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 55 records · Page 3Linked to original sources
PubMed2005

Changes in patterns of scaphoid and lunate motion during functional arcs of wrist motion induced by ligament division.

PURPOSE: To determine the in vitro motion of the scaphoid and lunate during wrist circumduction and wrist dart-throw motions and to see how these motions change after the ligamentous stabilizers of the scaphoid and lunate are sectioned in a manner simulating scapholunate instability. METHODS: Twenty-one fresh-frozen cadaver forearms were moved through a dart-throw motion and a circumduction motion using a wrist joint simulator. Scaphoid and lunate motion were measured with the wrist ligaments intact and after sectioning of the scapholunate interosseous ligament, the scaphotrapezium ligament, and the radioscaphocapitate ligament. RESULTS: In the intact wrist the scaphoid and lunate moved more during circumduction than during the dart-throw motion. With ligamentous sectioning the scaphoid flexed more and the lunate extended more during both the circumduction and dart-throw motions. During the circumduction motion both before and after sectioning the global motion of the scaphoid was greater than that of the lunate. After sectioning the scaphoid motion increased and the lunate motion decreased. CONCLUSIONS: The scaphoid and lunate motions were observed to change remarkably after ligamentous sectioning. The observed changes in carpal motion correlate with the clinical observation that after ligamentous injury arthritic changes occur in the radioscaphoid joint and not in the radiolunate joint. Analysis of the injured wrist in positions that combine flexion-extension and radial-ulnar deviation may allow noninvasive diagnosis of specific wrist ligament injuries.

Adult↗
PubMed2003

Induced rotational motion with nonabutting inducing and induced stimuli: implications regarding two forms of induced motion.

Induced motion is the illusory motion of a static stimulus in the opposite direction to a moving stimulus. Two types of induced motion have been distinguished: (a) when the moving stimulus is distant from the static stimulus and undergoes overall displacement, and (b) when the moving stimulus is pattern viewed within fixed boundaries that abut the static stimulus. Explanations of the 1st type of induced motion refer to mediating phenomena, such as vection, whereas the 2nd type is attributed to local processing by motion-sensitive neurons. The present research was directed to a display that elicited induced rotational motion with the characteristics of both types of induced motion: the moving stimulus lay within fixed boundaries, but the inducing and induced stimuli were distant from each other. The author investigated the properties that distinguished the two types of induced motion. In 3 experiments, induced motion persisted indefinitely, interocular transfer of the aftereffect of induced motion was limited to about 20%, and the time-course of the aftereffect of induced motion could not be attributed to vection. Those results were consistent with fixed-boundary induced motion. However, they could not be explained by local processing. Instead, the results might reflect the detection of object motion within a complex flow-field that resulted from the observer's motion.

Humans↗
PubMed1999

Induced motion at texture-defined motion boundaries.

When a static textured background is covered and uncovered by a moving bar of the same mean luminance we can clearly see the motion of the bar. Texture-defined motion provides an example of a naturally occurring second-order motion. Second-order motion sequences defeat standard spatio-temporal energy models of motion perception. It has been proposed that second-order stimuli are analysed by separate systems, operating in parallel with luminance-defined motion processing, which incorporate identifiable pre-processing stages that make second-order patterns visible to standard techniques. However, the proposal of multiple paths to motion analysis remains controversial. Here we describe the behaviour of a model that recovers both luminance-defined and an important class of texture-defined motion. The model also accounts for the induced motion that is seen in some texture-defined motion sequences. We measured the perceived direction and speed of both the contrast envelope and induced motion in the case of a contrast modulation of static noise textures. Significantly, the model predicts the perceived speed of the induced motion seen at second-order texture boundaries. The induced motion investigated here appears distinct from classical induced effects resulting from motion contrast or the movement of a reference frame.

Humans↗
PubMed2006

When motion appears stopped: stereo motion standstill.

