Organization of cortical afferents to the frontal association cortex in dogs.

The source of cortical frontal association cortex (FAC) afferents and their terminal distribution in the dog's brain was determined by the HRP tracing method. It was shown that the sources of ipsilateral FAC afferents are limbic and paralimbic areas of allo- and mesocortex and parasensory areas of the neocortex. Most of these areas with the exception of the piriform olfactory cortex could be characterized as cortical association fields. The terminal distribution of FAC afferents gave evidence to distinguish dorsal and ventral FAC zones. The dorsal FAC zone which includes the premotor and dorsal prefrontal regions is supplied by afferents originating in the temporal, parietal, occipital, perirhinal and parahippocampal cortical areas. In contrast, the ventral FAC zone, involving the ventral part of the prefrontal cortex, receives characteristic projections from the subcallosal area and from the anterior parts of the piriform cortex. However, both FAC zones receive intensive projections from the cingular and insular cortices. The organization of FAC afferents in the dog was discussed in comparison with other species.