summary: Researchers have made progress in understanding how stick insects control their leg muscles while walking, challenging previous assumptions about motor neuron activation. Their study revealed that neurons that activate depressor muscles in stick insect legs receive unique rhythmic stimulation, unlike other leg muscles.
These findings highlight the role of the central pattern generator (CPG) in the production of rhythmic movements and suggest that its influence on motor neurons is limited to each group of neurons. This research not only increases our understanding of animal locomotion, but also underscores the complexity of neural networks in coordinating walking movements.
Key facts:
source: University of Cologne
In a new study, scientists from the University of Cologne gained new insights into the rhythmic activation mechanisms of nerve cells (neurons) in stick insects that control leg muscles during walking.
The researchers showed that neurons that activate depressor muscles in the legs are excited rhythmically, unlike neurons in other leg muscles. Until now, it was assumed that all so-called motor neurons were activated in the same way by the central nervous tissue.
They found that all but one of the leg muscle groups of motor neurons received the same drive from the network: rhythmic inhibitory signals from the CPG. Credit: Neuroscience News
The research, entitled “Synaptic drive of the central pattern-generating network of walking insect leg motoneurons specific to a population of motoneurons,” was published in the journal Current biology.
A research team at UCLA is investigating the neural bases underlying the generation of movement in animals, particularly basic motor activities such as walking.
For this purpose, the team led by Prof. Ansgar Boschges analyzed insects, among other things, because the requirements of the nervous system regarding the generation and control of walking movements are very similar in the animal kingdom.
In many animals, for example, there are networks in the central nervous system that underlie the formation of rhythmic activity patterns for various forms of movement, whether for rhythmic locomotor activities such as running, swimming, crawling, and flying, or for vegetative functions. Like breathing.
This highly specialized network is called a central pattern generator (CPG). It produces rhythmic motor activity of muscles to move by interacting with information received from sensory organs and neurons called proprioceptors; Proprioceptors report movement and inform the central nervous system. When walking, they fall on the insect’s feet.
The tissue does this by activating the so-called motor neurons that innervate the muscles. Until now, these motor neurons were assumed to have the same effect on all the motor neurons they target.
In their new study, Angelina Roth, Dr. Charalambos Mantziaris, and Professor Boschges refuted the assumptions about the locomotor activity of insects.
In their experiments, the scientists pharmacologically activated CPGs in the central nervous system of stick insects Carausius Maurusus He investigated its effect on the motor neurons that innervate his leg muscles.
They found that all but one of the leg muscle groups of motor neurons received the same drive from the network: rhythmic inhibitory signals from the CPG.
Only motor neurons, which innervate the gastrocnemius depressor muscle, are controlled by phasic excitatory drive. Interestingly, the gastrocnemius depressor muscle is the insect muscle responsible for generating leg posture during any walking condition – regardless of whether the animal is running up or down horizontally, on the ceiling, or on a branch.
“The rhythmic excitation and specific activation of motor neuron populations by the CPG may serve to ensure the precise timing of depressor muscle contractions and thus the initiation and stabilization of the stance phase,” explains Professor Boschges.
Financing: This study was funded by the German Research Foundation (DFG).
About this neuroscience research news
author: Eva Schiesler
source: University of Cologne
communication: Eva Schiesler – University of Cologne
picture: Image credited to Neuroscience News
Original search: Open access.
“Synaptic drive of the central pattern-generating network of walking insect leg motoneurons is specific to a population of motoneurons“By Ansgar Boschges et al. Current biology
summary
Synaptic drive of the central pattern-generating network of walking insect leg motoneurons is specific to a population of motoneurons
Highlight
- The synaptic drive of the motoneuron stalk CPG network is assembly specific
- Protractor, connective tissue, and lever motor neurons receive phase inhibitory drive
- Specifically, depressor motor neurons receive phasic excitatory impulses
summary
Rhythmic motor activities, such as flying, swimming, or walking, result from interactions between higher centers in the central nervous system, which initiate, maintain, and modulate task-specific motor activity, and central pattern-generating neural circuits (CPGs). ) that can generate virtual rhythmic motor output and, ultimately, feedback from the sense organs that modulate basic motor activity towards their function.
In this context, CPGs provide phasic synaptic drive to motor neurons (MN), thereby supporting the generation of rhythmic activity for movement.
We analyzed the synaptic impulses received by leg MNs supplying the three major leg joints of the CPG in pharmacologically activated and desmoplastic stick insect preparations (Carausius Maurusus). We have shown that the motor CPG models the tonic activity of five of the six leg MNs via phasic inhibitory synaptic drive.
These are the antagonistic MN bundles that innervate the thoracic-trochanteric joint and the tibiofemoral joint as well as the levator MN bundle that innervates the coxa-trochanteric joint (CTr). In contrast, the rhythmic activity of MN depressors via feeding at the CTR joint was found to depend primarily on phasic excitatory impulses.
This difference is likely related to the important role of depressor muscles in producing foot posture during any walking condition. Thus, our results provide evidence for the existence of qualitatively different mechanisms for generating rhythmic activity between MN populations within the same motor system.
2024-02-09 02:00:52
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