Your Brain on Math

16 07 2013

By @maiaszApril 23, 2013

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 No one is born knowing their 1, 2, 3’s or  A, B, C’s. However, the brain clearly handles these  uniquely human but culturally varied types of knowledge differently. Many  people, for example, are far stronger in one area or another, showing a  propensity for verbal skills over numerical ones or vice versa.

So understanding how the brain codes these different systems could not only  aid children with language disabilities, for instance, or those who struggle  with processing numbers, but could also help to reveal more about how the brain  works to process new information and acquire knowledge.

In a new study, which was  published in the Journal of Neuroscience, researchers tested seven people  with epilepsy who had electrodes implanted in their  brains to determine the source of their seizures. Researchers have learned a great deal about the  brain with the help of such patients, including more about how the brain works  to produce speech and the effect of anesthesia on consciousness. The electrodes help inform doctors about the  source of electrical disturbances that contribute to the seizures; some of these patients may then be eligible for additional surgery to remove the damaged region. Because of the unusual circumstance of having electrodes in their brain that can track neural activity, these patients are often approached to volunteer for clinical  trials of brain function.

In the first experiment aimed at determining the brain’s “numeral area,”  participants looked at single digits, letters, foreign numeral symbols from  languages they didn’t know and at images of distorted numbers and letters that  were unreadable. They were asked to press keys on the computer indicating  whether or not they could read each symbol. In a second test, the volunteers saw  either numbers, the words depicting numerals (one instead of  1) or words that sounded similar to number words (won instead  of one), which they read aloud.

The researchers pinpointed a group of around 1 million to 2 million cells,  located in a region called the inferior temporal gyrus that extends into both  sides of the head near the ear canals. These cells responded much more strongly  when the participants processed actual numbers than number words, meaningless  symbols resembling the numbers or the numbers written in an unknown foreign  language.

“This is the first ever study to show the existence of a cluster of nerve  cells in the human brain that specializes in processing numerals,” Dr. Josef  Parvizi, associate professor of neurology at Stanford University and the lead  author of the study, said in a statement. “It’s a dramatic demonstration of our  brain circuitry’s capacity to change in response to education. No one is born  with the innate ability to recognize numerals.”

(MORE: The  Math Gender Gap: Nurture Trumps Nature)

Because the second experiment asked the participants to distinguish between  phonetically similar words for the numbers (too instead of  two) and the numerals, the researchers could determine that different  brain regions were activated by the idea of the number, not just the sound of  the word.

The authors say that the region of the brain that preferentially processes  numerals is close to the area that is responsible for interpreting language,  which makes sense since people often read words and numbers together. That could  explain why previous work showed that some types of brain damage, for example,  can interfere with reading letters but leave numeral reading unaffected, or can  cause verbal dyslexia but not numerical confusion.

Interestingly, however, the cells responding to numerals seem to be  physically close to those that process distorted numbers and to foreign number  symbols, suggesting they might share a common origin and could be specialized  versions of cells that generally process visual images of lines, angles and  curves. Additional research on this region of cells could inform how education  and learning tease out this subgroup of these cells to process numerals in  particular.

(MORE: Can’t  Do Math? How the Brain Makes Tradeoffs in Favoring Some Skills Over  Others)

The study may also explain why such regions have not appeared in imaging  studies of the brain that did not have the advantage of the implanted electrodes  to track physiological activity. Since the inferior temporal gyrus is so close  to the ear canals, functional MRI machines, which detect changes in oxygen use  and blood flow by nerve cells, may not be as sensitive to the activity of  neurons tucked away in that area.

However, say the researchers, combining different techniques should lead to  deeper understanding of the brain’s inner workings and start to reveal some of  its seemingly inscrutable mysteries.

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