Abstract
Cognitive control abilities change rapidly in early childhood. We explored the neural basis of visual cognitive control in the context of the Simon task longitudinally at the ages of 2 and 4. fNIRS was used to measure neural activation across bilateral frontal, temporal, and parietal cortices. During the Simon task, children were instructed to press either the left or right button of a two-button controller in response to an image of a front-facing cat or dog. The image could either be presented on the center of the screen (neutral) or laterally at a location that was either congruent or incongruent with the response location. A significant RT Simon effect (faster RTs on congruent condition) was observed only at age 2. At age 4, an accuracy Simon effect (more accurate on congruent condition) was observed instead. Over development, children’s accuracy improved in all conditions, and RTs became significantly faster on both neutral and incongruent trials, but not on congruent trials. Importantly, we found significant neural activation in left inferior parietal (lIP) cortex during incongruent trials, indicating lIP’s involvement in spatial filtering. We also observed a decreased lIP activation from 2 to 4 years of age in a region adjacent to where we found the condition effect, suggesting that activation in lIP becomes more selective over development. This is the first study in which children as young as 2-years-old showed a significant Simon effect. We prose that the Simon task can be used as a measure of neurocognitive development as early as age 2. The present results showed that even early in development there is significant neural activation to filter task-irrelevant spatial information. Further, the brain regions engaged are refined over development: older children recruit a narrower range of cortex.