共查询到20条相似文献,搜索用时 15 毫秒
1.
Stroeve S 《Biological cybernetics》1999,81(5-6):495-504
The modulation of neuromusculoskeletal impedance during movements is analysed using a motor control model of the human arm.
The motor control system combines feedback and feedforward control and both control modes are determined in one optimization
process. In the model, the stiffness varies at the double movement frequency for 2-Hz oscillatory elbow movements and has
high values at the movement reversals. During goal-directed two-degrees-of-freedom arm movements, the stiffness is decreased
during the movement and may be increased in the initial and final phases, depending on the movement velocity. The stiffness
has a considerable curl during the movement, as was also observed in experimental data. The dynamic stiffness patterns of
the model can be explained basically by the α−γ coactivation scheme where feedback gains covary with motor control signals.
In addition to the modulation of the gain factors, it is argued that the variation of the intrinsic stiffness has a considerable
effect on movement control, especially during fast movements.
Received: 14 October 1997 / Accepted in revised form: 18 May 1999 相似文献
2.
It has been suggested that incongruence between signals for motor intention and sensory input can cause pain and other sensory abnormalities. This claim is supported by reports that moving in an environment of induced sensorimotor conflict leads to elevated pain and sensory symptoms in those with certain painful conditions. Similar procedures can lead to reports of anomalous sensations in healthy volunteers too. In the present study, we used mirror visual feedback to investigate the effects of sensorimotor incongruence on responses to stimuli that arise from sources external to the body, in particular, touch. Incongruence between the sensory and motor signals for the right arm was manipulated by having the participants make symmetrical or asymmetrical movements while watching a reflection of their left arm in a parasagittal mirror, or the left hand surface of a similarly positioned opaque board. In contrast to our prediction, sensitivity to the presence of gaps in tactile stimulation of the right forearm was not reduced when participants made asymmetrical movements during mirror visual feedback, as compared to when they made symmetrical or asymmetrical movements with no visual feedback. Instead, sensitivity was reduced when participants made symmetrical movements during mirror visual feedback relative to the other three conditions. We suggest that small discrepancies between sensory and motor information, as they occur during mirror visual feedback with symmetrical movements, can impair tactile processing. In contrast, asymmetrical movements with mirror visual feedback may not impact tactile processing because the larger discrepancies between sensory and motor information may prevent the integration of these sources of information. These results contrast with previous reports of anomalous sensations during exposure to both low and high sensorimotor conflict, but are nevertheless in agreement with a forward model interpretation of perceptual modulations during goal directed movement. 相似文献
3.
Zehr EP Carroll TJ Chua R Collins DF Frigon A Haridas C Hundza SR Thompson AK 《Canadian journal of physiology and pharmacology》2004,82(8-9):556-568
There is extensive modulation of cutaneous and H-reflexes during rhythmic leg movement in humans. Mechanisms controlling reflex modulation (e.g., phase- and task-dependent modulation, and reflex reversal) during leg movements have been ascribed to the activity of spinal central pattern generating (CPG) networks and peripheral feedback. Our working hypothesis has been that neural mechanisms (i.e., CPGs) controlling rhythmic movement are conserved between the human lumbar and cervical spinal cord. Thus reflex modulation during rhythmic arm movement should be similar to that for rhythmic leg movement. This hypothesis has been tested by studying the regulation of reflexes in arm muscles during rhythmic arm cycling and treadmill walking. This paper reviews recent studies that have revealed that reflexes in arm muscles show modulation within the movement cycle (e.g., phase-dependency and reflex reversal) and between static and rhythmic motor tasks (e.g., task-dependency). It is concluded that reflexes are modulated similarly during rhythmic movement of the upper and lower limbs, suggesting similar motor control mechanisms. One notable exception to this pattern is a failure of contralateral arm movement to modulate reflex amplitude, which contrasts directly with observations from the leg. Overall, the data support the hypothesis that CPG activity contributes to the neural control of rhythmic arm movement. 相似文献
4.
