Modulating motor cortex plasticity via cortical and peripheral somatosensory stimulation.

Area of Science:

• Neuroscience
• Motor Control
• Somatosensory System

Background:

• The motor and somatosensory systems interact for effective motor control.
• Somatosensory stimulation influences primary motor cortex (M1) excitability.
• Mechanisms of somatosensory stimulation effects on M1 plasticity are unclear.

Purpose of the Study:

• Investigate effects of cortical and peripheral somatosensory stimulation on M1 plasticity.
• Examine modulation of corticospinal excitability and M1 intracortical circuits.
• Differentiate mechanisms of cortical vs. peripheral somatosensory input.

Main Methods:

• Applied continuous theta-burst stimulation (cTBS) to primary somatosensory cortex (S1).
• Administered transcutaneous electrical nerve stimulation (TENS) to the median nerve.
• Measured motor-evoked potentials (MEPs), short-latency intracortical inhibition (SICI), intracortical facilitation (ICF), and short-latency afferent inhibition (SAI).

Main Results:

• cTBS increased MEPs for >50 min; TENS increased MEPs for 10 min.
• Neither cTBS nor TENS affected SICI or ICF.
• cTBS decreased SAI, while TENS did not; sham procedures had no effect.

Conclusions:

• Both cortical and peripheral somatosensory stimulation modulate corticospinal excitability.
• Cortical stimulation effects are more prolonged and modulate M1-S1 interaction.
• Neither stimulation type affects M1's intracortical inhibitory/excitatory circuits.