Disturbances in human arm movement trajectory due to mild cerebellar dysfunction.

The temporal structure of arm movements was studied in nine cerebellar patients with mild impairment of the upper limbs and in six age-matched control subjects. The experimental paradigm consisted of visually guided, step tracking movements about the elbow. Movements ranged from 10 degrees to 70 degrees in amplitude and were made under different instructions (fast, fast/accurate, accurate). As in normal subjects, cerebellar patients were able to scale peak velocity with movement amplitude. This relationship was highly linear under all instruction conditions. Similar relationships existed between movement duration and amplitude. In contrast to normal subjects who produced movements with nearly symmetric velocity profiles, movements made by cerebellar patients were characterised by short acceleration and long deceleration durations. The degree of asymmetry was directly related to movement duration but was unaffected by movement peak velocity. Acceleration durations did not increase beyond 300 ms even in movements lasting up to 1s. These findings demonstrate that, despite little or no obvious impairment of the limb during routine examination, the temporal structure of voluntary movements in cerebellar patients is clearly disturbed. This supports the view that the production of an optimal movement trajectory is under cerebellar influence.     

Neck movement speed in cervical dystonia

Clinical scales of patients with cervical dystonia do not rate neck movement velocity. We prospectively measured range of neck movements and movement velocities in 35 consecutive patients with cervical dystonia (CD) and 29 normal controls. Reduction of peak velocities in patients with CD was the most robust abnormality and was correlated to TWSTRS. Coupled movements out of attempted movement plane were increased in the patient group. Movement range was moderately though significantly reduced. We conclude that slowing of voluntary neck movements is a frequent and hitherto unrecognized feature in CD. © 2009 Movement Disorder Society     

Voluntary movement at the elbow in spastic hemiparesis

The relative importance of hyperreflexia and paresis in disturbances of voluntary arm movement was studied in a group of patients (n = 25) with spasticity arising from a unilateral ischemic cerebral lesion. Patient performance was evaluated against data obtained from normal subjects (n = 15). Spastic patients achieved lower maximum movement velocities during flexion or extension than did normal subjects. The more marked the paresis of the elbow flexor and extensor muscles of the patients, relative to the strength of the normal subjects, the greater was this reduction in maximum velocity. For a given velocity, however, the time taken to complete a movement and the time to reach the peak velocity were normal. No relationship was found between the degree of impairment of voluntary movement and the level of passive muscle hypertonia in the antagonist. Although overactivity of the antagonist muscle may play some role in disturbance of movements made at low velocities without an opposing load, antagonist activity during movements made against a load (i.e., under more natural conditions) was at or below normal levels, even in those patients with the most marked passive muscle hypertonia. It is concluded that agonist muscle paresis, rather than antagonist muscle hypertonia, plays the dominant role in the disturbance of voluntary elbow movement following stroke.     

Voluntary,spontaneous, and reflex blinking in Parkinson's disease

Blinking, a motor act consisting of a closing and an opening eyelid movement, can be performed voluntarily, spontaneously, and reflexly. In this study we investigated the kinematic features of voluntary, spontaneous, and reflex blinking in patients with Parkinson's disease (PD), OFF and ON dopaminergic treatment. Patients were asked to blink voluntarily as fast as possible. Spontaneous blinking was recorded for a minute during which the subjects just relaxed. Reflex blinking was evoked by electrical stimulation on the supraorbital nerve. Eyelid movements were recorded with the SMART analyzer motion system. Patients OFF therapy paused longer than controls during voluntary blinking but not during spontaneous and reflex blinking. The blink rate tended to be lower in patients OFF therapy than in controls and the spontaneous blinking had abnormally low amplitude and peak velocity. Finally, in patients OFF therapy the excitability of the neural circuit mediating the closing phase of the reflex blinking was enhanced. Dopaminergic treatment shortened the pause during voluntary blinking and increased the blink rate. In PD patients the longer pauses between the closing and opening phase in comparison to normal subjects, suggest bradykinesia of voluntary blinking. PD patients also display kinematic abnormalities of spontaneous blinking and changes in the excitability of the closing phase of reflex blinking. © 2007 Movement Disorder Society     

