Afferents from limbic system-related regions to the frontal cortex in the bush baby (Galago senegalensis)

Afferents from limbic system-related structures (aside from the cingulate and retrosplenial cortex) to medial and lateral regions of the bush baby's frontal cortex were investigated by means of the somatopetal transport of horseradish peroxidase. The frontopolar region received afferents from the subicular cortex, the lateral nucleus of the amygdala, from hypothalamic nuclei, the ventral tegmental area and other brain stem nuclei. Injections of horseradish peroxidase into other frontal regions usually resulted in labeled cells in brain stem nuclei and in the hypothalamus, but not in telencephalic regions; only the large injection into the posterior part of the frontal cortex was followed by labeled amygdaloid neurons. From these results it is concluded that a small number of limbic system-related telecephalic areas projects to the frontal cortex and that a somewhat larger number of diencephalic and brain stem nuclei reaches this part of the cortex.