MRI-BASED MORPHOMETRIC TOPOGRAPHIC PARCELLATION OF HUMAN NEOCORTEX INTRICHOTILLOMANIA

The purpose of the present study was to test specific hypotheses regar ding volumetric changes of the neocortex between 10 female trichotillo mania (TTM) subjects and 10 female normal controls. A standard three-d imensional (3-D) brain coordinate system was imposed over each newly a cquired native magnetic resonance imaging (MRI) scan for positional no rmalization and 3-D shape/geometric localization analyses were based o n the midpoints of anterior and posterior commissures, and the longitu dinal fissure. The brain segmentation method, using well-characterized semiautomated intensity and differential contour algorithms by signal intensity-frequency histograms, was used blind to segment the princip al gray and white matter structures. The segmented neocortical ribbon was subdivided into 48 regions (i.e. parcellation units) per hemispher e via a new method of morphometric topographic parcellation. There wer e no significant volumetric changes of the precentral gyrus, postcentr al gyrus, supplementary motor cortex or opercular cortex in TTM patien ts compared with control subjects. A broader analysis as a hypothesis- generating post-hoc effort showed that TTM subjects exhibited signific antly reduced left inferior frontal gyrus Volume of 27% (t = 2.21, d.f . = 18, P = 0.04) and enlarged right cuneal cortex volume of 40% (t = -2.30, d.f. = 18, P = 0.03) compared to normal controls. This is the f irst report of a structural neocortex abnormality in TTM. Results are discussed in terms of the behavioral specialization of these two brain neocortical regions and the complex interractions between visual and sensorimotor cortices. The results also showed the feasibility of the MRI-based morphometric topographic parcellation for investigation of t he human neocortex in neuroscience research.