Common Learning Circuit Found in Birds and Mammals

In a new scientific study, researchers have broken new ground in their understanding of how birds and mammals may be connected evolutionarily. The investigators managed to discover that a common learning mechanism is at work in both the bird and mammalian brain, and that the same pathways are used, to some extent, in both categories. Given the large anatomical differences that exist between the cortices of these animals, finding such similarities is an extremely rare occurrence. The new study was led by experts at the Massachusetts Institute of Technology (MIT), who worked closely with colleagues from the Hebrew University, e! Science News reports.

“Our results strongly suggest that the same brain circuits underlie learning in birds and mammals, despite the superficial differences of anatomy. This circuit must have evolved at least 300 million years ago, before birds and mammals diverged,” explains MIT McGovern Institute for Brain Research expert Jesse Goldberg. The scientist worked closely with colleague Michael Fee, also from the Institute. Details of the work will be published in the upcoming, May 26 issue of the esteemed scientific Journal of Neuroscience. A related investigation, also by Fee and Goldberg, appears in the latest issue of the respected Journal of Neurophysiology.

The target of the investigation was a region of the brain known as the basal ganglia. This cortical region play a crucial role in learning new skills, getting accustomed with new habitats, and other related things. When it malfunctions, it may promote the development of drug addiction, neurodegenerative conditions such as Parkinson's, as well as obsessive-compulsive disorders. A central role in Parkinson's is, for example, played by the striatum and the globus pallidus, which are two structures located within the basal ganglia. Researches hypothesized a long time ago that birds feature the same type of structures and neurons as mammals in this region, but this was not proven scientifically before.

The MIT / Hebrew University team discovered that different basal ganglia cell types in the bird brain intersected each other in “area X,” a tiny structure in the brain, about 1 millimeter wide. The team positioned electrodes precisely into the area X of zebra finches. As the birds were singing, two distinct classes of neurons caught the eye of researchers. They compared these nerve cells with others found in the globus pallidus of monkeys, as underlying the same pathway. The firing patterns are highly similar in both species. The only difference is that the bird brain fires a lot faster, at around 700 spikes per second.