Uncertainty Shapes Neural Dynamics in Motor Cortex During Reaching

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• Voluntary movements often occur with incomplete information about the goal.
• The brain must flexibly adjust motor plans and ongoing movements based on changing conditions.

Purpose of the Study:

• To investigate how uncertainty about a reach target influences neural preparation and execution.
• To examine neural activity in dorsal premotor (PMd) and primary motor (M1) cortices during a reaching task with varying target uncertainty.

Main Methods:

• Recorded neural activity from PMd and M1 in a rhesus macaque performing a reaching task.
• Manipulated target uncertainty using probabilistic cues and delayed target presentation.
• Analyzed population neural trajectories in relation to uncertainty levels.

Main Results:

• Neural trajectories in PMd, but not M1, showed progressively less expansive preparatory states with higher uncertainty.
• Despite altered preparatory states, the executed movements remained consistent across uncertainty levels.
• A specific dimension in neural state-space was identified that represents the level of uncertainty during preparation and execution.

Conclusions:

• Neural preparation in PMd adapts to target uncertainty, with narrower trajectories potentially facilitating faster re-planning.
• The findings suggest a neural mechanism for adapting goal-directed movements under conditions of incomplete information.
• Motor planning and execution can be flexibly adjusted by the brain in response to varying levels of environmental uncertainty.