004

Attention-based motion perception and motion adaptation: what does attention contribute?

Attention-based motion perception refers to the phenomenon that a stimulus with ambiguous motion energy can be seen to move in a direction that is under attentive control of the observer. The role of attention is obvious when the stimulus is ambiguous: it makes the stimulus move in one direction. The goal of the current experiment is to investigate what the contribution of attention under attentive tracking conditions actually is, especially while viewing-time progresses. We had our observers look at a circular array of four evenly spaced discs whose motion direction was biased in the clockwise direction. Observers either viewed the stimulus moving around a circular path passively or actively. In the latter case they attentively tracked one of the discs. The observer's task was to indicate the perceived direction of motion. As time progresses, this kind of stimulus will undergo spontaneous motion direction reversals. We analyzed the time course of the reversals and show that actively attentive tracking the stimulus massively delays the reversal time. These results suggest that attention can temporarily overrule lower level adaptation.

Adaptation, Physiological↗
PubMed2005

Illusory rebound motion and the motion continuity heuristic.

A new motion illusion, "illusory rebound motion" (IRM), is described. IRM is qualitatively similar to illusory line motion (ILM). ILM occurs when a bar is presented shortly after an initial stimulus such that the bar appears to move continuously away from the initial stimulus. IRM occurs when a second bar of a different color is presented at the same location as the first bar within a certain delay after ILM, making this second bar appear to move in the opposite direction relative to the preceding direction of ILM. Three plausible accounts of IRM are considered: a shifting attentional gradient model, a motion aftereffect (MAE) model, and a heuristic model. Results imply that IRM arises because of a heuristic about how objects move in the environment: In the absence of countervailing evidence, motion trajectories are assumed to continue away from the location where an object was last seen to move.

Color Perception↗
PubMed2005

Large shifts in perceived motion direction reveal multiple global motion solutions.

Moving objects are thought to be decomposed into one-dimensional motion components by early cortical visual processing. Two rules describing how these components might be re-combined to produce coherent object motion are the intersection of constraints and the vector average rules. Using stimuli for which these combination rules predict different directional solutions, we found that adapting one of the solutions through motion adaptation switched perceived direction to the other solution. The effects were symmetrical: shifts from IOC to VA, and from VA to IOC, were observed following adaptation. These large shifts indicate that multiple solutions to global motion processing coexist and compete to determine perceived motion direction.

Adaptation, Psychological↗
PubMed2001

The stereoscopic (cyclopean) motion aftereffect is dependent upon the temporal frequency of adapting motion.

This study investigated whether the stereoscopic (cyclopean) motion aftereffect (induced by adaptation to moving binocular disparity information) is dependent upon the temporal frequency or speed of adapting motion. The stereoscopic stimuli were gratings created from disparity embedded in a dynamic random-dot stereogram. Across different combinations of stereoscopic spatial frequency, temporal frequency and speed of adapting motion, the duration of the aftereffect was dependent upon temporal frequency (maximal aftereffect=1-2 cyc s(-1)). These results support the idea that stereoscopic motion is processed by a cortical mechanism that computes cyclopean motion energy.

Adaptation, Physiological↗