Abstract
When confronting an abrupt external perturbation force during movement, subjects continuously adjust their behaviors to adapt to changes. Such adaptation is of great importance for realizing flexible motor control in varied environments, but the potential cortical neuronal mechanisms behind it have not yet been elucidated. Aiming to reveal potential neural control system compensation for external disturbances, we applied an external orientation perturbation while monkeys performed an orientation reaching task and simultaneously recorded the neural activity in the primary motor cortex (M1). We found that a subpopulation of neurons in the primary motor cortex specially created a time-locked activity in response to a “go” signal in the adaptation phase of the impending orientation perturbation and did not react to a “go” signal under the normal task condition without perturbation. Such neuronal activity was amplified as the alteration was processed and retained in the extinction phase; then, the activity gradually faded out. The increases in activity during the adaptation to the orientation perturbation may prepare the system for the impending response. Our work provides important evidence for understanding how the motor cortex responds to external perturbations and should advance research about the neurophysiological mechanisms underlying motor learning and adaptation.
Highlights
When confronting an abrupt external perturbing force during movement, subjects constantly adjust their behavior to correspond to instant changes
An RTp less than the 95% CI lower bound is an indication of the animal predicting the perturbation. As shown in this figure, for all of the four repeat perturbation conditions, both monkeys were able to predict the perturbation after a few trials, it took them a few more trials on the first perturbation day before starting to predict
On the last perturbation day, the monkey had predicted in only one trial for some repeat perturbation conditions
Summary
When confronting an abrupt external perturbing force during movement, subjects constantly adjust their behavior to correspond to instant changes Such alteration is essential for flexible motor control in varied environments [1], but it is still not clear what strategies the brain utilizes to solve such learning and adaptation issues. Feedback control aiming to eliminate the inconsistency between expected movement and output is often considered to be time consuming and inefficient because the abruptness of such perturbation means that it occurs within a very limited time. In such conditions, a feedforward control mechanism would play an important role in improving the ability of the subjects to adapt. To elucidate the basis of adaptation in initialization, development, and extinction on a neurophysiological level, an exploration of associated neuron ensembles in various cortical regions is significant
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