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Monosynaptic reflex

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https://www.readbyqxmd.com/read/28638331/monosynaptic-stretch-reflex-fails-to-explain-the-initial-postural-response-to-sudden-lateral-perturbations
#1
Andreas Mühlbeier, Christian Puta, Kim J Boström, Heiko Wagner
Postural reflexes are essential for locomotion and postural stability, and may play an important role in the etiology of chronic back pain. It has recently been theoretically predicted, and with the help of unilateral perturbations of the trunk experimentally confirmed that the sensorimotor control must lower the reflex amplitude for increasing reflex delays to maintain spinal stability. The underlying neuromuscular mechanism for the compensation of postural perturbations, however, is not yet fully understood...
2017: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/28623664/mechanosensory-neurons-control-the-timing-of-spinal-microcircuit-selection-during-locomotion
#2
Claire Wyart, Steven Knafo, Kevin Fidelin, Andrew Prendergast, Po-En Brian Tseng, Alexandre Parrin, Charles William Dickey, Urs Lucas Böhm, Sophie Nunes FIgueiredo, Olivier Thouvenin, Hugues Pascal-Moussellard
Despite numerous physiological studies about reflexes in the spinal cord, the contribution of mechanosensory feedback to active locomotion and the nature of underlying spinal circuits remains elusive. Here we investigate how mechanosensory feedback shapes active locomotion in a genetic model organism exhibiting simple locomotion-the zebrafish larva. We show that mechanosensory feedback enhances the recruitment of motor pools during active locomotion. Furthermore, we demonstrate that inputs from mechanosensory neurons increase locomotor speed by prolonging fast swimming at the expense of slow swimming during stereotyped acoustic escape responses...
June 17, 2017: ELife
https://www.readbyqxmd.com/read/28576940/descending-systems-direct-development-of-key-spinal-motor-circuits-abbreviated-title-postnatal-development-of-spinal-motor-circuits
#3
Calvin C Smith, Julian F R Paton, Samit Chakrabarty, Ronaldo M Ichiyama
The formation of mature spinal motor circuits is dependent on both activity dependent and independent mechanisms during postnatal development. During this time, reorganisation and refinement of spinal sensorimotor circuits occurs as supraspinal projections are integrated. However, specific features of postnatal spinal circuit development remain poorly understood. This study provides the first detailed characterisation of rat spinal sensorimotor circuit development in the presence and absence of descending systems...
June 2, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28570549/non-invasive-assessment-of-changes-in-corticomotoneuronal-transmission-in-humans
#4
Wolfgang Taube, Christian Leukel, Jens Bo Nielsen, Jesper Lundbye-Jensen
The corticospinal pathway is the major pathway connecting the brain with the muscles and is therefore highly relevant for movement control and motor learning. There exists a number of noninvasive electrophysiological methods investigating the excitability and plasticity of this pathway. However, most methods are based on quantification of compound potentials and neglect that the corticospinal pathway consists of many different connections that are more or less direct. Here, we present a method that allows testing excitability of different fractions of the corticospinal transmission...
May 24, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28543879/vglut1-synapses-and-p-boutons-on-regenerating-motoneurons-after-nerve-crush
#5
Adam J Schultz, Travis M Rotterman, Anirudh Dwarakanath, Francisco J Alvarez
Stretch-sensitive Ia afferent monosynaptic connections with motoneurons form the stretch reflex circuit. After nerve transection, Ia afferent synapses and stretch reflexes are permanently lost, even after regeneration and efficient re-innervation of muscle by motor and sensory afferents is completed in the periphery. This loss greatly affects full recovery of motor function. However, after nerve crush, reflex muscle forces during stretch do recover after muscle reinnervation and reportedly exceed 140% baseline values...
May 20, 2017: Journal of Comparative Neurology
https://www.readbyqxmd.com/read/28405011/plasticity-within-excitatory-and-inhibitory-pathways-of-the-vestibulo-spinal-circuitry-guides-changes-in-motor-performance
#6
Diana E Mitchell, Charles C Della Santina, Kathleen E Cullen
Investigations of behaviors with well-characterized circuitry are required to understand how the brain learns new motor skills and ensures existing behaviors remain appropriately calibrated over time. Accordingly, here we recorded from neurons within different sites of the vestibulo-spinal circuitry of behaving macaque monkeys during temporally precise activation of vestibular afferents. Behaviorally relevant patterns of vestibular nerve activation generated a rapid and substantial decrease in the monosynaptic responses recorded at the first central stage of processing from neurons receiving direct input from vestibular afferents within minutes, as well as a decrease in the compensatory reflex response that lasted up to 8 hours...
