Clinical, behavioural and neural validation of the PANSS amotivation factor.

Abstract

Negative symptoms in schizophrenia have been suggested to map onto two distinct factors - amotivation and diminished expression. Only recently, two-factor solutions for measuring negative symptoms have been proposed for the Positive and Negative Symptom Scale (PANSS), the most commonly used scale to assess the psychopathology of patients with schizophrenia. We aimed to validate the PANSS two-factor structure on a clinical, behavioural and neural level. For this multi-level validation, we reanalysed several datasets with patients for whom both the Brief Negative Symptom Assessment Scale (BNSS) and PANSS data were collected. We used a clinical dataset (n = 120) as well as behavioural data from an effort-based decision making task (n = 31) and functional neuroimaging data from a monetary incentive delay task (n = 41). Both tasks have previously been shown to be associated with BNSS amotivation. On the clinical level, the PANSS amotivation and diminished expression were highly correlated with their BNSS counterparts. On the behavioural level, we found that the PANSS amotivation factor but not the diminished expression factor specifically associated with willingness to invest effort to obtain a reward. On the neural level, PANSS amotivation was specifically related to reduced ventral striatal activation during reward anticipation. Our data confirm that the PANSS clearly allows distinguishing amotivation from diminished expression, as it relates selectively to specific aspects of behaviour and brain function. Our results will allow a re-analysis and sharing of existing datasets that used the PANSS to further substantiate the distinction between the two factors in neuroscientific studies and clinical trials.