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At least 1,171 records · Page 65Linked to original sources
PubMed2006

Effects of uncoupled motion on performance.

OBJECTIVES: To determine whether human exposure to vehicle motion specifically affects performance on a similar, yet uncorrelated, driving task and to observe the motion/simulator sickness symptoms that were associated with the real vehicle motion and the driving task. BACKGROUND: Past research has shown uncoupled motion can affect a person's performance on a task as well as induce motion sickness. METHODS: Ten participants (age range = 19-25 years) completed an uncorrelated driving task while seated in a stationary real vehicle and a moving real vehicle. RESULTS: The results show participants took longer to complete the motion condition, t(9) = 1.96, p < .05, and were less accurate, t(9) = 3.73, p < .05. Scores for the Motion Sickness Assessment Questionnaire, t(9) = 3.37, p < .05, and the Simulator Sickness Questionnaire, t(9) = 3.30, p < .05, were significantly higher during the motion condition. CONCLUSIONS: Performance on the task was degraded and motion sickness heightened during the motion condition. APPLICATION: This research has potential implications for military-related tasks such as operating a command and control station or controlling a remote vehicle while simultaneously being a passenger in a real vehicle, as well as for civilian applications such as interacting with a moving map navigation system while driving a car.

Adult↗
PubMed2005

Neural basis for a powerful static motion illusion.

Most people see movement in Figure 1, although the image is static. Motion is seen from black --> blue --> white --> yellow --> black. Many hypotheses for the illusory motion have been proposed, although none have been tested physiologically. We found that the illusion works well even if it is achromatic: yellow is replaced with light gray, and blue is replaced with dark gray. We show that the critical feature for inducing illusory motion is the luminance relationship of the static elements. Illusory motion is seen from black --> dark gray --> white --> light gray --> black. In psychophysical experiments, we found that all four pairs of adjacent elements when presented alone each produced illusory motion consistent with the original illusion, a result not expected from any current models. We also show that direction-selective neurons in macaque visual cortex gave directional responses to the same static element pairs, also in a direction consistent with the illusory motion. This is the first demonstration of directional responses by single neurons to static displays and supports a model in which low-level, first-order motion detectors interpret contrast-dependent differences in response timing as motion. We demonstrate that this illusion is a static version of four-stroke apparent motion.

Action Potentials↗
PubMed2007

Motion integration by neurons in macaque MT is local, not global.

Direction-selective neurons in primary visual cortex have small receptive fields that encode the motions of local features. These motions often differ from the motion of the object to which they belong and must therefore be integrated elsewhere. A candidate site for this integration is visual cortical area MT (V5), in which cells with large receptive fields compute the motion of patterns. Previous studies of motion integration in MT have used stimuli that fill the receptive field, and thus do not test whether motion information is really integrated across this whole area. For each MT neuron, we identified two regions ("patches") within the receptive field that were approximately equally effective in driving responses. We then measured responses to plaids whose component gratings overlapped within a patch, and compared them with responses to the same component gratings presented in separate patches. Cells that were selective for the direction of motion of the whole pattern when the gratings overlapped lost this selectivity when the gratings were separated and became selective instead for the direction of motion of the individual components. If MT cells simply pooled all of the inputs that endow them with a receptive field, they would encode all of the motions in the receptive field as belonging to a single object. Our results indicate instead that critical elements of the computations underlying pattern-direction selectivity in MT are done locally, on a scale smaller than the whole receptive field.

Animals↗
PubMed1999

Early motion of the ankle after operative treatment of a rupture of the Achilles tendon. A prospective, randomized clinical and radiographic study.

