The researchers used the analytical technique of functional magnetic resonance imaging (fMRI) to show that a brain region called the intraparietal sulcus (IPS) is activated when both four-year-olds and adults perceive numerical quantities. They said their findings represent the beginning of a promising new research pathway to explore how the brain wires itself during development to acquire mathematical skills.
"Lots of previous behavioral studies have shown that pre-school children can do basic math tasks before they ever get any formal math training in school," said Jessica Cantlon, lead author of the study. "They can tell you that a bag of fifteen grapes has more things in it than a bag of five apples, even if they don't know how to verbally count very well. So, it seems like a basic set of math skills are laid down very early in development. And we were interested in whether these early math skills are related to the sophisticated math skills of adults in the brain," she said.
The experiment involved showing both children and adults a rapid display of objects, for example, 32 circles over and over. And when the subjects became accustomed to seeing 32 circles, a display containing 64 circles would appear. The fMRI scans would reveal the brain region activated by this change in number. To ensure that the brain region was not reacting to shape or some other aspect of the stimuli, the researchers would also change the objects to another form, for example a triangle.
"This study is the first study to use fMRI to study the neural basis of higher-order cognition in children this young," said Cantlon. "Our study suggests that the human brain is prepared for basic mathematics at an early age, and that the same neural circuits that perform basic math at an early age continue to process mathematical information over the whole course of development, into adulthood."
Also, in behavioral studies, the researchers found that the same children could not verbally count to 64, even though they were capable of discriminating such large numbers when presented in a nonsymbolic way. "We were showing them changes in number and changes in shape that allowed us to find specifically the brain regions involved in numerical perception that weren't connected to the numerical symbols that adults use in math. We clearly found that the IPS responded to number but not to shape in both children and adults."
Future studies, said the researchers will examine older children, to determine whether there are any detectable age-related differences in numerical processing that might give clues to development of numerical ability. Ultimately, the researchers hope to perform studies in which they follow development of numerical skills in the same children as they grow into adults.
Citation: Cantlon JF, Brannon EM, Carter EJ, Pelphrey KA (2006) Functional imaging of numerical processing in adults and 4-y-old children. PLoS Biol 4(5): e125. DOI: 10.1371/journal.pbio.0040125
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