Development of executive function

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Executive function (EF; i.e., psychological processes involved in the conscious control of thought and action) undergoes considerable development during childhood, and there is now evidence that the development of EF depends, in part, on a growing ability to represent increasingly complex sets of rules--children first acquire the ability to represent a single rule, then a pair of rules, and then a hierarchical system of rules that allows them to select among incompatible pairs of rules (Zelazo et al., 2003). Although it is clear that prefrontal cortex (PFC) plays an important role in EF, relatively little is known about how specific developmental changes in PFC are related to specific changes in children's EF. The current proposal describes a new line of research that aims to assess the neural correlates of EF development, focusing in particular on the role of PFC. It is hypothesized that the pattern of developmental changes in rule use reflects the different rates of development of specific regions within PFC--from orbitofrontal cortex (single rules for responding when stimulus-reward associations need to be reversed), to ventrolateral and dorsolateral PFC (sets of conditional rules), to rostrolateral PFC (higher-order rules for selecting among task sets). Primary behavioral measures will be versions of the dimensional change card sort (DCCS; Zelazo et al., 2003). Two main measures of neural function will be used, with overlapping assessments when possible: event-related functional Magnetic Resonance Imaging (fMRI) and dense-array (128-channel) EEG/ERP. EEG/ERP has millisecond temporal resolution and is ideal for capturing the time course of neural processing. The results of this research program have the potential to shed light on the functional significance of age-related changes in PFC, and they will also address the effect of experience on EF development during early childhood. In the long-term, the results will provide the foundation of a detailed, integrative account of EF that spans behavioral, cognitive/emotional, and neural levels of analysis. One application will be to develop interventions for children with disorders related to EF (e.g., ADHD, autism, CD, PKU).