Visual and motor cortices differentially support the translation of foreign language words

At present, it is largely unclear how the human brain optimally learns foreign languages. We investigated teaching strategies that utilize complementary information ("enrichment"), such as pictures or gestures, to optimize vocabulary learning outcome. We found that learning while performing gestures was more efficient than the common practice of learning with pictures and that both enrichment strategies were better than learning without enrichment ("verbal learning"). We tested the prediction of an influential cognitive neuroscience theory that provides explanations for the beneficial behavioral effects of enrichment: the "multisensory learning theory" attributes the benefits of enrichment to recruitment of brain areas specialized in processing the enrichment. To test this prediction, we asked participants to translate auditorily presented foreign words during fMRI. Multivariate pattern classification allowed us to decode from the brain activity under which enrichment condition the vocabulary had been learned. The visual-object-sensitive lateral occipital complex (LOC) represented auditory words that had been learned with pictures. The biological motion superior temporal sulcus (bmSTS) and motor areas represented auditory words that had been learned with gestures. Importantly, brain activity in these specialized visual and motor brain areas correlated with behavioral performance. The cortical activation pattern found in the present study strongly supports the multisensory learning theory in contrast to alternative explanations. In addition, the results highlight the importance of learning foreign language vocabulary with enrichment, particularly with self-performed gestures.