Kinematics of Arm Joint Rotations in Cerebellar and Unskilled Subjects Associated with the Inability to Throw Fast

Cerebellar subjects and unskilled throwers cannot produce fast arm movements when throwing. We investigated the arm movement kinematics associated with this lack of skill. Cerebellar subjects and matched controls, and skilled throwers throwing with their skilled (dominant) and unskilled (nondominant) arms, were instructed to make slow, medium, and fast 3-D overarm throws from a sitting position. Only the fast throws were analyzed in detail. Joint motions were computed from angular positions of arm segments recorded with search coils. When throwing, both the cerebellar group and the unskilled-arm group had slower arm movements, and slower elbow extension and wrist flexion velocities than their reference groups. They also had similar magnitudes of many kinematic parameters, e.g., both cerebellar and unskilled groups had similar elbow extension and wrist flexion velocities. Compared to their reference groups, both the cerebellar and unskilled-arm groups also had a smaller elbow extension acceleration, a smaller shoulder adduction deceleration, and the absence of a large elbow extension deceleration before ball release. Similar decreases in joint velocities and in joint accelerations and decelerations in the cerebellar and unskilled groups are consistent with the idea that the absence of the skill of throwing fast in both groups is associated with an inability to exploit interaction torques.     

Reciprocal change of motor-evoked potentials preceding voluntary movement in humans

Reciprocal change of motor-evoked potentials (MEPs) recorded from the agonist and antagonist muscles of the forearm was studied in 10 normal subjects in whom transcranial magnetic stimulation (TMS) was applied to the hand motor area before voluntary wrist movements. MEP recorded from the agonist muscles, that is, radial extensor muscles for wrist extension and ulnar flexor muscle for wrist flexion, were gradually facilitated with shortening of the interval between the magnetic stimulation and the voluntary muscle contraction. In contrast, MEP recorded from the antagonist muscles, that is, ulnar flexor muscle for wrist extension and radial extensor muscles for wrist flexion, were gradually suppressed as the interval shortened. The reciprocal change of MEP was recognized when TMS was applied within 60 ms prior to the voluntary movements. The present data confirmed that reciprocal change of MEP was recognized before voluntary movements; they further suggest that cortically originated reciprocal control of the corticospinal pathway may exist and that it may be generated just before the voluntary movement. © 1996 John Wiley & Sons, Inc.     

Proprioceptive regulation of voluntary ankle movements, demonstrated using muscle vibration, is impaired by Parkinson''s disease

OBJECTIVE: To test the hypothesis that the proprioceptive regulation of voluntary movement is disturbed by Parkinson's disease, the effects of experimental stimulation of proprioceptors, using muscle vibration, on the trajectories of voluntary dorsiflexion movements of the ankle joint were compared between parkinsonian and control subjects. METHODS: Twenty one patients with Parkinson's disease, on routine medication (levodopa in all but one), and an equal number of age matched, neurologically intact controls, were trained initially to make reproducible ankle dorsiflexion movements (20 degrees amplitude with a velocity of 9.7 degrees /s) following a visual "go" cue while movement trajectories were recorded goniometrically. During 50% of the experimental trials, vibration (105 Hz; 0.7 mm peak to peak) was applied to the Achilles tendon during the ankle movement to stimulate antagonist muscle spindles; vibrated and non-vibrated trials were interspersed randomly. Subjects' performance was assessed by measuring end point position-that is, the ankle angle attained 2 seconds after the visual "go" cue, from averaged (20 trials) trajectories. RESULTS: Statistical analysis of the end point amplitudes of movement showed that, whereas the amplitudes of non-vibrated movements did not differ significantly between patients with Parkinson's disease and controls, antagonist muscle vibration produced a highly significant reduction in the amplitudes of ankle dorsiflexion movements in both the patient and control groups. However, the extent of vibration induced undershooting produced in the patients with Parkinson's disease was significantly less than that in the controls; the mean vibrated/non-vibrated ratios were 0.86 and 0.54 for, respectively, the patient and control groups. CONCLUSIONS: The present finding of a reduction of vibration induced ankle movement errors in parkinsonian patients resembles qualitatively previous observations of wrist movements, and suggests that Parkinson's disease may produce a general impairment of proprioceptive guidance.     

