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PubMed1992

Influence of temporal cues on acoustic motion-direction sensitivity of auditory neurons in the owl.

1. We studied the sensitivity of auditory neurons in the barn owl's brain stem to the direction of apparent acoustic motion. Motion stimuli were generated with an array of seven free-field speakers (Fig. 2). Motion-direction sensitivity was determined by comparing the number of spikes evoked by counterclockwise (CCW) motion with the number of spikes evoked by clockwise (CW) motion. A directionality index (DI) was defined to quantify the measurements. The statistical significance of the directional bias was determined by a chi 2 test that used the responses to stationary sounds as the null hypothesis. 2. During the search for acoustic neurons, dichotic stimuli were presented via earphones, and the sensitivity of the units for interaural time difference (ITD), interaural level difference (ILD), and frequency was measured. After a unit had been isolated, its response to moving and stationary free-field stimuli was recorded. Most of the neurons that responded to dichotic stimulation responded also to free-field stimulation. At 61 of the 211 recording sites, the response was motion-direction sensitive. 3. The spontaneous activity of all neurons was low, so that some 95% of the recorded activity was due to an excitation caused by the stimuli. 4. Neurons sensitive to the direction of motion were found in many nuclei of the auditory pathway such as the nuclei of the lateral lemniscus, the subnuclei of the inferior colliculus (IC), and the optic tectum (OT) (Figs. 3 and 5-8, Table 1). 5. In 61% of the motion-direction-sensitive neurons, the response to motion in the preferred direction was equal to the response to stationary sounds, whereas in 75% of the neurons, the response to motion in the null direction was lower than the response to stationary sounds (Table 2, Fig. 6). This observation suggested a null-direction inhibition as one important factor of generating motion-direction sensitivity. 6. Neurons having a high motion-direction sensitivity usually responded phasically, whereas tonically active neurons exhibited a low motion-direction sensitivity (Fig. 9). 7. Velocity tuning was broad (Fig. 7). A shallow peak appeared around 310 degrees/s within the range tested (125-1,200 degrees/s, 33 cells). 8. A silent gap between the bursts from successive speakers caused a decrease in motion-direction sensitivity. This decrease was linear with gap duration and depended on the apparent velocity (Figs. 10-13).(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗

PubMed1998

Response to motion in extrastriate area MSTl: center-surround interactions.

The medial superior temporal area of the macaque monkey extrastriate visual cortex can be divided into a dorsal medial (MSTd) and a lateral ventral (MSTl) region. The functions of the two regions may not be identical: MSTd may process optic flow information that results from the movement of the observer, whereas MSTl may be related more closely to processing visual motion related specifically to the motion of objects. If MSTl were related to such object motion, one would expect to see mechanisms for the segregation of objects from their surround. We investigated one of these mechanisms in MSTl neurons: the effect of stimuli falling in the region surrounding the receptive field center on the response to stimuli falling in the field center. We found the effects of the surround stimulation to be modulatory with little response to the surround stimulus itself but a clear effect on the response to the stimulus falling on the receptive field center. The response to motion in the center in the direction preferred for the neuron usually increased when the surround motion was in the opposite direction to that in the center and decreased when surround motion was in the same direction as that in the center. Fifty-seven percent of the neurons showed a ratio of response for center motion with a surround moving in the opposite direction to that in the center for center motion alone that was >1. The response to motion in the center also increased when the surround stimulus was stationary, and this increase was sometimes larger than that with a moving surround. Nearly 70% of the neurons showed a ratio of response to center motion with a stationary surround to center motion alone that was >1. This is in contrast to the minimal effect of stationary surrounds in middle temporal area neurons. When the stimulus presentation was reversed so that the stimulus in the center was stationary and the surround moved, some MSTl neurons responded when the direction of motion in the surround was in the direction opposite to the preferred direction of motion in the center of the receptive field. Stimulation of the surround thus had a profound effect on the response of MSTl neurons, and this pronounced effect of the surround is consistent with a role in the segmentation of objects using motion.

