Aperiodic (1/f) spectral parameterization of EEG

Separates each channel's power spectrum into an aperiodic (1/f) component and periodic (oscillatory) peaks, following the specparam / FOOOF model (Donoghue et al. 2020). The aperiodic exponent is a widely used index of the excitation/inhibition balance and cortical state. Delegates the fit to PhysioAnalysis::specparam().

Usage

eegAperiodic(
  pe,
  freq_range = c(1, 45),
  aperiodic_mode = c("fixed", "knee"),
  max_n_peaks = 6L,
  peak_width_limits = c(1, 12),
  min_peak_height = 0.05,
  peak_threshold = 2,
  assay_name = NULL
)

Arguments

pe: A PhysioExperiment.
freq_range: Frequency range to fit, in Hz (default c(1, 45)).
aperiodic_mode: "fixed" (offset + exponent) or "knee" (offset + knee + exponent), the latter for spectra with a bend in log-log space.
max_n_peaks: Maximum number of oscillatory peaks per channel (default 6).
peak_width_limits: Min/max peak width in Hz (default c(1, 12)).
min_peak_height: Minimum peak height above the aperiodic fit (default 0.05).
peak_threshold: Peak detection threshold in SD of the flattened spectrum (default 2).
assay_name: Assay to use (default: the object's default assay).

Value

An eeg_aperiodic object: a list with aperiodic (per-channel data frame: channel, exponent, offset, optionally knee, r_squared, error), peaks (per-channel CF/PW/BW), exponent (a named per-channel vector, e.g. for eegPlotTopomap()), and the underlying specparam_result.

References

Donoghue et al. 2020, Nat Neurosci (specparam / FOOOF).

Examples

if (requireNamespace("PhysioAnalysis", quietly = TRUE)) {
  pe <- make_eeg(n_time = 2500, n_channels = 8, sr = 250)
  ap <- eegAperiodic(pe, freq_range = c(2, 40))
  ap$aperiodic          # per-channel exponent / offset
}
#>   channel    offset exponent r_squared     error
#> 1     Fp1 1.0569143 1.899793 0.9517044 0.1794116
#> 2     Fp2 0.9976620 1.893552 0.9729035 0.1329855
#> 3      F7 0.7323077 1.689029 0.9699991 0.1272416
#> 4      F3 0.9299269 1.865744 0.9517095 0.1647729
#> 5      Fz 0.7507181 1.747007 0.9560722 0.1427750
#> 6      F4 0.9321072 1.853310 0.9602022 0.1416420
#> 7      F8 0.9810790 1.895442 0.9554800 0.1608447
#> 8      T3 1.0408772 1.930276 0.9532819 0.1750132