Current challenges: the ups and downs of tACS

Area of Science:

• Neuroscience
• Biophysics
• Neuromodulation

Background:

• Transcranial electrical stimulation, including tACS, is a popular neuromodulation tool due to its adaptability and tolerability.
• tACS aims to entrain neural oscillations for causal insights into brain-behavior, but weak intracranial field strengths pose a challenge.
• The current review examines challenges in tACS application, including weak field intensities and potential transcutaneous effects.

Purpose of the Study:

• To review the challenges and recent advancements in transcranial alternating current stimulation (tACS).
• To discuss the biophysics of electrical brain stimulation and factors limiting intracranial field strength.
• To explore methods for managing tACS artifacts and improving current distribution for enhanced neuromodulation.

Main Methods:

• Review of existing literature on tACS biophysics, applications, and challenges.
• Analysis of factors contributing to weak intracranial field strengths.
• Examination of techniques for artifact management and novel current distribution methods.

Main Results:

• Conventional tACS intensities result in weak intracranial fields (< 1 V/m), questioning the plausibility of transcranial effects.
• Scalp nerve stimulation (transcutaneous effects) is a significant factor influencing tACS outcomes.
• Recent advancements include high-frequency protocols for artifact management and innovative methods for dynamic or focal current distribution.

Conclusions:

• Despite challenges, tACS remains a valuable tool for neuromodulation.
• Managing artifacts and optimizing current delivery are crucial for maximizing tACS efficacy.
• Future research should focus on advanced techniques to overcome current limitations and enhance transcranial effects.