Image Analysis. The individual MRI and PET images were reformatted into a common space (standard brain) and filtered with 10-mm Gaussian kernel as described ( 13 , 19 , 21 ). Significant activations were then determined with statistical parametric mapping statistics (spm99, Wellcome Foundation, London) ( 25 ), by using the contrasts AND-AIR, EST-AIR, and OO-AIR. Three types of analyses were performed.