Some characteristics of arm movements that humans exhibit during learning the dynamics of reaching are consistent with a
theoretical framework where training results in motor commands that are gradually modified to predict and compensate for novel
forces that may act on the hand. As a first approximation, the motor control system behaves as an adapting controller that
learns an internal model of the dynamics of the task. It approximates inverse dynamics and predicts motor commands that are
appropriate for a desired limb trajectory. However, we had previously noted that subtle motion characteristics observed during
changes in task dynamics challenged this simple model and raised the possibility that adaptation also involved sensory–motor
feedback pathways. These pathways reacted to sensory feedback during the course of the movement. Here we hypothesize that
adaptation to dynamics might also involve a modification of how the CNS responds to sensory feedback. We tested this through
experiments that quantified how the motor system's response to errors during voluntary movements changed as it adapted to
dynamics of a force field. We describe a nonlinear approach that approximates the impedance of the arm, i.e., force response
as a function of arm displacement trajectory. We observe that after adaptation, the impedance function changes in a way that
closely matches and counters the effect of the force field. This is particularly prominent in the long-latency (>100 ms) component
of response to perturbations. Therefore, it appears that practice not only modifies the internal model with which the brain
generates motor commands that initiate a movement, but also the internal model with which sensory feedback is integrated with
the ongoing descending commands in order to respond to error during the movement.
Received: 10 January 2001 / Accepted in revised form: 30 May 2001 相似文献
5.
Nikica Popovic Sybele Williams Thomas Schmitz-Rode Günter Rau Cantherine Disselhorst-Klug 《Journal of biomechanics》2009,42(10):1570-1573
Although arm movements play an important role in everyday life, there is still a lack of procedures for the analysis of upper extremity movement. The main problems for standardizing the procedure are the variety of arm movements and the difficult assessment of external hand forces. The first problem requires the predefinition of motions, and the second one is the prerequisite for calculation of net joint forces and torques arising during motion. A new methodology for measuring external forces during prespecified, reproducible upper extremity movement has been introduced and validated. A robot-arm has been used to define the motion and 6 degrees of freedom (DoF) force sensor has been attached to it for acquiring the external loads acting on the arm. Additionally, force feedback has been used to help keeping external loads constant. Intra-individual reproducibility of joint angles was estimated by using correlation coefficients to compare a goal-directed movement with robot-guided task. Inter-individual reproducibility has been evaluated by using the mean standard deviation of joint angles for both types of movement. The results showed that both inter- and intra-individual reproducibility have significantly improved by using the robot. Also, the effectiveness of using force feedback for keeping a constant external load has been shown. This makes it possible to estimate net joint forces and torques which are important biomechanical information in motion analysis. 相似文献
6.
It has been shown that target-pointing arm movements without visual feedback shift downward in space microgravity and upward in centrifuge hypergravity. Under gravity changes in aircraft parabolic flight, however, arm movements have been reported shifting upward in hypergravity as well, but a downward shift under microgravity is contradicted. In order to explain this discrepancy, we reexamined the pointing movements using an experimental design which was different from prior ones. Arm-pointing movements were measured by goniometry around the shoulder joint of subjects with and without eyes closed or with a weight in the hand, during hyper- and microgravity in parabolic flight. Subjects were fastened securely to the seat with the neck fixed and the elbow maintained in an extended position, and the eyes were kept closed for a period of time before each episode of parabolic flight. Under these new conditions, the arm consistently shifted downward during microgravity and mostly upward during hypergravity, as expected. We concluded that arm-pointing deviation induced by parabolic flight could be also be valid for studying the mechanism underlying disorientation under varying gravity conditions. 相似文献
7.
