Thanks to functional MRI exams, experts recently gained new insight into mechanisms behind the “loosening of associations” commonly observed in individuals diagnosed with schizophrenia.
Looseness of association is characterized by fragmented, sometimes erratic speech patterns due to disrupted thought processes in people with schizophrenia. These patients are thought to have altered semantic processing due to impaired connections between neurons. Until now, those disconnections had not been characterized through functional brain activity.
“It is now possible to quantitatively evaluate the semantic representations of individual words in the brain, thanks to fMRI showing brain activity and language processing techniques,” senior author of the study Hidehiko Takahashi, from the Department of Psychiatry and Behavioral Sciences at Tokyo Medical and Dental University, and colleagues explained.
Functional MRI offers clinicians insight into neural activity by acquiring a series of images while patients are thinking about or performing a task that prompts a neural response. In the case of this research, patients watched a colorless movie during the exam.
Researchers from Tokyo Medical and Dental University (TMDU) completed fMRI brain scans on 14 patients with schizophrenia and 17 healthy individuals. The connectivity structure of patients’ responses was compared using a graph theory-based network analysis.
Experts found that semantic networks in healthy individuals' brains had small-world properties similar to those of natural languages, suggesting organization and greater connectivity between the networks. This allows neurotypical individuals to communicate more efficiently.
The opposite was found in patients with schizophrenia—those patients displayed significantly reduced small-world properties and disorganized connectivity structures. These findings were also associated with patients’ psychological measures. This would explain why individuals with schizophrenia struggle with thought and language processes.
“The disintegration of the semantic network of schizophrenia patients suggests that the representations of concepts become relatively indistinct in their brains,” the experts explained. “The co-occurrence of intruding knowledge may cause confusion in the understanding of context, leading to the emergence of delusional beliefs.”
This is the first study of its kind to use neural responses of schizophrenia patients to evaluate their brain network structure. The authors are hopeful that their work will lead to a better management of the mental illness and to understanding of how these individuals perceive the world.
The study and images are available in Schizophrenia Bulletin.
In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She joined Innovate Healthcare in 2021 and has since put her unique expertise to use in her editorial role with Health Imaging.