Eyes on the Brain

A neurobiologist explores the amazing capacity of the brain to rewire itself at any age

Navigation: It's All In Your Head

How you navigate suggests how you recruit different brain regions.

Did you ever notice how people have different strategies for finding their way? Some must always follow one and the same path while others develop mental maps and can find new routes and short-cuts. I usually fall into the first group—a real creature of habit, and I've always envied those who just seem to know their way.

So, I was intrigued to read in the latest issue of the Journal of Neuroscience an article about brain imaging and navigational strategies. In this study, 128 adults were exposed to a virtual environment maze in which objects were placed in specific locations. After watching video tours of the maze, the participants were placed in the virtual environment and had to find their way to the targets. Although all the subjects were successful in finding the objects, they varied widely in the strategies they used. Some people followed the routes that they learned during the virtual tour, while others, by making mental maps of the maze, found short-cuts. Many individuals used a familiar route for some trials and a short-cut for others.

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A smaller group of twenty subjects had their brain scanned in an fMRI machine while they were given a tour of the virtual maze. Two areas of the brain that were particularly active during the tour were the caudate nucleus and hippocampus. The caudate may be involved in developing memories of familiar routes while the hippocampus may be involved in the formation of mental maps and thus the possibility of discovering short-cuts. All subjects activated both areas when observing the tour of the virtual maze but to different extents.

Right after the brain scans, the subjects were given the task of finding objects in the virtual environment. Strikingly, the balance between hippocampal and caudate activation seen during the brain imaging predicted the strategy that they used. Those who had a greater hippocampal-to-caudate activation ratio during the brain scan were more likely to develop short cuts as they moved around the maze. Those who had a smaller hippocampal-to-caudate ratio during the brain scan were more likely to follow familiar routes. Thus, all the subjects successfully found their way through the maze, but the strategies they used were different. This difference was reflected in the way different regions of the brain were activated when they first learned about the maze.

I blame my poor navigational sense in large part on my vision. Up until age 48, I was cross-eyed and focused on only what was close and center. I rarely took in the visual periphery, never made any mental maps of my environment, and was continually disoriented and lost. Once I undertook optometric vision therapy and learned to straighten my eyes and see in 3D, I was able to take in more of my surroundings. For the first time, I began to create mental maps of the landscape. My husband helped me with this by making me a compass hat, a hat that buzzes every time I turn north. The hat prompts me to think about the direction I am going and thus reminds me to create and fill in my mental maps. As I read the Journal of Neuroscience article, I wondered if my compass hat and my new navigation strategy are changing the way I recruit and exercise different parts of my brain.

 

Susan R. Barry, Ph.D., is a professor of neurobiology in the Department of Biological Sciences at Mount Holyoke College and the author of Fixing My Gaze (June, 2009).

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