Increased negative discordance of the dominating mode of the pressing duration histogram (PDH), which correlates with the growth of fixed bursts of stimulation is accompanied by a progressive decrease in the reinforcing properties of self-stimulation (SS), avoidance of the pedal and at the same time by a change of behavioral grooming reactions in the intervals between SS for search and consummatory reactions. Hunger considerably shortens the preferable duration of pressing or leads to the appearance of an additional mode on the PDH. With the change of the dominating PDH mode from positive discordance to a negative one, brain stimulation acquires aversive properties which are apparently due to the activation of the mechanisms of specific motivations.