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At least 289 records · Page 16Linked to original sources
PubMed2006

Type of motion in inverted self-motion perception induced by a foreground stimulus.

Slowly moving foreground induces an illusory self-motion perception in the same direction as its motion direction (inverted vection). In this study, the effects of motion type of the foreground stimulus on inverted vection were investigated using a sample of 3 men and 1 woman. As indices of perceived strength of the inverted vection, duration and estimated magnitude were measured. Analysis of the psychophysical experiment indicated that a translating foreground induced inverted linear vection in the same direction as the stimulus motion. However, a rotating foreground did not induce an inverted roll vection. Statistical analyses indicate that there is a significant difference between two foreground motion conditions (Duration: t3=14.54, p <.01; Estimation: t3=16.92, p<.01). This result supports the hypothesis that eye-movement information is responsible for the occurrence of inverted vection.

Adult↗
PubMed1994

Intraobserver and interobserver reliability of asymptomatic subjects' thoracolumbar range of motion using the OSI CA 6000 Spine Motion Analyzer.

Because spinal range of motion (ROM) is assessed routinely in clinical and research settings, a technique is needed that can be performed comfortably, quickly, and reliably. The purpose of this study was to determine if ROM data from asymptomatic subjects measured with the OSI CA 6000 Spine Motion Analyzer (OSI SMA) are reliable within and between observers. Thoracolumbar ROM, from approximately T7 to S2, was measured in all three planes in eight male and 13 female asymptomatic adult subjects (mean age = 29.7 years, SD = 5.6; mean height = 1.7 m, SD = 3.4, mean weight = 78.25 kg, SD = 34.6). A standardized protocol was used to fit each subject with appropriate hardware. Foot placement at a comfortable foot angle was standardized by the use of a template. Subjects performed three practice trials of flexion, extension, right and left sidebending, and right and left rotation. During testing, subjects performed four trials of each maximal pain-free motion. The hardware was completely removed and replaced by the same examiner, and ROM trials in all three planes were repeated. The same procedure was completed by a second examiner. Repeated measures analysis of variance and intraclass correlation coefficients (ICC [2,1] were used to analyze intra- and interobserver data. Intraobserver ICCs were 0.89 or higher for all motions. Interobserver ICCs were 0.85 or higher for all motions. Measurements of thoracolumbar ROM using the OSI SMA are sufficiently reliable within and between observers for clinical assessment and research purposes.

Adult↗
PubMed1999

Reproducibility of lumbar spine range of motion measurements using the back range of motion device.

STUDY DESIGN: Single-group repeated measures for single rater reliability. OBJECTIVES: To describe the intratester reliability for measurements of active lumbar spine mobility and pelvic inclination during standing obtained with the back range-of-motion (BROM) device. BACKGROUND: The BROM device has often been used to quantify lumbar spine active range of motion. No studies have reported the reliability of the BROM device in a clinical setting. METHODS AND MEASURES: One examiner measured all 3 planes of lumbar range of motion in 40 nonimpaired subjects. For each plane of motion, 2 BROM device measurements were made. Intraclass correlation coefficients were calculated to express the intratester reliability for each plane of motion measured. RESULTS: Intraclass correlation coefficients were in the range of 0.67 to 0.94 for lumbar measurements with the BROM device. CONCLUSIONS: Intratester reliability was fair to poor for sagittal plane measurements and pelvic inclination. Measurements obtained by the same examiner for lumbar lateral flexion and rotation with the BROM device, however, were reliable.

Adult↗
PubMed1998

Opponent motion interactions in the perception of transparent motion.

Interactions in the perception of motion transparency were investigated using a signal-detection paradigm. The stimuli were the linear sum of two independent, moving, random-check "signal" textures and a third texture consisting of dynamic random "noise." Performance was measured as the ratio of squared signal and noise contrasts was varied (S2/N2). Motion detectability was poorest when the two signal textures moved in opposite directions (180 degrees), intermediate when they moved in the same direction (0 degrees), and best when the textures moved in directions separated by 90 degrees in the stimulus plane. This pattern of results held across substantial variations in velocity, field size, duration, and texture-element size. Motion identification was also impaired, relative to 0 degrees, in the 180 degrees but not in the 90 degrees condition. These results are consistent with the idea that performance in the opponent-motion condition is limited by inhibitory (or suppressive) interactions. These interactions, however, appear to be direction specific: little, if any, inhibition was observed for perpendicular motion.

