Task-related changes in resting state connectivity are affected by temporal interference (TI) stimulation

BACKGROUND: Resting-state metrics, such as brain network activity and functional connectivity (FC), are influenced by preceding cognitive tasks, such as memory formation. Brain stimulation can modulate brain network activity and FC during the resting state. However, it is unknown whether it can acutely modulate activity or FC traces of preceding cognitive tasks. OBJECTIVES: We evaluated whether non-invasive temporal interference (TI) stimulation of the hippocampus can modulate hippocampal resting-state FC traces induced by a preceding hippocampally-dependent task. METHODS: We collected resting-state functional magnetic resonance imaging (rsfMRI) in twenty healthy participants before and after the performance of an associative memory task. Theta-band TI stimulation of the medial and anterior hippocampus, and sham stimulation were delivered during post-task resting state. We used permutation tests to assess differences in pairwise mutual information functional connectivity (miFC) between pre-task rsfMRI vs post-task sham. In edges with significantly different pre-vs post-task miFC, permutation tests assessed the effect of TI on post-task miFC. RESULTS: MiFC was significantly lower in several functional networks during post-task sham compared to pre-task baseline, including the hippocampal-connected and task-related Anterior Temporal (AT) and Posterior Medial (PM) networks. TI stimulation of the hippocampus during post-task resting state increased the miFC in the hippocampal AT and PM networks as well as other functional networks. CONCLUSIONS: Non-invasive TI stimulation of the hippocampus during the resting state acutely modulated FC traces related to preceding hippocampal-dependent memory tasks.