Cross-Frequency Coupling
Theta (4-8 Hz) → Gamma (30-80 Hz): phase-amplitude coupling, PAC comodulogram
Phase Signal (θ)
θ freq (Hz)
6.0
θ amplitude
1.00
θ noise
0.05
Low-frequency theta phase modulates high-frequency gamma amplitude. Classic hippocampal mechanism.
Amplitude Signal (γ)
γ freq (Hz)
60
γ base amp
0.20
CFC strength
0.70
Phase offset
0
γ envelope = base + CFC·(1+cos(θ_phase+offset))/2. Controls which theta phase drives peak gamma.
PAC Comodulogram
Phase f_low
6
Amp f_high
60
Right panel: amplitude vs phase angle (modulation index). Bottom: comodulogram heatmap. Peak indicates coupling frequency pair.