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Blazevich AJ, Mesquita RNO, Pinto RS, Pulverenti T, Ratel S. Reduction and recovery of self-sustained muscle activity after fatiguing plantar flexor contractions. Eur J Appl Physiol 2024; 124:1781-1794. [PMID: 38340155 PMCID: PMC11130039 DOI: 10.1007/s00421-023-05403-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 12/11/2023] [Indexed: 02/12/2024]
Abstract
PURPOSE Persistent inward calcium and sodium currents (PICs) are crucial for initiation and maintenance of motoneuron firing, and thus muscular force. However, there is a lack of data describing the effects of fatiguing exercise on PIC activity in humans. We simultaneously applied tendon vibration and neuromuscular electrical stimulation (VibStim) before and after fatiguing exercise. VibStim induces self-sustained muscle activity that is proposed to result from PIC activation. METHODS Twelve men performed 5-s maximal isometric plantar flexor contractions (MVC) with 5-s rests until joint torque was reduced to 70%MVC. VibStim trials consisted of five 2-s trains of neuromuscular electrical stimulation (20 Hz, evoking 10% MVC) of triceps surae with simultaneous Achilles tendon vibration (115 Hz) without voluntary muscle activation. VibStim was applied before (PRE), immediately (POST), 5-min (POST-5), and 10-min (POST-10) after exercise completion. RESULTS Sustained torque (Tsust) and soleus electromyogram amplitudes (EMG) measured 3 s after VibStim were reduced (Tsust: -59.0%, p < 0.001; soleus EMG: -38.4%, p < 0.001) but largely recovered by POST-5, and changes in MVC and Tsust were correlated across the four time points (r = 0.69; p < 0.001). After normalisation to values obtained at the end of the vibration phase to control for changes in fibre-specific force and EMG signal characteristics, decreases in Tsust (-42.9%) and soleus EMG (-22.6%) remained significant and were each correlated with loss and recovery of MVC (r = 0.41 and 0.46, respectively). CONCLUSION The parallel changes observed in evoked self-sustained muscle activity and force generation capacity provide motivation for future examinations on the potential influence of fatigue-induced PIC changes on motoneuron output.
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Affiliation(s)
- Anthony J Blazevich
- School of Medical and Health Sciences, Centre for Human Performance, Edith Cowan University, Joondalup, Australia.
| | - Ricardo N O Mesquita
- School of Medical and Health Sciences, Centre for Human Performance, Edith Cowan University, Joondalup, Australia
- Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
- Neuroscience Research Australia, Sydney, Australia
| | - Ronei S Pinto
- Exercise Research Laboratory, School of Physical Education, Physiotherapy and Dance, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Timothy Pulverenti
- Department of Physical Therapy, College of Staten Island, Staten Island, NY, USA
| | - Sébastien Ratel
- UFR STAPS - Laboratoire AME2P, Université Clermont Auvergne, Campus Universitaire des Cézeaux, 3 Rue de la Chebarde, 63170, Clermont-Ferrand, France
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Mesquita RNO, Taylor JL, Trajano GS, Holobar A, Gonçalves BAM, Blazevich AJ. Effects of jaw clenching and mental stress on persistent inward currents estimated by two different methods. Eur J Neurosci 2023; 58:4011-4033. [PMID: 37840191 DOI: 10.1111/ejn.16158] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 08/25/2023] [Accepted: 09/13/2023] [Indexed: 10/17/2023]
Abstract
Spinal motoneuron firing depends greatly on persistent inward currents (PICs), which in turn are facilitated by the neuromodulators serotonin and noradrenaline. The aim of this study was to determine whether jaw clenching (JC) and mental stress (MS), which may increase neuromodulator release, facilitate PICs in human motoneurons. The paired motor unit (MU) technique was used to estimate PIC contribution to motoneuron firing. Surface electromyograms were collected using a 32-channel matrix on gastrocnemius medialis (GM) during voluntary, ramp, plantar flexor contractions. MU discharges were identified, and delta frequency (ΔF), a measure of recruitment-derecruitment hysteresis, was calculated. Additionally, another technique was used (VibStim) that evokes involuntary contractions that persist after cessation of combined Achilles tendon vibration and triceps surae neuromuscular electrical stimulation. VibStim measures of plantar flexor torque and soleus activity may reflect PIC activation. ΔF was not significantly altered by JC (p = .679, n = 18, 9 females) or MS (p = .147, n = 14, 5 females). However, all VibStim variables quantifying involuntary torque and muscle activity during and after vibration cessation were significantly increased in JC (p < .011, n = 20, 10 females) and some, but not all, increased in MS (p = .017-.05, n = 19, 10 females). JC and MS significantly increased the magnitude of involuntary contractions (VibStim) but had no effect on GM ΔF during voluntary contractions. Effects of increased neuromodulator release on PIC contribution to motoneuron firing might differ between synergists or be context dependent. Based on these data, the background level of voluntary contraction and, hence, both neuromodulation and ionotropic inputs could influence neuromodulatory PIC enhancement.
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Affiliation(s)
- Ricardo N O Mesquita
- Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
- Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia
- Neuroscience Research Australia, Sydney, New South Wales, Australia
| | - Janet L Taylor
- Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia
- Neuroscience Research Australia, Sydney, New South Wales, Australia
| | - Gabriel S Trajano
- School of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Basílio A M Gonçalves
- Neuromechanics Research Group, Centre for Sport Science and University Sports, University of Vienna, Vienna, Austria
| | - Anthony J Blazevich
- Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia
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3
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Lapole T, Mesquita RNO, Baudry S, Souron R, Brownstein CG, Rozand V. Can local vibration alter the contribution of persistent inward currents to human motoneuron firing? J Physiol 2023; 601:1467-1482. [PMID: 36852473 DOI: 10.1113/jp284210] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 02/23/2023] [Indexed: 03/01/2023] Open
Abstract
The response of spinal motoneurons to synaptic input greatly depends on the activation of persistent inward currents (PICs), which in turn are enhanced by the neuromodulators serotonin and noradrenaline. Local vibration (LV) induces excitatory Ia input onto motoneurons and may alter neuromodulatory inputs. Therefore, we investigated whether LV influences the contribution of PICs to motoneuron firing. This was assessed in voluntary contractions with concurrent, ongoing LV, as well as after a bout of prolonged LV. High-density surface electromyograms (HD-EMG) of the tibialis anterior were recorded with a 64-electrode matrix. Twenty males performed isometric, triangular, dorsiflexion contractions to 20% and 50% of maximal torque at baseline, during LV of the tibialis anterior muscle, and after 30-min of LV. HD-EMG signals were decomposed, and motor units tracked across time points to estimate PICs through a paired motor unit analysis, which quantifies motor unit recruitment-derecruitment hysteresis (ΔF). During ongoing LV, ΔF was lower for both 20% and 50% ramps. Although significant changes in ΔF were not observed after prolonged LV, a differential effect across the motoneuron pool was observed. This study demonstrates that PICs can be non-pharmacologically modulated by LV. Given that LV leads to reflexive motor unit activation, it is postulated that lower PIC contribution to motoneuron firing during ongoing LV results from decreased neuromodulatory inputs associated with lower descending corticospinal drive. A differential effect in motoneurons of different recruitment thresholds after prolonged LV is provocative, challenging the interpretation of previous observations and motivating future investigations. KEY POINTS: Neuromodulatory inputs from the brainstem influence motoneuron intrinsic excitability through activation of persistent inward currents (PICs). PICs make motoneurons more responsive to excitatory input. We demonstrate that vibration applied on the muscle modulates the contribution of PICs to motoneuron firing, as observed through analysis of the firing of single motor units. The effects of PICs on motoneuron firing were lower when vibration was concurrently applied during voluntary ramp contractions, likely due to lower levels of neuromodulation. Additionally, prolonged exposure to vibration led to differential effects of lower- vs. higher-threshold motor units on PICs, with lower-threshold motor units tending to present an increased and higher-threshold motor units a decreased contribution of PICs to motoneuron firing. These results demonstrate that muscle vibration has the potential to influence the effects of neuromodulation on motoneuron firing. The potential of using vibration as a non-pharmacological neuromodulatory intervention should be further investigated.
