MRI Shows Neural Disruptions in Schizophrenic Patients with Auditory Hallucinations
New Radiology research may further the understanding of pathophysiological correlates of auditory verbal hallucinations in schizophrenia
In patients with schizophrenia who experience auditory verbal hallucinations (AVH), functional MRI (fMRI) demonstrates symptom-specific disruptions in resting-state neural networks, according to a recent study in Radiology.
MRI can help to map functional connectivity in the brains of patients with multiple sclerosis (MS) and those with clinically isolated syndrome (CIS), which carries a high risk of progressing to MS.
These results may further the understanding of pathophysiological correlates of AVHs in schizophrenia, said study author Hong Yin, MD, professor and director in the Department of Radiology at Xijing Hospital in China.
Published online ahead of print, the study will appear in an upcoming issue of Radiology.
“In our study, we showed that resting-state network biomarkers might be an effective indicator of AVH vulnerability in schizophrenia and provide a novel strategy for diagnosis and therapy,” Dr. Yin said.
AVHs are considered one of the most prominent features in schizophrenia, affecting 60 percent to 90 percent of patients.
In their cross-sectional study, researchers used independent component analysis to compare resting-state networks in 17 patients with first-episode, untreated schizophrenia who experienced AVH to resting-state networks in 15 schizophrenia patients without AVH and 19 healthy control subjects.
Results showed symptom-specific abnormal disrupted co-activation within the auditory, default mode, executive, motor and frontoparietal networks, with pronounced findings in the auditory cortex, supramarginal gyrus, insula, putamen, dorsolateral prefrontal cortex, angular gyrus, precuneus and thalamus. Researchers also noted a positive correlation between the degree of co-activation within the motor network and the severity of the hallucinations.
“With independent component analysis and dual regression, our findings indicate mainly increased brain activity in regions that involve auditory processing, language production and monitoring, and sensory information filtering in AVHs in schizophrenia, creating a predisposition toward false perceptual inference,” according to Dr. Yin and colleagues.
Using functional imaging data, the research team created maps demonstrating network connectivity differences among the patients with schizophrenia who experienced AVH, patients with schizophrenia without AVH, and healthy controls.
“The thalamus is characterized by enhancing certain inputs but suppressing others in schizophrenia, showing impaired thalamic filtering of external speech from internal speech,” the researchers added.
“We found decreased thalamic volume in patients with schizophrenia with AVH, a higher level of left thalamic co-activation within the executive network, and a lower level within the motor network. More intriguingly, an electrophysiological study seems to link the disruption of thalamoauditory cortical projection and AVH.”
Identifying Schizophrenia Biomarkers in Resting-State Networks
There are two main categories of research on AVH with fMRI, Dr. Yin explained.
The first type, state study, is conducted during a hallucination and is used to directly measure brain alterations associated with symptom occurrence. The second type, trait study, is used to compare the neural features of patients with AVH to those without AVH, whether or not they experienced hallucinations during imaging.
“None of the patients in our study reported the presence of AVH during MRI,” Dr. Yin noted.
“We therefore defined the current research as a trait study.”
The co-activation level of resting-state networks helped to distinguish patients with schizophrenia who experienced AVH from those without AVH, the research team found.
“We observed that patients with AVH demonstrated significantly increased co-activation in the right auditory cortex,” the researchers noted. “Also, there is evidence of altered connectivity between the superior temporal gyrus — the auditory cortex — and language- and/or memory- related cerebral structures, including the inferior frontal gyrus and the hippocampus.”
Hyperactivity in the auditory cortex might be related to its interaction with the language and/or memory processing areas, the authors concluded.
Dr. Yin’s team also detected increased co-activation in the putamen within the executive network and insula within the auditory network.
“In general, the insula and putamen involve speech production. Lower volume and disconnectivity of the putamen have been found in patients with schizophrenia with AVH,” Dr. Yin said. “Our results suggest the putamen as a possible verbal hallucinogenic source for AVH, on the basis of evidence of the putamen involving speech initiation and execution.”
- Access the Radiology study, "Disturbed Brain Activity in Resting-State Networks of Patients with First-Episode Schizophrenia with Auditory Verbal Hallucinations: A Cross-sectional Functional MR Imaging Study" at http://pubs.rsna.org/doi/full/10.1148/radiol.2016160938