ERO, PLI (phase lock index) and PDLI (phase difference lock index) analyses were accomplished from the same datasets that were used to generate ERP data reported in two previous publications in humans and animals (Ehlers et al., 1998a, 1998b). Data from each ERP trial generated by the auditory stimuli were prepared for time-frequency analysis by subtracting from each trial its mean prestimulus value, windowing the first and last 100 msec with a cosine function, and padding with zeroes for a total of 512 data points. The time-frequency analysis of EROs utilizes the S transform (Stockwell et al., 1996). The computer code for this is based closely on a C language S transform subroutine downloaded from the NIMH MEG Core Facility web site (http://kurage.nimh.nih.gov/meglab/).