Humans↗
PubMed1988

Three-dimensional spinal motion measurements. Part 1: A technique for examining posture and functional spinal motion.

This study examines the application of a new noninvasive technology capable of accurately, reproducibly, and reliably measuring spinal motion, in real time, with 3 df. The mean values and SD of range of motion in the lumbar, thoracic, and cervical regions compares favorably with results reported by other authors. Pearson correlations yielded a statistically significant weak inverse relationship between age and range of motion in the sagittal and frontal planes (p less than .02). No correlation between sex, height, or weight and range of motion was found. There was no statistically significant evidence of organized coupling. However, a relationship between rotation and lateral motion in the thoracic region was noted.

Aging↗
PubMed1995

[Motion discrimination as as test for visual motion perception].

Recent neurophysiological studies have indicated that there are two parallel pathways in vision processing independently shape and motion. There are many methods for examining perception of color and shape, but none for examining visual motion perception. In this study, we devised a "motion discrimination task (MDT)" for evaluating motion perception, which was displayed on a computer monitor, and recorded normal responses to the MDT in 90 normal subjects. Responses to MDT were not affected by visual acuity, but were affected by dot speed of the MDT. There was little trial-to-trial or subject variability in the MDT. These findings indicate that our MDT is a good clinical test for evaluating motion perception in human subjects.

Adolescent↗
PubMed1999

Motion correction with PROPELLER MRI: application to head motion and free-breathing cardiac imaging.

A method for motion correction, involving both data collection and reconstruction, is presented. The PROPELLER MRI method collects data in concentric rectangular strips rotated about the k-space origin. The central region of k-space is sampled for every strip, which (a) allows one to correct spatial inconsistencies in position, rotation, and phase between strips, (b) allows one to reject data based on a correlation measure indicating through-plane motion, and (c) further decreases motion artifacts through an averaging effect for low spatial frequencies. Results are shown in which PROPELLER MRI is used to correct for bulk motion in head images and respiratory motion in nongated cardiac images. Magn Reson Med 42:963-969, 1999.

Artifacts↗
PubMed2000

Assessment of elbow joint kinematics in passive motion by electromagnetic motion tracking.

This research provides a detailed analysis of the kinematics of passive elbow motion. It quantifies how closely humeroulnar kinematics approximates rotation around a fixed axis. The results are clinically relevant for emerging treatment modalities that impose an artificial hinge to the elbow joint, such as total elbow arthroplasty and articulated external fixation. In a cadaveric study of seven specimens, we quantified ulnar rotation around the humerus in terms of instantaneous screw displacement axes calculated from electromagnetic motion-tracking source data. This methodology enabled description of the complex excursion of the elbow axis in terms of translation and orientation changes of the screw displacement axes over the range of motion. Furthermore, we analyzed the envelope of joint laxity for elbow motion under applied small varus and valgus moments. In addition, radiographic landmarks of clinical utility for axis location were evaluated by visualizing the elbow's radiographic appearance when viewed from along the calculated best-fit (average) rotation axis. Over the normal range of elbow motion, the screw displacement axis varied 2.6-5.7 degrees in orientation and 1.4-2.0 mm in translation. All instantaneous rotation axes nearly intersected on the medial facet of the trochlea. The breadth of the envelope of varus-valgus joint laxity was greatest within the initial 40 degrees of flexion and decreased by a factor of approximately two for flexion angles exceeding 100 degrees.

Arthroplasty↗
PubMed1989

Cardiac cycle-dependent variation of integrated backscatter is not distorted by abnormal myocardial wall motion in human subjects with paradoxical septal motion.