Effects of velocity on maximal torque production in poststroke hemiparesis

Impaired torque production is a major physical impairment following stroke, and has been studied extensively in isometric conditions. However, functional use of a limb requires torque production during movement, and the effects of velocity on maximal torque production may be abnormally enhanced in the paretic limb. The purpose of this study was to quantify the effects of movement velocity on maximal torque production during isokinetic, concentric flexion and extension of the elbow in poststroke subjects. Three speeds were tested (30, 75, 120 deg/s) over a 100-deg range of motion. To control for strength variations between subjects and limbs, isokinetic torques were normalized by peak isometric torque. As flexion velocity increased, paretic limb torque decreased at a greater rate than in the unaffected limb. During extension, paretic limb torque was much lower than torque in the unaffected limb at all speeds. In both flexion and extension, the disparity between limbs in the constant-velocity torque-angle curves became more pronounced as velocity increased. Torque decreased 44% +/- 7% in flexion and 63% +/- 9% in extension as velocity increased from 30 to 120 deg/s, whereas the corresponding decreases in the unaffected limb were only 9% +/- 5% in flexion and 16% +/- 4% in extension. No electromyographic (EMG) abnormalities were observed during flexion. During extension, EMG data provided evidence for abnormally increased antagonist coactivation in brachioradialis and markedly reduced activation in triceps as potential contributors to the decreased extension torques. The finding that movement velocity produces large deficits in maximal torque might explain why functional use of the paretic limb is often impaired even though isometric strength appears adequate.     

Impairment of individual finger movements in patients with hand dystonia.

We investigated finger movements in patients with hand dystonia to compare the kinematics of repetitive individual and non-individual finger oppositions. We used an optoelectronic motion analysis system to record movements in 3-D space, and recorded three 5-second trials for each task, counting how many finger oppositions subjects carried out during each trial, and measured the duration and amplitude of flexions, extensions, and pauses. During tasks, normal subjects and patients carried out finger flexions faster than extensions, and invariably they paused longer before extension than before flexion. Patients were slower and paused longer than controls during both individual and non-individual oppositions. During individual finger movements, patients were disproportionately slow during extension and pause before extension. Patients with hand dystonia perform finger movements abnormally; they are affected predominantly during individual oppositions. This finding reflects the finer cortical control needed to promote and sustain this highly fractionated type of motor output, and points toward underactivity of the primary motor cortex in dystonia.     

等速测试同步电刺激正常人上肢肌肉力量的分析

背景：力量训练方法多种多样,而运用负荷加上同步电刺激进行训练的方法在国内报道较少。 目的：通过选定有效增强肌力的电流参数,利用等速测试来观察同步电刺激对正常人上肢肌肉肌力的影响,探讨在传统力量训练的同时使用电刺激,对增强肌肉力量和对肌肉屈伸比的作用。 设计、时间及地点：随机分组,对照观察实验,2007-09/2008-01在江苏省机关医院康复医学实验室进行测试。 对象：南京体育学院16名在校大学生进行同步电刺激上肢肌肉力量训练。 方法：将16名参试者随机均分为2组：对照组和刺激组。对照组用哑铃进行传统力量训练;刺激组用哑铃与同步电刺激进行结合训练。哑铃负重进行屈伸力量训练肱二头肌、肱三头肌,共12周,3次/周,2组/次,每组同一质量连续举6次。刺激组在进行哑铃训练的同时将电极片分别置于肱二头肌肱三头肌起止点处,进行电刺激,刺激强度20 mA,波宽0.3 ms,每刺激6~10 s后休息30~50 s,实际共刺激100 s左右。 主要观察指标：训练12周后利用BIODEX多关节等速测力及康复系统测试参试者屈伸状态下2个不同速度：60 (°)/s和120 (°)/s的峰值力矩、平均功率、屈伸肌比值。 结果：①在60 (°)/s和120 (°)/s角速度下等速运动,实验组与对照组伸肌肌群力量增长并不明显,甚至出现了最大力量的下降。②在60 (°)/s和120 (°)/s下,刺激组和对照组平均肌肉作用能量如同最大力矩呈现的相类似的特点,即伸肌肌群增长不明显,屈肌肌群有明显增长。在60(°)/s下刺激组的平均肌肉作用能量增长55%,120 (°)/s下增长了29% ,相应对照组分别增长了16%。③在60 (°)/s下,即慢速运动下,刺激后屈伸比趋向目标值,而在120 (°)/s下,屈伸比均超过了目标值。 结论：①同步肌肉电刺激可有有效增强肌肉最大力量,但随着运动角速度的增大,增强的效果越发不明显。②同步肌肉电刺激可以有效增加肌肉做功效率,在不同角速度下均有较明显的提高。③同步肌肉电刺激可以使肌肉屈伸比趋向目标值,一定角速度下维持屈伸肌力平衡,但在快速运动时,由于屈肌肌力过度发展会引起屈伸肌比值偏离目标值,从而更易于引起肌肉损伤。     

