The research article, Why Birds are Smart, by Onur Güntürkün, Roland Pusch, and Jonas Rose, explores the misconception of higher cognitive functioning being associated with a larger brain, particularly involving mammals. While animals such as birds do not have a large brain, avians have experienced a convergent evolution from mammals that allowed them to adapt similar neuronal structures that increase their cognition. The development of these structures in avian brains have allowed them to have cognitive abilities similar to mammals, such as planning for the future and using tools to assist them. The key neural features that allow avians to exhibit advanced cognitive functioning, despite their smaller brain, include an area similar to the prefrontal cortex in mammals called the nidopallium caudolaterale (NCL), dense dopaminergic innervation in association areas, a large amount of associate pallial neurons, and neurophysiological mechanisms which support a working memory. In addition to these specific key features of avian brains, they have more neurons in ratio to the size of their brain, or higher density, and they are more energy-efficient than mammalian neurons. In particular, these neurons are called pallial neurons, which innervate an area similar to the mammalian PFC, called the NCL. The dense innervation of dopaminergic neurons allows for avians to exhibit similar mammalian cognitive functions, as the PFC and NCL share similar roles in memory, reasoning, and cognition. Overall, despite the decrease in neuron numbers and brain size, avians have experienced convergent evolution that developed similar neuronal structures to mammals, allowing them to share similar cognitive roles, despite the popular assumption that larger brains are associated with more intelligence and cognitive skill.
In addition to specific neuronal mechanisms and structures in avian brains that exhibit similarities to mammalian brains, research led under Dr. Christina Herold and Dr. Martin Stacho has found that the overall organization of neuronal structure is similar as well. Previously, studies have found the structure of the brain in avians as disorganized and not as advanced as that of mammalian brains. However, with new technology called 3DPLI, or 3D Polarized Light Imaging, researchers were able to analyze the avian fiber structure, revealing specific features of the brain’s neural organization. They looked at one area of the avian brain in particular, called the dorsal ventricular ridge, or DVR for short, as it exhibits similar cognitive functioning to the mammalian neocortex. The results of the study showed that in specific sensory areas of the DVR, the neural fibers are organized radially and tangentially, or in simpler terms, horizontally and vertically. This precise organization of neural fibers is analogous to the organization of neural fibers in the neocortex of mammals. However, further analysis revealed that nonsensory areas of the DVR were organized in a different, more unorganized manner, as the fibers were arranged in patches, somewhat like a mosaic. But, in terms of the sensory components, this research study revealed the similarities in the precise and organized structure of the DVR in the avian brain to the mammalian neocortex, providing further context to why avian brains exhibit advanced cognitive abilities similar to mammals, despite the smaller size in brain and overall neuron count.
Both of these papers highlighted key features of the avian brain to explain why they also can perform higher-level cognitive functioning. These results debunk the common myth that a larger brain and neocortex are essential for advanced cognition and intelligence. Through specific neural features of the avian brain, such as denser dopaminergic neuron innervation, and analogous parts of the avian brain to mammals, such as the DVR to the neocortex, avians are able to perform advanced cognitive functions, which provides insight on further mechanisms on what makes organisms more intelligent, other than the outdated idea of larger brain size. Güntürkün, O., Pusch, R., & Rose, J. (2023). Why birds are smart. Trends in Cognitive Sciences, 28(3), 197–209. https://doi.org/10.1016/j.tics.2023.11.002 Stacho, M., Herold, C., Rook, N., Wagner, H., Axer, M., Amunts, K., & Güntürkün, O. (2020). A cortex-like canonical circuit in the avian forebrain. Science, 369(6511). https://doi.org/10.1126/science.abc5534
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