Search results for "Muscle spindle"
showing 8 items of 18 documents
Effects of effort and EMG levels on short-latency stretch reflex modulation after varying background muscle contractions.
2005
It is known that the short-latency stretch reflex (SLSR) is modulated by the background muscle activity when it is elicited at matched torque levels. This study was designed to examine the effects of muscle contraction types before a stretch perturbation on SLSR in the human soleus muscle (SOL) when SLSR was elicited at the same levels of effort and at matched electromyographic (EMG) activity levels. A mechanical stretch perturbation was applied to the calf muscles when the ankle joint reached a ninety degree tibio-tarsal joint angle after the muscles performed an isometric (pre-ISO), shortening (pre-SHO) and lengthening contraction (pre-LEN). Subjects were seated on an ankle ergometer chai…
Attention directed to proprioceptive stimulation alters its cortical processing in the primary sensorimotor cortex.
2021
Funding Information: This study has been supported by the Academy of Finland ”Brain changes across the life‐span” profiling funding to University of Jyväskylä (grant #311877). HP was supported by Academy of Finland (grants #296240, #326988, #307250 and #327288) to HP and Jane and Aatos Erkko Foundation (grant #602.274). Publisher Copyright: © 2021 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd. Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Movement-evoked fields to passive movements and corticokinematic coherence between limb kinematics and magnetoencephalographic signals can both be used to …
Bilateral reciprocal organisation in man: focus on IA interneurone
1994
The H reflex of flexor carpi radialis and radial-induced reciprocal inhibition were recorded in normal subjects during conditioning stimulation of the contralateral median or radial nerves. It was found that stimulation of the contralateral median nerve enhanced the degree of reciprocal inhibition exerted by the radial nerve on the median nerve, while contralateral radial nerve stimulation reduced the reciprocal inhibition exerted by the extensor on the flexor. In two subjects in which a pure extensor H reflex was recorded specular features were observed following contralateral median and radial stimulation. These findings are considered to be the electrophysiological manifestation of contr…
The Stretch-Shortening Cycle
2006
Neuromuscular fatigue has traditionally been examined using isolated forms of either isometric, concentric or eccentric actions. However, none of these actions are naturally occurring in human (or animal) ground locomotion. The basic muscle function is defined as the stretch-shortening cycle (SSC), where the preactivated muscle is first stretched (eccentric action) and then followed by the shortening (concentric) action. As the SSC taxes the skeletal muscles very strongly mechanically, its influence on the reflex activation becomes apparent and very different from the isolated forms of muscle actions mentioned above. The ground contact phases of running, jumping and hopping etc. are example…
The fine structure of de-and reinnervated muscle spindles
1974
Reinnervated muscle spindles in lower lumbrical muscles of rats studied 17 days to 24 months after crushing the sciatic nerve showed a series of alterations which have not been analysed, thus far, by electron microscopy. There was a striking increase of the number of intrafusal muscle fibers seen in approximately 20% of reinnervated spindles. These spindles showed 5–11 intrafusal muscle fibers whereas normal spindles usually contained 3–4 fibers only.
Two different pathogenic mechanisms, dying-back axonal neuropathy and pancreatic senescence, are present in the YG8R mouse model of Friedreich ataxia
2016
Frataxin (FXN) deficiency causes Friedreich's ataxia (FRDA), a multisystem disorder with neurological and non-neurological symptoms. FRDA pathophysiology combines developmental and degenerative processes of dorsal root ganglia (DRG), sensory nerves, dorsal columns and other central nervous structures. A dying-back mechanism has been proposed to explain the peripheral neuropathy and neuropathology. In addition, affected individuals have non-neuronal symptoms such as diabetes mellitus or glucose intolerance. To go further in the understanding of the pathogenic mechanisms of neuropathy and diabetes associated with the disease, we have investigated the humanized mouse YG8R model of FRDA. By bio…
Erbb2 regulates neuromuscular synapse formation and is essential for muscle spindle development
2003
Neuregulins and their Erbb receptors have been implicated in neuromuscular synapse formation by regulating gene expression in subsynaptic nuclei. To analyze the function of Erbb2 in this process, we have inactivated the Erbb2 gene in developing muscle fibers by Cre/Lox-mediated gene ablation. Neuromuscular synapses form in the mutant mice, but the synapses are less efficient and contain reduced levels of acetylcholine receptors. Surprisingly, the mutant mice also show proprioceptive defects caused by abnormal muscle spindle development. Sensory Ia afferent neurons establish initial contact with Erbb2-deficient myotubes. However, functional spindles never develop. Taken together, our data su…
Proprioceptive response strength in the primary sensorimotor cortex is invariant to the range of finger movement
2023
Available online 13 February 2023 Proprioception is the sense of body position and movement that relies on afference from the proprioceptors in muscles and joints. Proprioceptive responses in the primary sensorimotor (SM1) cortex can be elicited by stim- ulating the proprioceptors using evoked (passive) limb movements. In magnetoencephalography (MEG), propri- oceptive processing can be quantified by recording the movement evoked fields (MEFs) and movement-induced beta power modulations or by computing corticokinematic coherence (CKC) between the limb kinematics and cortical activity. We examined whether cortical proprioceptive processing quantified with MEF peak strength, relative beta supp…