In this chapter we attempt to synthesize knowledge from disciplines concerned with human behavioural organization with the aim of developing a unified psychophysiological approach to the brain mechanisms underlying (a) the expression of depressive symptoms as defined by Beck's cognitive theory of depression and (b) the psychological and/or pharmacological treatment of these symptoms. This synthesis is based on a psychophysiological model of brain functioning which was originally developed to explain dream mentation, i.e. mental experiences by healthy adults which are distinctly different from wakeful thinking and feeling (Koukkou and Lehmann 1980, 1983a). The application of the model to schizophrenic symptomatology and treatment and to neurotic symptomatology and treatment is discussed elsewhere (Koukkou 1980, 1987; Koukkou and Lehmann 1980, 1983b).