The nature of facilitation and interference in the multilingual language system: insights from treatment in a case of trilingual aphasia.

The rehabilitation study described here sets out to test the premise of Abutalebi and Green's neurocognitive model--specifically, that language selection and control are components of overall cognitive control. We follow a trilingual woman (first language, L1: Amharic; second language, L2: English; third language, L3: French) with damage to the left frontal lobe and left basal ganglia who presented with cognitive control and naming deficits, through two periods of semantic treatment (French, followed by English) to alleviate naming deficits. The results showed that while the participant improved on trained items, she did not show within- or cross-language generalization. In addition, error patterns revealed a substantial increase of interference of the currently trained language into the nontrained language during each of the two treatment phases. These results are consistent with Abutalebi and Green's neurocognitive model and support the claim that language selection and control are components of overall cognitive control.