Dynamics of the gamma-band power of evoked responses to a facial expression in conditions of loading on working memory

The dynamics of power levels in evoked responses (0.8 sec) to stimuli with different facial expressions were studied in conditions of a cognitive set with an additional load on working memory in two groups of subjects: A) only "facial stimuli" (n = 29) and B) with an additional load (matrix of letters, n = 35). Wavelet power spectra of evoked responses to set stimuli were assessed in the band 15-60 Hz in the occipital, temporal, central and frontal areas. In both groups, power levels in evoked responses in the gamma2 range (41-60 Hz) were significantly higher in subjects with the plastic set type than in subjects with the rigid set type. In group A, the greatest increase in gamma2 band power to set stimuli at the set testing stage was seen in the central area of the left hemisphere. In conditions of increased loading on working memory (group B), increases in the power of evoked responses in both the gamma2 and gamma1 (21-40 Hz) ranges were seen in the occipital and temporal areas of both hemispheres, along with significant decreases in the central areas. The frontal areas showed no significant differences in evoked power in responses between subjects of the two groups. © 2013 Springer Science+Business Media New York.