Hippocampal volume

Hippocampal volume measures the size of the brain region central to memory consolidation and spatial navigation. Atrophy rates vary by cohort and method: Jack et al. report roughly 1.55 percent per year in cognitively normal controls, accelerating to about 3.98 percent per year in Alzheimer's disease. MRI-derived volume serves as an early biomarker of cognitive aging. Aerobic exercise has been shown to preserve or even enlarge it (Erickson et al. 2011, PNAS), while separate lines of evidence link sleep quality and chronic stress to hippocampal structure.