Functional Activation in Diverse Regions of the Developing Brain of Human Infants

To understand the functional organization of the human cortex during the early postnatal period, we performed neuroimaging studies for visual perception in awake 3-month-old infants. Cortical hemodynamic responses to 2 different video images, moving mobile objects and black-and-white checkerboard pattern reversals, were observed using multichannel near-infrared spectroscopy (NIRS). Although a focal region of the occipital cortex was equally activated by both stimuli, the occipitotemporal region was activated only by the mobile objects. A possible explanation of the result is that the former and the latter regions are involved in the primary processing of visual stimuli and perception of objects with complex visual features, respectively. Furthermore, the prefrontal region was distinctly activated by the mobile objects. These results suggest that the early sensory region and the higher sensory/association and prefrontal regions are functionally differentiated by 3 months of age and that diverse regions of the cortex including the prefrontal region function during perception of visual events.