Electromagnetic Muscle Stretch Strongly Excites Sensorimotor Cortex Neurons in Behaving Primates

Wolpaw, Jonathan R.

doi:10.1126/science.104385

“…33,34 Sensory signals conveyed from specific peripheral receptors in the limb of primates have been shown to have relatively direct access to the motor cortex. 35 However, the relative importance of the large diameter myelinated afferents as compared to the smaller type III and IV afferents in muscle fatigue is still controversial. [36][37][38][39][40] Another group of possible factors are changes in the other cortical and subcortical structures such as the premotor cortex, the supplementary motor area and its subcortical connections.…”

Section: Discussionmentioning

confidence: 99%

Age-Related Changes in Muscle Fatigue Resistance in Humans

Chan

¹

,

Raja

²

,

Strohschein

³

et al. 2000

Can. j. neurol. sci.

View full text Add to dashboard Cite

Some age-related changes in the motor system are welldescribed. For example, loss and atrophy of muscle fibers with a relatively greater decrease in the number and size of type II muscle fibers occur with aging. 1 There is also a progressive decline in the number of motoneurons with subsequent reinnervation and expansion of the innervation territory of the surviving motoneurons. [2][3][4][5][6] In the central nervous system, the extent of upper motoneuron loss with aging is substantial. 7,8 Taken together, it should not be surprising that some, or all, of these changes may have an impact on the muscle fatigue resistance in elderly individuals. Although muscle fatigue is of great functional importance in daily activities, data on its changes in aging, compared to strength changes, is relatively sparse. Also, reports on age-related changes in muscle fatigue resistance are conflicting. Findings range from increased fatigue resistance, 9,10 no change, 11 to decline. 12 The lack of agreement may, in part, be due to the different conditions under which muscle fatigue was induced and assessed. In some studies, ABSTRACT: Objective: The goal of this study was to compare the relative contributions from the muscle and the central nervous system to muscle fatigue resistance in aging. Methods: Each subject carried out 90 s of sustained maximal voluntary isometric contraction (MVC) of the thumb using the thenar and forearm thumb muscles. Contractile capacity of the thenar muscles was assessed through tetanic stimulation of the median nerve. Interpolated doublets delivered during an MVC represented the overall voluntary activation level while transcranial cortical stimulation with an electromagnetic stimulator was used to assess motor output upstream from the corticomotoneuronal pathway. Results: Nine elderly subjects [four females and five males, 70±9 years old (mean±SD)] and 10 younger subjects (five females and five males, 30±6 years old) were tested. After the fatiguing exercise, the elderly group's MVC declined by 29% as opposed to 47% in the younger group (p<0.01). The elderly group's greater fatigue resistance was accounted for by increased fatigue resistance at the muscle level as well as in the central nervous system. At least some of the decline in the central motor drive was upstream from the corticomotoneuronal pathway. Conclusion: The higher muscle fatigue resistance in the elderly group was attributable to differences in both the peripheral and central nervous systems.RÉSUMÉ: Changements dans la résistance à la fatigue musculaire associés au vieillissement chez l'humain. Objectif: Le but de cette étude était de comparer les contributions relatives du muscle et du système nerveux central à la résistance à la fatigue associée au vieillissement. Méthodes: Chaque sujet a effectué 90 s de contractions isométriques volontaires maximum soutenues (CVM) du pouce en utilisant les muscles de l'éminence thénar et de l'avant-bras. La capacité contractile des muscles de l'éminence thénar a été évaluée au moyen d'une stimulatio...

