Effort-based reward task, a behavioral measure to study negative symptoms in schizophrenia

Negative symptoms in schizophrenia, and specifically amotivation/apathy, have been correlated with impaired general functioning. Its neurobiological basis are thought to rely on an aberrant reward system. To study the association of reward deficits and negative symptoms, 25 schizophrenia patients and 35 controls underwent a new reward behavioral task. Briefly, patients had to choose a level of effort (1 to 3), each one corresponding to a progressively increasing number of required button presses and 3 different probabilities to win an economic reward. We compared the chosen effort between groups and correlated this output with the score of the Brief negative symptoms scale in the group of patients. Patients chose less effort than controls but without reaching significance level (mean patients effort: 2.49 vs controls: 2.76, P  = 0.064). A negative correlation was found between BNSS score and effort chosen for the maximum reward corrected by sex ( t : −0.021, P  = 0.045). When the group of patients was split according to negative symptoms score, patients with more negative symptoms (BNSSS score > 23) chose significantly less effort than patients with less negative symptoms and controls ( Fig. 1 ). Our reward task correlates well with negative symptoms. Thus, it could offer a behavioral measure of negative symptoms. It could be a good instrument to study the neurobiological basis of negative symptoms using functional techniques.