Shaping the optimal repetition interval for cathodal transcranial direct current stimulation (tDCS)

Area of Science:

• Neuroscience
• Neurophysiology
• Noninvasive Brain Stimulation

Background:

• Transcranial direct current stimulation (tDCS) is a promising noninvasive brain stimulation technique for neurological and psychiatric disorders.
• Current tDCS protocols have limited aftereffect durations, necessitating strategies for prolonged therapeutic benefits.
• Optimal protocols for repetitive tDCS to extend aftereffects remain largely unknown.

Purpose of the Study:

• To investigate the impact of varying inter-stimulation intervals on cathodal tDCS-induced cortical excitability.
• To determine how different break durations influence the aftereffects of repetitive tDCS.
• To identify optimal stimulation timing for prolonging tDCS aftereffects.

Main Methods:

• 12 healthy subjects received two identical 9-minute, 1 mA cathodal tDCS sessions.
• Inter-stimulation intervals tested were 0 minutes (no break), 3 minutes, 20 minutes, 3 hours, and 24 hours.
• Cortical excitability alterations were assessed following the stimulation protocols.

Main Results:

• Doubling stimulation duration without a break extended aftereffects from 60 to 90 minutes.
• Performing the second stimulation during the aftereffects of the first prolonged and enhanced effects up to 120 minutes.
• Intervals of 3 or 24 hours initially attenuated or abolished aftereffects, but they re-established within 120 minutes in the 24-hour condition.

Conclusions:

• The duration of aftereffects following cathodal tDCS is significantly influenced by the interval between stimulation sessions.
• Strategic timing of repetitive tDCS may be crucial for achieving prolonged therapeutic effects.
• Further research is needed to optimize stimulation intervals for clinical applications of tDCS.