  The role of the motor cortex in perceptual and cognitive functions is highly
controversial. Here, we investigated the hypothesis that the motor cortex can
be instrumental for translating foreign language vocabulary. Participants were
trained on foreign language (L2) words and their native language translations
over four consecutive days. L2 words were accompanied by complementary gestures
(sensorimotor enrichment) or pictures (sensory enrichment). Following training,
participants translated the auditorily-presented L2 words that they had learned
and repetitive transcranial magnetic stimulation (rTMS) was applied to the
bilateral posterior motor cortices. Compared to sham stimulation, effective
perturbation by rTMS slowed down the translation of sensorimotor-enriched L2
words - but not sensory-enriched L2 words. This finding suggests that
sensorimotor-enriched training induced changes in L2 representations within the
motor cortex, which in turn facilitated the translation of L2 words. The motor
cortex may play a causal role in precipitating sensorimotor-based learning
benefits, and may directly aid in remembering the native language translations
of foreign language words following sensorimotor-enriched training. These
findings support multisensory theories of learning while challenging
reactivation-based theories.
