A VEP investigation of parallel visual pathway development in primary school age children.

Different features of visual function mature along unique timescales through infancy and early childhood. It is not clear which functions continue to mature in school age children. Functions believed to be mediated by the Magnocellular (M) and Parvocellular (P) pathways were compared in five- (n=25), eight- (n=21) and eleven-year-old children (n=21) and young adult controls (n=20). Steady-state visual evoked potentials were recorded from occipital electrodes in response to very low spatial frequency gratings, at a series of contrasts (M), and to high contrast gratings at a series of spatial frequencies (P). No evidence was found to indicate M pathway development across these age groups. However, the youngest children demonstrated elevated VEP thresholds to the high contrast gratings compared with either the adults or eleven-year-olds. This difference in threshold implies an immaturity of the high contrast, high spatial frequency stream, i.e. the putative P pathway.