Negativity bias, which describes the tendency to interpret ambiguous stimuli or events as negative, is often observed in patients with depression and may prevent psychological well-being. Here, we used ambiguous facial stimuli, with negative (sad) and positive (happy) emotions simultaneously accessible, to examine neural activation during perceptual decision-making in healthy participants. The negativity bias was positively correlated with the activity of the bilateral pregenual anterior cingulate cortex (pgACC) when ambiguous faces were perceived as sad versus happy. Additionally, the strength of the functional connectivity between the bilateral pgACC and the right dorsal ACC (dACC)/right thalamus was positively correlated with hopelessness, one of the core characteristics of depression. Given the role of the pgACC as a major site of depressive affect and the roles of the dACC and thalamus in conflict monitoring and vigilance, respectively, our results reveal valid and important neuroanatomical correlates of the association between negativity bias and hopelessness in the healthy individuals.

Individual differences in positive memory recollection are of interest in mental health, as positive memories can help protect people against stress and depression. However, it is unclear how individual differences in positive memory recollection are reflected in brain activity in the resting state. Here, we investigate the resting-state functional connectivity (FC) associated with interindividual variations in positive memory by employing cluster-level inferences based on randomization/permutation region of interest (ROI)-to-ROI analyses. We identified a cluster of FCs that was positively associated with positive memory performance, including the frontal operculum, central operculum, parietal operculum, Heschl's gyrus, and planum temporale. The current results suggest that positive memory is innervated by frontotemporal network connectivity, which may have implications for future investigations of vulnerability to stress and depression.

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Perceptual changes in shape, size, or color are observed in patients with derealization symptoms; however, the underlying neural and molecular mechanisms are not well understood. The current study explored the relationship between neural activity associated with altered colorfulness perception assessed by fMRI and striatal dopamine D2 receptor availability measured by [11C]raclopride PET in healthy participants. Inside an fMRI scanner, participants performed the saturation adaptation task, where they rated how much vivid/faded visual objects looked like real/unreal ones using a visual analog scale. We found that participants experienced greater unreality when they perceived fadedness than vividness despite physically identical saturation. The combined fMRI and PET analyses revealed that the faded perception-related activities of the dorsolateral prefrontal and parietal cortex were positively correlated with striatal D2 receptor availability. This finding may help to understand the neuromolecular mechanisms of faded perception associated with feeling unreal in derealization symptoms.