Semantic network disconnection in formal thought disorder.
BACKGROUND
Structural and functional findings in schizophrenic patients with formal thought disorder (FTD) show abnormalities within left-side semantic areas. The present study investigate the network function of the involved brain regions as a function of FTD severity.


METHODS
We examined a group of 16 schizophrenia patients differing in FTD, but not in overall symptom severity, and 18 matched healthy controls. A passive word reading paradigm was applied during functional MRI (fMRI). A concatenated independent component analysis approach separated the fMRI signal into independent components, and spatial similarity was used to estimate the individual differences in spatial configuration of networks.


RESULTS
The semantic network was identified for both groups encompassing structures of the left inferior frontal gyrus, the left angular gyrus and the left middle temporal gyrus. The differences between the semantic networks of patients and controls increased with increasing severity of FTD. This difference was due to a decreasing contribution of the left inferior frontal gyrus (Brodmann area 45 and 47).


CONCLUSIONS
Severity of FTD was correlated with a disruption of the left semantic network in schizophrenic patients. We suggest that FTD is a consequence of a frontal-parietal/temporal disconnection due to a complex interaction between structural and functional abnormalities within the left semantic network.
University Hospital of Psychiatry, Bern, Switzerland. horn@puk.unibe.ch
Helge
H
Horn
Kay
K
Jann
Andrea
A
Federspiel
Sebastian
S
Walther
Roland
R
Wiest
Thomas
T
Müller
Werner
W
Strik
D000328:Adult; D001931:Brain Mapping; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000473:pathology / Q000503:physiopathology*; D003072:Cognition Disorders / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology; D059907:Functional Neuroimaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000473:pathology / Q000503:physiopathology; D010296:Parietal Lobe / Q000473:pathology / Q000503:physiopathology; D012559:Schizophrenia / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D012660:Semantics; D012720:Severity of Illness Index; D013702:Temporal Lobe / Q000473:pathology / Q000503:physiopathology