[Blocking of the alpha rhythm induced by sensory self-stimulation]

In a series of experiments in animals and in man several authors have shown that sensory stimulation induces low voltage fast activity in the EEG. The problem to be studied in this work is related to the EEG changes produced by self-stimulation. A group of human subjects were instructed to be self-stimulated with clicks and flashes of light randomly applied by themselves. When the subjects were with the eyes closed and in resting state, alpha rhythm was predominantly recorded in the EEG. However, during acoustic or visual stimulation a low voltage fast activity was predominantly observed in the EEG. In self-administration of the stimulus a low voltage fast activity was recorded in the EEG several seconds before the stimulus application. These results suggest that the activation of a complex neuronal mechanism involved in the volitive response, as well as anxiety and attentive states of the subject occurring before the actual stimulation to select the moment at which the stimulus has to be applied, can be responsible for the blocking of the alpha rhythm previously to the flashes of light and clicks presentation.