What is Phase-Locked?
Phase-Locked stimulation means synchronizing an external stimulus (e.g., sound, light) with the phase of an internal biological oscillation (e.g., slow-wave sleep, delta waves). The external signal "locks" to the internal rhythm to amplify or entrain it.
Key Applications
- •Sleep — acoustic stimulation phase-locked to slow-wave sleep can enhance delta amplitude
- •EEG — frequency-following response to binaural beats
- •Precision — requires real-time detection of the internal rhythm (e.g., via EEG or actigraphy)
Why does Phase-Locked matter?
Phase-locking matters because it shows when two rhythms keep a consistent timing relationship, which often signals that they are coordinated. In the body, this helps explain how separate oscillating systems work together.
Examples include neurons firing at a consistent point in a brain wave, or heart rhythm aligning with breathing. In neuroscience, phase-locked activity is thought to help brain regions share information efficiently.
How is Phase-Locked measured?
Phase-locking is measured by extracting the phase of each rhythm over time and checking how consistent the difference between them stays. If the gap between the two cycles remains stable, the signals are considered phase-locked; if it drifts randomly, they are not.
Researchers commonly use measures such as the phase-locking value or inter-trial phase coherence, which range from no consistency to perfect consistency. The phase is usually calculated with mathematical tools like the Hilbert transform or wavelet analysis after filtering the signal to a frequency band of interest. Results must be interpreted carefully: shared noise, filtering choices, or a common outside driver can create apparent phase-locking even when two systems are not directly interacting.
In ONDA Life
The Phase-Locked Sleep article covers delta amplification protocols using phase-locked acoustic stimulation.