April 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28380320/reappraisal-of-the-f-m-amplitude-ratio-in-carpal-tunnel-syndrome
#7
F Ginanneschi, M Mondelli, A Aretini, Alessandro Rossi
The F-wave/M-wave amplitude (F/M-amp) ratio has been shown to be increased in peripheral neuropathies, provided the maximum M-wave is relatively preserved. Reduced M-wave amplitudes and central facilitation of antidromically-induced reactivation of the anterior horn cells' axon hillocks (F-wave) are believed to contribute to higher F/M-amp ratios. The present study was undertaken to re-evaluate mechanisms responsible for higher F/M-amp ratios in carpal tunnel syndrome (CTS). We enrolled 232 cases affected by CTS and 108 controls...
January 2017: Functional Neurology
https://www.readbyqxmd.com/read/28244163/chemogenetic-enhancement-of-functional-recovery-after-a-sciatic-nerve-injury
#8
Poonam B Jaiswal, Arthur W English
Designer receptors exclusively activated by designer drugs (DREADDs) are chemogenetic tools used to modulate neuronal excitability. We hypothesized that activation of excitatory (Gq) DREADD by its designer ligand, clozapine-N-oxide (CNO), would increase the excitability of neurons whose axons have been transected following peripheral nerve injury, and that this increase will lead to an enhanced functional recovery. The lateral gastrocnemius (LG) muscle of adult female Lewis rats was injected unilaterally with AAV9- hsyn- hM3Dq-mCherry (7...
May 2017: European Journal of Neuroscience
https://www.readbyqxmd.com/read/27891626/does-trans-spinal-and-local-dc-polarization-affect-presynaptic-inhibition-and-post-activation-depression
#9
D Kaczmarek, J Ristikankare, E Jankowska
KEY POINTS: Trans-spinal polarization was recently introduced as a means to improve deficient spinal functions. However, only a few attempts have been made to examine the mechanisms underlying DC actions. We have now examined the effects of DC on two spinal modulatory systems, presynaptic inhibition and post-activation depression, considering whether they might weaken exaggerated spinal reflexes and enhance excessively weakened ones. Direct current effects were evoked by using local intraspinal DC application (0...
March 1, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/27880894/requirement-for-dicer-in-maintenance-of-monosynaptic-sensory-motor-circuits-in-the-spinal-cord
#10
Fumiyasu Imai, Xiaoting Chen, Matthew T Weirauch, Yutaka Yoshida
In contrast to our knowledge of mechanisms governing circuit formation, our understanding of how neural circuits are maintained is limited. Here, we show that Dicer, an RNaseIII protein required for processing microRNAs (miRNAs), is essential for maintenance of the spinal monosynaptic stretch reflex circuit in which group Ia proprioceptive sensory neurons form direct connections with motor neurons. In postnatal mice lacking Dicer in proprioceptor sensory neurons, there are no obvious defects in specificity or formation of monosynaptic sensory-motor connections...
November 22, 2016: Cell Reports
https://www.readbyqxmd.com/read/27879195/pharmacokinetic-comparison-and-bioequivalence-evaluation-of-two-10-mg-baclofen-formulations-in-healthy-male-subjects%C3%A2
#11
Sumin Yoon, SeungHwan Lee, Kyung-Sang Yu, Sung-Vin Yim, Bo-Hyung Kim
BACKGROUNDS: Baclofen is used as a skeletal muscle relaxant for multiple sclerosis patients. It depresses the transmission of monosynaptic and polysynaptic reflex by stimulating GABA<sub>β</sub> (gamma-aminobutyric acid) receptors. OBJECTIVES: The aim of this study was to compare the pharmacokinetic characteristics of two 10-mg baclofen formulations and to assess bioequivalence. METHODS: A randomized, single-dose, two-period, two-sequence crossover study was conducted in healthy male subjects...
