Fig. 5
From: Benchmarking the utility of dry-electrode electroencephalography for clinical trials
Visual gamma activity. (a) Participants quietly maintained fixation on a centrally displayed fixation dot without additional active behavioral tasks. After a variable baseline, a visual stimulus consisting of a contracting grating was displayed around the fixation dot for 1 s. (b) Time frequency representation (TFR) of EEG activity averaged across all available trials and recordings for electrodes that are part of a posterior-occipital region of interest available across devices (102,010–20 system electrodes O1, O2, P3, Pz, P4, C3, Cz, C4). White boxes define the definitions of the TFR features used for ICC analysis (see d), where the same electrodes and the respective time frequency bins within the indicated area of the TFR have been averaged per patient. Combined alpha and beta activity (ɑ/ꞵ) was defined as 0.05–1.5 s post stimulus onset and 10–20 Hz. Transient gamma activity (γt) was defined as 0.05–0.5 s post stimulus onset and 50–75 Hz. Sustained gamma activity (γs) was defined as 0.5–1 s post stimulus onset and 50–75 Hz. (c) Robustness and extent of the induced activity per device. Results from a non-parametric cluster based significance test of the signal power change across the entire time, frequency and electrode space. For all significant clusters (pFWER < 0.05, random permutation test), percentages of contributing electrodes (for the TFR) and time–frequency bins of the TFR regions of interest (for the topographies) are being displayed. The TFR regions of interest are defined in b. Clusters with a positive change from baseline are depicted in red color, clusters with a negative change from baseline are depicted with a blue color. (d) Intraclass correlations (ICC) for alpha (ɑ), transient (γt) and sustained gamma (γs) power change (see B). The absolute agreement and consistency are shown for each device as compared to the standard EEG. The test–retest reliability compared the features between the test (Day 1) and retest (Day 8) recordings. The standard EEG was also subsampled at the electrodes present consistently for the dry electrode devices, see [Std. EEG (1020)], to allow for a comparison of ICC values based on comparable electrode configurations between devices.
