Robotic movement elicits visuomotor priming in children with autism

The ability to understand another person's action and, if needed, to imitate that action, is a core component of human social behaviour. Imitation skills have attracted particular attention in the search for the underlying causes of the social difficulties that characterize autism. In recent years, it has been reported that people with autism can bypass some of their social deficits by interacting with robots. However, the robot preference in terms of imitation has yet to be proved. Here we provide empirical evidence that interaction with robots can trigger imitative behaviour in children with autism. We compared a group of high functioning children with autism with a group of typically developing children in a visuomotor priming experiment. Participants were requested to observe either a human or a robotic arm model performing a reach-to-grasp action towards a spherical object. Subsequently, the observers were asked to perform the same action towards the same object. Two 'control' conditions in which participants performed the movement in the presence of either the static human or robot model were also included. Kinematic analysis was conducted on the reach-to-grasp action performed by the observer. Our results show that children with autism were facilitated - as revealed by a faster movement duration and an anticipated peak velocity - when primed by a robotic but not by a human arm movement. The opposite pattern was found for normal children. The present results show that interaction with robots has an effect on visuomotor priming processes. These findings suggest that in children with autism the neural mechanism underlying the coding of observed actions might be tailored to process socially simpler stimuli.     

Impact of Morbid Obesity on Chewing Ability

Background  This study compared the chewing parameters in a group of obese adult patients scheduled for gastric bypass surgery with those of a control group. Methods  Chewing parameters were measured in two groups of subjects, one of 44 obese patients scheduled for gastric bypass surgery (body mass index [BMI] = 49.1 ± 7.2) and the other of 30 non-obese control subjects (BMI = 20.9 ± 2.1). In both groups, the subjects’ dental status was characterized by the number of functional dental units. Kinematic parameters, namely chewing time (CT), number of chewing cycles (CC), and chewing frequency (CF), were video recorded during the mastication of five natural standardized foods (banana, apple, sweet jelly, peanut, and carrot). The particle size distribution of the expectorated bolus from carrot and peanuts was characterized by the 50th percentile (D ₅₀). Analysis was carried out to detect any effect of the fixed factors “dental status,” “type of food,” and “subject group” on the variations of the dependent factors CT, CC, CF, and D ₅₀. Results  In obese subjects, CT, CC, and D ₅₀ were variables depending on both dental status and food. For fully dentate subjects, the group of patients with obesity showed higher values for CT and CC and lower values for D ₅₀ for both carrot and peanuts than the control group. Conclusion  The chewing parameters were affected in fully dentate patients with morbid obesity compared with controls, emphasizing the need for a systematic evaluation of both dental status and chewing ability in patients scheduled for bariatric surgery.     

In vivo flexion/extension of the normal cervical spine

Twenty-two women (age range 25-49 years, average 30.9 years) and twenty-two men (age range 23-42 years, average 31.6 years), all healthy and asymptomatic, underwent passive flexion/extension examinations of the cervical spine. Functional x-rays were taken and analyzed using a computer-assisted method that quantified intervertebral rotations, translations, and locations of the centers of rotation for each level C1-C2-C6-C7. The aim of the study was to establish values for these parameters for a normal population as related to age and gender. In the process, a statistically significant difference was found in the average value of rotation between male and female groups at the C5-C6 level. A new parameter, the ratio between translation and rotation, was also established and may prove useful for clinical diagnoses. This parameter has a smaller error associated with it than do pure translations and may aid the clinician by helping to account for the large variation in rotatory ranges of motion within the population. This translation/rotation ratio indicated highly significant differences in the lower segments of the cervical spine between gender groups.     

Effect of auditory rhythmic cuing on gait kinematic parameters of stroke patients

The emotional and psychological benefits of musical experiences for human behavior are well documented by research in music therapy and psychology of music. It is also documented that music and rhythm have been utilized universally to accompany motor activity. The effect, however, of music and rhythm on motor activity including mechanics of hemiparetic gait has not been investigated. The purpose of this study was to investigate the effect of auditory rhythmic cuing on gait kinematic parameters of stroke patients. Eight subjects were studied over three trials. For each trial, a baseline walk without rhythm and a walk with rhythm as pacemaker, matched to the step cadence of the baseline walk, was videotaped with two 60 Hz videocameras. Three dimensional coordinates of ten body points were calculated by combining the images of the two cameras utilizing the direct linear transformation (DLT) method. The raw position data was digitally smoothed before being submitted to further analysis. Repeated measures ANOVA and paired t-tests revealed positive modifications in gait patterns due to musical rhythmic cues; specifically: (1) the stride lengths and hip joint range of motion (ROM) of the affected/non-affected sides became more symmetrical; and (2) center of mass (CM) vertical displacement decreased. These results support the presence of an entrainment effect of auditory rhythmic cuing on hemiparetic gait.     

