Secondary sensory area SII is crucially involved in the preparation of familiar movements compared to movements never made before.

Secondary sensorimotor regions are involved in sensorimotor integration and movement preparation. These regions take part in parietal-premotor circuitry that is not only active during motor execution but also during movement observation and imagery. This activation particularly occurs when observed movements belong to one's own motor repertoire, consistent with the finding that motor imagery only improves performance when one can actually make such movement. We aimed to investigate whether imagery or observation of a movement that was never made before causes parietal-premotor activation or that the ability to perform this movement is indeed a precondition. Nine subjects [group Already Knowing It (AKI)] could abduct their hallux (moving big toe outward). Seven subjects initially failed to make such movement (Absolute Zero A0 group). They had to imagine, observe, or execute this movement, whereas fMRI data were obtained both before and after training. Contrasting abduction observation between the AKI-group and A0-group showed increased left SII and supplementary motor area activation. Comparing the observation of hallux flexion with abduction showed increased bilateral SII activation in the A0 and not in the AKI group. Prolonged training resulted in equal performance and similar cerebral activation patterns in the two groups. Thereby, conjunction analysis of the correlations on subject's range of abduction during execution, imagery, and observation of hallux abduction showed exclusive bilateral SII activation. The reduced SII involvement in A0 may imply that effective interplay between sensory predictions and feedback does not take place without actual movement experience. However, this can be acquired by training.

Cerebral consequences of dynamic immobilisation after primary digital flexor tendon repair.

Current treatment protocols for flexor tendon injuries of the hand generally result in an acceptable function, which can be quantified by objective parameters such as range of motion. The latter does not always match the patients' subjective experiences of persisting dysfunction. This raises the question whether changes in the cerebral control of movement might contribute to the perceived deficit. The main objective of the present positron emission tomography (PET) study was to characterise the cerebral responses in movement-associated areas during simple finger flexion immediately after dynamic immobilisation and after a subsequent 6-week period of active training. Ten subjects with flexor tendon injury participated in the PET study. Electromyography (EMG) recordings were made during finger flexion and extension in an additional subject. The main finding was that the (ventral) putamen contralateral to flexor movement was not activated immediately after release from splinting, while such activation reappeared after a period of training. This indicates a temporary loss of efficient motor control of over-learnt movements. The increase of unwanted co-contractions during flexion in a first EMG session, and not during extension, supports a concept of lost skills.

Motor imagery and action observation: cognitive tools for rehabilitation.

Rehabilitation, for a large part may be seen as a learning process where old skills have to be re-acquired and new ones have to be learned on the basis of practice. Active exercising creates a flow of sensory (afferent) information. It is known that motor recovery and motor learning have many aspects in common. Both are largely based on response-produced sensory information. In the present article it is asked whether active physical exercise is always necessary for creating this sensory flow. Numerous studies have indicated that motor imagery may result in the same plastic changes in the motor system as actual physical practice. Motor imagery is the mental execution of a movement without any overt movement or without any peripheral (muscle) activation. It has been shown that motor imagery leads to the activation of the same brain areas as actual movement. The present article discusses the role that motor imagery may play in neurological rehabilitation. Furthermore, it will be discussed to what extent the observation of a movement performed by another subject may play a similar role in learning. It is concluded that, although the clinical evidence is still meager, the use of motor imagery in neurological rehabilitation may be defended on theoretical grounds and on the basis of the results of experimental studies with healthy subjects.

Motor imagery: the relation between age and imagery capacity.

The imagination of motor actions forms not only a theoretical challenge for cognitive neuroscience but may also be seen as a novel therapeutic tool in neurological rehabilitation, in that it can be used for relearning motor control after damage to the motor system. However, since the majority of rehabilitation patients consist of older individuals it is relevant to know whether the capacity of mental imaging is compromised by age. Scores on the vividness of movement imagery questionnaire were obtained for 333 participants, divided in three age groups. Results showed that elderly participants were slightly worse in motor imagery capacity than younger participants, particularly in relation to motor imagery from an internal (first person) perspective. Furthermore, a possible relation between the level of physical activities and motor imagery capacity is discussed.

Abnormalities in the temporal patterning of lower extremity muscle activity in hemiparetic gait.

