Prolongation of Cerebral Activation in Response to a Stimulus as a Probable Mechanism of Associative Plasticity during Semantic Learning

Remembering the meanings of new spoken words is believed to occur as a result of associative learning. For example, this is how words denoting movements can be compared with their corresponding motor acts. Synaptic plasticity is known to develop in the brain when the activity of the cellular ensembles representing associated events coincides in time. However, in reality, such associations can develop when there is a significant time gap between the events to be associated, violating the conditions required for the occurrence of synaptic plasticity. We suggested that the conditions required for the development of synaptic plasticity in the brain can be created if the activity of neural representations is prolonged in time such that the required overlap in time at the level of neural ensembles is achieved. To test this assumption, we recorded magnetoencephalograms from voluntary participants during the development of associations between pseudowords and movements of the four limbs. The results obtained here show that there is indeed a significant prolongation of stimulus-induced auditory-verbal activation when new associations develop. Thus, during the development of an association, conditions can be created in the brain for the development of Hebbian plasticity, even if the associated events are separated in time.