Auditory delusions show link to voice-processing area

For the first time, researchers have combined functional and anatomic MR imaging to reveal abnormalities in both physiological states in a well-defined subgroup of schizophrenic patients with chronic auditory hallucinations. With the potential to visually pinpoint abnormalities, MRI could prove useful as a diagnostic and follow-up tool to evaluate treatment for people with the disorder, according to lead investigator Dr. Luis Marti-Bonmati, chief of MR at Dr. Peset University Hospital in Valencia, Spain.

Researchers imaged subjects as they listened to a recording of either neutral or emotionally charged words that are frequently heard by psychotic patients with auditory hallucinations. Brain function in the schizophrenic group was marked by an increased hemodynamic response in the temporal lobe. Structurally, gray matter volume in auditory processing regions of these patients was lower than in the controls (Radiology 2007;244:549-556).

Although the researchers expected a relationship between structural and functional aberrations, they were surprised to find so many coinciding areas that followed the same pattern: structural reduction of gray matter volume and functional overactivation. The coinciding areas included large clusters in the left and right middle temporal and left and right superior temporal gyri and smaller areas in the left posterior and right anterior cingular gyri, left inferior opercular frontal gyrus, and right middle occipital gyrus.

Marti-Bonmati suggests that overactivation and corresponding gray matter deficits in the limbic and frontal brain of schizophrenics reflect a dysfunctional emotional response to spoken words.

Schizophrenia is a complex syndrome with a strong genetic basis, yet the phenotypes are poorly understood, according to Fred W. Sabb, Ph.D., a research scientist with the Consortium for Neuropsychiatric Phenomics at the University of California, Los Angeles.

This study represents an important step in examining phenotypic indicators across several dimensions, he said.

"By combining fMRI and structural MRI results, these researchers have been able to localize specific structural deficits and abnormal neural signatures associated with behavior and examine how these are related to symptomatology at the core of the schizophrenia syndrome," Sabb said. "This multidimensional approach represents an exciting new area for neuroimaging, as we look to link phenotypes from genome to syndrome in the study of complex neuropsychiatric disorders."