Grid-based transcutaneous spinal cord stimulation: probing neuromodulatory effect in spinal flexion reflex circuits

Area of Science:

• Neuroscience
• Spinal Cord Research
• Neuromodulation

Background:

• Non-invasive spinal stimulation offers a promising avenue for modulating spinal excitability.
• Understanding the precise effects of transcutaneous spinal cord stimulation (tSCS) on spinal circuits is crucial for therapeutic applications.

Purpose of the Study:

• To investigate the neuromodulatory capacity of sub-motor grid-based tSCS on lumbar spinal cord excitability.
• To examine the impact of tSCS on polysynaptic reflex pathways involving motoneurons and interneurons activated by cutaneous afferents.

Main Methods:

• Two grid electrode montages (transverse and diagonal) were used for tSCS applied to the T10-T11 spinous process.
• Flexion reflex excitability in the tibialis anterior muscle and H-reflex in the soleus muscle were assessed post-stimulation.
• Participants were seated during the 20-minute stimulation period.

Main Results:

• Grid-based tSCS induced significant neuromodulatory effects, resulting in a net inhibitory influence on the flexion reflex.
• The diagonal montage uniquely shortened the duration of the flexion reflex.
• No significant effects were observed on the H-reflex, suggesting targeted modulation of polysynaptic pathways.

Conclusions:

• Grid-based tSCS can specifically modulate spinal activities within polysynaptic flexion reflex pathways.
• The findings suggest potential for grid-specific targeted neuromodulation of spinal circuits.
• tSCS demonstrates potential as a non-invasive tool for altering spinal reflex activity.