Phase Locking Value (PLV)

Computes the Phase Locking Value between two signals, measuring the consistency of phase difference across time. A PLV of 1 indicates perfect phase locking; a PLV of 0 indicates no consistent phase relationship.

Usage

phaseLockingValue(
  x,
  y = NULL,
  sr = NULL,
  freq_band,
  method = c("hilbert", "wavelet"),
  modality_x = NULL,
  modality_y = NULL,
  channels_x = 1L,
  channels_y = 1L
)

Arguments

x: Numeric vector, PhysioExperiment, or MultiPhysioExperiment.
y: Numeric vector or PhysioExperiment (NULL when x is an MPE).
sr: Numeric sampling rate in Hz (required when x/y are numeric).
freq_band: Numeric vector of length 2 specifying the frequency band c(low, high) in Hz. Required.
method: Character; phase extraction method. Currently only "hilbert" is supported. "wavelet" is reserved for future use.
modality_x: Character modality name in MPE for x signal.
modality_y: Character modality name in MPE for y signal.
channels_x: Integer channel index to extract from x (default 1).
channels_y: Integer channel index to extract from y (default 1).

Value

A named list with components:

plv: Numeric scalar in [0, 1] – the Phase Locking Value.
phase_diff: Numeric vector of instantaneous phase differences (radians, [-pi, pi]).

Details

The signals are bandpass-filtered to freq_band and then Hilbert- transformed to extract instantaneous phase. PLV is computed as: $$\text{PLV} = \left|\frac{1}{N} \sum_{t=1}^{N} e^{i(\phi_x(t) - \phi_y(t))}\right|$$

References

Lachaux, J.-P., Rodriguez, E., Martinerie, J., & Varela, F. J. (1999). Measuring phase synchrony in brain signals. Human Brain Mapping, 8(4), 194–208.

Examples

# Two phase-locked sinusoids
sr <- 500
t <- seq(0, 2, length.out = sr * 2)
x <- sin(2 * pi * 10 * t)
y <- sin(2 * pi * 10 * t + pi / 4)
result <- phaseLockingValue(x, y, sr = sr, freq_band = c(8, 12))
result$plv
#> [1] 0.993784