Brain Symmetry Index (BSI) and pairwise-derived pdBSI

Quantifies left/right spectral asymmetry across hemispheric electrode pairs, a quantitative-EEG stroke marker (van Putten 2007; Sheorajpanday et al. 2011). The global bsi is the spectrum-averaged absolute relative difference between summed right- and left-hemisphere power, bounded from 0 (symmetric) to 1 (one hemisphere silent). The pairwise-derived pdbsi averages the same relative difference per hemispheric pair; with directed = TRUE it keeps the sign (positive = right-dominant). Both are returned as reliability-characterised physioBiomarker objects with provenance and, for the global BSI, a normative reference range.

Usage

eegBSI(
  x,
  pairs = NULL,
  band = c(1, 25),
  directed = FALSE,
  method = "welch",
  age = NULL,
  montage = NULL,
  reliability = list(icc = NA_real_, sem = NA_real_),
  assay_name = NULL
)

Arguments

x

A PhysioExperiment object with 2D EEG data.

pairs

List of length-2 character vectors, each a c(right, left) hemispheric electrode pair. Defaults to the standard 10-20 hemispheric pairs.

band

Numeric length-2 frequency band in Hz (default: c(1, 25)).

directed

Logical; when TRUE the pairwise index keeps its sign (default: FALSE).

method

Spectral estimator (default: "welch").

age

Optional numeric age for the normative lookup.

montage

Optional character montage for the normative lookup.

reliability

Named list of reliability indices to attach (default: icc and sem placeholders).

assay_name

Input assay name (default: the default assay).

Value

A named list with two PhysioBiomarker objects: bsi (global, from 0 to 1) and pdbsi (pairwise-derived, signed when directed = TRUE).

References

van Putten, M. J. A. M. (2007). The revised brain symmetry index. Clinical Neurophysiology, 118(11), 2362-2367.

Sheorajpanday, R. V. A., et al. (2011). Quantitative EEG in ischemic stroke: correlation with functional status after 6 months. Clinical Neurophysiology, 122(5), 874-883.

See also

eegDAR(), eegAsymmetry(), PhysioCore::physioBiomarker()

Examples

if (FALSE) { # \dontrun{
pe <- make_eeg(n_time = 5000, n_channels = 19, sr = 250)
res <- eegBSI(pe, age = 60)
res$bsi
} # }