February 2017: International Journal of Clinical Pharmacology and Therapeutics
https://www.readbyqxmd.com/read/27553707/monosynaptic-facilitation-of-group-i-afferents-between-brachioradialis-and-extensor-carpi-radialis-in-humans
#12
Katsuhiro Shinozaki, Mitsuhiro Nito, Shinji Kobayashi, Masahiro Hayashi, Takuji Miyasaka, Wataru Hashizume, Masaomi Shindo, Akira Naito
Spinal reflex arcs mediated by low-threshold (group I) afferents from muscle spindles and Golgi tendon organs modulate motoneuron excitabilities to coordinate smooth movements. In this study, the reflex arcs between the brachioradialis (BR) and extensor carpi radialis muscles (ECR) were examined in nine healthy human subjects using a post-stimulus time-histogram method. Electrical conditioning stimuli (ES) to the radial nerve branches innervating BR (BR nerve) and ECR (ECR nerve) with the intensity just below the motor threshold were delivered and firings of the ECR and BR motor units were recorded in 6 and 7 of the nine subjects, respectively...
January 2017: Neuroscience Research
https://www.readbyqxmd.com/read/27552219/electrical-stimulation-of-low-threshold-proprioceptive-fibers-in-the-adult-rat-increases-density-of-glutamatergic-and-cholinergic-terminals-on-ankle-extensor-%C3%AE-motoneurons
#13
Olga Gajewska-Woźniak, Kamil Grycz, Julita Czarkowska-Bauch, Małgorzata Skup
The effects of stimulation of low-threshold proprioceptive afferents in the tibial nerve on two types of excitatory inputs to α-motoneurons were tested. The first input is formed by glutamatergic Ia sensory afferents contacting monosynaptically α-motoneurons. The second one is the cholinergic input originating from V0c-interneurons, located in lamina X of the spinal cord, modulating activity of α-motoneurons via C-terminals. Our aim was to clarify whether enhancement of signaling to ankle extensor α-motoneurons, via direct electrical stimulation addressed predominantly to low-threshold proprioceptive fibers in the tibial nerve of awake rats, will affect Ia glutamatergic and cholinergic innervation of α-motoneurons of lateral gastrocnemius (LG)...
2016: PloS One
https://www.readbyqxmd.com/read/27499737/short-term-plasticity-in-a-monosynaptic-reflex-pathway-to-forearm-muscles-after-continuous-robot-assisted-passive-stepping
#14
Tsuyoshi Nakajima, Kiyotaka Kamibayashi, Taku Kitamura, Tomoyoshi Komiyama, E Paul Zehr, Kimitaka Nakazawa
Both active and passive rhythmic limb movements reduce the amplitude of spinal cord Hoffmann (H-) reflexes in muscles of moving and distant limbs. This could have clinical utility in remote modulation of the pathologically hyperactive reflexes found in spasticity after stroke or spinal cord injury. However, such clinical translation is currently hampered by a lack of critical information regarding the minimum or effective duration of passive movement needed for modulating spinal cord excitability. We therefore investigated the H-reflex modulation in the flexor carpi radialis (FCR) muscle during and after various durations (5, 10, 15, and 30 min) of passive stepping in 11 neurologically normal subjects...
2016: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/27466130/upslope-treadmill-exercise-enhances-motor-axon-regeneration-but-not-functional-recovery-following-peripheral-nerve-injury
#15
Jill Cannoy, Sam Crowley, Allen Jarratt, Kelly LeFevere Werts, Krista Osborne, Sohee Park, Arthur W English
Following peripheral nerve injury, moderate daily exercise conducted on a level treadmill results in enhanced axon regeneration and modest improvements in functional recovery. If the exercise is conducted on an upwardly inclined treadmill, even more motor axons regenerate successfully and reinnervate muscle targets. Whether this increased motor axon regeneration also results in greater improvement in functional recovery from sciatic nerve injury was studied. Axon regeneration and muscle reinnervation were studied in Lewis rats over an 11 wk postinjury period using stimulus evoked electromyographic (EMG) responses in the soleus muscle of awake animals...
