Catecholamine-containing neurones and electrical self-stimulation: 2. A theoretical interpretation and some psychiatric implications

Abstract

SynopsisA theory is proposed which relates the learning theory concepts of reinforcement and incentive motivation to visceral afferent pathways in the central nervous System. Herrick's hypothesis of the functional significance of the difference between olfactory and gustatory connexions is used to demonstrate a parallel between olfactory and ‘drive inducing’ stimuli in their role in energizing and directing behaviour; and a somewhat similar parallel between the roles of gustatory and ‘reinforcing’ stimuli. This theory is used to explain recent evidence that there is a relationship between catecholamine-containing neurones and electrical self-stimulation behaviour. It is proposed that self-stimulation can be understood as resulting in most instances from activation of one or both of two ascending Systems: (1) a ‘reinforcement System’ (which may be phylogenetically related to gustation), arising from cell-bodies in the locus coeruleus and releasing noradrenaline as a neurohumour from terminals distributed to the neocortex; and (2) an ‘incentive motivational’ System (which may be a phylogenetic derivative of olfactory pathways), arising from cell bodies in the ventral mesencephalon and releasing dopamine from terminals distributed to the corpus striatum and related nuclei. Some implications of this theory for the action of certain psychotropic drugs and the ‘catecholamine hypothesis’ of affective disorders are discussed.