Friday February 15 2008
CEA
3-month-old infants possess number sense
CEA
All humans, regardless of their culture and education, possess what we call number sense. It is through number sense that we can, for example, perceive the rough number of objects in a set within a fraction of a second. Over the last twenty years or so, methods employed in behavioural research have shown how 5 to 6-month-old infants possess number sense. A team from the cognitive neuroimaging laboratory at NeuroSpin(1) (joint CEA-Inserm Unit 562) have been the first to highlight brain regions activated in number processing in 3-month-old infants. The results of this study, which was led at Kremlin-Bicêtre Hospital in Paris, were published in the February 5 2008 release of PloS Biology.
(1) NeuroSpin is attached to the CEA's Institute of Biomedical Imaging, I²BM
(1) NeuroSpin is attached to the CEA's Institute of Biomedical Imaging, I²BM
The research team carrying out the study employed electroencephalography (EEG) to measure electrical activity in the brains of infants shown images representing object sets. Most of the images contained the same number of identical objects, but some showed different numbers or types of objects. The researchers noticed that infant brains reacted to these changes.
In adults, visual information is processed through two main processing pathways:
- the first, called the dorsal pathway, extracts object position and motion-related information. It functions through the parietal lobe regions situated at the top of the brain. It is this pathway that is activated for object number processing.
- the second, called the ventral pathway, extracts and retains information on the identity of objects perceived. This pathway functions through the laterally-positioned temporal lobe regions.
The EEG technique employed cannot directly highlight the cortical areas involved. However, the research team developed a method that uses the EEG data to reconstruct 3D images of the brain zones activated. This protocol enabled them to observe that even 3-month-old infants used separate brain regions to deal with changes in object and in number, and that the infant brain is already structurally organized along essentially ventral-dorsal lines.
These results also highlight how number sense develops through a continuity-based process: in the early months, number processing is directed towards the parietal regions. This means that young children can use this sense of quantities as a foundation, and then move on to understanding more sophisticated mathematical concepts such as arithmetic.
Observation of a change in object Observation of a change in number
Reference:
"Distinct Cerebral Pathways for Object identity and Number in Human Infants”, Izard V, Dehaene-Lambertz G, Dehaene S (2007). PLOS :Biology 6(2): e11 doi:10.1371/journal.pbio.0060011
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