Neural Circuits: Spinal Cord, Retina, Invertebrate Systems

2009 ◽  
pp. 114-128
Author(s):  
Gordon M. Shepherd
Keyword(s):  
Spinal Cord ◽  
Neural Circuits

scholarly journals Multiple Functions of Draxin/Netrin-1 Signaling in the Development of Neural Circuits in the Spinal Cord and the Brain

2021 ◽  
Vol 15 ◽  
Author(s):  
Giasuddin Ahmed ◽  
Yohei Shinmyo
Keyword(s):  
Spinal Cord ◽  
Axon Guidance ◽  
Neural Circuits ◽  
Neural Circuit ◽  
Deleted In Colorectal Cancer ◽  
Guidance Cue ◽  
Thalamocortical Projections ◽  
The Central Nervous System ◽  
Circuit Formation ◽  
The Brain

Axon guidance proteins play key roles in the formation of neural circuits during development. We previously identified an axon guidance cue, named draxin, that has no homology with other axon guidance proteins. Draxin is essential for the development of various neural circuits including the spinal cord commissure, corpus callosum, and thalamocortical projections. Draxin has been shown to not only control axon guidance through netrin-1 receptors, deleted in colorectal cancer (Dcc), and neogenin (Neo1) but also modulate netrin-1-mediated axon guidance and fasciculation. In this review, we summarize the multifaceted functions of draxin and netrin-1 signaling in neural circuit formation in the central nervous system. Furthermore, because recent studies suggest that the distributions and functions of axon guidance cues are highly regulated by glycoproteins such as Dystroglycan and Heparan sulfate proteoglycans, we discuss a possible function of glycoproteins in draxin/netrin-1-mediated axon guidance.

scholarly journals The Effect of Limb Position on a Static Knee Extension Task can be Explained with a Simple Spinal Cord Circuit Model

2021 ◽  
Author(s):  
Gareth James Richard York ◽  
Hugh Osborne ◽  
Piyanee Sriya ◽  
Sarah Astill ◽  
Marc de Kamps ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Muscle Activity ◽  
Neural Circuits ◽  
Rectus Femoris ◽  
Knee Extension ◽  
Afferent Input ◽  
Muscle Synergy ◽  
Knee Angle ◽  
Activation Patterns ◽  
Isometric Knee Extension

The influence of proprioceptive feedback on muscle activity during isometric tasks is the subject of conflicting studies. We performed an isometric knee extension task experiment based on two common clinical tests for mobility and flexibility. The task was carried out at four pre-set angles of the knee and we recorded from five muscles for two different hip positions. We applied muscle synergy analysis using non-negative matrix factorisation on surface electromyograph recordings to identify patterns in the data which changed with internal knee angle, suggesting a link between proprioception and muscle activity. We hypothesised that such patterns arise from the way proprioceptive and cortical signals are integrated in neural circuits of the spinal cord. Using the MIIND neural simulation platform, we developed a computational model based on current understanding of spinal circuits with an adjustable afferent input. The model produces the same synergy trends as observed in the data, driven by changes in the afferent input. In order to match the activation patterns from each knee angle and position of the experiment, the model predicts the need for three distinct inputs: two to control a non-linear bias towards the extensors and against the flexors, and a further input to control additional inhibition of rectus femoris. The results show that proprioception may be involved in modulating muscle synergies encoded in cortical or spinal neural circuits.

Reconstruction and Tuning of Neural Circuits for Locomotion After Spinal Cord Injury

2014 ◽  
pp. 139-148
Author(s):  
Toru Ogata ◽  
Noritaka Kawashima ◽  
Kimitaka Nakazawa ◽  
Masami Akai
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Neural Circuits ◽  
Cord Injury

scholarly journals Crossed activation of thoracic trunk motoneurons by medullary reticulospinal neurons

2019 ◽  
Vol 122 (6) ◽  
pp. 2601-2613
Author(s):  
Brandon K. LaPallo ◽  
Andrea Giorgi ◽  
Marie-Claude Perreault
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Brain Stem ◽  
Neural Circuits ◽  
Single Cells ◽  
The Other ◽  
Medullary Reticular Formation ◽  
Functional Connections ◽  
Cord Injury ◽  
The Brain

