Figure 15. Brain activation maps obtained during memory-activation task in patients at genetic risk for AD (carriers of apolipoprotein [Apo] 
4 allele) compared with control subjects (apolipoprotein 3 carriers). Three-dimensional renditions of the brain surface are shown in gray, and colored areas indicate regions of significantly increased MR signal intensity during performance of memory task as compared with that during resting periods. Activation is seen in temporal and frontal regions in both groups; however, both the extent and intensity of activation are greater among the genetic risk group, which suggests compensatory brain function. (Adapted and reprinted, with permission, from reference 117.)