Introducing the brain: learning new motor skills (Introduction)

by David Turell , Wednesday, February 09, 2022, 20:31 (806 days ago) @ David Turell

Specialized area is found:

https://medicalxpress.com/news/2022-02-newly-brain-circuit-motor.html

"'We were particularly interested in two major types of cells in the cortex, known as IT (intratelencephalic) and PT (pyramidal tract) neurons," said Nicolas Morgenstern, the first author of this study which was developed in the group at the time led by Rui Costa, at Champalimaud Foundation, in Lisbon, Portugal. "Both IT and PT cells send signals from the cortex to another area buried deeper in the brain, called the striatum. These 'cortico-striatal' connections (i.e. connections from the cortex to the striatum) are very important for motor learning and have been implicated in movement disorders like Parkinson's disease."

"This is where the third major character in our story appears: the spiny projection neurons (SPNs), which make up 95% of the neurons in the striatum. SPNs are directly contacted by both IT and PT cells. "We wanted to understand the different roles of IT and PT cells in this brain circuit, which is so important for motor learning and behavior."

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"while recording the activity of neurons in vitro, the authors uncovered a new corticostriatal pathway. In this pathway, a fourth principal player emerged: striatal cholinergic interneurons (ChIs). Acting as the "middle-man" in a three-person relay, ChIs in the striatum receive input from PT cells and, in turn, excite SPNs. "We found that PT cells preferentially connect to ChIs, which indirectly activated SPNs," said Morgenstern.

"Using pharmacological methods, the authors were able to show precisely how ChIs excite SPNs. When activated by PT neurons, ChIs release a neurotransmitter called acetylcholine (ACh). Neurotransmitters are chemical messengers that transmit signals from one cell to another. When ChIs release ACh, they cause the nerve fibers of cells nearby to excite SPNs.

"These results demonstrate that SPNs are excited twice: first, through the known direct routes (IT→SPN and PT→SPN), and second, through this previously unknown indirect circuit (PT→ChI→SPN), which amplifies the initial excitation. What is the purpose of this double excitation? The authors speculate that the direct IT→SPN connection initially prepares specific motor actions, while the PT→ChI→SPN connection subsequently triggers movement.

"'Besides movement execution," notes Nicolas Morgenstern, "this second excitatory phase mediated by PT neurons could be important for inducing long-lasting changes in the strength of specific connections, via the neurotransmitter ACh. This could be important for behavior, since learning happens when connections between brain cells change'."
(my bold)

Comment: the final paragraph is a key point. We know practice makes perfect and this is how the brain does it. Over the years we have invented all sorts of activities our 315,000 years old ancestors had no idea about doing; think sports for example. Our brain came fully prepared for these new activities. But dhw thinks there was no anticipation by God arranged for in our new big brain..