Activation of contralateral muscles by supraspinal neurons, or crossed activation, is critical for bilateral coordination. Studies in mammals have focused on the neural circuits that mediate cross activation of limb muscles, but the neural circuits involved in crossed activation of trunk muscles are still poorly understood. In this study, we characterized functional connections between reticulospinal (RS) neurons in the medial and lateral regions of the medullary reticular formation (medMRF and latMRF) and contralateral trunk motoneurons (MNs) in the thoracic cord (T7 and T10 segments). To do this, we combined electrical microstimulation of the medMRF and latMRF and calcium imaging from single cells in an ex vivo brain stem-spinal cord preparation of neonatal mice. Our findings substantiate two spatially distinct RS pathways to contralateral trunk MNs. Both pathways originate in the latMRF and are midline crossing, one at the level of the spinal cord via excitatory descending commissural interneurons (reticulo-commissural pathway) and the other at the level of the brain stem (crossed RS pathway). Activation of these RS pathways may enable different patterns of bilateral trunk coordination. Possible implications for recovery of trunk function after stroke or spinal cord injury are discussed. NEW & NOTEWORTHY We identify two spatially distinct reticulospinal pathways for crossed activation of trunk motoneurons. Both pathways cross the midline, one at the level of the brain stem and the other at the level of the spinal cord via excitatory commissural interneurons. Jointly, these pathways provide new opportunities for repair interventions aimed at recovering trunk functions after stroke or spinal cord injury.

scholarly journals Clinically Relevant Levels of 4-Aminopyridine Strengthen Physiological Responses in Intact Motor Circuits in Rats, Especially After Pyramidal Tract Injury

2017 ◽  
Vol 31 (4) ◽  
pp. 387-396 ◽  
Author(s):  
Anil Sindhurakar ◽  
Asht M. Mishra ◽  
Disha Gupta ◽  
Jennifer F. Iaci ◽  
Tom J. Parry ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Stimulation ◽  
Neural Circuits ◽  
Pyramidal Tract ◽  
Cervical Spinal Cord ◽  
Physiological Responses ◽  
Motor Circuits ◽  
Improve Motor Function ◽  
Drug Plasma ◽  
Brain And Spinal Cord

Background. 4-Aminopyridine (4-AP) is a Food and Drug Administration–approved drug to improve motor function in people with multiple sclerosis. Preliminary results suggest the drug may act on intact neural circuits and not just on demyelinated ones. Objective. To determine if 4-AP at clinically relevant levels alters the excitability of intact motor circuits. Methods. In anesthetized rats, electrodes were placed over motor cortex and the dorsal cervical spinal cord for electrical stimulation, and electromyogram electrodes were inserted into biceps muscle to measure responses. The motor responses to brain and spinal cord stimulation were measured before and for 5 hours after 4-AP administration both in uninjured rats and rats with a cut lesion of the pyramidal tract. Blood was collected at the same time as electrophysiology to determine drug plasma concentration with a goal of 20 to 100 ng/mL. Results. We first determined that a bolus infusion of 0.32 mg/kg 4-AP was optimal: it produced on average 61.5 ± 1.8 ng/mL over the 5 hours after infusion. This dose of 4-AP increased responses to spinal cord stimulation by 1.3-fold in uninjured rats and 3-fold in rats with pyramidal tract lesion. Responses to cortical stimulation also increased by 2-fold in uninjured rats and up to 4-fold in the injured. Conclusion. Clinically relevant levels of 4-AP strongly augment physiological responses in intact circuits, an effect that was more robust after partial injury, demonstrating its broad potential in treating central nervous system injuries.

Optical demonstration of the functional formation of neural circuits in the embryonic chick spinal cord slice

1998 ◽  
Vol 31 ◽  
pp. S115
Author(s):  
Yoshiyasu Arai ◽  
Yoko Momose-Sato ◽  
Katsushige Sato ◽  
Kohtaro Kamino
Keyword(s):  
Spinal Cord ◽  
Neural Circuits ◽  
Embryonic Chick ◽  
Spinal Cord Slice ◽  
Chick Spinal Cord

An update on the spinal and peripheral pathways of pain signalling

e-Neuroforum ◽  
2017 ◽  
Vol 23 (3) ◽  
Author(s):  
Stefan G. Lechner
Keyword(s):  
Spinal Cord ◽  
Sensory Neurons ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Neural Circuits ◽  
Sensory Information ◽  
Brain Regions ◽  
Sensory Afferents ◽  
Different Types ◽  
Functionally Diverse

AbstractPainful or potentially tissue-damaging stimuli are detected by primary sensory afferents that innervate the skin as well as internal tissues. The neurons that give rise to sensory afferents are located in the dorsal root ganglia (DRG) and transmit sensory information to the spinal cord where it is processed and further relayed to higher brain regions to ultimately generate the perception of pain. Both the DRGs as well as the spinal cord comprise a variety of morphologically, molecularly and functionally diverse neurons. The objective of this review is to provide an overview of the different types of sensory neurons and their proposed role in pain signalling. Moreover, I will discuss how pain related sensory information is processed in the dorsal horn of the spinal cord with an emphasis on recently delineated neural circuits that mediate pain hypersensitivity in the setting of nerve injury and inflammation.

