While it is clear that people with schizophrenia have more limited amounts of working memory, often referred to as short-term memory, scientists have never understood whether this is precisely what makes learning more difficult for the millions who suffer from this mental illness. Now, new research from Brown University pinpoints working memory as the key to learning difficulties in people with schizophrenia.
Working memory is what helps us keep bits of information in mind while we use it to complete a task. For instance, it is the memory we access whenever we read a cake recipe and then mix the correct amounts of flour, salt, baking powder, and sugar together, before we glance once again at the text of the recipe to see the next steps. It is the memory that allows us to remember the name of the man we just met and after a few minutes of conversation introduce him to a girlfriend. It is limited, like a piece of note pad paper, and easily disposable as well.
For the current study, the team of researchers assembled 49 participants with schizophrenia and a matched group of 36 participants without the condition for a specially designed learning task. In each round, participants see a set of images and then they must push any one of three buttons. Afterward, they’re told if they hit the right button for the image. Through trial and error, then, participants learn which picture calls for which button.
As designed, the task requires the use of working memory and the use of reinforcement learning; with perfect memory, a participant would never need to see an image more than three times to learn the right button to push whenever it appears. Next, the experimenters varied the number of images the volunteers saw, from two to six, in different rounds. As expected, the researchers discovered that for both participants with schizophrenia and those without, the larger the number of images, the more trials it took to learn to press the correct button consistently for each image and the longer it took to react to each stimulus.
However, people with schizophrenia generally performed worse on the task than the others. Then, using computational models, the researchers analyzed the numbers. What did they discover?
Differences in behavior between the groups could only be accounted for by the differences in working memory. "We really tend to think of learning as a unitary, single process, but really it is not," said Dr. Anne Collins, a Brown University postdoctoral researcher and study author. Instead, she explained it is a multiactor kind of behavior and clinicians who wish to help schizophrenics improve their learning abilities might want to target working memory rather than reinforcement learning.
Source: Collins A, Frank M, Waltz J, Gold J. Journal of Neuroscience. 2014.