Spinal cord associative plasticity improves forelimb sensorimotor function after cervical injury.

Area of Science:

• Neuroscience
• Spinal Cord Injury Research
• Rehabilitation Science

Background:

• Previous attempts to induce associative plasticity primarily targeted the cortex, yielding inconsistent results.
• Targeted circuits in prior studies were often inferred rather than directly investigated.
• A significant gap exists in directly targeting sensorimotor integration within the spinal cord for plasticity induction.

Purpose of the Study:

• To develop and test a novel method, spinal cord associative plasticity (SCAP), for strengthening sensorimotor connections in the spinal cord.
• To investigate the physiological effects, mediating pathways, and functional recovery potential of SCAP after spinal cord injury.
• To determine if SCAP can improve forelimb function and sensorimotor integration in a preclinical model of spinal cord injury.

Main Methods:

• Developed SCAP by precisely timing motor cortex and dorsal spinal cord stimulations to leverage natural sensorimotor convergence.
• Investigated the necessity of cortical descending motor and spinal proprioceptive afferents for the SCAP effect.
• Administered daily SCAP sessions to rats with moderate cervical spinal cord injury and assessed functional recovery, sensorimotor responses, and reflex modulation.

Main Results:

• Synchronous pairing of motor cortex and spinal cord stimulation significantly augmented muscle potentials, demonstrating SCAP's efficacy.
• The SCAP effect was dependent on both descending motor and ascending proprioceptive pathways, confirming targeted sensorimotor interaction.
• SCAP treatment in injured rats led to significant improvements in forelimb dexterity and normalized H-reflex modulation compared to sham controls.

Conclusions:

• Spinal cord associative plasticity effectively strengthens sensorimotor connections within the spinal cord.
• SCAP promotes partial recovery of reflex modulation and forelimb function following moderate spinal cord injury.
• The feasibility of translating SCAP to human clinical trials for spinal cord injury and other sensorimotor disorders is supported by the findings.