BACKGROUND: Different regimens of early motion of the ankle after operative treatment of a ruptured Achilles tendon have been suggested since the late 1980s. However, as far as we know, no controlled studies comparing these regimens with conventional immobilization in a cast have been reported. METHODS: In a prospective study, seventy-one patients who had an acute rupture of the Achilles tendon were randomized to either conventional postoperative management with a cast for eight weeks or early restricted motion of the ankle in a below-the-knee brace for six weeks. The brace was modified with an elastic band on the posterior surface, in a manner similar to the principle of Kleinert traction. Metal markers were placed in the tendon, and the separation between them was measured on serial radiographs during the first twelve weeks postoperatively. The patients were assessed clinically when the cast or brace was removed, at twelve weeks postoperatively, and at a median of sixteen months postoperatively. RESULTS: The separation between the markers at twelve weeks postoperatively was nearly identical in the two groups, with a median separation of 11.5 millimeters (range, zero to thirty-three millimeters) in the patients managed with early motion of the ankle and nine millimeters (range, one to forty-one millimeters) in the patients managed with a cast. The separation was primarily correlated with the initial tautness of the repair (r[S] = 0.45). No patient had excessive lengthening of the tendon. The patients managed with early motion had a smaller initial loss in the range of motion, and they returned to work and sports activities sooner than those managed with a cast. Furthermore, there were fewer visible adhesions between the repaired tendon and the skin in the patients managed with early motion, and these patients were subjectively more satisfied with the overall result. The patients in both groups recovered a median of 89 percent of strength of plantar flexion compared with that of the noninjured limb, as measured with an isometric strain-gauge at 15 degrees of dorsiflexion. The heel-rise index was similar for both groups: 0.88 for the patients managed with early motion and 0.89 for those managed with a cast. CONCLUSIONS: Early restricted motion appears to shorten the time needed for rehabilitation. There were no complications related to early motion in these patients. However, early unloaded exercises did not prevent muscle atrophy.

Achilles Tendon↗
PubMed2000

The effect of the orientation of the acetabular and femoral components on the range of motion of the hip at different head-neck ratios.

BACKGROUND: Prosthetic impingement due to poor positioning can limit the range of motion of the hip after total hip arthroplasty. In this study, a computer model was used to determine the effects of the positions of the acetabular and femoral components and of varying head-neck ratios on impingement and range of motion. METHODS: A three-dimensional generic hip prosthesis with a hemispherical cup, a neck diameter of 12.25 millimeters, and a head size ranging from twenty-two to thirty-two millimeters was simulated on a computer. The maximum range of motion of the hip was measured, before the neck impinged on the liner of the cup, for acetabular abduction angles ranging from 35 to 55 degrees and acetabular and femoral anteversion ranging from 0 to 30 degrees. Stability of the hip was estimated as the maximum possible flexion coupled with 10 degrees of adduction and 10 degrees of internal rotation and also as the maximum possible extension coupled with 10 degrees of external rotation. The effects of prosthetic orientation on activities of daily living were analyzed as well. RESULTS: Acetabular abduction angles of less than 45 degrees decreased flexion and abduction of the hip, whereas higher angles decreased adduction and rotation. Femoral and acetabular anteversion increased flexion but decreased extension. Acetabular abduction angles of between 45 and 55 degrees permitted a better overall range of motion and stability when combined with appropriate acetabular and femoral anteversion. Lower head-neck ratios decreased the range of motion that was possible without prosthetic impingement. The addition of a modular sleeve that increased the diameter of the femoral neck by two millimeters decreased the range of motion by 1.5 to 8.5 degrees, depending on the direction of motion that was studied. CONCLUSIONS: There is a complex interplay between the angles of orientation of the femoral and acetabular components. Acetabular abduction angles between 45 and 55 degrees, when combined with appropriate acetabular and femoral anteversion, resulted in a maximum overall range of motion and stability with respect to prosthetic impingement. CLINICAL RELEVANCE: During total hip arthroplasty, acetabular abduction is often constrained by available bone coverage, while femoral anteversion may be dictated by the geometry of the femoral shaft. For each combination of acetabular abduction and femoral anteversion, there is an optimum range of acetabular anteversion that allows the potential for a maximum range of motion without prosthetic impingement after total hip arthroplasty. These data can be used intraoperatively to determine optimum position.

Acetabulum↗
PubMed2006

[Application of a jaw motion tracking device that measures six degrees of freedom using optoelectronic].

