Three dimensional structure of the suprachiasmatic nuclei in the diurnal squirrel monkey (Saimiri sciureus).

In the squirrel monkey the suprachiasmatic nuclei (SCN) play a major role in the neural control of circadian physiology. Functional specificity within these nuclei has been suggested by the finding that subtotal lesions destroying only the posterior portion of the SCN altered the saliency of certain external stimuli as zeitgebers. Computer assisted histological analyses of the three dimensional (3-D) morphology of the SCN reveal a concomitant heterogeneity of structure between the rostral versus the caudal poles of these nuclei. The results are discussed in terms of a hypothesized specificity of function within the SCN.