Modulation of Transmission in the Corticospinal and Group Ia Afferent Pathways to Soleus Motoneurons During Bicycling

2003 ◽  
Vol 89 (1) ◽  
pp. 304-314 ◽  
Author(s):  
H. S. Pyndt ◽  
J. B. Nielsen
Keyword(s):  
Presynaptic Inhibition ◽  
Short Interval ◽  
Femoral Nerve ◽  
H Reflex ◽  
Emg Activity ◽  
Afferent Pathways ◽  
Corticospinal Pathway ◽  
Ia Afferents ◽  
Late Part

Transmission in the corticospinal and Ia pathways to soleus motoneurons was investigated in healthy human subjects during bicycling. Soleus H reflexes and motor evoked potentials (MEPs) after transcranial magnetic stimulation (TMS) were modulated similarly during the crank cycle being large during downstroke [concomitant with soleus background electromyographic (EMG) activity] and small during upstroke. Tibialis anterior MEPs were in contrast large during upstroke and small during downstroke. The soleus H reflexes and MEPs were also recorded during tonic plantarflexion at a similar ankle joint position, corresponding ankle angle, and matched background EMG activity as during the different phases of bicycling. Relative to their size during tonic plantarflexion, the MEPs were found to be facilitated in the early part of downstroke during bicycling, whereas the H reflexes were depressed in the late part of downstroke. The intensity of TMS was decreased below MEP threshold and used to condition the soleus H reflex. At short intervals (conditioning-test intervals of −3 to −1 ms), TMS produced a facilitation of the H reflex that is in all likelihood caused by activation of the fast monosynaptic corticospinal pathway. This facilitation was significantly larger in the early part of downstroke during bicycling than during tonic plantarflexion. This suggests that the increased MEP during downstroke was caused by changes in transmission in the fast monosynaptic corticospinal pathway. To investigate whether the depression of H reflexes in the late part of downstroke was caused by increased presynaptic inhibition of Ia afferents, the soleus H reflex was conditioned by stimulation of the femoral nerve. At a short interval (conditioning-test interval: −7 to −5 ms), the femoral nerve stimulation produced a facilitation of the H reflex that is mediated by the heteronymous monosynaptic Ia pathway from the femoral nerve to soleus motoneurons. Within the initial 0.5 ms after its onset, the size of this facilitation depends on the level of presynaptic inhibition of the Ia afferents, which mediate the facilitation. The size of the facilitation was strongly depressed in the late part of downstroke, compared with the early part of downstroke, suggesting that increased presynaptic inhibition was indeed responsible for the depression of the H reflex. These findings suggest that there is a selectively increased transmission in the fast monosynaptic corticospinal pathway to soleus motoneurons in early downstroke during bicycling. It would seem likely that one cause of this is increased excitability of the involved cortical neurons. The increased presynaptic inhibition of Ia afferents in late downstroke may be of importance for depression of stretch reflex activity before and during upstroke.

Mechanisms modulating spinal excitability after nerve stimulation inducing extra torque

2021 ◽  
Author(s):  
Florian Vitry ◽  
Maria Papaiordanidou ◽  
Alain Martin
Keyword(s):  
Nerve Stimulation ◽  
Presynaptic Inhibition ◽  
Motor Evoked Potentials ◽  
Femoral Nerve ◽  
Common Peroneal Nerve ◽  
H Reflex ◽  
Ia Afferents ◽  
Thoracic Level ◽  
The Common ◽  
Spinal Excitability

The study included 3 experiments aiming to examine the mechanisms responsible for spinal excitability modulation, as assessed by the H-reflex, following stimulation trains delivered at two different frequencies (20 and 100Hz) inducing extra torque (ET). A first experiment (n=15) was conducted to evaluate changes in presynaptic inhibition acting on Ia afferents induced by these electrical stimulation trains, assessed by conditioning the soleus H-reflex (tibial nerve stimulation) with stimulation of the common peroneal nerve (D1 inhibition) and of the femoral nerve (heteronymous Ia facilitation, HF). A second experiment (n=12) permitted to investigate homosynaptic post-activation depression (HPAD) changes after the stimulation trains. A third experiment (n=14) analysed changes in motoneuron intrinsic properties after the stimulation trains, by electrically stimulating the descending corticospinal tract at the thoracic level, evoking thoracic motor evoked potentials (TMEP). Main results showed that in all experiments spinal excitability decreased after the 20-Hz train (P<0.05), while this parameter significantly increased after the 100-Hz stimulation (P<0.05). D1 and HF were not significantly modified after either stimulation. HPAD was significantly decreased only after the 20-Hz train, while TMEP was significantly increased only after the 100-Hz train (P<0.05). It is concluded that the decreased spinal excitability observed after the 20-Hz train cannot be attributed to D1 presynaptic inhibition but rather to increased HPAD of the Ia afferents terminals, while the increase of this parameter obtained after the 100-Hz train can be assigned to changes in intrinsic motoneuron properties allowing to maintain Ia - alpha motoneurons transmission efficacy.

