Topographic organization of basal forebrain neurons projecting to the rat cerebral cortex

The topographic organization of basal forebrain neurons projecting to the rat cerebral cortex was investigated using the retrograde transport of horseradish peroxidase (HRP). HRP injections in cingulate and occipital cortices labeled neurons in the nucleus of the diagonal band of Broca. In contrast, injections in the frontal cortex labeled mostly neurons in the substantia innominata, and injections in the temporal and parietal cortices labeled neurons in the medial and ventral boundaries of the globus pallidus. These results suggest that the basal forebrain projection to the cerebral cortex is topographically organized.