Motion standstill is different from the usual perceptual experiences associated with objects in motion. In motion standstill, a pattern that is moving quite rapidly is perceived as being motionless, and yet its details are not blurred but clearly visible. We revisited motion standstill in dynamic random-dot stereograms similar to those first used by Julesz and Payne [Julesz B, Payne R (1968) Vision Res 8:433-444]. Three improvements were made to their paradigm to avoid possible confounds: The temporal frequency of the motion stimuli was manipulated independently from that of individual stereo gratings so that the failure of motion perception is not due to inability to compute stereo. The motion of the stereo gratings was continuous across the visual field so that the perceived pattern in motion standstill was not a simple average of a back-and-forth display wobble over time. Observers discriminated three spatial frequencies to demonstrate pattern recognition. Three objective psychophysical methods, instead of merely self-report, were used to objectively demonstrate motion standstill. Our results confirm that motion standstill occurs in dynamic random-dot stereogram motion displays at 4-6 Hz. Motion standstill occurs when the stimulus spatiotemporal frequency combination exceeds that of the salience-based third-order motion system in a spatiotemporal frequency range in which the shape and depth systems still function. The ability of shape systems to extract a representative image from a series of moving samples is a significant component of a biological system's ability to derive a stable perceptual world from a constantly changing visual environment.

Adult↗
PubMedDate not supplied

How can a patient blind to radial motion discriminate shifts in the center-of-motion?

Within biologically constrained models of heading and complex motion processing, localization of the center-of-motion (COM) is typically an implicit property arising from the precise computation of radial motion direction associated with an observer's forward self-motion. In the work presented here we report psychophysical data from a motion-impaired stroke patient, GZ, whose pattern of visual motion deficits is inconsistent with this view. We show that while GZ is able to discriminate direction in circular motions she is unable to discriminate direction in radial motion patterns. GZ's inability to discriminate radial motion is in stark contrast with her ability to localize the COM in such stimuli and suggests that recovery of the COM does not necessarily require an explicit representation of radial motion direction. We propose that this dichotomy can be explained by a circular template mechanism that minimizes a global motion error relative to the visual motion input, and we demonstrate that a sparse population of such templates is computationally sufficient to account for human psychophysical performance in general and in particular, explains GZ's performance. Recent re-analysis of the predicted receptive field structures in several existing heading models provides additional support for this type of circular template mechanism and suggests the human visual system may have available circular motion mechanisms for heading estimation.

Discrimination, Psychological↗
PubMed2002

Perception of biological motion without local image motion.

A vivid perception of the moving form of a human figure can be obtained from a few moving light points on the joints of the body. This is known as biological motion perception. It is commonly believed that the perception of biological motion rests on image motion signals. Curiously, however, some patients with lesions to motion processing areas of the dorsal stream are severely impaired in image motion perception but can easily perceive biological motion. Here we describe a biological motion stimulus based on a limited lifetime technique that tests the perception of a moving human figure in the absence of local image motion. We find that subjects can spontaneously recognize a moving human figure in displays without local image motion. Their performance is very similar to that for classic point-light displays. We also find that tasks involving the discrimination of walking direction or the coherence of a walking figure can be performed in the absence of image motion. Thus, although image motion may generally aid processes such as segmenting figure from background, we propose that it is not the basis for the precept of biological motion. Rather, we suggest biological motion is derived from dynamic form information on body posture evolving over time.

Humans↗
PubMed2006

Quantifying biomechanical motion using Procrustes motion analysis.

The ability to quantify and compare the movements of organisms is a central focus of many studies in biology, anthropology, biomechanics, and ergonomics. However, while the importance of functional motion analysis has long been acknowledged, quantitative methods for identifying differences in motion have not been widely developed. In this article, we present an approach to the functional analysis of motion and quantification of motion types. Our approach, Procrustes Motion Analysis (PMA) can be used to distinguish differences in cyclical, repeated, or goal-directed motions. PMA exploits the fact that any motion can be represented by an ordered sequence of postures exhibited throughout the course of a motion. Changes in posture from time step to time step form a trajectory through a multivariate data space, representing a specific motion. By evaluating the size, shape, and orientation of these motion trajectories, it is possible to examine variation in motion type within and among groups or even with respect to continuous variables. This represents a significant analytical advance over current approaches. Using simulated and digitized data representing cyclical, repeated and goal-directed motions, we show that PMA correctly identifies distinct motion tasks in these data sets.

Animals↗
PubMed1995

The effects of motion direction, body axis, and posture on motion sickness induced by low frequency linear oscillation.

