Language-specific activations in the brain: Evidence from inflectional processing in bilinguals

We investigated the neural correlates of morphological processing in two structurally different languages within the same individuals. An interesting contrast is provided by Finnish and Swedish where most inflected Finnish nouns tend to show a processing cost (i.e., longer reaction times and higher error rates) compared to monomorphemic nouns, while most inflected Swedish nouns do not show such a cost. This has been taken as evidence for morphological decomposition in Finnish and full-form recognition of inflected nouns in Swedish. While most previous imaging studies had studied the two morphological processing routes (decomposition and storage) within the same language and often by comparing regular vs. irregular forms, we employed a cross-language setting and a direct contrast between morphologically complex vs. simple words. We subjected high-proficient Finnish–Swedish early bilinguals to a visual lexical decision task with inflected vs. monomorphemic Finnish and Swedish nouns while measuring their brain activation by fMRI. The participants showed an inflectional processing cost and related left fronto-temporal activation increases in Finnish but not in Swedish. This suggests a language-specific processing difference in the brain, possibly reflecting the structural difference between these two languages. In addition, the activations appeared in regions related to lexical-semantic and syntactic processing rather than visual word form processing. This is in line with previous studies in Finnish, suggesting that the morphological processing cost stems primarily from the later, semantic-syntactic stage.