Abstract
It is commonly assumed that early visual areas (V1-V2, and also retina and LGN) develop first, followed by higher associative cortices (V3-V6-MT). However, there have been no direct measurements of the maturation of individual cortical areas in newborns by MR imaging methods to confirm this hypothesis. In adults, motion direction selectivity is mediated by an extensive network of areas (V1, V3, V6, LO, MT, VIPS, Pre-Cuneus, PIVC). Here we use fMRI to investigate if this neural network is functional in infancy. We measure BOLD responses to flow versus random motion stimuli in 10 cooperative 7-week-old infants, and the resting state activity in 5 of those infants during sleep. The results show that at 7 weeks of age the major circuits mediating the response to flow motion were operative and adult-like, with stronger response to coherent spiral flow motion than random speed-matched motion (Morrone et al 2000, Nature Neuroscience) in parietal-occipital area (presumed MT+), pre-cuneous, posterior parietal (V6) and an area corresponding anatomical to PVIC, which in adults receives visual-vestibular input (Cardin & Smith 2010). As in adults, V1 does not respond preferentially to coherent motion. Resting-state connectivity maps indicate strongly reduced connectivity between V1 and the parietal-occipital regions selective for flow motion (putative MT+), suggesting the existence of an alternative input that bypasses V1. The results revealed an unexpected maturation of the motion analysis circuit of the associative area, probably not mediated by striate cortex, and suggest that the limiting factor in the development of motion selective cortical response are the development of the subcortical input and of the cortical-cortical connections.
Meeting abstract presented at VSS 2014