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Published on: August 1, 2018
Forward estimation of movement state in posterior parietal cortex
Grant H Mulliken1, Sam Musallam, Richard A Andersen
1Computation and Neural Systems and Division of Biology, California Institute of Technology, Mail Code 216-76, Pasadena, CA 91125, USA.
Summary
Primates use internal forward models in the posterior parietal cortex (PPC) to predict movement states, enabling rapid online control despite sensorimotor delays. This brain mechanism aids in accurate trajectory adjustments during goal-directed actions.
Area of Science:
- Neuroscience
- Motor Control
- Computational Neuroscience
Background:
- Goal-directed movements require rapid and accurate online trajectory control.
- Significant delays in the sensorimotor loop pose a challenge for real-time motor adjustments.
- Internal forward models are hypothesized to predict movement states for enhanced control.
Purpose of the Study:
- To investigate the role of the posterior parietal cortex (PPC) in online sensorimotor control.
- To examine neural encoding of movement dynamics in the PPC.
- To test the hypothesis that PPC acts as a forward model for motor control.
Main Methods:
- Single-neuron recordings were conducted in monkeys performing a joystick task.
- Neural activity was analyzed in relation to static target direction and dynamic cursor movement angle.
- Space-time tuning functions of neurons were examined for separability.
Main Results:
- Neurons in the PPC encoded both static target direction and dynamic movement angle.
- Many neurons exhibited dynamic encoding properties consistent with a forward estimate of cursor state.
- These estimates were not directly available from sensory feedback or motor commands.
- Neuron tuning functions were largely separable in the angle-time plane, suggesting encoding of straight trajectories.
Conclusions:
- The PPC appears to function as a forward model for online sensorimotor control.
- This forward modeling capability helps primates overcome sensorimotor delays during goal-directed movements.
- The PPC's encoding of movement trajectories supports rapid and accurate motor control.
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