Augmenting Plasticity Induction in Human Motor Cortex by Disinhibition Stimulation.

Area of Science:

• Neuroscience
• Neurophysiology
• Brain Stimulation

Background:

• Cellular studies indicate that disinhibition can enhance long-term plasticity (LTP) induction.
• Transcranial magnetic stimulation (TMS) has been shown to evoke late cortical disinhibition (LCD) in the human primary motor cortex (M1).

Purpose of the Study:

• To investigate whether LCD can augment LTP-like plasticity in the human motor cortex.
• To introduce and validate a novel protocol, disinhibition stimulation (DIS), for enhancing cortical plasticity.

Main Methods:

• Patterned repetitive TMS was applied to the left M1 using specific interdoublet intervals (IDIs) timed to the individual peak LCD.
• Motor-evoked potential (MEP) amplitude was measured to assess changes in corticospinal excitability.
• Control experiments used varied IDIs, and topographic specificity and plasticity duration were examined.

Main Results:

• The DIS protocol significantly increased MEP amplitude by 147% ± 4%, indicating LTP-like plasticity.
• Control experiments demonstrated that plasticity was dependent on the precise timing of the IDI relative to LCD.
• The observed LTP-like plasticity was specific to the stimulated M1 hand region and lasted for 60 minutes.

Conclusions:

• GABA(B)-ergic LCD provides a potent mechanism for augmenting LTP-like plasticity induction in the human cortex.
• The disinhibition stimulation (DIS) protocol is an effective method for enhancing neuroplasticity.
• This research opens new avenues for non-invasive brain stimulation techniques aimed at modulating cortical plasticity.