AGE-RELATED NEURONAL LOSS IN THE NUCLEUS CENTRALIS SUPERIOR OF THE RHESUS-MONKEY

The effect of age on the number of neurons in the nucleus centralis su perior (NCS) [6] was determined in 11 behaviorally tested rhesus monke ys or 7-32 years of age. There was a significant age-related decrease in both cell packing density and in the total number of neurons. This decrease in number of neurons appeared to effect two different populat ions of cell in the NCS, one of which corresponded in size to the sero tonergic cells in this nucleus and the other to a smaller-sized cell. Comparisons of the changes in the cell packing density with behavioral testing, showed significant correlations with the overall test perfor mance as well as with individual tests of memory function and of execu tive system functions. These findings suggest that neuronal loss in th e NCS may play a significant role in mediating cognitive changes seen in normal aging.