Animals↗

PubMed2005

A computational analysis of separating motion signals in transparent random dot kinematograms.

When multiple motion directions are presented simultaneously within the same region of the visual field human observers see motion transparency. This perceptual phenomenon requires from the visual system to separate different motion signal distributions, which are characterised by distinct means that correspond to the different dot directions and variances that are determined by the signal and processing noise. Averaging of local motion signals can be employed to reduce noise components, but such pooling could at the same time lead to the averaging of different directional signal components, arising from spatially adjacent dots moving in different directions, which would reduce the visibility of transparent directions. To study the theoretical limitations of encoding transparent motion by a biologically plausible motion detector network, the distributions of motion directions signalled by a motion detector model (2DMD) were analysed here for Random Dot Kinematograms (RDKs). In sparse dot RDKs with two randomly interleaved motion directions, the angular separation that still allows us to separate two directions is limited by the internal noise in the system. Under the present conditions direction differences down to 30 deg could be separated. Correspondingly, in a transparent motion stimulus containing multiple motion directions, more than eight directions could be separated. When this computational analysis is compared to some published psychophysical data, it appears that the experimental results do not reach the predicted limits. Whereas the computer simulations demonstrate that even an unsophisticated motion detector network would be appropriate to represent a considerable number of motion directions simultaneously within the same region, human observers usually are restricted to seeing not more than two or three directions under comparable conditions. This raises the question why human observers do not make full use of information that could be easily extracted from the representation of motion signals at the early stages of the visual system.

Computer Simulation↗

PubMed2004

Early versus delayed repair of infantile strabismus in macaque monkeys: II. Effects on motion visually evoked responses.

PURPOSE: Infantile strabismus in humans and the monkey is associated with maldevelopment of visual motion responsiveness, one manifestation of which is directionally asymmetric motion visual evoked potentials (motion VEPs). Early repair of strabismus in infant monkeys has been shown to restore normal development of motion responsiveness for pursuit and optokinetic eye movements (optokinetic nystagmus [OKN]). The purpose of this study was to determine how early versus delayed repair of strabismus influences the development or maldevelopment of motion VEPs. METHODS: Optical strabismus was created in infant macaques by fitting them with prism goggles on day 1 of life. The Early Repair group wore the goggles for a period of 3 weeks (the equivalent of 3 months before surgical repair in humans), whereas the Delayed Repair group wore the goggles for a period of 3 to 6 months (the equivalent of 12-24 months before surgical repair in humans). Several months after the removal of the goggles, motion VEPs to horizontally oscillating grating stimuli were recorded during monocular viewing. An asymmetry index (AI) was measured for each animal by extracting an asymmetric (F1) and symmetric (F2) frequency component from the motion VEP. The AIs of the infant monkeys with Early versus Delayed Repair were also compared with that of a group of adult monkeys, who had unrepaired, natural strabismus. RESULTS: When tested with a 1-cyc/deg, 6-Hz stimulus, both control and Early Repair monkeys exhibited symmetric motion VEPs (AI < 0.25). Mean AI was 0.15 +/- 0.09 in control and 0.16 +/- 0.13 in Early Repair monkeys. In contrast, both Delayed Repair and naturally strabismic monkeys had asymmetric motion VEP responses: AI = 0.57 +/- 0.22 in the Delayed Repair and 0.49 +/- 0.17 in the naturally strabismic monkeys (P < 0.01). Delayed Repair and naturally strabismic monkeys also had motion VEP asymmetries of equivalent magnitude when tested using stimuli at higher (3 cyc/deg/11 Hz) spatial-temporal frequencies. The concordance between motion VEP symmetry and normal fusional vergence was significant (P < 0.01). CONCLUSIONS: Early repair of optical strabismus in primates restores normal development of visual motion pathways in the cerebral cortex, measured as symmetric motion VEPs. Delayed repair causes permanent motion VEP maldevelopment. These results provide additional evidence that early strabismus repair is beneficial for brain development in infant primates.

