Neural substrates of duration serial dependence: Putamen suppression of the prior duration trace.

Perceptual judgments are biased toward recent experience, a phenomenon called serial dependence. For orientation and motion, this carryover has a demonstrated locus in the early visual cortex; for time, the circuits that hold the previous duration are unknown. Using fMRI, we asked where the preceding duration is represented, and whether the same neural mechanism carries recent information about a non-temporal feature of the same stimulus. Participants viewed a moving random-dot display and reproduced either its duration or its direction, retro-cued as to which feature to report, thereby separating the memory trace from the demands of task switching. Duration reproduction was attracted toward the preceding duration, four times more strongly when the same task was repeated. Direction judgments exhibited a much smaller bias that reversed sign with the preceding task. The preceding duration was negatively associated with retro-cue-locked activity in the bilateral putamen, the region where this effect survived whole-brain correction. The estimate held after accounting for both current and preceding responses. Direction produced no comparable signal anywhere. Switching from the direction task to the time task recruited the inferior frontal junction and dorsolateral prefrontal cortex, neither of which carried a preceding-duration effect. The prior-duration signal, therefore, localized to the dorsal striatum, distinct from the frontoparietal regions in task reconfiguration. These findings argue against a unitary neural mechanism for serial dependence and suggest that recent-history biases are likely domain-specific: for perceived time, the critical trace resides in the striatum rather than in the visual cortex.