Analysis.
  1. Subjective and behavioral measures were assessed with analysis of variance using peak change score from baseline, using individual paired samples T-tests to measure the differences between Placebo vs MA and Placebo vs MDMA. Peak drug effects were calculated by subtracting the baseline values from the highest or lowest value during the session.
  2. Faces Ratings Task (supplementary results). Participants rated the valence and arousal of each of the 6 faces seen in the emotional oddball task (male and female; angry, happy, neutral). These ratings were analyzed using two 3x2 (Emotion x MDMA (vs PLC); Emotion x MA (vs PLC)) ANOVAs.
  3. Emotional Faces Oddball Task. The N170 was measured at electrode PO8, extracting the mean peak from 150-200ms post stimulus onset. The P300 was measured at electrode parietal (Pz) extracting the mean peak between 300-400ms. The MMN was measured using electrodes Fz between 240-350ms. For each of these peaks of interest, two 3 (Emotion) x 2 (Drug condition; Drug vs PLC) repeated measures ANOVAS were conducted. We also examined ERP responses to the frequent cartoon faces for MMN to compare frequent vs infrequent stimuli. Initial analyses (supplementary materials) revealed that responses to the (infrequent) human faces differed from markedly from responses to the (frequent) cartoon face on all three ERP measures. The final analyses were conducted only with the human faces, comparing MDMA and MA vs PLC separately.
Results .
Demographics. Participants were 17 men and 8 women, mean age of 27.4 years, most of whom had completed partial college (Table 1). Participants had previously taken MDMA a mean of 7.1 times. None of the subjects were cigarette smokers. Sixty-four percent of participants correctly identified Placebo, 20% MA and 52% MDMA, showing the effectiveness of the blinding (Supplementary Table 1).
Table 1 . Demographic information and nonmedical drug use (N=25).