Study Offers New Insight into What Causes Learning Impairment in Schizophrenia

Study Offers New Insight into What Causes Learning Impairment in Schizophrenia

Posted: October 16, 2014

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People with schizophrenia tend to have cognitive impairments related to thinking and learning; these symptoms of the illness have a great impact on social functioning. One finding that seems to be consistent across research studies and teams is that there is a deficit in “reward learning,” which has to do with repeating behaviors that are positively reinforced (also called reinforcement learning). This lack of integration of reward/reinforcement can make it hard for people with schizophrenia to attach value to things—and may be what leads to the profound apathy that makes it hard for them to study, work or have social relationships.

Reward learning involves a combination of learning systems in the brain, including the basal ganglia region, associated with motivation, and also the prefrontal cortex region, linked to cognition and what is known as working memory (working memory enables the holding of multiple pieces of information in the mind for a limited amount of time, where they can be accessed and used to determine behavior.) Thus, it is unclear which specific system is responsible for the learning impairments in schizophrenia.

In a new study published October 8th in The Journal of Neuroscience, two-time NARSAD Young Investigator Grantee Jim Gold, Ph.D., of University of Maryland, Baltimore, and researchers at Brown University in Providence, Rhode Island, teamed up to disentangle the different processes involved in such learning in people with schizophrenia. Using a new behavioral test developed by the researchers at Brown University, combined with computer modeling, the researchers found that the trouble people with schizophrenia had in learning the reward associations stemmed from a diminished working memory that enables fast, but capacity-limited learning. The patients could not hold as many elements in working memory as the control subjects. Their basic reinforcement learning (slow, cumulative learning), on the other hand, was normal.

The results suggest that the working memory system contributes strongly to learning impairments in schizophrenia and also highlight the brain area responsible for the dysfunction, which is the prefrontal cortex. The researchers suggest that the loss of motivation in schizophrenia may stem in part from a malfunctioning prefrontal cortex rather than the basal ganglia, the region responsible for reinforcement learning.

“We've tended to say that motivation is about reinforcement, separate from the cognitive functions,” said 2013 NARSAD Distinguished Investigator Grantee Deanna Barch, Ph.D., of Washington University of St. Louis, Missouri, who was not involved in the study. “But this study shows we really need to think about motivation and cognition in a more integrated fashion.”

The researchers do not go so far as to say that all problems with reinforcement learning in schizophrenia come from impaired working memory. “It’s possible the task we used put a premium on the role of working memory,” Dr. Gold told the Schizophrenia Research Forum. “But the experiment provides a proof of principle that working memory problems likely do contribute to reinforcement learning problems.”

Read the abstract for this research paper.

Read more about this research from the Schizophrenia Research Forum.