PROLONGATION OF STIMULUS REPRESENTATION IN THE BRAIN AS A PROBABLE MECHANISM OF ASSOCIATIVE PLASTICITY IMPLEMENTATION DURING SEMANTIC LEARNING

It is believed that memorization of the meaning of new words occurs due to associative learning. For example, it may be matching of a word to the corresponding motor act. Synaptic plasticity in the brain develops on condition that activity of cell ensembles representing the associated events coincides in time – however, in reality, during the development of such associations, a significant time gap between the associated events is likely, which compromises necessary conditions for synaptic plasticity. We hypothesized that conditions for the development of synaptic plasticity may be created by way of prolongation in the activity of neuronal representations, thus providing for the required overlap in time at the level of neuronal ensembles. To test this assumption, we recorded magnetoencephalogram in volunteers during acquisition of associations between pseudowords and movements by four limbs. The results of the study show that there indeed occurs a significant prolongation of stimulus-induced auditory speech activation during the development of new associations. Thus, during the development of the association in the brain, the necessary conditions for Hebbian plasticity can be created – even if the events being associated are separated in time.