Evaluation of the dual route theory of reading: a metanalysis of 35 neuroimaging studies
Abstract
Numerous studies concerned with cerebral structures underlying word reading have been published during the last decade. A few
controversies, however, together with methodological or theoretical discrepancies between laboratories, still contribute to blurring the
overall view of advances effected in neuroimaging. Carried out within the dual route of reading framework, the aim of this metanalysis was
to provide an objective picture of these advances. To achieve this, we used an automated analysis method based on the inventory of
activation peaks issued from word or pseudoword reading contrasts of 35 published neuroimaging studies. A first result of this metanalysis
was that no cluster of activations has been found more recruited by word than pseudoword reading, implying that the first steps of word
access may be common to word and word-like stimuli and would take place within a left occipitotemporal region (previously referred to
as the Visual Word Form Area—VWFA) situated in the ventral route, at the junction between inferior temporal and fusiform gyri. The
results also indicated the existence of brain regions predominantly involved in one of the two routes to access word. The graphophonological
conversion seems indeed to rely on left lateralized brain structures such as superior temporal areas, supramarginal gyrus, and the opercular
part of the inferior frontal gyrus, these last two regions reflecting a greater load in working memory during such an access. The
lexicosemantic route is thought to arise from the coactivation of the VWFA and semantic areas. These semantic areas would encompass a
basal inferior temporal area, the posterior part of the middle temporal gyrus, and the triangular part of inferior frontal gyrus. These results
confirm the suitability of the dual route framework to account for activations observed in nonpathological subjects while they read.