Boosting brain excitability by transcranial high frequency stimulation in the ripple range

Area of Science:

• Neuroscience
• Neuromodulation
• Cortical Excitability

Background:

• Neurological diseases pose challenges in symptom management.
• Increasing cortical excitability via transcranial stimulation is a key therapeutic goal.
• Targeting high-frequency oscillations is a potential strategy.

Purpose of the Study:

• To investigate the effects of high-frequency transcranial alternating current stimulation (tACS) on human motor cortex excitability.
• To determine the optimal frequency for tACS-induced cortical excitability enhancement.
• To assess the duration and characteristics of after-effects.

Main Methods:

• Twenty-one subjects received tACS at 80 Hz, 140 Hz, 250 Hz, and sham stimulation over the motor cortex (M1).
• Motor cortex excitability was measured using motor evoked potentials (MEPs) via transcranial magnetic stimulation.
• Specific intracortical inhibition and facilitation measures were assessed.

Main Results:

• 140 Hz tACS significantly increased M1 excitability during and up to 1 hour post-stimulation.
• Sham and 80 Hz stimulation had no effect; 250 Hz showed delayed and shorter effects.
• 140 Hz tACS reduced short-interval intracortical inhibition but did not affect other intracortical measures or motor learning.

Conclusions:

• High-frequency tACS, particularly at 140 Hz, is a promising non-invasive protocol to increase human cortical excitability.
• This method offers potential for therapeutic interventions in neurological conditions.
• Further research into ripple-range stimulation for cortical excitability is warranted.