Influence of the Working Memory Load on the Spatial Synchronization of Prestimulus Cortical Electrical Activity during Recognition of Facial Expression

The effect of increased working memory load (introduction of additional cognitive task into the context) was studied in adult healthy subjects (n = 35, 16 men, 19 women) in experiments with cognitive set. The EEG coherence in the frequency bands theta (4-7 Hz) and alpha (8-13 Hz), as well as alphal (8-10 Hz) and alpha2 (11-13 Hz) was analyzed and compared to the control data obtained in the experiments without additional memory load. Additional memory load was accompanied by an increase in the rigidity of the set to facial expression and substantial change in the pattern of the spatial synchronization of cortical potentials: coherence of potentials in the theta bands increased between the left and right frontal areas and between the frontal and temporal areas. A hypothesis is suggested that the rigidity of the set to emotionally negative facial expression is associated with the activation of the cortico-hippocampal system, which is justified by a substantial increase in coherence in the theta band in the frontal area known as the key structure in the functioning of cognitive sets. Loading the working memory is associated also with substantial weakening of the spatial synchronization of the low-frequency alpha rhythm, which presumably reflects the increase in the role of the fronto-thalamic system of selective attention in the process of recognition due to redistribution of attention induced by the additional cognitive task included in the context of current activity of a subject.