Resting State EEG

Motivation:

To detail processing of resting state EEG data that is collected from Conte. Resting state data was only collected for Version 3 of Conte and was collected in both an eyes open and eyes closed condition. Data collection occurred in the following order: 1 minute of eyes open, 1 minute of eyes closed, 1 minute eyes open, 1 minute eyes closed. The resting state recordings occurred at the beginning of the EEG session (so before the tasks were run). During the recording, subject were asked to sit still with their eyes open, blinking normally, and then sit still with their eyes closed.

File locations:

All files are located on Odin:

/Electrophysiology/CONTE_DATA/eeg_v3_6_2016/resting_closed
/Electrophysiology/CONTE_DATA/eeg_v3_6_2016/resting_open

The files are labeled O1_bblid.bdf, O2_bblid.bdf, C1_bblid.bdf, and C2_bblid.bdf

When working with a data set (either the eyes open or eyes closed), all of the raw, processed, and history files live in a workspace. The below listed are the workspaces that are processed fully:

/Electrophysiology/CONTE_DATA/eeg_v3_6_2016/resting_closed/Resting_Closed.wksp2
/Electrophysiology/CONTE_DATA/eeg_v3_6_2016/resting_open/resting_open.wksp2

Within the folders resting_closed and resting_open live raw files and history files. History files are the edited versions, deleting these will delete the work you have done and when reloading the workspace, blank history files will be created.

Working in Brain Vision Analyzer

All data was processed and extracted using Brain Vision Analyzer. Brain Vision Analyzer only works on Windows machines, so it will have to be installed via Parallels Desktop if you are using a Mac. The current version of Brain Vision Analyzer used for this data analysis is 2.0. A user manual for Brain Vision Analyzer can be found on Odin in /Electrophysiology/CONTE_DATA/BrainVisionAnalyzer_UserManual.pdf

Processing steps

• Before any processing occurs, the first and second minutes of recordings were merged together for each condition (O1 and O2 for eyes open and C1 and C2 for eyes closed).
• Data was then visually inspected for excessive artifact and high frequency oscillations that are above normal wavelengths
• If abnormal frequencies were noticed, data was filtered at 60Hz for the electrodes that were affected
• Once visual inspection occurred, a history file was applied to the data. A history file contains sets of processing steps that occur and can be applied for each subject.
  • The history file (located: /Electrophysiology/CONTE_DATA/eeg_v3_6_2016/AVC/AVC_Conditioning_Part1.ehtp) contains the following steps:
    • Linear Derivation: References electrodes to linked mastoids
    • Filters: Filtered out noise in the data below 0.5Hz and above 70Hz.
    • Raw Data Inspection: Marked amplitudes above 1000µV and below -1000µV as bad; this included 200ms before the bad amplitude occurred.
    • Ocular Correction: Using the VEOG channels, corrected all electrodes for facial muscle movement
    • Raw Data Inspection 2: Marks amplitudes above 75µV and -75µV as bad; bad segments include 200ms before the bad amplitude occurred.

Post Processing Steps

Once the data was cleaned and ready to be extracted, data was the processed for Frequency Spectrum data extraction. The history file for this step is located:/Electrophysiology/CONTE_DATA/eeg_v3_6_2016/Resting_Closed/Resting_FFT.ehtp. This included:

• Segmentation: This is the first step to beginning to get the data ready for frequency spectrum data extraction. This segments the data into 2 second artifact free epochs.
• FFT: This step Fast Fourier Transforms the 2 second segments into the frequency spectrum. The resolution (because it is 2 seconds) is 0.5Hz; the full spectrum was used with a 10% Hanning window (no window variance correction and a symmetric window).
• Average: This next step averages the FFT spectrum results across all segments to get an average frequency for each electrode for frequencies from 0.5-70Hz.

Data Extraction

Data extraction occurred for theta (0-3.5Hz), delta (4-7.5Hz), alpha (8-12.5Hz), beta (13-30Hz), and gamma (30-50Hz). Data was extracted for mean power for all electrodes. Extracted data can be found in the Conte REDCap under Resting Eeg Closed and Resting Eeg Open.