EEG Measures.
Data collection and Processing. A 64 channel
electro-geodesic net was used (Magstim, EGI). Electrodes were soaked in
a saline solution then placed on the head using measurements from nasion
to inion and mastoid to mastoid. EEG data was acquired continuously,
amplified, and digitized using Netstation software, sampled online at
1024Hz. Offline EEG recordings were analyzed using EEGLab (Delorme &
Makeig, 2004) it was first down sampled to 512Hz then high pass filtered
(1 Hz), and low pass filtered (60 Hz, -12 dB/octave) to remove
extraneous high and low frequency noise. Data were visually inspected
for movement and electronic artifact. PICARD Independent Components
Analysis (Ablin, Cardoso & Gramfort, 2017) were performed to correct
for EEG artifacts including blinks, horizontal and vertical eye
movements, muscle movement and EKG signal. Data were segmented from -200
to 1000ms and baseline corrected following stimulus presentation for
each of the stimulus types.
Emotional Oddball Task (Raz et al., 2014). To assess the neural
responses to emotional stimuli, participants completed an emotional
oddball task. The task consisted of 300 stimulus presentations, of which
80% were cartoon faces, and 20% were human faces. The stimuli were
presented in three blocks of 100 stimuli consisting of the frequent
cartoon image interspersed with infrequent angry, happy, or neutral
faces. Subjects were instructed to respond on the left key on a button
box when they saw a human face and, on the right when they saw a cartoon
face. ERPs were recorded during each stimulus presentation.