BACKGROUND: A recent experiment demonstrated that low frequency linear oscillation through the Z-axis of the body was more nauseogenic when applied in the vertical direction, with subjects seated upright, than in the horizontal direction, with subjects supine. HYPOTHESIS: The nauseogenicity of low frequency linear oscillatory motion is dependent on direction of motion with respect to the gravity vector, orientation of body axis with respect to motion, and body posture. METHODS: The following conditions were compared: A) seated upright, with horizontal motion, X-axis; B) seated upright, with vertical motion, Z-axis; and C) supine, with vertical motion, X-axis. Sinusoidal motion at 0.35 Hz, 3.6 m.s-2 peak was used in all conditions. Two experiments were performed. In Experiment 1 subjects (n = 28) were exposed to conditions A and B. In Experiment 2 subjects (n = 12) were exposed to conditions A, B and C. RESULTS: Horizontal motion (condition A) was found to be twice as nauseogenic (p < 0.05 to p < 0.0001) as vertical motion (condition B), but there was no difference in nauseogenicity between upright and supine postures for vertical motion (condition B vs. C). Mean motion exposure times to achieve moderate nausea were: Experiment 1: A) 9.0 min.; B) 22.4 min.; Experiment 2: A) 15.3 min.; B) 27.1 min.; C) 22.5 min. CONCLUSIONS: These results, taken together with those of the previous experiment, suggest that upright vs. supine body posture and stimulation through X- vs. Z-axis, both enhance the nauseogenicity of low frequency linear oscillation, these effects are additive, but that motion direction with respect to the gravity vector (horizontal vs. vertical) is a less important factor.

Adult↗
PubMed1995

Motion aftereffect with flickering test patterns reveals higher stages of motion processing.

A series of experiments was conducted to clarify the distinction between motion aftereffects (MAEs) with static and counterphasing test patterns (static and flicker MAEs). It was found that while the motion of higher-order structure, such as areas defined by texture, flicker, or stereoscopic depth, induces little static MAE, such motion reliably generates flicker MAE. It was also found that static and flicker MAEs were induced in opposite directions for stimuli in which first- and second-order structures moved in opposite directions (compound graftings of 2f + 3f or 2f + 3f + 4f, shifting a half cycle of 2f). When the test was static, MAE was induced in the direction opposite to the first-order motion; but when the test was counterphasing, MAE was induced in the direction opposite to the second-order motion. This means that static MAE is predominantly induced by first-order motion, but that flicker MAE is affected strongly by second-order motion, along with first-order motion. The present results suggest that static MAE primarily reflects adaptation of a low-level motion mechanism, where first-order motion is processed, while flicker MAE reveals a high-level motion processing, where both first- and second-order motion signals are available.

Adaptation, Ocular↗
PubMed2004

Patterns of motion loss in subjects with idiopathic loss of shoulder range of motion.

BACKGROUND: Subjects with idiopathic loss of shoulder motion have difficulty sleeping, performing overhead activities, and completing activities of daily living. Treatment has been variable in approach and success. Cyriax's proposed shoulder capsular pattern was external rotation most limited followed by abduction followed by internal rotation. This investigation was performed to determine if a consistent pattern of motion loss was present in subjects with idiopathic loss of shoulder motion. METHODS: Repeated measurement of 25 (22 female) subjects' bilateral shoulder patterns of motion were compared. The three-dimensional position of the scapula and humerus throughout active shoulder abduction, external rotation, flexion, internal rotation, and scapular plane abduction was evaluated with an electromagnetic motion capture system. Patterns of motion loss were determined for both shoulders. The proportions of peak shoulder motion to mean maximum non-involved shoulders abduction, external, and internal rotation were utilized to determine the pattern of motion loss. FINDINGS: There was a significant difference in motion loss patterns between the involved and non-involved shoulders with the arm at the side. The internal rotation less than abduction less than external rotation pattern was demonstrated in 14 of 25 (56%) involved shoulders. No pattern was present in 14 of 21 (67%) non-involved shoulders. With the arm abducted, internal rotation was the most limited motion in 23 of 25 (92%) involved shoulders. INTERPRETATION: The results did not support Cyriax's proposed glenohumeral capsular pattern. Defining the pattern of motion loss in subjects with idiopathic loss of shoulder motion may assist in diagnosis and treatment.

Adult↗
PubMed2004

The motion-induced position shift depends on the perceived direction of bistable quartet motion.

Motion can influence the perceived position of nearby stationary objects (Nature Neuroscience 3 (2000) 954). To investigate the influence of high-level motion processes on the position shift while controlling for low-level motion signals, we measured the position shift as a function of the motion seen in a bistable quartet. In this stimulus, motion can be seen along either one or the other of two possible paths. An illusory position shift was observed only when the flashes were adjacent to the path where motion was perceived. If the flash was adjacent to the other path, where no motion was perceived, there was no illusory displacement. Thus for the same physical stimulus, a change in the perceived motion path determined the location where illusory position shifts would be seen. This result indicates that high-level motion processes alone are sufficient to produce the position shift of stationary objects. The effect of the timing of the test flash between the onset and offset of the motion was also examined. The position shifts were greatest at the onset of motion, then decreasing gradually, disappearing at the offset of motion. We propose an attentional repulsion explanation for the shift effect.