Animals↗

PubMed1990

Value of continuous passive motion in total knee arthroplasty.

Two methods of rehabilitation after 91 total knee arthroplasties in 74 patients were reviewed. Patients in each group were well matched for age, sex, and diagnosis. Forty-four knees in 39 patients were treated with conventional physiotherapy, consisting of 3 days of immobilization followed by a program of active assisted range-of-motion exercises. Forty-seven knees in 41 patients were placed in a continuous passive motion machine immediately after operation. Other aspects of preoperative, intraoperative, and postoperative care were identical in both groups. Patients in the continuous passive motion group were found to have a lower incidence of complications, especially of wound healing problems and thromboembolic disease. Analgesic use in patients in the continuous passive motion group was reduced. Straight leg raising was achieved slightly earlier in patients in the continuous passive motion group (4.9 days) compared with patients not treated with continuous passive motion (5.2 days). Although the range of motion of the knee at discharge from the hospital in patients in the continuous passive motion group was greater (91 degrees) compared with patients not treated with continuous passive motion (81 degrees), the range of motion in both groups at ultimate follow up was equivalent. However, when knee-rating scores were considered, patients treated with continuous passive motion averaged 9 points higher on a 100-point scale than patients not treated with continuous passive motion. In addition, the length of hospital stay for patients in the continuous passive motion group was 2.1 days shorter. We concluded that continuous passive motion was an effective adjunct to physiotherapy in the postoperative care of patients undergoing total knee arthroplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1992

[Clinical study on the mechanism of motion sickness--clinical examination based on trigger factors].

This report deals with factors which trigger motion sickness. The author has focused on the clinical examinations applied to motion sickness cases. Relationships between clinical data and susceptibility to motion sickness were investigated. The following results were obtained: 1. CV R-R(coefficient of variation of R-R intervals on EGG)in the frequent motion sickness group showed higher values than in the occasional motion sickness group. This result suggests a hyperfunction of the vagus nerve. 2. In caloric testing with ENG, the motion sickness group showed lower values of duration and eye speed than the occasional motion sickness group. On the other hand, the frequent group showed higher values of laterality in eye speed than the occasional group. 3. With the visual suppression test, the frequent motion sickness group showed higher values than the occasional motion sickness group. On the other hand, there was a significant difference between the frequent motion sickness group and the occasional motion sickness group in terms of laterality of visual suppression values. 4. In testing fluctuation of CV R-R in response to optokinetic stimuli, the frequent motion sickness group showed elevation of CV R-R values after optokinetic load. On the other hand, the occasional motion sickness group showed depression of CV R-R values after the same load. 5. Among clinical examinations designed to diagnose susceptibility to motion sickness, CV R-R, the caloric test, the visual suppression test and OKP testing can produce sufficiently accurate results for clinical investigation.

Electrocardiography↗

PubMed2003

Effect of roll oscillation frequency on motion sickness.

BACKGROUND: In many environments associated with motion sickness there are low frequency motions in several axes, including roll. Roll motion has often been assumed to be a cause of motion sickness, either alone or in combination with motions in other axes. However, there have been no systematic studies of the effects of roll frequency on sickness. HYPOTHESIS: It was hypothesized that sickness caused by roll oscillation would depend on the frequency of roll. METHOD: There were 100 male subjects (aged 18 to 26 yr) who participated in a laboratory study. Prior to experiencing motion, all subjects completed a motion sickness history questionnaire giving information on travel and motion sickness experience. The seated subjects were exposed within a closed cabin to 30 min of sinusoidal roll motion at one of five frequencies: 0.025 Hz, 0.05 Hz, 0.10 Hz, 0.20 Hz, or 0.40 Hz. At each frequency, the cabin oscillated through +/-8 degrees about a center of rotation located on the seat surface. Ratings of motion sickness were obtained at 1-min intervals. RESULTS: Subject illness ratings were positively correlated with their previous motion sickness, although at each frequency the amount of sickness was small. Overall, there was no significant difference in the sickness ratings produced by the five motions. CONCLUSIONS: The frequency dependence of motion sickness produced by roll oscillation differs from that associated with vertical and horizontal oscillation. Motion sickness associated with pure roll oscillation of a seat will usually be less than the sickness associated with pure translational oscillation of the seat or the sickness associated with combined translation and rotation.

