A further issue to consider when choosing between fMRI and O-15 is the oft repeated statement that, unlike PET, fMRI allows for meaningful inferential statistics to be performed on individual subject's data. In this fashion, one can examine both common activation and individual variations -- an advantage which could prove doubly useful in the context of experiments employing small sample sizes. A perhaps less commonly appreciated point that has been recently discussed in print by members of both the London group and the D'Esposito lab, is the legitimate statistical generalizability of fixed (between-group) versus random (repeated-measures) analyses -- fMRI can be used to perform random analyses. -- Alex _____________________________________________ Alexander J. Shackman Laboratory for Affective Neuroscience Department of Psychology University of Wisconsin - Madison 1202 West Johnson Street Madison, Wisconsin 53706 PH: 608.262.4443 FAX: 608.265.2875 EMAIL: [log in to unmask] HTTP: psyphz.psych.wisc.edu %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%