Berlin | Contrary to the previous belief, the human brain makes use of regions in both its hemispheres for processing numbers, scientists using high-performance MRI scans have found.
Our brain is known to work with division of labour. While words and language are mainly processed in the left hemisphere, the right hemisphere is responsible for numerical reasoning.
According to previous findings, this division of labour originates from the fact that the first steps in the processing of letters and numbers are also located individually in the different hemispheres. However, this is not the case, at least not when it comes to the visual processing of numbers, researchers said. They found that the visual processing of numbers takes place in a so-called ‘visual number form area’ (NFA) – in fact in both hemispheres alike.
The scientists were the first to publish high resolution magnetic resonance recordings showing the activity in this region of the brain of healthy test persons. The area is normally difficult to get access to.
In the study, Mareike Grotheer and Gyula Kovacs from the Jena University, and Karl-Heinz Herrmann from the Jena University Hospital in Germany presented subjects with numbers, letters and pictures of everyday objects.
Meanwhile the participants’ brain activity was recorded using magnetic resonance imaging (MRI). Thus the researchers were able to clearly identify the region in which the visual processing of numbers takes place. The small area at the underside of the left and right temporal lobe reacted with increased activity at the presentation of numbers.
Letters and other images but also false numbers lead to a significantly lower brain activity in this area. This region has been a kind of blind spot in the human brain until now, Grotheer said.
This is because, hidden underneath the ear and the acoustic meatus, surrounded by bone and air, previous MRI scans showed a number of artifacts and thus obstructed detailed research.
For their study the scientists used a high-performance 3 tesla MRI scanner. They recorded three-dimensional images of the brain of the test subjects at an unusually high spatial resolution and hence with only very few artifacts. In addition these recordings were spatially smoothed whereby the remaining ‘white noise’ could be removed.
This approach will help other scientists to investigate a part of the brain that until now had been nearly inaccessible. In this region not only numbers are being processed but also faces and objects, Kovacs said.
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