Comparing in vivo kinematics of unicondylar and bi-unicondylar knee replacements

Preserving both cruciate ligaments in unicondylar knee arthroplasty likely provides more normal knee mechanics and contributes to enhanced patient function. It follows that preserving both cruciate ligaments with total knee arthroplasty should provide functional benefit compared to arthroplasty sacrificing one or both cruciates. The purpose of this study was to compare knee kinematics in patients with optimally functioning cruciate-preserving medial unicondylar and bi-unicondylar arthroplasty to determine if knee motions differed. Eight consenting patients with seven medial unicondylar and five bi-unicondylar arthroplasties were studied using lateral fluoroscopy during treadmill gait, stair stepping, and maximum flexion activities. Patient-specific geometric models based on CT and CAD data were used for shape matching to determine the three-dimensional knee kinematics. Tibiofemoral contact locations were computed for the replaced compartments. Maximum flexion in kneeling was 135°±14° for unicondylar knees and 123°±14° for bi-unicondylar knees (p=0.22). For 0°–30° flexion during the stair activity, the medial condyle translated posterior 3.5±2.5 mm in unicondylar knees and 4.7±1.9 mm in bi-unicondylar knees (p>0.05). Lateral posterior translation was 5.0±2.3 mm in bi-unicondylar knees for 0°–30° flexion. From heel-strike to mid-stance phase, there was little tibial rotation, but unicondylar knees showed 1.5±1.6 mm posterior translation of the medial condyle, while bi-unicondylar knees showed 5.1±2.2 mm (p<<0.05). The bi-unicondylar knees showed 3.8±3.4 mm posterior lateral condylar translation. Preserving both cruciate ligaments in knee arthroplasty appears to maintain some basic features of normal knee kinematics. Knees with bi-unicondylar arthroplasty showed kinematics closer to motions observed in total knee arthroplasty, slightly less weight-bearing flexion, and greater dynamic laxity in gait than unicondylar knees. Despite kinematic differences, knees with unicondylar and bi-unicondylar arthroplasty can provide excellent functional outcomes in appropriately selected patients.     

Physiological costs and temporo-spatial parameters of walking on a treadmill vary with body weight unloading and speed in both healthy young and older women

Walking on a treadmill with Body Weight Unloading (BWU), which has been successfully used on patients with neurological conditions, may also be used as a training tool to increase walking speed in healthy individuals. We hypothesised that BWU enables individuals to walk at a faster speed on a treadmill than they would do in normal gravity conditions without increasing their effort and with an increase in both stride length (SL) and stride frequency (SF). Oxygen uptake, heart rate (HR), SL and SF of six older women (mean ± SD; 70 ± 4 years) and six young women (26 ± 3 years) were measured during treadmill walking at three self-selected speeds (comfortable, slow and fast) and three different percentages of BWU (0, 20 and 40%). No significant differences were found between the groups in any self-selected walking speeds and any of the other variables. The combined data of the two groups showed that walking energy cost per unit of time (WECt) and HR at fast speed with 40% of BWU (258 ± 60 J kg⁻¹ min⁻¹ and 95 ± 15 beats min⁻¹, respectively) were similar to those measured at comfortable speed with no BWU (273 ± 47 J kg⁻¹ min⁻¹ and 101 ± 16 beats min⁻¹, respectively). Also SL and SF increased significantly with speed (P < 0.017) at any given percentage of BWU. The results suggest that 40% of BWU enables both young and older women to walk at a faster speed on a treadmill without increasing their effort and with an increase in both SL and SF.     