Following hemiparetic stroke, the timing of lower extremity muscle activity during gait often undergoes radical changes. In the present study, we compared the duration of activity in Biceps femoris (BF), Rectus femoris (RF), Tibialis anterior (TA) and Gastrocnemius medialis (GM) for four subphases of the gait cycle: the first double support phase (DS1), the single support phase (SS), the second double support phase (DS2) and the swing phase (SW) and compared these between 24 hemiparetic stroke patients and 14 healthy controls. In the upper leg, durations of BF and RF activity during SS were significantly longer on the paretic side (70% for BF, and 78% for RF) as well as on the nonparetic side (71% for BF, and 81% for RF), when compared to controls (45% and 53% for BF and RF, respectively). As a result, the duration of BF-RF coactivity during SS was longer in both legs of patients with stroke (61% in the paretic and 62% in the nonparetic leg) relative to control values (25%). In addition, during DS1 of the paretic leg, the total amount of BF-RF coactivity was abnormally long (82% versus 57% in controls). In the lower leg, longer total durations of GM activity were found during DS1 on the paretic side in people with stroke (51%) than in controls (38%). In the paretic TA, longer durations of activity were observed during SW (73% versus 60% in controls), whereas smaller total durations of activity were found during SS (28% versus 48% in controls). No statistically significant differences were found between the paretic and nonparetic leg within patients, except for the mean total duration of TA activity during DS1 (50% and 69% for the paretic and nonparetic leg, respectively). Overall, these results suggest that, despite large interindividual differences, some common disturbances can be observed in the temporal layout of muscle activity and coactivity associated with hemiparetic gait. Although these disturbances are more pronounced in the paretic leg, muscle activation patterns of the nonparetic leg also display some clear abnormalities.

Functional dominance of finger flexion over extension, expressed in left parietal activation.

Sensory stimuli may elicit a widely distributed parietal-premotor circuitry underlying task-related movements such as grasping. These stimuli include the visual presentation of an object to be grasped, as well as the observation of grasping performed by others. In this study, we used functional Magnetic Resonance Imaging (fMRI) to test whether the performance of simple finger flexion, contrasted to extension, might similarly activate higher-order circuitry associated with grasping. Statistical Parametric Mapping (SPM) showed that flexion, compared to extension, was related with significant activation of the left posterior parietal cortex and posterior insula, bilaterally. This pattern supported our hypothesis that simple finger flexion has a specific relation with circuitry involved in preparing manual tasks. Although the two motor conditions showed major overlap in the primary motor cortex, increased flexion-related activation at the precentral motor-premotor junction further supported its association with higher-order motor control.

Gait recovery is not associated with changes in the temporal patterning of muscle activity during treadmill walking in patients with post-stroke hemiparesis.

OBJECTIVE: To establish whether functional recovery of gait in patients with post-stroke hemiparesis coincides with changes in the temporal patterning of lower extremity muscle activity and coactivity during treadmill walking. METHODS: Electromyographic (EMG) data from both legs, maximum walking speed, the amount of swing phase asymmetry and clinical measures were obtained from a group of post-acute patients with hemiparesis, as early as possible after admission in a rehabilitation centre (mean time post-stroke 35 days) and 1, 3, 6, and 10 weeks later, while all patients participated in a regular rehabilitation program. EMG data from the first assessment were compared to those obtained from a group of healthy controls to identify abnormalities in the temporal patterning of muscle activity. Within subject comparisons of patient data were made over time to investigate whether functional gait recovery was accompanied by changes in the temporal patterns muscle (co-)activity. RESULTS: EMG patterns during the first assessment showed a number of abnormalities on the paretic side, namely abnormally long durations of activity in biceps femoris (BF) during the single support (SS) phase and in gastrocnemius medialis (GM) during the first double support phase (DS1). Furthermore, in both legs a prolongation of the activity was seen in the rectus femoris (RF) during the SS phase. In addition, the duration of BF-RF coactivation was longer on the paretic side than it was in controls. Over time, the level of ambulatory independence, body mobility, and maximum walking speed increased significantly, indicating that substantial improvements in gait ability occurred. Despite these improvements, durations of muscle (co-) activity and the level of swing phase asymmetry did not change during rehabilitation. More specifically, timing abnormalities in muscle (co-)activity that were found during the first assessment did not change significantly, indicating that these aberrations were not an impediment for functional gait improvements. CONCLUSIONS: Normalization of the temporal patterning of gait related muscle activity in the lower extremities is not a prerequisite for functional recovery of gait in patients with post-stroke hemiparesis. Apparently, physiological processes other than improved temporal muscular coordination must be important determinants of the restoration of ambulatory capacity after stroke. SIGNIFICANCE: Recovery of walking ability in post-stroke hemiparesis is not necessarily associated with, or dependent on, reorganization in the temporal control of gait related muscle activity. Normalization of the temporal coordination of muscle activity during gait may not be an important clinical goal during post-acute rehabilitation.

