Structures of bird brains and their relationship to cognitive capacity, metabolic costs and limitations to brain growth

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This project represents an attempt to establish a new view on the relationship between brain structure, brain metabolism, and cognition. At the same time, this study is a product of an intense collaboration between the labs of Suzana Herculano-Houzel (Rio de Janeiro; Brazil) and Onur Güntürkün (Bochum; Germany). The joint application that you just read is similar to the application to FAPERJ (Research Foundation of the State of Rio de Janeiro) that is submitted in parallel by Suzana Herculano-Houzel. With the exception of some differences in format, the only content-related differences of the Brazilian and the German proposal as presented here, concern the length of the description of the planned experiments. For the application to the DFG, the experiments planned in Brazil are provided in a shortened version only, while the studies planned for Bochum are described in detail. In short, we plan in Bochum to estimate the absolute and the relative size as well as the neuron numbers of the Nidopallium caudolaterale (NCL) in five different bird species. The NCL is the functional analogue to the prefrontal cortex and subserves executive functions in birds. The five bird species chosen are representatives of bird orders of which we have partly detailed knowledge on their cognitive abilities. In a second study, we plan to measure for the first time the brain metabolic rate in these five species. Since birds have exceptional cognitive skills and high neuronal densities, but very small brains, it is possible that their brains are characterized by extremely high metabolic neural demands per unit volume. Both findings of the present study could represent critical cornerstones for theories on the partly different paths of the evolution of brain and cognition in birds, relative to mammals.