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Affiliation(s)
- T Lapole
- Université Jean Monnet Saint-Etienne, Lyon 1, Université Savoie Mont-Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, Saint-Etienne, France
| | - R N O Mesquita
- Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
- School of Medical and Health Sciences, Edith Cowan University, Perth, Australia
- Neuroscience Research Australia, Sydney, Australia
| | - S Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - R Souron
- Movement-Interactions-Performance, MIP, UR 4334, Nantes Université, 44000 Nantes, France
| | - C G Brownstein
- Université Jean Monnet Saint-Etienne, Lyon 1, Université Savoie Mont-Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, Saint-Etienne, France
| | - V Rozand
- Université Jean Monnet Saint-Etienne, Lyon 1, Université Savoie Mont-Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, Saint-Etienne, France
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Abstract
The frontal lobe is crucial and contributes to controlling truncal motion, postural responses, and maintaining equilibrium and locomotion. The rich repertoire of frontal gait disorders gives some indication of this complexity. For human walking, it is necessary to simultaneously achieve at least two tasks, such as maintaining a bipedal upright posture and locomotion. Particularly, postural control plays an extremely significant role in enabling the subject to maintain stable gait behaviors to adapt to the environment. To achieve these requirements, the frontal cortex (1) uses cognitive information from the parietal, temporal, and occipital cortices, (2) creates plans and programs of gait behaviors, and (3) acts on the brainstem and spinal cord, where the core posture-gait mechanisms exist. Moreover, the frontal cortex enables one to achieve a variety of gait patterns in response to environmental changes by switching gait patterns from automatic routine to intentionally controlled and learning the new paradigms of gait strategy via networks with the basal ganglia, cerebellum, and limbic structures. This chapter discusses the role of each area of the frontal cortex in behavioral control and attempts to explain how frontal lobe controls walking with special reference to postural control.
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Affiliation(s)
- Kaoru Takakusaki
- Department of Physiology, Division of Neuroscience, Asahikawa Medical University, Asahikawa, Japan.
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Kavanagh JJ, Taylor JL. Voluntary activation of muscle in humans: does serotonergic neuromodulation matter? J Physiol 2022; 600:3657-3670. [PMID: 35864781 PMCID: PMC9541597 DOI: 10.1113/jp282565] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 07/12/2022] [Indexed: 11/08/2022] Open
Abstract
Ionotropic inputs to motoneurones have the capacity to depolarise and hyperpolarise the motoneurone, whereas neuromodulatory inputs control the state of excitability of the motoneurone. Intracellular recordings of motoneurones from in vitro and in situ animal preparations have provided extraordinary insight into the mechanisms that underpin how neuromodulators regulate neuronal excitability. However, far fewer studies have attempted to translate the findings from cellular and molecular studies into a human model. In this review, we focus on the role that serotonin (5-HT) plays in muscle activation in humans. 5-HT is a potent regulator of neuronal firing rates, which can influence the force that can be generated by muscles during voluntary contractions. We firstly outline structural and functional characteristics of the serotonergic system, and then describe how motoneurone discharge can be facilitated and suppressed depending on the 5-HT receptor subtype that is activated. We then provide a narrative on how 5-HT effects can influence voluntary activation during muscle contractions in humans, and detail how 5-HT may be a mediator of exercise-induced fatigue that arises from the central nervous system.
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Affiliation(s)
- Justin J. Kavanagh
- Neural Control of Movement laboratoryMenzies Health Institute QueenslandGriffith UniversityGold CoastAustralia
| | - Janet L. Taylor
- Centre for Human Performance, School of Medical and Health SciencesEdith Cowan UniversityPerthAustralia
- Neuroscience Research AustraliaSydneyAustralia
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Noga BR, Whelan PJ. The Mesencephalic Locomotor Region: Beyond Locomotor Control. Front Neural Circuits 2022; 16:884785. [PMID: 35615623 PMCID: PMC9124768 DOI: 10.3389/fncir.2022.884785] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 04/14/2022] [Indexed: 11/25/2022] Open
Abstract
The mesencephalic locomotor region (MLR) was discovered several decades ago in the cat. It was functionally defined based on the ability of low threshold electrical stimuli within a region comprising the cuneiform and pedunculopontine nucleus to evoke locomotion. Since then, similar regions have been found in diverse vertebrate species, including the lamprey, skate, rodent, pig, monkey, and human. The MLR, while often viewed under the lens of locomotion, is involved in diverse processes involving the autonomic nervous system, respiratory system, and the state-dependent activation of motor systems. This review will discuss the pedunculopontine nucleus and cuneiform nucleus that comprises the MLR and examine their respective connectomes from both an anatomical and functional angle. From a functional perspective, the MLR primes the cardiovascular and respiratory systems before the locomotor activity occurs. Inputs from a variety of higher structures, and direct outputs to the monoaminergic nuclei, allow the MLR to be able to respond appropriately to state-dependent locomotion. These state-dependent effects are roughly divided into escape and exploratory behavior, and the MLR also can reinforce the selection of these locomotor behaviors through projections to adjacent structures such as the periaqueductal gray or to limbic and cortical regions. Findings from the rat, mouse, pig, and cat will be discussed to highlight similarities and differences among diverse species.
