Subcortical projections to the hippocampal formation in squirrel monkey (Saimira sciureus).

Subcortical afferents to the hippocampal formation in squirrel monkey were investigated using horseradish peroxidase as a retrograde marker. Labeled cells were found in the medial septal area, the diagonal band of Broca, anterior and laterodorsal thalamic nuclei, reuniens and periventricular thalamic nuclei, lateral hypothalamus, supramamillary nucleus, and the dorsal and superior central midbrain raphe nuclei. These results in a primate confirm previous findings in rats and cats with the exception of the noradrenergic cell groups, where the interpretation of retrograde label was hampered by high levels of endogenous pigment.