Schematic representation of the two stimulus GO/NOGO task Time dynamics of stimuli in four trial categories. Abbreviations: A, P, H are stimuli consisting of pictures of animals, plants and humans. GO trials require the subject to press a button. NOGO trials require suppression of a prepared action. IGNORE trials are stimuli pairs beginning with a picture of a plant, which require no preparation for action. NOVEL trials are stimuli pairs requiring no action, with the presentation of a novel sound together with the second human picture stimulus. Time intervals are depicted at the bottom.