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Affiliation(s)
- Brian R. Noga
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, Miller School of Medicine, University of Miami, Miami, FL, United States
- *Correspondence: Brian R. Noga Patrick J. Whelan
| | - Patrick J. Whelan
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
- *Correspondence: Brian R. Noga Patrick J. Whelan
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7
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Mesquita RNO, Taylor JL, Trajano GS, Škarabot J, Holobar A, Gonçalves BAM, Blazevich AJ. Effects of reciprocal inhibition and whole-body relaxation on persistent inward currents estimated by two different methods. J Physiol 2022; 600:2765-2787. [PMID: 35436349 PMCID: PMC9325475 DOI: 10.1113/jp282765] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 04/13/2022] [Indexed: 11/08/2022] Open
Abstract
Abstract Persistent inward currents (PICs) are crucial for initiation, acceleration, and maintenance of motoneuron firing. As PICs are highly sensitive to synaptic inhibition and facilitated by serotonin and noradrenaline, we hypothesised that both reciprocal inhibition (RI) induced by antagonist nerve stimulation and whole‐body relaxation (WBR) would reduce PICs in humans. To test this, we estimated PICs using the well‐established paired motor unit (MU) technique. High‐density surface electromyograms were recorded from gastrocnemius medialis during voluntary, isometric 20‐s ramp, plantarflexor contractions and decomposed into MU discharges to calculate delta frequency (ΔF). Moreover, another technique (VibStim), which evokes involuntary contractions proposed to result from PIC activation, was used. Plantarflexion torque and soleus activity were recorded during 33‐s Achilles tendon vibration and simultaneous 20‐Hz bouts of neuromuscular electrical stimulation (NMES) of triceps surae. ΔF was decreased by RI (n = 15, 5 females) and WBR (n = 15, 7 females). In VibStim, torque during vibration at the end of NMES and sustained post‐vibration torque were reduced by WBR (n = 19, 10 females), while other variables remained unchanged. All VibStim variables remained unaltered in RI (n = 20, 10 females). Analysis of multiple human MUs in this study demonstrates the ability of local, focused inhibition to attenuate the effects of PICs on motoneuron output during voluntary motor control. Moreover, it shows the potential to reduce PICs through non‐pharmacological, neuromodulatory interventions such as WBR. The absence of a consistent effect in VibStim might be explained by a floor effect resulting from low‐magnitude involuntary torque combined with the negative effects of the interventions. Key points Spinal motoneurons transmit signals to skeletal muscles to regulate their contraction. Motoneuron firing partly depends on their intrinsic properties such as the strength of persistent (long‐lasting) inward currents (PICs) that make motoneurons more responsive to excitatory input. In this study, we demonstrate that both reciprocal inhibition onto motoneurons and whole‐body relaxation reduce the contribution of PICs to human motoneuron firing. This was observed through analysis of the firing of single motor units during voluntary contractions. However, an alternative technique that involves tendon vibration and neuromuscular electrical stimulation to evoke involuntary contractions showed less effect. Thus, it remains unclear whether this alternative technique can be used to estimate PICs under all physiological conditions. These results improve our understanding of the mechanisms of PIC depression in human motoneurons. Potentially, non‐pharmacological interventions such as electrical stimulation or relaxation could attenuate unwanted PIC‐induced muscle contractions in conditions characterised by motoneuron hyperexcitability.
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Affiliation(s)
- Ricardo N O Mesquita
- Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Perth, Australia.,Neuroscience Research Australia, Sydney, Australia
| | - Janet L Taylor
- Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Perth, Australia.,Neuroscience Research Australia, Sydney, Australia
| | - Gabriel S Trajano
- School of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
| | - Jakob Škarabot
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, UK
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Basílio A M Gonçalves
- Griffith Centre of Biomedical and Rehabilitation Engineering (GCORE), Menzies Health Institute Queensland, Griffith University, Brisbane, Australia
| | - Anthony J Blazevich
- Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Perth, Australia
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Wollman L, Hill A, Hasse B, Young C, Hernandez-De La Pena G, Levine RB, Fregosi RF. Influence of developmental nicotine exposure on serotonergic control of breathing-related motor output. Dev Neurobiol 2022; 82:175-191. [PMID: 35016263 PMCID: PMC8940681 DOI: 10.1002/dneu.22866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 12/06/2021] [Accepted: 01/04/2022] [Indexed: 11/07/2022]
Abstract
Serotonin plays an important role in the development of brainstem circuits that control breathing. Here, we test the hypothesis that developmental nicotine exposure (DNE) alters the breathing-related motor response to serotonin (5HT). Pregnant rats were exposed to nicotine or saline, and brainstem-spinal cord preparations from 1- to 5-day-old pups were studied in a split-bath configuration, allowing drugs to be applied selectively to the medulla or spinal cord. The activity of the fourth cervical ventral nerve roots (C4VR), which contain axons of phrenic motoneurons, was recorded. We applied 5HT alone or together with antagonists of 5HT1A, 5HT2A, or 5HT7 receptor subtypes. In control preparations, 5HT applied to the medulla consistently reduced C4VR frequency and this reduction could not be blocked by any of the three antagonists. In DNE preparations, medullary 5HT caused a large and sustained frequency increase (10 min), followed by a sustained decrease. Notably, the transient increase in frequency could be blocked by the independent addition of any of the antagonists. Experiments with subtype-specific agonists suggest that the 5HT7 subtype may contribute to the increased frequency response in the DNE preparations. Changes in C4VR burst amplitude in response to brainstem 5HT were uninfluenced by DNE. Addition of 5HT to the caudal chamber modestly increased phasic and greatly increased tonic C4VR activity, but there were no effects of DNE. The data show that DNE alters serotonergic signaling within brainstem circuits that control respiratory frequency but does not functionally alter serotonin signaling in the phrenic motoneuron pool.
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Affiliation(s)
- Lila Wollman
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ
| | - Andrew Hill
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ
| | - Brady Hasse
- Department of Neuroscience, University of Arizona, Tucson, AZ
| | - Christina Young
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ
| | | | - Richard B Levine
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ,Department of Neuroscience, University of Arizona, Tucson, AZ
| | - Ralph F. Fregosi
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ,Department of Neuroscience, University of Arizona, Tucson, AZ
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Goodlich BI, Horan SA, Kavanagh JJ. Blockade of 5-HT 2 receptors suppresses rate of torque development and motor unit discharge rate during rapid contractions. J Neurophysiol 2021; 127:150-160. [PMID: 34936830 DOI: 10.1152/jn.00470.2021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Serotonin (5-HT) is a neuromodulator that is critical for regulating the excitability of spinal motoneurons and the generation of muscle torque. However, the role of 5-HT in modulating human motor unit activity during rapid contractions has yet to be assessed. Nine healthy participants (23.7 ± 2.2 yr) ingested 8 mg of the competitive 5-HT2 antagonist cyproheptadine in a double-blinded, placebo-controlled, repeated-measures experiment. Rapid dorsiflexion contractions were performed at 30%, 50% and 70% of maximal voluntary contraction (MVC), where motor unit activity was assessed by high-density surface electromyographic decomposition. A second protocol was performed where a sustained, fatigue-inducing dorsiflexion contraction was completed prior to undertaking the same 30%, 50% and 70% MVC rapid contractions and motor unit analysis. Motor unit discharge rate (p < 0.001) and rate of torque development (RTD; p = 0.019) for the unfatigued muscle were both significantly lower for the cyproheptadine condition. Following the fatigue inducing contraction, cyproheptadine reduced motor unit discharge rate (p < 0.001) and RTD (p = 0.024), where the effects of cyproheptadine on motor unit discharge rate and RTD increased with increasing contraction intensity. Overall, these results support the viewpoint that serotonergic effects in the central nervous system occur fast enough to regulate motor unit discharge rate during rapid powerful contractions.
