The precise anatomical coordinates of a brain “hot spot,” was determined by scientists at the Stanford University School of Medicine. The specific area of the brain measures only about one-fifth of an inch across. It is preferentially activated when people view the ordinary numerals we learn early on in elementary school, like “6” or “38.”
Activity in this spot relative to neighboring sites drops off substantially when people are presented with numbers that are spelled out (“one” instead of “1”), homophones (“won” instead of “1”) or “false fonts,” in which a numeral or letter has been altered.
“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,” said Josef Parvizi, MD, PhD, associate professor of neurology and neurological sciences and director of Stanford’s Human Intracranial Cognitive Electrophysiology Program. “In this small nerve-cell population, we saw a much bigger response to numerals than to very similar-looking, similar-sounding and similar-meaning symbols.
“It’s a dramatic demonstration of our brain circuitry’s capacity to change in response to education,” he added. “No one is born with the innate ability to recognize numerals.”
The finding pries open the door to further discoveries delineating the flow of math-focused information processing in the brain. It also could have direct clinical ramifications for patients with dyslexia for numbers and with dyscalculia: the inability to process numerical information.
The cluster Parvizi’s group identified consists of perhaps 1 to 2 million nerve cells in the inferior temporal gyrus, a superficial region of the outer cortex on the brain. The inferior temporal gyrus is already generally known to be involved in the processing of visual information.
The new study, published April 17 in the Journal of Neuroscience, builds on an earlier one in which volunteers had been challenged with math questions. “We had accumulated lots of data from that study about what parts of the brain become active when a person is focusing on arithmetic problems, but we were mostly looking elsewhere and hadn’t paid much attention to this area within the inferior temporal gyrus,” said Parvizi, who is senior author of the study.