Striatal ensembles specify and control granular forelimb actions.

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• The striatum is vital for movement control and learning, with its dysfunction linked to movement disorders.
• Traditionally, striatal activity was thought to broadly invigorate movement, but recent evidence suggests it encodes specific actions.
• The granularity and causal role of striatal activity in controlling specific ongoing movements remain unclear.

Purpose of the Study:

• To investigate the specificity and causal role of striatal medium spiny neuron (MSN) activity in controlling fine motor actions.
• To determine if striatal activity encodes distinct movements at a granular level.
• To explore the function of both D1-MSNs and D2-MSNs in action control.

Main Methods:

• Mice performed a task involving two distinct forelimb actions (push/pull) on a joystick.
• Two-photon microscopy was used to image dorsolateral striatum MSN activity during action preparation and execution.
• A closed-loop holographic optogenetics system was developed to stimulate action-specific neural ensembles.

Main Results:

• Striatal activity encoded the preparation and execution of specific actions, irrespective of reinforcement.
• Both D1-MSNs and D2-MSNs populations equally encoded action identity.
• Stimulation of action-specific MSN ensembles causally enhanced ongoing actions congruent with the stimulated ensemble.

Conclusions:

• Specific ensembles of D1- and D2-MSNs causally control specific ongoing actions with high granularity.
• This finding provides a mechanistic framework for understanding movement impairments in striatal dysfunction.
• The results highlight the precise role of the striatum in fine motor control and action selection.