The influence of orthographic depth on brain activation during reading: a meta-analysis of universal and orthography-specific effects

Richlan, F. , Martin, A. & Kronbichler, M.

Paris-Lodron-University of Salzburg, Department of Psychology, Centre for Cognitive Neuroscience

We used coordinate-based meta-analysis to objectively quantify reading-related functional neuroanatomical commonalities and differences between languages varying in orthographic depth. Specifically, we compared activation foci reported in 34 fMRI and PET studies in a deep orthography (DO: English) and in 32 such studies in shallow orthographies (SO: Dutch, Finnish, German, Greek, Italian, Spanish, Swedish). The separate meta-analyses showed universal reading-related brain activation common to both, DO and SO in core regions of the left hemisphere reading network including the ventral occipito-temporal cortex, the middle temporal gyrus, and the opercular part of the inferior frontal gyrus.
The direct statistical comparison between the two sets of studies revealed higher convergence of activation for DO compared with SO in the bilateral medial superior frontal cortex, the right cerebellum, the triangular part of the left inferior frontal gyrus, the left angular gyrus, and the left inferior temporal gyrus. Conversely, higher convergence of activation for SO compared with DO was identified in the left and right middle occipital gyrus, the left precentral gyrus, the left postcentral gyrus, and the left superior temporal gyrus.
The findings of the present meta-analysis are discussed in relation to current functional neuroanatomical models of reading acquisition and developmental dyslexia.