Changes in Activity of Spinal Postural Networks at Different Time Points After Spinalization

Area of Science:

• Neuroscience
• Spinal Cord Injury Research
• Motor Control

Background:

• Postural limb reflexes (PLRs) are crucial for maintaining balance and correcting posture.
• Spinalization, a model of spinal cord injury, causes loss of PLRs and leads to abnormal motor responses.
• Plastic changes in spinal networks are suspected to underlie these altered responses.

Purpose of the Study:

• To investigate the time course of plastic changes in spinal postural networks after spinalization.
• To characterize the recovery of spinal interneuron activity and sensory signal processing.
• To correlate these changes with the reappearance and quality of motor responses.

Main Methods:

• Decerebrated rabbits were studied at 3, 7, and 30 days post-T12 spinalization.
• Responses of L5 spinal interneurons and hindlimb muscle EMG were recorded.
• Stimulation mimicked sensory inputs that elicit PLRs in intact animals.

Main Results:

• Neurons responding to postural stimuli were found, but their proportion remained low post-spinalization.
• Interneuron activity recovered to control levels within 3 days, but sensory signal processing remained distorted.
• Motor responses reappeared by 3 days but were weak, irregular, and often incorrectly phased, with gradual amplitude increase.

Conclusions:

• Spinalization induces distinct plastic changes: rapid interneuron activity recovery and slow motoneuronal excitability recovery.
• Recovered interneuron activity likely enables motor response reappearance.
• Impaired sensory signal processing and enhanced neuronal oscillations contribute to abnormal PLRs and lost postural function.