Subcortical connections of the prefrontal cortex in dogs: afferents to the medial cortex.

Afferent subcortical connections to the medial prefrontal cortex (PFC) in the dog were investigated using the horseradish peroxidase retrograde transport method. The dorsal and ventral regions of the medial PFC receive different projections both from the mediodorsal and the ventral thalamic nuclei. The dorsomedial PFC receives projection from a dorsolateral region of the "parvocellular" MD subdivision, while the ventromedial PFC - from the medial, "magnocellular" MD subdivision. The area precruciata medialis (XM) is involved in significant MD projection and should be included in the "prefrontal" not the "premotor" cortex. The ventral thalamic nuclei project mainly to the dorsomedial but not the ventromedial cortex. The distribution of this projection was correlated with antero-posterior cortical localization of injections. The main criterion for distinguishing "prefrontal" and "motor" cortex remains its projections either from MD or from VL nuclei. Only the ventromedial prefrontal cortex receives projection from anterior thalamic nuclei. The caudal region of the ventromedial prefrontal cortex seems to receive richer projection from "non-specific" thalamic nuclei as well as from the amygdaloid complex.