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https://www.readbyqxmd.com/read/29720934/reticulospinal-systems-for-tuning-motor-commands
#1
REVIEW
Robert M Brownstone, Jeremy W Chopek
The pontomedullary reticular formation (RF) is a key site responsible for integrating descending instructions to execute particular movements. The indiscrete nature of this region has led not only to some inconsistencies in nomenclature, but also to difficulties in understanding its role in the control of movement. In this review article, we first discuss nomenclature of the RF, and then examine the reticulospinal motor command system through evolution. These command neurons have direct monosynaptic connections with spinal interneurons and motoneurons...
2018: Frontiers in Neural Circuits
https://www.readbyqxmd.com/read/29719504/descending-inputs-to-spinal-circuits-facilitating-and-inhibiting-human-wrist-flexors
#2
Stefane A Aguiar, Stuart N Baker
Recently we reported in humans that electrical stimulation of the wrist extensor muscle extensor carpi radialis (ECR) could facilitate or suppress the H reflex elicited in flexor carpi radialis (FCR), for inter-stimulus intervals (ISIs) of 30 ms or 70 ms, respectively. The facilitation at 30 ms may be produced by both flexor afferents and extensor Ib afferents acting on a spinal circuit; the origin of the suppression at 70 ms is less certain. In this study, we investigated possible descending inputs to these systems...
2018: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/29715475/rhoa-activation-in-axotomy-induced-neuronal-death
#3
Guixin Zhang, Jianli Hu, William Rodemer, Shuxin Li, Michael E Selzer
After spinal cord injury (SCI) in mammals, severed axons fail to regenerate, due to both extrinsic inhibitory factors, e.g., the chondroitin sulfate proteoglycans (CSPGs) and myelin-associated growth inhibitors (MAIs), and a developmental loss of intrinsic growth capacity. The latter is suggested by findings in lamprey that the 18 pairs of individually identified reticulospinal neurons vary greatly in their ability to regenerate their axons through the same spinal cord environment. Moreover, those neurons that are poor regenerators undergo very delayed apoptosis, and express common molecular markers after SCI...
April 28, 2018: Experimental Neurology
https://www.readbyqxmd.com/read/29661988/the-effect-of-axon-resealing-on-retrograde-neuronal-death-after-spinal-cord-injury-in-lamprey
#4
Guixin Zhang, William Rodemer, Taemin Lee, Jianli Hu, Michael E Selzer
Failure of axon regeneration in the central nervous system (CNS) of mammals is due to both extrinsic inhibitory factors and to neuron-intrinsic factors. The importance of intrinsic factors is illustrated in the sea lamprey by the 18 pairs of large, individually identified reticulospinal (RS) neurons, whose axons are located in the same spinal cord tracts but vary greatly in their ability to regenerate after spinal cord transection (TX). The neurons that are bad regenerators also undergo very delayed apoptosis, signaled early by activation of caspases...
April 14, 2018: Brain Sciences
https://www.readbyqxmd.com/read/29653186/constraint-induced-movement-therapy-improves-efficacy-of-task-specific-training-after-severe-cortical-stroke-depending-on-the-ipsilesional-corticospinal-projections
#5
Naohiko Okabe, Naoyuki Himi, Emi Nakamura-Maruyama, Norito Hayashi, Issei Sakamoto, Kazuhiko Narita, Toru Hasegawa, Osamu Miyamoto
Descending spinal pathways (corticospinal, rubrospinal, and reticulospinal) are believed to contribute to functional recovery resulting from rehabilitative training after stroke. However, the contribution of each pathway remains unclear. In the current study, we investigated rehabilitation-induced functional recovery and remodelling of the descending spinal pathways after severe cortical stroke in rats followed by 3 weeks of various rehabilitation [constraint-induced movement therapy (CIMT), skilled forelimb reaching, rotarod, and treadmill exercise]...
