Varied Use of Brain Areas May Explain Memory Difficulties in Schizophrenics

Junghee Lee, Bradley S. Folley, John Gore, and Sohee Park. "We found that schizophrenic patients use different areas of their brain than healthy individuals do for working memory, which is an active form of short-term memory,” Dr. Park said. "Both groups used their frontal cortex while remembering and forgetting. However, while healthy subjects groups used the right side of this brain area when asked to remember spatial locations, the schizophrenic patients used a wider network in both hemispheres. This suggests that while healthy people recruit a specialized and focused network of brain areas for specific memory functions, schizophrenic patients seem to rely on a more diffuse and wider network to achieve the same goal.”

The researchers also found an essential difference in the way healthy individuals and schizophrenic patients made errors. When healthy people forgot, they had no confidence in their response for that trial and the brain areas that were recruited during correct memory trials remained inactive. A more complex portrait emerged for schizophrenic patients.

Researchers have known since the early 1990s that working memory problems are a consistent symptom of schizophrenia. The researchers sought to better understand what is occurring in the brain that may be causing these problems.

"The right hemisphere is usually recruited during spatial information processing but if it is malfunctioning, as it may be in schizophrenia, the left hemisphere may also be recruited,” Dr. Park said. "Another possible explanation is that schizophrenic patients may have more difficulty with these tasks, and as a result recruit more brain areas to assist them.”

In the study, the participants were shown a point on a computer screen and told to concentrate upon it. Three identical black circles were then flashed on a gray background, each in a different location. After a short delay, the subjects were shown a probe and instructed to press one key if the probe matched one of the circles shown earlier and another if it did not. They then were told to press another key ranking on a scale from one to five their confidence in their answer about the probe.

The researchers captured images of brain activity during these tasks using functional magnetic resonance imaging (fMRI). They repeated the experiment to capture data using another tool, near infrared spectroscopy (NIRS). NIRS is a new and promising method to study schizophrenia, the researchers believe.

The researchers published their study in the journal PLoS One on March 12, 2008. "We felt that the fact that anybody can access scientific papers in this journal was a big plus,” Dr. Park noted. "One normally has to pay for access to journals. Most schizophrenic patients, including the individuals who participated in our study, simply do not have the money to do so. This article is available for free to anyone.”


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