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BioRxiv : the Preprint Server For... May 2023Muscle spindles relay vital mechanosensory information for movement and posture, but muscle spindle feedback is coupled to skeletal motion by a compliant tendon. Little...
Muscle spindles relay vital mechanosensory information for movement and posture, but muscle spindle feedback is coupled to skeletal motion by a compliant tendon. Little is known about the effects of tendon compliance on muscle spindle feedback during movement, and the complex firing of muscle spindles make these effects difficult to predict. Our goal was to investigate changes in muscle spindle firing using added series elastic elements (SEEs) to mimic a more compliant tendon, and to characterize the accompanying changes in firing with respect to muscle-tendon unit (MTU) and muscle fascicle displacements (recorded via sonomicrometry). Sinusoidal, ramp-hold-release, and triangular stretches were analyzed to examine potential changes in muscle spindle instantaneous firing rates (IFRs) in locomotor- and perturbation-like stretches as well as history dependence. Added SEEs effectively reduced overall MTU stiffness and generally reduced muscle spindle firing rates, but the effect differed across stretch types. During sinusoidal stretches, peak firing rates were reduced and IFR was strongly correlated with fascicle velocity. During ramp stretches, SEEs reduced the dynamic and static responses of the spindle during lengthening but had no effect on initial bursts at the onset of stretch. Notably, IFR was negatively related to fascicle displacement during the hold phase. During triangular stretches, SEEs reduced the mean IFR during the first and second stretches, affecting the history dependence of mean IFR. Overall, these results demonstrate that tendon compliance may attenuate muscle spindle feedback during movement, but these changes cannot be fully explained by reduced muscle fascicle length and velocity.
PubMed: 37215007
DOI: 10.1101/2023.05.08.539853 -
Advances in Experimental Medicine and... 2019The purpose of this study was to characterize the effects of taurine (supplementation and acute injection) on the stretch reflex in the ankle muscles, and in particular...
The purpose of this study was to characterize the effects of taurine (supplementation and acute injection) on the stretch reflex in the ankle muscles, and in particular to compare the effects of chronic taurine supplementation versus acute injection on the muscle tension, amplitude of electromyogram and velocity of muscle response. Stretch reflex responses were evoked using a specialized stretching device designed for mice. The triceps surae muscle of an awake mouse was stretched at various speeds ranging from 500 to 500,000° per second. A transducer recorded the muscle resistance at each velocity and the corresponding EMG. We found that at each velocity, the taurine-fed mice generated more tension and exhibited a higher EMG response. Acute taurine injection did not affect the tension but significantly reduced the EMG. To evaluate if the enhances response was due to neuronal excitability of changes in the passive properties of the muscles, we anesthetize the mice to eliminate the central component of the reflex. Under these conditions, taurine-fed mice still exhibited an enhanced stretch reflex response. We have previously shown that taurine-fed mice have reduced expression of GABA receptors and other biochemical changes in the GABAergic system that are consistent with hyper-excitability. GABA receptor is a major component of the inhibitory (GABAergic) system and its reduced expression probably contributes to the enhanced stretch reflex in these mice through biochemical mechanisms that involve alterations not only at the spinal level but also at the cortical level.
Topics: Animals; Electromyography; Mice; Muscle, Skeletal; Receptors, GABA; Reflex, Stretch; Taurine
PubMed: 31468414
DOI: 10.1007/978-981-13-8023-5_34 -
Philosophical Transactions of the Royal... Sep 2018Muscle spindles and Golgi tendon organs (GTOs) are two types of sensory receptors that respond to changes in length or tension of skeletal muscles. These mechanosensors... (Review)
Review
Muscle spindles and Golgi tendon organs (GTOs) are two types of sensory receptors that respond to changes in length or tension of skeletal muscles. These mechanosensors have long been known to participate in both proprioception and stretch reflex. Here, we present recent findings implicating these organs in maintenance of spine alignment as well as in realignment of fractured bones. These discoveries have been made in several mouse lines lacking functional mechanosensors in part or completely. In both studies, the absence of functional spindles and GTOs produced a more severe phenotype than that of spindles alone. Interestingly, the spinal curve phenotype, which appeared during peripubertal development, bears resemblance to the human condition adolescent idiopathic scoliosis. This similarity may contribute to the study of the disease by offering both an animal model and a clue as to its aetiology. Moreover, it raises the possibility that impaired proprioceptive signalling may be involved in the aetiology of other conditions. Overall, these new findings expand considerably the scope of involvement of proprioception in musculoskeletal development and function.This article is part of the Theo Murphy meeting issue 'Mechanics of development'.
