Visual oddball event-related electrophysiological data for the target conditions were analyzed. Mean values were calculated from the S-transform TFR for use as phenotypes within time-frequency regions of interest (TFROIs) that are specified by frequency band ranges and time intervals [Lachaux et al., 2003]. This study focused on the total amplitude of the theta (4.0-7.0 Hz) frequency band in the 300-700 ms time window range, which corresponds to the P300 latency window in the event-related waveforms measured at the frontal midline channel (Fz electrode) (see Figure 1), a brain region where theta oscillations have been found to be strongly concentrated for the P300 response [Karakas et al., 2000b]. This TFROI was established by examination of target condition grand-mean TFRs and selecting a time region that bound observed stimulus evoked increases in theta band energy relating to a subcomponent of the P300 ERP. Similar to the P300 ERP amplitude, the theta ERO phenotype showed a significant age effect and thus age was included as a covariate in the genetic analyses.
