Oct 17, 2014 06:12 AM EDT By Staff Reporter, UniversityHerald Reporter

Working memory makes learning more difficult among schizophrenic patients, according to a Brown University study.

Although it was known that working memory affects millions of people with schizophrenia, until now the cause and effect relationship had not been determined.

"We really tend to think of learning as a unitary, single process, but really it is not," said Anne Collins, a postdoctoral researcher and lead author of the study, in a statement. "We thought we could try to disentangle that here and see if the impairment was in both aspects, or only one of them."

For the study, the researchers subjected 49 participants with schizophrenia and a control group of 39 to a specially designed learning task. In each round, the participants were asked to push one of the three buttons when they saw an image in a set of three. They were subsequently told if they pressed the right button.

A participant with a perfect memory wouldn't require seeing an image over three times to learn the right button for an image to push when it appeared.

In some rounds, the researchers varied the number of images from two to six. The researchers found that both the groups took more time to learn to press the correct button, when they were shown a larger image set size. At the same time it took longer to react to each stimulus. Schizophrenic patients performed worse on the task than healthy controls.

"More broadly, it brings attention to the fact that we need to consider learning as a multiactor kind of behavior that can't be just summarized by a single system," Collins said. "It's important to design tasks that can separate them out so we can extract different sources of variance and correctly match them to different neural systems."

The finding is published in the Journal of Neuroscience.

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