ИСТИНА

Neural mechanisms leading to formation of an associative link between action words and respective movements remain largely unknown. In motor learning, the post-movement increase in beta oscillations (BO) is implicated in the strengthening of the just learned motor program (Tan et al., 2014). Here, we tested hypothesis that the post-movement BO similarly promote a newly formed association between a movement and an auditory novel word that denotes this movement. We recorded MEG while 24 volunteers performed a trial-and-error search for unique associations between four acoustically presented pseudowords and movements by hands and feet. We assessed pre-movement (Pre-M) and post-movement (Post-M) changes in beta power (i) at the beginning of learning when movements to the presented pseudowords were exploratory; (ii) at the advanced stage of learning when movements became uniquely associated with specific pseudowords; (iii) during self-paced movements. We hypothesized that Post-M BO would be expressed stronger at the advanced learning stage when the pseudoword-movement association were to be maintained, compared to the onset of learning when a change of a movement was probable, or during the self-paced movements when there was no memorization task. In line with the previous findings, we observed decrease in BO during the movement preparation and execution, and increase after the movement completion in all three conditions. The strongest beta decrease in Pre-M period was observed at the beginning of the learning as compared to both the advanced learning, and, especially, to the self-paced movements (p<0.05, FDR-corr.), reflecting the difficulty of choosing between several competing motor programs. Crucially, Post-M BO were dramatically increased at the advanced learning stage as compared to both the self-paced and the exploratory movements (p<0.05, FDR-corr.). The source-space analysis showed that the learning-related increase in Post-M beta power occurred in a widespread cortical network including not only sensorimotor cortex, but also memory-related regions (retrosplenial and parahippocampal cortex), the medial and lateral prefrontal cortex, and classical "language" area in left inferior frontal gyrus. We suggest that Post-M BO serve to promote and reinforce the evolving action word representation by strengthening of long-range interactions (Benchenane et al., 2011).