A new study has revealed that the brain uses geometrical relationships from spatial environment to track the movements one makes to move from one place to another.
The findings from the University of Pennsylvania (US) have provided a neurological basis of how people used geometrical relationships to orient themselves and showed how the brain anchored this mental compass.
Russell Epstein, a professor of psychology in the University of Pennsylvania's School of Arts & Sciences, and Steven Marchette, a postdoctoral fellow in Epstein's lab, designed an experiment in which they had introduced participants to a virtual environment of four museums in a park, and had the participants memorise the location of the everyday objects on display in those museums.
They scanned their brains while asking them to recall the spatial relationships between those objects, such as whether the bicycle was to the left or the right of the cake. Using a technique called Functional magnetic resonance imaging (fMRI) they had measured the blood flow to different regions of their brain and focused on a region known as the 'retrosplenial complex .'
People who have had severe injuries to this region were able to recognise landmarks in their environments but were unable to recall how to get from one to another, suggesting that it played a specific role in the type of memory used in navigation and orientation.
After being allowed to freely roam around the virtual environment the participants were scanned with the fMRI scanner. The researchers explained that if the retrosplenial complex supported the geometrical system as the patterns had looked similar when the participants had imagined looking at objects that have the same 'geometric relationship' to the surrounding room, regardless of the "true" direction the participant was facing. For example, one who remembered objects on the back walls of two different museums had produced similar activation patterns, even though the back wall is north in one museum and east in the other.
The researchers said that they could reconstruct the location that the participant remembered based on those similarities and once they knew what they were looking for based on the first half of a participant's responses, they could estimate the location of a given view entirely from the fMRI data. They also added that the museums were geometrically identical and hence the 'retrosplenial cortex' used the same 'floor plan' for all of them."
Therefore through the fMRI data they could reconstruct a 'floor plan' of the museums from each person's brain. The team's research provided a more complete picture of what happened in the brain when people navigated from one place to another. This study also won 2014's Nobel Prize in Physiology or Medicine, and has added new dimensions to our understanding of spatial memory and how it helped us to build memories of events.
The study was published in Nature Neuroscience.
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