Physiological analysis of simple rapid movements in patients with cerebellar deficits.

Patients with cerebellar deficits made elbow flexion movements as rapidly as possible for three different angular distances. Electromyographic activity of biceps and triceps and the kinematics of the movements were analysed. Results were compared with those of normal subjects making both rapid and slow movements. In the patients, the first agonist burst of the biceps was frequently prolonged regardless of the distance or speed of the movement. The most striking kinematic abnormality was prolonged acceleration time. The pattern of acceleration time exceeding deceleration time was common in patients but uncommon in normal subjects. The best kinematic correlate of the duration of the first agonist burst was acceleration time. Altered production of appropriate acceleration may therefore be an important abnormality in cerebellar dysfunction for attempted rapid voluntary movements.     

A comparison of the effects of imposed extension and flexion movements on Parkinsonian rigidity.

OBJECTIVE: To test a hypothesis that Parkinsonian rigidity is more pronounced in imposed extension than flexion movement. METHODS: Twelve Parkinsonian subjects (both "Off" and "On" medication states) and seven control subjects participated in the protocol, in which a servomotor imposed wrist flexion and extension. Rigidity was quantitatively evaluated by the rectified torque integral with time, i.e., temporal score, and by the torque integral with joint angle, i.e., work score, for extension and flexion, respectively. RESULTS: In the "Off" state, the imposed extension induced a significantly higher resistance than did flexion. Dopaminergic medication significantly reduced the temporal score associated with imposed extension, and significantly decreased the work score of both movements. Compared with controls, the scores were higher for patients in the "On" state. CONCLUSIONS: Rigidity is more readily elicited in extension movement. The distinction is not evident in clinical practice, whereas it can be clearly revealed with the application of biomechanical analyses. SIGNIFICANCE: This distinction may prove to be a standard feature of rigidity. The procedures may be helpful in diagnosis and useful in evaluating new treatments and developing rehabilitation programs.     

Switching of movement direction is central to parkinsonian bradykinesia in sit-to-stand.

Patients with Parkinson's disease (PD) are known to manifest slowness in movements. We sought to identify the particular kinematic and kinetic disorders that contribute to the slowness in performing sit-to-stand in these patients. Two inter-related studies were carried out. In the first study, 20 patients with PD and 20 control subjects were instructed to perform sit-to-stand at a natural speed. In the second study, 15 control subjects were instructed to simulate the slower speed of sit-to-stand of the patients identified in the first study. Kinematic and kinetic data were recorded by a PEAK motion analysis system and two force platforms. The results showed that patients with PD generated smaller peak horizontal and vertical velocities during the task. They took a longer time to complete each individual phase as well as the whole movement of sit-to-stand. Patients also produced smaller peak hip flexion and ankle dorsiflexion joint torques and had prolonged time-to-peak torques from sit-to-stand onset. When control subjects simulated the patients' speed of sit-to-stand, there was no difference in all the kinematic and kinetic data between groups. The only exception was that they exhibited a shorter transition time between peak horizontal velocity (flexion phase) and seat-off (extension phase) than the patients. This study demonstrated that the slowness of PD patients during sit-to-stand at a natural speed could be attributed to inadequate peak hip flexion and ankle dorsiflexion torques, a prolonged torque production, as well as a difficulty in switching from the flexion to extension direction during sit-to-stand. As the latter difficulty persisted when the control subjects performed the task at a speed similar to that of the patients, our findings suggest that a fundamental problem of patients with Parkinson's disease could be a switch between movement directions.     

