If you have a map, you can know where you are without knowing which way you are facing. If you have a compass, you can know which way you're facing without knowing where you are. Animals from ants to mice to humans use both kinds of information to reorient themselves in familiar places, but how they determine this information from environmental cues is not well understood. In a new study in mice, researchers at the University of Pennsylvania (Penn) have shown that these systems work independently. A cue that unambiguously provided both types of information allowed the mice to determine their location, but not the direction they were facing. The study, published in the May 19, 2015 issue of PNAS, was conducted by graduate students Joshua Julian and Alexander Keinath, Assistant Professor Dr. Isabel Muzzio and Professor Dr. Russell Epstein, all of the Department of Psychology in Penn's School of Arts & Sciences. "When you're lost," Dr. Epstein said, "how do you reestablish your bearings? People have been studying this for more than 25 years, but they have not focused on the fact that place recognition, figuring out where you are, and heading retrieval, figuring out which way you're facing, could be two separate systems." The team's experiment was an updated version of one of the original studies of reorientation, conducted at Penn by psychologists Dr. Ken Cheng and Dr. Randy Gallistel in 1986, which showed that rats use the shape of a room, but not other kinds of informative features, to get their bearings. To show this, the researchers in the 1986 study used a small rectangular room that had cups in each corner in which food could be hidden. From the bird's-eye view of the researchers, the food was always hidden in the northwest corner.
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