Possible contributions of CPG activity to the control of rhythmic human arm movement (original) (raw)
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Journal of Neurophysiology - J NEUROPHYSIOL, 2004
During locomotor tasks such as walking, running, and swimming the arms move rhythmically with the legs. It has been suggested that connections between the cervical and lumbosacral spinal cord may mediate some of this interlimb coordination. However, it is unclear how these interlimb pathways modulate reflex excitability during movement. We hypothesized that rhythmic arm movement would alter the gain of reflex pathways in the stationary leg. Soleus Hreflexes recorded during arm cycling were compared to those recorded at similar positions with the arms stationary. Nerve stimulation was delivered with the right arm at approximately 70º shoulder flexion or 10º shoulder extension. H-reflexes were evoked alone (unconditioned) or with sural or common peroneal nerve (CP) conditioning to decrease or increase soleus IA presynaptic inhibition, respectively. Both conditioning stimuli were also delivered with no H-reflex stimulation. H-reflex amplitudes were compared at similar M-wave amplitudes and activation levels of the soleus. Arm cycling significantly reduced (p< 0.05) unconditioned soleus H-reflexes at shoulder flexion by 21.7% and at shoulder extension by 8.8%, compared to static controls. The results demonstrate a taskdependent modulation of soleus H-reflexes between arm cycling and stationary trials. Sural nerve stimulation facilitated H-reflexes at shoulder extension but not at shoulder flexion during static and cycling trials. CP nerve stimulation significantly reduced H-reflex amplitude in all conditions. Reflexes in soleus when sural and CP nerve stimulation were delivered alone, were not different between cycling and static trials; thus the task-dependent change in H reflex amplitude was not due to changes in motoneuron excitability. Therefore modulation occurred at a pre-motoneuronal level, probably by presynaptic inhibition of the IA afferent volley. Results indicate that neural networks coupling the cervical and lumbosacral spinal cord in humans are activated during rhythmic arm movement. It is proposed that activation of these networks may assist in reflex linkages between the arms and legs during locomotor tasks. Brooke JD, Cheng J, Collins DF, McIlroy WE, Misiaszek JE and Staines WR. Sensori-sensory afferent conditioning with leg movement: gain control in spinal reflex and ascending paths. Prog Neurobiol 51: 393-421, 1997. Calancie B. Interlimb reflexes following cervical spinal cord injury in man. Exp Brain Res 85: 458-469, 1991. Calancie B, Lutton S and Broton JG. Central nervous system plasticity after spinal cord injury in man: interlimb reflexes and the influence of cutaneous stimulation. Calancie B, Molano MR and Broton JG. Interlimb reflexes and synaptic plasticity become evident months after human spinal cord injury. Brain 125: 1150-1161, 2002. Capaday C, Lavoie BA and Comeau F. 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The Journal of Physiology, 2004
Rhythmic movements brought about by the contraction of muscles on one side of the body give rise to phase-locked changes in the excitability of the homologous motor pathways of the opposite limb. Such crossed facilitation should favour patterns of bimanual coordination in which homologous muscles are engaged simultaneously, and disrupt those in which the muscles are activated in an alternating fashion. In order to examine these issues, we obtained responses to transcranial magnetic stimulation (TMS), to stimulation of the cervicomedullary junction (cervicomedullary-evoked potentials, CMEPs), to peripheral nerve stimulation (H-reflexes and f-waves), and elicited stretch reflexes in the relaxed right flexor carpi radialis (FCR) muscle during rhythmic (2 Hz) flexion and extension movements of the opposite (left) wrist. The potentials evoked by TMS in right FCR were potentiated during the phases of movement in which the left FCR was most strongly engaged. In contrast, CMEPs were unaffected by the movements of the opposite limb. These results suggest that there was systematic variation of the excitability of the motor cortex ipsilateral to the moving limb. H-reflexes and stretch reflexes recorded in right FCR were modulated in phase with the activation of left FCR. As the f-waves did not vary in corresponding fashion, it appears that the phasic modulation of the H-reflex was mediated by presynaptic inhibition of Ia afferents. The observation that both H-reflexes and f-waves were depressed markedly during movements of the opposite indicates that there may also have been postsynaptic inhibition or disfacilitation of the largest motor units. Our findings indicate that the patterned modulation of excitability in motor pathways that occurs during rhythmic movements of the opposite limb is mediated primarily by interhemispheric interactions between cortical motor areas.