Cued and non-cued repetitive ballistic movements. A kinematic study in healthy subjects

Repetitive ballistic movements of the upper limbs were registered in 63 healthy subjects with an optoelectric 3-dimensional infrared computerized system. For evaluation of externally cued movements the arm was moved at maximum speed between two targets. As internally cued movements elbow flexion and extension at maximum speed was performed. At non-cued movements the subject shifted the hand between pronation and supination as fast as possible without further instructions. Movement velocity decreased progressively with increasing age at an annual rate of 0.5-0.6%. Women moved more slowly than men during cued movements, whereas no sex differences were found for non-cued movements. The peak velocity of cued movements remained unchanged during the 20 s performance period, whereas non-cued movements showed signs of fatigue with slowing. In conclusion, the maintenance of velocity during simple repetitive ballistic movements in healthy subjects depends on cueing and on sensory-motor function rather than on cognitive motor processing.     

Step-tracking movements of the wrist in humans. I. Kinematic analysis

We have examined the kinematics of the initial trajectory of step-tracking movements performed by human subjects. Each subject tracked a target that required 5-30 degrees of radial or ulnar deviation of the wrist. All movements were to be performed as accurately as possible. Speed instructions were given before each trial. When subjects performed different amplitude movements following the same speed instruction, the peaks of velocity, acceleration, and jerk were linearly related to peak displacement. The peaks of velocity, acceleration, and jerk also changed when the speed instruction was altered. Thus, for any given movement, the peak values of the derivatives of displacement were dependent on both movement amplitude and intended speed. As a result, the peak values of the derivatives cannot be used by themselves to control or monitor peak displacement. When subjects performed different amplitude movements following the same speed instruction, movement duration tended to remain constant. In contrast, movement duration changed when the speed instruction was altered. Movements performed when subjects intended to move slowly had longer durations than when subjects intended to move quickly. These results suggest that subjects volitionally alter intended speed by selecting different movement durations. When both movement amplitude and intended speed were varied, the peak displacement of a step-tracking movement was linearly related to the product of 2 kinematic variables: the initial peak of a derivative of displacement (either velocity, acceleration, or jerk) and movement duration. On the basis of our observations, we propose that central commands generate step-tracking movements of different amplitudes and intended speeds by adjusting both the magnitude and duration of a derivative of displacement.     

Enhanced negative slope of cortical potentials before sequential as compared with simultaneous extensions of two fingers

Cortical potentials preceding voluntary sequential extension of the right middle finger followed by the index finger were compared with those preceding voluntary simultaneous extension of the two fingers in 7 right-handed subjects who were trained to make the total duration of the EMG discharges approximately the same between the two movements. The negative slope with the sequential movement started earlier and was larger, especially at the vertex and also at the bilateral precentral areas, as compared with the simultaneous movement. There was no difference in the Bereitschaftspotential amplitude between the two movements. It was postulated that a greater and earlier activation of the supplementary motor areas as well as the primary hand sensorimotor areas is associated, both bilaterally, with the execution of the unilateral sequential movement.     

Jaw movement dysfunction related to Parkinson's disease and partially modified by levodopa.

