Quantitative analysis of neuronal cells in specific brain areas of different avian orders: Comparison of avian species with high cognitive abilities to species with lower cognitive skills.

• Applicant: Dr. Felix Ströckens
• Subject Area: Cognitive, Systems and Behavioural Neurobiology ; Evolutionary Cell and Developmental Biology (Zoology) ; Human Cognitive and Systems Neuroscience ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: Funded in 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 260119458

It is believed that primate species possess the most advanced cognitive skills in the animal kingdom. However, avian species like some corvid and parrot species show cognitive abilities which seem to match the skills of non-human primates. This is reflected in their capability to use tools, perform causal reasoning and exhibit future planning as well as imagination. Although the cognitive abilities are highly similar between these avian species and non-human primates, their brain organization is vastly different. Therefore, it is feasible to assume that advanced cognitive abilities can be based on different neuronal architectures. This, however, raises the question of which factors have contributed towards the evolution of such specialized brains in both primates and certain avians, that only these species evince advanced cognitive skills. Absolute and relative brain size seem to be insufficient to explain the differences in cognitive skills within vertebrates. Evolutionary development of advanced cognitive functions has to depend on other factors. Such a possible factor has recently been identified in primates. Primate brains differ from other mammalian brains in their neuronal scaling rules allowing them to accumulate more neurons per brain volume than other mammalian species can. Preliminary data indicates that Passeriformes birds, which include corvids, share this scaling rule with primates. Therefore, comparable neuronal scaling rules could be the connecting factor between the advanced cognitive skills in primate and corvids. The aim of the presented project is to quantify the number of neurons in different forebrain areas of birds to investigate if such favorable scaling rules are present in avian species with advanced cognitive skills, and if these scaling rules are specific to certain brain areas. For this reason I plan to analyze cellular composition of brain areas which have been shown to be related to advanced cognitive functions in birds, such as the Nidopallium/Mesopallium in comparison to primarily motor and sensory areas. Cellular compositions will be investigated by using a recently developed method: the Isotropic fractionator technique. This method allows precise measurements of neuron numbers within a given area not affected by heterogeneity in cellular distribution. The analysis will be done in four corvid and three parrot species, as well as five other avian species which do not show extraordinary cognitive skills. I expect that brain structures associated with advanced cognitive abilities will show higher cell densities in corvid and parrot species in contrast to other birds. On the other hand, cellular densities of areas less related to cognition are expected to scale with motor/sensory characteristics of the given species. If this is the case, this study will provide the first insight into the neuronal prerequisites which allow the development of advanced cognitive abilities in two differently organized neuronal systems.

• DFG Programme: Research Fellowships
• International Connection: Brazil
• Host: Professorin Suzana Herculano-Houzel, Ph.D.