Learning to associate novel words with motor actions: language-induced motor activity following short training

Action words referring to face, arm or leg actions activate areas along the motor strip that also control the planning and execution of the actions specified by the words. This electroencephalogram (EEG) study aimed to test the learning profile of this language-induced motor activity. Participants were trained to associate novel verbal stimuli to videos of object-oriented hand and arm movements or animated visual images on two consecutive days. Each training session was preceded and followed by a test-session with isolated videos and verbal stimuli. We measured motor-related brain activity (reflected by a desynchronization in the μ frequency bands; 8-12 Hz range) localized at centro-parietal and fronto-central electrodes. We compared activity from viewing the videos to activity resulting from processing the language stimuli only. At centro-parietal electrodes, stable action-related μ suppression was observed during viewing of videos in each test-session of the two days. For processing of verbal stimuli associated with motor actions, a similar pattern of activity was evident only in the second test-session of Day 1. Over the fronto-central regions, μ suppression was observed in the second test-session of Day 2 for the videos and in the second test-session of Day 1 for the verbal stimuli. Whereas the centro-parietal μ suppression can be attributed to motor events actually experienced during training, the fronto-central μ suppression seems to serve as a convergence zone that mediates underspecified motor information. Consequently, sensory-motor reactivations through which concepts are comprehended seem to differ in neural dynamics from those implicated in their acquisition.