Attention↗
PubMed2005

Psychophysical evidence for a radial motion bias in complex motion discrimination.

In a graded motion pattern task we measured observers' ability to discriminate small changes in the global direction of complex motion patterns. Performance varied systematically as a function of the test motion (radial, circular, or spiral) with thresholds for radial motions significantly lower than for circular motions. Thresholds for spiral motions were intermediate. In all cases thresholds were lower than for direction discrimination using planar motions and increased with removal of the radial speed gradient, consistent with the use of motion pattern specific mechanisms that integrate motion along complex trajectories. The radial motion bias and preference for speed gradients observed here is similar to the preference for expanding motions and speed gradients reported in cortical area MSTd, and may suggest the presence of comparable neural mechanisms in the human visual motion system.

Differential Threshold↗
PubMed2001

Motion adaptation in chromatic motion-onset visual evoked potentials.

The aim of this study was to investigate the influence of motion adaptation on visual evoked potentials (VEPs) elicited by the onset of isoluminant chromatic motion. VEPs were recorded from the occipital cortex of human subjects using a sinusoidal grating stimulus of one cycle per degree which moved at either a velocity of 2 or 10 degrees/s and subtended a field of 7 degrees with a mean luminance of 30 cdm(-2). In the first experiment the effects of adaptation were investigated via the manipulation of the stimulus duty cycle which was varied between 11-90%. The results showed a significant (p < 0.001) reduction in the N2-P2 amplitude of the chromatic response. In contrast, P1-N2 amplitude was not significantly affected by motion adaptation. Subsequent experiments demonstrated that the chromatic motion onset VEP was attenuated not only following adaptation to isoluminant chromatic motion, but also to luminance motion as well. These results indicate that the chromatic motion onset VEP is just as susceptible as its luminance counterpart to motion after effects (MAEs) and as a result it is highly likely that it is a motion specific response. Furthermore, the fact that the VEP shows that there are cross-adaptation effects between motion defined by change in colour and by change in luminance, suggests that the two types of motion stimuli have inputs into a common motion mechanism.

Adaptation, Ocular↗
PubMed2005

What learning to see arbitrary motion tells us about biological motion perception.

In separate studies, observers viewed upright biological motion, inverted biological motion, or arbitrary motion created from systematically randomizing the positions of point-light dots. Results showed that observers (a) could learn to detect the presence of arbitrary motion, (b) could not learn to discriminate the coherence of arbitrary motion, although they could do so for upright biological motion, (c) could apply a detection strategy to learn to detect the presence of inverted biological motion nearly as well as they detected upright biological motion, and (d) performed better discriminating the coherence of upright biological motion compared with inverted biological motion. These results suggest that learning and form information play an important role in perceiving biological motion, although this role may only be apparent in tasks that require processing information from multiple parts of the motion display.

Attention↗
PubMed2006

Defining the nature of motion perception deficits in glaucoma using simple and complex motion stimuli.

PURPOSE: The purpose of this study is to determine the nature of motion perception deficits in primary open-angle glaucoma by measuring the sensitivity of simple (luminance-defined) and complex (texture-defined) motion, the latter requiring supplementary neural processing to be resolved. These findings will help address the possible extent of the cortical damage in glaucoma that has been recently demonstrated by anatomic and physiological studies. They also serve the purpose of establishing which motion paradigms would be most appropriate for assessing glaucoma-related functional loss. METHODS: Direction-identification thresholds for first-order and second-order motion were measured for 26 patients with primary open-angle glaucoma (for both phakic and pseudophakic) and 18 nonglaucomatous observers. RESULTS: The glaucomatous observers showed significantly increased motion thresholds for both first- and second-order motion conditions when compared with nonglaucomatous observers. However, the relative increase in threshold for first-order motion did not differ significantly from that of second-order motion. CONCLUSIONS: These findings imply that there is no measurable higher-level cortical function damage caused by the glaucomatous process because no greater loss in second-order motion was observed. Based on the results, we suggest that motion paradigms used to assess functional loss in primary open-angle glaucoma should consist of simple, first-order type stimuli to minimize potential confounds such as those introduced by both the normal and pathologic aging process on complex motion processing (i.e., perimetry using complex motion stimuli).

