Anhedonia and amotivation are key clinical symptoms observed in patients with schizophrenia (SCZ) and those with major depressive disorder (MDD). Specifically, deficits in range adaptive valuation or coding are thought to contribute to these symptoms in patients with SCZ.  

Dr. Raymond Chan and his team from the Institute of Psychology of the Chinese Academy of Sciences have identified dysfunctions in range adaptation across the spectrum of SCZ disorders, which include clinically diagnosed individuals as well as those with subclinical psychopathological features. Furthermore, they have linked impairments in range adaptation to the long-term presentation of anhedonia and amotivation in schizophrenia symptoms in schizophrenia patients at follow-up. However, it remains unclear whether patients with MDD show similar or distinct patterns of range adaptive valuation in comparison to those with SCZ. 

To explore this question, Dr. Raymond Chan and his collaborators conducted a study to examine the valuation of rewards and range adaptive coding in patients with SCZ and MDD. They evaluated reward processing by constructing and comparing representations of expected value (EV) and outcome value (OV) using the Effort-based Pleasure Experience Task. This task was administered to 56 SCZ patients, 46 MDD patients, and 56 healthy controls to measure EV and OV adaptation.

This study was published in Asian Journal of Psychiatry. 

According to the researchers, patients with SCZ and MDD exhibit modifications in range adaptation, though in differing manifestations. SCZ patients were prone to over-adaptation in their response to OV and showed reduced adaptation to EV, while MDD patients showed diminished OV adaptation with preserved EV adaptation. In addition, correlations between OV and EV adaptations and anhedonia and amotivation were observed in both clinical groups. 

In summary, the study reveals distinct patterns of range adaptive value representation between patients with SCZ and MDD. The association of range adaptation with anhedonia and amotivation symptoms in these groups suggests that these impaired range adaptations may serve as critical neural mechanisms and potential targets for intervention in both SCZ and MDD patients.