Differential effects of a flexor nerve input on the human soleus H-reflex during standing versus walking

1995 ◽  
Vol 73 (4) ◽  
pp. 436-449 ◽  
Author(s):  
C. Capaday ◽  
B. A. Lavoie ◽  
F. Comeau
Keyword(s):  
Spinal Cord ◽  
Presynaptic Inhibition ◽  
Stance Phase ◽  
Conditioning Stimulus ◽  
Background Level ◽  
H Reflex ◽  
Emg Activity ◽  
Group I ◽  
The Difference

A conditioning (C) stimulus at group I strength was delivered during standing to the common peroneal (CP) nerve before a test (T) stimulus at several C–T intervals ranging from 0 to 150 ms. At sufficiently long C–T intervals (100–120 ms) the soleus H-reflex was strongly inhibited despite little, or no change, in the background level of EMG activity. This finding indicates that a significant portion of the inhibition occurs at a premotoneuronal level, likely via presynaptic inhibition of the Ia-afferent terminals. During standing, at C–T intervals of 100–120 ms (optimal C–T interval) a conditioning stimulus to the CP nerve of 1.5 times motor threshold (MT) intensity reduced the soleus H-reflex by an average of 45.8% (n = 14 subjects). The conditioning stimulus always produced a clear inhibition of the H-reflex during standing at these C–T intervals. The effects of this conditioning stimulus on the soleus H-reflex were then determined in the early part of the stance phase of walking. In contrast to standing, the conditioning stimulus produced little or no inhibition during the early part of the stance phase of walking (average inhibition 45.8 vs. 11.6%, n = 14 subjects). The soleus background EMG, and the soleus and tibialis anterior M-waves were essentially the same during standing and walking. Furthermore, there was no shift of the optimal C–T interval during walking. The difference in the effects of the conditioning stimulus was not due to differences in the size of the test H-reflex in each task. It appears to be due to a genuine task-dependent change in the input–output properties of the underlying spinal cord circuits. There are at least two, mutually compatible, explanations of these results. Firstly, during walking the intraspinal terminals of the afferent fibres (group Ia and Ib) conducting the conditioning volley may be presynaptically inhibited, or their input gated at the interneuronal level. Secondly, on the assumption that the conditioning stimulus is acting via the presynaptic inhibitory network in the spinal cord, it is possible that during walking this network is saturated as a result of increased central or peripheral synaptic inputs. Finally, it seems unlikely that differences in the refractoriness of the CP nerve between the tasks may be involved; the reasons for this are presented in the discussion.Key words: Ia afferents, motoneurons, presynaptic inhibition, EMG, posture, locomotion, spinal cord.

scholarly journals Task- and time-dependent modulation of Ia presynaptic inhibition during fatiguing contractions performed by humans

2011 ◽  
Vol 106 (1) ◽  
pp. 265-273 ◽  
Author(s):  
Stéphane Baudry ◽  
Adam H. Maerz ◽  
Jeffrey R. Gould ◽  
Roger M. Enoka
Keyword(s):  
Presynaptic Inhibition ◽  
Angular Position ◽  
H Reflex ◽  
Time Dependent ◽  
Initial Value ◽  
Ia Afferents ◽  
Position Task ◽  
Motor Neuron Pool ◽  
Extensor Carpi Radialis ◽  
Fatiguing Contractions

