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Why neurobiology of cognition in birds?

Traditionally, studies of complex cognition have focused on humans and our close relatives. However, recent studies reveal that also birds are cognitively well developed and show complex behaviours comparable to many mammalian species. In mammals, the layered structure of the cortex is considered crucial for complex cognition. Like in mammals, birds’ pallium, the cortex homolog, contains very high densities of neurons (neuronal densities in the primate pallium are matched by those of domestic chicken and surpassed by those of songbirds and parrots). However, instead of a laminar organisation, birds’ cortex developed a nuclear organisation. The absence of cortical layers in birds, together with the similarity in cognitive abilities of mammals and birds, challenges the fundamental question of neuroscience: how does brain structure contribute to its functions? We approach this question by using birds as animal models and investigating a selection of brain areas that process similar functions in birds and mammals despite their structural differences.

Structural and functional investigations of the avian hippocampal formation

Birds possess a hippocampal area that, in contrast to its mammalian homolog, lacks a layered structure and whose anatomical subdivisions are still highly debated. By using experimental setups equivalent to those used for rodents (e.g. 'dry version of the Morris water maze' and orientation in geometrical enclosure) in combination with neurobiological methods (e.g. single unit recording and histochemical detection of neuronal activity markers) we question how far theories developed for mammalian hippocampus can also be applied to the avian hippocampal formation.

Dry Morris Water Maze                    HF-c-Fost  
'dry version of the Morris water maze'             IEG-expression in the hippocampus             

Neurobiology of social cognition in birds

Birds are highly social animals, making them good models to study social behaviours. In all vertebrates the control of social behaviour is mediated by the so called 'social behaviour network', a set of interconnected areas rich in sex steroid receptors. Although the basic organisation of this network is similar in all vertebrates, the anatomical structure of these brain regions shows fundamental differences. We aim to investigate how areas of the 'social behaviour network' are interacting with each other, not only in social behaviours, but also in their contribution to learning and memory functions, producing the complex behaviours that we can observe in birds.

Conspecific              Septum    
A living conspecific vs. stuffed chicks                   IEG-expression in septum              

Visual processing in the avian brain

In humans visual information is transmitted by about 1 million fibers within each optic nerve, which is only 40% of the number of fibers within each optic nerve of domestic chicks.  Indeed, birds are probably the most visually advanced class of vertebrates. However, while the homologies between the visual pathways of birds and mammals are well understood, the functional equivalences between the later visual processing stations in the birds pallium and the mammalian visual cortexes are still unclear. This is particularly relevant for the study
of comparative cognition since precisely those later processing stations carry out more sophisticated computations of the visual information, which are involved also in higher cognitive functions. We study these visual properties in birds by combining behavioral, neuroanatomical and neurophysiological techniques.

Orientation Neurons        Retinotopic Maps
Direction selective neurons and retinotopic maps within the visual wulst in zebra finches