The neuroanatomy of bilingualism: how to turn a hazy view into the full picture

Epub ahead of print 07/09/2015.This article was originally published with errors. This version has been amended. Please see Corrigendum (http://dx.doi.org/10.1080/23273798.2016.1144398).The neuroanatomical bases of bilingualism have recently received intensive attention. However, it is still a matter of debate how the brain structure changes due to bilingual experience since current findings are highly variable. The aim of this review is to examine these structural studies from a methodological perspective and to discuss two major methodological problems that could give rise to this variability. The first problem is sample selection, an issue directly related to the heterogeneous nature of bilingualism. The second problem is the inconsistency in the methods used for the analysis of brain imaging data. This review reveals that although structural changes related to bilingualism have been reported in regions comprising language/cognitive control and language processing, these results are not yet sufficiently numerous or consistent to allow important generalizations to be reached. Consequently, current evidence offers ambiguous support for neural models of bilingualism. This shortcoming in the field is exacerbated by critical methodological differences between studies that only further complicate the matter. We conclude by identifying issues that should be taken into consideration so that studies are more comparable and results are easier to aggregate and interpret. We also point out future directions that would allow for progress in the field.This article was partially supported by grants CONSOLIDERINGENIO2010 CSD2008-00048, PSI2012–32123 and PSI2012– 31448 from the Spanish Ministry of Science and Innovation, by ERC-2011-ADG-295362 grant from the European Research Council and by the AThEME project funded by the European Union Seventh Framework Programme [grant number 613465]