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

Abstract

The present study describes the ipsilateral and contralateral cortico‐cortical and cortico‐thalamic connectivity of the parietal visual areas, posterior parietal caudal cortical area (PPc) and posterior parietal rostral cortical area (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 frontoparietal 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 frontoparietal network across mammals. The data generated will also contribute to a connectomics database, to further cross‐species analyses of connectomes and illuminate wiring principles of cortical connectivity across mammals.

Cortical and thalamic connectivity of temporal visual cortical areas 20a and 20b of the domestic ferret (Mustela putorius furo)

“…The posterior parietal cortex has been identified as an integral component of the visual dorsal stream, maintaining direct connections with the prefrontal cortex, as well as numerous direct and indirect connections with the occipital cortex. This has been illustrated in numerous animal studies (Baizer, Ungerleider, & Desimone, 1991;Kaas & Stepniewska, 2016;Remple, Reed, Stepniewska, Lyon, & Kaas, 2007) as well as in the ferret (Dell et al, 2018a(Dell et al, , 2018b. Similarly, the visual temporal cortex is integral to visual ventral stream information processing; thus, direct connections with the prefrontal cortex are anticipated (Cloutman, 2013;Goodale & Milner, 1992;Webster et al, 1994) The current study shows that areas 20a and 20b are well connected with PMLS (Figures 4-5, 7, and 9; Table 1), a feature also observed in the cat (Symonds & Rosenquist, 1979).…”

“…Note the dense connectivity with most regions of the visual thalamus, apart from that to the C lamina of the lateral geniculate nucleus and the MIN. Conventions and abbreviations as provided in the legend to Figure 6 and abbreviation list areas of the ferret are under a stronger influence of lateral geniculate input compared to the cat, potentially emphasizing differences in the extraction of visual information in the two species possibly related to life history and morphological differences (Dell, Innocenti, Hilgetag, & Manger, 2018a;Dell, Innocenti, Hilgetag, & Manger, 2018b).…”

Comparison between diffusion MRI tractography and histological tract-tracing of cortico-cortical structural connectivity in the ferret brain

“…Structural connectivity data from anatomical tract-tracing experiments in adult ferrets (of two years age) were obtained from (Dell et al, 2019a(Dell et al, , 2019b(Dell et al, , 2019c . The experiments examined the cortico-cortical and cortico-thalamic connectivity of areas 17, 18, 19 and 21 (occipital visual cortex), PPc and PPr (posterior parietal visual cortex), and 20a and 20b (temporal visual cortex) in adult ferrets by means of retrograde Biotinylated Dextran Amine tracer (BDA).…”

“…Thus, the injected brain regions were defined as the target regions and the brain regions with cell bodies that were labeled positive for BDA were defined as the source regions. The connections were then quantified by obtaining a fraction of labelled neuron (FLN) value; refer to (Dell et al, 2019a(Dell et al, , 2019b(Dell et al, , 2019c for a detailed explanation on the experimental procedures. Furthermore, for the purpose of this study, we considered only ipsilateral projections and adjusted the connectivity matrix and FLN values to exclude contralateral projections, in order to focus on the edge-complete subnetwork.…”

“…Furthermore, these mammals display complex behavior, are inexpensive to house and have a short gestation period as well as a limited life time, making them an attractive 'whole lifespan model' (Fox, 1998) . Recently established extensive tract-tracing connectivity data of the ferret (Dell, Innocenti, Hilgetag, & Manger, 2019a, 2019b, 2019c have made it possible to compare anatomical cortical connectivity with that reported by tractography methods. Thus, the present study aimed to use the ferret as an animal model to assess the performance of six diffusion tractography algorithms compared to histological tract-tracing data from the occipital, parietal and temporal cortices in the ferret.…”