PURPOSE: A jaw motion tracking device that measures six degrees of freedom has recently been developed. Understanding jaw motion is useful, but previous measurement methods were impractical for use in dental clinics. The overall aim of this study was to demonstrate the simple operation, low cost, and high precision of a recently developed jaw tracking device. In addition, this study explored its potential clinical applications. METHODS: In this study, we compared two jaw motion tracking devices: a digital system type of device and an optical type of device. First we established a baseline occlusal plane from which to measure jaw motion in the same subject with both devices. The jaw motion signals were sampled at a frequency of 100 Hz. The subjects were three healthy women (mean age +/- SD = 26.3 +/- 1.2 years) who were recruited from among the crown-and-bridge faculty of Tsurumi University of Dentistry. The jaw motions measured were open-close movement, sagittal border movement, and frontal border movement. In addition, the kinematic axis point was calculated from the sagittal border movement. Data from the digital system type of device and data from the optical device were compared. The data were selected to measure rotation and translocation, i.e. jaw position about protrusion, both laterotrusion and maximal opening of the mouth. RESULTS: The root mean square (RMS) error of position measurement was 0.163 mm with MM-JI-E and 0.178 mm with the optical type of device. The RMS error of jaw motion measurement with the optical type of device was maximum at 0.8mm and minimum at 0.1mm. This was similar to that with digital system type of jaw motion tracking device. CONCLUSION: This study showed the possibility of developing clinical applications for this jaw motion device.

Adult↗
PubMed2002

Motion sickness and vestibular hypersensitivity.

OBJECTIVE: Motion sickness is poorly understood, although it has been recognized for years as debilitating. Vestibular function is required for motion sickness to occur, but motion sickness can also be brought on without body motion. The aim of this study was to see if there was a correlation between caloric response and motion sickness susceptibility. DESIGN: One experiment was a prospective study carried out on 200 patients. A second prospective study was carried out on 121 patients. SETTING: Patients referred to our tertiary/quaternary care dizziness clinic. METHODS: In experiment 1, caloric scores in patients were correlated with symptoms of motion sickness as established by responses to a simple question. In experiment 2, caloric scores were correlated with symptomatic responses to caloric testing itself. MAIN OUTCOME MEASURES: Caloric responses of the best ear were measured according to standardized caloric evaluation methods. RESULTS: There was no correlation between motion sickness and caloric scores. There was a significant difference in caloric scores between patients made symptomatic by calorics and those who were not. CONCLUSIONS: The autonomic response seen in some patients is not triggered by a specific level of semicircular canal response (as measured by caloric testing). We hypothesize that (similar to space motion sickness) the trigger is a signal differential that arises between semicircular canals and otoliths and that some patients are unable to suppress this response. These patients often suffer motion sickness on a long-term basis.

Adult↗
PubMed2000

Influence of ankle support on joint range of motion before and after exercise: a meta-analysis.

STUDY DESIGN: Meta-analysis. OBJECTIVE: To evaluate the effects of different types of ankle support on ankle and foot joint range of motion before and after activity using meta-analysis procedures. BACKGROUND: The effects of ankle support on joint range of motion before and after exercise has been extensively studied, but the results among studies are not consistent. Obtaining knowledge from synthesizing the available literature with a meta-analysis can provide a greater understanding of these effects. METHODS AND MEASURES: A total of 253 cases from 19 studies were examined and included in this analysis. The treatment variables were ankle support with 3 levels (tape, lace-up, and semirigid) and time with 2 levels (before exercise and after exercise). Standardized effect sizes were computed for inversion, eversion, dorsiflexion, and plantar flexion range of motion to measure the difference between control and treatment groups at each point in time. Effect sizes were analyzed using a mixed-model factorial analysis of variance. RESULTS: Before exercise, the semirigid condition (-2.97 +/- 0.63) demonstrated greater restriction compared with the tape (-2.33 +/- 0.38) and lace-up conditions (-2.18 +/- 0.86) for inversion range of motion. After exercise, the semirigid condition (-3.85 +/- 0.64) restricted inversion range of motion more than the tape (-1.07 +/- 0.20) and lace-up (-1.56 +/- 0.29) conditions. No differences were found between the mean effect sizes for the tape and lace-up conditions before and after exercise. With respect to eversion range of motion, the semirigid support (-2.69 +/- 0.43) provided greater restraint compared with the tape (-1.00 +/- 0.21) and lace-up (-1.40 +/- 0.47) conditions. The lace-up condition also displayed greater support compared with tape alone. For dorsiflexion range of motion, greatest overall support was provided by the tape condition (-0.94 +/- 0.06) compared with the lace-up condition (-0.51 +/- 0.06). CONCLUSIONS: The greatest restriction of motion in the frontal plane was offered by the semirigid support condition, whereas taping offered the most support for limiting dorsiflexion range of motion. The results of this study may help clinicians make rational decisions concerning the selection of ankle appliances for preventing acute or chronic reinjury.

