Simplified schematic illustration of the motor management system thought of on this examine, and the hypotheses about how it’s utilized in response to completely different challenges. Credit score: Mizes et al.
The motor cortex is part of the mammalian mind and is thought to help the planning and management of voluntary physique actions. Some previous neuroscience research, nonetheless, discovered that the motor cortex might not be needed for executing some realized expertise and motor sequences, elevating the query of when and the way it’s recruited.
Researchers at Harvard College not too long ago carried out a examine on rats to handle this query. Their paper, revealed in Nature Neuroscience, exhibits that the involvement of the motor cortex in motor sequence execution will depend on the extent to which a given activity requires flexibility.
“We previously found that motor cortex is not necessary to generate highly automatized learned skills or motor sequences,” Bence P. Ölveczky, senior creator of the paper, instructed Medical Xpress.
“This was a departure from common wisdom, which assumed that learned motor skills are stored in the motor cortex. If this is the case, however, when is the motor cortex necessary for generating motor sequences?”
Constructing on their earlier analysis, the researchers determined to discover whether or not and the way the motor cortex is concerned within the technology of sequences in response to sensory cues. They hypothesized that this mind area conveys info processed in cortical circuits (e.g., the which means of a given stimulus) to subcortical motor facilities within the mind.
To check this speculation, Ölveczky and his colleagues carried out a collection of experiments involving grownup rats. These rats had been skilled to “play” a small piano with solely three keys, producing sequences of three notes.
“There were two contexts: in one context, the rats only had to ever perform one specific sequence,” defined Ölveczky. “This is equivalent to you learning and overtraining on a single piano piece for weeks and months. You become really good, or ‘automatic,’ as we call it.”
Within the second experimental situation, rats had been nonetheless skilled on this sequence, however they realized to generate different three-element sequences that modified with each trial. These sequences relied on instructive cues offered to the rats, which they’d beforehand realized to interpret.
4 side-by-side trials of a rat taking part in the three-keyed “piano.” Credit score: Mizes et al.
“The analogy here is to a piano player who reads sheet music and produces action sequences based on cues (i.e., musical notes on a sheet) that they have learned to interpret,” mentioned Ölveczky.
“We then lesioned the motor cortex and found that animals that learned single overtrained sequences were unaffected, whereas the rats that had to interpret cues to get the sequence right were very much affected.”
These experiments yielded numerous fascinating insights. Firstly, the researchers discovered that the rats and not using a motor cortex may nonetheless play the sequence they had been overtrained on.
This confirmed the crew’s earlier findings, which prompt that the execution of motor sequences which have been practiced extensively, and thus turned automated, shouldn’t be supported by the motor cortex. In distinction, the flexibility to generate new sequences in response to particular cues, which requires larger flexibility, seemed to be supported by the motor cortex.
Apparently, the researchers discovered that the overtrained sequence, which was unbiased of the motor cortex when skilled in isolation, turned motor cortex dependent when skilled alongside extra versatile sequences.
“To keep with the pianist analogy, this is the case when, in the morning, you (over)train the one piece you will play for the concert, but in the evening you also play different tunes from sheet music,” mentioned Ölveczky. “This is interesting to us because it suggests that the same behavior can be implemented in different brain circuits depending on how it is learned.”
Primarily, the researchers discovered that if a sequence is realized alongside different ones and supported by the identical actions, it turns into reliant on the motor cortex. Nonetheless, if the specialised actions used to be taught a particular sequence will not be re-used in different contexts, the mind seems to consolidate this conduct in subcortical circuits.
“We believe this is possible because the progression of rote and highly stereotyped behaviors can be unambiguously defined in terms of past behavior,” mentioned Ölveczky.
“All the brain needs to do is connect past action to future action. But if the mapping between past action and future action is ambiguous and depends on environmental cues, then the cortex gets involved. This has implications for how we practice and learn our own skills.”
The current examine by Ölveczky and his colleagues presents priceless insights that would inform future studying strategies. Particularly, it means that overtraining on a single motor sequence may forestall learners from re-using the actions they realized in different contexts and to supply completely different behaviors.
“Avoiding this inflexibility might be why good piano teachers will never have you practice the same piece repeatedly, but instead interleave other exercises, like scales and etudes,” added Ölveczky. “In our next studies, we want to further explore the logic of how neural circuits generate learned skills under different conditions.”
Extra info:
Kevin G. C. Mizes et al, The function of motor cortex in motor sequence execution will depend on calls for for flexibility, Nature Neuroscience (2024). DOI: 10.1038/s41593-024-01792-3.
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