Researchers Map Sixth Sense Within the Brain

Researchers have discovered a sixth sense mapped out in the human brain: the ability to compare the amount of any given object, whether it be the number of people in a concert hall or jelly beans in a glass jar.

Called "numerosity," researchers have long suspected that this sense existed, but were unable to detect its presence within the brain. In particular, researchers were unable to identify a topographical map in which neurons related to numerosity assessment were laid out in such a way that those most closely related were able to interact over the shortest possible distance -- a phenomenon characteristic of the primary senses.

A new paper published in the journal Science changes all of that.

Led by Utrecht University's Benjamin Harvey, the study included eight participants, each of whom were asked to look at patterns of dots whose numbers changed over time. Meanwhile, the scientists analyzed the neural response properties in a part of the brain linked to numerosity using high-field functional magnetic resonance imaging,

With the resulting data, the team used population receptive field modelling, which, according to the press release detailing the study, "aims to measure neural response as directly and quantitatively as possible."

"This was the key to our success," Harvey said, as it allowed the scientists to, as the press release explained, "model the human fMRI response properties they observed following results of recordings from macaque neurons, in which numerosity experiments had been conducted more extensively."

Based on the results, the researchers were able to uncover a topographical layout of numerosity within the human brain, with neurons in one part of the brain encoding the small quantities of dots and another part of the brain the larger quantities.

So, what does this all mean? For starters, says Harvey, the study could help "lead to a much more complete understanding of humans' unique numerical and mathematical skills."