Cortical and thalamic connectivity of posterior parietal visual cortical areas PPc and PPr of the domestic ferret (Mustela putorius furo).

The present study describes the ipsilateral and contralateral cortico-cortical and cortico-thalamic connectivity of the parietal visual areas PPc and PPr in the ferret using standard anatomical tract-tracing methods. The two divisions of posterior parietal cortex of the ferret are strongly interconnected, however area PPc shows stronger connectivity with the occipital and suprasylvian visual cortex, while area PPr shows stronger connectivity with the somatomotor cortex, reflecting the functional specificity of these two areas. This pattern of connectivity is mirrored in the contralateral callosal connections. In addition, PPc and PPr are connected with the visual and somatomotor nuclei of the dorsal thalamus. Numerous connectional similarities exist between the posterior parietal cortex of the ferret (PPc and PPr) and the cat (area 7 and 5), indicative of the homology of these areas within the Carnivora. These findings highlight the existence of a fronto-parietal network as a shared feature of the organization of parietal cortex across Euarchontoglires and Laurasiatherians, with the degree of expression varying in relation to the expansion and areal complexity of the posterior parietal cortex. This observation indicates that the ferret is a potentially valuable experimental model animal for understanding the evolution and function of the posterior parietal cortex and the fronto-parietal network across mammals. The data generated will also contribute to the Ferretome (www.ferretome.org) connectomics databank, to further cross-species analyses of connectomes and illuminate wiring principles of cortical connectivity across mammals.