Motivational deficits in schizophrenia: investigations from the perspective of effort-cost decision-making

Schizophrenia is a psychiatric disorder affecting nearly 1% of the population. Individuals experience hallucinations and delusions, but also exhibit a deficit in motivation, which is one of the most debilitating symptoms in daily life. This deficit can hinder them from maintaining employment or engaging in social activities with family and/or friends. This lack of motivation is part of what is known as the negative syndrome of schizophrenia. These symptoms are poorly understood, and there is currently no treatment available.

Tasks examining the cost-benefit trade-off between different levels of effort and rewards have been used to understand motivation deficit. In schizophrenia specifically, around twenty studies have utilized effort-cost decision-making tasks and examined their relationship with motivation deficit. We aggregated these studies to quantify the magnitude of the deficit of effort-cost decision-making tasks using a meta-analysis. We found that the magnitude of the deficit in schizophrenia was moderate and robust, and correlated with the level of negative symptoms. Meanwhile, we observed that the efforts required in these studies were always static, not allowing subjects the freedom to adapt. Therefore, we examined effort from a dynamic perspective, which better reflects the trade-offs we make in our daily lives where we are freer to allocate our efforts according to our choices. We reused an effort allocation task that had been used to model motivation mechanisms in healthy subjects but had never been used to study the motivation deficit. We found that effort allocation in schizophrenia patients was less guided by the difficulty of the efforts. They exerted the same amount of effort at each level of difficulty. However, this was not correlated with the level of negative symptoms. To complete our overview of effort perception in schizophrenia, we reused the principle of subjective judgment tasks, where subjects are asked to rate the subjective perception of effort items on a rating scale that determines how unpleasant an effort is to them. This allows direct access to the effort valuation process in schizophrenia. In a second step, we recorded subjects' eye fixations when choosing between two previously rated effort items. This allows us to verify that subjects are indeed making choices based on the ratings given to the efforts in the previous step. Eye fixation data provided valuable information on the perception of the value of each item in the choices, which is strongly influenced by visual attention in healthy subjects. Although the analyses of this third approach are still ongoing, we see that patients make choices less guided by the value they assigned to the efforts compared to control subjects. It appears that they rely more on their visual attention to select efforts. There is no correlation with negative symptoms.

In conclusion, we observe multiple deficits in effort-cost decision-making, but their association with negative symptoms is not direct. To fully understand these approaches and the results obtained, I first need to introduce what value-based decision-making, schizophrenia, and value-based decision-making in schizophrenia are.