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Abstract:
The brain maintains internal models to make predictions. When predictions are violated, the current model can either be updated or replaced by a new model. The latter is accompanied by pupil dilation responses (PDRs) related to locus coeruleus activity/norepinephrine release (LC-NE). We replicated and generalized Zhao et al. (Nature Communications, 2019) by investigating PDRs associated with transitions between regular and random patterns of tones in auditory sequences. We presented these sequences to participants who had been instructed to find silent gaps (to maintain attention). Transitions from regular to random patterns induced PDRs, suggesting that an internal model attuned to the regular pattern is reset. Transitions from one regular pattern to another regular pattern also induced PDRs with later pupil constriction, suggesting also a model reset. On the other hand, transitions from random patterns to regular patterns did not induce PDRs, suggesting a gradual update of model parameters because the random pattern does not allow for strong predictions. Overall, our results replicate Zhao et al. (2019) closely and suggest that PDRs, a biomarker of LC-NE activation, are indeed sensitive to model reset but not model update.
