Dopaminergic processes predict temporal distortions in event memory

Abstract

Our memories do not simply keep time -- they warp it, bending the past to fit the structure of our experiences. For example, people tend to remember items as occurring farther apart in time if they spanned a change in context, or event boundary, compared to the same context. While these distortions could sacrifice precise timing, they might also serve to divide and organize information into distinct memories. In the current study, we combined functional magnetic resonance imaging (fMRI; n = 32) with eye-tracking (n = 28) to test whether activation of the dopaminergic system, known to influence encoding and time perception, predicts time dilation between adjacent events in memory. Participants encoded item sequences while listening to tones that mostly repeated over time, forming a stable auditory context, but occasionally switched, creating an event boundary. We found that boundaries predicted greater retrospective estimates of time between item pairs. Critically, tone switches significantly activated the ventral tegmental area (VTA), a key midbrain dopaminergic region, and these responses predicted greater time dilation between item pairs that spanned those switches. Boundaries furthermore predicted a momentary increase in blinks. Activation of the VTA predicted blinking in general, consistent with the idea that blink behavior is a potential marker of dopaminergic activity. On a larger timescale, higher blink counts predicted greater time dilation in memory, but only for boundary-spanning item pairs. Together, these findings suggest that dopaminergic processes are sensitive to event structure and may drive temporal distortions that help to separate memories of distinct events.