A new study may explain why people with schizophrenia have difficulty achieving real-world goals, such as making friends, completing their education, and finding a job.
The study, from researchers at the University of Sydney in Australia, found that people with schizophrenia struggle to turn goals into action because the parts of the brain governing desire and emotion are less active, failing to pass along goal-oriented messages to other regions of the brain that affect decision-making.
“The apparent lack of motivation in schizophrenic patients isn’t because they lack goals or don’t enjoy rewards and pleasure,” said Richard Morris, Ph.D., the study’s lead author. “They enjoy as many experiences as other people, including food, movies, and scenes of natural beauty.
“What appears to block them are specific brain deficits that prevent them from converting their desires and goals into choices and behavior.”
The researchers used a two-prong approach to reveal how and why schizophrenics fail to convert their preferences into choices.
The first included a series of experiments involving different snack foods.
Through these, the researchers found that people with schizophrenia had the same liking for snack foods as those without. And when the researchers reduced the value of one of the snacks, people in both groups preferred different snacks.
The researchers found, however, that those with schizophrenia had a lot of difficulty choosing their preferred snack when provided with a choice between their preferred snack and the devalued snack.
Next, researchers used functional magnetic resonance imaging (fMRI) to measure brain activity while those in the study performed learning tasks involving snack foods. This technique relies on the fact that cerebral blood flow and neuronal activity are coupled, the researchers said.
When an area of the brain is in use, blood flow to that region increases, indicating neural activity, the researchers explained. This neural activity can be presented graphically by color-coding the strength of activation across the brain or in specific brain regions.
The functional MRI results revealed that those with schizophrenia had normal neural activity in the prefrontal cortex, the part of the brain responsible for decision-making, but in the part of the brain responsible for controlling actions and choice — the caudate — there was far lower neural activity than in healthy subjects.
This lower activity was correlated with the difficulty that the schizophrenic subjects had in applying their food preferences to getting future snack foods, according to the researchers.
“Pathology in the caudate and associated brain regions may prevent schizophrenic subjects from properly evaluating their desires then transmitting that information to guide their behavior,” said Morris.
“This means that desires and goals are intact in people with schizophrenia, however they have difficulty choosing the right course of action to achieve those goals. This failure to integrate desire with action means people with schizophrenia are stuck in limbo, wanting a normal life but unable to take the necessary steps to achieve it.”
The study was published in Biological Psychiatry.
Source: University of Sydney