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How the brain accounts for uncertainties in motor planning

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In baseball, it can take only 400 milliseconds for the pitch to reach the plate. With a typical reaction time of 200 ms and a swing of about 150 ms, the batter must decide whether to swing and how to swing based only on the first 10 to 20 percent of the ball’s flight. .. At that point, there is still a lot of uncertainty about pitch speed and trajectory. Still, major league baseball batters have a 25% chance of hitting the ball. 40% if Ted Williams or Tony Gwynn is prime.

How batters and other athletes handle this uncertain information has long fascinated scientists.

“The fact that humans can do this is an incredible feat,” said Wraith Al Hussein, a graduate student at Harvard John A. Paulson’s School of Engineering and Applied Sciences (SEAS).

The underlying mechanism of these feats is at the heart of a new study by SEAS professors Gordon McKay of Al Hussein and Maurice Smith.The study was recently published in a journal eLife.

This study solves a long-standing question about how the brain chooses actions to take when there is uncertainty in the ultimate goal. motor Nervous system planning.

In ” Real WorldUnderstanding the mechanisms that reduce this uncertainty generally allows the brain to choose actions in real time, as we often interact with dynamic environments that can change rapidly in unpredictable ways. It is important to understand the mechanism used to plan. “Smith said.

Previous studies on exercise planning during uncertainty have shown that the brain prepares all potential goals in parallel, averages the exercise planning, and produces sophisticated intermediate exercise as additional information becomes available. Suggested to do. In that case, the batter’s brain averages everywhere the pitch can enter the strike zone, generates a swing based on this average, and adjusts slightly as the pitch approaches and the swing unfolds.

But is that what the brain is actually doing?

“Intermediate movements are widely observed, but given the remaining uncertainties, they may instead reflect neural decisions regarding the choice of a single best action at each point in time.” Al Hussein said. “Our study uses new experiments to systematically separate these possibilities, and when faced with uncertainty, humans do not average potential exercise plans, but rather tasks. We have found that it produces a single exercise plan that optimizes performance. ”

The researchers have designed several different experiments. One gave participants a target on the screen to aim with a kind of robot joystick. As the participants move towards the target, the joystick will try to push them out of the target and the participants will have to correct their forces. In another experiment, participants were given two targets. In about one-fifth of each move, one target disappears and participants need to capture the remaining targets. Participants did not know which target would disappear, so they had to aim in a way that was most likely to catch either target. In yet another experiment, participants needed to capture the target while avoiding intervening obstacles.

“In all cases, we find clear evidence when faced. UncertaintyHumans form a single exercise plan that optimizes task performance at all levels. This approach selects the first action to maximize for the ultimate success of the task. ”

Based on this performance optimization theory, the researchers also developed a computational model that accounts for 80-90 percent of the variance of individual differences among participants.

“This study overturns the decades-old theory of motor averaging and provides a mechanism framework for understanding the motor plan of the nervous system,” Smith said. “But the mechanism by which the brain calculates the single best behavioral choice has not yet been clarified.”


How the brain regulates motor function fluctuations


For more information:
Laith Alhussein et al, Motor Planning under Uncertainty, eLife (2021). DOI: 10.7554 / eLife.67019

Journal information:
eLife

Quote: How the brain explains the uncertainty of the exercise plan (September 14, 2021) can be found at https://medicalxpress.com/news/2021-09-brain-accounts-uncertainties-motor.html Obtained September 14, 2021

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