Adult↗
PubMed2003

Shoulder motions during the golf swing in male amateur golfers.

STUDY DESIGN: Prospective descriptive biomechanical analysis of shoulder motion in golf. OBJECTIVE: To characterize normal shoulder motion during the driving swing in male recreational golfers of various age groups. BACKGROUND: Shoulder trauma accounts for approximately 12% of all golf-related injuries. To design sport-specific rehabilitation programs for the injured golfer and exercise programs for the healthy golfer, clinicians and teachers need quantitative information describing range of motion requirements about the shoulder for the amateur player. METHOD AND MEASURE: Sixty-five male golfers were divided into 3 age groups: college, middle, and senior. A high-speed, 6-camera motion analysis system recorded 3-dimensional bilateral shoulder motion (vertical elevation, horizontal adduction, external rotation, and shoulder tum) for 3 swings of the driver. Group means for ranges and functional end points of motion were compared using a single-factor 1-way ANOVA (alpha = 0.05). RESULTS: All maximum values of shoulder motion were lower in the senior group than in the other 2 groups. At peak backswing, senior golfers exhibited 38 degrees less right-side shoulder external rotation than college golfers. However, from address, seniors horizontally abduct the right arm 18 degrees more than college golfers. In the older golfers, total range of motion was reduced for both shoulders in the vertical plane and for the left shoulder in the horizontal plane. CONCLUSIONS: This study describes shoulder motion for asymptomatic golfers of various age groups. These data may serve as a baseline reference for assessing disease- or injury-related changes in the golf swing and for designing sport-specific exercise and rehabilitation programs.

Adolescent↗
PubMed2004

Three-dimensional clavicular motion during arm elevation: reliability and descriptive data.

STUDY DESIGN: Cross-sectional. OBJECTIVES: To determine the reliability of a surface sensor measurement of clavicular motion during arm elevation and to describe 3-dimensional clavicular motion in an asymptomatic population. BACKGROUND: Abnormal scapular motion on the thorax has been implicated in shoulder pathology. Without the ability to measure clavicular motion, it is not possible to identify if abnormal scapular motions derive from the sternoclavicular or acromioclavicular joints. METHODS AND MEASURES: Thirty-nine subjects participated in the investigation, including an asymptomatic group (n = 30) and a group with a history or current symptoms of shoulder pathology (n = 9). Clavicular angles relative to the thorax were tracked with surface electromagnetic sensors on the thorax, clavicle, and humerus as subjects completed humeral flexion, scapular plane abduction, and abduction. Within-day reliability was assessed using intraclass correlation coefficients and SEM. Descriptive statistics quantified sternoclavicular joint motions for the various arm movements. RESULTS: Reliable measurements were obtained, with intraclass correlation coefficients ranging from 0.93 to 0.99, and SEMs from 0.9 degrees to 1.8 degrees. Between-day reliability SEM values were generally 2 degrees to 4 degrees. During elevation of the arm, the clavicle with respect to the thorax generally undergoes elevation (11 degrees-15 degrees maximum), retraction (15 degrees-29 degrees maximum), and posterior long-axis rotation (15 degrees-31 degrees maximum), with variability between subjects and planes of motion regarding the magnitude of motion. CONCLUSION: Rehabilitation approaches attempting to improve shoulder motion should benefit from improved knowledge of 3-dimensional contributions of the clavicle to normal and abnormal scapular kinematics.

Adolescent↗
PubMed2002

Stereoillusory motion concomitant with lateral head movements.

Stationary objects in a stereogram can appear to move when viewed with lateral head movements. This illusory motion can be explained by the motion-distance invariance hypothesis, which states that illusory motion covaries with perceived depth in accordance with the geometric relationship between the position of the stereo stimuli and the head. We examined two predictions based on the hypothesis. In Experiment 1, illusory motion was studied while varying the magnitude of binocular disparity and the magnitude of lateral head movement, holding viewing distance constant. In Experiment 2, illusory motion was studied while varying binocular disparity and viewing distance, holding magnitude of head movement constant. Ancillary measures of perceived depth, perceived viewing distance, and perceived magnitude of lateral head movement were also obtained. The results from the two experiments show that the extent of illusory motion varies as a function of perceived depth, supporting the motion-distance invariance hypothesis. The results also show that the extent of illusory motion is close to that predicted from the geometry in crossed disparity conditions, whereas it is greater than the predicted motion in uncrossed disparity conditions. Furthermore, predictions based on perceptual variables were no more accurate than predictions based on geometry.