April 10, 2018: Experimental Neurology
https://www.readbyqxmd.com/read/29649085/tract-specific-volume-loss-on-3t-mri-in-patients-with-cervical-spondylotic-myelopathy
#6
Benjamin S Hopkins, Kenneth A Weber, Michael Brendan Cloney, Monica Paliwal, Todd B Parrish, Zachary A Smith
STUDY DESIGN: Case-control. OBJECTIVE: The aim of this study was to understand the role of high-resolution magnetic resonance (MR) in identifying regional cord volume loss in cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA: Preliminary studies suggest that compression of the ventral region of the cord may contribute disproportionately to CSM symptomology; however, tract-specific data are lacking in the CSM population. The current study is the first to use 3T MR imaging (MRI) images of CSM patients to determine specific volume loss at the level of detail of individual descending white matter tracts...
April 11, 2018: Spine
https://www.readbyqxmd.com/read/29556028/cortico-reticulo-spinal-circuit-reorganization-enables-functional-recovery-after-severe-spinal-cord-contusion
#7
Leonie Asboth, Lucia Friedli, Janine Beauparlant, Cristina Martinez-Gonzalez, Selin Anil, Elodie Rey, Laetitia Baud, Galyna Pidpruzhnykova, Mark A Anderson, Polina Shkorbatova, Laura Batti, Stephane Pagès, Julie Kreider, Bernard L Schneider, Quentin Barraud, Gregoire Courtine
Severe spinal cord contusions interrupt nearly all brain projections to lumbar circuits producing leg movement. Failure of these projections to reorganize leads to permanent paralysis. Here we modeled these injuries in rodents. A severe contusion abolished all motor cortex projections below injury. However, the motor cortex immediately regained adaptive control over the paralyzed legs during electrochemical neuromodulation of lumbar circuits. Glutamatergic reticulospinal neurons with residual projections below the injury relayed the cortical command downstream...
April 2018: Nature Neuroscience
https://www.readbyqxmd.com/read/29457651/progressive-recruitment-of-contralesional-cortico-reticulospinal-pathways-drives-motor-impairment-post-stroke
#8
Jacob G McPherson, Albert Chen, Michael D Ellis, Jun Yao, C J Heckman, Julius P A Dewald
KEY POINTS: Activation of the shoulder abductor muscles in the arm opposite a unilateral brain injury causes involuntary increases in elbow, wrist and finger flexion in the same arm, a phenomenon referred to as the flexion synergy. It has been proposed that flexion synergy expression is related to reduced output from ipsilesional motor cortex and corticospinal pathways. In this human subjects study, we provide evidence that the magnitude of flexion synergy expression is instead related to a progressive, task-dependent recruitment of contralesional cortex...
April 1, 2018: Journal of Physiology
https://www.readbyqxmd.com/read/29423637/complementary-expression-of-calcium-binding-proteins-delineates-the-functional-organization-of-the-locomotor-network
#9
Eva M Berg, Maria Bertuzzi, Konstantinos Ampatzis
Neuronal networks in the spinal cord generate and execute all locomotor-related movements by transforming descending signals from supraspinal areas into appropriate rhythmic activity patterns. In these spinal networks, neurons that arise from the same progenitor domain share similar distribution patterns, neurotransmitter phenotypes, morphological and electrophysiological features. However, subgroups of them participate in different functionally distinct microcircuits to produce locomotion at different speeds and of different modalities...
February 8, 2018: Brain Structure & Function
https://www.readbyqxmd.com/read/29417172/axial-reflexes-are-present-in-older-subjects-and-may-contribute-to-balance-responses
#10
James G Colebatch, Sendhil Govender
We studied the response to axial taps (mini-perturbations) of a group of 13 healthy older subjects (mean age 63 ± 12 years, 7 females, 6 males), 12 of whom were also studied using larger applied (macro-) perturbations requiring active postural responses. The mini-perturbation consisted of a brief impulsive force produced by a mini-shaker applied to the trunk at the level of the shoulders and anteriorly at the upper sternum which was perceived as a tap. Acceleration, force platform, and EMG measurements were made...
