Coherence

Coherence (magnitude-squared coherence) is a frequency-domain measure of the linear correlation between two signals, with values ranging from 0 (no correlation) to 1 (perfect correlation) at each frequency.

Why it matters: Coherence reveals functional connectivity between brain regions — high coherence at a specific frequency indicates synchronized neural oscillations, suggesting information flow or shared processing.

Common applications: Inter-area coupling during cognitive tasks, beta-band coherence in motor circuits, theta coherence in hippocampal-cortical communication, and gamma coherence in sensory processing.

Computation: Estimated from cross-spectral density divided by the product of auto-spectral densities. Requires sufficient trial averaging for reliable estimates.