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Affiliation(s)
| | - Sean A Horan
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia
| | - Justin J Kavanagh
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia
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Noga BR, Guest JD. Combined neuromodulatory approaches in the central nervous system for treatment of spinal cord injury. Curr Opin Neurol 2021; 34:804-811. [PMID: 34593718 PMCID: PMC8595808 DOI: 10.1097/wco.0000000000000999] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE OF REVIEW To report progress in neuromodulation following spinal cord injury (SCI) using combined brain and spinal neuromodulation.Neuromodulation refers to alterations in neuronal activity for therapeutic purposes. Beneficial effects are established in disease states such as Parkinson's Disease (PD), chronic pain, epilepsy, and SCI. The repertoire of neuromodulation and bioelectric medicine is rapidly expanding. After SCI, cohort studies have reported the benefits of epidural stimulation (ES) combined with training. Recently, we have explored combining ES with deep brain stimulation (DBS) to increase activation of descending motor systems to address limitations of ES in severe SCI. In this review, we describe the types of applied neuromodulation that could be combined in SCI to amplify efficacy to enable movement. These include ES, mesencephalic locomotor region (MLR) - DBS, noninvasive transcutaneous stimulation, transcranial magnetic stimulation, paired-pulse paradigms, and neuromodulatory drugs. We examine immediate and longer-term effects and what is known about: (1) induced neuroplastic changes, (2) potential safety concerns; (3) relevant outcome measures; (4) optimization of stimulation; (5) therapeutic limitations and prospects to overcome these. RECENT FINDINGS DBS of the mesencephalic locomotor region is emerging as a potential clinical target to amplify supraspinal command circuits for locomotion. SUMMARY Combinations of neuromodulatory methods may have additive value for restoration of function after spinal cord injury.
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Affiliation(s)
- Brian R Noga
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, Florida, USA
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11
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Ferreira-Pinto MJ, Kanodia H, Falasconi A, Sigrist M, Esposito MS, Arber S. Functional diversity for body actions in the mesencephalic locomotor region. Cell 2021; 184:4564-4578.e18. [PMID: 34302739 PMCID: PMC8382160 DOI: 10.1016/j.cell.2021.07.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 05/06/2021] [Accepted: 06/30/2021] [Indexed: 12/13/2022]
Abstract
The mesencephalic locomotor region (MLR) is a key midbrain center with roles in locomotion. Despite extensive studies and clinical trials aimed at therapy-resistant Parkinson's disease (PD), debate on its function remains. Here, we reveal the existence of functionally diverse neuronal populations with distinct roles in control of body movements. We identify two spatially intermingled glutamatergic populations separable by axonal projections, mouse genetics, neuronal activity profiles, and motor functions. Most spinally projecting MLR neurons encoded the full-body behavior rearing. Loss- and gain-of-function optogenetic perturbation experiments establish a function for these neurons in controlling body extension. In contrast, Rbp4-transgene-positive MLR neurons project in an ascending direction to basal ganglia, preferentially encode the forelimb behaviors handling and grooming, and exhibit a role in modulating movement. Thus, the MLR contains glutamatergic neuronal subpopulations stratified by projection target exhibiting roles in action control not restricted to locomotion.
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Affiliation(s)
- Manuel J Ferreira-Pinto
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Harsh Kanodia
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Antonio Falasconi
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Markus Sigrist
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Maria S Esposito
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Silvia Arber
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland.
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12
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Chang SJ, Cajigas I, Guest JD, Noga BR, Widerström-Noga E, Haq I, Fisher L, Luca CC, Jagid JR. MR Tractography-Based Targeting and Physiological Identification of the Cuneiform Nucleus for Directional DBS in a Parkinson's Disease Patient With Levodopa-Resistant Freezing of Gait. Front Hum Neurosci 2021; 15:676755. [PMID: 34168545 PMCID: PMC8217631 DOI: 10.3389/fnhum.2021.676755] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/11/2021] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Freezing of gait (FOG) is a debilitating motor deficit in a subset of Parkinson's Disease (PD) patients that is poorly responsive to levodopa or deep brain stimulation (DBS) of established PD targets. The proposal of a DBS target in the midbrain, known as the pedunculopontine nucleus (PPN), to address FOG was based on its observed neuropathology in PD and its hypothesized involvement in locomotor control as a part of the mesencephalic locomotor region (MLR). Initial reports of PPN DBS were met with enthusiasm; however, subsequent studies reported mixed results. A closer review of the MLR basic science literature, suggests that the closely related cuneiform nucleus (CnF), dorsal to the PPN, may be a superior site to promote gait. Although suspected to have a conserved role in the control of gait in humans, deliberate stimulation of a homolog to the CnF in humans using directional DBS electrodes has not been attempted. METHODS As part of an open-label Phase 1 clinical study, one PD patient with predominantly axial symptoms and severe FOG refractory to levodopa therapy was implanted with directional DBS electrodes (Boston Science Vercise CartesiaTM) targeting the CnF bilaterally. Since the CnF is a poorly defined reticular nucleus, targeting was guided both by diffusion tensor imaging (DTI) tractography and anatomical landmarks. Intraoperative stimulation and microelectrode recordings were performed near the targets with leg EMG surface recordings in the subject. RESULTS Post-operative imaging revealed accurate targeting of both leads to the designated CnF. Intraoperative stimulation near the target at low thresholds in the awake patient evoked involuntary electromyography (EMG) oscillations in the legs with a peak power at the stimulation frequency, similar to observations with CnF DBS in animals. Oscillopsia was the primary side effect evoked at higher currents, especially when directed posterolaterally. Directional DBS could mitigate oscillopsia. CONCLUSION DTI-based targeting and intraoperative stimulation to evoke limb EMG activity may be useful methods to help target the CnF accurately and safely in patients. Long term follow-up and detailed gait testing of patients undergoing CnF stimulation will be necessary to confirm the effects on FOG. CLINICAL TRIAL REGISTRATION Clinicaltrials.gov identifier: NCT04218526.
