Keith R. Thulborn1, Saad Jamil1, Aiming Lu1, Ian C. Atkinson1
1Ctr Magnetic Resonance Research, University of Illinois, Chicago, IL, United States
Quantitative sodium MR imaging at 9.4 Tesla has been used to measure cell density in the brain of cognitively normal individuals (N=14) across the adult age range (20-65 years). Despite the known ongoing tissue loss with aging, the constant cell density suggests that this is a highly conserved structural parameter. The brain must shrink with age as cells are lost in order to preserve cell density and hence function. This may be related to the need to maintain the intra- and extra-cellular volumes to preserve the resting membrane potential at the same energy demand of the Na/K ion pumps.