Comparison between successful and failed sit-to-stand trials of a patient after traumatic brain injury

OBJECTIVE: To compare the peak whole-body center of mass (COM) velocities and joint angular contributions in successful and unsuccessful sit-to-stand (STS) trials in a subject with traumatic brain injury (TBI). DESIGN: Single-case study. SETTING: Motion research laboratory. PARTICIPANT: A 24-year-old man who was 3.5 years post-TBI. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak horizontal and vertical velocities of the whole-body COM and peak angular velocities of the ankle, knee, hip, and shoulder joints. RESULTS: The peak whole-body COM vertical velocity was significantly lower in the unsuccessful STS trials. Angular velocities at the hip, knee, ankle, and shoulder joints in successful trials exceeded those in unsuccessful trials (P<.001). The subject's peak knee extension velocity was the single major predictor of the peak whole-body COM vertical velocity (r(2)=.90). Knee extension angular velocities greater than 3.25 radian/s were associated with successful STS trials. Knee extension angular velocities between 2.75 and 3.25 radian/s were associated with successful rising 50% of the time; the subject had no success in rising when velocities were less than 2.75 radian/s. CONCLUSIONS: For this subject, sit-back failures occurred in STS attempts characterized by peak whole-body COM vertical velocities that were lower than those generated in successful rising trials. These unsuccessful rising attempts were primarily the result of the subject's inability to generate sufficient knee extension angular velocity.     

脑卒中偏瘫患者未受累侧上肢够物动作的生物力学研究

目的 分析脑卒中偏瘫患者未受累侧（健侧）上肢在够物动作中的生物力学特性。 方法 选取脑卒中偏瘫患者30例设为患者组,另选取健康受试者23例作为对照组。2组受试者均接受上肢够物测试,够物过程分为肩前屈和保持两个阶段。采用表面肌电技术和穿戴式微型运动捕获系统同步采集并提取上肢够物时相关肌肉的表面肌电参数（均方根值、积分肌电值）和三维运动学数据（躯干扭转度、肩关节运动幅度、肩关节运动速度、等张失稳度、肩关节角度分散度）,患者组依据未受累上肢是否为利手侧,将其分为利手侧和非利手侧进行分别采集,对照组利手和非利手侧均进行采集,然后采用秩和检验对相关数据进行统计学分析。 结果 患者利手侧在前屈阶段斜方肌上部均方根值为34.3μV,躯干扭转度为-1.4°,均高于对照组利手侧的19.7μV和-2.3°,组间差异均有统计学意义（P<0.05）,而肩关节运动速度则低于对照组利手侧,差异有统计学意义（P<0.05）;在保持阶段斜方肌上部,患者利手侧均方根值为55.4μV,高于对照组利手侧,胸大肌均方根值和三角肌前组/斜方肌上部积分肌电值均低于对照组利手侧,差异均有统计学意义（P<0.05）。患者非利手侧在前屈阶段三角肌中组均方根值高于对照组非利手侧,肩关节运动速度低于对照组非利手侧的,组间差异均有统计学意义（P<0.05）。对照组双侧比较,在前屈阶段,非利手侧斜方肌上部均方根值大于利手侧,三角肌前组/斜方肌上部积分肌电值比在前屈和保持阶段均小于利手侧,组内差异均有统计学意义（P<0.05）。 结论 无论脑卒中偏瘫患者的未受累上肢是利手侧还是非利手侧,其够物动作的生物力学特点与健康人对应侧上肢并非完全一致,在对脑卒中偏瘫患侧上肢进行生物力学研究时最好以健康人对应侧上肢作为对照。     

Awareness of muscular force during movement production: an fMRI study

Awareness of the muscular forces we produce during voluntary movement must be distinguished from awareness of motor outcome itself. Indeed, there is no univocal relationship between produced muscle force and movement outcome because of external forces. In the present study, we performed a functional magnetic resonance imaging study to investigate the neural bases underlying the awareness we can have of the muscular forces we put into our voluntary movements. In reference conditions, subjects made rhythmical hand movements and knew they had to reproduce, in a subsequent condition in which the resistance to the movement was increased, either their muscular forces or their kinematics. The idea behind this (well established) reproduction paradigm is that, after an explicit verbal instruction, subjects can only reproduce what they are aware off. The main contrast, that is, between the condition during which the subjects had to gain awareness of their muscular forces and that during which they had to gain awareness of their kinematics (conditions in which the actual motor output was similar), shows that gaining awareness about muscular forces exerted during movement execution makes much higher demands on many brain structures, in particular posterior insula, primary sensorimotor areas and associative somatosensory areas. This indicates the important role of somesthetic information processing in awareness of produced muscular force. Therefore, the often-heard presumption that muscle force sense might be based on the outgoing motor command is not confirmed by the present results.     

Knee joint moments during high flexion movements: Timing of peak moments and the effect of safety footwear

Aim

(1) Characterize knee joint moments and peak knee flexion moment timing during kneeling transitions, with the intent of identifying high-risk postures. (2) Determine whether safety footwear worn by kneeling workers (construction workers, tile setters, masons, roofers) alters high flexion kneeling mechanics.