Scientists from Denmark and the United States showed that the giant neurons of the nucleus of the brain stem control the asymmetrical rhythmic movements of the mice. During stimulation of the left giant cell nucleus animals were turned to the left: the activity of the muscles of the left legs down and the muscle tone of the left half of the body is increased. Previously, the mechanism of desynchronization of skeletal muscles at the level of the brainstem was unclear. A study published in the journal Nature Neuroscience.
Sequence of muscle contraction during rhythmic movements (e.g. walking) control motor neurons of the spinal cord. The signal for the beginning or end of the movement and its speed comes from the higher parts of the nervous system. Region and the neuronsthat are responsible for the appropriate command found in the brainstem, the path of initiation are very well studied.
If you stimulate the area of the brain stem in which there is the command to start the movement only on one side (e.g. right), the animal will go forward and will be symmetrically tragic deaths. This bilateral synchronization is possible thanks to the many comissural fibers (extending from the left side of the brain stem in a similar area on the right). They transfer the excitation to the second half of the brain, and the symmetric motion is obtained.
Even if one-sided damage of corticospinal tract (the path by which motor commands descend from the cerebral cortex to the spinal cord), posture and movements of the animal will remain symmetrical. The question arises — what happens if you need to turn right or left? For this you need to resynchronizing the work of neurons. What mechanisms provide asymmetrical commands for the muscles is not clear.
A group of scientists under the leadership of OLE Kina (Ole Kiehn) from the University of Copenhagen have suggested that asymmetric motion can run the giant neurons of the reticular nucleus. For a start, the researchers made sure that the projections of these neurons descend in the spinal cord ipsilateral (cells only Innervate the same half of the brain) is a condition necessary to launch unilateral movements. In giant cell nucleus of mice on the one hand introduced the label is a virus that moved aksonam neurons towards their targets. The virus has attached fluorescent molecule, and its distribution could be observed with a microscope.
Projection neurons giant cell nuclei do down the ipsilateral, about 80% of these cells formed synapses in the corresponding half of the spinal cord (p < 0.001). Targets of nerve cells were not motor neurons directly trigger the contraction of the muscles, and the intercalated neurons of the rear horns of the spinal cord.