Adult↗
PubMed2002

Integration of speed signals in the direction of motion.

Speed discrimination tasks were used to examine the spatial and temporal characteristics of the integration mechanism involved when signals are extended in the direction of motion. We varied the aspect ratio of a signal patch whose speed differed from the background, while holding the area of the signal patch constant, so that the signal patch could be either extended in the direction of motion or extended orthogonal to the direction of motion. Speed discrimination thresholds decreased dramatically as the signal patch was extended in the direction of motion. The spatial and temporal integration regions were larger than would be expected if the integration mechanism were a low-level motion detector. The mechanism was tuned for direction of motion. The data are discussed with reference to two alternative integration mechanisms: a low-level detector that is elongated in the direction of motion and a higher level integration mechanism characterized by cooperative or facilitatory interactions between low-level detectors tuned to the same direction of motion. Our data are consistent with a second-level, direction-specific process that integrates the responses of low-level motion detectors.

Discrimination, Psychological↗
PubMed1997

Dynamic, state-dependent thresholds for the perception of single-element apparent motion: bistability from local cooperativity.

Previous studies have indicated that the formation of coherent patterns for multielement motion displays depends on global cooperative interactions among large ensembles of spatially distributed motion detectors. These interactions enhance certain motion directions and suppress others. It is reported here that perceiving one element moving between two nearby locations likewise is subject to cooperative influences (possibly facilitating and inhibiting interactions within a local ensemble of overlapping detectors). Thresholds depending on luminance contrast were measured for a generalized single-element apparent-motion stimulus, and evidence for spontaneous switching and hysteresis effects indicated that motion perception near the 50% threshold was bistable. That is, for conditions in which motion and nonmotion were perceived half the time, the two percepts were distinct; when one was perceived, it clearly was discriminable from the other. These results indicated that (1) single-element apparent-motion thresholds depended on the immediately preceding state of the ensemble of motion detectors responding to the stimulus, and (2) the stimulus activation of individual motion detectors always might be influenced by recurrent, cooperative interactions resulting from the detectors' being embedded within interconnected ensembles.

Adult↗
PubMed2006

Perception of biological motion from limited-lifetime stimuli.

The visual perception of human movement from sparse point-light walkers is often believed to rely on local motion analysis. We investigated the role of local motion in the perception of human walking, viewed from the side, in different tasks. The motion signal was manipulated by varying point lifetime. We found the task of coherence discrimination, commonly used in biological motion studies, to be inappropriate for testing the role of motion. A task requiring temporal information showed a strong performance drop when fewer points were used or when the image sequence was sampled and displayed at a reduced frame rate. Irrespective of the frame rate, performance did not vary with point lifetime. We concluded that local motion is not required for the perception of tested biological movements, suggesting that the analysis of biological motion does not benefit from examining local motion. The reliance of perception on the number of displayed points and frames supports the idea that biological motion is perceived from a sequence of spatiotemporally sampled forms.

Child↗
PubMed1995

Effects of continuous passive motion following Austin bunionectomy. A prospective review.

Thirty-nine patients suffering from hallux valgus deformity were randomized into one of two treatment groups following a corrective Austin procedure. One group received physical therapy only (n = 18), and the other group received physical therapy and continuous passive motion (n = 21). Continuous passive motion was initiated immediately after surgery and patients were instructed to use continuous passive motion for 8 hr a day for 24 days. On the 7th, 14th, 21st, 28th, 60th, and 90th days, range of motion, return to conventional shoes, use of oral analgesics, and complication rate were measured. The group using continuous passive motion had greater range of motion at each postoperative visit compared with the group who used physical therapy only (P < 0.05). The group who used physical therapy only took longer to return to conventional shoes and to cease oral medication than the group who used continuous passive motion (P < 0.01). The use of continuous passive motion as an adjunct to physical therapy following an Austin procedure expedites the rehabilitation time and increases the rate of return to functional range of motion.

