Sobel Filter Segmentation of the Globus Pallidus in Schizophrenics
J. Alvarado, C. Davidson, M. Niethammer, R. McCarley, M. Kubicki, M. E. Shenton, J. Levitt
Mysell Harvard Research Day, Psychiatry Annual Meeting
2008
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Abstract
The basal ganglia (BG) are integrally involved in motor function, and
have recently been shown to form part of limbic and cognitive components in
frontal-striatal-thalamic (FST) circuits. Abnormalities in FST circuitry have
also been theorized to account for some of the symptoms and cognitive
disturbances observed in schizophrenia. Much of this circuitry converges on
the globus pallidus (GP) before projecting to the thalamus. More specifically,
the GP pars interna (GPi) represents a major ’¡Èoutput’¡É nucleus of the BG.
Pathology in this structure, therefore, could severely affect FST circuit
function and, in turn, account for motor, limbic, and cognitive deficits in
schizophrenia. Using structural MRI, we explored differences in the GP
between schizophrenics and normal controls.
Structural MR images were acquired on a 3T GE Echospeed system for
17 male, chronic schizophrenics and 19 normal controls group matched for age
and parental socioeconomic status. A Sobel filter, an edge-detection operator,
was applied to highlight the borders of the GP. The GP was manually
delineated by following the high-intensity borders marked by the Sobel filter.
Volume measurements, relative to intra-cranial contents, were calculated.
Volumetric measurements revealed a significant increase in schizophrenics in the left (p=0.013) and right (p=0.007) GP relative volumes (i.e., corrected for head size).
Our findings of increased GP relative volume in schizophrenics is
consistent with our lab’¡Çs previous findings, and with the notion that GP is
important in the pathophysiology of schizophrenia. These findings also suggest
the importance of further parcellation of the GP into its internal and external
segments to determine if there is a further localization to the enlargement and
to further clarify the role of the effect of medication.
Reference
Alvarado J, Davidson C, Niethammer M, McCarley R, Kubicki M, Shenton ME, Levitt J. Sobel filter segmentation of the globus pallidus in schizophrenics, 2008.
