The effect of age and voluntary contraction on presynaptic inhibition of soleus muscle Ia afferent terminals in man

Butchart, P; Farquhar, Ruth; Part, N. J.; Roberts, R C

doi:10.1113/expphysiol.1993.sp003683

Cited by 41 publications

(40 citation statements)

References 15 publications

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“…The decrease in presynaptic inhibition of Ia afferents during the position task in young adults is consistent with previous results from our laboratory (Baudry and Enoka 2009). The present findings, however, did not show any change in the amount of Ia presynaptic inhibition during contractions performed at 5, 10, and 15% MVC force, which contrasts with previous studies that have found a decrease in the amount of Ia presynaptic inhibition in the soleus muscle with an increase in contraction strength of the plantarflexor muscles (Butchart et al 1993;Earles et al 2001). The divergent findings are likely attributable to differences in how the target torque was determined for each contraction: Earles et al (2001) used the amplitude of the surface EMG to set the intensity of the contraction, whereas Butchart et al (1993) used the same absolute torques across subjects.…”

Section: Discussioncontrasting

confidence: 56%

“…The present findings, however, did not show any change in the amount of Ia presynaptic inhibition during contractions performed at 5, 10, and 15% MVC force, which contrasts with previous studies that have found a decrease in the amount of Ia presynaptic inhibition in the soleus muscle with an increase in contraction strength of the plantarflexor muscles (Butchart et al 1993;Earles et al 2001). The divergent findings are likely attributable to differences in how the target torque was determined for each contraction: Earles et al (2001) used the amplitude of the surface EMG to set the intensity of the contraction, whereas Butchart et al (1993) used the same absolute torques across subjects. Accordingly, Meunier and Pierrot-Deseilligny (1998) reported no change in the amount of soleus Ia presynaptic inhibition across different contraction intensities when the target torque was set relative to the MVC torque (12, 25, and 50% MVC force).…”

Section: Discussioncontrasting

confidence: 56%

“…Several studies have found that old adults are less able than young adults to modulate presynaptic inhibition of Ia afferents converging onto the soleus motor neuron pool when exerting plantar flexion forces to match different target forces (Butchart et al 1993;Earles et al 2001) and when going from a supine to a standing position (Koceja and Mynark 2000). The reduced capacity of older adults to modulate Ia presynaptic inhibition in the lower limb, however, may not generalize to the upper limb where the modulation appears to be stronger.…”

Section: Introductionmentioning

confidence: 91%

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Presynaptic Modulation of Ia Afferents in Young and Old Adults When Performing Force and Position Control

Baudry

Maerz

Enoka

2010

Journal of Neurophysiology

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Baudry S, Maerz AH, Enoka RM. Presynaptic modulation of Ia afferents in young and old adults when performing force and position control. J Neurophysiol 103: 623-631, 2010. First published November 25, 2009 doi:10.1152/jn.00839.2009. The present work investigated presynaptic modulation of Ia afferents in the extensor carpi radialis (ECR) when young and old adults exerted a wrist extension force either to support an inertial load (position control) or to achieve an equivalent constant torque against a rigid restraint (force control) at 5, 10, and 15% of the maximal force. H reflexes were evoked in the ECR by stimulating the radial nerve above the elbow. A conditioning stimulus was applied to the median nerve above the elbow to assess presynaptic inhibition of homonymous Ia afferents (D1 inhibition) or at the wrist (palmar branch) to assess the ongoing presynaptic inhibition of heteronymous Ia afferents that converge onto the ECR motor neuron pool (heteronymous Ia facilitation). The young adults had less D1 inhibition and greater heteronymous Ia facilitation during the position task (79 and 132.1%, respectively) compared with the force task (69.1 and 115.1%, respectively, P Ͻ 0.05). In contrast, the old adults exhibited no difference between the two tasks for either D1 inhibition (ϳ72%) or heteronymous Ia facilitation (ϳ114%). Contraction intensity did not influence the amount of D1 inhibition or heteronymous Ia facilitation for either group of subjects. The amount of antagonist coactivation was similar between tasks for young adults, whereas it was greater in the position task for old adults (P ϭ 0.02). These data indicate that in contrast to young adults, old adults did not modulate presynaptic inhibition of Ia afferents when controlling the position of a compliant load but rather increased coactivation of the antagonist muscle.

