Non-invasive Brain Stimulation: A Paradigm Shift in Understanding Brain Oscillations

Area of Science:

• Cognitive Neuroscience
• Neuroscience
• Brain Stimulation

Background:

• Cognitive neuroscience traditionally relies on correlational data to link brain activity with cognitive processes.
• Non-invasive brain stimulation (NIBS) techniques, particularly transcranial alternating current stimulation (tACS), now enable direct manipulation of brain function.
• tACS offers a powerful tool to move beyond correlational evidence and establish causal relationships in cognitive neuroscience.

Purpose of the Study:

• To review the application and impact of transcranial alternating current stimulation (tACS) in understanding cognitive functions.
• To explore how tACS can directly interfere with and modulate ongoing brain oscillations.
• To examine mechanistic theories linking cognitive functions to specific brain oscillation parameters (amplitude, frequency, phase, coherence) using tACS.

Main Methods:

• Review of studies employing tACS in healthy volunteers, patients with intracranial recordings, and animal models.
• Analysis of tACS effects on neural entrainment and plasticity.
• Examination of tACS protocols testing the functional relevance of oscillation parameters and recent advancements like non-sinusoidal waveforms and closed-loop systems.

Main Results:

• tACS effectively modulates human brain oscillations across different observational levels, with findings translating between human and animal studies.
• Neural entrainment and plasticity are identified as key mediators of tACS-induced behavioral effects.
• tACS is actively used to test mechanistic theories about the role of specific oscillation parameters in cognitive functions.

Conclusions:

• tACS is a crucial NIBS technique for establishing causal links between brain oscillations and cognitive processes.
• The review highlights the potential of tACS in advancing our understanding of the neural underpinnings of cognition.
• Future directions include advanced tACS waveforms and closed-loop applications for more precise neural modulation.