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 397 records · Page 22Linked to original sources
PubMed2001

A motion aftereffect seen more strongly by the non-adapted eye: evidence of multistage adaptation in visual motion processing.

We found that the motion aftereffect measured using a directionally ambiguous counterphase grating (flicker MAE) can be stronger when it is measured for the non-adapted eye than when measured for the adapted eye. The monocularly viewed adaptation stimulus was the movement of a missing-fundamental grating (2f+3f motion), for which the movement of the higher-order spatial structure was dominantly perceived, while the first-order structure was physically moving in the opposite direction. For observers who perceived the MAE consistently in the direction opposite to the movement of the higher-order structures, the MAE was larger for the non-adapted eye than for the adapted eye. This finding of 'over-100% transfer' invalidates the standard view that the IOT is a direct measure of the binocularity of the adapted neurones. In addition, the finding provides convincing support for the hypothesis that the flicker MAE reflects adaptation at multiple processing stages

Adaptation, Physiological↗
PubMed1991

The how and why of what went where in apparent motion: modeling solutions to the motion correspondence problem.

A model that is capable of maintaining the identities of individuated elements as they move is described. It solves a particular problem of underdetermination, the motion correspondence problem, by simultaneously applying 3 constraints: the nearest neighbor principle, the relative velocity principle, and the element integrity principle. The model generates the same correspondence solutions as does the human visual system for a variety of displays, and many of its properties are consistent with what is known about the physiological mechanisms underlying human motion perception. The model can also be viewed as a proposal of how the identities of attentional tags are maintained by visual cognition, and thus it can be differentiated from a system that serves merely to detect movement.

Attention↗
PubMed1986

Illusory continuous motion from oscillating positive-negative patterns: implications for motion perception.

A black and white (positive) grating pattern was superimposed in exact register on its own photographic negative. Four operations were repetitively applied to this positive pattern so that it moved fractionally to the right, grew dimmer, moved back to the left, and grew brighter again. This sequence produced a strong illusion of continuous apparent motion to the right for as long as the cycle was repeated. The small relative motion between the two patterns generated two new illusory effects: enhanced real movement (ERM) and reversed real movement (RRM). The dimming and brightening phases gave rise to reversed apparent movement (RAM). All three effects are attributed to spatial filtering by neural mechanisms, which shifts the effective position of the positive-negative contours.

Color Perception↗
PubMed2003

The line-motion illusion can be reversed by motion signals after the line disappears.

In the line-motion illusion, a briefly flashed line appears to propagate from the locus of attention, despite being physically presented on the screen all at once. It has been proposed that the illusion reflects low-level visual information processing that occurs faster at the locus of attention (Hikosaka et al 1993 Vision Research 33 1219-1240; Perception 22 517-526). Such an explanation implicitly embeds the assumption that speeding or slowing of neural signals will map directly onto perceptual timing. This 'online' hypothesis presupposes that signals which arrive first are perceived first. However, other evidence suggests that events in a window of time after the disappearance of a visual stimulus can influence the brain's interpretation of that stimulus (Eagleman and Sejnowski 2000 Science 287 2036-2038; 289 1107a; 290 1051a; 2002 Trends in Neuroscience 25 293). If the online hypothesis were true, we should expect that events occurring after the flashing of the line would not change the illusion. Consistent with our hypothesis that awareness is an a posteriori reconstruction, we demonstrate that the perceived direction of illusory line-motion can be reversed by manipulating stimuli after the line has disappeared.

Attention↗
PubMed2000

Center of gravity motions and ankle joint stiffness control in upright undisturbed stance modeled through a fractional Brownian motion framework.

The authors modeled the center of gravity vertical projection (CG(v)) and the difference, CP - CG(v), which, combined, constitute the center of pressure (CP) trajectory, as fractional Brownian motion in order to investigate their relative contributions and their spatiotemporal articulation. The results demonstrated that CG(v) and CP - CG(v) motions are both endowed in complementary fashion with strong stochastic and part-deterministic behaviors. In addition, if the temporal coordinates remain similar for all 3 trajectories by definition, the switch between the successive control mechanisms appears for shorter displacements for CP - CG(v) and CG(v) than for CP trajectories. Results deduced from both input (CG(v)) and muscular stiffness (CP - CG(v)) thus provide insight into the way the central nervous system regulates stance control and in particular how CG and CP - CG are controlled.

Adult↗
PubMed1985

Nucleic acid binding drugs. Part XIII. Molecular motion in a drug-nucleic acid model system: thermal motion analysis of a proflavine-dinucleoside crystal structure.

The high-resolution crystal structure of the intercalation complex between proflavine and cytidylyl-3',5'-guanosine (CpG) has been studied by thermalmotion analysis. This has provided information on the translational and librational motions of individual groups in the complex. Many of these motions are similar to, though of larger magnitude than in uncomplexed dinucleosides. Pronounced librational effects were observed along the base pairs and in the plane of the drug chromophore.

