In rats, neurons in and around the hippocampus— the region of the brain responsible for forming a map of the physical surroundings— only weakly respond to changes in altitude, according to a study published online yesterday (August 7) in Nature Neuroscience. Specifically, as the animals moved upwards along pegs on a climbing wall or up a spiral stair case, grid cells, which measure distance, only kept track of their horizontal movement, and did not appear to encode how high they were. Place cells, which denote location, did respond to changes in altitude, but only slightly.
“The implication is that our internal sense of space is actually rather flat—we are very sensitive to where we are in horizontal space but only vaguely aware of how high we are," Kate Jeffery, lead author from UCL Psychology and Language Sciences, said in a press release. “This finding is surprising and…raises the question—if our map of space is flat, then how do we navigate through complex environments so effectively?”