Adolescent↗

PubMed2005

Desensitization to strong vestibular stimuli improves tolerance to simulated aircraft motion.

INTRODUCTION: The extent to which tolerance acquired in one motion environment can be transferred to another has not been fully elucidated. This study compares three provocative motion stimuli and whether tolerance acquired from cross-coupled motion and torso rotation can be transferred to simulated aircraft motion. METHOD: There were 18 healthy subjects (9 men and 9 women), 18-44 yr of age, who were divided into 3 groups. Each group was exposed to the following desensitization procedure in a pseudo-random repeated measures design. In condition D1, subjects were exposed to 4 consecutive days of cross-coupling and on the 5th d they were exposed to simulated aircraft motion. In D2, subjects were exposed to 4 consecutive days of torso rotation and on the 5th day they were exposed to the simulated aircraft motion as in D1. In D3, subjects were exposed to 5 consecutive days of simulated aircraft motion. Based on Graybiel's diagnostic criteria, severity of motion sickness on the 1st and 5th day in D1, D2, and D3 were compared. RESULTS: Cross-coupled motion was the most provocative stimulus followed by torso rotation and simulated aircraft motion. Within each motion stimulus, there was evidence of desensitization (p < 0.001) within 4 d. There were no significant differences in the severity of motion sickness observed on the 5th day regardless of the desensitization stimuli. CONCLUSION: Our results suggest that desensitization to one provocative motion could be transferred to a less severe motion stimulus. This result could be used in the refinement of desensitization programs for aircrew.

Adaptation, Physiological↗

PubMed1986

Necessary conditions for the perception of motion in depth.

This study investigated the relation between the perception of motion in depth and ocular vergence movements for a single foveally viewed dot, and for a 30 deg X 30 deg pattern of many dots. When the target's disparity was changed, it appeared to move in depth relative to stationary reference marks, but removing the reference marks completely abolished the sensation of motion in depth for the multi-dot target and left only a weak sensation of motion in depth for the single dot target. However, it is not the case that motion-in-depth sensation per se depends on the presence of reference marks; motion in depth generated by changing-size stimulation was unaffected by removing reference marks. Possible explanations for the loss of motion-in-depth sensation include ocular vergence exactly tracked stimulus motion; vergence changes and disparity changes, though unequal, produced equal and opposite motion-in-depth signals; vergence changes, though producing no motion-in-depth signals, suppressed the signals produced by disparity changes; motion-in-depth sensation requires relative motion. Explanation is rejected because vergence tracking errors were large. Explanation is rejected because vergence changes do not in themselves induce a sensation of motion in depth. Explanation is rejected because motion-in-depth threshold is not affected by vergence changes. Conclusions are as follows. For a single-dot target, visual sensitivity to motion in depth is much higher for changes in relative retinal disparity than for changes in absolute retinal disparity, while for a multi-dot target any residual sensitivity is abolished by an interaction between neighboring coherently moving dots. The authors suggest that the relative velocity elements proposed to explain sensitivity to changing size feed the stereomotion mechanism also.

Depth Perception↗

PubMed2005

Lumbar spine intersegmental motion analysis during lifting.