Presynaptic modulation of Ia afferents converging onto the motor neuron pool of the extensor carpi radialis (ECR) was compared during contractions (20% of maximal force) sustained to failure as subjects controlled either the angular position of the wrist while supporting an inertial load (position task) or exerted an equivalent force against a rigid restraint (force task). Test Hoffmann (H) reflexes were evoked in the ECR by stimulating the radial nerve above the elbow. Conditioned H reflexes were obtained by stimulating either the median nerve above the elbow or at the wrist (palmar branch) to assess presynaptic inhibition of homonymous (D1 inhibition) and heteronymous Ia afferents (heteronymous Ia facilitation), respectively. The position task was briefer than the force task ( P = 0.001), although the maximal voluntary force and electromyograph for ECR declined similarly at failure for both tasks. Changes in the amplitude of the conditioned H reflex were positively correlated between the two conditioning methods ( P = 0.02) and differed between the two tasks ( P < 0.05). The amplitude of the conditioned H reflex during the position task first increased (129 ± 20.5% of the initial value, P < 0.001) before returning to its initial value ( P = 0.22), whereas it increased progressively during the force task to reach 122 ± 17.4% of the initial value at failure ( P < 0.001). Moreover, changes in conditioned H reflexes were associated with the time to task failure and force fluctuations. The results suggest a task- and time-dependent modulation of presynaptic inhibition of Ia afferents during fatiguing contractions.

scholarly journals Presynaptic and Postsynaptic Effects of the Anesthetics Sevoflurane and Nitrous Oxide in the Human Spinal Cord

2007 ◽  
Vol 107 (4) ◽  
pp. 553-562 ◽  
Author(s):  
Jan H. Baars ◽  
Michael Benzke ◽  
Falk von Dincklage ◽  
Josephine Reiche ◽  
Peter Schlattmann ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Nitrous Oxide ◽  
Presynaptic Inhibition ◽  
Femoral Nerve ◽  
Volatile Anesthetic ◽  
H Reflex ◽  
Receptor Subtype ◽  
Gamma Aminobutyric Acid ◽  
Human Spinal Cord ◽  
Two Parameters

Background Reduced spinal excitability contributes to the suppression of movement responses to noxious stimuli during the anesthetic state. This study examines and compares presynaptic and postsynaptic effects of two anesthetics in the human spinal cord. Methods The authors tested two parameters during the administration of 0.8 vol% sevoflurane or 40 vol% nitrous oxide compared with control states before and after drug administration: (1) the size of the soleus H reflex (integrating presynaptic and postsynaptic effects) at increasing stimulus intensities (recruitment curve) and (2) the amount of presynaptic inhibition on Ia afferents of the quadriceps femoris, evaluated by the heteronymous facilitation of the soleus H reflex caused by a conditioning stimulation of the femoral nerve. The study was performed in 10 subjects for each drug. Results At the chosen concentrations, the maximum H reflex was reduced by 26.3 +/- 8.4% (mean +/- SD) during sevoflurane and by 33.5 +/- 15.6% during nitrous oxide administration. The averaged recruitment curves were similarly depressed under the influence of the two drugs. The reduction of H-reflex facilitation was significantly stronger for sevoflurane (28.8 +/- 20.0%) than for nitrous oxide administration (6.2 +/- 26.4%). Conclusions These results demonstrate in humans presynaptic effects of the volatile anesthetic sevoflurane but not of nitrous oxide. A possible explanation for this difference may be the different potency of the respective drugs in enhancing gamma-aminobutyric acid type A receptor-mediated inhibition, because presynaptic inhibition in the spinal cord involves this receptor subtype.

Propofol Increases Presynaptic Inhibition of Ia Afferents in the Intact Human Spinal Cord

2006 ◽  
Vol 104 (4) ◽  
pp. 798-804 ◽  
Author(s):  
Jan H. Baars ◽  
Falk von Dincklage ◽  
Josephine Reiche ◽  
Benno Rehberg
Keyword(s):  
Spinal Cord ◽  
Tibial Nerve ◽  
Femoral Nerve ◽  
Conditioning Stimulus ◽  
Type A ◽  
H Reflex ◽  
Excitatory Postsynaptic Potential ◽  
Human Spinal Cord ◽  
Ia Afferents ◽  
Stimulation Of

