Memory-Skills Training May Benefit Schizophrenia Patients

Agrowing body of research on the intersection of schizophrenia and memory illuminates both the nature of the disease and practical issues for patients.

“Subtle memory deficits in schizophrenia can lead to difficulty in functioning independently in real life, even more than the severity of the hallucinations and delusions that affect patients,” said Deana Barch, Ph.D., an associate professor of psychology, radiology, and psychiatry at Washington University in St. Louis and coauthor of a new study on episodic memory and cortical activity. Study results are published in the July 1 Biological Psychiatry.

The researchers recruited 17 patients with schizophrenia and 26 healthy controls. They were shown anonymous faces and a series of printed words in the first phase of the study and then quizzed on their ability to recall or answer questions about what they had seen.

Their brains were scanned with a functional magnetic resonance imaging (fMRI) system while they completed these tasks. All but one of the patients in the schizophrenia group were taking medications.

“Past research has shown that [people with schizophrenia] have deficits in memory, but the question is whether these are permanent, or if some strategies might improve their memory,” said lead author Aaron Bonner-Jackson, a graduate student in psychology at Washington University, in an interview with Psychiatric News.

The researchers did not describe the study to the subjects as a memory test, but the questions asked and the way they were presented allowed them to test how well the subjects learned and recognized information.

“They were not explicitly memorizing each word, but the deep semantic processing they were doing helped them to recognize a good percentage of those words later on,” said Bonner-Jackson. “I believe that knowing they were going to be tested later would probably affect their strategy in some way, which in turn probably would have affected their brain activity and subsequent recognition of the words. However, it was not necessary for them to know about the later memory test in order to obtain consent, since the brief deception was minor and necessary for our experiment.”

The researchers asked two kinds of questions. “Deep” questions required the subjects to think about the semantic meaning of the words, that is, if they were abstract or concrete. “House” is concrete, while“ love” is abstract, for instance.

“The point is, you've asked them to think about the word,” said Barch. “If you think about what words mean, you remember them better later.”

“Shallow” processing meant simply asking about the arrangement of letters in the word: Did the first or last letter of the word come earlier in the alphabet?

Study subjects weren't specifically trained in techniques for remembering words or images or for answering test questions, but the structure of the study demanded certain strategies to process the information, said Bonner-Jackson.

“The advantage of using deep versus shallow processing is that patients don't have to generate a strategy for memory,” commented J. Daniel Ragland, Ph.D., an associate professor of neuropsychology in psychiatry at the University of Pennsylvania School of Medicine, in an interview.“ And it's gratifying to see research taking strategy into account during imaging.”

Subjects with schizophrenia in the Washington University study performed worse than controls on both the shallow (alphabetical judgments) and deep (abstract/concrete) encoding tasks. Members of both groups did better on shallow than deep tasks.

In the recognition phase of the trial, subjects with schizophrenia were less accurate than were control subjects, but the difference was not statistically significant.

Compared with shallow encoding, deep encoding of words resulted in significant memory performance benefits among the schizophrenia subjects. Those subjects “benefit from deep encoding, just like controls do,” said Bonner-Jackson. “They don't have a generalized memory deficit; they can do what controls do.”

The fMRI imaging delineated areas of the brain in both subject groups that showed more activity during deep than shallow encoding. Both groups showed effects in regions typically active during deep semantic encoding. However, schizophrenia subjects showed greater activity for deep versus shallow encoding in three other regions: the left inferior frontal, right inferior frontal, and left middle frontal. These regions were not usually engaged by control subjects.

Two hypotheses might explain the involvement of these added brain areas seen in the fMRI.

“If greater activity appeared in better-performing subjects, it may mean that these regions are compensating for some deficit,” said Bonner-Jackson. “Or, if the increased activity appeared in lower-performing subjects, it could simply represent wasted effort and indicate greater pathology.”

Seeking evidence for either of these two alternatives, the researchers compared high- and low-performing subgroups among the schizophrenia patients. The effect size for the deep versus shallow contrast was greater in the low-performing group. Thus, people with schizophrenia who perform worse on the encoding tasks use more (and bilateral) brain regions, while high performers require a smaller set of regions to complete the same tasks, a set more like those activated in control subjects.

The “pathological” explanation seems more likely, given the results of this study, said Bonner-Jackson. Schizophrenia is associated with a deficit in the use of effective strategies to influence memory performance, and those abnormalities are not fully overcome by use of those strategies, said the authors.

Nevertheless, the study outcome also suggests avenues for clinical improvement of patients, Bonner-Jackson said: “People with schizophrenia have more memory capability than we thought.”

Such insights derived from the current state of basic research might influence ways to improve their lives.

“Patients with schizophrenia in a new learning situation tend to take a rather passive approach to processing stimuli, not actively organizing information,” said Ragland, whose related research is now in press with the American Journal of Psychiatry. “With the shallow/deep paradigm you can compensate by giving them a strategy, but the real challenge is teaching patients to do it for themselves, without a person in a white coat standing at their shoulder.”

“It won't help to tell people with schizophrenia just to work harder or emphasize rote rehearsal of information,” said Barch. “Rather than practice the same inefficient methods, it would be better to help them understand how they're learning by stressing the meanings and relationships of the things they encounter.”

An abstract of “The Influence of Encoding Strategy on Episodic Memory and Cortical Activity in Schizophrenia” can be accessed at<www.elsevier.com/locate/biopsychiat> under the July 1 issue. ▪