NeuroAnalyzer tutorials: Analyze: Lateralization index and asymmetry index

using NeuroAnalyzer
eeg = load("files/eeg.hdf");

Lateralization index is calculated as log(A / B), where A is average power at given frequency (default is 10 Hz, alpha) for the right hemisphere and B is average power at that frequency for the left hemisphere.

Lateralization index (default for alpha 10 Hz frequency):

lidx = lat_idx(eeg)

1.5173798065603747

Lateralization index for the range 8.0-12.5 Hz:

lidx = lat_idx(eeg, frq=(8.0, 12.5))

1.4688999711396036

Calculate frontal alpha asymmetry index:

# left
ch_left = channel_cluster(eeg, cluster=:f1)
# or
ch_left = channel_pick(eeg, p=[:left, :frontal])
# right
ch_right = channel_cluster(eeg, cluster=:f2)
# or
ch_right = channel_pick(eeg, p=[:right, :frontal])

# alpha frequency
alpha = band_frq(eeg, band=:alpha)

# asymmetry index
band_asymmetry(eeg,
               frq_lim=alpha,
               ch1=labels(eeg)[ch_left],
               ch2=labels(eeg)[ch_right])

(ba = -2.6469560812055706,
 ba_norm = -0.8676462643674967,)

Calculate channel symmetry:

symmetry(eeg, ch=["F3", "F4"])

2×1 Matrix{Float64}:
 0.9952395736313774
 0.9753212906696037

(!) Channel symmetry is the ratio of positive to negative amplitudes. Perfectly symmetrical signal has symmetry of 1.0. Symmetry above 1.0 indicates there are more positive amplitudes.