UNLABELLED: There are a lot of in vitro and also in vivo studies under strictly restricted and subject-demanding laboratory conditions using X-ray or MRI recordings, but very few studies give information about the lumbar spine intersegmental behavior in daily life activities. Aims of this study were to measure the intersegmental lumbar spine motions during lifting trials and to determine the different motion patterns of different subjects performing comparable lifting tasks. First, 11 healthy volunteers had to perform lifting tasks (box weight 4-15 kg) using their favorite lifting technique (no instructions by the researcher). The coordinates of skin-markers attached on lumbar spines of the subjects were measured using 3D-motion capturing and then transformed to Cardan-angles. Second, 23 volunteers performed lifting tasks (box weight 4-15 kg) with the instruction to bend their knees during lifting. Coordinates of this smaller set of markers on lumbar spines of the subjects were transformed to intersegmental angles using a spline-method. From the first experiment three groups of motion patterns are distinguishable: subjects who used only small intersegmental range of motion within their upper lumbar spine and bended their knees during lifting were in contrast to subjects who used 3.25 times wider range of motion in the upper lumbar spine and did not bend the knees (cluster analysis, c = 0.76). The third group was not assignable to these other two groups. Within all lifting trials of the second experiment different groups were detectable also: in spite of all subjects bended their knees, there were subjects with wide range of motion of lumbar spine motion segments. Other subjects were able to reduce intersegmental range of motion (k-means clustering, msv > 0.47). From this it follows that the intersegmental motion of lumbar spine is individually different and not equal for all lumbar levels. Furthermore, lifting technique influenced the motion of the lumbar spine. But not for all subjects, the advice to bend the knees during the lifting effectively reduced the lumbar motion ranges. IN CONCLUSION: special instructions to reduce lumbar spinal motion are recommended. Due to different lumbar spine motion patterns, different loading situations are anticipated because of changing lever arms and angular accelerations. This understanding is important in reducing spinal loading and to prevent spinal disorders in manual material handling tasks.

Journal Article↗

PubMed2005

Real-time intra-fraction-motion tracking using the treatment couch: a feasibility study.

Significant differences between planned and delivered treatments may occur due to respiration-induced tumour motion, leading to underdosing of parts of the tumour and overdosing of parts of the surrounding critical structures. Existing methods proposed to counter tumour motion include breath-holds, gating and MLC-based tracking. Breath-holds and gating techniques increase treatment time considerably, whereas MLC-based tracking is limited to two dimensions. We present an alternative solution in which a robotic couch moves in real time in response to organ motion. To demonstrate proof-of-principle, we constructed a miniature adaptive couch model consisting of two movable platforms that simulate tumour motion and couch motion, respectively. These platforms were connected via an electronic feedback loop so that the bottom platform responded to the motion of the top platform. We tested our model with a seven-field step-and-shoot delivery case in which we performed three film-based experiments: (1) static geometry, (2) phantom-only motion and (3) phantom motion with simulated couch motion. Our measurements demonstrate that the miniature couch was able to compensate for phantom motion to the extent that the dose distributions were practically indistinguishable from those in static geometry. Motivated by this initial success, we investigated a real-time couch compensation system consisting of a stereoscopic infra-red camera system interfaced to a robotic couch known as the Hexapod, which responds in real time to any change in position detected by the cameras. Optical reflectors placed on a solid water phantom were used as surrogates for motion. We tested the effectiveness of couch-based motion compensation for fixed fields and a dynamic arc delivery cases. Due to hardware limitations, we performed film-based experiments (1), (2) and (3), with the robotic couch at a phantom motion period and dose rate of 16 s and 100 MU min(-1), respectively. Analysis of film measurements showed near-equivalent dose distributions (<or=2 mm agreement of corresponding isodose lines) for static geometry and motion-synchronized real-time robotic couch tracking-based radiation delivery.

Computer Systems↗

PubMed1999

Dynamic motion analysis of normal and unstable cervical spines using cineradiography. An in vivo study.