Bilateral Reflex Fluctuations during Rhythmic Movement of Remote Limb Pairs
Frontiers in Human Neuroscience
The modulation of spinal cord excitability during rhythmic limb movement reflects the neuronal coordination underlying actions of the arms and legs. Integration of network activity in the spinal cord can be assessed by reflex variability between the limbs, an approach so far very little studied. The present work addresses this question by eliciting Hoffmann (H-) reflexes in both limbs to assess if common drive onto bilateral pools of motoneurons influence spinal cord excitability simultaneously or with a delay between sides. A cross-covariance (CCV) sequence between reflexes in both arms or legs was evaluated under conditions providing common drive bilaterally through voluntary muscle contraction and/or rhythmic movement of the remote limbs. For H-reflexes in the flexor carpi radialis (FCR) muscle, either contraction of the FCR or leg cycling induced significant reduction in the amplitude of the peak at the zero lag in the CCV sequence, indicating independent variations in spinal excitability between both sides. In contrast, for H-reflexes in the soleus (SO) muscle, arm cycling revealed no reduction in the amplitude of the peak in the CCV sequence at the zero lag. This suggests a more independent control of the arms compared with the legs. These results provide new insights into the organization of human limb control in rhythmic activity and the behavior of bilateral reflex fluctuations under different motor tasks. From a functional standpoint, changes in the co-variability might reflect dynamic adjustments in reflex excitability that are subsumed under more global control features during locomotion.
Human cervical spinal cord circuitry activated by tonic input can generate rhythmic arm movements
Journal of Neurophysiology
The coordination between arms and legs during human locomotion shares many features with that in quadrupeds, yet there is limited evidence for the central pattern generator for the upper limbs in humans. Here we investigated whether different types of tonic stimulation, previously used for eliciting stepping-like leg movements, may evoke nonvoluntary rhythmic arm movements. Twenty healthy subjects participated in this study. The subject was lying on the side, the trunk was fixed, and all four limbs were suspended in a gravity neutral position, allowing unrestricted low-friction limb movements in the horizontal plane. The results showed that peripheral sensory stimulation (continuous muscle vibration) and central tonic activation (postcontraction state of neuronal networks following a long-lasting isometric voluntary effort, Kohnstamm phenomenon) could evoke nonvoluntary rhythmic arm movements in most subjects. In ∼40% of subjects, tonic stimulation elicited nonvoluntary rhythmic arm...
Z. Brain Research Reviews 30 1999 27--51
Motivated by the challenge of improving neuroprosthetic devices, the authors review current knowledge relating to harnessing the potential of spinal neural circuits, such as reflexes and pattern generators. If such spinal interneuronal circuits could be activated, they could provide the coordinated control of many muscles that is so complex to implement with a device that aims to address each participating muscle individually. The authors' goal is to identify candidate spinal circuits and areas of research that might open opportunities to effect control of human limbs through electrical activation of such circuits. David McCrea's discussion of the ways in which hindlimb reflexes in the cat modify motor activity may help in developing optimal strategies for functional neuromuscular Z. stimulation FNS , by using knowledge of how reflex actions can adapt to different conditions. Michael O'Donovan's discussion of the development of rhythmogenic networks in the chick embr...
Effects of Sensorimotor Rhythm Modulation on the Human Flexor Carpi Radialis H-Reflex
Frontiers in Neuroscience
People can learn over training sessions to increase or decrease sensorimotor rhythms (SMRs) in the electroencephalogram (EEG). Activity-dependent brain plasticity is thought to guide spinal plasticity during motor skill learning; thus, SMR training may affect spinal reflexes and thereby influence motor control. To test this hypothesis, we investigated the effects of learned mu (8-13 Hz) SMR modulation on the flexor carpi radialis (FCR) H-reflex in 6 subjects with no known neurological conditions and 2 subjects with chronic incomplete spinal cord injury (SCI). All subjects had learned and practiced over more than 10 <30-min training sessions to increase (SMR-up trials) and decrease (SMR-down trials) mu-rhythm amplitude over the hand/arm area of left sensorimotor cortex with ≥80% accuracy. Right FCR H-reflexes were elicited at random times during SMR-up and SMR-down trials, and in between trials. SMR modulation affected H-reflex size. In all the neurologically normal subjects, the H-reflex was significantly larger [116% ± 6 (mean ± SE)] during SMR-up trials than between trials, and significantly smaller (92% ± 1) during SMR-down trials than between trials (p < 0.05 for both, paired t-test). One subject with SCI showed similar H-reflex size dependence (high for SMR-up trials, low for SMR-down trials): the other subject with SCI showed no dependence. These results support the hypothesis that SMR modulation has predictable effects on spinal reflex excitability in people who are neurologically normal; they also suggest that it might be used to enhance therapies that seek to improve functional recovery in some individuals with SCI or other CNS disorders.
