Brain activity in bilingual developmental dyslexia: an fMRI study

The aim of this study was to identify the neural substrates of an adult English-German bilingual with dyslexia (in both languages) during lexical decision-making using functional magnetic resonance imaging (fMRI). A lexical decision task with five conditions in a block design was employed (nonverbal shape judgment, lettercase judgment, regular word judgment, irregular word judgment, and nonword judgment), and the activation was compared to a non-dyslexic control bilingual and a control monolingual participant. Both of the control participants matched the dyslexic bilingual BK on age, sex, IQ, handedness, and education level. Results indicated that the bilingual adult with dyslexia was strongly right lateralized for stimuli that required phonological processing, a profile that differed particularly from the activation observed from the monolingual participant. These results are consistent with the idea of increased activation (mostly in the right hemisphere) during linguistic tasks in adults with dyslexia and in late proficient bilinguals relative to monolinguals. Findings also suggest that the additional activation observed in both of the bilinguals are similar, suggesting that these effects are not additive in the dyslexic bilingual.