Immediate Effects of Preconditioning Intermittent Theta Burst Stimulation on Lower Extremity Motor Cortex...

Area of Science:

• Neuroscience
• Motor Control
• Neuromodulation

Background:

• Previous research demonstrated inhibitory priming with continuous theta burst stimulation (cTBS) enhances excitatory conditioning stimuli with intermittent theta burst stimulation (iTBS) in upper limbs.
• The efficacy of this combined stimulation in lower extremities remained uninvestigated.
• This study explored cTBS preconditioning's effect on iTBS-induced motor cortex excitability in the lower limb.

Purpose of the Study:

• To investigate the modulatory effect of cTBS preconditioning on iTBS-induced motor cortex excitability in the lower limb.
• To determine if combined cTBS and iTBS protocols enhance lower extremity motor cortex excitability in healthy individuals.

Main Methods:

• A randomized crossover design involving 25 healthy participants.
• Three protocols were administered: cTBS + iTBS, sham cTBS + iTBS, and sham cTBS + sham iTBS, with one-week intervals.
• Motor-evoked potentials (MEPs) of the tibialis anterior muscle were measured before, immediately after, and 20 minutes after interventions.

Main Results:

• The cTBS + iTBS protocol significantly increased MEP amplitude at both immediate post-intervention and 20-minute follow-up (p < 0.01).
• No significant changes in MEP amplitude were observed with sham protocols.
• No significant differences were found between the three protocols at any time point.

Conclusions:

• Preconditioning the lower extremity motor cortex with cTBS before iTBS promptly enhances its excitability.
• This facilitatory effect on lower limb motor cortex excitability persists for at least 20 minutes.