Rhesus macaque versus rat divergence in the corticospinal projectome

Area of Science:

• Neuroscience
• Comparative neuroanatomy

Background:

• Corticospinal neurons are crucial for fine motor control.
• Understanding their full projection targets (projectome) is key to deciphering motor control mechanisms.

Purpose of the Study:

• To map and compare the entire projectome of corticospinal neurons involved in fine distal forelimb control in rats and rhesus macaques.
• To investigate the structural-functional correlations of corticospinal system outputs.

Main Methods:

• Utilized viral intersectional tools for precise neuronal tracing.
• Employed optogenetics and transsynaptic viral tracing for functional validation.

Main Results:

• Rat corticospinal neurons project extensively to 23 brain and spinal regions, with a significant weighting towards sensory systems.
• Rhesus macaques show a narrower, heavier projection bias towards spinal and brainstem motor systems.
• Demonstrated a multi-modal integrative role for rat corticospinal projections versus a primary motor output role in macaques.

Conclusions:

• Corticospinal systems exhibit distinct organizational principles and functional roles across species.
• Rat corticospinal projections integrate motor commands with sensory information, while macaque projections primarily serve as a final motor output pathway.
• Mapping total axonal output and target weighting reveals unique structural-functional correlations within neuronal systems.