Context-Dependent Modulation of Duration Encoding in the Supplementary Motor Area

Abstract

Duration judgments are calibrated by the statistics of recent temporal experience, but how this contextual influence is expressed across human timing-related brain regions remains unclear. We used functional MRI while 24 participants performed a visual temporal bisection task under two distributional contexts: one biased toward longer durations and one biased toward shorter durations. Behaviorally, distributional context shifted subjective duration judgments without changing in temporal precision, consistent with a prior-related bias. Neurally, duration-related BOLD responses varied across a priori timing regions as a function of context. The clearest region-specific evidence was stronger left-insula duration modulation in the short-biased context. SMA/pre-SMA contributed to the broader timing-network pattern, and its context-specific asymmetry was sensitive to the alignment of the duration regressor. Exploratory SMA-seeded connectivity analyses provided converging evidence that context also modulated duration-related coupling with timing- and attention-related regions. Together, these findings indicate that distributional context impacts the relative weighting of established timing-related regions during duration judgments, rather than recruiting anatomically separate timing systems.