eegmp_preproc/code

EEG Preprocessing

Steps 1-4 create filters (e.g., from the ICA, segment labeling), which later get applied to the raw data starting in step 5.

All steps use FieldTrip and were executed within MATLAB 2020a.

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01_prepare_preprocessing

• Prepare for ICA
• Read into FieldTrip format
• Switch channels
• EEG settings: o Referenced to avg. mastoid (A1, A2) o downsample: 1000Hz to 250 Hz o 4th order Butterworth 1-100 Hz BPF o no reref for ECG

02_visual_inspection

• Check for gross noise periods that should not be considered for ICA

03_ica

• Conduct initial ICA1, this should be run on tardis

04_ica_labeling

• Manual labeling of artefactual ICA components

05_segmentation_raw_data

• Segmentation: -1500 ms relative to fixcue onset to 1500 ms after ITI onset
• Load raw data
• Switch channels
• EEG settings: o Referenced to avg. mastoid (A1, A2) o 0.2 4th order butterworth HPF o 125 4th order butterworth LPF o demean o recover implicit reference: A2 o downsample: 1000Hz to 500 Hz

06_automatic_artifact_correction

• Automatic artifact correction, interpolation
• Remove blink, move, heart, ref, art & emg ICA components prior to calculation
• get artifact contaminated channels by kurtosis, low & high frequency artifacts
• get artifact contaminated channels by FASTER
• interpolate artifact contaminated channels
• equalize duration of trials to the trial with fewest samples o This is a hack. Apparently, we did not always get consistent timing on each trial, such that some trials were a bit shorter. To include these trials, I cut every trial to the lowest trial length. o Interpolation to a general length may be the better option.
• get artifact contaminated epochs & exclude epochs recursively
• get channel x epoch artifacts
• Note that this does NOT yet remove anything. We only calculate the data to be removed in the next setp (I).

07_prep_data_for_analysis

• Remove blink, move, heart, ref, art & emg ICA components
• Interpolate detected artifact channels
• Remove artifact-heavy trials, for subjects with missing onsets, the missing trials are included here as ‘artefactual trials’, hence correcting the EEG-behavior assignment:

08_assignConditionsToData

• Remove additional channels
• Load behavioral data and add information to data