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Affiliation(s)
- Stephano J. Chang
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurosurgery, University of British Columbia, Vancouver, BC, Canada
| | - Iahn Cajigas
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - James D. Guest
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Brian R. Noga
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Eva Widerström-Noga
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Ihtsham Haq
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Letitia Fisher
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Corneliu C. Luca
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Jonathan R. Jagid
- The Miami Project to Cure Paralysis, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
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13
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Liu H, Xiong D, Pang R, Deng Q, Sun N, Zheng J, Liu J, Xiang W, Chen Z, Lu J, Wang W, Zhang A. Effects of repetitive magnetic stimulation on motor function and GAP43 and 5-HT expression in rats with spinal cord injury. J Int Med Res 2021; 48:300060520970765. [PMID: 33356694 PMCID: PMC7783896 DOI: 10.1177/0300060520970765] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Objectives Spinal cord injury (SCI) is a disabling central nervous system disorder. This
study aimed to explore the effects of repetitive trans-spinal magnetic
stimulation (rTSMS) of different spinal cord segments on movement function
and growth-associated protein-43 (GAP43) and 5-hydroxytryptamine (5-HT)
expression in rats after acute SCI and to preliminarily discuss the optimal
rTSMS treatment site to provide a theoretical foundation and experimental
evidence for clinical application of rTSMS in SCI. Methods A rat T10 laminectomy SCI model produced by transient application of an
aneurysm clip was used in the study. The rats were divided into group A
(sham surgery), group B (acute SCI without stimulation), group C (T6 segment
stimulation), group D (T10 segment stimulation), and group E (L2 segment
stimulation). Results In vivo magnetic stimulation protected motor function, alleviated myelin
sheath damage, decreased NgR and Nogo-A expression levels, increased GAP43
and 5-HT expression levels, and inhibited terminal deoxynucleotidyl
transferase dUTP nick end labeling-positive cells and apoptosis-related
protein expression in rats at 8 weeks after the surgery. Conclusions This study suggests that rTSMS can promote GAP43 and 5-HT expression and
axonal regeneration in the spinal cord, which is beneficial to motor
function recovery after acute SCI.
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Affiliation(s)
- Hao Liu
- Department of Rehabilitation, Shanghai Fourth People's Hospital Affiliated with Tongji University School of Medicine, Shanghai, P.R. China.,Department of Rehabilitation, The First Affiliated Hospital of Naval Medical University, Shanghai, P.R. China
| | - Deqi Xiong
- Department of Rehabilitation, The Second People's Hospital of Yibin, Yibin, Sichuan, P.R. China
| | - Rizhao Pang
- Department of Rehabilitation, The General Hospital of Western Theater Command, Chengdu, Sichuan, P.R. China
| | - Qian Deng
- School of Medicine, Southwest Jiaotong University, Chengdu, Sichuan, P.R. China
| | - Nianyi Sun
- Department of Rehabilitation, Shengjing Hospital of China Medical University, Shenyang, Liaoning, P.R. China
| | - Jinqi Zheng
- Department of Rehabilitation, The General Hospital of Western Theater Command, Chengdu, Sichuan, P.R. China
| | - Jiancheng Liu
- Department of Rehabilitation, The General Hospital of Western Theater Command, Chengdu, Sichuan, P.R. China
| | - Wu Xiang
- Department of Rehabilitation, The General Hospital of Western Theater Command, Chengdu, Sichuan, P.R. China
| | - Zhesi Chen
- Department of Rehabilitation, The General Hospital of Western Theater Command, Chengdu, Sichuan, P.R. China
| | - Jiachun Lu
- Department of Rehabilitation, Chengdu Eighth People's Hospital, Chengdu, Sichuan, P.R. China
| | - Wenchun Wang
- Department of Rehabilitation, The General Hospital of Western Theater Command, Chengdu, Sichuan, P.R. China
| | - Anren Zhang
- Department of Rehabilitation, Shanghai Fourth People's Hospital Affiliated with Tongji University School of Medicine, Shanghai, P.R. China
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14
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Thorstensen JR, Taylor JL, Kavanagh JJ. Human corticospinal-motoneuronal output is reduced with 5-HT 2 receptor antagonism. J Neurophysiol 2021; 125:1279-1288. [PMID: 33596722 DOI: 10.1152/jn.00698.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Animal models indicate that serotonin (5-HT) release onto motoneurons facilitates motor output, particularly during strong motor activities. However, evidence for 5-HT effects during human movement are limited. This study examined how antagonism of the 5-HT2 receptor, which is a 5-HT receptor that promotes motoneuron excitability, affects human movement. Ten healthy participants (24.2 ± 1.9 yr) ingested 8 mg of cyproheptadine (competitive 5-HT2 antagonist) in a double-blinded, placebo-controlled, repeated-measures design. Transcranial magnetic stimulation (TMS) of the motor cortex was used to elicit motor evoked potentials (MEPs) from biceps brachii. First, stimulus-response curves (90%-160% active motor threshold) were obtained during very weak elbow flexions (10% of maximal). Second, to determine if 5-HT effects are scaled to the intensity of muscle contraction, TMS at a fixed intensity was applied during elbow flexions of 20%, 40%, 60%, 80%, and 100% of maximal. Cyproheptadine reduced the size of MEPs across the stimulus-response curves (P = 0.045). Notably, MEP amplitude was 22.3% smaller for the cyproheptadine condition for the strongest TMS intensity. In addition, cyproheptadine reduced maximal torque (P = 0.045), lengthened the biceps silent period during maximal elbow flexions (P = 0.037), and reduced superimposed twitch amplitude during moderate-intensity elbow flexions (P = 0.035). This study presents novel evidence that 5-HT2 receptors influence corticospinal-motoneuronal output, which was particularly evident when a large number of descending inputs to motoneurons were active. Although it is likely that antagonism of 5-HT2 receptors reduces motoneuron gain to ionotropic inputs, supraspinal mechanisms may have also contributed to the study findings.NEW & NOTEWORTHY Voluntary contractions and responses to magnetic stimulation of the motor cortex are dependent on serotonin activity in the central nervous system. 5-HT2 antagonism decreased evoked potential size to high-intensity stimulation, and reduced torque and lengthened inhibitory silent periods during maximal contractions. We provide novel evidence that 5-HT2 receptors are involved in muscle activation, where 5-HT effects are strongest when a large number of descending inputs activate motoneurons.
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Affiliation(s)
- Jacob R Thorstensen
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
| | - Janet L Taylor
- School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia.,Neuroscience Research Australia (NeuRA), Sydney, New South Wales, Australia
| | - Justin J Kavanagh
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
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15
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Flaive A, Fougère M, van der Zouwen CI, Ryczko D. Serotonergic Modulation of Locomotor Activity From Basal Vertebrates to Mammals. Front Neural Circuits 2020; 14:590299. [PMID: 33224027 PMCID: PMC7674590 DOI: 10.3389/fncir.2020.590299] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 09/28/2020] [Indexed: 12/14/2022] Open
Abstract
During the last 50 years, the serotonergic (5-HT) system was reported to exert a complex modulation of locomotor activity. Here, we focus on two key factors that likely contribute to such complexity. First, locomotion is modulated directly and indirectly by 5-HT neurons. The locomotor circuitry is directly innervated by 5-HT neurons in the caudal brainstem and spinal cord. Also, indirect control of locomotor activity results from ascending projections of 5-HT cells in the rostral brainstem that innervate multiple brain centers involved in motor action planning. Second, each approach used to manipulate the 5-HT system likely engages different 5-HT-dependent mechanisms. This includes the recruitment of different 5-HT receptors, which can have excitatory or inhibitory effects on cell activity. These receptors can be located far or close to the 5-HT release sites, making their activation dependent on the level of 5-HT released. Here we review the activity of different 5-HT nuclei during locomotor activity, and the locomotor effects of 5-HT precursors, exogenous 5-HT, selective 5-HT reuptake inhibitors (SSRI), electrical or chemical stimulation of 5-HT neurons, genetic deletions, optogenetic and chemogenetic manipulations. We highlight both the coherent and controversial aspects of 5-HT modulation of locomotor activity from basal vertebrates to mammals. This mini review may hopefully inspire future studies aiming at dissecting the complex effects of 5-HT on locomotor function.