This paper presents a mathematical model for the learning of accurate human arm movements. Its main features are that the
movement is the superposition of smooth submovements, the intrinsic deviation of arm movements is considered, visual and kinesthetic
feedback are integrated in the motion control, and the movement duration and accuracy are optimized with practice. This model
is consistent with the jerky arm movements of infants, and may explain how the adult motion behavior emerges from the infant
behavior. Comparison with measurements of adult movements shows that the kinematics of accurate movements are well predicted
by the model.
Received: 15 May 1997 / Accepted 5 December 1997 相似文献
8.
After limb deafferentation, there was no gross alteration in the initiation and performance of a sound-triggered ballistic movement. The pattern of neuronal discharge in the arm area of the motor cortex was not significantly modified. In the absence of cerebellum, the reaction time of motor cortex cells was about 150 msec longer than the reaction time observed in normal and deafferented animals. This was associated with an equal retardation in the onset of ENG changes in the limb muscles. This observation is compatible with the idea that the motor cortex is normally situated downstream to the cerebellum in the initiation of some movements. However, the motor cortex is necessary for the initiation and execution of simple sound-triggered movements since its removal results in a permanent inability to perform the task. Finally, in the absence of peripheral feedback, the pattern of motor output to the agonistic and antagonistic muscles was initiated normally and thus appeared to be preprogrammed centrally. The importance of the motor cortex as a "reflex center" in the control of slower movements is obviously not challenged by these observations since the motor task that we have used depends very little or not at all on sensory feedback (Stark, 1968). What these results indicate, however, is that the execution of some voluntary fast ballistic movements can be entirely preprogrammed independently of peripheral and cerebellar influences, and that the program, which is mainly concerned with generating velocity signals, appears to require the integrity of the motor cortex for its execution. 相似文献
9.
The extremely flexible octopus arm provides a unique opportunity for studying movement control in a highly redundant motor system. We describe a novel preparation that allows analysis of the peripheral nervous system of the octopus arm and its interaction with the muscular and mechanosensory elements of the arm's intrinsic muscular system. First we examined the synaptic responses in muscle fibers to identify the motor pathways from the axial nerve cord of the arm to the surrounding musculature. We show that the motor axons project to the muscles via nerve roots originating laterally from the arm nerve cord. The motor field of each nerve is limited to the region where the nerve enters the arm musculature. The same roots also carry afferent mechanosensory information from the intrinsic muscle to the axial nerve cord. Next, we characterized the pattern of activity generated in the dorsal roots by electrically stimulating the axial nerve cord. The evoked activity, although far reaching and long lasting, cannot alone account for the arm extension movements generated by similar electrical stimulation. The mismatch between patterns of activity in the isolated cord and in an intact arm may stem from the involvement of mechanosensory feedback in natural arm extension. 相似文献
10.
E I Pal'tsev 《Biofizika》1992,37(6):1096-1100
Trained arm movements and two-link arm dynamics and control of arm movements model are investigated. It is found that for these movements the component of the movements energy dissipations in the control force potential is invariable during the outer force actions. 相似文献
11.
Locomotion of mammals, including humans, is based on the rhythmic activity of spinal cord circuitries. The functioning of these circuitries depends on multimodal afferent information and on supraspinal influences from the motor cortex. Using the method of transcranial magnetic stimulation (TMS) of arm muscle areas in the motor cortex, we studied the motor evoked potentials (MEP) in the upper arm muscles in stationary conditions and during voluntary and vibration-evoked arm movements. The study included 13 healthy subjects under arm and leg unloading conditions. In the first series of experiments, with motionless limbs, the effect of vibration of left upper arm muscles on motor responses in these muscles was evaluated. In the second series of experiments, MEP were compared in the same muscles during voluntary and rhythmic movements generated by left arm m. triceps brachii vibration (the right arm was stationary). Motionless left arm vibration led to an increase in MEP values in both vibrated muscle and in most of the non-vibrated muscles. For most target muscles, MEP was greater with voluntary arm movements than with vibration-evoked movements. At the same time, a similar MEP modulation in the cycle of arm movements was observed in the same upper arm muscles during both types of arm movements. TMS of the motor cortex significantly potentiated arm movements generated by vibration, but its effect on voluntary movements was weaker. These results indicate significant differences in the degree of motor cortex involvement in voluntary and evoked arm movements. We suppose that evoked arm movements are largely due to spinal rather than central mechanisms of generation of rhythmic movements. 相似文献
12.
