Neural tuning to numerosity relates to perceptual tuning in 3- to 6-year-old children.

Neural representations of approximate numerical value, or numerosity, have been observed in the intraparietal sulcus (IPS) in monkeys and humans, including children. Using functional magnetic resonance imaging (fMRI) we show that children as young as 3 to 4 years old exhibit neural tuning to cardinal numerosities in the IPS and that their neural responses are accounted for by a model of numerosity coding that has been used to explain neural responses in the adult IPS. We also found that the sensitivity of children's neural tuning to number in the right IPS was comparable to their numerical discrimination sensitivity observed behaviorally, outside of the scanner. Children's neural tuning curves in the right IPS were significantly sharper than in the left IPS, indicating that numerical representations are more precise and mature more rapidly in the right hemisphere than in the left. Further, we show that children's perceptual sensitivity to numerosity can be predicted by the development of their neural sensitivity to numerosity. This research provides novel evidence of developmental continuity in the neural code underlying numerical representation and demonstrates that children's neural sensitivity to numerosity is related to their cognitive development.

SIGNIFICANCE STATEMENT: This study shows that a model of neural tuning that predicts numerical coding in adults applies to children's neural representations of numerical values at 3 to 4 years of age. The results show that the adult model of neural coding not only accounts for neural response patterns in children, but also predicts children's perceptual sensitivity. These data provide the first robust evidence that there is developmental continuity in how the intraparietal sulcus (IPS) represents the values of numerosities. Moreover, the study goes beyond previous research by examining the relation between neural tuning and perceptual tuning in children.