A new study has demonstrated that smaller size does not mean lesser efficiency: the forebrain of songbirds and parrots contains twice as many neurons as the brains of comparable-sized mammals. The article is published in the journal PNAS.
The study of the brains of 28 different bird species led to unexpected conclusions: in their forebrain—the area responsible for learning—the number of nerve cells exceeds the comparable number in the brains of mammals of similar size. This explains why some birds successfully solve the same tasks as mammals while having brains that are twice as small: they use the space in their skulls more efficiently.
To count the neurons, scientists extracted the bird brains from the skulls and dissolved them, creating what the study leader Suzana Herculano-Houzel described as a “brain soup.” This method allowed for the estimation of the number of cells in a specific area of the brain.
The area studied by the Spanish researchers plays an important role in tool use, planning future actions, singing, and mimicking human speech. The identified neurons turned out to be quite small, with short axons, which facilitates their connection with other cells. In the future, the scientists intend to find out why the neurons in bird brains are so small: whether they were originally that way or shrank to reduce overall body mass and facilitate flight.
