Cerebellar output shapes cortical preparatory activity during motor adaptation

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• The cerebellum is vital for motor adaptation, recalibrating movements based on errors.
• Cortical motor adaptation signals in primates emerge early in motor planning.
• The origin of these early signals (cerebellar vs. intracortical) remains debated.

Purpose of the Study:

• To investigate the role of cerebellar outflow in motor adaptation and cortical preparatory activity.
• To determine if cerebellar signals are necessary for encoding task structure in motor cortex.
• To elucidate the interplay between cerebellar feedback and intracortical mechanisms during adaptation.

Main Methods:

• Trained macaque monkeys to reach in a viscous force field (FF) while selectively blocking cerebellar outflow.
• Recorded motor cortical neural activity during reaching tasks under FF and null-field conditions.
• Utilized a computational model to simulate neural activity and test hypotheses about feedback dimensionality.

Main Results:

• Cerebellar outflow blockade significantly impaired force field adaptation.
• Blocking cerebellar signals induced compensatory shifts in motor cortical preparatory activity.
• Neural preparatory activity showed increased dimensionality and reduced generalization in the absence of cerebellar signals.
• A computational model confirmed that low-dimensional cerebellar-like feedback could explain the observed neural changes.

Conclusions:

• Cerebellar signals convey crucial task structure information that shapes the preparatory motor cortical activity.
• Cerebellar feedback constrains the dimensionality of the cortical preparatory manifold, facilitating movement generalization.
• In the absence of cerebellar signals, cortical mechanisms partially compensate to restore motor adaptation, albeit with altered neural dynamics.