Researchers often study cognitive disorders to better understand normal development. But a new study in the July issue of Psychological Medicine has done just the opposite: Researchers simulated disorders with healthy college students and gained insight into the underpinnings of schizophrenia.
Specifically, John Kerns, PhD, a psychologist at the University of Missouri-Columbia, taxed the memory of 80 healthy college students until they told stories with the disorganized speech characteristic of people with schizophrenia.
Kerns showed students a series of images and asked them to make up 30-second stories about what they saw. At the same time, the students listened to a list of letters being read in earphones, and they occasionally had to recall whether the last letter uttered matched one they had heard two letters ago.
Kerns found that when the students' working memory--the brain's workbench--was burdened by remembering letters, their stories fell apart in much the same way as stories told by people with schizophrenia. For example, the study participants commonly mentioned characters without first introducing them--a feature of disorganized speech that researchers commonly observe in people with schizophrenia, says Kerns.
To further confound the memory, Kerns put a second burden on the brain. While viewing the images, students occasionally encountered a repeat. Kerns instructed the students to make up an entirely new tale when the old picture appeared. Unfortunately for the students (and fortunately for Kerns' research), seeing an old image brought back a flood of memories about the last story they told about it.
Students struggled to overcome these competing memories and, in doing so, stumbled into even more disorganized speech. When this difficulty was combined with the letter-remembrance task, the students' speech fell apart even more dramatically, closely mirroring schizophrenia's speech deficits.
By inducing abnormal behaviors in healthy brains, the study's results point toward a potential cause, rather than correlation, Kerns says.
"Everybody has some degree of unclarity in their speech," he says. "People with schizophrenia just have more of it."
These results further suggest that deficiencies in working memory and memory retrieval may form the backbone of schizophrenia-related speech problems. Kerns posits that behavioral and pharmacological strategies could ease the burdens that impair the memory processes of people with schizophrenia, such as stress.