April 2018: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/29408659/axonal-regeneration-of-different-tracts-following-transplants-of-human-glial-restricted-progenitors-into-the-injured-spinal-cord-in-rats
#11
Ying Jin, Jed S Shumsky, Itzhak Fischer
The goal of this study was to compare the efficacy of human glial restricted progenitors (hGRPs) in promoting axonal growth of different tracts. We examined the potential of hGRPs grafted into a cervical (C4) dorsal column lesion to test sensory axons, and into a C4 hemisection to test motor tracts. The hGRPs, thawed from frozen stocks, were suspended in a PureCol matrix and grafted acutely into a C4 dorsal column or hemisection lesion. Control rats received PureCol only. Five weeks after transplantation, all transplanted cells survived in rats with the dorsal column lesion but only about half of the grafts in the hemisection...
May 1, 2018: Brain Research
https://www.readbyqxmd.com/read/29386100/terminal-nerve-gnrh3-neurons-mediate-slow-avoidance-of-carbon-dioxide-in-larval-zebrafish
#12
Tetsuya Koide, Yoichi Yabuki, Yoshihiro Yoshihara
Escape responses to threatening stimuli are vital for survival in all animal species. Larval zebrafish display fast escape responses when exposed to tactile, acoustic, and visual stimuli. However, their behavioral responses to chemosensory stimuli remain unknown. In this study, we found that carbon dioxide (CO2 ) induced a slow avoidance response, which was distinct from the touch-evoked fast escape response. We identified the gonadotropin-releasing hormone 3-expressing terminal nerve as the CO2 sensor in the nose...
January 30, 2018: Cell Reports
https://www.readbyqxmd.com/read/29230191/the-reticulospinal-pathway-does-not-increase-its-contribution-to-the-strength-of-contralesional-muscles-in-stroke-survivors-as-compared-to-ipsilesional-side-or-healthy-controls
#13
Sheng Li, Minal Bhadane, Fan Gao, Ping Zhou
Objective: Startling acoustic stimulation (SAS), via activation of reticulospinal (RS) pathways, has shown to increase muscle strength in healthy subjects. We hypothesized that, given RS hyperexcitability in stroke survivors, SAS could increase muscle strength in stroke survivors. The objective was to quantify the effect of SAS on maximal and sub-maximal voluntary elbow flexion on the contralesional (impaired) side in stroke survivors as compared to ipsilesional (non-impaired) side and healthy controls...
2017: Frontiers in Neurology
https://www.readbyqxmd.com/read/29138697/following-spinal-cord-injury-transected-reticulospinal-tract-axons-develop-new-collateral-inputs-to-spinal-interneurons-in-parallel-with-locomotor-recovery
#14
Zacnicte May, Keith K Fenrich, Julia Dahlby, Nicholas J Batty, Abel Torres-Espín, Karim Fouad
The reticulospinal tract (RtST) descends from the reticular formation and terminates in the spinal cord. The RtST drives the initiation of locomotion and postural control. RtST axons form new contacts with propriospinal interneurons (PrINs) after incomplete spinal cord injury (SCI); however, it is unclear if injured or uninjured axons make these connections. We completely transected all traced RtST axons in rats using a staggered model, where a hemisection SCI at vertebra T10 is followed by a contralateral hemisection at vertebra T7...
2017: Neural Plasticity
https://www.readbyqxmd.com/read/29097251/fear-conditioned-alterations-of-motor-cortex-excitability-the-role-of-amygdala
#15
Selim Gökdemir, Ayşegül Gündüz, Çiğdem Özkara, Meral E Kızıltan
BACKGROUND AND OBJECTIVE: We hypothesized that fear-conditioning may increase motor cortical excitability in preparation for response to fear. We tested our hypothesis in healthy subjects and in the second step, to determine the role of amygdala in alterations of motor cortex excitability, we included a group of patients who previously underwent unilateral amygdalo-hippocampectomy for temporal lobe epilepsy. PATIENTS AND METHODS: In the first step, we included 16 healthy volunteers...
