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Fig. 4.2: The first selected EEG segment and ICA results from patient 1. Once W
and S were resolved by ICA (Equation 4.5), rows of S representing the temporal
waveforms of independent sources were displayed in (
d
), and each column of W-1
denoting the relative (spatial) weightings of each sources was depicted as a topogra-
phy map in (
e
). (
a
) A 15-s time window (2-17 s) within 5-min data used to display
results in (
b
) and (
d
). (
b
) The illustration of a 15-s segment where signals in the
shaded areas were severely contaminated by large eye movements and environmen-
tal noises. (
c
) The topographical maps generated at four peak time points p1, p2,
p3, and p4 (
vertical lines
in
b
) of four waves in IC3 at 3.3, 5.1, 9.6, and 10.9 s. (
d
)
The 17 decomposed ICs show that diseased-related pattern was PLEDs (IC3) and
the artifacts were eyeblinks (IC2), eye movements (IC8), and noise (IC11). (
e
)The
corresponding spatial maps of IC2, IC3, IC8, and IC11.
EEG recordings are overlapping potentials contributed from individual neurons
inside the brain as well as from the artifacts produced outside the brain [5]. Fig-
ures 4.2b, 4.3b, and 4.4b illustrate parts of typical segments of raw EEG signals
recorded from the first admissions of patient 1 (the early stage of CJD). The shaded
areas show that the brain activities are severely contaminated by significantly large
eye-movement potentials and environmental noises, which makes the visual inspec-
tion of FIRDA, PLEDs, and tirphasic waves in the early stage of CJD a difficult task.
