Co-occurring positive and negative prediction error signals are independent of stimulus repetition effects

Both the absence of a predicted stimulus and the unexpected presentation of another stimulus result in increased activation in the areas processing the stimuli. These signals are termed negative and positive prediction errors, respectively. Here, we showed that both types of prediction errors can occur simultaneously and independently of stimulus repetition effects. Participants performed a reaction time task in a magnetic resonance scanner while being exposed to face and place stimuli with a distinct probabilistic distribution resulting in unexpected omissions and unexpected presentations of those stimuli. Participants' responses were significantly faster for expected as compared to neutral or unexpected trials, showing that they learned the statistical regularities inherent to the task. Moreover, the region of interest analysis of beta estimates extracted from the fusiform face area and the parahippocampal place area revealed co-occurring negative and positive prediction error signals. This was evidenced by increases in brain activation for unexpected omissions and unexpected presentations of visual stimuli when compared to expected stimuli. Our results also underlined that these effects occur independently of stimulus repetition effects. Altogether, these findings support a predictive coding model of cognition, highlighting the importance of considering the potential dual nature of expectation violations.