Figure 1.

Summary of sleep physiology/stages, associations with memory, and changes related to hormonal milieu. Illustrations on the left depict EEG activity associated with each of the four stages of sleep (American Academy of Sleep Medicine (4)), and include definitions. Note that sleep staging is also conducted using concurrent EMG and EOG recordings. The right panel summarizes memory and hormone findings for rodents, nonhuman primates, and humans, denoted with blue symbols. AD = Alzheimer’s disease; E2 = 17β-estradiol; EEG = electroencephalography; EMG = electromyography; EOG = electrooculography; NREM N1-3= nonrapid eye movement stages 1-3; OVX = ovariectomized; P = progesterone; SWA = slow-wave activity; SWS = slow-wave sleep; REM= rapid eye movement.