To define the dependence of cardiac cycle-dependent variation of integrated backscatter on regional myocardial wall motion, 8 children mean age 10.6 +/- 1.3 y with congenital cardiac lesions associated with paradoxical septal motion were studied (study group). Six healthy children mean age 9.0 +/- 0.3 y with no history of cardiac disease served as controls (control group). Subjects in the study group had paradoxical septal motion but normal septal wall thickening detected by conventional two-dimensional and M-mode echocardiography. The control group had normal septal motion evident by conventional echocardiographic criteria. The percentage of systolic septal thickening was 46 +/- 4.5% and 42 +/- 5.9% in the study and control groups (p = NS). Cyclic variation was measured in parasternal long-axis views from several septal sites in each subject. Mean values of the magnitude of cyclic variation from independent septal sites were averaged to yield a regional average value for each subject. The average regional magnitude of cyclic variation was 8.3 +/- 1.0 dB and 5.7 +/- 0.4 dB in the study and control groups (p = NS). The results indicate that the measurement of cyclic variation of integrated backscatter is not distorted by altered regional wall motion, and that it reflects intrinsic contractile function.

Child↗
PubMed2004

Trajectory of coronary motion and its significance in robotic motion cancellation.

OBJECTIVES: To characterize remaining coronary artery motion of beating pig hearts after stabilization with an 'Octopus' using an optical remote analysis technique. METHODS: Three pigs (40, 60 and 65 kg) underwent full sternotomy after receiving general anesthesia. An 8-bit high speed black and white video camera (50 frames/s) coupled with a laser sensor (60 microm resolution) were used to capture heart wall motion in all three dimensions. Dopamine infusion was used to deliberately modulate cardiac contractility. Synchronized ECG, blood pressure, airway pressure and video data of the region around the first branching point of the left anterior descending (LAD) coronary artery after Octopus stabilization were captured for stretches of 8 s each. Several sequences of the same region were captured over a period of several minutes. Computerized off-line analysis allowed us to perform minute characterization of the heart wall motion. RESULTS: The movement of the points of interest on the LAD ranged from 0.22 to 0.81 mm in the lateral plane (x/y-axis) and 0.5-2.6 mm out of the plane (z-axis). Fast excursions (>50 microm/s in the lateral plane) occurred corresponding to the QRS complex and the T wave; while slow excursion phases (<50 microm/s in the lateral plane) were observed during the P wave and the ST segment. The trajectories of the points of interest during consecutive cardiac cycles as well as during cardiac cycles minutes apart remained comparable (the differences were negligible), provided the hemodynamics remained stable. Inotrope-induced changes in cardiac contractility influenced not only the maximum excursion, but also the shape of the trajectory. Normal positive pressure ventilation displacing the heart in the thoracic cage was evident by the displacement of the reference point of the trajectory. CONCLUSIONS: The movement of the coronary artery after stabilization appears to be still significant. Minute characterization of the trajectory of motion could provide the substrate for achieving motion cancellation for existing robotic systems. Velocity plots could also help improve gated cardiac imaging.

Animals↗
PubMed2001

New method of on-line quantification of regional wall motion with automated segmental motion analysis.

We have recently developed an automated segmental motion analysis (A-SMA) system, based on an automatic "blood-tissue interface" detection technique, to provide real-time and on-line objective echocardiographic segmental wall motion analysis. To assess the feasibility of A-SMA in detecting regional left ventricular (LV) wall motion abnormalities, we performed 2-dimensional echocardiography with A-SMA in 13 healthy subjects, 22 patients with prior myocardial infarction (MI), and 9 with dilated cardiomyopathy (DCM). Midpapillary parasternal short-axis and apical 2- and 4-chamber views were obtained to clearly trace the blood-tissue interface. The LV cavity was then divided into 6 wedge-shaped segments by A-SMA. The area of each segment was calculated automatically throughout a cardiac cycle, and the area changes of each segment were displayed as bar graphs or time-area curves. The systolic fractional area change (FAC), peak ejection rate (PER), and filling rate (PFR) were also calculated with the use of A-SMA. In the control group, a uniform FAC was observed in real time among 6 segments in the short-axis view (60% +/- 10% to 78% +/- 9%), or among 5 segments in either the 2-chamber (59% +/- 12% to 75% +/- 16%) or 4-chamber view (58% +/- 13% to 72% +/- 12%). The variations of FAC, PER, and PFR were obviously decreased in infarct-related regions in the MI group and were globally decreased in the DCM group. We conclude that A-SMA is an objective and time-saving method for assessing regional wall motion abnormalities in real time. This method is a reliable new tool that provides on-line quantification of regional wall motion.

