Localizing cortical sources of event-related potentials in infants' covert orienting.

This study used cortical source analysis to locate potential cortical sources of event-related potentials (ERPs) during covert orienting in infants aged 14 and 20 weeks. The infants were tested in a spatial cueing procedure. The reaction time to localize the target showed response facilitation for valid trials relative to invalid or neutral trials. High-density EEG (126 channels) was recorded during the task, and independent component analysis and equivalent current dipole analysis was used to estimate the cortical sources of the EEG during the task. There was a larger P1 ERP component on the valid trials than the other trials (P1 validity effect). The cortical source analysis suggested that this occurred due to activity in Brodmann's areas 18 and 19. A presaccadic ERP component occurred over the frontal scalp areas (-65 ms) and was larger to a target in a cued location than in uncued locations. A potential cortical source for this ERP component was the superior frontal gyrus on the inferior portion of the prefrontal cortex. Increases from 14 to 20 weeks in amplitude of the P1 validity effect and the presaccadic ERP could be modeled by an increase in activation in the corresponding cortical areas.