Acridines↗
PubMed1993

Optical tearing in spatiotemporal boundary formation: when do local element motions produce boundaries, form, and global motion?

Perception of continuous boundaries, shape, and global motion can be produced by transformations in local elements separated in both space and time, a process here called spatiotemporal boundary formation (SBF). Prior research has shown that a broad class of element transformations gives rise to SBF. The present work used the transformation of local element displacement to explore the initiating conditions for SBF. Three experiments assessed SBF using a 10-alternative, forced-choice, shape identification task. Experiment 1a showed that large element displacements, but not small ones, produced high accuracy in shape identification. Experiment 1b tested the detectability of the small and large element displacements in an unrelated task, indicating that the results of Experiment 1a were not due to poor detectability for small displacements. Experiment 2 found no variation in SBF performance with changes in viewing distance. Experiment 3 provided evidence that initiating SBF depends on a ratio of element displacement to element separation. These results support an interpretation of SBF as a process geared to detection of object boundaries from spatiotemporal change. Initiating SBF requires transformations in local elements that are classified as spatiotemporal discontinuities (STDs). Small element displacements in a display of a given density do not register as STDs because they are classified as local deformations in an intact, implicit surface connecting visible elements. Complementarity is suggested between element changes which preserve continuity with their neighbors (optic flow) and those comprising spatiotemporal discontinuities (optic tearing). Classification of element transformations as optic flow or tearing may determine whether they provide information about surface form (e.g., through structure-from-motion) or about object boundaries, through SBF.

Form Perception↗
PubMed2006

Criterion validity study of the cervical range of motion (CROM) device for rotational range of motion on healthy adults.

STUDY DESIGN: This study compared range of motion (ROM) measurements using a cervical range of motion device (CROM) and an optoelectronic system (OPTOTRAK). OBJECTIVES: To examine the criterion validity of the CROM for the measurement of cervical ROM on healthy adults. BACKGROUND: Whereas measurements of cervical ROM are recognized as part of the assessment of patients with neck pain, few devices are available in clinical settings. Two papers published previously showed excellent criterion validity for measurements of cervical flexion/extension and lateral flexion using the CROM. METHODS AND MEASURES: Subjects performed neck rotation, flexion/extension, and lateral flexion while sitting on a wooden chair. The ROM values were measured by the CROM as well as the OPTOTRAK. RESULTS: The cervical rotational ROM values using the CROM demonstrated a good to excellent linear relationship with those using the OPTOTRAK: right rotation, r = 0.89 (95% confidence interval, 0.81-0.94), and left rotation, r = 0.94 (95% confidence interval, 0.90-0.97). Similar results were also obtained for flexion/extension and lateral flexion ROM values. CONCLUSION: The CROM showed excellent criterion validity for measurements of cervical rotation. We propose using ROM values measured by the CROM as outcome measures for patients with neck pain.

Adult↗
PubMed1994

Perceived motion in structure from motion: pointing responses to the axis of rotation.

We investigated the ability to match finger orientation to the direction of the axis of rotation in structure-from-motion displays. Preliminary experiments verified that subjects could accurately use the index finger to report direction. The remainder of the experiments studied the perception of the axis of rotation from full rotations of a group of discrete points, the profiles of a rotating ellipsoid, and two views of a group of discrete points. Subjects' responses were analyzed by decomposing the pointing responses into their slant and tilt components. Overall, the results indicated that subjects were sensitive to both slant and tilt. However, when the axis of rotation was near the viewing direction, subjects had difficulty reporting tilt with profiles and two views and showed a large bias in their slant judgments with two views and full rotations. These results are not entirely consistent with theoretical predictions. The results, particularly for two views, suggest that additional constraints are used by humans in the recovery of structure from motion.

Attention↗
PubMed1992

[Three-dimensional motion analysis of the wrist using two-directional radiography, with special reference to the motion of the scaphoid].

To clarify the motion of the scaphoid, which exhibits unique movement among the carpal bones, three-dimensional motion analysis of the wrist was conducted. Three fresh-frozen cadavers were thawed, and three-dimensional measurement was carried out using two-directional radiography. Conventional two-dimensional measurement with unidirectional radiography was also carried out for comparison with the three-dimensional measurement. After measurement, the cadavers were dissected and the anatomical findings were correlated with results of measurement. During flexion-extension movement of the wrist, the scaphoid showed flexion-extension movement accompanied by rotation around the longitudinal axis. In radio-ulnar flexion of the wrist, the scaphoid did not exhibit flexion-extension movement in such a way as reported previously, but showed rotation around the longitudinal axis. These results and the anatomical findings suggest that the rotation around the longitudinal axis in both flexion-extension movement and radio-ulnar flexion is the movement along the articular surface of the capitate.

Adult↗
PubMed1991

Adaptive motion compensation in MRI: accuracy of motion measurement.

