Two input systems for body representations in the primate striatal matrix: experimental evidence in the squirrel...

Area of Science:

• Neuroscience
• Motor Control
• Basal Ganglia Function

Background:

• The striatum, a key component of the basal ganglia, plays a critical role in motor control.
• Understanding the organization of sensorimotor cortical inputs to the striatum is crucial for deciphering motor functions and movement disorders.

Purpose of the Study:

• To investigate the distinct sensorimotor cortical input systems to the striatum in squirrel monkeys.
• To map the somatotopic organization of projections from the primary motor cortex (MI) and primary somatosensory cortex (SI) to the striatal matrix.

Main Methods:

• Utilized intracortical microstimulation and multiunit recording to guide tracer injections in MI and SI.
• Employed anterograde tracers to visualize projection pathways.
• Used enkephalin immunohistochemistry to delineate striosome/matrix architecture.

Main Results:

• Identified two distinct sensorimotor input systems to the striatal "matrisomes" (matrix zones).
• Demonstrated somatotopic projections from ipsilateral MI and SI to specific matrisomes.
• Revealed somatotopic projections from contralateral MI to different matrisomes, with alternating patterns except for the face representation.
• Observed stronger contralateral MI projections for axial body parts compared to distal parts.

Conclusions:

• The primate striatal matrix exhibits a unique, patchy organization of sensorimotor cortical inputs.
• Contralateral and ipsilateral body representations generally alternate within the striatal matrix, similar to ocular dominance columns.
• This organization provides insights into basal ganglia motor control and potential mechanisms underlying movement disorders.