θ-γ Cross-Frequency Transcranial Alternating Current Stimulation over the Trough Impairs Cognitive Control

Area of Science:

• Neuroscience
• Cognitive Science

Background:

• Cognitive control enables goal-directed decisions, linked to theta band oscillations and theta-gamma cross-frequency coupling (CFC) in frontal and cingulate cortices.
• The specific behavioral impact of different theta-gamma CFC patterns remains unclear.

Purpose of the Study:

• To investigate the behavioral consequences of phase-specific theta-gamma CFC using transcranial alternating current stimulation (tACS) in humans.
• To determine if stimulating frontal and cingulate cortices with specific theta-gamma phase relationships affects cognitive control performance.

Main Methods:

• A double-blind, randomized, repeated measures study involving 24 healthy participants.
• Application of four tACS conditions: three active (peak-coupled, trough-coupled, amplitude-modulated theta-gamma CFC) and one control (non-specific CFC).
• Participants performed a Go/NoGo instrumental learning task during 20-minute stimulation sessions.

Main Results:

• Trough-coupled and amplitude-modulated theta-gamma CFC tACS significantly reduced performance on conflicting trials compared to the control condition.
• Peak-coupled theta-gamma CFC tACS showed no significant effect on behavioral performance.
• Bayesian hierarchical logistic regression analysis supported these findings.

Conclusions:

• Cognitive control performance is dependent on the phase specificity of theta-gamma cross-frequency coupling.
• Targeting specific phases of theta-gamma CFC, particularly the trough, can negatively impact cognitive control, suggesting a critical role in adaptive decision-making.