It has been shown that magnetic resonance image data can be corrected for the effects of motion by using retrospective adaptive techniques which employ navigator (NAV) echoes. We demonstrate the accuracy with which NAV echoes can measure motion, as well as the independent nature of the respective view-to-view and intraview corrections.

Brain↗
PubMed1975

ESR spectral analysis of the molecular motion of spin labels in lipid bilayers and membranes based on a model in terms of two angular motional parameters and rotational correlation times.

Electron spin resonance (ESR) spectral line shapes are calculated for a nitroxide spin-labeled molecule undergoing rapid restricted rotations (twisting) about its long molecular axis while simultaneously tumbling within a cone. Explicit expressions are derived for the hyperfine splittings and g-values, as well as for the secular contributions to the motionally modulated linewidths. The present model is useful for analyzing the restricted twisting and tumbling motions, and rotational correlation times, of spin-labeled molecules in bilayers. Simulated spectra compare well with experimental spectra of lecithin bilayers marked with cholestane spin label, over a wide temperature range.

Cholestanes↗
PubMed1986

Otolith stimulation evokes compensatory reflex eye movements of high velocity when linear motion of the head is combined with concurrent angular motion.

Previous investigations have failed to find significant compensatory eye movements in response to linear motion of the head. However, the fact that visual acuity is essentially preserved during natural head movements, which combine both linear and angular components, is evidence that there must be compensation for linear translation. Hence we examined the lateral eye movements produced by angular oscillation, in the dark, in yaw at 0.5 and 1.5 Hz, 80 degrees/s peak, with the head both centred and positioned 30 cm eccentric from the axis of rotation in order to produce an additional linear acceleration acting tangentially. The combined stimuli produced high velocities of eye movement which were much greater than those produced by angular motion alone. The findings are evidence or a linear-compensatory reflex which is probably otolithic. The dependency of otolithic eye movements on concurrent stimulation of the semicircular canals is a possible explanation of positional nystagmus in neuro-otological disease in which it may be released by a pathological imbalance of canal function.

Adult↗
PubMed2005

Production of a range image for facial motion analysis: a method for analyzing lip motion.

To analyze the lip movement of patients with cleft lip and palate in detail, we developed a novel technique to produce a range image from a video-based motion capture system, and a unique technique to analyze lip movements in detail three-dimensionally. The accuracy of the range image obtained from the present system was investigated using a positioning actuator with a high accuracy and a known object, and by comparisons with the range images produced from a laser scanner with a cast model of a face. The lip motions of six healthy adults during phonation was analyzed.

Adult↗
PubMed2000

An assessment of alternate keyboards using finger motion, wrist motion and tendon travel.

OBJECTIVE: To assess the biomechanical impact of commercially available alternate keyboard designs.DESIGN. A repeated measures study was conducted in a laboratory setting, with planned comparisons of Pitch, Roll and Yaw angles of the keyboards. Ten keyboard conditions were tested. Dependent measures included tendon travel, wrist deviations, and wrist and finger kinematics.BACKGROUND. Various alternate keyboard designs have recently been introduced, which vary Pitch, Roll and Yaw angles, separation distance between keyboard halves, and include other novel features such as cup-shaped depressions for the keys. Yet little objective research has been conducted regarding the biomechanical implications of these various design features. This study attempts to quantify the keyboard designs in terms of several recognized risk factors associated with cumulative trauma disorders that arise with repetitive typing. METHODS: Wrist and finger goniometers were used to measure joint motions during a standardized typing task. 15 experienced typists (8 women, 7 men) served as subjects. Regression equations were used to generate estimates of tendon travel.RESULTS. Tendon travel was affected primarily by Pitch but not Roll or Yaw angles while wrist deviations responded to changes in all three angles. Males had significantly greater amount of tendon travel than female subjects; this difference was only partially accounted for by anthropometry. Differences in joint motion may have a greater impact on the amount of tendon travel.CONCLUSIONS. Alternate keyboard designs can affect tendon travel by as much as 11%. RelevanceAs various alternate keyboard designs are marketed, quantifiable biomechanical data such as that provided by this study, will help to assess their impact on the risk factors for cumulative trauma disorders.

Adult↗
PubMed2002

Correlative motions and memory effects in molecular dynamics simulations of molecules: principal components and rescaled range analysis suggest that the motions of native BPTI are more correlated than those of its mutants.

In this work MD simulations of the native bovine pancreatic trypsin inhibitor (BPTI) and 16 mutants were done in vacuum in order to study memory effects in the mutants using principal component analysis (PCA) and the rescaled range analysis (Hurst exponents). Both PCA and the rescaled range analysis support our previous proposition, based on PCA of lysozyme, that the motions of a native protein are more correlated than those of mutants. The methods are compared, the nature and applications of the rule and the role of the long-range correlations in MD time series (i.e. memory) are discussed in the context of collective motions.

Algorithms↗