Sixth Sense in Human Brain Mapped by Scientists

We may just have a sixth sense. No, it's not the ability to see dead people, but it does relate to the ability to work with numbers. Scientists have discovered that numerosity is associated with the part of the brain that is organized topographically, putting it on the same level as the other five primary sense of sight, hearing, touch smell and taste.

Scientists have suspected before that numerosity might be characterized by a topographical map. Until now, though, they haven't been able to find where it exists in the brain. Now scientists have sussed out the signals that reveal that the numerosity map is, in fact, real.

Numerosity is distinct from symbolic numbers. While we use symbolic numbers to represent numerosity and other aspects of magnitude, it's still only a representation. Instead, numerosity is derived from visual processing of image features.

In order to better understand what controls the brain's processing of numerosity, the researchers conducted a study on eight adults. They asked the participants to look at patterns of dots that varied in number over time, all the while analyzing the neural response properties in a numerosity-linked part of the brain used high-field fMRI. This allowed the scientists to scan the subjects for far fewer hours per sitting than with less powerful scanning technology.

The researchers then incorporated the data into a model, which aimed to measure neural response as directly and quantitatively as possible. This allowed them to model the human fMRI response properties that they observed. In the end, they saw a topographical layout of numerosity in the human brain. The small quantities of dots that the participants observed were encoded by neurons in one part of the brain, and the larger quantities, in another.

"We are very excited that association cortex can produce emergent topographic structures," said Benjamin Harvey, one o the researchers, in a news release. "We believe this will lead to a much more complete understanding of humans' unique numerical and mathematical skills."

The findings are published in the journal Science.