Maintenance of specificity by sprouting and regenerating peripheral nerves. I. Normal variability

Area of Science:

• Neuroscience
• Motor control
• Comparative anatomy

Background:

• The spinal cord's representation of hindlimb muscles exhibits variability.
• Understanding this variability is crucial for motor control research.

Purpose of the Study:

• To investigate inter-animal variability in the spinal cord's representation of the tibialis anterior (TA) muscle in cats.
• To correlate this variability with the lumbosacral plexus arrangement and its effect on the TA tendon reflex.

Main Methods:

• Retrograde transport of HRP to label motor neurons.
• Dissection of the lumbosacral plexus.
• Acute section of spinal nerves (L5-S2) and reflex testing.

Main Results:

• Significant inter-animal variability in the number and rostrocaudal extent of TA motor neurons.
• Three classes of lumbosacral plexus representation identified: prefixed, postfixed, and intermediate.
• TA tendon reflex was weakened or abolished in prefixed/postfixed animals after nerve section, despite spared L7 nerve.

Conclusions:

• The spinal representation of the tibialis anterior muscle is highly variable between individual cats.
• Lumbosacral plexus arrangement influences the spinal nerve root distribution to the TA muscle.
• Variability in spinal nerve root contribution and motor axon distribution may affect reflex maintenance.