Poster D62, Monday, March 27, 8:00 – 10:00 am, Pacific Concourse
Primary motor cortex is involved in online word learning: A combined TMS-MRI study
Nikola Vukovic1, Yury Shtyrov1; 1Center of Functionally Integrative Neuroscience, Institute for Clinical Medicine, Aarhus University, Denmark
Language processing recruits a fronto-temporal cortical network, which is complemented by a distributed network of modal areas, such as the motor cortex, that encode modality-specific referential aspects of meaning. Since most studies typically focus on already fully-formed adult vocabulary, it remains unclear how and when exactly modality-specific areas become involved in language processing. Here, we addressed this using a 3D virtual reality-based learning game to teach adult participants new action verbs and object nouns, such that their meaning was learned in a contextually relevant and immersive fashion. We used offline continuous theta-burst stimulation over primary motor cortex (M1, defined using individual MRI images and fMRI localiser task) to test the hypothesis that this area selectively encodes aspects of action verb meaning early on in the process of word acquisition. Our results indicate that TMS of M1 (as opposed to a control site in a different participant group) interferes with the learning process, as revealed by a significantly increased number of errors during training. This variable encoding accuracy between the motor and control TMS groups was further corroborated in a post-learning lexical decision task, which showed that significant between-group RT differences were only pronounced for newly learned action verbs, but not for new nouns or real native words. These behavioural results are further accompanied by MRI measures of structural reorganisation within motor, inferior frontal and temporal regions of interest. Overall, our study highlights rapid brain plasticity during word learning, and the motor cortex’s functional involvement in its earliest phases.
Topic Area: LANGUAGE: Lexicon