Emotions become destructive when normal neural systems for essential behavior go to extremes, compelling us to react in inappropriate, harmful ways. To understand why this happens so easily in modern life, we examine first the impact that the role of emotions as a survival mechanism in evolution has had on our neural architecture. The emotional centers developed early in evolution-our thinking brain, the neocortex, literally grew from the emotional centers; our thoughts and emotions are as intimately intertwined as the latticework of circuitry that regulates them. The design of brain integrates multiple networks from various regions that can play different roles at different moments. Some of these networks allow the emotional centers to override rationality in moments of perceived emergency, recruiting areas of the neocortex in what seems an emotional “hijack.” With this perspective from affective neuroscience as background, we can explore the classical Buddhist model of the “Three Poisons”–aggression, craving, and delusion–in terms of the neural processes at work in fear and anger; in ordinary pleasure and addiction; and in the role of emotional bias in cognition. The brain mechanisms by which negative emotions are regulated–amplified and attenuated–help to distinguish normal expression of these emotions from their destructive extremes. The trigger for turning them on involves circuits running from cortical sensory and perceptual processing zones to subcortical limbic structures including the amygdala. Anatomical data suggest that direct pathways exist between sensory regions of the thalamus and the amygdala, permitting the activation and learning of emotional responses in the relative absence of awareness. A circuit that includes inhibitory pathways from regions of the prefrontal cortex to the amygdala provides a mechanism by which activation of the amygdala, and negative affect, might be regulated. When this process fails, emotions may spiral out-of-control, becoming destructive. Circuits converging on the hippocampus determine whether an emotional reaction is appropriate; the over-generalized fearfulness in post-traumatic stress disorder likely emerges from trauma-induced abnormalities in the hippocampus and amygdala. Craving appears to arise from the pleasure-inducing dopamine system, which spurs us toward our goals in life and makes us feel satisfied when we attain them. But the repeated over-activation of this system in addictions produces structural alterations, which decreases the normal capacity to activate pleasure. This in turn fuels addictive behavior as people seek to re-experience the pleasure. Finally, emotions can bias cognition through the neural architecture connecting structures that generate the emotions to those brain systems involved in perception and attention. We can identify the neural mechanisms by which sustained emotional habits (e.g. the hypervigilance to threat common after trauma) result in an enduring sensory and perceptual bias, and thus to “delusion”.
- Dialogue 811 sessions
- March 22, 2000Dharamsala, Himachal Pradesh, India