PMC4832091_01
fMRI model derivation from EEG frequency decomposition (models 3 and 4).. (a) Data from a selected contact (e.g. in the figure right amygdala showing sz onset) for the pre-ictal (- 30 s from seizure onset) and ictal phase (+ 21.2 s from seizure onset) was wavelet transformed to a representation in time (x) and frequency (y). (b) The data was convolved with a haemodynamic response and averaged within the beta and gamma bands. This procedure was repeated for each channel and the resulting regressors were entered into a design matrix (model 3). (c) A principal component analysis was performed to reduce the time-frequency data into the smallest number of regressors able to explain 90% of the data variance. These regressors were the effects of interest in model 4.
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PMC4832091_01_gr1.jpg
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The resulting time courses were converted into a z-score for each frequency and convolved with the canonical HRF (see Fig. 1).