Somatotopically arranged inputs from putamen and subthalamic nucleus to primary motor cortex

Area of Science:

• Neuroscience
• Motor Control
• Basal Ganglia Function

Background:

• The basal ganglia play a crucial role in motor control.
• Understanding the specific circuits within the basal ganglia that project to the primary motor cortex (MI) is essential for elucidating motor function.

Purpose of the Study:

• To investigate the organization of basal ganglia inputs to different representations within the macaque primary motor cortex (MI).
• To delineate the somatotopic organization of these inputs within the striatum and subthalamic nucleus (STN).

Main Methods:

• Utilized retrograde transsynaptic transport of rabies virus.
• Injected rabies virus into hindlimb, forelimb, and orofacial regions of the macaque MI.
• Analyzed neuronal labeling in the striatum and STN four days post-injection.

Main Results:

• Observed distinct labeling patterns in the dorsal striatum (putamen) and ventral striatum (nucleus accumbens).
• Dorsal striatal labeling was somatotopically arranged, mirroring corticostriatal input patterns for hindlimb, orofacial, and forelimb areas.
• Subthalamic nucleus (STN) also showed somatotopic organization aligned with corticosubthalamic inputs.
• Ventral striatal labeling was consistent across all MI injection sites.

Conclusions:

• The cortico-basal ganglia motor circuits involving the dorsal putamen and STN may form separate, somatotopically organized closed loops.
• The ventral striatum appears to provide common multisynaptic projections to all body-part representations in the MI.
• These findings offer insights into the parallel processing within basal ganglia motor circuits.