Control of single-joint movements in deafferented patients: evidence for amplitude coding rather than position control

Two deafferented patients and several control subjects participated in a series of experiments to investigate how accurate single-joint movements are programed, spatially calibrated, and updated in the absence of proprioceptive information. The deafferented patients suffered from a permanent and severe loss of large sensory myelinated fibers below the neck. Subjects performed, with and without vision, sequences of forearm supinations and pronations with two temporal delays between each movement (0 s and 8 s). Overall, the lack of proprioception did not yield any significant decrease in movement accuracy when vision was available. Without vision, the absence of proprioceptive afferents yielded (1) significantly larger spatial errors, (2) amplitude errors similar to those of control subjects, and (3) a significant drift when an 8-s delay was introduced between two successive movements. Subjects also performed, without vision, a 20 supination followed by a 20 pronation that brought back the wrist to the starting position. On some trials, the supination was blocked unexpectedly by way of a magnetic brake. When the supination was blocked, subjects were already on the second target and no pronation was required when the brake was released. The defferented patients, unaware of the procedure, always produced a 20 pronation. These data confirm that deafferented patients were not coding a final position. It rather suggests that they coded an amplitude and translated the spatial distance between the two targets in a corresponding force pulse. Overall, the results highlight the powerful and key role of proprioceptive afferents for calibrating the spatial motor frame of reference.     

Perceptual distortion of face deletion by local anaesthesia of the human lips and teeth

As visual guidance of facial movements is impossible, accurate movements for speech and mastication require an established body image that is formed via the information from mechanoreceptors in the skin, mucosa, periodontium, and proprioceptors in the facial and masticatory muscles and in the jaw joints. In this study we aimed to investigate how the acute deafferentation of lips and teeth alters the established image of lips, teeth and the thumb. We used a psychophysical method to determine whether the perceived sizes of the upper lip and front teeth change when the sensory input from the lips and front teeth is fully blocked. We also examined the perceived size of the thumb to test for acute interactions between the thumb and facial structures. Local anaesthetic blocking of upper lip and upper front teeth significantly increased the perceived size of the upper lip by as much as 100% (range 21–100%) in ten out of eleven subjects tested (overall mean 52%; p=0.001). The perceived size of the upper teeth also significantly increased by as much as 155% (range 30–155%) in eight of the eleven subjects during anaesthesia (overall mean 41%; p=0.035). When the region of anaesthesia was increased and both upper and lower teeth and lips were anaesthetised, the perceived size of the upper lip again increased, by 53% (p=0.040), but the change in perceived size of the upper front teeth (18%) was not significant (p=0.206). In both studies there was no change in perceived size of the thumb. The results illustrate the labile central interaction between sensory inputs and the importance of feedback from peripheral afferents in generating the subjective facial image. The timing, level, and area of anaesthesia may be important modifiers of these interactions.     

偏瘫患者平衡功能测定及相关因素的分析

目的 探讨偏瘫患者平衡功能测定及影响因素,为偏瘫患者进行平衡训练提供依据。方法 正常人和偏瘫患者各３０例,采用平衡仪测定平衡功能（身体重心稳定系数和重心分布）,分析本体感觉障碍与严重肌痉挛对平衡功能的影响。结果 偏瘫患者身体重心明显偏向健侧（Ｐ＜０．０５）;偏瘫患者身体重心摆动系数明显高于正常组（Ｐ＜０．０５）;本体感觉障碍的偏瘫患者负重能力明显差于无本体感觉障碍的患者（Ｐ＜０．０５）。结论 偏瘫     

膝腱反射检查对前交叉韧带断裂和重建后本体感觉功能的评价

目的探讨膝腱反射检查对前交叉韧带断裂和重建后本体感觉功能的评价和意义。方法对20例单纯前交叉韧带断裂,采用关节镜下自体四股半腱肌-股薄肌肌腱重建。常规方法检查膝腱反射,双极表面电极电刺激髌韧带并记录股内侧肌肌电图。观察前交叉韧带断裂和重建后膝腱反射和肌电图的客观改变,结合临床"打软腿"的主观症状,研究主、客观相互关系。结果3项指标手术前后两样本率比较,差异有统计学意义(PKJ=0.004,PEMG=0.022,PS=0.000);3项指标手术前后改变率之间两两比较,差异无统计学意义(PKJ-EMG=0.495,PKJ-S=0.476,PEMG-S=0.163)。结论提出"前交叉韧带-膝腱反射弧"的观点,将膝腱反射检查作为前交叉韧带断裂和重建后的常规查体,借此评价膝关节本体感觉功能,以指导本体感觉的康复锻炼。     

Cognitive loading-induced sway alterations are similar in those with chronic ankle instability and uninjured controls

