Birds do not need the latest in navigational technology when it comes to flying south for the winter; they come with their own built-in GPS system that uses the Earth’s magnetic field. But just how they detect the magnetic force is still unknown. Researchers at Baylor College of Medicine (BCM) are now closer to answering that question. In a study that was published online in Science on April 26, 2012, Drs. Le-Qing Wu, post-doctoral fellow, and J. David Dickman, professor of neuroscience, both at BCM, have shown how certain brain cells in pigeons encode the direction and intensity of the Earth’s magnetic field. "We know birds and many other animals can sense the magnetic force; behavioral studies show that birds fly along magnetic routes during seasonal changes," said Dr. Dickman, who conducted much of the research while at Washington University in St. Louis. "It is still unknown what exactly acts as a receptor within the bird; however, in our current study we are able to show how neurons in the pigeon’s brain encode magnetic field direction and intensity. This is how we believe birds know their position on the surface of the Earth." Dr. Dickman said certain areas of the brain are activated when a particular area of the inner ear, known as the lagena, is exposed to a magnetic field. Without it, several of these corresponding areas in the brain show no activity. Drs. Dickman and Wu used electrodes in one brain area, known as the vestibular nuclei, to record activity when the bird was exposed to a changing magnetic field. "The cells responded to the angle and intensity of the magnetic field. Some cells were more sensitive depending on what direction we aimed the magnetic field around the bird’s head," Dr. Dickman said.
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