Butti, Camilla
Organization of the cetacean frontal and insular cortices: cytoarchitecture,chemoarchitecture, and neuronal specializations [Tesi di dottorato]

The brain of cetaceans is very large in both absolute and relative size and possesses an extremely convoluted cortex. The understanding of how the brain of these mammals fully adapted to an aquatic life is organized is important to shed light on the processes that shaped the evolution of the mammalian brain in general, including humans. Three cortical regions, the anterior cingulate (ACC), anterior insular (AI), and frontopolar cortices (FPC) have been shown to be involved in high-level cognitive function in primates and thus, the understanding of their structural organization in cetaceans is particularly meaningful given the wide evidence of their cognitive abilities. Cytoarchitecture, chemoarchitecture based on the distribution of the calcium binding (CaBP) protein calretinin, glia/neuron ratio, and neuronal specializations were assessed in the ACC, AI, and FPC of a series of cetaceans representative of the main families such as the bottlenose dolphin (Tursiops truncatus, Odontoceti, Delphinidae), Risso’s dolphin (Grampus griseus, Odontoceti, Delphinidae), harbor porpoise (Phocoena phocoena, Odontoceti, Phocoenidae), killer whale, (Orcinus orca, Odontoceti, Delphinidae), beluga whale (Delphinapterus leucas, Odontoceti, Monodontidae), sperm whale (Physeter macrocephalus, Odontoceti, Physeteridae), pigmy sperm whale (Kogia simus, Odontoceti, Kogiidae), Amazon river dolphin (Inia geoffrensis, Odontoceti, Iniidae), minke whale (Balaenoptera acutorostrata, Mysticeti, Balaenopteridae), and humpback whale (Megaptera novaeangliae, Mysticeti, Balaenopteridae). Other species including the pigmy hippopotamus (Hexaprotodon liberiensis, Cetartiodactyla, Hippopotamidae), Florida manatee (Trichecus manatus latirostris, Sirenia, Trichechidae), Atlantic walrus (Odobenus rosmarus rosmarus, Carnivora, Odobenidae), African savannah elephant (Loxodonta africana, Proboscidea, Elephantidae), black rhinoceros (Diceros bicornis, Perissodactyla, Rhinocerotidae), rock hyrax (Procavia capensis, Hyracoidea, Procavidae), lowland streaked tenrec (Hemicentetes semispinosus, Afrosoricida, Tenrecidae), and black and rufous elephant shrew (Rhynchocyon petersi, Macroscelidea, Macroscelididae), were used for comparative purposes in different parts of this study. The results show that 1) Order-specific differences in the organization of the neocortex occur among cetaceans; 2) Cetaceans share structural features of the neocortex with the artiodactyls, both at a structural and neurochemical level; 3) The glia-neuron ratio of the cetacean neocortex corresponds to what is expected for their brain size; 4) The specific cortical regions investigated contain, in most of the available cetaceans species, a neuronal specialization observed with the same pattern of distribution only in great apes and humans, the Von Economo neurons. Overall these results are further evidence for an organization of the cetacean neocortex, which, although very different from that of primates, displays complexity, challenging the classical view of its homogeneous and simple structure. Specifically, the extended development of regions involved in high-level cognitive processes such as the ACC, AI, and FPC, their diverse cortical organization, and the presence of a specific neuronal specialization, all suggest that specific evolutionary selective pressures acted on these cortical regions and thus on their functions. Based on the evidence reported in the present thesis, the brain of cetaceans can be considered of a complexity comparable to that of primates, and an evolutionary alternative to the generation of complex behaviors.

In relazione con http://paduaresearch.cab.unipd.it/2112/
VET/01 - Anatomia degli animali domestici

Tesi di dottorato. | Lingua: | Paese: | BID: TD13052452