Stochastic tractography study of Inferior Frontal Gyrus anatomical connectivity in schizophrenia.
BACKGROUND
Abnormalities within language-related anatomical structures have been associated with clinical symptoms and with language and memory deficits in schizophrenia. Recent studies suggest disruptions in functional connectivity within the Inferior Frontal Gyrus (IFG) network in schizophrenia. However, due to technical challenges, anatomical connectivity abnormalities within this network and their involvement in clinical and cognitive deficits have not been studied.


METHODS
Diffusion and anatomical scans were obtained from 23 chronic schizophrenia patients and 23 matched controls. The IFG was automatically segmented, and its white matter connections extracted and measured with newly-developed stochastic tractography tools. Correlations between anatomical structures and measures of semantic processing were also performed.


RESULTS
White Matter connections between the IFG and posterior brain regions followed two distinct pathways: dorsal and ventral. Both demonstrated left lateralization, but ventral pathway abnormalities were only found in schizophrenia. IFG volumes also showed left lateralization and abnormalities in schizophrenia. Further, despite similar laterality and abnormality patterns, IFG volumes and white matter connectivity were not correlated with each other in either group. Interestingly, measures of semantic processing correlated with white matter connectivity in schizophrenia and with gray matter volumes in controls. Finally, hallucinations were best predicted by both gray matter and white matter measures together.


CONCLUSIONS
Our results suggest abnormalities within the ventral IFG network in schizophrenia, with white matter abnormalities better predicting semantic deficits. The lack of a statistical relationship between coexisting gray and white matter deficits might suggest their different origin and the necessity for a multimodal approach in future schizophrenia studies.
Department of Psychiatry, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215, USA. kubicki@bwh.harvard.edu
Marek
M
Kubicki
Jorge L
JL
Alvarado
Carl-Fredrik
CF
Westin
David F
DF
Tate
Douglas
D
Markant
Douglas P
DP
Terry
Thomas J
TJ
Whitford
Julien
J
De Siebenthal
Sylvain
S
Bouix
Robert W
RW
McCarley
Ron
R
Kikinis
Martha E
ME
Shenton
D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D056324:Diffusion Tensor Imaging; D005260:Female; D005625:Frontal Lobe / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008959:Models, Neurological; D015233:Models, Statistical; D009415:Nerve Net / Q000473:pathology*; D009434:Neural Pathways / Q000503:physiopathology*; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000473:pathology*; D012680:Sensitivity and Specificity; D013269:Stochastic Processes
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