[Changes in the cortical electrical activity during the formation of set in man]

The EEG spectral structure was studied in 30 healthy adult subjects during formation, realization of the verbal set and its disappearance. The subjects were divided in two groups according to the set stability: I-with the stable, II-with the unstable set (the set was maintained during 6-30 or 1-3 trials, respectively, in the subjects of the I and II groups). The background EEG records in the subjects of the I group were characterized by the dominance of the alpha-activity. Changes in the delta-rhythm power turned to be the most informative at different stages of the experiment. During the formation of the set its power was substantially lower in the subjects of the I than of the II group. During disappearance of the set effect there was a significant decrease in the delta-power in subjects of the II group. It is assumed that the formation of the stable fixed set is a stabilizing factor in behaviour which is reflected in the electrical activity of the cortex.