The brain is home to a one-eyed giant

According to Greek mythology, Odysseus defeated the cyclops Polyphemus, the one-eyed giant. Yet neuroscience shows that the cyclops really exists, or to be more precise, the cyclopean eye. “For some time it has been accepted that we see the world as if we have a single eye, a cyclopean eye”, explains Martijn Barendregt, neuroscientist at Utrecht University. “But we are the first to pinpoint the area of the brain that is responsible for this.” The findings of Barendregt and his colleagues have now been published in the journal Current Biology.

Generally speaking, people have two eyes which are both able to see. However, many people may not realise that each of these eyes transmits a different image to the brain. In order to create a single image, the brain needs the cyclopean eye. Co-author Serge Dumoulin says: “It is a transformation process. First of all, the two images are transmitted to an area of the brain. From here they are sent to another part of the brain that combines the two images into one. It is this second area of the brain that sees the world through a cyclopean eye.”

Powerful scanner

The existence of this transformation of two images into one  has long been accepted. “But now we have seen where it happens”, say the neuroscientists at Utrecht University who carried out this research together with Bas Rokers of the University of Wisconsin-Madison. In order to observe the transformation in the brain, test subjects were scanned using the extremely powerful 7 Tesla MRI scanner in the UMCU. This scanner was previously used by Serge Dumoulin to show how the brain recognises and organises numerosity.   

3D

“What your brain does can be compared to a 3D film”, explains Dumoulin. If you watch a 3D film without special glasses, you see two somewhat blurry, overlapping images. Wearing the 3D glasses brings these two images together into a single coherent image. And that's how it works in our brain too. “The right and left eye each transmit a 2D image to a certain part of the brain. This sends the images on to the cyclopean eye, which merges them to form a single 3D image. So thanks to the cyclopean eye we experience only a single, sharp 3D image.” Just how the cyclopean eye represents this third dimension, or depth, in the brain is fuel for further research.

More information

Faculty of Social and Behavioural Sciences press information, +31 (0)30-253 4027, r.a.b.vanveen@uu.nl