Some people land in a foreign city and know their way around in one afternoon; others remain lost a week later. Now, Russell Epstein and colleagues from the University of Pennsylvania have found a neurological basis for that difference. Good and bad navigators process spatial information in distinct ways.
The researchers showed 12 volunteers a series of pictures of buildings and interior settings. At the same time, the researchers measured brain activity using functional magnetic resonance imaging (fMRI), which detects blood flow in the brain. Brain regions that are active during a task show proportionally more blood flow. However, as one becomes familiar with an object or image, activity decreases in a process called fMRI adaptation, suggesting that interpreting the image requires either fewer neurons or less activity in the same neurons. Thus, investigators can tell when a place is familiar to a subject, even if the subject’s point of view is new.
During the course of the experiment, the volunteers saw three types of images: identical places from the same point of view, identical places but from new perspectives, and novel places. Two brain regions involved in place recognition, the parahippocampal place area and the transverse occipital sulcus, were active during the task.
Initially, a volunteer’s recognition of a building or place was viewpoint-specific and only images from the same point of view induced fMRI adaptation. However, as subjects progressed through the trial and looked at more images, they developed a viewpoint-independent recognition of places and neural activity decreased even if a building was viewed from a new direction.
Significantly, people who scored well on a questionnaire that measures a person’s navigational skill showed more rapid fMRI adaptation than poor navigators when looking at view-point-independent images. The correlation was particularly strong in the parahippocampal place area.
“Good navigators have representational tuning, while bad navigators keep activating all of the cells,” as if the image is still unfamiliar to them, Epstein says.