Movement is an essential part of our daily lives, and disorders of the motor system, such as spasticity, amyotrophic lateral sclerosis, and spinal cord injury are particularly debilitating for individuals. Simple rhythmic movements, such as walking and breathing, have constituted models for fundamental aspects of the motor system. Despite extensive investigations, the connectivity of the network responsible for generating motor activity remains unknown.
Scientists in a new study studied the network between nerve and muscle cells in turtles and found that most movements are generated in the spinal cord. The offers unique insight on into how movements are created and maintained. What’s more, it may imply treatments like ALS and spinal cord injuries.
Associate Professor and Head of Research Rune W. Berg from the Department of Neuroscience at the University of Copenhagen said, “Naturally, there is a conversation with high-ranking parts of the nervous system, such as the cerebrum, but there are also reflexes that simply stem from the back.”
For this study, scientists used electrodes to consider the spinal cord reflex of turtles when they scratched themselves with one hind leg. A reflex likewise found in dogs, cats, and several other mammals.
Similarly, humans are equipped with a variety of spinal reflexes. And, in terms of evolution, humans are different from the turtle.
According to scientists, there are many underlying mechanisms are same. Thus when the turtle rhythmically scratches itself using crawl movements from its hind leg, the fireworks of lightning-quick neurological impulses that are set off inside the shell are not far from the mechanisms that also trigger our muscles.
Assistant Professor Henrik Lindén from the research group behind the study said, “It has been a common assumption that the activation of muscle neurons originates from some command center that sends a signal to many cells at one time.”
“Because the origin of movement has been difficult to find, it has long been assumed that it is a small core that sets the pace. Like some metronome. But our data has shown that it may be a large network.”
To check if it is a matter of commands or an extensive network, scientists compared the relatively quiet rhythm of the turtle’s movement with the rapid neurological impulses from the spine.
Surprisingly, the measurements demonstrated no proof of connection – and subsequently no evidence that the neurological signal in various cells ought to have originated from the same source, which would undoubtedly have been the case if it had been a command center that signaled to numerous cells simultaneously.
Now, scientists believe that neurological signals originate from a significant, scattered network of cells, each of which sends signals to only a few other cells — a result which the group has subsequently replicated in computer models of a simulated, simple nervous system.
Rune W. Berg said, “If we do not know enough about the network and how it works, we grope a bit in the dark when it comes to treatment. Conversely, once we gain insight into the principles behind the distribution of the network, and which cell types are important, we can better put the treatment of neurological disorders on the right track.”
Now, scientists are planning to continue the mapping of the scattered neurological network with optical measurements that allow them to track the activity simultaneously over a larger area.