Aged↗
PubMed1993

The interaction of luminance, velocity, and shape information in the perception of motion transparency, coherence, and non-rigid motion.

The perception of luminance transparency for superimposed patterns depends on how luminance, figural, and topological conditions are simultaneously satisfied. Motion transparency or coherence for two superimposed patterns, which correspond to the perception of both patterns moving across one another or to the perception of compound motion of the regions of pattern intersection, depends on the relation between the local velocity, luminance, and shape information. This study analyzes how luminance, shape, and local velocity interact in the perception of motion transparency and coherence. Psychophysical experiments done with sinusoidally modulated bar patterns are presented which show that the perception of motion transparency or coherence can be described as the result of the interaction of two integration modules: the velocity-luminance and the velocity-shape processes. The velocity-luminance process describes the integration of the local velocity with luminance information. When the luminance transparency rules are satisfied this process always generates the perception of motion transparency independently of the shape or contour information. On the other hand, when the luminance transparency rules are violated one can either perceive motion coherence or non-rigid motion; one perceives motion coherence when the patterns have small or zero amplitude, and non-rigid motion when the patterns have large amplitude. The velocity-shape process describes the integration of local velocity with shape information, and this depends on the relation between the error in the extraction of the local velocity and the magnitude of the contour amplitude. As a result of these experiments it is conjectured that the velocity-luminance and the velocity-shape processes do interact constructively or destructively. The constructive interaction occurs when the luminance transparency rules are satisfied. The destructive interaction occurs when the luminance transparency rules are violated, and such that, although the patterns contain sufficient shape information to solve the aperture problem and therefore generate the perception of motion transparency, one perceives non-rigid motion. This shows that global information describing the stratification of superimposed patterns can affect the integration of local velocity information with, for example, shape information, and this is not described by current motion theories.

Form Perception↗
PubMed2003

Motion adaptation shifts apparent position without the motion aftereffect.

Adaptation to motion can produce effects on both the perceived motion (the motion aftereffect) and the position (McGraw, Whitaker, Skillen, & Chung, 2002; Nishida & Johnston, 1999; Snowden, 1998; Whitaker, McGraw, & Pearson, 1999) of a subsequently viewed test stimulus. The position shift can be interpreted as a consequence of the motion aftereffect. For example, as the motion within a stationary aperture creates the impression that the aperture is shifted in position (De Valois & De Valois, 1991; Hayes, 2000; Ramachandran & Anstis, 1990), the motion aftereffect may generate a shift in perceived position of the test pattern simply because of the illusory motion it generates on the pattern. However, here we show a different aftereffect of motion adaptation that causes a shift in the apparent position of an object even when the object appears stationary and is located several degrees from the adapted region. This position aftereffect of motion reveals a new form of motion adaptation--one that does not result in a motion aftereffect--and suggests that motion and position signals are processed independently but then interact at a higher stage of processing.

Attention↗
PubMed1992

Lumbar motion trends and correlation with low back pain. Part II. A roentgenological evaluation of quantitative segmental motion in lateral bending.

OBJECTIVE: A radiographic study was undertaken to describe the relationship between the magnitude of coupled lumbar motion in lateral bending and the presence of low back pain: correlation between pain and motion, relationship between motion category and motion and symmetry of lumbar motion. DESIGN: Survey. SETTING: Chiropractic college student health center and private chiropractic clinic. PARTICIPANTS: 249 subjects: 114 with low back pain, 29 asymptomatic with no history and 106 asymptomatic with history. Of these, 194 were freshman volunteers and 55 were new private clinic low back pain patients. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Net lumbar segmental tilt and rotation in lateral bending: corrected and uncorrected for segmental malposition with the patient standing in the upright neutral position. RESULTS: Statistical analysis demonstrated no significant relationship between coupled lumbar motion and low back pain (p greater than .01). The presence of type II motion could account for, on average, less than 5% loss of segmental tilt in the lumbar spine. Asymmetries between left and right side motion averaged 45 to 100% of unilateral range of motion. CONCLUSIONS: This study suggests that back pain is not an indication for the routine use of lateral bending films for the identification of alterations in the magnitude of lumbar segmental motion in lateral bending. It further indicates that type II motion cannot be ruled out as a normal variant. The paucity of symmetrical lumbar motion suggests that segmental tilt or coupled rotation asymmetry, in and of itself, should not be considered an indication for spinal manipulation.

Adolescent↗