Neuromolecular basis of faded perception associated with unreality experience

Keita Yokokawa,Tetsuya Suhara,Kazunori Kawamura,Ayako Isato,Takehito Ito,Yoko Ikoma,Masanori Ichise,Makiko Yamada,Harumasa Takano,Hidehiko Takahashi,Hiroshi Ito,Yasuyuki Kimura,Keisuke Takahata,Ming-Rong Zhang

doi:10.1038/s41598-018-26382-9

Abstract

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.

Highlights

Perceptual changes in shape, size, or color are observed in patients with derealization symptoms; the underlying neural and molecular mechanisms are not well understood
In case of physically identical middle saturation stimuli (MS), the reality ratings of middle saturation stimuli preceded by high saturation stimuli (HSMS, subjective faded condition) and middle saturation stimuli preceded by low saturation stimuli (LSMS, subjective vivid condition) were 55.0 ± 11.0 and 65.2 ± 8.7, respectively
This revealed that the average activity of right and left V4 was significantly higher for the objective vivid condition (HS) than any other conditions (HS versus LS: p = 0.018; HS versus HSMS: p = 0.028; HS versus LSMS: p = 0.048, all p-values after Bonferroni corrected for multiple comparison, Fig. 2c)

Summary

Introduction

Perceptual changes in shape, size, or color are observed in patients with derealization symptoms; 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. 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. Application of saturation adaptation in fMRI may reveal the neural activities associated with subjective faded/vivid perception toward physically identical saturation objects. We set out to assess the subjective colorfulness and unreality experience of visual objects, and to examine the relationships between the neural representation of subjective colorfulness and unreality, measured by fMRI, and striatal D2 receptor availability, measured by [11C]raclopride PET, in healthy subjects

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Conclusion