Decompositions were performed using averaged data, which enhanced brain activity that was consistently phase-locked to the stimulus, while attenuating non-phase-locked (e.g. induced) activity. This method provided the most direct parallel to the extant body of research on P3, thus allowing greater comparability to relevant P3 findings. Further, given our goal of exploring TF components as potential endophenotypes for externalizing, we sought to extend our previous findings by focusing current analyses on the same group of subjects used in Iacono et al. (2002), which characterized the relationship between P3-AR and externalizing disorders, and by utilizing the TF-PCA method of Bernat et al. (2007), which characterized the TF components associated with the P3 ERP. Therefore, to optimize the signal to noise ratio and stability of the components in the PCA decomposition, the TF-PCA was carried out using the 17-year-old sample described in Bernat et al. (N=2068), which included the subjects used in the current report, supplemented by the addition of 17-year-olds whose data have more recently become available (providing a total N=2084). Decompositions were performed on a frequency range of 0 –