Adult↗
PubMed2005

Motion compensated coronary interventional navigation by means of diaphragm tracking and elastic motion models.

Current catheter tracking in the x-ray catheter laboratory during coronary interventions is performed using 2D fluoroscopy. Although this features real-time navigation on high-resolution images, drawbacks such as overlap and foreshortening exist and hamper the diagnosis and treatment process. An alternative to fluoroscopy-based tracking is device tracking by means of a magnetic tracking system (MTS). Having measured the 3D location of the interventional device, its position can be reconstructed on 3D images or virtual roadmaps of the organ or vessel structure under examination. In this paper, a method is presented which compensates the interventional device location measured by the MTS for organ motion and thus registers it dynamically to a 3D virtual roadmap. The motion compensation is accomplished by using an elastic motion model which is driven by the ECG signal and a respiratory sensor signal derived from ultrasonic diaphragm tracking. The model is updated during the intervention itself, thus allowing for a local refinement in regions which bear a complex geometric structure, such as stenoses and bifurcations. The evaluation is done by means of a phantom-based study using a dynamic heart-phantom. The mean displacement caused by the overall motion of the heart is improved from 10.4+/-4.8 mm in the uncompensated case to 2.1+/-1.2 mm in the motion compensated case.

Algorithms↗
PubMed2000

Impairment in motion discrimination tasks is unrelated to amount of damage to superior temporal sulcus motion areas.

The behavioral role of the middle temporal (MT/V5) area and its satellites in motion processing is still unclear, particularly the degree to which MT/V5 proper is critical for different types of motion processing. Therefore, effects of small and large lesions in the caudal part of the superior temporal sulcus of macaque monkeys were compared for two tasks requiring different types of motion processing: a direction and a kinetic orientation discrimination. The small lesion was restricted to the peripheral representation of MT/V5 but included V4t, whereas the large lesion included all of MT/V5 and the medial superior temporal (MST) area as well as substantial parts of the floor of the superior temporal (FST) area. Both lesions resulted in significant and long-lasting impairment of direction discrimination but had a lesser effect on kinetic orientation discrimination. Thus the effects of small STS lesions on motion perception are much stronger than expected.

Animals↗
PubMed1991

Energy filters, motion uncertainty, and motion sensitive cells in the visual cortex: a mathematical analysis.

Energy filters are tuned to space-time frequency orientations. In order to compute velocity it is necessary to use a collection of filters, each tuned to a different space-time frequency. Here we analyze, in a probabilistic framework, the properties of the motion uncertainty. Its lower bound, which can be explicitly computed through the Cramér-Rao inequality, will have different values depending on the filter parameters. We show for the Gabor filter that, in order to minimize the motion uncertainty, the spatial and temporal filter sizes cannot be arbitrarily chosen; they are only allowed to vary over a limited range of values such that the temporal filter bandwidth is larger than the spatial bandwidth. This property is shared by motion sensitive cells in the primary visual cortex of the cat, which are known to be direction selective and are tuned to space-time frequency orientations. We conjecture that these cells have larger temporal bandwidth relative to their spatial bandwidth because they compute velocity with maximum efficiency, that is, with a minimum motion uncertainty.

Animals↗
PubMed1999

Superior results with continuous passive motion compared to active motion after periosteal transplantation. A retrospective study of human patella cartilage defect treatment.

