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The Mysterious Power of the Central Pattern Generator: How to Generate Rhythm Without Brain Instructions?
Central pattern generators (CPGs) are self-organizing biological neural circuits that produce rhythmic output in the absence of rhythmic input.
With the deepening of the scientific understanding of the operation of the nervous system, central pattern generators (CPGs) have gradually attracted the interest of many researchers. Not only can these neural circuits control basic movements such as walking, swimming, breathing, and chewing, they can also operate without the intervention of higher brain regions, effectively demonstrating their unique rhythm-generating capabilities. Under certain circumstances that require adjustment at the same time, the resilience and flexibility displayed by CPGs make it possible to adapt to changes in the external environment, thereby affecting the diversity of organism behaviors.
Physiological basis of central pattern generator
The study points out that neurons in CPGs have different intrinsic membrane properties, and this diversity is key to their ability to generate rhythms. For example, some neurons are capable of generating bursts of action potentials, while others have stable bottom cell potentials that allow them to respond to depolarizing pulses or even restart activity after inhibition has ended. This restarting after inhibition is called “inhibitory rebound” and is a common property of these neurons.
Rhyme generation mechanism
Rhythm generation in CPG networks relies on the intrinsic properties of neurons and their synaptic connections. There are two main mechanisms for rhythm generation, namely master metronome/follower neurons and reciprocal inhibition. In the master metronome mechanism, one or more neurons act as core oscillators, pushing other neurons into cyclic rhythmic patterns. Reciprocal inhibition is a key component of action. Although these neurons are not active in isolation, they can produce alternating activity patterns through inhibitory connections between each other.
The role of neuromodulation
In the face of changes in the internal and external environment, the behavior of organisms must continuously adapt. In this process, neuromodulation of central pattern generators is crucial. Neuromodulation can not only change the functional configuration of CPG, but also change the role of neurons in the network. For example, the swimming response of eels can be influenced by hormones or other neuromodulatory substances that strengthen synaptic connections between neurons, making movement choices more flexible.
The impact of sensory feedback
Although central pattern generator theory asserts that basic rhythmicity and pattern generation are centrally generated, CPGs can also respond to sensory feedback to behaviorally alter patterns appropriately. This change in pattern may be cooperative, requiring the preservation of some coordination relationship with other parts of the behavioral cycle. For example, if you put a small stone in your right shoe while walking, this will change the entire gait, even if the stimulus only exists when the right foot is standing.
Functionality of the Central Pattern Generator
The functions of the central pattern generator are diverse. They play a key role in movement, breathing and other similar mechanisms, including the control of gait, swimming, and rhythm generation. Since 1911, scientists have begun to recognize the importance of the spinal cord in the control of rhythmic movement. Through experiments with locusts and other vertebrates, researchers have begun to extensively explore the role of the central pattern generator in the spinal cord, particularly in generating locomotor patterns during walking and swimming.
In detailed studies, for example, the leech's spinal cord can continue to produce regular movements even after the brain is removed, which provides strong evidence for the mechanism of CPG. At the same time, these research results not only promote the understanding of biological movement, but also create new possibilities for the design and engineering applications of future robots.
Research on central pattern generators not only focuses on the understanding of biological motion, but may also bring revolutionary progress in fields such as neurological rehabilitation and robot design. We have to think about, with the development of science and technology, can humans design a biological-like central pattern generator to improve the movement performance of machines?