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Affiliation(s)
- Aurélie Flaive
- Département de Pharmacologie-Physiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Maxime Fougère
- Département de Pharmacologie-Physiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Cornelis Immanuel van der Zouwen
- Département de Pharmacologie-Physiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Dimitri Ryczko
- Département de Pharmacologie-Physiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada.,Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada.,Institut de Pharmacologie de Sherbrooke, Sherbrooke, QC, Canada.,Centre des Neurosciences de Sherbrooke, Sherbrooke, QC, Canada
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16
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Biological data questions the support of the self inhibition required for pattern generation in the half center model. PLoS One 2020; 15:e0238586. [PMID: 32915814 PMCID: PMC7485810 DOI: 10.1371/journal.pone.0238586] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Accepted: 08/19/2020] [Indexed: 11/19/2022] Open
Abstract
Locomotion control in mammals has been hypothesized to be governed by a central pattern generator (CPG) located in the circuitry of the spinal cord. The most common model of the CPG is the half center model, where two pools of neurons generate alternating, oscillatory activity. In this model, the pools reciprocally inhibit each other ensuring alternating activity. There is experimental support for reciprocal inhibition. However another crucial part of the half center model is a self inhibitory mechanism which prevents the neurons of each individual pool from infinite firing. Self-inhibition is hence necessary to obtain alternating activity. But critical parts of the experimental bases for the proposed mechanisms for self-inhibition were obtained in vitro, in preparations of juvenile animals. The commonly used adaptation of spike firing does not appear to be present in adult animals in vivo. We therefore modeled several possible self inhibitory mechanisms for locomotor control. Based on currently published data, previously proposed hypotheses of the self inhibitory mechanism, necessary to support the CPG hypothesis, seems to be put into question by functional evaluation tests or by in vivo data. This opens for alternative explanations of how locomotion activity patterns in the adult mammal could be generated.
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17
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Chang SJ, Cajigas I, Opris I, Guest JD, Noga BR. Dissecting Brainstem Locomotor Circuits: Converging Evidence for Cuneiform Nucleus Stimulation. Front Syst Neurosci 2020; 14:64. [PMID: 32973468 PMCID: PMC7473103 DOI: 10.3389/fnsys.2020.00064] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 08/03/2020] [Indexed: 01/06/2023] Open
Abstract
There are a pressing and unmet need for effective therapies for freezing of gait (FOG) and other neurological gait disorders. Deep brain stimulation (DBS) of a midbrain target known as the pedunculopontine nucleus (PPN) was proposed as a potential treatment based on its postulated involvement in locomotor control as part of the mesencephalic locomotor region (MLR). However, DBS trials fell short of expectations, leading many clinicians to abandon this strategy. Here, we discuss the potential reasons for this failure and review recent clinical data along with preclinical optogenetics evidence to argue that another nearby nucleus, the cuneiform nucleus (CnF), may be a superior target.
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Affiliation(s)
- Stephano J. Chang
- Neuroscience Graduate Program, University of Miami Miller School of Medicine, Miami, FL, United States
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL, United States
- Division of Neurosurgery, Department of Surgery, University of British Columbia, Vancouver, BC, Canada
| | - Iahn Cajigas
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Ioan Opris
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL, United States
| | - James D. Guest
- Neuroscience Graduate Program, University of Miami Miller School of Medicine, Miami, FL, United States
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Brian R. Noga
- Neuroscience Graduate Program, University of Miami Miller School of Medicine, Miami, FL, United States
- The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL, United States
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
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18
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Aguilar Garcia IG, Dueñas-Jiménez JM, Castillo L, Osuna-Carrasco LP, De La Torre Valdovinos B, Castañeda-Arellano R, López-Ruiz JR, Toro-Castillo C, Treviño M, Mendizabal-Ruiz G, Duenas-Jimenez SH. Fictive Scratching Patterns in Brain Cortex-Ablated, Midcollicular Decerebrate, and Spinal Cats. Front Neural Circuits 2020; 14:1. [PMID: 32174815 PMCID: PMC7056700 DOI: 10.3389/fncir.2020.00001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 01/03/2020] [Indexed: 11/13/2022] Open
Abstract
Background: The spinal cord’s central pattern generators (CPGs) have been explained by the symmetrical half-center hypothesis, the bursts generator, computational models, and more recently by connectome circuits. Asymmetrical models, at odds with the half-center paradigm, are composed of extensor and flexor CPG modules. Other models include not only flexor and extensor motoneurons but also motoneuron pools controlling biarticular muscles. It is unknown whether a preferred model can explain some particularities that fictive scratching (FS) in the cat presents. The first aim of this study was to investigate FS patterns considering the aiming and the rhythmic periods, and second, to examine the effects of serotonin (5HT) on and segmental inputs to FS. Methods: The experiments were carried out first in brain cortex-ablated cats (BCAC), then spinalized (SC), and for the midcollicular (MCC) preparation. Subjects were immobilized and the peripheral nerves were used to elicit the Monosynaptic reflex (MR), to modify the scratching patterns and for electroneurogram recordings. Results: In BCAC, FS was produced by pinna stimulation and, in some cases, by serotonin. The scratching aiming phase (AP) initiates with the activation of either flexor or extensor motoneurons. Serotonin application during the AP produced simultaneous extensor and flexor bursts. Furthermore, WAY 100635 (5HT1A antagonist) produced a brief burst in the tibialis anterior (TA) nerve, followed by a reduction in its electroneurogram (ENG), while the soleus ENG remained silent. In SC, rhythmic phase (RP) activity was recorded in the soleus motoneurons. Serotonin or WAY produced FS bouts. The electrical stimulation of Ia afferent fibers produced heteronymous MRes waxing and waning during the scratch cycle. In MCC, FS began with flexor activity. Electrical stimulation of either deep peroneus (DP) or superficial peroneus (SP) nerves increased the duration of the TA electroneurogram. Medial gastrocnemius (MG) stretching or MG nerve electrical stimulation produced a reduction in the TA electroneurogram and an initial MG extensor burst. MRes waxed and waned during the scratch cycle. Conclusion: Descending pathways and segmental afferent fibers, as well as 5-HT and WAY, can change the FS pattern. To our understanding, the half-center hypothesis is the most suitable for explaining the AP in MCC.
