No distorted prediction error processing in depression? Pupillary responses to expected vs. unexpected emotional information in clinically depressed and healthy individuals

Depression has been associated with a reduced ability to update negative beliefs, possibly driven by difficulties integrating new positive information. Recent theoretical accounts propose that attenuated neural responses to unexpected positive information, i.e., positive prediction errors, may underlie this biased belief updating. We examined the revision of established negative vs. positive interpretations in response to novel negative vs. positive information and the associated pupillary responses in clinically depressed individuals (n = 41) and healthy controls (n = 43). Results confirmed a negative interpretation bias in the clinical subsample, but no deficits in updating negative interpretations in the face of positive information. Similarly, no blunted pupillary responses to unexpected positive outcomes were observed in individuals with depression. Exploratory analyses provided preliminary evidence that medicated participants were more likely to revise their interpretations after positive information than unmedicated participants. Additionally, there was a possible tendency toward an increased pupillary response to unexpected compared to expected positive information across both subsamples, while negative outcomes appeared to elicit stronger pupil dilations regardless of the level of surprise. We discuss the results in terms of a trade-off between using ecologically valid, disorder-relevant stimuli and the resulting complexity and susceptibility to confounding variables in psychophysiological measurements.