October 31, 2017: Neuroscience Letters
https://www.readbyqxmd.com/read/28924005/nigral-glutamatergic-neurons-control-the-speed-of-locomotion
#16
Dimitri Ryczko, Swantje Grätsch, Laura Schläger, Avo Keuyalian, Zakaria Boukhatem, Claudia Garcia, François Auclair, Ansgar Büschges, Réjean Dubuc
The mesencephalic locomotor region (MLR) plays a crucial role in locomotor control. In vertebrates, stimulation of the MLR at increasing intensities elicits locomotion of growing speed. This effect has been presumed to result from higher brain inputs activating the MLR like a dimmer switch. Here, we show in lampreys (Petromyzon marinus) of either sex that incremental stimulation of a region homologous to the mammalian substantia nigra pars compacta (SNc) evokes increasing activation of MLR cells with a graded increase in the frequency of locomotor movements...
October 4, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28912689/monoamine-release-in-the-cat-lumbar-spinal-cord-during-fictive-locomotion-evoked-by-the-mesencephalic-locomotor-region
#17
Brian R Noga, Riza P Turkson, Songtao Xie, Annette Taberner, Alberto Pinzon, Ian D Hentall
Spinal cord neurons active during locomotion are innervated by descending axons that release the monoamines serotonin (5-HT) and norepinephrine (NE) and these neurons express monoaminergic receptor subtypes implicated in the control of locomotion. The timing, level and spinal locations of release of these two substances during centrally-generated locomotor activity should therefore be critical to this control. These variables were measured in real time by fast-cyclic voltammetry in the decerebrate cat's lumbar spinal cord during fictive locomotion, which was evoked by electrical stimulation of the mesencephalic locomotor region (MLR) and registered as integrated activity in bilateral peripheral nerves to hindlimb muscles...
2017: Frontiers in Neural Circuits
https://www.readbyqxmd.com/read/28889979/visual-threat-assessment-and-reticulospinal-encoding-of-calibrated-responses-in-larval-zebrafish
#18
Kiran Bhattacharyya, David L McLean, Malcolm A MacIver
All visual animals must decide whether approaching objects are a threat. Our current understanding of this process has identified a proximity-based mechanism where an evasive maneuver is triggered when a looming stimulus passes a subtended visual angle threshold. However, some escape strategies are more costly than others, and so it would be beneficial to additionally encode the level of threat conveyed by the predator's approach rate to select the most appropriate response. Here, using naturalistic rates of looming visual stimuli while simultaneously monitoring escape behavior and the recruitment of multiple reticulospinal neurons, we find that larval zebrafish do indeed perform a calibrated assessment of threat...
September 25, 2017: Current Biology: CB
https://www.readbyqxmd.com/read/28871033/reticulospinal-contributions-to-gross-hand-function-after-human-spinal-cord-injury
#19
Stuart N Baker, Monica A Perez
Multiple descending motor pathways likely contribute to the recovery of hand motor function following spinal cord injury (SCI). Reticulospinal neurons project to spinal motor neurons controlling hand muscles and extensively sprout into gray matter structures after SCI; therefore, it has been proposed that the reticulospinal tract is one of the descending motor pathways involved in recovery of hand function after injury. To test this hypothesis, we examined the StartReact response, an involuntary release of a planned movement via a startling stimulus that engages the reticulospinal tract, by measuring reaction times from electromyographic activity in an intrinsic finger muscle during three motor tasks requiring different degrees of hand dexterity: index finger abduction, a precision grip, and a power grip...
October 4, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28813815/how-do-strength-and-coordination-recovery-interact-after-stroke-a-computational-model-for-informing-robotic-training
#20
Sumner L Norman, Joan Lobo-Prat, David J Reinkensmeyer
Robotic devices can train strength, coordination, or a combination of both. If a robotic device focuses on coordination, what happens to strength recovery, and vice versa? Understanding this interaction could help optimize robotic training. We developed a computational neurorehabilitation model to gain insight into the interaction between strength and coordination recovery after stroke. In the model, the motor system recovers by optimizing the activity of residual corticospinal cells (focally connected, excitatory and inhibitory) and reticulospinal cells (diffusely connected and excitatory) to achieve a motor task...
July 2017: IEEE ... International Conference on Rehabilitation Robotics: [proceedings]
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