The neural signature of simple overlearned temporal expectationsresembles episodic retrieval

Temporal expectations are crucial for adaptive responding to predictable events. Most previous imaging studies have focused on the neural underpinnings of unexpectedness rather than expectedness, without considering that neural responses related to temporal expectations may be confounded by parallel learning processes. To identify the neural basis of overlearned expectancy with fMRI, we employed a multi-day detection paradigm with auditory cues preceding visual targets at likely and unlikely time points. After training left inferior parietal cortex was engaged in processing overlearned temporal expectations together with retrosplenial and prefrontal cortex. Remarkably, compared with untrained controls, we observed inverted brain responses as a function of stimulus likelihood and training status. Finally, the brain regions coding overlearned expectancy had previously been implicated in episodic retrieval and simulation (based on Neurosynth association tests), suggesting that frequently used temporal expectations may, over time, utilize episodic memory routines to simulate likely future events and thus guide behavior.