Modeling Neural Control of Locomotion: Integration of Reflex Circuits with CPG
Lecture Notes in Computer Science, 2002
A model of the spinal cord neural circuitry for control of cat hindlimb movements during locomotion was developed. The neural circuitry in the spinal cord was modeled as a network of interacting neuronal modules (NMs). All neurons were modeled in Hodgkin-Huxley style. Each NM included an αmotoneuron, Renshaw, Ia and Ib interneurons, and two interneurons associated with the central pattern generator (CPG). The CPG was integrated with reflex circuits. Each three-joint hindlimb was actuated by nine one-and two-joint muscles. Our simulation allowed us to find (and hence to suggest) an architecture of network connections within and between the NMs and a schematic of feedback connections to the spinal cord neural circuitry from muscles (Ia and Ib types) and touch sensors that provided a stable locomotion with different gaits, realistic patterns of muscle activation, and kinematics of limb movements.
Changes in Spinal Reflex Excitability Associated With Motor Sequence Learning
Journal of Neurophysiology, 2010
. Motivated by a paradigm in which but not lateral column transection prevents down-conditioning of reward depends on reflex amplitude, both primates and rats H reflex in rats. J. Neurophysiol. 78: 1730Neurophysiol. 78: -1734Neurophysiol. 78: , 1997. Operant can gradually increase or decrease the SSR or the H reflex. conditioning of the H reflex, the electrical analogue of the spinal The conditioning paradigm appears to induce a change in stretch reflex, in freely moving rats is a relatively simple model for descending influence that modifies the spinal cord and studying long-term supraspinal control over spinal cord function. changes the reflex (Carp and Wolpaw 1994; Feng-Chen and Motivated by food reward, rats can gradually increase or decrease Wolpaw 1996; Wolpaw and Lee 1989). the soleus H reflex. This study is the first effort to determine Recent studies in rats show that contusion injuries to thowhich spinal cord pathways convey the descending influence from racic spinal cord impair operant conditioning of the soleus supraspinal structures that changes the H reflex. In anesthetized Sprague-Dawley rats, the entire dorsal column (DC), which in-H reflex and that the degree of impairment is correlated with cludes the main corticospinal tract, or the right lateral column (LC) the size of the lesion . These results was transected by electrocautery. Animals recovered quickly and confirm the essential role of spinal cord pathways in H reflex the minimal transient effects of transection on the right soleus H conditioning. However, because contusions cause diffuse reflex disappeared within 16 days. Beginning at least 18 days after damage, they do not indicate which pathways are essential transection, 12 rats were exposed to the HRdown-conditioning for conditioning.
Journal of Neurology, Neurosurgery & Psychiatry, 1976
SYNOPSIS In 30 normal subjects, the influence of the reflex activation of one myotatic reflex arc on the excitability of other myotatic reflex arcs of the lower limb has been investigated using excitability curves. Soleus, quadriceps, and short biceps tendon reflexes as well as H reflex at two different intensities (liminal and H max/2) were used either as conditioning or as conditioned responses. The reflex activation of the soleus muscle has opposite effects on antagonistic muscle groups of the thigh: facilitation of the quadriceps myotatic arc and inhibition of the short biceps myotatic reflex arc. Conversely, activation of both quadriceps and short biceps muscles leads to a marked and long lasting (±5000 ms) inhibition of the soleus myotatic reflex arc. The differences of functional organization between proximal and distal myotatic reflex arcs are emphasized and the role of the afferent impulses secondary to the conditioning muscular contraction is discussed.