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Section: Discussioncontrasting

confidence: 56%

Section: Discussioncontrasting

confidence: 56%

Section: Introductionmentioning

confidence: 91%

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Presynaptic Modulation of Ia Afferents in Young and Old Adults When Performing Force and Position Control

Baudry

Maerz

Enoka

2010

Journal of Neurophysiology

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“…Therefore, the impact of the afferent feedback on the agonist and antagonist motor neuron populations is reduced, although it is possible that an increased gamma drive may increase spindle output and thereby in part compensate for the decreased synaptic gain (Llewellyn et al 1990;. Baudry et al (2010) showed that young subjects increased the afferent gain when exposed to a more unstable task, whereas older subjects, who are less able to modulate presynaptic inhibition (Butchart et al 1993;Koceja and Mynark 2000), reacted with an increase in the cocontraction level. These observations suggest that cocontraction can be considered a more easily applied strategy that is often the first choice when a subject is exposed to an unknown environment, whereas it is more difficult, but also more desirable because of metabolic costs, to adjust the afferent gains to the appropriate level.…”

Section: Discussionmentioning

confidence: 99%

The optimal neural strategy for a stable motor task requires a compromise between level of muscle cocontraction and synaptic gain of afferent feedback

Dideriksen

Negro

Farina

2015

Journal of Neurophysiology

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Dideriksen JL, Negro F, Farina D. The optimal neural strategy for a stable motor task requires a compromise between level of muscle cocontraction and synaptic gain of afferent feedback. J Neurophysiol 114: 1895-1911, 2015. First published July 22, 2015 doi:10.1152/jn.00247.2015.-Increasing joint stiffness by cocontraction of antagonist muscles and compensatory reflexes are neural strategies to minimize the impact of unexpected perturbations on movement. Combining these strategies, however, may compromise steadiness, as elements of the afferent input to motor pools innervating antagonist muscles are inherently negatively correlated. Consequently, a high afferent gain and active contractions of both muscles may imply negatively correlated neural drives to the muscles and thus an unstable limb position. This hypothesis was systematically explored with a novel computational model of the peripheral nervous system and the mechanics of one limb. Two populations of motor neurons received synaptic input from descending drive, spinal interneurons, and afferent feedback. Muscle force, simulated based on motor unit activity, determined limb movement that gave rise to afferent feedback from muscle spindles and Golgi tendon organs. The results indicated that optimal steadiness was achieved with low synaptic gain of the afferent feedback. High afferent gains during cocontraction implied increased levels of common drive in the motor neuron outputs, which were negatively correlated across the two populations, constraining instability of the limb. Increasing the force acting on the joint and the afferent gain both effectively minimized the impact of an external perturbation, and suboptimal adjustment of the afferent gain could be compensated by muscle cocontraction. These observations show that selection of the strategy for a given contraction implies a compromise between steadiness and effectiveness of compensations to perturbations. This indicates that a task-dependent selection of neural strategy for steadiness is necessary when acting in different environments.

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“…presynaptic mechanism; see Pierrot-Desseilligny and Burke 2005;Stein 1995;Zehr and Stein 1999). A reduced ability to modulate presynaptic inhibition has been indeed suggested in elderly adults (Butchart et al 1993;Earles et al 2001). …”

Section: Age-related Changes In H-reflex Modulationmentioning

confidence: 98%

Modulation of reflex responses in activated ankle dorsiflexors differs in healthy young and elderly subjects

2011

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During voluntary contractions, motor neurone activity is modulated by descending input and sensory feedback. Impaired excitatory afferent feedback with ageing may, therefore, alter motor control. This study investigated the age-related changes in afferent feedback through the recording of reflex responses during voluntary muscle activation. Short-and long-latency components of the stretch reflex and Hoffmann reflex (H-reflex) were recorded during voluntary contractions (10% of maximal voluntary contraction; MVC) of the ankle dorsiflexor muscles of young and elderly adults (C70 years). Furthermore, the modulation of spinal reflex excitability was analyzed at different torque levels (10-50% MVC). The short-latency stretch reflex and the H-reflex areas were similar in the two age groups at 10% MVC whereas the area of the long-latency component of the stretch reflex augmented with ageing (P \ 0.05). However, the area of the H-reflex increased linearly with the level of contraction up to 50% MVC in young adults, whereas it slightly increased to 30% MVC and plateaued thereafter in elderly adults. The absence of age-related changes in the shortlatency stretch reflex and H-reflex areas suggests that the reflex circuitry and the sensitivity of the muscle spindles are not substantially affected by ageing. The modest increase in the H-reflex area with the contraction intensity in elderly adults, however, indicates that the modulation of afferent feedback is reduced with advancing age. This observation, associated with a greater long-latency stretch reflex, suggests that elderly adults rely more on central than peripheral mechanisms to regulate motor output of the dorsiflexor muscles.

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The effect of age and voluntary contraction on presynaptic inhibition of soleus muscle Ia afferent terminals in man

Cited by 41 publications

References 15 publications

Presynaptic Modulation of Ia Afferents in Young and Old Adults When Performing Force and Position Control

Presynaptic Modulation of Ia Afferents in Young and Old Adults When Performing Force and Position Control

The optimal neural strategy for a stable motor task requires a compromise between level of muscle cocontraction and synaptic gain of afferent feedback

Modulation of reflex responses in activated ankle dorsiflexors differs in healthy young and elderly subjects

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