The aging hippocampus: Cognitive, biochemical and structural findings

Aging is often accompanied by learning and memory problems, many of which resemble deficits associated with hippocampal damage. Studies of aging in nonhuman animals have demonstrated hippocampus-related memory decline, and point to a possible locus for impairments associated with normal and pathological aging in humans. Two well-characterized hippocampus-dependent tasks in nonhuman animal literature are the Morris water task (MWT) and the transverse patterning discrimination task (TPDT). We employed the virtual MWT and the TPDT to assess hippocampus-dependent cognition in humans. Magnetic resonance imaging and proton magnetic resonance spectroscopy were employed to measure hippocampal volume and neurochemistry respectively. Age-related deficits were observed in performance on both hippocampus-dependent tasks. This pattern of impairment was accompanied by decreased hippocampal NAA/Cre ratios and volume, both of which imply neuronal loss and/or decrease in neuronal density. Collectively, our results suggest that hippocampus undergoes structural and biochemical changes with normal aging and that these changes may represent an important component of age-related deterioration in hippocampus-dependent cognition.