The emergence of the visual word form: Longitudinal evolution of category-specific ventral visual areas during reading acquisition

PLoS Biol. 2018 Mar 6;16(3):e2004103. doi: 10.1371/journal.pbio.2004103. eCollection 2018 Mar.

Abstract

How does education affect cortical organization? All literate adults possess a region specialized for letter strings, the visual word form area (VWFA), within the mosaic of ventral regions involved in processing other visual categories such as objects, places, faces, or body parts. Therefore, the acquisition of literacy may induce a reorientation of cortical maps towards letters at the expense of other categories such as faces. To test this cortical recycling hypothesis, we studied how the visual cortex of individual children changes during the first months of reading acquisition. Ten 6-year-old children were scanned longitudinally 6 or 7 times with functional magnetic resonance imaging (fMRI) before and throughout the first year of school. Subjects were exposed to a variety of pictures (words, numbers, tools, houses, faces, and bodies) while performing an unrelated target-detection task. Behavioral assessment indicated a sharp rise in grapheme-phoneme knowledge and reading speed in the first trimester of school. Concurrently, voxels specific to written words and digits emerged at the VWFA location. The responses to other categories remained largely stable, although right-hemispheric face-related activity increased in proportion to reading scores. Retrospective examination of the VWFA voxels prior to reading acquisition showed that reading encroaches on voxels that are initially weakly specialized for tools and close to but distinct from those responsive to faces. Remarkably, those voxels appear to keep their initial category selectivity while acquiring an additional and stronger responsivity to words. We propose a revised model of the neuronal recycling process in which new visual categories invade weakly specified cortex while leaving previously stabilized cortical responses unchanged.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Brain Mapping
  • Child
  • Humans
  • Language*
  • Learning
  • Longitudinal Studies
  • Magnetic Resonance Imaging
  • Pattern Recognition, Visual*
  • Photic Stimulation
  • Visual Cortex / physiology*

Grant support

Fondation Bettencourt-Schueller https://www.fondationbs.org/ Neuro-education. Received by SD. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Faculté de Medecine, University Paris 11 http://www.medecine.u-psud.fr/fr/index.html (grant number BQR 2007). Received by GDL. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Ecoles des Neurosciences de Paris http://www.paris-neuroscience.fr/ (grant number NERF 2007). Received by GDL. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.