Target Engagement for Oxytocin: Dose Ranging Study

Primary outcomes

1. Mu Suppression on EEG

   Time frame: Baseline, 1 Week

   This primary outcome measure is mu suppression recorded during a biological motion task. In this task, participants view point-light walker (PLW) animations of a human; the PLWs were either male or female, happy or sad, or walking towards or away from the viewer. In addition to the humans, there was a control condition which consisted of a circle moving either left or right. In separate blocks, participants had to identify either the gender, the emotion, or intention (i.e., direction) of the walker, or the direction of the circle, while their EEG was recorded. The primary measure was mu activity (8-12 Hz) recorded over 3 central electrodes. Mu suppression was calculated as the log10 transformed ratio of mu power to one of the three human conditions compared to the circle: log10(human/circle). A negative value indicates suppression of mu activity to human walkers vs. circles. We are presenting the mean (SD) of this suppression ratio collapsed over the 3 human conditions.

2. Pupil Dilation While Observing Faces

   Time frame: Baseline, 1 Week

   This primary outcome measure is pupil size recorded during a facial affect identification task. In this task, participants view faces portraying happy, afraid, or neutral faces; scrambled images of the faces were also shown. There were 64 trials: 16 trials per each image type. The primary measure was the difference in pupil size averaged over the happy and fearful faces from the scrambled face condition. A positive value indicates greater pupil dilation relative to the scrambled face; a negative value indicates greater pupil constriction relative to the scrambled face.

   Baseline was defined as the median pupil width 1 second prior to stimulus onset. Pupil sizes during each trial were baseline-corrected by dividing them by baseline median width. Resulting pupil size timecourses were averaged within-subject for each type of stimulus (happy, afraid, neutral, scrambled). The primary dependent variable was computed by taking the average of the change in pupil size between 1 and 3 s.