Stage-specific 5-Hz visual flicker dissociates temporal encoding and production in bisection and reproduction

This project investigates whether externally imposed theta-band rhythmic structure causally and stage-specifically modulates human interval timing, paralleling dissociable contributions of hippocampal and striatal theta observed in prior neuromodulation work. Building on evidence that hippocampal theta primarily shapes the encoding of interval representations, whereas striatal theta contributes to decision-stage comparison and production-related readout, we test whether rhythmic sensory input delivered at different task stages selectively biases temporal behavior. Participants perform temporal bisection and time reproduction tasks while exposed to visual luminance modulation presented at the display border. Stimulation is applied either during the encoding phase or the production phase. To isolate the role of rhythmicity per se, stimulation is either rhythmic at 5 Hz (theta) or arrhythmic with matched event rate and luminance energy but without periodic structure. This design allows us to dissociate effects of temporal regularity from nonspecific sensory load. Opposite to our prior results found using theta temperal interference stimulation, we predict that rhythmic sensory stimulation during encoding will lead to improvement in temporal precision in bisection (decreased Weber fraction), consistent with theta entrainment of striatal neurons in timing function. Further, the stimulation should lead to longer reproductions in the reproduction task, consistent with hippocampal-theta-linked functions in time encoding. In contrast, rhythmic stimulation during production is expected to exert influencing reproduced duration without altering bisection precision, consistent with a striatal contribution to production-stage readout.