Fmri based analysis of brain plasticity in face and arm transplantation and arm scapular replantation patients

The aim of this study was to examine cortical plasticity in transplant patients and to analyze cortical reorganization that occurs after the hand and face transplantation using functional magnetic resonance imaging. Full-face transplantation (3), bilateral hand transplantation (2), scapular left arm replantation (1) patients and healthy control (10) subjects were participated in the study. The volar surfaces of the index finger and thumb and the lower face perioral area were stimulated, and images were recorded in the 3T functional MRI system. Represented hand and face areas in the somatosensory cortex are different in size, shape, intensity and location due to the experience-dependent plasticity. For this reason, an adaptive feature extraction with an adaptive masking method have been introduced which determines the peak densities of the activation clusters within the region of interest, which constitute the global masks in the radii proportional to the relationships between these intensities, and determines the thresholds for the average number of activated voxels. Features such as overlapped voxel numbers and barycenter distances of the represented hand and face areas were extracted from this masked area. In addition, barycenters, mean intensity, peak intensity coordinates and peak intensities of the activation maps obtained by adaptive masking were tested by means of various classifiers to discuss the separability of represented hand and face areas.