APOE and dementia: Bookheimer et al.50 compared healthy older persons whowere ApoE3 and ApoE4 carriers, showing that individuals carrying the ApoE4 allelealready showed differences in brain response on an fMRI memory task, despiteexhibiting normal performance on neuropsychological tests.50 However, to act in prevention, the targetpopulation should be younger, as signs of brain alterations in dementia occurearlier in life.