Topics: Animals; Disease Models, Animal; Humans; Mechanoreceptors; Mice; Muscle Spindles; Muscle, Skeletal; Proprioception; Scoliosis; Spine
PubMed: 30249776
DOI: 10.1098/rstb.2017.0327 -
Skeletal Muscle Mar 2019Striated muscles express an array of sarcomeric myosin motors that are tuned to accomplish specific tasks. Each myosin isoform found in muscle fibers confers unique... (Review)
Review
Striated muscles express an array of sarcomeric myosin motors that are tuned to accomplish specific tasks. Each myosin isoform found in muscle fibers confers unique contractile properties to the fiber in order to meet the demands of the muscle. The sarcomeric myosin heavy chain (MYH) genes expressed in the major cardiac and skeletal muscles have been studied for decades. However, three ancient myosins, MYH7b, MYH15, and MYH16, remained uncharacterized due to their unique expression patterns in common mammalian model organisms and due to their relatively recent discovery in these genomes. This article reviews the literature surrounding these three ancient sarcomeric myosins and the specialized muscles in which they are expressed. Further study of these ancient myosins and how they contribute to the functions of the specialized muscles may provide novel insight into the history of striated muscle evolution.
Topics: Animals; Evolution, Molecular; Humans; Muscle, Skeletal; Myocytes, Cardiac; Myosin Heavy Chains; Protein Isoforms
PubMed: 30836986
DOI: 10.1186/s13395-019-0192-3 -
Experimental Physiology Jan 2024Proprioceptors are non-nociceptive low-threshold mechanoreceptors. However, recent studies have shown that proprioceptors are acid-sensitive and express a variety of... (Review)
Review
Proprioceptors are non-nociceptive low-threshold mechanoreceptors. However, recent studies have shown that proprioceptors are acid-sensitive and express a variety of proton-sensing ion channels and receptors. Accordingly, although proprioceptors are commonly known as mechanosensing neurons that monitor muscle contraction status and body position, they may have a role in the development of pain associated with tissue acidosis. In clinical practice, proprioception training is beneficial for pain relief. Here we summarize the current evidence to sketch a different role of proprioceptors in 'non-nociceptive pain' with a focus on their acid-sensing properties.
Topics: Humans; Musculoskeletal Pain; Acid Sensing Ion Channels; Sensory Receptor Cells; Mechanoreceptors; Proprioception
PubMed: 37417654
DOI: 10.1113/EP090989 -
Journal of the Peripheral Nervous... Mar 2021The foot-sole cutaneous receptors (section 2), their function in stance control (sway minimisation, exploratory role) (2.1), and the modulation of their effects by gait... (Review)
Review
The foot-sole cutaneous receptors (section 2), their function in stance control (sway minimisation, exploratory role) (2.1), and the modulation of their effects by gait pattern and intended behaviour (2.2) are reviewed. Experimental manipulations (anaesthesia, temperature) (2.3 and 2.4) have shown that information from foot sole has widespread influence on balance. Foot-sole stimulation (2.5) appears to be a promising approach for rehabilitation. Proprioceptive information (3) has a pre-eminent role in balance and gait. Reflex responses to balance perturbations are produced by both leg and foot muscle stretch (3.1) and show complex interactions with skin input at both spinal and supra-spinal levels (3.2), where sensory feedback is modulated by posture, locomotion and vision. Other muscles, notably of neck and trunk, contribute to kinaesthesia and sense of orientation in space (3.3). The effects of age-related decline of afferent input are variable under different foot-contact and visual conditions (3.4). Muscle force diminishes with age and sarcopenia, affecting intrinsic foot muscles relaying relevant feedback (3.5). In neuropathy (4), reduction in cutaneous sensation accompanies the diminished density of viable receptors (4.1). Loss of foot-sole input goes along with large-fibre dysfunction in intrinsic foot muscles. Diabetic patients have an elevated risk of falling, and vision and vestibular compensation strategies may be inadequate (4.2). From Charcot-Marie-Tooth 1A disease (4.3) we have become aware of the role of spindle group II fibres and of the anatomical feet conditions in balance control. Lastly (5) we touch on the effects of nerve stimulation onto cortical and spinal excitability, which may participate in plasticity processes, and on exercise interventions to reduce the impact of neuropathy.
