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

Different features of visual function mature along unique timescales throug h infancy and early childhood. It is not clear which functions continue to mature in school age children. Functions believed to be mediated by the Mag nocellular (M) and Parvocellular (P) pathways were compared in five- (n=25) , eight- (n=21) and eleven-year-old children (n=21) and young adult control s (n=20). Steady-state visual evoked potentials were recorded from occipita l electrodes in response to very low spatial frequency gratings, at a serie s of contrasts (M), and to high contrast gratings at a series of spatial fr equencies (P). No evidence was found to indicate M pathway development acro ss these age groups. However, the youngest children demonstrated elevated V EP 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 path way.