STUDY DESIGN: Cervical motion patterns were analyzed in a normal population and in patients with cervical instability by using cineradiography. OBJECTIVES: To determine normal and pathologic motion patterns in the cervical spine through an in vivo continuous motion analysis. SUMMARY OF BACKGROUND DATA: Cineradiographic techniques have been used in a limited number of studies to quantify spinal motion. There is a paucity of information regarding dynamic motion patterns in normal and pathologic cervical spines. METHODS: Ten healthy subjects and 12 patients with unstable cervical spines (C1-C2 subluxation caused by rheumatoid arthritis, n = 10; instability below C2, n = 2) were studied. Cervical motion during flexion from the maximum extension position was recorded using cineradiography. Cervical segmental motions (C1-C2 to C5-C6) were continuously measured through quantifying cineradiographic images projected on a digitizer. RESULTS: Normal cervical spines showed a well-regulated stepwise motion pattern that initiated at C1-C2 and transmitted to the lower segments with time lags. Pathologic spines showed a different order of onset of segmental motion. In patients with rheumatoid arthritis who had atlantoaxial subluxation, C1-C2 motion initiated significantly earlier than C2-C3 motion. In patients with segmental instability below C2, motion in the unstable segments preceded that in the upper intact segments. CONCLUSIONS: Different motion patterns were observed between normal and pathologic cervical spines. Cineradiographic motion analysis is a valuable adjunctive technique, especially in diagnosis or evaluation of conditions that cannot be identified through conventional radiographic examination.

Adult↗

PubMed2002

The effects of motion artifact and low perfusion on the performance of a new generation of pulse oximeters in volunteers undergoing hypoxemia.

INTRODUCTION: Motion artifact and low perfusion often lead to faulty or absent pulse oximetry readings in clinical practice. OBJECTIVE: Determine the impact of motion artifact and low perfusion on newly introduced pulse oximetry technologies during hypoxemic episodes in healthy volunteers. METHODS: Five different pulse oximeters from 4 manufacturers (the Datex Ohmeda 3900P; the Agilent; the Nellcor N-3000; the Nellcor N-395; and the Schiller OX-1, which is the European version of the Ivy SatGuard 2000 with Masimo SET) were compared with respect to their ability (separated or in combination) to provide accurate readings in the presence of motion artifact and low perfusion. Four of these oximeters represent the latest available oximetry technology, and one (the N-3000) represents a previous generation of oximeters. Oxygen saturation values (S(pO(2))) and pulse rate from the oximeters were recorded during episodes of induced hypoxemia in 10 healthy volunteers. Standardized and repeatable motion artifacts were generated by a motion machine and by having the test subject perform tapping and scratching motions. Perfusion to the finger was reduced by an inflatable balloon impinging on the brachial artery. The pulse oximetry readings from the test oximeters were compared to readings from control pulse oximeters on the unperturbed reference hand. The pulse rates from the test oximeters were compared to the electrocardiographically-measured heart rate. RESULTS: The frequency of faulty readings was increased by increasing motion interference and decreasing perfusion. The S(pO(2)) deviation was within +/- 3% of the reference reading > 95% of the time for all instruments during the control desaturation period in the absence of motion and with normal perfusion. With the combination of motion and low perfusion, the S(pO(2)) error was within +/- 3% less than 62% of the time for all oximeters tested. A significant difference in the frequency of large S(pO(2)) errors was observed only in the direct comparison of the N-395 and N-3000. The N-395 exhibited less frequent S(pO(2)) error exceeding 6% of S(pO(2)) in the combination of the most challenging situations (motion and motion with reduced perfusion). In the same situation the Datex-Ohmeda 3900P and Nellcor N-3000 showed significantly higher pulse rate errors than the other devices (Datex-Ohmeda 3900P 53% of the time and N-3000 37% of the time). CONCLUSIONS: The established model of creating motion artifact and low perfusion is capable of simulating a hierarchy of severe clinical situations. With solely motion or solely reduced perfusion the percentage of errors exceeding +/- 3% of S(pO(2)) increased by 20% and 10%, respectively, compared to the control period. Simultaneous presence of motion and reduced perfusion leads to a relative incidence of > 35% of errors > 3% of S(pO(2)) for the various oximeters. In this situation the N-3000 and the Datex-Ohmeda 3900P exhibited differences between estimated pulse rate and electrocardiographically-measured heart rate > 25 beats/min > 37% of the time.

