Forelimb movements in the cat; kinetic features and neuronal control

Area of Science:

• Neuroscience
• Motor Control
• Animal Behavior

Background:

• Descending motor pathways, including corticospinal (CST) and rubrospinal (RST) tracts, are critical for forelimb movements.
• Propriospinal neurons (PNs) in the C3-C4 segments and forelimb interneurons (C6-Th1) are known to mediate specific motor commands.

Purpose of the Study:

• To investigate the role of defined descending pathways in controlling target-reaching and food-taking movements in cats.
• To explore the functional contribution of propriospinal neurons (PNs) and subcortical systems in motor command execution and adjustment.

Main Methods:

• Behavioral experiments involving cats performing target-reaching and food-taking tasks.
• Serial lesioning techniques targeting specific descending tracts (CST, RST) and spinal cord segments (C2, C5/6).
• Kinematic analysis of forelimb movements using motion tracking (SELSPOT system).

Main Results:

• Food-taking, normally abolished by dorsal lateral funiculus lesions, could still be performed after CST transection followed by RST lesion, suggesting a compensatory role for ventral reticulospinal fibers.
• Target-reaching corrections, initiated when target positions shifted, were not significantly affected by CST/RST input transection to forelimb interneurons but were impaired by ventral C2 lesions.
• Lesions of C3-C4 PNs disrupted target-reaching correction kinematics, causing initial ataxia and altered braking, indicating their importance in movement adjustments.

Conclusions:

• Ventral reticulospinal pathways can compensate for rubrospinal tract damage in mediating food-taking.
• Propriospinal neurons (PNs) in C3-C4 are essential for target-reaching switching and kinematic adjustments.
• Subcortical pathways, potentially ventral tecto- and tecto-reticulospinal tracts, may facilitate rapid target-reaching adjustments.