Of Mice and Men (and Women)

Big navigation news out of University College London. In last month's Nature, a group of UCL researchers wrote that they'd found evidence of "grid cells" in the human brain. Scientists have known for a while that rodent brains have these "grid cells," whose accumulated firings map a triangular grid as the animal explores an open area.  They are just one of several specialized navigation neurons that have been found in rats, mice, and a few other animals.

But we don't know as much about our own navigational wiring. After all, opportunities to poke around living human brains are rare, although a few years ago, researchers at the University of Pennsylvania found a way. They asked a group of people with epilepsy who already had electrodes in their brains to identify the source of their seizures to play a taxi video game, providing the researchers with a neural play by play. 

In 2003, the Penn researchers found "place cells," neurons that fired only in response to seeing a given place (e.g. a bookstore), and cells that fired only when arriving at that bookstore, and still other cells that fired only when that bookstore was the virtual cabbie's destination. Two years ago, they discovered heading-specific "path cells" whose activity indicated whether the taxis were steering clockwise or counterclockwise around the virtual town square. But the search for "grid cells" by the Penn researchers and other labs had come up empty. Until now.