Research Article Changes in Cortical Thickness in 6-Year-Old Children Open Their Mind to a Global Vision of the World Nicolas Poirel, 1,2 Elise Leroux, 3,4 Arlette Pineau, 1 Olivier Houdé, 1,2 and Grégory Simon 1 1 LaPsyD ´ E, UMR 8240, CNRS, Universit´ e Paris Descartes and Universit´ e de Caen, Sorbonne, 46 rue Saint-Jacques, 75005 Paris, France 2 Institut Universitaire de France, 75005 Paris, France 3 ISTS, UMR 6301, CNRS, CEA, 14000 Caen, France 4 CHU de Caen, Service de Psychiatrie, Centre Esquirol, 14074 Caen, France Correspondence should be addressed to Nicolas Poirel; nicolas.poirel@parisdescartes.fr Received 20 February 2014; Revised 12 June 2014; Accepted 30 June 2014; Published 9 July 2014 Academic Editor: Tianming Liu Copyright © 2014 Nicolas Poirel et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Even if objectively presented with similar visual stimuli, children younger than 6 years of age exhibit a strong attraction to local visual information (e.g., the trees), whereas children older than 6 years of age, similar to adults, exhibit a visual bias toward global information (e.g., the forest). Here, we studied the cortical thickness changes that underlie this bias shit from local to global visual information. Two groups, matched for age, gender, and handedness, were formed from a total of 30 children who were 6 years old, and both groups performed a traditional global/local visual task. he irst group presented a local visual bias, and the other group presented a global visual bias. he results indicated that, compared with the local visual bias group, children with a global visual bias exhibited (1) decreased cortical thickness in the bilateral occipital regions and (2) increased cortical thickness in the let frontoparietal regions. hese indings constitute the irst structural study that supports the view that both synaptic pruning (i.e., decreased cortical thickness) and expansion mechanisms (i.e., increased cortical thickness) cooccur to allow healthy children to develop a global perception of the visual world. 1. Introduction Adults and children do not equally perceive the forest (i.e., global visual information) and the trees (i.e., local visual information). Even if objectively presented with similar visual stimuli, children younger than 6 years of age exhibit a strong attraction to local information, whereas children older than 6 years of age exhibit, similar to adults [1–3], a visual attention bias toward global information [4–6]. Because the global level (e.g., the whole, the forest) can be predicted from the identity of the local level (e.g., the features, the trees) and viceversa in a real-word situation, experimental materials that included a global level that could be apprehended independently of the local level (and vice versa) were developed by Navon [2, 7]. hese compound stimuli consisted of large global forms composed of small local elements (e.g., a global triangle composed of local circles; see Figure 1) that presented an elegant method for performing global/local studies. First, the set of possible global features is identical to the set of possible local features (i.e., both could represent any possible geometric form). Second, the independence of the global and local features is let intact, such that the geometric form presented at the global level cannot be predicted from the identity of the geometric form presented at the local level and vice versa. When children were presented with compound stimuli and asked to draw them from memory, Dukette and Stiles [8] showed that (1) global visual processing was not as fully developed in younger children and (2) compared with adults the younger children were biased toward the local level. An age-related change in global/local processing was proposed to be mediated by evolution of the visuospatial strategy employed by children [4, 9, 10]. In particular, ater the age of 6 years, children exhibit more exploratory eye movements than younger children, suggesting a shit from a local sampling strategy of visual information to a more exhaustive exploration of global visual stimuli [10, 11]. Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 362349, 7 pages http://dx.doi.org/10.1155/2014/362349