Richlan, F. 1 , Martin, A. 1, 2 & Kronbichler, M. 1, 2
1 University of Salzburg
2 Christian-Doppler-Klinik
We used coordinate-based meta-analysis to quantify commonalities and differences of dyslexic functional brain abnormalities between alphabetic languages differing in orthographic depth. Specifically, we compared foci of under- and overactivation in dyslexic readers relative to non-impaired readers reported in 14 studies in deep orthographies (DO: English) and in 14 studies in shallow orthographies (SO: Dutch, German, Italian, Swedish). The separate meta-analyses of the two sets of studies showed universal reading-related dyslexic underactivation in the left occipito-temporal cortex (including the visual word form area). The direct statistical comparison revealed higher convergence of underactivation for DO compared with SO in bilateral inferior parietal regions, left inferior frontal gyrus pars triangularis, left precuneus, and right superior temporal gyrus, together with higher convergence of overactivation in the left insula. Higher convergence of underactivation for SO compared with DO was found in the left fusiform gyrus, left temporo-parietal cortex, left inferior frontal gyrus pars orbitalis, and left frontal operculum, together with higher convergence of overactivation in the left precentral gyrus. Taken together, the findings support the notion of a biological unity of dyslexia, with additional orthography-specific abnormalities and presumably different compensatory mechanisms. The results are discussed in relation to current functional neuroanatomical models of developmental dyslexia.