When assessing the value of a reward, people with schizophrenia have difficulty integrating information about the size of the reward and the probability of receiving it, according to a study in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. This inability is likely behind the motivational deficits associated with schizophrenia.
“In this study, the authors show that people with schizophrenia, whose motivational deficits lead to much of the social and occupational disability in the illness, perform poorly on reward-based decision making because they fail to compute the expected value of a specific action and instead rely on nonvalue-based information available in the task,” said journal editor Cameron Carter, MD.
Researchers from the Maryland Psychiatric Research Center, Baltimore, developed a learning task performed by 49 people with schizophrenia and 38 people without the disorder. The task required participants to consider the size of a reward as well as the probability of receiving it. Provided with two choices, participants were directed to select the choice with the highest reward value.
“Using the rewarded learning task, we showed that people with motivational deficits focus too much on how often a reward is presented (ie, probability), at the cost of learning about the size of the reward (ie, magnitude),” said study lead author Dennis Hernaus, PhD, now based at Maastricht University, The Netherlands.
“Our mathematical model helped determine that these ‘red integration’ deficits—that is, an inability to combine information about reward probability and magnitude—were linked to a decreased ability to precisely represent reward value, which is thought to involve a brain area called the orbitofrontal cortex.”
Among participants with schizophrenia, those with motivation deficits performed worse with easier choices—when the objective value between the options was larger. In other words, their ability to assess the reward value dropped when the demands on the orbitofrontal cortex to assess value rose.
In future studies, researchers plan to use neuroimaging to study deficits within the brain region and their association with motivation deficits in people with schizophrenia.