The significant group effect on the δ1 EROEVK power indicates that the phase-locked (i.e. evoked) activity in the lower δ band discriminates the groups. The δ1 EROTOT power, comprising both evoked and non-phase-locked activity also significantly discriminates the groups. As the effect size is smaller for the δ1 EROTOT power compared to the δ1 EROEVK power, it is most likely that the non-phase-locked activity does not contribute to the significant group effect, and it is only the evoked activity in the lower δ band that account for the significant group differences. Had the non-phase-locked activity contributed, the effect size of the δ1 EROTOT power would have been larger than the effect size for the δ1 EROEVK power. The finding that the θ1 and θ2 EROTOT power measures discriminate the groups, while the θ1 and θ2 EROEVK power measures do not, indicates that it is most likely the contribution of non-phase-locked activity to the θ EROTOT power that accounts for the significant group effect. If evoked activity discriminated the groups, then the θ EROEVK power would have shown a significant group effect as well. Only separating the measurement of phase-locked and non-phase-locked power could directly address this issue.
