Poster A88, Tuesday, August 20, 2019, 10:15 am – 12:00 pm, Restaurant Hall
Effortful verb retrieval from semantic memory drives beta suppression in higher-order motor areas
Boris Chernyshev1,2, Anna Pavlova1,2, Anna Butorina1, Anastasia Nikolaeva1, Andrey Prokofyev1, Maxim Ulanov1,2, Denis Bondarev1,3, Tatiana Stroganova1;1Moscow State University of Psychology and Education, 2National Research University Higher School of Economics, Moscow, 3National Research Center “Kurchatov Institute”, Moscow
The participation of the motor cortex in the semantic processing of verbs remains a subject of debate in neuroscience. The aim of the present study was to test the hypothesis that the motor circuitry contributes to semantic access to verbs representations. To this end, we examined whether the verb retrieval from semantic memory engages the motor cortex and whether this engagement is stronger when the more demanding memory search is required. We asked 33 participants to overtly produce related verbs in response to presented noun cues. The noun cues were either strongly associated with a single verb and prompted the fast and effortless verb generation (mean RT = 1.22 sec), or were weakly associated with multiple verbs and more difficult to respond to (mean RT = 1.89 sec). We used suppression of MEG beta oscillations (15-30 Hz) as an index of cortical activation and performed a whole-brain analysis to identify the cortical regions sensitive to the difficulty of verb semantic retrieval. The verb generation task induced a widespread beta suppression which started around 250ms after noun cue presentation and sustained until the overt production of the verb (p < 0.0001, FWE-corr.). The suppression was localised to a widely distributed left-hemispheric cortical network, that included the higher-order motor areas of the frontal lobe, classical auditory speech areas of the temporal lobe and memory-related structures at the mesial temporal surface (p < 0.05, Bonferroni-corr.). Crucially, despite the spread of beta suppression over the entire left hemisphere, the only cortical regions where beta suppression was sensitive to the semantic difficulty, were the premotor and supplementary motor areas on the lateral and medial surfaces of the frontal lobe. Stronger activation of the higher-order motor areas was observed under the more difficult task condition between -700 and -550ms before the response (p < 0.05, FWE-corr.), at the time window which substantially precedes the preparation of vocal response and likely overlaps with the semantic search for the target verb in both conditions. Given that greater allocation of processing resources in the higher-order motor areas was observed during the effortful memory search, we proposed that the re-activation of verb-related motor plans in higher-order motor circuitry serves to promote the semantic retrieval of target verbs. Thus, our findings support the “embodied cognition” view that motor associations contribute to verb semantic processing. Work on this study was supported by the Russian Science Foundation (grant 14-28-00234) and Core Funding of MEG centre from Ministry of Science and Education of RF.
Themes: Multisensory or Sensorimotor Integration, Language Production
Method: Electrophysiology (MEG/EEG/ECOG)