ERP-aligned delta transcranial alternating current stimulation modulates the P3 amplitude

The underlying mechanisms of the event-related potential (ERP) generation are still under debate. One popular model considers the ERP as a superposition of phase-resets of ongoing endogenous oscillations of different frequencies. Brain oscillations have been shown to be modulated by transcranial alternating current stimulation (tACS). Thus, it seems feasible, that an ERP could be altered by modulating the contributing oscillations using tACS. One possible approach would be to target a frequency-matched stimulation signal to a specific ERP-component. One possible target for such an approach is the P3, which appears as delta/theta oscillations in the frequency-domain. Thus, an ERP-aligned stimulation in the delta/theta-range might be suitable to force synchronization in the stimulated frequency band and thus increase the amplitude of the P3 component. Building on an existing paradigm, in the present study 21 healthy participants received individualized ERP-aligned delta tACS and control stimulation while performing a visual task. The visual stimulation was matched to the continuous tACS in order to align the tACS peak with the P3 peak. Both the P3 amplitude and the evoked delta power were significantly increased after ERP-aligned tACS but not after control stimulation. The investigated behavioral parameter showed no stimulation dependent effect. Our results may provide new insights into the debate on the contribution of phase-reset mechanisms to the generation of ERPs and offer new opportunities for clinical trials.