Increasing human brain excitability by transcranial high-frequency random noise stimulation

Area of Science:

• Neuroscience
• Neurophysiology
• Brain Stimulation

Background:

• Noninvasive transcranial stimulation techniques, including repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), have been utilized for over two decades.
• These methods aim to induce neuroplastic-like effects in the human cortex, modifying synaptic transmission based on activity.
• Existing techniques have limitations, such as the current flow direction sensitivity of tDCS.

Purpose of the Study:

• To introduce and evaluate a novel noninvasive brain stimulation method: transcranial random noise stimulation (tRNS).
• To investigate the effects of tRNS on cortical excitability and its duration.
• To compare the therapeutic potential and characteristics of tRNS with established methods like rTMS and tDCS.

Main Methods:

• Application of a random electrical oscillation spectrum over the motor cortex using tRNS.
• Assessment of cortical excitability changes through physiological measures and behavioral tasks.
• Involvement of 80 human subjects in the study.

Main Results:

• tRNS consistently increased cortical excitability for up to 60 minutes post-stimulation.
• The observed effects were validated through both physiological and behavioral assessments in 80 subjects.
• Higher frequencies (100-640 Hz) were identified as key to generating the excitability increase, potentially via repeated Na(+) channel opening.

Conclusions:

• tRNS is a novel and effective method for noninvasively modulating cortical excitability.
• The technique demonstrates comparable therapeutic potential to rTMS and tDCS for conditions like depression.
• tRNS overcomes the directionality constraint associated with tDCS, offering a potentially more versatile application.