BIRDS are famously good navigators. Some migrate thousands of kilometres, flying day and night, even when the stars are obscured. And for decades, scientists have known that one navigational skill they employ is an ability to detect variations in the earth’s magnetic field.
How this magnetic sense works, however, has been frustratingly difficult to figure out.
Now, two researchers at Baylor College of Medicine, Le-Qing Wu and David Dickman, have solved a central part of that puzzle, identifying cells in a pigeon’s brain that record detailed information on the earth’s magnetic field, a kind of biological compass.
”It’s a stunning piece of work,” David Keays of the Institute of Molecular Pathology in Vienna wrote in an email. ”Wu and Dickman have found cells in the pigeon brain that are tuned to specific directions of the magnetic field.” Their report appeared online in Science Express.
Navigating by magnetism has several steps. Birds have to have a way to detect a magnetic field, and some part of the brain has to register that information; it seems likely that another part of the brain then compares the incoming information to a stored map.
The Baylor researchers have offered a solution to the middle step. They identified a group of cells in the brain stem of pigeons that record both the direction and the strength of the magnetic field. And they have good, but not conclusive, evidence to suggest that the information these cells are recording is coming from the bird’s inner ear.
They did not work on the third step, but Dickman said a good candidate for the location of that map was the hippocampus, the brain region involved in memory of locations in birds and humans.
The Baylor researchers did a kind of step-by-step tracking of what areas in pigeons’ brains were responding to variations in an artificial magnetic field that they created. By looking at specific neurons in the brain stem, the researchers found the bird’s orientation determined which neurons were active.
New York Times