Adult↗

PubMed1998

The humeroscapular motion interface.

Motion between the humerus and scapula commonly is described as glenohumeral motion. However, humeroscapular motion occurs at two distinct sites. In addition to the motion at the diarthrodial glenohumeral joint, movement occurs between the proximal humerus and related structures and the surrounding sleeve of structures, including the acromion, deltoid, coracoid, coracoacromial ligament, and the muscles attached to the coracoid. This site of nonarticular shoulder motion is defined as the humeroscapular motion interface. Nonarticular humeroscapular motion can be documented and measured using standard magnetic resonance imaging techniques. The maximum average interfacial motion using axial images was 29.1 mm, which occurred at the level of the maximum diameter of the humeral head. Interfacial motion varied depending on the site measured. If pathologic conditions such as adhesions secondary to trauma or surgery interfere with or obliterate this space at sites of significant sliding motion, overall shoulder motion will be limited. Successful treatment of shoulder stiffness related to humeroscapular restraints is likely to require restoration of the normal sliding motion at the humeroscapular motion interface, in addition to resolving restraints affecting the glenohumeral joint motion.

Adult↗

PubMed1996

Intercepting real and path-guided apparent motion targets.

Human subjects were instructed to intercept with a cursor real and apparent motion targets presented on a computer screen. Targets traveled counterclockwise (CCW) in a circle at one of five angular velocities (180, 300, 420, 480 and 540 deg/s), either smoothly (real motion) or in path-guided apparent motion. Subjects operated a computer mouse and were instructed to intercept targets at the 12 o'clock position; there were no constraints on when to initiate the response, which was a movement from the center of the screen towards and past 12 o'clock. We found the following: (a) for both motion conditions and all target velocities, subjects were late in intercepting the target, especially at higher target velocities; (b) for both motion conditions, the directional variability of the response increased as a linear function of the target velocity; (c) the directional variability of the response was systematically higher for the apparent than the real motion condition; there was no significant interaction between target velocity and target motion type; (d) the response time did not vary significantly with velocity, but was consistently longer for apparent than real motion targets; (e) the movement time was very similar for different target velocities; and (f) the moment of initiation of the interception movement was delayed appreciably at higher target velocities, relative to that dictated for perfect interception at a given target velocity. This delay was greater for the apparent motion target. These results demonstrated the following: (a) for both target motion conditions, interception was not fully predictive but lagged the target in spite of the constant target velocity and the unconstrained time allowed for initiating the interception movement; (b) subjects can intercept an apparent motion target but, compared with real motion, the performance is somewhat degraded overall; (c) the similarities in performance between the two target motion conditions, and the fact that target velocity influenced performance in a similar fashion, suggest that the motor system can access the visual information provided by the moving target; and (d) since movement time was similar for different target velocities, the strategy for interception relied on controlling the moment of initiation of the interception movement. This was successful for low target velocities but became unsuccessful at higher target velocities.

Adult↗

PubMed2000

The role of continuous passive motion after total knee arthroplasty.

