FUZZY CLUSTERING OF GRADIENT-ECHO FUNCTIONAL MRI IN THE HUMAN VISUAL-CORTEX - PART I - REPRODUCIBILITY

Reproducibility of human functional MRI (fMRI) studies is essential fo r clinical and neuroresearch applications of this new human brain mapp ing method. Based on a recently presented study on reproducibility of gradient-echo fMRI in the human visual cortex (Moser et al. Magn Reson Imaging 1996; 14:567-579), comparing the performance of three differe nt threshold strategies for correlation analysis, we demonstrate that (a) fuzzy clustering is a robust, model-independent method to extract functional information in time and space; (b) intertrial reproducibili ty of cortical activation is significantly improved by the capability of fuzzy clustering to separate signal contributions from larger vesse ls, running perpendicular to the slice orientation, from activation ap parently close to the primary visual cortex; and (9) for repeated sing le subject studies, SDs of <20% for signal enhancement in approximatel y 80% of the studies and SDs of <30% for activated area size in approx imately 65% of the studies are obtained. This, however, depends also o n signal-to-noise ratio, (motion) artifacts, and subject cooperation.