Afferent projections to the cingulate cortex in albino rats: a study with a retrograde labeling method using fluoro-gold.

We studied the neuronal populations that project their axons to the cingulate cortex in albino rats using the retrograde fluorescent dye of 4% Fluoro-Gold injected into the anterior, middle and posterior portions of the cingulate cortex. The result showed that the following ipsilateral structures are sending fibers to these three portions: the prefrontal cortex, frontoparietal motor cortex, indusium griseum, dorsal endopiriform nucleus, lateral part of medial mammillary nucleus, nuclei of diagonal band of Broca, anterior pretectum, anterior part of caudate-putamen, hippocampal formation, anteroventral, anteromedial, lateroposterior, ventroposterior and dorsomedial thalamic nuclei. The anterior portion of the cingulate cortex receives inputs from the following ipsi- and contralateral structures: the accessory olfactory bulbs, anterior olfactory nuclei, middle and posterior portions of the cingulate cortex. The middle cingulate cortex receives fibers only from the ipsilateral dorsal part of the lateral septal nucleus in addition from the ipsi- and contralateral anterior and posterior portions of the cingulate cortex. While the posterior portion of the cingulate cortex receives separate inputs from the following ipsilateral structures: anterodorsal thalamic nucleus, temporal cortex, entorhinal cortex, areas 17 and 18, as well as from the ipsi- and contralateral anterior and middle portions of the cingulate cortex. The present study shows that the cingulate cortex receives various kinds of inputs from the other parts of the brain which are involved in emotion, memory, vision and motion, and also suggests that there are differences in afferent projections among the anterior, middle and posterior portions of the cingulate cortex.