show abstract

Neural Control of Muscle Length and Tension

Houk

¹

,

Rymer

²

1981

Comprehensive Physiology

View full text Add to dashboard Cite

The sections in this article are: Control Theory Concepts Systems and Models Control Systems Feedback, Feedforward, and Adaptive Systems Principle of Negative Feedback Regulated Variables and Properties Control Configurations Summary Hypotheses of Motor Servo Function Salient Features of the Available Sensors Follow‐up Servo Hypothesis Spindle Receptors as Model‐Reference Error Detectors Conditional Feedback and Servo Assistance β‐System and the Possibility for Zero Sensitivity Stiffness Regulation Summary Model Adaptive Models Summary Muscle Mechanical Stiffness Stiffness Definitions Length Dependence Recruitment of Motor Units Rate Modulation of Motor Units Instantaneous Stiffness and Short‐Range Elasticity Instantaneous Stiffness Beyond the Short‐Range Region Ramp Responses: Transient Properties and Nonlinearity Natural Combinations of Recruitment and Rate Modulation Summary Central Pathways Primary Ending Projections Tendon Organ Projections Projections From Secondary Endings and Group II Free Nerve Endings Projections From Groups III and IV Free Nerve Endings Clasp‐Knife Reflex Long‐Loop Reflexes Summary Simplified Animal Models Decerebrate Preparation Spinal Preparation Summary Tonic Stretch Reflex in Functionally Isolated Muscles Basic Features of the Stretch Reflex Static Force‐Length Relations Normalized Stiffness Mechanically and Neurally Mediated Components Actions of Control Signals on the Motor Servo Dependence of Incremental Stiffness on Initial Force Loop Gain of Force Feedback Summary Static Regulatory Characteristics in Intact Subjects Skeletal Mechanics and Coordinate Systems Steady‐State Responses to Changes in Load Force Torque‐Angle Relations Equivalent Stiffness and the Concept of Composite Motor Servos Effect of Instructional Set Gain Variation vs. Gain Control Summary Dynamic Responses to Mechanical Disturbances Dynamic Features of Force Development Dependence of Transient Responses on Initial Force Amplitude Dependence and Linearity Asymmetry of Motor Servo Response Compensation for Yielding Predictive Compensation: Feedforward vs. Nonlinear Feedback Viewpoints Vibration and the Stretch Reflex Velocity Dependence and Damping Summary Implementation of Movement Commands α‐γ‐Relations Positional Stiffness Deduced From Spindle Relations β‐Innervation of Muscle Spindles Analytical Approaches to Actions of α‐, β‐, and γ‐Motoneurons Equilibrium Point Control Stiffness Regulation vs. Stiffness Control Perturbations During Movement Compliance, Load Compensation, and Biological Design Summary

show abstract

Maturation of lower extremity EMG responses to postural perturbations: relationship of response-latencies to development of fastest central and peripheral efferents

Müller

¹

,

Hömberg

²

,

Coppenrath

³

et al. 1991

View full text Add to dashboard Cite

EMG responses to toe-up tilt perturbations on a movable platform system were analysed in 86 children between the age of 12 months and 13 years. To assess the relative contribution of peripheral and central nerve conduction properties, a concomitant recording of the fastest efferent pathways in the central and peripheral motor system was made using non-invasive transcranial magnetic stimulation of motor cortex and peripheral nerve roots. This allowed the determination of the fastest downstream efferent connection times from motor cortex to lumbar motor neuron pools and to measure the fastest efferent conduction from these motor neuron pools to effector muscles in the lower leg. The sequence observed for stance stabilizing EMG responses was similar to that obtained in earlier studies with short latency (SL) and middle latency (ML) companents occurring in the stretched triceps surae muscle and long latency (LL) responses occurring in the non-stretched tibialis anterior muscle. Homologous responses were also obtained in upper leg muscles, being recruited consistently later than those in lower leg muscles across all age groups. In the short latency range two different SL1- and SL2-responses were obtained in children of all age groups as well as in adult controls. Both the SL1- and the SL2-responses showed a flat developmental profile, reaching adult values between 20 and 30 months of age which correlated with that of the fastest efferents from lumbar motor neuron pools to leg muscles, i.e. the final motor path. ML-responses showed a steeper developmental profile.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

Electromagnetic Muscle Stretch Strongly Excites Sensorimotor Cortex Neurons in Behaving Primates

Cited by 7 publications

References 9 publications

Age-Related Changes in Muscle Fatigue Resistance in Humans

Age-Related Changes in Muscle Fatigue Resistance in Humans

Neural Control of Muscle Length and Tension

Maturation of lower extremity EMG responses to postural perturbations: relationship of response-latencies to development of fastest central and peripheral efferents

Contact Info

Product

Resources

About