Prestimulus EEG gamma frequencies during formation of a cognitive set to facial expressions

The power spectra of baseline (prestimulus) EEG recordings from various parts of the cortex in the band 1–60 Hz were studied in adult subjects during the stage of formation of a cognitive set to facial expressions. Individual variability in the power spectra of the baseline EEG, particularly in the gamma range (41–60 Hz) made it impossible to average spectra from different subjects. This is the first study demonstrating that the EEG at 41–60 Hz was more informative during the prestimulus period than recordings at 1–20 Hz and 21–40 Hz. High levels of gamma-frequency power were found to be dominant in the frontal areas of the right hemisphere in groups of subjects with plastic sets; the group of subjects with a rigid set showed dominance of gamma-frequency power in the posterior temporal and occipital areas of the left hemisphere. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 58, No. 1, pp. 5–11, January–February, 2008.