September 1, 2016: Journal of Neurophysiology
https://www.readbyqxmd.com/read/27422350/vastus-medialis-hoffmann-reflex-excitability-is-associated-with-pain-level-self-reported-function-and-chronicity-in-women-with-patellofemoral-pain
#16
Danilo de Oliveira Silva, Fernando Henrique Magalhães, Nathálie Clara Faria, Deisi Ferrari, Marcella Ferraz Pazzinatto, Evangelos Pappas, Fábio Mícolis de Azevedo
OBJECTIVE: To determine the association between the amplitude of vastus medialis (VM) Hoffmann reflex (H-reflex) and pain level, self-reported physical function, and chronicity of pain in women with patellofemoral pain (PFP). DESIGN: Cross-sectional study. SETTING: Laboratory of biomechanics and motor control. PARTICIPANTS: Women diagnosed with PFP (N=15) aged 18 to 35 years. INTERVENTIONS: Not applicable...
January 2017: Archives of Physical Medicine and Rehabilitation
https://www.readbyqxmd.com/read/27318009/the-effect-of-voluntary-modulation-of-the-sensory-motor-rhythm-during-different-mental-tasks-on-h-reflex
#17
M Jarjees, A Vučković
OBJECTIVES: The aim of this study was to explore the possibility of the short-term modulation of the soleus H reflex through self-induced modulation of the sensory-motor rhythm (SMR) as measured by electroencephalography (EEG) at Cz. METHODS: Sixteen healthy participants took part in one session of neuromodulation. Motor imagery and mental math were strategies for decreasing SMR, while neurofeedback was used to increase SMR. H reflex of the soleus muscle was elicited by stimulating tibial nerve when SMR reached a pre-defined threshold and was averaged over 5 trials...
August 2016: International Journal of Psychophysiology
https://www.readbyqxmd.com/read/27225950/elpbn-neurons-regulate-rvlm-activity-through-elpbn-rvlm-projections-during-activation-of-cardiac-sympathetic-afferent-nerves
#18
Zhi-Ling Guo, John C Longhurst, Stephanie C Tjen-A-Looi, Liang-Wu Fu
The external lateral parabrachial nucleus (elPBN) within the pons and rostral ventrolateral medulla (rVLM) contributes to central processing of excitatory cardiovascular reflexes during stimulation of cardiac sympathetic afferent nerves (CSAN). However, the importance of elPBN cardiovascular neurons in regulation of rVLM activity during CSAN activation remains unclear. We hypothesized that CSAN stimulation excites the elPBN cardiovascular neurons and, in turn, increases rVLM activity through elPBN-rVLM projections...
August 1, 2016: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/27225763/synapse-formation-in-monosynaptic-sensory-motor-connections-is-regulated-by-presynaptic-rho-gtpase-cdc42
#19
Fumiyasu Imai, David R Ladle, Jennifer R Leslie, Xin Duan, Tilat A Rizvi, Georgianne M Ciraolo, Yi Zheng, Yutaka Yoshida
UNLABELLED: Spinal reflex circuit development requires the precise regulation of axon trajectories, synaptic specificity, and synapse formation. Of these three crucial steps, the molecular mechanisms underlying synapse formation between group Ia proprioceptive sensory neurons and motor neurons is the least understood. Here, we show that the Rho GTPase Cdc42 controls synapse formation in monosynaptic sensory-motor connections in presynaptic, but not postsynaptic, neurons. In mice lacking Cdc42 in presynaptic sensory neurons, proprioceptive sensory axons appropriately reach the ventral spinal cord, but significantly fewer synapses are formed with motor neurons compared with wild-type mice...
May 25, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/27208411/ascending-mechanisms-of-stress-integration-implications-for-brainstem-regulation-of-neuroendocrine-and-behavioral-stress-responses
#20
REVIEW
Brent Myers, Jessie R Scheimann, Ana Franco-Villanueva, James P Herman
In response to stress, defined as a real or perceived threat to homeostasis or well-being, brain systems initiate divergent physiological and behavioral processes that mobilize energy and promote adaptation. The brainstem contains multiple nuclei that engage in autonomic control and reflexive responses to systemic stressors. However, brainstem nuclei also play an important role in neuroendocrine responses to psychogenic stressors mediated by the hypothalamic-pituitary-adrenocortical axis. Further, these nuclei integrate neuroendocrine responses with stress-related behaviors, significantly impacting mood and anxiety...
March 2017: Neuroscience and Biobehavioral Reviews
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