Neurodevelopment of the visual system in typically developing children.

A central question in developmental psychology is how a child acquires knowledge about the surrounding world. Is it important for learning to know what an object represents, before a child knows how to deal with it? Or does a child learn because it is improving haptic skills to act upon an object, to follow its actions and predict how it behaves? Behavioral research investigating such questions distinguished the role of dorsal and ventral visual streams in learning to "know how" and "know what" about objects, but these studies did not unequivocally resolve how these functions mature. Recent functional, structural, and microstructural neuroimaging research has shed a novel light on the normal development of the human visual system, particularly during later stages of child development. This chapter reviews these neuroimaging studies and interrogates them on the question of whether dorsal and ventral visual streams mature at different rates. Structural gray matter properties within the ventral visual stream show prolonged development compared to the dorsal stream, whereas white matter connectivity within dorsal visual stream structures matures later. Functionally specialized areas in the ventral visual stream show increased size during development, whereas parietal dorsal stream areas show increasing activity associated with high-order visual perception. Such results emphasize the importance of neuroimaging techniques for research on visual cognitive development. They suggest that high-order visual functions mature late and that dorsal and ventral visual streams follow different neurodevelopmental trajectories.