The usefulness of continuous passive motion after total knee arthroplasty remains controversial. The reported benefits include decreased rates of knee manipulation, deep vein thrombosis, and postoperative use of analgesics, and a greater range of motion. Other studies have reported increased wound complications, bleeding, and pain. Lack of consensus on the use of continuous passive motion exists because reported studies include many confounding variables. Several studies have shown that continuous passive motion in the hospital decreased the rate of knee manipulation from as high as 21% to as low as 0%. Although many studies show that range of motion may improve more rapidly with continuous passive motion, the ultimate range of motion at followup is unchanged. At the author's institution, continuous passive motion is used three times per day (1 hour sessions), beginning on the first postoperative day, within a 4 to 5 day inpatient hospital pathway. Of 132 knees that had a primary posterior-stabilized total knee arthroplasty, seven knees (5%) had a manipulation for failure to obtain greater than 70 degrees flexion. No patients had major wound complications that required reoperation. There is no specific charge to the patient for the continuous passive motion because it is included in the hospital per diem charge. The literature and the author's data support the use of continuous passive motion to decrease the rate of manipulation (and its costs) for poor range of motion after total knee arthroplasty. If patients follow fixed inpatient hospital pathways, the length (and possibly cost) of hospital stay is not changed by use of continuous passive motion. The data on the effect of continuous passive motion on overall analgesic use and prevalence of deep vein thrombosis are not clear.

Arthroplasty, Replacement, Knee↗

PubMed2005

Motion class dependency in observers' motor areas revealed by functional magnetic resonance imaging.

Human and animal data suggest that the mere observation of biological motion activates those premotor areas that also underlie the initiation of the same motion. However, data also indicate that the human premotor cortex (PM), in contrast to the monkey PM, responds not only to the observation of goal-directed (transitive) motion but also to intransitive motion. The present study used functional magnetic resonance imaging to test this hypothesis directly. Participants were presented cycles of intransitive motion specified as belonging to the distal (fingers and mouth), proximal (knee, ankle, elbow, and wrist), or axial (trunk and shoulder) motion class. Attention to motion was behaviorally tested by a forced-choice task on motion acceleration and deceleration. Results revealed extended PM activation for each motion condition. However, direct contrasts showed that the most significant activations were elicited in ventrolateral PM by distal motion, in dorsolateral PM by proximal motion, and medial PM (supplementary motor area) by axial motion. Findings confirm observed intransitive motions to engage premotor areas along a gross-scaled somatotopy.

Adult↗

PubMed1998

Continuous passive motion after repair of the rotator cuff. A prospective outcome study.

Despite the apparent success of continuous passive motion after soft-tissue procedures or joint replacements, its effect after repair of the rotator cuff is still unknown. The purpose of this prospective, randomized outcome study was to compare the results of continuous passive motion with those of manual passive range-of-motion exercises after repair of the rotator cuff. Thirty-one patients (thirty-two rotator cuffs) were randomly assigned to one of two types of postoperative management: continuous passive motion (seventeen patients) or manual passive range-of-motion exercises (fifteen patients). There were seventeen women and fourteen men, and the mean age was sixty-three years (range, thirty to eighty years). The patients were followed for a mean of twenty-two months (range, six to forty-five months). Five tears of the rotator cuff were small, eighteen were medium, and nine were large. All of the operations were performed by one surgeon. The patients who were managed with continuous passive motion used the device for the first four weeks postoperatively. The patients who were managed with manual passive range-of-motion exercises were assisted by a trained relative, friend, or home-care nurse. After the four-week period, the two groups were managed similarly for two to five months. According to the Shoulder Pain and Disability Index, a valid and reliable self-administered questionnaire, the treatment was extremely successful in both groups. The overall score was excellent for twenty-seven shoulders (84 per cent), good for two (6 per cent), fair for two (7 per cent), and poor for one (3 per cent). With the numbers available, we could detect no significant differences (p > 0.05) between the two groups with respect to the score according to the Index, pain (according to a visual-analog scale), range of motion, or isometric strength. Manual passive range-of-motion exercises were more cost-effective than continuous passive motion. The limited number of physical-therapy visits associated with the manual passive range-of-motion exercises in the present study appeared to be more cost-effective than a traditional physical-therapy schedule of three visits per week. Postoperative therapy with continuous passive motion or manual passive range-of-motion exercises appears to yield favorable results after repair of a small, medium, or large tear of the rotator cuff.

Adult↗