Performing a cognitive task while balancing can result in either increased or decreased sway depending on the nature of the cognitive task, and is commonly used in pathologic populations to evaluate postural performance. A total of 39 participants were recruited into two groups: uninjured controls (n = 20, age: 21.9 ± 2.1 years, height: 175.0 ± 11.2 cm, mass: 71.3 ± 14.9 kg) and chronic ankle instability (n = 19, age: 22.1 ± 5.6 years, height: 169.7 ± 7.7 cm, mass: 72.9 ± 17.3 kg). Participants were asked to perform one of three cognitive tasks while maintaining single limb balance. Cognitive tasks included backwards counting by 3 (BC), the manikin test (MAN), and random number generation (RNG). Time-to-boundary minima, mean, and standard deviations were calculated and compared between groups as pre to post change scores. Effect sizes and 95% confidence intervals were also calculated to test for group differences and the effect of task performance on sway. No significant main effects of Group or Group by Task interactions were identified (p > 0.05). However, a significant multivariate main effect of Task was identified in BC (p = 0.001, F(6, 32) = 4.804) and RNG (p < 0.001, F(6, 32) = 6.233) but not for MAN (p = 0.117). The results suggest that those with chronic ankle instability and uninjured controls have similar postural–suprapostural interactions across multiple cognitive task domains. Both the BC and RNG tasks resulted in less sway for all participants. Our results suggest that dual-task interference in the CAI population may not be present as previous research would suggest.     

Effects of eight-week “gyroscopic device” mediated resistance training exercise on participants with impingement syndrome or tennis elbow

Background

Rehabilitation of injuries in the upper extremity and reestablishment of muscle strength throughout the range of motion in overhead movements, are the major concerns of athletes and coaches in the sports field.

Relationship Between Proprioception and Endurance Functionality of the Cervical Flexor Muscles in Chronic Neck Pain and Asymptomatic Participants

Objective

The purpose of this study was to compare the relationship between flexion endurance capacity and joint position error in participants with or without chronic neck pain (CNP).

An investigation of the effect of the lower extremity sensation on gait in children with cerebral palsy

BackgroundSensory disorders frequently accompany the motor disorders in children with cerebral palsy (CP).Research questionDo children with CP have sensory disturbances in their lower extremities? If there are sensory impairments, do these impairments affect gait?MethodsIn total, 45 children (18 females, 27 males) in an age range between 5 and 18 years were included in the study: 15 typically developing children, 15 unilaterally affected children with cerebral palsy, and 15 bilaterally affected children with cerebral palsy. They could walk independently at the levels of I or II according to the gross motor function classification. After the demographic data of the children were recorded, their tactile sense, vibration sense, two-point discrimination, and proprioception were evaluated, and the Edinburgh Visual Gait Score (EVGS) was used for gait assessment.ResultsFailures were discovered in lower extremity tactile (p = 0.001), two-point discrimination (p = 0.001), and proprioceptive senses of the children with CP (p = 0.001), and the loss of tactile sense was found to be related to gait disorders (p = 0.02, r = 0.41).SignificanceThere were deficiencies in the lower extremity senses, and deficiencies in the tactile sense negatively affected gait. Performing sensory assessments, which are considered to be fundamental for gait training in the rehabilitation of children with CP, and providing support for the lacking parameters in the intervention programs may create positive effects on gait.     

Real-time modulation of visual feedback on human full-body movements in a virtual mirror: development and proof-of-concept

Background

Virtual reality (VR) provides interactive multimodal sensory stimuli and biofeedback, and can be a powerful tool for physical and cognitive rehabilitation. However, existing systems have generally not implemented realistic full-body avatars and/or a scaling of visual movement feedback. We developed a “virtual mirror” that displays a realistic full-body avatar that responds to full-body movements in all movement planes in real-time, and that allows for the scaling of visual feedback on movements in real-time. The primary objective of this proof-of-concept study was to assess the ability of healthy subjects to detect scaled feedback on trunk flexion movements.

Methods

The “virtual mirror” was developed by integrating motion capture, virtual reality and projection systems. A protocol was developed to provide both augmented and reduced feedback on trunk flexion movements while sitting and standing. The task required reliance on both visual and proprioceptive feedback. The ability to detect scaled feedback was assessed in healthy subjects (n = 10) using a two-alternative forced choice paradigm. Additionally, immersion in the VR environment and task adherence (flexion angles, velocity, and fluency) were assessed.

Results

The ability to detect scaled feedback could be modelled using a sigmoid curve with a high goodness of fit (R² range 89-98%). The point of subjective equivalence was not significantly different from 0 (i.e. not shifted), indicating an unbiased perception. The just noticeable difference was 0.035 ± 0.007, indicating that subjects were able to discriminate different scaling levels consistently. VR immersion was reported to be good, despite some perceived delays between movements and VR projections. Movement kinematic analysis confirmed task adherence.

Conclusions

The new “virtual mirror” extends existing VR systems for motor and pain rehabilitation by enabling the use of realistic full-body avatars and scaled feedback. Proof-of-concept was demonstrated for the assessment of body perception during active movement in healthy controls. The next step will be to apply this system to assessment of body perception disturbances in patients with chronic pain.