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Tessa Dekker, Samuel Schwarzkopf, Aisha McLean, Catherine Manning, John Greenwood, Marko Nardini, Martin Sereno; The development of population receptive field size in visual cortex during childhood. Journal of Vision 2016;16(12):206. doi: 10.1167/16.12.206.
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© 2017 Association for Research in Vision and Ophthalmology.
Whilst dramatic changes in visual ability occur during the first year of life, many aspects of vision continue to develop substantially during childhood, with some only maturing in the early teens. For example, visuospatial processing during motion averaging and crowding tasks still improves after age 6 years (Manning, Dakin, Tibber & Pellicano, 2014; Greenwood et al., 2012; our own unpublished replication of these findings). We explored how changes in visual skills might be linked to visuospatial selectivity in the developing cortex, by adapting recently developed MRI and population receptive field (pRF) mapping methods (Dumoulin & Wandell, 2008) for children. We fitted a pRF model to fMRI signals measured while 6- to 12-year-old children (N=38) viewed an expanding ring and rotating wedge traversing the visual field. In a preliminary analysis with a subset of 18 children, we estimated pRF size and location for each voxel. Location estimates were used to generate polar angle maps to identify retinotopic regions of interest (V1-V3) in visual cortex. We found that as in adults, pRF size increased as a function of eccentricity, and from V1-3. In addition, a bootstrapping analysis comparing younger children (6-8 years, N=7) to older children (9-12 years, N=11), revealed a general increase in pRF size with age in V1 and V2, and peripherally in V3 (p< 0.05, Bonferroni-corrected). This is unlikely to be explained by confounding head-movements or by eye-movements away from the central fixation task, as these would predict larger pRF sizes in younger children. Thus, changes in low-level functions of the visual cortex may contribute to improvements in visual ability in late childhood. This work demonstrates for the first time that pRF estimation methods can be used successfully with young children, paving the way for in-vivo investigation of visual cortex organization and processing resolution during normal and abnormal visual development.
Meeting abstract presented at VSS 2016
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