[Is the Activities-specific Balance Confidence Scale suitable for Dutch older persons living in the community?]. / Is de Activities-specific Balance Confidence Scale geschikt voor het meten van valangst bij Nederlandse niet-geïnstitutionaliseerde ouderen?

BACKGROUND: In ageing populations fear of falling is an important issue. International studies and collaborations require scales suitable to more cultures. Scales developed in one culture require adaptation and additional investigation of psychometric properties for use in other countries. OBJECTIVE: To investigate the psychometric properties of a Dutch version of the Activities-specific Balance Confidence scale (ABC-NL) and whether adding questions about complex/dual tasks improves the discriminatory power. METHOD: Subjects were 106 men and 140 women aged 65-92 years. Measures were the 16-item ABC-NL and seven additional more complex items, fall history, general and physical self-efficacy, a functional reach test and a balance platform test. RESULTS: The ABC-NL had a weak ceiling effect. Internal consistency (Cronbachs alpha) was high. The relationship between ABC-NL and physical self-efficacy was significantly stronger than between the ABC-NL and general self-efficacy. Relationships with performance-based measures of balance were moderate. Differences between fallers and non-fallers and between activity avoiders and non-avoiders were significant. Adding questions about complex tasks hardly improved discriminatory power, reliability and validity. CONCLUSION: Psychometric properties of the ABC-NL were satisfactory. Further research is needed for use in high-functioning older persons.

Is de Activities-specific Balance Confidence Scale geschikt voor het meten van valangst bij Nederlandse niet-geïnstitutionaliseerde ouderen?

Is the Activities-specific Balance Confidence Scale suitable for Dutch older persons living in the community? Background: In ageing populations fear of falling is an important issue. International studies and collaborations require scales suitable to more cultures. Scales developed in one culture require adaptation and additional investigation of psychometric properties for use in other countries.Objective: To investigate the psychometric properties of a Dutch version of the Activities-specific Balance Confidence scale (ABC-NL) and whether adding questions about complex/dual tasks improves the discriminatory power.Method: Subjects were 106 men and 140 women aged 65-92 years. Measures were the 16-item ABC-NL and seven additional more complex items, fall history, general and physical self-efficacy, a functional reach test and a balance platform test.Results: The ABC-NL had a weak ceiling effect. Internal consistency (Cronbachs alpha) was high. The relationship between ABC-NL and physical self-efficacy was significantly stronger than between the ABC-NL and general self-efficacy. Relationships with performance-based measures of balance were moderate. Differences between fallers and non-fallers and between activity avoiders and non-avoiders were significant. Adding questions about complex tasks hardly improved discriminatory power, reliability and validity.Conclusion: Psychometric properties of the ABC-NL were satisfactory. Further research is needed for use in high-functioning older persons.

Stumbling over obstacles in older adults compared to young adults.

