In a remarkable experiment, researchers have transplanted an inborn behavior from one species to another. They swapped brain tissue between two bird species, causing young chickens to prefer the sounds made by mother quail over sounds made by mother chickens. "It's a real breakthrough in the study of perceptions, which are very elusive brain functions to study," says neurobiologist Thomas Park of the University of Illinois, Chicago.
Mother chickens and quail make characteristic calls to gather their chicks and keep them nearby, and the chicks innately perceive and favor the calls of adult females of their own species.
To determine the biological basis of this behavior, developmental biologist Evan Balaban of the City University of New York and colleagues took cells from regions of quail embryos destined to become brain tissue and transferred them to chicken embryos. After the chickens had hatched, the team tested their responses to vocalizations made by mother chickens and mother quail. Some chickens responded favorably to the chicken calls and some to the quail calls, the team reports in an upcoming issue of the Proceedings of the National Academy of Sciences.
The team then dissected the brains of the chicks see which regions had developed from transplanted cells, which stain differently than the chicks' own neurons. In chickens that responded to quail calls, the transplanted cells had developed into regions at the junction of the midbrain and forebrain, the researchers found. Transplanted cells produced other brain regions in those chicks that responded to chicken calls. This allowed the group to pinpoint the midbrain/forebrain regions as those responsible for the innate preference for a certain species' sound.
Other researchers applaud the transplant technique and are surprised that complex behaviors such as sound perception can be so localized in the brain that they can be transplanted. But the researchers don't yet know how these newfound regions connect to the birds' auditory pathways. "The ability to transplant is a very remarkable achievement, but the next stage is to figure out what circuits are involved," says bird-song researcher Masakazu Konishi of the California Institute of Technology in Pasadena.