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.