Altered obstacle negotiation after low thoracic hemisection in the cat

Area of Science:

• Neuroscience
• Locomotion research
• Spinal cord injury research

Background:

• Lateralized spinal cord injury (SCI) in humans leads to significant walking recovery but deficits in adaptive locomotion, like obstacle negotiation.
• Normal obstacle negotiation involves increased limb flexion, with potential involvement of the spinally organized stumbling corrective response for unanticipated obstacles.

Purpose of the Study:

• This study investigates the recovery of obstacle negotiation following a low-thoracic spinal hemisection in cats.
• The research aims to characterize how voluntary and reflex components of locomotion are affected post-partial SCI, specifically focusing on the ipsilateral hindlimb.

Main Methods:

• Cats were trained to cross an obstacle runway before and after a spinal hemisection.
• Locomotor behavior, particularly hindlimb trajectory and obstacle clearance, was assessed at various time points post-injury (2, 4, 8, and 16 weeks).

Main Results:

• Post-injury, cats frequently dragged their hindlimb over obstacles (~90% at 2 weeks).
• The stumbling corrective response was delayed, appearing after 2 weeks.
• While obstacle negotiation improved between 4-8 weeks, insufficient limb lift persisted, eliciting the stumbling response even at 16 weeks in ~50% of encounters.

Conclusions:

• Following spinal hemisection, recovery of ipsilateral hindlimb trajectory modification allows ~50% successful obstacle clearance by 16 weeks.
• Despite observed plasticity, consistent obstacle clearance remains impaired, likely contributing to falls in individuals with SCI.
• A post-injury lead limb bias suggests potential training strategies to enhance successful clearances.