Timothy J Brindle Arthur J Nitz Tim L Uhl Edward Kifer Robert Shapiro 《Journal of electromyography and kinesiology》2006,16(3):236-249
The objective of this study was to determine if simple, shoulder movements use the dual control hypothesis strategy, previously demonstrated with elbow movements, and to see if this strategy also applies in the absence of visual feedback. Twenty subjects were seated with their right arm abducted to 90 degrees and externally rotated in the scapular plane. Subjects internally rotated to a target position using a custom shoulder wheel at three different speeds with and without visual feedback. Kinematics were collected with a motion analysis system and electromyographic (EMG) recordings of the pectoralis major (PECT), infraspinatus (INFRA), anterior and posterior (ADELT, PDELT) deltoid muscles were used to evaluate muscle activity patterns during movements. Kinematics changed as movement speed increased with less accuracy (p<0.01). Greater EMG activity was observed in the PECT, PDELT, and INFRA with shorter durations for the ADELT, PDELT and INFRA. Movements with only kinesthetic feedback were less accurate (p<0.01) and performed faster (p<0.01) than movements with visual feedback. EMG activity suggests no major difference in CNS control strategies in movements with and without visual feedback. Greater resolution with visual feedback enables the implementation of a dual control strategy, allowing greater movement velocity while maintaining accuracy. 相似文献
13.
The possibility of muscle activation of passive arm during its cyclic movements, imposed by active movements of contralateral arm or by experimenter was studied, as well as the influence of lower extremities cyclic movements onto arm muscles activity. In addition to that the activity of legs muscles was estimated in dependence on motor task condition for arms. Ten healthy supine subjects carried out opposite movements of arms with and without stepping-like movements of both legs. The experiment included three conditions for arm movements: 1) the active movements of both arms; 2) the active movements of one arm, when other entirely passive arm participated in the movement by force; 3) passive arm movement caused by experimenter. In the condition 2) additional load on active arm was applied (30 N and 60 N). In all three conditions the experiment was carried out with arms movements only or together with legs movements. The capability of passive moving arm muscles activation depended on increasing afferent inflow from muscles of contralateral arm was demonstrated. Emerging electrical activity was modulated in the arms movements cycle and depended on the degree of active arm loading. During combined active movements of arms and legs the reduction of activity in the flexor muscles of shoulder and forearm was observed. Concomitant arms movements increased the magnitude ofelectromiographic bursts during passive stepping-like movements in the most of recorded muscles, and the same increasing was only observed in biceps femoris and tibialis anterior muscles during active legs movement. The increasing of loading of one arm caused essential augmentation of EMG-activity in the majority of recording legs muscles. The data obtained are the additional proof of existence of functionally significant neuronal interaction both between arms and between upper and lower extremities, which is evidently depend on the intraspinal neuronal connections. 相似文献
14.
