Bird brains

ScienceDaily has an item (here) comparing the networks in bird brains with those in mammals. The paper is: O. Güntürkün, M. Wild, T. Shimizu, V. Bingman, M. Shanahan; “Large-scale network organization in the avian forebrain: a connectivity matrix and theoretical analysis”; Frontiers in Computational Neuroscience, 2013



The researchers found both homologous similarities and convergent evolution similarities. These would likely underlie the cognitive capabilities of birds: innovative tool manufacture, referential gesturing, planning for future needs, mirror self-recognition, causal reasoning, long-term recollection, transitive inference, complex pattern recognition, optimal choice, and numerical discrimination. These feats are similar to many mammals but the mammal brain and the avian one have different architecture. This research shows many similarities.



Their conclusion:


The graph-theoretical analysis presented here reveals a connective core of five inter-connected hub nodes in the pigeon forebrain. In graph-theoretical terms, these regions are the most topologically central and most richly connected to the rest of the network, and are thus central to information flow in the avian brain. These findings are suggestive of the possibility that the same set of regions is central to avian cognition. Several researchers have hypothesized that intelligence evolved convergently in birds and primates. Our data are compatible with this idea, but hint at a somewhat more complex picture. For regions like the hippocampal APH, homology with their mammalian counterpart is likely, and the similarity of hippocampal network organization between birds and mammals is therefore likely due to shared evolutionary history. But several key structures in the pigeon connectome, such as NCL, AD, and AI, are functionally analogous but probably not homologous to corresponding mammalian structures. In these cases, shared network topology may be the outcome of convergent evolution. It is noteworthy that in both mammals and birds, the topologically central regions are also cognitively significant. It may therefore be reasonably hypothesized that during the evolution of taxa with demonstrably high cognitive abilities, similar selective pressures were at work resulting in similar network architectures.


Overall, our analysis suggests that, despite the absence of cortical layers, the avian brain conforms to the same organizational principles as the mammalian brain on a deeper, network-topological level. Future work will no doubt produce further refinements to the underlying connectome data. However, we anticipate that the central findings of the present paper will remain valid, namely the modular, small-world network topology of the avian brain and the presence within it of a connective core of hub nodes that includes hippocampal and prefrontal-like structures.




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