No abstract

In reaching for an object in the environment, it has been suggested that movement components concerned with transport of the hand toward the object and those related to grasping the object are organized and executed independently. An experiment is reported that demonstrates people adjust grasp aperture to compensate for factors affecting transport error. Grasp aperture was found to be greater in reaching movements performed faster than normal, and grasp aperture was also found to be wider when reaching with the eyes closed. In both cases, transport was spatially less accurate. It is argued that, in advance of movement, formation of grasp is planned to take into account not only the perceived characteristics of the object but, also, internalized information based on past experience about the likely accuracy of the transport component.

Prism adaptation has been shown to alleviate the symptoms of unilateral spatial neglect following stroke in single case and small group studies. The purposes of this single blinded pilot randomised controlled trial were to determine the feasibility of delivering prism adaptation treatment in a clinically valid sample and to assess its impact on self-care. Thirty seven right hemisphere stroke patients with unilateral spatial neglect were randomised into either prism adaptation (using 10 dioptre, 6 degree prisms) or sham treatment (using plain glasses) groups. Treatment was delivered each weekday for two weeks. Pointing accuracy, without vision of the finger, was recorded each day before treatment. Outcome was measured, by blinded assessors, four days and eight weeks after the end of treatment using the Catherine Bergego Scale (CBS) and the conventional neuropsychological tests from the Behavioural Inattention Test (BIT). Thirty four patients received treatment: 16 with prisms, 18 sham. Mean compliance was 99% and 97%, respectively. Over the treatment days only the prism treated group showed increased leftward bias in open loop pointing to targets on a touch screen. However, despite the group level changes in pointing behaviour no overall effect of the treatment on self-care or BIT were found.

The effectiveness of home therapy programmes for facilitating recovery of stroke patients' reaching movements was tested. Twenty-two patients were visited regularly at home for approximately 9 weeks following their discharge from a rehabilitation unit. Twelve patients were assessed and provided with a programme of exercises, while 10 were visited for assessment only. The home therapy group's performance on a peg transfer test improved significantly more than that of the control group. Compliance rates with the programmes were high. These results lead to suggestions for further evaluation of home therapy.

Objectives: To evaluate the amount of practice achieved and assess potential for effects on performance of 30 minutes of daily training in sit-to-stand. Design: Randomized controlled pilot study. Setting: Stroke rehabilitation unit, UK. Participants: Eighteen stroke patients needing `stand by' help to sit-to-stand. Interventions: In addition to usual rehabilitation the experimental group (n = 9) practised sit-to-stand and leg strengthening exercises for 30 minutes, on weekdays for two weeks, with a physiotherapy assistant. The control group received arm therapy. Main outcome measures: Frequency of sit-to-stands per day. Performance measures: rise time, weight taken through the affected foot at `thighs off', number of attempts needed to achieve three successful sit-to-stands and the number of sit-to-stands performed in 60 seconds. Outcome was measured one and two weeks after baseline assessment. Results: Sit-to-stand frequency averaged 18 per day. Thirty minutes of practice in sit-to-stand resulted in a mean of 50 (SD 17.2) extra stands per day. There was a significant mean difference of 10% body weight taken through the affected foot after one week of intervention: The control group had reduced weight through the affected leg while the training group increased weight (F1,16 = 11.1, P= 0.004, 95% confidence interval (CI) -16.61 to -3.72). No significant differences between groups were found on other measures. Results two weeks after baseline were inconclusive due to loss of five participants. Conclusions: Task-specific practice given for 30 minutes a day appears promising for patients learning to sit-to-stand.

Although it is well known that the corticospinal system exerts more influence over distal (hand and fingers) than proximal (elbow and shoulder) upper limb muscles, differences in the importance of this system for voluntary activation of these muscle groups have not been demonstrated directly. Two investigations were carried out to provide a quantitative comparison of the contribution of fast corticospinal inputs to voluntary activity in proximal and distal muscles of normal subjects. The first study confirmed that the rate of increase in the amplitude of EMG responses to transcranial magnetic stimulation (TMS) with voluntary activation of the muscles was significantly greater in a hand muscle (first dorsal interosseous, 1DI) than in biceps, which was in turn greater than that for deltoid. The second study demonstrated that this result reflected a genuine difference in corticospinal influence over these muscles and was not due to differences in the pattern and type of motor unit recruitment in proximal vs distal muscles. The voluntary activation of a pair of low-threshold single motor units (SMUs) in 1DI and deltoid was compared with their response to TMS. In both muscles only a small amount of additional effort was required to recruit the second SMU; increments were typically within 1% of maximum voluntary contraction, as assessed from EMG measurements. Subjects were asked to voluntarily discharge the lower threshold SMU at a steady rate, and then the threshold of responses of this SMU and that of the second unit to TMS were determined. In 1DI, only small increments in TMS intensity above the threshold for the first SMU were required to activate the second unit [mean 1.4% maximum stimulator output (MSO), SD +/- 1.0%, n = 7 subjects]. In contrast, in deltoid a significantly greater intensity increase was needed (mean 6%, SD +/- 1.2%, MSO n = 7, P < 0.001). Similar results were obtained when TMS thresholds of motor unit pairs were assessed in relaxed subjects. These experiments support the hypothesis that the fast corticospinal input that can be activated by TMS is of greater importance for the voluntary activation of hand than of shoulder muscles. This hypothesis served as a basis for testing deltoid responses in three stroke patients. In two patients smaller responses to TMS were obtained on the affected side than on the unaffected side during the production of equivalent voluntary contractions, suggesting that the patients achieved these contractions using inputs other than the fast corticospinal elements excited by TMS.

This paper reports the integration of a kinematic model of the human hand during cylindrical grasping, with specific focus on the accurate mapping of thumb movement during grasping motions, and a novel, multi-degree-of-freedom assistive exoskeleton mechanism based on this model. The model includes thumb maximum hyper-extension for grasping large objects (~> 50 mm). The exoskeleton includes a novel four-bar mechanism designed to reproduce natural thumb opposition and a novel synchro-motion pulley mechanism for coordinated finger motion. A computer aided design environment is used to allow the exoskeleton to be rapidly customized to the hand dimensions of a specific patient. Trials comparing the kinematic model to observed data of hand movement show the model to be capable of mapping thumb and finger joint flexion angles during grasping motions. Simulations show the exoskeleton to be capable of reproducing the complex motion of the thumb to oppose the fingers during cylindrical and pinch grip motions.

Patients with neglect veer to one side when walking or driving a wheelchair, however there is a contradiction in the literature about the direction of this deviation. The study investigated the navigational trajectory of a sample of neglect patients of mixed mobility status in an ecological setting. Fifteen patients with left-sided neglect after right hemisphere stroke were recorded walking or driving a powered wheelchair along a stretch of corridor. Their position in the corridor and the number of collisions was recorded. The results showed that the patients' path was dependent on their mobility status: wheelchair patients with neglect consistently deviated to the left of the centre of the corridor and walking patients with neglect consistently deviated to the right. A further two ambulant patients with neglect were recorded both walking and using the wheelchair to determine whether the differences were task or patient dependent. These two patients also exhibited leftward deviation when driving the wheelchair, but a rightward deviation when walking. These results suggest that the direction of the deviation is task dependent. Further work will be required to identify what features of the two modes of navigation lead to this dissociation.