Adult↗
PubMed2000

Specificity of projections from wide-field and local motion-processing regions within the middle temporal visual area of the owl monkey.

The middle temporal visual area (MT) of the owl monkey is anatomically organized with respect to both preferred direction of motion and different types of center-surround interaction. The latter organization consists of clusters of neurons whose receptive fields have antagonistic surrounds that render them unresponsive to wide-field motion (local motion columns) interdigitated with groups of neurons whose receptive fields have additive surrounds and thus respond best to wide-field motion (wide-field motion columns). To learn whether the information in these regions remained segregated further along the visual pathways, we made injections of retrograde tracers into two visual areas to which MT projects [the medial superior temporal area (MST) and fundus of the superior temporal sulcus (FST)] and then labeled the wide-field and local organization using 2-deoxyglucose. In complementary experiments, we injected anterograde tracers into regions of MT that we had mapped using microelectrode recordings. Injections into both dorsal FST and ventral MST labeled clusters of cell bodies in MT that were concentrated within wide-field motion columns, whereas injections into dorsal MST labeled neurons predominantly within local motion columns. Results from the anterograde tracer experiments corroborated these findings. The high degree of specificity in the connections reinforces a model of functional organization for wide-field versus local motion processing within MT. Our data support the previously reported division of FST into separate dorsal and ventral areas, and they also suggest that MST of the owl monkey is, like MST of the macaque, functionally organized with respect to local versus wide-field motion processing.

Animals↗
PubMed2000

Effects of superior colliculus inhibition on visual motion processing in the lateral suprasylvian visual area of the cat.

PURPOSE: To clarify whether visual inputs of the tectothalamocortical pathway influence motion processing within the lateral suprasylvian (LS) area of the cat. METHODS: This study was conducted in five cats. Tungsten microelectrodes were used for recording visual evoked potentials. The electrodes were introduced into the LS area. An array of 120 randomly located dots was projected onto the stimulus field (40 degrees x 40 degrees) in front of the animal by a slide projector. The dots were moved rightward and leftward alternatively with interstimulus intervals by a mirror attached to a galvanometer, the movements of which were controlled by a microcomputer. Each motion sequence consisted of an abrupt onset of motion that continued for 100 msec followed by an abrupt offset and a stationary phase of 900 msec; the total duration of each sequence was thus 1000 msec. The velocity of the motion was varied in 12 steps. The onset of motion was used as the trigger for recording evoked potentials. Single or multiple injections (two to three) of muscimol were made, mainly into the rostral superior colliculus (SC). The amplitudes of evoked potentials before and after the muscimol injection were compared. RESULTS: A large negative wave (N1) with the peak latency of 89.80+/-16.39 msec (mean +/- SD, n = 191) was recorded consistently. The amplitude of N1 was not altered by the muscimol injection into the SC when the velocity of motion was 50 deg/sec or less. When the velocity of motion was 75 deg/sec or more, however, the amplitude of N1 was reduced to 62% to 72% of that noted before the muscimol injection. CONCLUSIONS: These findings suggest that the LS area processes the visual motion inputs reaching through the two parallel pathways, the geniculostriate pathway and the tectothalamocortical pathway, when the velocity of visual motion is 75 deg/sec or more.

Animals↗
PubMed2000

Occlusion and the interpretation of visual motion: perceptual and neuronal effects of context.

Visual motion can be represented in terms of the dynamic visual features in the retinal image or in terms of the moving surfaces in the environment that give rise to these features. For natural images, the two types of representation are necessarily quite different because many moving features are only spuriously related to the motion of surfaces in the visual scene. Such "extrinsic" features arise at occlusion boundaries and may be detected by virtue of the depth-ordering cues that exist at those boundaries. Although a number of studies have provided evidence of the impact of depth ordering on the perception of visual motion, few attempts have been made to identify the neuronal substrate of this interaction. To address this issue, we devised a simple contextual manipulation that decouples surface motion from the motions of visual image features. By altering the depth ordering between a moving pattern and abutting static regions, the perceived direction of motion changes dramatically while image motion remains constant. When stimulated with these displays, many neurons in the primate middle temporal visual area (area MT) represent the implied surface motion rather than the motion of retinal image features. These neurons thus use contextual depth-ordering information to achieve a representation of the visual scene consistent with perceptual experience.

Animals↗