ABSOLUTE NUMBER AND SIZE OF PIGMENTED LOCUS-COERULEUS NEURONS IN YOUNG AND AGED INDIVIDUALS

Significant loss of noradrenergic neurons of the locus coeruleus in ag ing and Alzheimer's disease has been reported. The interpretation of t hese analyses, however, is problematic because of the model- and assum ption-based nature of conventional sampling and estimation techniques. In the present study, unbiased stereological methods were used to est imate the total number and mean cell volume of pigmented neurons of th e locus coeruleus in the brains of young and aged nondemented persons. No side-to-side differences are seen, and there is no change in pigme nted cell number or size in the locus coeruleus of nondemented older p ersons as compared with that of young individuals. In light of previou s studies that show severe locus coeruleus cell loss in Alzheimer's di sease, these data support further critical investigations into the pos sible protective role of noradrenaline in normal cognitive functions a nd emphasize the importance of avoiding methodological bias in quantit ative neuroanatomical studies.