[Methodologic aspects in psychopharmacology]

During the planning and carrying out of clinical trials on potential psychotropic agents various difficulties arise when applying experimental-psychological procedures, especially on self- and non-self-rated behaviour. The action of these substances is extraordinarily complex and the behaviour, which is the most obvious component, is only an indirect measure of central effects. Thus, it is also essential to take into consideration the physiological and biochemical components in order to clarify the relationship between effects on the brain and finally on behaviour. It is possible, for example, to register changes in EEG in connection with attention and reaction time tests also in healthy persons. Actually, most psychotropic substances can only be differentiated by means of their effects on human beings. That means that ingenious methods must be elaborated in order to be able to recognize the influence on the human brain and thus to explain the mechanism of action.