Liveamp

Electroencephalography measures were collected via a 15-channel EEG system (LiveAMP, Brain Products, Munich, Germany) with electrodes positioned over Fp1, Fp2, F3, Fz, F4, T7, T8, C3, Cz, C4, P3, Pz, P4, O1, and O2 (Figure 2A), adopting the 10/20 system of electrode placement (Jasper, 1958 ). An ElectroCap was used for signal recording. Data were acquired with a frequency band between 0.01 and 40 Hz and a sampling rate of 500 Hz. The electrode impedance for each individual was monitored before data collection and was kept <5 kΩ. Portions of data that presented artifacts were removed in order to increase the specificity. Ocular artifacts (blinks and eye movements) were corrected using an eye movement correction algorithm via a regression analysis in combination with artifact averaging (Sapolsky, 2004 (link)). Finally, a standard independent component analysis (ICA) analysis was applied. The EEG data were band-pass-filtered (0.1–40 Hz, 48 dB/octave roll-off), and frequency power data were computed by fast Fourier transformation (FFT) for standard frequency bands: delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), and beta (14–20 Hz) (Keil et al., 2001 (link)).

Electroencephalography data were recorded using a wireless 32-channel EEG system (LiveAmp, Brain Products Inc., Gilching, Germany). In order to minimize the influence of head motion on the EEG recordings, we used an EEG system with active electrodes, fixated the EEG cables with straps to minimize their motion, and also placed a stretchable mesh cap that assisted in maintaining the electrodes with the decided contact to the scalp across the recording. The channels recorded in this experiment were: FP1, FP2, Fz, C3, C4, Cz, and Pz. The sampling rate was set to 500 Hz. This EEG system is a gel-based system with active electrodes. Head accelerations were acquired in the vertical, anterior-posterior and medial-lateral directions simultaneously with the EEG recordings sampled at 500 Hz. The accelerometer was in-built in the EEG system and was fixed at the head embedded in the EEG cap at the basis of the cranium.

EEG activity was recorded via an EEG wireless System (Live-Amp) and processed via Analyzer2 software (Brain Products GmbH, Gilching, Germany). The montage included 15 active electrodes (Fp1, Fp2, AFF3h, Fz, AFF4h, T7, C3, Cz, C4, T8, P3, Pz, P4, O1, O2; placement according to the 10–20 International System [59 ]. Electrode impedance was monitored for each subject prior to data collection and kept under 5 kΩ. Data were acquired using a sampling rate of 250 Hz and then filtered offline with a 0.5–45 Hz IIR bandpass filter (slope: 48 dB/octave). Data were then segmented and visually inspected for ocular, muscle, and movement artifacts. Fast-Fourier transform (Hamming window, resolution: 0.5 Hz) was applied to artifact-free segments to compute the average power spectra. Finally, the average power for the main EEG frequency bands (Delta—0.5–3.5 Hz, Theta—4–7.5 Hz, Alpha—8–12.5 Hz, and Beta—13–30 Hz) was extracted. 120-second resting baseline was registered at the beginning of the experiment before the picture series. We used this period as baseline for the successive analysis.
In the statistical analysis of the data, factors such as the lateralisation (left/right hemisphere) and the three regions of interest (ROI) grouping frontal (F: Fp1; Fp2; AFF3h; AFF4h), temporo-central (TC: T7; T8; C3; C4), and parieto-occipital (PO: P3; P4; O1; O2) electrodes were considered.