Differentiation of Primary Emotions through Neuromodulators: Review of Literature

Abstract

Emotional mental disorders are a leading cause of disabilities worldwide. Despite the obvious importance of emotion for human existence, controversy still abounds over the definition of emotion, the number of emotions that exit, whether different emotions have different physiological signatures. In this paper, we review papers about the emotional functions of neuromodulators: dopamine (DA), norepinephrine (NE), serotonin (5-HT) and acetyl choline (ACh), and propose that they act as the primary neural basis for 5 primary emotions (joy, anger/fear, sadness and missing). DA is a rewarding signal for salient stimuli such as food, sex and other needs. 5-HT has been related to depression for decades, it might be a marker for dislike/disgusting things. NE is the substrate for surprise, whose release induces “fight or flight” behaviors, or fear and anger emotions. Even though anger and fear are common emotions, there are no previous papers differentiating them or probing into their relationships. Here we found that fear and anger usually come hand in hand with fear followed by anger. And we give an equation to describe their relationships: The total amount of Surprise/stress = fear + anger. This equation fits in both duration and tension. Finally we introduced ACh emotions, which are opposite to NE induced stressful emotions. These emotions include “missing and wanting”, “calm/tame”, affectionate, submissive, et al. The significance of ACh emotions lies in the treatment for aggressive, impulsive behaviors, or phobia and manic disorders. In all, there might be 5 basic emotions (joy, anger/fear, sadness and missing).