OBJECTIVES--To test the hypotheses that Parkinson's disease can differentially produce deficits in voluntary and rhythmic jaw movements, which involve different neuronal circuits, and that levodopa treatment improves specific components of the motor deficit. METHODS--Patients with idiopathic Parkinson's disease and control subjects were tested on a series of jaw motor tasks that included simple voluntary movement, isometric clenching, and natural and paced rhythmic movements. Jaw movements were measured by changes in electromagnetic fields and EMG activity. Patients with Parkinson's disease with fluctuations in motor responses to levodopa were tested while off and on. RESULTS--During the off state, patients with Parkinson's disease were significantly worse than the control subjects on most tasks. The deficits included a decrease in amplitude and velocity during jaw opening and closing, aberrant patterns and low amplitude of EMG activity during clenching, and low vertical amplitude and prolonged durations of occlusion during rhythmic movements. No decrements were found in the amplitude of voluntary lateral jaw movements or the frequency of rhythmic movements. During the on state, improvements occurred in the patterns and level of EMG activity during clenching and in the vertical amplitude and duration of occlusion during rhythmic movements, although a significant decrement occurred in the lateral excursion of the jaw. CONCLUSIONS--Parkinson's disease affects the central programming of functionally related muscles involved in voluntary and rhythmic jaw movements and levodopa replacement influences only certain aspects of jaw movement, most likely those requiring sensory feedback.     

Quantitative measurement of trunk rigidity in parkinsonian patients

We aimed to develop an objective measurement to quantify trunk rigidity in patients with Parkinson's disease (PD), and to examine its reliability, validity and sensitivity in differentiating PD patients from control subjects. In Study 1, an isokinetic dynamometer was employed to assess trunk rigidity in 6 PD patients and 6 healthy controls. Passive trunk flexion and extension at 4 angular velocities were applied and resistive torques were recorded. Both work done and resistive peak torques to passive trunk flexion (Torque(PF)) and extension (Torque(PE)) were found to be highly reliable within a 2-day interval in PD patients and control subjects. In Study 2, trunk muscle tone was compared between 15 PD and 15 control subjects. Significantly higher muscle tone, as shown by increases in work done, and in Torque(PF) and Torque(PE )at higher movement speeds, was found in PD patients. Within each subject group, resistive trunk muscle tone was found to increase with increasing velocity of passive movement, but the extent of increase was greater in PD patients. Our results thus suggest that the objective method developed by us was reliable and could differentiate trunk rigidity in PD patients from that of healthy subjects.     

Adaptation motor learning of arm movements in patients with cerebellar disease.

OBJECTIVE--To design a test of motor learning using arm movements in normal subjects and patients with cerebellar disease. METHODS--Elbow angle was continuously displayed as a cursor (a dot) on a computer screen, and subjects made ballistic elbow flexion and extension movements to try to move the cursor between two targets on the screen. The relation between the arm movement and its visual feedback was changed, and the subjects reacted by adapting the amplitude of their movements in subsequent trials. RESULTS--The consecutive errors showed exponential learning curves during adaptation, which were quantified by their steepness. Ten patients with isolated cerebellar or olivopontocerebellar degeneration had less steep learning curves than normal subjects, indicating a failure of adaptation motor learning in cerebellar disease. The results show that this test may be useful for the analysis of motor learning.     

Kinematics of fast wrist movements in manic-depressive illness chronically treated with lithium carbonate

Abstract

Lithium salts have been shown to impair kinematics of fast voluntary movements during acute intoxication. The aim of the present study was to determine whether lithium carbonate affected the kinematics of fast movements in patients chronically treated and who did not exhibit signs of neurotoxicity. We analysed fast wrist flexion movements in 6 healthy subjects, in 5 patients presenting a manic-depressive illness without treatment, and in 8 patients receiving lithium carbonate for a manic-depressive disease. The mean duration of treatment was 3.9±4.1 years, the mean daily dose 837±341 mg and the mean serum level 0.95±0. 15 mEq/l. Although mean movement amplitudes were similar in the 3 groups, the variability of fast movements was increased in patients receiving lithium salts. The ratio of maximum to average velocities (VmNaveJ was significantly higher in patients treated, and their movements were temporally asymmetrical, with a ratio ofacceleration duration divided by deceleration duration being lower than in the 2 other groups. These kinematic abnormalities show that a chronic treatment with lithium salts is associated with an impairment of the cerebellar control of fast single-joint movements. [Neural Res 1998; 20: 320-326]