Topics: Foot; Gait; Humans; Muscle, Skeletal; Peripheral Nervous System Diseases; Proprioception; Sensory Receptor Cells; Skin Physiological Phenomena; Touch Perception
PubMed: 33426723
DOI: 10.1111/jns.12429 -
Frontiers in Neurology 2022High frequency oscillations (HFO; ripples = 80-200, fast ripples 200-500 Hz) are promising epileptic biomarkers in patients with epilepsy. However, especially in...
RATIONALE
High frequency oscillations (HFO; ripples = 80-200, fast ripples 200-500 Hz) are promising epileptic biomarkers in patients with epilepsy. However, especially in temporal epilepsies differentiation of epileptic and physiological HFO activity still remains a challenge. Physiological sleep-spindle-ripple formations are known to play a role in slow-wave-sleep memory consolidation. This study aimed to find out if higher rates of mesial-temporal spindle-ripples correlate with good memory performance in epilepsy patients and if surgical removal of spindle-ripple-generating brain tissue correlates with a decline in memory performance. In contrast, we hypothesized that higher rates of overall ripples or ripples associated with interictal epileptic spikes correlate with poor memory performance.
METHODS
Patients with epilepsy implanted with electrodes in mesial-temporal structures, neuropsychological memory testing and subsequent epilepsy surgery were included. Ripples and epileptic spikes were automatically detected in intracranial EEG and sleep-spindles in scalp EEG. The coupling of ripples to spindles was automatically analyzed. Mesial-temporal spindle-ripple rates in the speech-dominant-hemisphere (left in all patients) were correlated with verbal memory test results, whereas ripple rates in the non-speech-dominant hemisphere were correlated with non-verbal memory test performance, using Spearman correlation).
RESULTS
Intracranial EEG and memory test results from 25 patients could be included. All ripple rates were significantly higher in seizure onset zone channels ( < 0.001). Patients with pre-surgical verbal memory impairment had significantly higher overall ripple rates in left mesial-temporal channels than patients with intact verbal memory (Mann-Whitney-U-Test: = 0.039). Spearman correlations showed highly significant negative correlations of the pre-surgical verbal memory performance with left mesial-temporal spike associated ripples (r = -0.458; = 0.007) and overall ripples (r = -0.475; = 0.006). All three ripple types in right-sided mesial-temporal channels did not correlate with pre-surgical nonverbal memory. No correlation for the difference between post- and pre-surgical memory and pre-surgical spindle-ripple rates was seen in patients with left-sided temporal or mesial-temporal surgery.
DISCUSSION
This study fails to establish a clear link between memory performance and spindle ripples. This highly suggests that spindle-ripples are only a small portion of physiological ripples contributing to memory performance. More importantly, this study indicates that spindle-ripples do not necessarily compromise the predictive value of ripples in patients with temporal epilepsy. The majority of ripples were clearly linked to areas with poor memory function.
PubMed: 35720106
DOI: 10.3389/fneur.2022.876024 -
Journal of Manipulative and... Jun 2021The purpose of this study was to characterize trunk muscle spindle responses immediately after high-velocity, low-amplitude spinal manipulation (HVLA-SM) delivered at...
OBJECTIVE
The purpose of this study was to characterize trunk muscle spindle responses immediately after high-velocity, low-amplitude spinal manipulation (HVLA-SM) delivered at various thrust magnitudes and thrust durations.
