Transcranial alternating current stimulation in the low kHz range increases motor cortex excitability

Area of Science:

• Neuroscience
• Neuron stimulation techniques

Background:

• Transcranial electrical and magnetic stimulation can alter cortical excitability.
• Developing novel stimulation paradigms is crucial for advancing neuromodulation.

Purpose of the Study:

• To investigate high-frequency transcranial alternating current stimulation (tACS) (>1 kHz) for modulating neuroplasticity.
• To explore tACS's potential to directly influence neuronal membrane excitability in the primary motor cortex (M1).

Main Methods:

• tACS was applied at 1, 2, and 5 kHz to the left primary motor cortex in 11 healthy volunteers.
• Corticospinal excitability was measured using motor-evoked potentials (MEPs) via transcranial magnetic stimulation (TMS).
• Sham stimulation served as a control condition.

Main Results:

• All tested tACS frequencies increased MEP amplitudes post-stimulation.
• 2 and 5 kHz tACS demonstrated greater sustained effects on cortical excitability compared to 1 kHz.
• Stimulation effects persisted for up to 30-60 minutes.

Conclusions:

• Low kHz range tACS may directly activate neuronal membranes rather than interfering with network oscillations.
• This high-frequency tACS approach presents a novel method for directly modulating cortical excitability.
• This technique could potentially offer an alternative to repetitive transcranial magnetic stimulation (rTMS) in clinical applications.