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Affiliation(s)
| | | | - Luis Castillo
- Centro Básico, Universidad de Aguascalientes, Aguascalientes, Mexico
| | | | | | | | | | - Carmen Toro-Castillo
- Departmento de Electrónica y Computación, CUCEI, Universidad de Guadalajara, Guadalajara, Mexico
| | - Mario Treviño
- Laboratorio de Plasticidad Cortical y Aprendizaje Perceptual, Instituto de Neurociencias, Universidad de Guadalajara, Guadalajara, Mexico
| | - Gerardo Mendizabal-Ruiz
- Departmento de Electrónica y Computación, CUCEI, Universidad de Guadalajara, Guadalajara, Mexico
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19
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Opris I, Dai X, Johnson DMG, Sanchez FJ, Villamil LM, Xie S, Lee-Hauser CR, Chang S, Jordan LM, Noga BR. Activation of Brainstem Neurons During Mesencephalic Locomotor Region-Evoked Locomotion in the Cat. Front Syst Neurosci 2019; 13:69. [PMID: 31798423 PMCID: PMC6868058 DOI: 10.3389/fnsys.2019.00069] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/31/2019] [Indexed: 12/26/2022] Open
Abstract
The distribution of locomotor-activated neurons in the brainstem of the cat was studied by c-Fos immunohistochemistry in combination with antibody-based cellular phenotyping following electrical stimulation of the mesencephalic locomotor region (MLR) – the anatomical constituents of which remain debated today, primarily between the cuneiform (CnF) and the pedunculopontine tegmental nuclei (PPT). Effective MLR sites were co-extensive with the CnF nucleus. Animals subject to the locomotor task showed abundant Fos labeling in the CnF, parabrachial nuclei of the subcuneiform region, periaqueductal gray, locus ceruleus (LC)/subceruleus (SubC), Kölliker–Fuse, magnocellular and lateral tegmental fields, raphe, and the parapyramidal region. Labeled neurons were more abundant on the side of stimulation. In some animals, Fos-labeled cells were also observed in the ventral tegmental area, medial and intermediate vestibular nuclei, dorsal motor nucleus of the vagus, n. tractus solitarii, and retrofacial nucleus in the ventrolateral medulla. Many neurons in the reticular formation were innervated by serotonergic fibers. Numerous locomotor-activated neurons in the parabrachial nuclei and LC/SubC/Kölliker–Fuse were noradrenergic. Few cholinergic neurons within the PPT stained for Fos. In the medulla, serotonergic neurons within the parapyramidal region and the nucleus raphe magnus were positive for Fos. Control animals, not subject to locomotion, showed few Fos-labeled neurons in these areas. The current study provides positive evidence for a role for the CnF in the initiation of locomotion while providing little evidence for the participation of the PPT. The results also show that MLR-evoked locomotion involves the parallel activation of reticular and monoaminergic neurons in the pons/medulla, and provides the anatomical and functional basis for spinal monoamine release during evoked locomotion. Lastly, the results indicate that vestibular, cardiovascular, and respiratory centers are centrally activated during MLR-evoked locomotion. Altogether, the results show a complex pattern of neuromodulatory influences of brainstem neurons by electrical activation of the MLR.
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Affiliation(s)
- Ioan Opris
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Xiaohong Dai
- Department of Physiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, Canada
| | - Dawn M G Johnson
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Francisco J Sanchez
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Luz M Villamil
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Songtao Xie
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Cecelia R Lee-Hauser
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Stephano Chang
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Larry M Jordan
- Department of Physiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, Canada
| | - Brian R Noga
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, United States
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20
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Morphological and electrophysiological properties of serotonin neurons with NMDA modulation in the mesencephalic locomotor region of neonatal ePet-EYFP mice. Exp Brain Res 2019; 237:3333-3350. [PMID: 31720812 DOI: 10.1007/s00221-019-05675-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Accepted: 11/07/2019] [Indexed: 10/25/2022]
Abstract
The mesencephalic locomotor region (MLR) is an essential area for initiation of locomotion. Its functional roles and circuits underlying locomotion have been studied intensively in many species. Studies suggest that cuneiform nucleus and pedunculopontine nucleus (PPN) are two core regions in the MLR for locomotion. However, it remains unclear about cellular components and morphological and intrinsic membrane properties of the neurons in these regions, especially the serotonergic neurons. Using neonatal ePet-EYFP transgenic mice and immunofluorescent technique, we demonstrated existence of 5-HT neurons in the MLR and discovered that 5-HT neurons distributed mainly in the caudal PPN. 5-HT neurons were heterogeneous in MLR and had three types of firing pattern (single spike, phasic and tonic) and two subtypes of morphology (pyramidal and stellate). We measured parameters of 5-HT neurons (n = 35) including resting membrane potential (- 69.2 ± 4.2 mV), input resistance (1410.1 ± 616.9 MΩ), membrane capacitance (36.4 ± 14.9 pF), time constant (49.7 ± 19.4 ms), voltage threshold (- 32.1 ± 7.4 mV), rheobase (21.3 ± 12.4 pA), action potential amplitude (58.9 ± 12.8 mV) and half-width (4.7 ± 1.1 ms), afterhyperpolarization amplitude (23.6 ± 10.4 mV) and half-decay (331.6 ± 157.7 ms). 5-HT neurons were intrinsically different from adjacent non-5-HT neurons and less excitable than them. Hyperpolarization-activated inward currents and persistent inward currents were recorded in 5-HT neurons. NMDA increased excitability of 5-HT neurons, especially the tonic-firing neurons, accompanied with depolarization of membrane potential, hyperpolarization of voltage threshold, reduction of afterhyperpolarization half-decay, and left-shift of frequency-current relationship. This study provided insight into the distribution and properties of 5-HT neurons in the MLR and interaction between serotonergic and glutamatergic modulations.
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21
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Thompson CK, Johnson MD, Negro F, Mcpherson LM, Farina D, Heckman CJ. Exogenous neuromodulation of spinal neurons induces beta-band coherence during self-sustained discharge of hind limb motor unit populations. J Appl Physiol (1985) 2019; 127:1034-1041. [PMID: 31318619 PMCID: PMC6850985 DOI: 10.1152/japplphysiol.00110.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The spontaneous or self-sustained discharge of spinal motoneurons can be observed in both animals and humans. Although the origins of this self-sustained discharge are not fully known, it can be generated by activation of persistent inward currents intrinsic to the motoneuron. If self-sustained discharge is generated exclusively through this intrinsic mechanism, the discharge of individual motor units will be relatively independent of one another. Alternatively, if increased activation of premotor circuits underlies this prolonged discharge of spinal motoneurons, we would expect correlated activity among motoneurons. Our aim is to assess potential synaptic drive by quantifying coherence during self-sustained discharge of spinal motoneurons. Electromyographic activity was collected from 20 decerebrate animals using a 64-channel electrode grid placed on the isolated soleus muscle before and following intrathecal administration of methoxamine, a selective α1-noradrenergic agonist. Sustained muscle activity was recorded and decomposed into the discharge times of ~10-30 concurrently active individual motor units. Consistent with previous reports, the self-sustained discharge of motor units occurred at low mean discharge rates with low-interspike variability. Before methoxamine administration, significant low-frequency coherence (<2 Hz) was observed, while minimal coherence was observed within higher frequency bands. Following intrathecal administration of methoxamine, increases in motor unit discharge rates and strong coherence in both the low-frequency and 15- to 30-Hz beta bands were observed. These data demonstrate beta-band coherence among motor units can be observed through noncortical mechanisms and that neuromodulation of spinal/brainstem neurons greatly influences coherent discharge within spinal motor pools.NEW & NOTEWORTHY The correlated discharge of spinal motoneurons is often used to describe the input to the motor pool. We demonstrate spinal/brainstem neurons devoid of cortical input can generate correlated motor unit discharge in the 15- to 30-Hz beta band, which is amplified through neuromodulation. Activity in the beta band is often ascribed to cortical drive in humans; however, these data demonstrate the capability of the mammalian segmental motor system to generate and modulate this coherent state of motor unit discharge.