Falls are a major problem in older adults. Many falls occur because of stumbling. The aim of the present study is to investigate stumbling reactions of older adults and to compare them with young adults. While subjects walked on a treadmill, a rigid obstacle unexpectedly obstructed the forward sway of the foot. In general, older adults used the same movement strategies as young adults ("elevating" and "lowering"). The electromyographic responses were categorized according to latencies: short-latency (about 45 ms, RP1), medium-latency (about 80 ms, RP2), and long-latency responses (about 110 ms, RP3; about 160 ms, RP4). Latencies of RP1 responses increased by about 6 ms and of RP2 by 10-19 ms in older adults compared with the young. Amplitudes of RP1 were similar for both age groups, whereas amplitudes of RP2-RP4 could differ. In the early-swing elevating strategy (perturbed foot directly lifted over the obstacle) older adults showed smaller responses in ipsilateral upper-leg muscles (biceps femoris and rectus femoris). This was related to shorter swing durations, more shortened step distances, and more failures in clearing the obstacle. In parallel, RP4 activity in the contralateral biceps femoris was enhanced, possibly pointing to a higher demand for trunk stabilization. In the late-swing lowering strategy (foot placed on the treadmill before clearing the obstacle) older adults showed lower RP2-RP3 responses in most muscles measured. However, kinematic responses were similar to those of the young. It is concluded that the changes in muscular responses in older adults induce a greater risk of falling after tripping, especially in early swing.

Suppressive musculocutaneous reflexes in tibialis anterior following upper leg stimulation at the end of the swing phase.

In the cat it is known that the distribution and modulation of the so-called P2 responses are similar, irrespective of whether they are obtained with electrodes implanted in the different skin areas or in the various leg muscles. In man it is known that the specific stimulation of cutaneous afferents from different parts of the foot evokes P2 responses, the phase-dependent modulation pattern of which exhibits both location-specific and common features. Responses generally differ, but one striking feature is the occurrence of suppressive responses in the tibialis anterior (TA) of the ipsilateral (i) leg at the end of the swing phase independent of the nerve stimulated. The question arises of whether this aspecificity is limited to the foot. Can similar suppressive P2 responses in iTA be obtained when afferents outside the region of the foot are stimulated during walking? If so this would indicate that there is a very general suppression occurring of input to the TA motor neuron pool, for example through presynaptic inhibition of a corticospinal drive. To answer this type of question the motor responses following transcutaneous stimulation of the rectus femoris (RF) and the motor responses following stimulation of the femoral nerve branch innervating the skin area above the quadriceps were determined during human locomotion. Electromyographic (EMG) activity in iTA was recorded by means of surface electrodes. In all subjects (N=10), the first consistent responses following RF stimulation occurred at about 80 ms poststimulus. The amplitude of these responses showed a clear phase-dependent modulation pattern. Facilitatory responses occurred during the end stance and early swing phase and turned into suppressive responses at the end of the swing phase. To investigate whether cutaneous afferents overlying the RF determined some of the responses following transcutaneous RF stimulation, the experiments were repeated following local anesthesia of the skin under the stimulation electrodes. This did not affect the responses substantially, indicating that most of the RF stimulation results were related to activation of muscle afferents. A similar phase-dependent modulation pattern was found following stimulation of cutaneous afferents of the femoral nerve (Fn). However, this phase-dependent modulation pattern was less pronounced and less consistent over the subjects when compared to the one found following RF stimulation. Our first conclusion is that the results show that P2 reflexes can be elicited both by stimulation of cutaneous afferents in the foot and by proximal cutaneous nerve and muscle stimulation. Secondly, it can be concluded that the suppressive responses at the end of the swing phase are present for both RF stimulation and stimulation of cutaneous afferents of the foot. This result indicates that a wide variety of afferent inputs have a suppressive influence on the input drive to TA motor neurons just prior to heel strike.

Adaptations in arm movements for added mass to wrist or ankle during walking.

The aim of the present study was to answer the question whether adaptations to local perturbations are restricted to the perturbed limb or whether they induce a reorganization of all co-moving limbs. Specifically, we studied the adaptations in arm movements to mass perturbations in seven healthy adults during walking on a treadmill. Four different perturbation conditions were employed in random order (no perturbation, mass added to both wrists, to the right wrist, and to the right ankle). During each experimental condition ten different belt speeds (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 km/h) were successively offered, while the arm movements and the electromyographic activity of the musculus deltoid posterior and anterior were measured. The results indicated that cadence was not affected by adding mass to the wrist or ankle. However, adding mass to a wrist not only resulted in an increase in muscle activity and a decrease of movement amplitude of the perturbed arm, but also in alterations in the non-perturbed arm. Notably, adding mass to one ankle induced adaptive changes in both arms, in that both muscle activity and arm movement increased. The present results indicate that during walking the loading of one of the limbs induces a general reorganization, involving all participating bodily segments, presumably to maintain balance while providing rhythm constancy.