AMYGDALA, EMOTIONS, MOTIVATION, AND DEPRESSIVE STATES

It is concluded that experiments on animals give exciting perspectives for investigations of amygdalar mechanisms in humans and may be useful for treatment of emotional disorders, depression, and neuroses.

Abstract

The first point postulated in this chapter is that emotions are physiological events, accessible for objective, experimental investigations. They are related to biological needs, they constitute “fuel for drives” and they determine the negative and positive hedonic value of inner and outer stimuli. Emotions are a crucial link in the chain of mechanisms that convert sensory inputs into subjective feelings and, according to their hedonic meaning, direct behavioral acts. The second important point concerns the role of the amygdala in the emotional processes used for the evaluation of internal and external stimuli with respect to biological usefulness and bidirectional hedonic values. Amygdala and hypothalamus are reciprocally interconnected and act as a unit. In both structures it is possible to distinguish positive and negative hedonic systems, as well as excitatory and inhibitory ones. Specific and generally modulating functions of these structures are interrelated. Within the amygdaloid complex two antagonistic parts, an excitatory dorso-medial (DMA) part and inhibitory lateral (LA) part can be functionally distinguished. Damage of DMA produces, besides impairment of specific functions, general apathy and sadness, whereas damage of LA evokes increased activity, joyfulness, liveliness, and social responses. Behavioral multifactor syndromes produced by damage of DMA may be reversed by subsequent damage of LA. The DMA syndrome may be compared to general depression and serves as a good model for investigating mechanisms of depressive states. It is concluded that experiments on animals give exciting perspectives for investigations of amygdalar mechanisms in humans and may be useful for treatment of emotional disorders, depression, and neuroses.