Mandarin and English single word processing studied with functional magnetic resonance imaging

The cortical organization of language in bilinguals remains disputed. We st udied 24 right-handed fluent bilinguals: 15 exposed to both Mandarin and En glish before the age of 6 years; and nine exposed to Mandarin in early chil dhood but English only after the age of 12 years. Blood oxygen level-depend ent contrast functional magnetic resonance imaging was performed while subj ects performed cued word generation in each language. Fixation was the cont rol task. In both languages, activations were present in the prefrontal, te mporal, and parietal regions, and the supplementary motor area. Activations in the prefrontal region were compared by (1) locating peak activations an d (2) counting the number of voxels that exceeded a statistical threshold. Although there were differences in the magnitude of activation between the pair of languages, no subject showed significant differences in peak-locati on or hemispheric asymmetry of activations in the prefrontal language areas . Early and late bilinguals showed a similar pattern of overlapping activat ions. There are no significant differences in the cortical areas activated for both Mandarin and English at the single word level, irrespective of age of acquisition of either language.