Figure 1.

Study design. In the initial phase of the neuroimaging study, annual resting-state PET scans were administered through follow-up year 8 of the study. Participants also performed a battery of cognitive tests each year. A group of participants developed initial symptoms of cognitive impairment on an average corresponding to year 11 (symptom onset, mean ± SD, 10.9 ± 3.7 years from baseline; n = 22). Changes in brain activity before the onset of impairment were assessed in CI (scan interval examined, mean ± SD, 7.0 ± 1.7 years) and compared with those who remained CN (scan interval examined, mean ± SD, 7.4 ± 1.5 years; n = 99) throughout the study.