Striatal Pathways for Action Counting and Steering.

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• The basal ganglia (BG) are essential for motor control, but their specific functions in coordinating voluntary movements are debated.
• Understanding the neural circuits underlying movement initiation, execution, and goal-directed behavior is crucial.

Purpose of the Study:

• To investigate the role of direct pathway (dSPN) and indirect pathway (iSPN) striatal projection neurons in motor control and action sequencing.
• To elucidate how the basal ganglia integrate kinematic and sequential information to guide behavior towards goals.

Main Methods:

• Developed a novel operant counting task in mice to quantify continuous kinematics, discrete actions, and action sequences.
• Utilized optogenetic manipulations to selectively activate or inhibit dSPNs and iSPNs.
• Employed in vivo calcium imaging to record neural activity in striatal projection neurons during task performance.

Main Results:

• Optogenetic activation of dSPNs extended action sequences, mimicking accumulator reset, while iSPN activation terminated them, mimicking count completion.
• Distinct, intermixed populations of dSPNs and iSPNs showed ramping activity related to lever approach and count progression.
• Neural activity differences between dSPN and iSPN populations scaled with proximity to spatial and count-based goals.

Conclusions:

• The basal ganglia employ a push-pull model involving dSPNs and iSPNs to integrate kinematic and sequential representations for goal-directed motor control.
• These findings highlight the BG's role in monitoring and steering progress toward behavioral objectives by unifying discrete and continuous movement control.