Coordinated arm and leg movements imply neural interactions between the rhythmic generators of the upper and lower extremities. In ten healthy subjects in the lying position, activity of the muscles of the upper and lower extremities was recorded during separate and joint cyclic movements of the arms and legs with different phase relationships between the movements of the limbs and under various conditions of the motor task. Antiphase active arm movements were characterized by higher muscle activity than during the inphase mode. The muscle activity during passive arm movements imposed by the experimentalist was significantly lower than muscle activity during passive arm movements imposed by the other arm. When loading one arm, the muscle activity in the other, passively moving, arm increased independently from the synergy of arm movements. During a motor task implementing joint antiphase movements of both upper and lower extremities, compared to a motor task implementing their joint in-phase movements, we observed a significant increase in activity in the biceps brahii muscle, the tibialis anterior muscle, and the biceps femoris muscle. Loading of arms in these motor tasks has been accompanied by increased activity in some leg muscles. An increase in the frequency of rhythmic movements resulted in a significant growth of the muscle activity of the arms and legs during their cooperative movements with a greater rate of rise in the flexor muscle activity of the arms and legs during joint antiphase movements. Thus, both the spatial organization of movements and the type of afferent influences are significant factors of interlimb interactions, which, in turn, determine the type of neural interconnections that are involved in movement regulation. 相似文献
15.
In most clinical applications of functional electrical stimulation (FES), the timing and amplitude of electrical stimuli have been controlled by open-loop pattern generators. The control of upper extremity reaching movements, however, will require feedback control to achieve the required precision. Here we present three controllers using proportional derivative (PD) feedback to stimulate six arm muscles, using two joint angle sensors. Controllers were first optimized and then evaluated on a computational arm model that includes musculoskeletal dynamics. Feedback gains were optimized by minimizing a weighted sum of position errors and muscle forces. Generalizability of the controllers was evaluated by performing movements for which the controller was not optimized, and robustness was tested via model simulations with randomly weakened muscles. Robustness was further evaluated by adding joint friction and doubling the arm mass. After optimization with a properly weighted cost function, all PD controllers performed fast, accurate, and robust reaching movements in simulation. Oscillatory behavior was seen after improper tuning. Performance improved slightly as the complexity of the feedback gain matrix increased. 相似文献
16.
The present study investigates how the CNS deals with the omnipresent force of gravity during arm motor planning. Previous studies have reported direction-dependent kinematic differences in the vertical plane; notably, acceleration duration was greater during a downward than an upward arm movement. Although the analysis of acceleration and deceleration phases has permitted to explore the integration of gravity force, further investigation is necessary to conclude whether feedforward or feedback control processes are at the origin of this incorporation. We considered that a more detailed analysis of the temporal features of vertical arm movements could provide additional information about gravity force integration into the motor planning. Eight subjects performed single joint vertical arm movements (45° rotation around the shoulder joint) in two opposite directions (upwards and downwards) and at three different speeds (slow, natural and fast). We calculated different parameters of hand acceleration profiles: movement duration (MD), duration to peak acceleration (D PA), duration from peak acceleration to peak velocity (D PA-PV), duration from peak velocity to peak deceleration (D PV-PD), duration from peak deceleration to the movement end (D PD-End), acceleration duration (AD), deceleration duration (DD), peak acceleration (PA), peak velocity (PV), and peak deceleration (PD). While movement durations and amplitudes were similar for upward and downward movements, the temporal structure of acceleration profiles differed between the two directions. More specifically, subjects performed upward movements faster than downward movements; these direction-dependent asymmetries appeared early in the movement (i.e., before PA) and lasted until the moment of PD. Additionally, PA and PV were greater for upward than downward movements. Movement speed also changed the temporal structure of acceleration profiles. The effect of speed and direction on the form of acceleration profiles is consistent with the premise that the CNS optimises motor commands with respect to both gravitational and inertial constraints. 相似文献
17.
