Cerebral organization in bilinguals: a PET study of Chinese-English verb generation.

Positron emission tomography (PET) was used to investigate cerebral organization in seven subjects who had Mandarin Chinese as their native language (L1), and learned English (L2) later in life. When activation from word repetition was subtracted from verb generation in L1 and L2, CBF increases were observed for both languages in left inferior frontal, dorsolateral frontal, temporal and parietal cortices, and right cerebellum. Direct comparison of the difference between verb generation and word repetition in L1 and L2 revealed no significant differences. Within-subject analysis of verb generation minus word repetition yielded CBF increases in left frontal cortex for all individuals for L1 and L2, and a comparison of differences yielded no spatial separation in frontal peaks. We argue for shared neural substrates even for such contrasting languages as Mandarin and English.