Neurobiological bases of individual differences in emotional and stress responsiveness: high responders-low responders model.

Our understanding of the neurobiological bases of emotional responsiveness derives from 2 major classes of work. The first class represents studies interested in brain sites and associated molecules that respond to fear and anxiety. The other class explores the brain circuits that regulate physiological responses to stress. These 2 classes of work do not contradict each other. In contrast, they coalesce into a coherent body of information of great importance to understanding emotion. We believe that animal differences in emotional reactivity involve some of the same neuronal circuitry that is relevant in humans. This circuitry includes the paraventricular nucleus of the hypothalamus (PVN), monoaminergic nuclei in the midbrain, amygdala, prefrontal cortex, hippocampus, and other limbic and limbicassociated areas. This circuitry determines how an individual perceives a stress and copes with it. It is a disruption of this circuitry that is responsible for why some individuals develop anxiety and major depressive disorders. In this article, we describe what is known about this emotional circuitry among animals that differ in emotional reactivity and stress responsiveness.