METHODS
Secondary analysis from multiple studies involving anesthetized adult cats (N = 70; 2.3-6.0 kg) receiving L6 HVLA-SM. Muscle spindle afferent recordings were obtained from L6 dorsal rootlets before, during, and immediately after HVLA-SM. L6 HVLA-SM was delivered posteriorly-to-anteriorly using a feedback motor with peak thrust magnitudes of 25%, 55%, and 85% of cat body weight (BW) and thrust durations of 25, 50, 75, 100, 150, 200, and 250 ms. Time to the first action potential and muscle spindle discharge frequency at 1 and 2 seconds post-HVLA-SM were determined.
RESULTS
A significant association between HVLA-SM thrust magnitude and immediate (≤2 s) muscle spindle response was found (P < .001). For non-control thrust magnitude, pairwise comparisons (25%, 55%, 85% BW), 55% BW thrust magnitude had the most consistent effect on immediate post-HVLA-SM discharge outcomes (false discovery rate < 0.05). No significant association was found between thrust duration and immediate post-HVLA-SM muscle spindle response (P > .05).
CONCLUSION
The present study found that HVLA-SM thrust magnitudes delivered at 55% BW were more likely to affect immediate (≤2 s) post-HVLA-SM muscle spindle response.
Topics: Animals; Cats; Manipulation, Spinal; Muscle Spindles; Muscle, Skeletal; Spinal Nerve Roots; Torso
PubMed: 34103172
DOI: 10.1016/j.jmpt.2021.03.004 -
Journal of Electromyography and... Dec 2018The objective of this study was to establish neural interactions between transspinal evoked potentials (TEPs) and muscle spindle group Ia afferents in healthy humans....
The objective of this study was to establish neural interactions between transspinal evoked potentials (TEPs) and muscle spindle group Ia afferents in healthy humans. Soleus H-reflexes were assessed following transspinal stimulation at conditioning-test (C-T) intervals that ranged from negative to positive 100 ms. TEPs were recorded from the right and left ankle/knee flexor and extensor muscles, and their amplitude was assessed following stimulation of soleus muscle spindle group Ia afferents at similar C-T intervals. Transspinal conditioning stimulation produced a short-latency, long-lasting soleus H-reflex depression. Excitation of muscle spindle group Ia afferents produced depression of ipsilateral ankle TEPs and medium-latency facilitation of the ipsilateral knee TEPs. At specific C-T intervals, the soleus H-reflex and ipsilateral ankle TEPs were summated based on their relative onset and duration. No changes were observed in the contralateral TEPs. These effects were exerted at both peripheral and spinal levels. Both transspinal and muscle spindle group Ia afferent stimulation produce long-lasting depression of the soleus H-reflex and TEPs, respectively. Transspinal stimulation may promote targeted neuromodulation and can be utilized in upper motoneuron lesions to normalize spinal reflex hyper-excitability and alter excitation thresholds of peripheral nerve axons.
Topics: Adult; Afferent Pathways; Evoked Potentials, Motor; H-Reflex; Humans; Male; Muscle Spindles; Muscle, Skeletal
PubMed: 30352388
DOI: 10.1016/j.jelekin.2018.10.005 -
Frontiers in Molecular Neuroscience 2022Neuromas form as a result of disorganized sensory axonal regeneration following nerve injury. Painful neuromas lead to poor quality of life for patients and place a... (Review)
Review
Neuromas form as a result of disorganized sensory axonal regeneration following nerve injury. Painful neuromas lead to poor quality of life for patients and place a burden on healthcare systems. Modern surgical interventions for neuromas entail guided regeneration of sensory nerve fibers into muscle tissue leading to muscle innervation and neuroma treatment or prevention. However, it is unclear how innervating denervated muscle targets prevents painful neuroma formation, as little is known about the fate of sensory fibers, and more specifically pain fiber, as they regenerate into muscle. Golgi tendon organs and muscle spindles have been proposed as possible receptor targets for the regenerating sensory fibers; however, these receptors are not typically innervated by pain fibers, as these free nerve endings do not synapse on receptors. The mechanisms by which pain fibers are signaled to cease regeneration therefore remain unknown. In this article, we review the physiology underlying nerve regeneration, the guiding molecular signals, and the target receptor specificity of regenerating sensory axons as it pertains to the development and prevention of painful neuroma formation while highlighting gaps in literature. We discuss management options for painful neuromas and the current supporting evidence for the various interventions.
PubMed: 35866159
DOI: 10.3389/fnmol.2022.859221