The role of the five senses in navigation
We tend to assume that visual data combined with our internal sense of motion are the primary means by which our brains interpret our environment, but we take for granted the extent of the synergy between all five of our senses.
Experimentation on rats has shown that other forms of sensory input besides vision play a much greater role in perceiving environments than previously believed. The rats were placed in a virtual environment devoid of smell or sound, leaving them with only their vision and body movements to guide them.
The data obtained from observing their behaviour was then compared to that of rats operating in a real-world environment, with all forms of sensory input available to them.
The study found that the rats in the scentless and soundless virtual environment experienced a 60% decrease in the number of cells active in their brain when compared to the rats in the real-world space. This demonstrates just how significant a role the other senses play in navigation.
Scientists have long theorised that special cells in our brain, known as “place cells”, are responsible for recording visual cues that enable our brains to map out our environments. Each place cell records a specific location, like the space outside your front door, and is activated whenever you pass through that location.
The results of these studies demonstrate that the place cells not only store visual cues, but that they also record the smells, sounds and feel of our environments. The brain cross-references all that data to create its personal version of Google Maps.
Divide and conquer
The hippocampus has been identified as the part of the brain primarily responsible for spatial awareness. But research has revealed that there are two different sections of the hippocampus that play a role in the navigation of an environment. One determines the size of the environment, while the other focuses on its complexity. Researchers at the University of Queensland have referred to this as a “divide and conquer” approach.
Their study involved the observation of 18 volunteers as they made their way through three virtual mazes that varied in size and complexity. Functional magnetic resonance imaging was then used to analyse the activity in the subjects’ brains as they were presented with static images from within each of the mazes.
The scans revealed that brain activity increased in the posterior of the hippocampus for the bigger mazes, while the more intricate mazes prompted an increase in activity for the anterior of the hippocampus.
Another study, conducted by the Institute of Behavioural Neuroscience at University College London, determined that the anterior of the hippocampus was more active when planning the straight-line route to a destination, while the posterior hippocampus became more active when calculating the length of a route.
The participants studied maps of Soho and were taken on a two-hour tour of the area, during which they had to memorise where 23 different bars, cafes and shops were located. Then a film crew was sent in to walk the area. The researchers observed the participants’ behaviour as they watched the film footage. The idea was to observe activity in the brain as they attempted to recall information.
Scans showed that activity increased in the posterior hippocampus whenever the participants had to think of which direction to turn, or when they made a detour. The subject’s brain was attempting to calculate the length of the route. But activity in the anterior increased once the film crew begun to pursue their chosen route.
This coincides with the results of research performed in 2000, where it was discovered that the posterior hippocampus of London taxi drivers who had memorised various routes was larger than average.
Older than the compass, more advanced than GPS
Such research can make significant contributions to environmental planning, by improving our understanding of the ways in which the human brain navigates its surroundings. It can also contribute to healthcare, hopefully leading to better understanding and treatment of disorders that affect spatial awareness, like Alzheimer’s.
Ultimately, research into spatial awareness shows that while digital technologies like GPS have contributed much to everyday life, we have yet to unlock the full capabilities of a much older and more advanced mapping technology, that which is contained within the human brain.
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