The possibility for the activation of muscles in a passive arm during its cyclic movements imposed by active movements of
the contralateral arm or by an experimenter and the effect that the movements of lower extremities have on the activity of
the arm muscles have been studied. In addition, the activity of the leg muscles was studied as dependent on the motor task
performed by the arms. Ten healthy subjects performed antiphase arm movements with and without stepping-like movements of
both legs in the supine position. The experiment was performed under three conditions for the arm movements: (1) both arms
performed active movements; (2) one arm performed active movements, and the contralateral arm, being entirely passive, was
forced to participate in movements; (3) the movement of the passive arm was caused by an experimenter. Under condition (2),
additional loadings of 30 and 60 N were applied to the active arm. Under all conditions, the arm movements were performed
with and without leg movements. The possibility for the activation of muscles in the arm performing passive movements has
been demonstrated. To a large extent, this is possible due to an increase in the afferent inflow from the muscles of the contralateral
arm. The electrical activity was modulated during cyclic arm movements and depended on the level of loading of the active
arm. During the combined active movements of the arms and legs, the reduction in the activity of the flexor muscles of the
shoulder and forearm was observed. In the case of passive stepping-like movements, the concomitant arm movements increased
the magnitude of electromyographic bursts in most of the examined leg muscles. During active leg movements, a similar increase
in electromyographic bursts was observed only in the m. biceps femoris (BF) and the anterior tibial muscle. An increase in
the loading of one arm caused a significant increase in the EMG activity in most examined muscles of the legs. The data obtained
provide additional proof for the existence of a functionally significant neuronal interaction between the arms, as well as
between the upper and lower extremities, which is probably due to intraspinal neuronal connections. 相似文献
18.
To study the effect of increasing amounts of exercising muscle mass on the relationship between glucose mobilization and peripheral glucose uptake, seven young men (23-28 yr) bicycled for 70 min at a work load of 55-60% VO2max. From minute 30 to 50, arm cranking was added and total work load increased to 82 +/- 4% VO2max. During leg exercise, hepatic glucose production (Ra) increased in parallel with peripheral glucose uptake (Rd) and euglycemia was maintained. During arm + leg exercise, Ra increased more than Rd and accordingly plasma glucose increased from 5.11 +/- 0.22 to 8.00 +/- 0.66 mmol/l (P less than 0.05). Plasma catecholamines increased three- to four-fold more during arm + leg exercise than during leg exercise. Leg glucose uptake increased with time regardless of arm cranking. Net leg lactate release during leg exercise was reverted to a net leg lactate uptake during arm + leg exercise. The rate of glycogen breakdown in exercising leg muscle was not altered by addition of arm cranking. In conclusion, when large amounts of muscle mass are active, plasma catecholamines increase sharply and mobilization of glucose exceeds peripheral glucose uptake. This indicates that mechanisms other than feedback regulation to maintain euglycemia are involved in hormonal and substrate mobilization during intense exercise in humans. 相似文献
19.
The common pattern of muscle activation and specifics of interlimb neuronal connections during the performance of rhythmic separate and simultaneous arm and leg movements in the lying position in healthy subjects, which reflected functionally significant interlimb neuronal interactions, were shown. The study was designed to investigate these mutual influences of the upper and lower limbs during the performance of similar motor tasks by stroke patients. Sixteen poststroke patients with different degrees of hemiparesis performed active and passive arm movements simultaneously with stepping leg movements or without them while lying supine. It was demonstrated that the patients had a disordered common pattern of distribution of muscle activity when they performed voluntary cyclic movements with both arms. Passive movements of both paretic and nonparetic arms led to different degrees of activation of their muscles, depending on the degree of paresis: in patients with mild paresis, muscle activation was similar to that in healthy subjects; in patients with severe paresis, it was insignificant. The loading of the nonparetic arm resulted in an increase in the activity in the paretic arm shoulder flexor muscles in patients with mild paresis (which was typical of healthy subjects), while loading did not influence significantly patients with severe paresis. The combination of cyclic arm movements and stepping leg movements in diagonal synergy decreased the activity in the proximal muscles of both arms, irrespective of the degree of paresis, as it was observed in healthy subjects. Simultaneous arm and leg movements did not change the muscle activity in nonparetic legs in either groups of patients, but the activity in the paretic leg muscles even decreased. The results obtained revealed important features of poststroke motor disturbances, which caused changes in interlimb interactions and largely depended on the degree of paresis. The data could be useful for developing new methods for the performance of rehabilitative procedures in poststroke patients. 相似文献
20.