Abstract
<p>Episodic memory formation requires integrating multisensory information. Inspired by animal research on how hippocampal theta oscillations modulate long-term potentiation, recent human studies have demonstrated that memory for auditory and visual stimuli modulated synchronously at theta frequency (4 Hz) is better than when those stimuli are modulated asynchronously; the so-called Theta-Induced Memory Enhancement (TIME) effect. However, recent failures to replicate the TIME effect question its robustness and dependence on other variables. One such variable may be inter-individual differences in neural sensitivity to the precise phase lag between auditory and visual streams. In this online study, we therefore tested a wider range of phase lags between 4 Hz modulated audio and visual stimuli. Using simulation methods from Zoefel et al. (2019), we estimated the sample size to achieve 90% statistical power to detect an optimal phase lag that varied across participants. However, this sample size showed no evidence that some phase lags produced better performance than others, thereby failing to replicate the TIME effect regardless of whether or not the optimal lag was assumed to vary across participants. Indeed, Bayes Factors supported the null for most analyses, and a follow-up analysis showed no evidence that the TIME effect depended on overall memory performance. Therefore, the present work adds to the growing number of non-replications of the TIME effect, though the reason for these failures remains unclear.</p>