Background In vitro studies indicate that the primary molecular targets of propofol in the spinal cord are gamma-aminobutyric acid (GABA) type A receptors. Because of the complexity of the central nervous system, specific GABA-mediated effects have not yet been isolated in humans. Here, the authors used heteronymous Ia facilitation of the soleus H-reflex from the femoral nerve as a specific pathway involving GABA to demonstrate a presynaptic GABA-mediated effect of propofol in humans. Methods The study was performed in 10 volunteers aged 23-32 yr. The soleus H-reflex was evoked by stimulation of the tibial nerve in the popliteal fossa. The stimulation current was adjusted to yield an unconditioned H-reflex of 15% of the maximal muscle response to electric stimulation of the tibial nerve. The soleus H-reflex was conditioned by stimulating Ia afferents from the quadriceps femoris in the femoral triangle. The stimulus was applied 0.3-0.4 ms after the onset of facilitation, to assure a purely monosynaptic excitatory postsynaptic potential from quadriceps Ia afferents to the soleus motoneuron. At least 45 conditioned (femoral and tibial) and unconditioned (only tibial) stimuli were applied in random order. The authors compared the amount of heteronymous H-reflex facilitation under a concentration of 2 microg/ml propofol with control values obtained before and after the propofol infusion. Results H-reflex facilitation due to the conditioning stimulus during propofol administration was significantly (P &lt; 0.05, t test) decreased by an average of 43% in all patients in comparison with the control values. Conclusions Although alternative explanations such as supraspinal effects cannot be ruled out completely, the findings of this study are most likely explained by a specific presynaptic effect of propofol. Strong evidence form neurophysiologic studies indicates that this effect is mediated by the GABA type A receptors.

Task-Specific Depression of the Soleus H-Reflex After Cocontraction Training of Antagonistic Ankle Muscles

2007 ◽  
Vol 98 (6) ◽  
pp. 3677-3687 ◽  
Author(s):  
Monica A. Perez ◽  
Jesper Lundbye-Jensen ◽  
Jens B. Nielsen
Keyword(s):  
Presynaptic Inhibition ◽  
Tibialis Anterior ◽  
Motor Performance ◽  
Motor Evoked Potentials ◽  
Intracortical Inhibition ◽  
H Reflex ◽  
Emg Activity ◽  
Frequent Use ◽  
Ankle Muscles ◽  
Simultaneous Activation

Ballet dancers have small soleus (SOL) H-reflex amplitudes, which may be related to frequent use of cocontraction of antagonistic ankle muscles. Indeed, SOL H-reflexes are depressed during cocontraction compared with plantarflexion at matched background EMG level. We investigated the effect of 30-min training of simultaneous activation of ankle dorsi- and plantarflexor muscles (cocontraction task) on the SOL H-reflex in 10 healthy volunteers. Measurements were taken during cocontraction. After training, there was a significant improvement in the ability of the subjects to perform a stable cocontraction. SOL H-reflex recruitment curves and H-max/M-max ratios were decreased after cocontraction training but not after 30 min of static dorsi or plantarflexion. The decreased H-reflex size correlated with improved motor performance. No changes in SOL and tibialis anterior (TA) EMG activity or EMG power were observed, suggesting that increased presynaptic inhibition of Ia afferents is a likely mechanism for H-reflex depression. In different sessions we measured SOL and TA motor-evoked potentials (MEPs) by using transcranial magnetic stimulation (TMS), TMS-elicited suppression of SOL EMG, and coherence between electroencephalographic (EEG) activity (Cz) and TA and SOL EMG. SOL and TA MEPs were depressed, whereas TMS-elicited suppression of SOL EMG and coherence were increased after training. Decreased excitability of corticospinal neurons due to increased intracortical inhibition seems a likely explanation of these observations. Our results indicate that the depression in H-reflex observed during a cocontraction task can be trained and that repeated performance of tasks involving cocontraction may lead to prolonged changes in reflex and corticospinal excitability.

scholarly journals Specific modulation of corticomuscular coherence during submaximal voluntary isometric, shortening and lengthening contractions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dorian Glories ◽  
Mathias Soulhol ◽  
David Amarantini ◽  
Julien Duclay
Keyword(s):  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Beta Band ◽  
Lengthening Contractions ◽  
Time Frequency ◽  
Corticomuscular Coherence ◽  
Emg Signal ◽  
Voluntary Contractions ◽  
Spinal Excitability

AbstractDuring voluntary contractions, corticomuscular coherence (CMC) is thought to reflect a mutual interaction between cortical and muscle oscillatory activities, respectively measured by electroencephalography (EEG) and electromyography (EMG). However, it remains unclear whether CMC modulation would depend on the contribution of neural mechanisms acting at the spinal level. To this purpose, modulations of CMC were compared during submaximal isometric, shortening and lengthening contractions of the soleus (SOL) and the medial gastrocnemius (MG) with a concurrent analysis of changes in spinal excitability that may be reduced during lengthening contractions. Submaximal contractions intensity was set at 50% of the maximal SOL EMG activity. CMC was computed in the time–frequency domain between the Cz EEG electrode signal and the unrectified SOL or MG EMG signal. Spinal excitability was quantified through normalized Hoffmann (H) reflex amplitude. The results indicate that beta-band CMC and normalized H-reflex were significantly lower in SOL during lengthening compared with isometric contractions, but were similar in MG for all three muscle contraction types. Collectively, these results highlight an effect of contraction type on beta-band CMC, although it may differ between agonist synergist muscles. These novel findings also provide new evidence that beta-band CMC modulation may involve spinal regulatory mechanisms.

