Lexical learning of the English language: a PET study in healthy French subjects

Abstract

To investigate the neural correlates of word learning in adults, 10 right-handed French subjects who had learned English without mastering it performed an English and a French naming task during two PET sessions, one before (PET1) and the second after (PET2) a 4-week lexical training in English. Behavioral performance was collected during the two PET exams and 2 months after (T3). At T2, performance on English naming increased in all subjects; this improvement persisted at T3, with no correlation between English performance at T2 and T3. Cerebral activation during French naming mainly showed a left frontal temporal network. The pattern specifically associated with English lexical learning included, in addition to the anterior cingulate cortex involved in attentional processing and BAs 4/6 reflecting speech output, the right cerebellum and the left insular cortex that are linked to speech gesture learning, and the right medial temporal regions, likely to reflect the involvement of episodic memory during verbal learning. Correlations between English T2/T1 performance and English T2/T1 rCBF changes reinforced the hypothesis of intervention of episodic memory since they interested right frontal, hippocampal, and lateral temporal regions. ‘Predictive’ correlations between English T3/T2 performance and English T2/T1 rCBF changes showed, in good reminders, increased activities in the left posterior superior temporal sulcus and middle temporal cortex probably related to efficient semantic storage of learned words.