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One of the most common misconceptions about the primary motor cortex is that the map of the body is cleanly segregated. Yet it is not a map of individuated muscles or even individuated body parts. The map contains considerable overlap. This overlap increases in more anterior regions of the primary motor cortex.
It is believed that as an animal learns a complex movement repertoire, the motor cortex gradually comes to coordinate among muscles. [65] [66] Map of the body in the human brain. The clearest example of the coordination of muscles into complex movement in the motor cortex comes from the work of Graziano and colleagues on the monkey brain.
Glutamate released from the upper motor neurons triggers depolarization in the lower motor neurons in the anterior grey column, which in turn causes an action potential to propagate the length of the axon to the neuromuscular junction where acetylcholine is released to carry the signal across the synaptic cleft to the postsynaptic receptors of the muscle cell membrane, signaling the muscle to ...
Prior to this, the only adult animal to have its brain entirely reconstructed was the nematode Caenorhabditis elegans, but the fruit fly brain map is the first "complete map of any complex brain", according to Murthy, one of the researchers involved. [2]
Multiple topographic maps is a feature that is advantageous because it allows maps of different sizes that would accommodate varying levels of acuity and details in signals. A more detailed map has more neurons that would take up more area than a more global map, which would require fewer connections. [14]
A single motor neuron may innervate many muscle fibres and a muscle fibre can undergo many action potentials in the time taken for a single muscle twitch. Innervation takes place at a neuromuscular junction and twitches can become superimposed as a result of summation or a tetanic contraction. Individual twitches can become indistinguishable ...
Brain at the U.S. National Library of Medicine Medical Subject Headings (MeSH) (view tree for regions of the brain) BrainMaps.org; BrainInfo (University of Washington) "Brain Anatomy and How the Brain Works". Johns Hopkins Medicine. 14 July 2021. "Brain Map". Queensland Health. 12 July 2022.
Penfield and Welch [18] in 1951 first described SMA in the monkey brain and the human brain as a representation of the body on the medial wall of the hemisphere. Woolsey and colleagues [19] in 1952 confirmed SMA in the monkey brain, describing it as a rough somatotopic map with the legs in a posterior location and the face in an anterior location.