Cortical control of presynaptic inhibition of Ia afferents in humans

1998 ◽  
Vol 119 (4) ◽  
pp. 415-426 ◽  
Author(s):  
S. Meunier ◽  
E. Pierrot-Deseilligny
Keyword(s):  
Presynaptic Inhibition ◽  
Cortical Control ◽  
Ia Afferents

Coordination between rib cage muscles and diaphragm during quiet breathing in humans

1984 ◽  
Vol 57 (3) ◽  
pp. 899-906 ◽  
Author(s):  
A. De Troyer ◽  
M. Estenne
Keyword(s):  
Tidal Volume ◽  
Marked Reduction ◽  
Emg Activity ◽  
Quiet Breathing ◽  
Rib Cage ◽  
Intercostal Muscles ◽  
Inspiratory Activity ◽  
Normal Humans ◽  
Volume Range

The pattern of activation of the scalenes and the parasternal intercostal muscles was studied in relation to the pattern of rib cage and abdominal motion during various respiratory maneuvers in the tidal volume range in five normal humans. Electromyograms (EMG) of the scalenes and parasternal intercostals were recorded with bipolar needle electrodes, and changes in abdominal and rib cage displacement were measured using linearized magnetometers. The scalenes and parasternal intercostals were always active during quiet breathing, and their pattern of activation was identical; in both muscles the EMG activity usually started together with the beginning of inspiration, increased in intensity as inspiration proceeded, and persisted into the early part of expiration. In addition, like the parasternal activity the scalene inspiratory activity persisted until the tidal volume was trivial, increased during tidal inspirations performed with the rib cage alone, and was nearly abolished during diaphragmatic isovolume maneuvers. However, attempts to perform tidal inspiration with the diaphragm alone, while causing an increase in parasternal EMG activity, were associated with a marked reduction or a suppression of scalene EMG activity and a reduced substantially distorted rib cage expansion. In particular, the upper rib cage was then moving paradoxically.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Early postnatal development of GABAergic presynaptic inhibition of Ia proprioceptive afferent connections in mouse spinal cord

2013 ◽  
Vol 109 (8) ◽  
pp. 2118-2128 ◽  
Author(s):  
Patrick M. Sonner ◽  
David R. Ladle
Keyword(s):  
Spinal Cord ◽  
Postnatal Development ◽  
Presynaptic Inhibition ◽  
Dorsal Root ◽  
Reciprocal Inhibition ◽  
Afferent Feedback ◽  
Early Postnatal Development ◽  
Ia Afferent ◽  
Ia Afferents ◽  
Stimulation Of

Sensory feedback is critical for normal locomotion and adaptation to external perturbations during movement. Feedback provided by group Ia afferents influences motor output both directly through monosynaptic connections and indirectly through spinal interneuronal circuits. For example, the circuit responsible for reciprocal inhibition, which acts to prevent co-contraction of antagonist flexor and extensor muscles, is driven by Ia afferent feedback. Additionally, circuits mediating presynaptic inhibition can limit Ia afferent synaptic transmission onto central neuronal targets in a task-specific manner. These circuits can also be activated by stimulation of proprioceptive afferents. Rodent locomotion rapidly matures during postnatal development; therefore, we assayed the functional status of reciprocal and presynaptic inhibitory circuits of mice at birth and compared responses with observations made after 1 wk of postnatal development. Using extracellular physiological techniques from isolated and hemisected spinal cord preparations, we demonstrate that Ia afferent-evoked reciprocal inhibition is as effective at blocking antagonist motor neuron activation at birth as at 1 wk postnatally. In contrast, at birth conditioning stimulation of muscle nerve afferents failed to evoke presynaptic inhibition sufficient to block functional transmission at synapses between Ia afferents and motor neurons, even though dorsal root potentials could be evoked by stimulating the neighboring dorsal root. Presynaptic inhibition at this synapse was readily observed, however, at the end of the first postnatal week. These results indicate Ia afferent feedback from the periphery to central spinal circuits is only weakly gated at birth, which may provide enhanced sensitivity to peripheral feedback during early postnatal experiences.

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