Posts Tagged ‘grid cells’

The Disoriented Ape

December 15, 2018

The title of this post is identical to the first part of a title by Emma Young in the Features section of the 15 Dec. 18 issue of the New Scientist. The second half of the title is “Why clever people can be terrible navigators.” Apart from technology, which does little, if anything, to develop an individual’s ability to navigate. It is likely that a heavy reliance on these devices could reduce or destroy any abilities we might have.

There are two main approaches we use to navigate. Route-based navigation involves remembering landmarks on a particular journey: turn left at the church and then right at the park, and so on. This works pretty well in familiar towns or on regular journey, but what do you do if you are forced to take another route?

Mental mapping involves creating, consciously or unconsciously, a mental map of the environment. This approach is sometimes considered superior because it is more flexible and allows one to take shortcuts when appropriate. But it is more cognitively demanding.

Mary Hegarty of the University of California at Santa Barbara’s (UCSB) Spatial Thinking Lab says that most of us use both strategies, the trick being to get the balance right. “Good navigators probably select the best strategy for the job automatically.

Hegarty and colleagues put 140 UCSB students in a virtual reality maze. The maze contained 12 objects, including a chair and a duck, placed at various junctions. After being taught a route through the maze, the volunteers were started off at one object and asked to navigate to another. Sometimes the learned route was the shortest path and at other times it was quicker to take a novel route. Women were more likely to follow learned routes and to wander. Men showed a greater preference for trying to work out shortcuts, which call for mental mapping. On average, males were faster and covered less ground in reaching their target.

Hugo Spiers of University College London conducted a massive study that surveyed people’s navigational abilities using a mobile-phone-based game called Sea Hero Quest. In an analysis of more than 500,000 people from 57 countries, the best performers were living in nations with greater gender equality and greater economic wealth, which is associated with higher levels of education, which improves abstract problem solving. The presence of four Nordic countries in the top 10 has led Spiers to speculate that there may have been selection for good navigational abilities in their Viking and seafaring past. It might also help to have a culture of participating sports requiring navigation, such as orienteering,

Half of the Nobel Prize in 2014 went to John O’Keefe at University College London for discovering place cells in the hippocampus of rats. Each of these cells fired in a specific location at the animal moved around its enclosure. So by remembering patterns of place cell activity, a rat could effectively map its environment. The other half of the prize went to May-Britt Moser and Edvard Moser at the Norwegian University of Science and Technology for their discover of grid cells. Located near the hippocampus, they fire in groups, each making a discrete hexagonal region of ground as an animal moves across it. It is though that, by essentially unfurling a grid map over a two-dimensional space as it goes, the rat gets precise information about the distance between objects within it, including itself.

Place cells and grid cells have been found in human brains, as have a variety of other neurons specialized for navigation. Head direction cells encode the orientation of your head, providing a reference point for grid and place cells. Border cells fire when you get close to a boundary, such as a wall. Spatial view cells become active when you look at a place, even if you don’t actually go there.