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Affiliation(s)
| | | | - Francesco Negro
- 3Department of Clinical and Experimental Sciences, Research Centre for Neuromuscular Function and Adapted Physical Activity “Teresa Camplani,” Università degli Studi di Brescia, Bescia, Italy
| | | | - Dario Farina
- 5Department of Bioengineering, Imperial College London, London, United Kingdom
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Grillner S, El Manira A. Current Principles of Motor Control, with Special Reference to Vertebrate Locomotion. Physiol Rev 2019; 100:271-320. [PMID: 31512990 DOI: 10.1152/physrev.00015.2019] [Citation(s) in RCA: 232] [Impact Index Per Article: 46.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vertebrate control of locomotion involves all levels of the nervous system from cortex to the spinal cord. Here, we aim to cover all main aspects of this complex behavior, from the operation of the microcircuits in the spinal cord to the systems and behavioral levels and extend from mammalian locomotion to the basic undulatory movements of lamprey and fish. The cellular basis of propulsion represents the core of the control system, and it involves the spinal central pattern generator networks (CPGs) controlling the timing of different muscles, the sensory compensation for perturbations, and the brain stem command systems controlling the level of activity of the CPGs and the speed of locomotion. The forebrain and in particular the basal ganglia are involved in determining which motor programs should be recruited at a given point of time and can both initiate and stop locomotor activity. The propulsive control system needs to be integrated with the postural control system to maintain body orientation. Moreover, the locomotor movements need to be steered so that the subject approaches the goal of the locomotor episode, or avoids colliding with elements in the environment or simply escapes at high speed. These different aspects will all be covered in the review.
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Affiliation(s)
- Sten Grillner
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Jean-Xavier C, Perreault MC. Influence of Brain Stem on Axial and Hindlimb Spinal Locomotor Rhythm Generating Circuits of the Neonatal Mouse. Front Neurosci 2018; 12:53. [PMID: 29479302 PMCID: PMC5811543 DOI: 10.3389/fnins.2018.00053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Accepted: 01/23/2018] [Indexed: 12/18/2022] Open
Abstract
The trunk plays a pivotal role in limbed locomotion. Yet, little is known about how the brain stem controls trunk activity during walking. In this study, we assessed the spatiotemporal activity patterns of axial and hindlimb motoneurons (MNs) during drug-induced fictive locomotor-like activity (LLA) in an isolated brain stem-spinal cord preparation of the neonatal mouse. We also evaluated the extent to which these activity patterns are affected by removal of brain stem. Recordings were made in the segments T7, L2, and L5 using calcium imaging from individual axial MNs in the medial motor column (MMC) and hindlimb MNs in lateral motor column (LMC). The MN activities were analyzed during both the rhythmic and the tonic components of LLA, the tonic component being used as a readout of generalized increase in excitability in spinal locomotor networks. The most salient effect of brain stem removal was an increase in locomotor rhythm frequency and a concomitant reduction in burst durations in both MMC and LMC MNs. The lack of effect on the tonic component of LLA indicated specificity of action during the rhythmic component. Cooling-induced silencing of the brain stem reproduced the increase in rhythm frequency and accompanying decrease in burst durations in L2 MMC and LMC, suggesting a dependency on brain stem neuron activity. The work supports the idea that the brain stem locomotor circuits are operational already at birth and further suggests an important role in modulating trunk activity. The brain stem may influence the axial and hindlimb spinal locomotor rhythm generating circuits by extending their range of operation. This may represent a critical step of locomotor development when learning how to walk in different conditions and environments is a major endeavor.
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Affiliation(s)
| | - Marie-Claude Perreault
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
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Jean-Xavier C, Sharples SA, Mayr KA, Lognon AP, Whelan PJ. Retracing your footsteps: developmental insights to spinal network plasticity following injury. J Neurophysiol 2017; 119:521-536. [PMID: 29070632 DOI: 10.1152/jn.00575.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
During development of the spinal cord, a precise interaction occurs between descending projections and sensory afferents, with spinal networks that lead to expression of coordinated motor output. In the rodent, during the last embryonic week, motor output first occurs as regular bursts of spontaneous activity, progressing to stochastic patterns of episodes that express bouts of coordinated rhythmic activity perinatally. Locomotor activity becomes functionally mature in the 2nd postnatal wk and is heralded by the onset of weight-bearing locomotion on the 8th and 9th postnatal day. Concomitantly, there is a maturation of intrinsic properties and key conductances mediating plateau potentials. In this review, we discuss spinal neuronal excitability, descending modulation, and afferent modulation in the developing rodent spinal cord. In the adult, plastic mechanisms are much more constrained but become more permissive following neurotrauma, such as spinal cord injury. We discuss parallel mechanisms that contribute to maturation of network function during development to mechanisms of pathological plasticity that contribute to aberrant motor patterns, such as spasticity and clonus, which emerge following central injury.
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Affiliation(s)
- C Jean-Xavier
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
| | - S A Sharples
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Neuroscience, University of Calgary , Calgary, Alberta , Canada
| | - K A Mayr
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Neuroscience, University of Calgary , Calgary, Alberta , Canada
| | - A P Lognon
- Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
| | - P J Whelan
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
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Kim LH, Sharma S, Sharples SA, Mayr KA, Kwok CHT, Whelan PJ. Integration of Descending Command Systems for the Generation of Context-Specific Locomotor Behaviors. Front Neurosci 2017; 11:581. [PMID: 29093660 PMCID: PMC5651258 DOI: 10.3389/fnins.2017.00581] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 10/04/2017] [Indexed: 11/23/2022] Open
Abstract
Over the past decade there has been a renaissance in our understanding of spinal cord circuits; new technologies are beginning to provide key insights into descending circuits which project onto spinal cord central pattern generators. By integrating work from both the locomotor and animal behavioral fields, we can now examine context-specific control of locomotion, with an emphasis on descending modulation arising from various regions of the brainstem. Here we examine approach and avoidance behaviors and the circuits that lead to the production and arrest of locomotion.
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Affiliation(s)
- Linda H Kim
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada
| | - Sandeep Sharma
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
| | - Simon A Sharples
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada
| | - Kyle A Mayr
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada
| | - Charlie H T Kwok
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
| | - Patrick J Whelan
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
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