Transcranial direct current stimulation treatment protocols: should stimulus intensity be constant or incremental...

Area of Science:

• Neuroscience
• Neuromodulation
• Motor Cortex Research

Background:

• Transcranial direct current stimulation (tDCS) is emerging as a potential therapeutic tool in neuropsychiatry.
• Establishing optimal tDCS treatment protocols is crucial for its clinical application.
• Understanding the effects of different stimulation intensities on cortical excitability is key.

Purpose of the Study:

• To compare the efficacy of constant versus gradually increasing current intensity in tDCS protocols.
• To investigate the cumulative effects of daily tDCS sessions on cortical excitability.
• To determine the optimal tDCS protocol for enhancing motor cortex excitability.

Main Methods:

• An intra-individual randomized cross-over design was employed with 11 healthy volunteers.
• Participants received five tDCS sessions to the left primary motor cortex over consecutive weekdays.
• Cortical excitability was measured using motor-evoked potentials (MEPs) via electromyography before and after each session.

Main Results:

• Both constant and gradually increasing tDCS intensities led to significant cumulative increases in cortical excitability.
• No significant differences in efficacy were observed between the two tDCS intensity protocols.
• Motor thresholds showed significant decreases from Monday to Friday in both conditions, indicating enhanced excitability.

Conclusions:

• Daily tDCS application over a week, whether at constant or gradually increasing intensity, is equally effective for increasing motor cortex excitability.
• These findings support the use of both protocols in therapeutic settings targeting the motor cortex.
• Further research may explore long-term effects and applications in clinical populations.