Direct projections from the reticular formation of the medulla oblongata to the anterior cingulate cortex in the mouse and the rat.

After injections of horseradish peroxidase into the anterior cingulate cortex of the mouse and the rat, labeled neurons were observed in different nuclei of the reticular formation of the rostral medulla oblongata: ventral part of the nucleus gigantocellularis, nucleus paragigantocellularis and nucleus lateralis reticularis. Other labeled neurons lay scattered outside the nuclear boundaries, often close to the ventral-most border of the medulla. The projection to the cingulate cortex is sparse, with rarely more than 3 cells per case, but constant. Injections into other cortical areas (visual, motor and somatosensory cortex) did not produce labeling in the medullary reticular formation.