Fifty-seven consecutive patients (33 men and 24 women), with a mean age of 32 years (range 16-53 years), who suffered from an isolated full-thickness cartilage defect of the patella and disabling knee pain of long duration, were treated by autologous periosteal transplantation to the cartilage defect. The first 38 consecutive patients (group A) were postoperatively treated with continuous passive motion (CPM), and the next 19 consecutive patients (group B) were treated with active motion for the first 5 days postoperatively. In both groups, the initial regimens were followed by active motion, slowly progressive strength training, and slowly progressive weight bearing. In group A, after a mean follow-up of 51 months (range 33-92 months), 29 patients (76%) were graded as excellent or good, 7 patients (19%) were graded as fair, and 2 patients (5%) were graded as poor. In group B, after a mean follow-up of 21 months (range 14-28 months), 10 patients (53%) were graded as excellent or good, 6 patients (32%) were graded as fair, and 3 patients (15%) were graded as poor. Altogether, nine of the fair or poor cases (50%) were diagnosed with chondromalacia of the patella. Our results, after performing autologous periosteal transplantation in patients with full-thickness cartilage defects of the patella and disabling knee pain, are good if CPM is used postoperatively. The clinical results using active motion postoperatively are not acceptable, especially not in patients with chondromalacia of the patella.

Adult↗
PubMed1991

Motion of complex patterns is computed from the perceived motions of their components.

A plaid pattern made by adding two gratings of the same spatial frequency, one moving 45 deg above the horizontal, and the other moving 45 deg below the horizontal, appears to move horizontally when the speeds of the two components are equal. If the apparent speed of the upward-moving component is reduced by a motion after-effect (MAE), the plaid appears to move obliquely downwards, unless the actual speed of the downward-moving component is reduced to match the (reduced) apparent speed of the upward moving component. This is consistent with the hypothesis that the visual system computes the motion of a plaid pattern in two stages, first estimating the motions of the components, and then combining them according to the intersection of constraints. An alternative explanation: that the vertical component of the plaid's motion is caused by an MAE in a horizontally oriented distortion product generated by non-linear transduction or transmission of the plaid, is ruled out by the finding that the adapting stimulus causes only a very weak vertical MAE.

Adaptation, Ocular↗
PubMed1995

Motion detection in interleaved random dot patterns: evidence for a rectifying nonlinearity preceding motion analysis.

Three experiments examined direction discrimination in temporally interleaved random dot patterns. The stimulus consisted of two or more uncorrelated random patterns presented in a repeating temporal sequence, so that each pattern appeared only once every n frames, separated by uncorrelated patterns. Each pattern shifted either leftward or rightward at each re-appearance (all patterns shifted in the same direction in any one presentation). Subjects could specify shift direction correctly even when eight different patterns were interleaved, provided that the duration of each frame was brief. An explanation based on responses in first-order motion energy detectors tuned to low spatiotemporal frequencies (effectively summating the interleaved patterns over time) was tested using a stimulus in which each pattern inverted in contrast mid-way through each frame. Contrary to predictions based on temporal summation, performance with contrast-inverting patterns was only slightly lower than with non-inverting patterns. An alternative explanation was examined, based on responses in motion detectors that full-wave rectify image contrast before extracting motion energy. Computed responses from such detectors successfully predicted psychophysical performance with interleaved random patterns. Implications for models of motion analysis are discussed.

Discrimination, Psychological↗
PubMed1986

Object-motion detection affected by concurrent self-motion perception: psychophysics of a new phenomenon.

Thresholds for object-motion detection are significantly raised when concurrent self-motion perception is induced by either vestibular, or visual, or cervico-somatosensory stimulation. Active sinusoidal horizontal head oscillations with compensatory vestibulo-ocular reflex (VOR) and foveal or eccentrical target presentation; 'passive' head movements with fixation suppression of the VOR; pure body oscillations with the head fixed in space (cervical stimulation); optokinetically induced apparent self-motion (circularvection). This new visual phenomenon of a physiological 'inhibitory interaction' between object- and self-motion perception seems to have a somatosensory motor analogue. It may reflect the disadventageous side effect due to unspecificness of an otherwise beneficial space constancy mechanism, which provides us with the image of a stable world during locomotion.

Adolescent↗