Skin-Conductance Response Function (SCRF)

First-class canonical skin-conductance response kernel used throughout PhysioEDA as the single source of the SCR shape (simulation, CDA / cvxEDA deconvolution, and GLM designs). The response is the biexponential (Bateman) function h(t) = exp(-t / tau2) - exp(-t / tau1) for t >= 0 (0 otherwise), optionally augmented with a Gaussian bump for the PsPM-style canonical form (Bach et al., 2010). Both the kernel and its first/second time-derivatives are available (the derivatives drive GLM temporal/dispersion regressors).

Usage

scrf(
  t,
  tau1 = 0.75,
  tau2 = 2,
  form = c("bateman", "pspm_canonical"),
  normalize = c("peak", "area", "none"),
  deriv = 0,
  bump_amp = 0.3,
  bump_center = NULL,
  bump_sd = 0.7
)

Arguments

t

Numeric vector of times in seconds. Values < 0 return 0.

tau1

SCR rise time constant in seconds (default: 0.75).

tau2

SCR decay time constant in seconds (default: 2.0). Must differ from tau1; the canonical shape has tau2 > tau1.

form

Kernel family: "bateman" (pure biexponential) or "pspm_canonical" (biexponential plus a Gaussian bump).

normalize

Normalisation of the kernel: "peak" (unit maximum, the default), "area" (unit integral), or "none" (raw). Derivatives are scaled by the same constant.

deriv

Derivative order to return: 0 (kernel), 1, or 2.

bump_amp

Gaussian bump amplitude, relative to the raw Bateman peak, for form = "pspm_canonical" (default: 0.3; ignored otherwise).

bump_center

Gaussian bump centre in seconds (default: the analytic Bateman peak time).

bump_sd

Gaussian bump standard deviation in seconds (default: 0.7).

Value

A numeric vector the same length as t: the requested derivative of the (optionally normalised) response kernel.

References

Bach, D.R., Flandin, G., Friston, K.J., & Dolan, R.J. (2010). "Modelling event-related skin conductance responses." International Journal of Psychophysiology, 75(3), 349-356. doi:10.1016/j.ijpsycho.2010.01.005

See also

scrfPeak for the analytic Bateman maximum, edaSimulate and edaDecompose which consume it.

Examples

t <- seq(0, 15, by = 0.1)
k <- scrf(t)                       # unit-peak Bateman kernel
dk <- scrf(t, deriv = 1)           # its temporal derivative
ck <- scrf(t, form = "pspm_canonical")