Donald W. Pfaff and Helen E. Fisher
This theoretical essay proposes that underlying the concept of libido is a primitive set of brain mechanisms responsible for the generalized arousal of the central nervous system (CNS) and the activation of all behavioural responses. Having given the concept of ‘generalized CNS arousal’ an operational definition, we write an equation that describes how specific motivational needs are integrated with generalized arousal to produce an overall state of the CNS sufficient for potentiating behavioural responses. Factor analysis of behavioural data with mice suggest that among all CNS arousal-related influences, generalized
arousal contributes about a third of the variance. Many neuroanatomical, neurophysiological, and genomic mechanisms for arousal are reviewed here. Highlighted are large reticular formation neurons in the medulla whose axons bifurcating rostrally and caudally equip them to contribute, respectively, both to cerebral cortical arousal and to autonomic arousal. Their rapid responses would cause sudden changes in CNS state associated with, for example, states of panic or rapid sexual attraction. Consequences of the actions of generalized arousal networks include increased alertness and attention that serve all cognitive functions and all emotional expression. Specifically with respect to psychoanalytic concepts these networks provide the psychic energy necessary for the expression of libido.