The enduring memory problems that people with schizophrenia experience may be related to differences in how their brains process information, new research has found.
The Public Library of Science published the report by Vanderbilt University researchers Junghee Lee, Bradley S. Folley, John Gore and Sohee Park in the online journal PLOS One March 12.
“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,” 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 a fundamental difference in the way healthy people 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 picture emerged for schizophrenic patients.
“When healthy people are correct, there is an increased activation of the right frontal cortex. When they forget, there is no such increase. Their brain activation pattern is tightly coupled with their memory performance. Not so with schizophrenic patients,” Park said.
“Schizophrenic patients may encode and remember incorrect information. The brain activation pattern during such error trials indicate that indeed they were remembering something, albeit incorrect,” she continued. “Such coupling of storing incorrect information and feeling confident of one's response may be one way to think about how delusions get initiated,” Park said.
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,” 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 experiment, the subjects 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 told 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.