Neurogenesis, control, and functional significance of gasping

1990 ◽  
Vol 68 (4) ◽  
pp. 1305-1315 ◽  
Author(s):  
W. M. St John
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Neural Circuits ◽  
Pattern Generator ◽  
Backup System ◽  
Neuronal Mechanisms ◽  
Inspiratory Activity ◽  
Respiratory Rhythms ◽  
Similar Elements ◽  
Stem Segments

Gasps are frequently the first and last breaths of life. Gasping, which is generated by intrinsic medullary mechanisms, differs fundamentally from other automatic ventilatory patterns. A region of the lateral tegmental field of the medulla is critical for the neurogenesis of the gasp but has no role in eupnea. Neuronal mechanisms in separate brain stem regions may be responsible for the neurogenesis of different ventilatory patterns. This hypothesis is supported by the recording of independent respiratory rhythms simultaneously from isolated brain stem segments. Data from fetal and neonatal animals also support gasping and eupnea being generated by separate mechanisms. Gasping may represent the output of a simple but rugged pattern generator that functions as a backup system until the control system for eupnea is developed. Pacemaker elements are hypothesized as underlying the onset of inspiratory activity in gasping. Similar elements, in a different brain stem region, may be responsible for the onset of the eupneic inspiration with neural circuits involving the pons, the medulla, and the spinal cord serving to shape efferent respiratory-modulated neural discharges.

scholarly journals Distinct sensorimotor feedback loops for dynamic and static control of primate precision grip

2019 ◽  
Author(s):  
Tomomichi Oya ◽  
Tomohiko Takei ◽  
Kazuhiko Seki
Keyword(s):  
Spinal Cord ◽  
Motor Cortex ◽  
Neural Circuits ◽  
Precision Grip ◽  
Electromyographic Activity ◽  
Dexterous Hand ◽  
Neuronal Coherence ◽  
Muscle Actions ◽  
Bidirectional Interactions ◽  
Sensorimotor Feedback

AbstractVolitional limb motor control involves dynamic and static muscle actions. It remains elusive how such distinct actions are controlled through separated or shared neural circuits. Here we explored the potential separation for dynamic and static controls in the primate hand actions, by investigating the neuronal coherence between local 1eld potentials (LFPs) of the spinal cord and the forelimb electromyographic activity (EMGs), and LFPs of the motor cortex and the EMGs during the performance of a precision grip in macaque monkeys. We observed the emergence of beta-range coherence with EMGs at spinal cord and motor cortex in the separated phases; spinal coherence during the grip phase and cortical coherence during the hold phase. Further, both of the coherence were influenced by bidirectional interactions with reasonable latencies as beta oscillatory cycles. These results indicate that dedicated feedback circuits comprising spinal and cortical structures underlie dynamic and static controls of dexterous hand actions.

scholarly journals Sexual Experience Induces the Expression of Gastrin-Releasing Peptide and Oxytocin Receptors in the Spinal Ejaculation Generator in Rats

2021 ◽  
Vol 22 (19) ◽  
pp. 10362
Author(s):  
Takumi Oti ◽  
Ryota Ueda ◽  
Ryoko Kumagai ◽  
Junta Nagafuchi ◽  
Takashi Ito ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Sexual Activity ◽  
Neural Circuits ◽  
Sexual Experience ◽  
Lumbar Spinal Cord ◽  
Gastrin Releasing Peptide ◽  
Oxytocin Receptors ◽  
Male Sexual Function ◽  
Lumbar Spinal ◽  
The Brain

Male sexual function in mammals is controlled by the brain neural circuits and the spinal cord centers located in the lamina X of the lumbar spinal cord (L3–L4). Recently, we reported that hypothalamic oxytocin neurons project to the lumbar spinal cord to activate the neurons located in the dorsal lamina X of the lumbar spinal cord (dXL) via oxytocin receptors, thereby facilitating male sexual activity. Sexual experiences can influence male sexual activity in rats. However, how this experience affects the brain–spinal cord neural circuits underlying male sexual activity remains unknown. Focusing on dXL neurons that are innervated by hypothalamic oxytocinergic neurons controlling male sexual function, we examined whether sexual experience affects such neural circuits. We found that >50% of dXL neurons were activated in the first ejaculation group and ~30% in the control and intromission groups in sexually naïve males. In contrast, in sexually experienced males, ~50% of dXL neurons were activated in both the intromission and ejaculation groups, compared to ~30% in the control group. Furthermore, sexual experience induced expressions of gastrin-releasing peptide and oxytocin receptors in the lumbar spinal cord. This is the first demonstration of the effects of sexual experience on molecular expressions in the neural circuits controlling male sexual activity in the spinal cord.

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