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Chemistry of Emotions - A Review

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Abstract

Human body coordinates through chemical signals released by the brain. Chemical signals play a major role in bio-regulatory reactions responsible for emotions. Emotions are complex chemical reactions in nervous systemcharacterized by neurophysiologic changes associated with thoughts and behavioral responses. On pinching, one can cry, skin becomes hot, heart beat increases and our brain desires to shout out loud or hit something in return. We experience a sudden influx of physical and mental stimuli underlying a basic emotion. A person experiences diverse emotions throughout the day that are helpful in learning, reasoning and creativity. Emotions are one the most central and pervasive aspects of human experience. Emotions motivate empathic and moral behavior and play a role in an individual’s sense of self. While emotions enrich human experience they can also cause dramatic disruptions of judgment and performance. Since ancient days psychiatrists have been cracking the brain process responsible for emotions. Greeks were the first to find the link between the physical body and human emotional responses. Human brain is a complex network that transmit information every second via neurons through chemicals called neurotransmitters such as dopamine, serotonin etc. These chemicals essentially let the organs communicate with each other and express the emotions such as anger and happiness. Analysis of hormones and their effects on human behavior is a major contribution of biochemistry to the understanding of emotions and related behavior. In this article we are trying to provide an in-depth knowledge about chemistry of emotion which we experience every day.

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Here we show inverse fMRI activation patterns in amygdala and medial prefrontal cortex (mPFC) depending upon whether subjects interpreted surprised facial expressions positively or negatively. More negative interpretations of surprised faces were associated with greater signal changes in the right ventral amygdala, while more positive interpretations were associated with greater signal changes in the ventral mPFC. Accordingly, signal change within these two areas was inversely correlated. Thus, individual differences in the judgment of surprised faces are related to a systematic inverse relationship between amygdala and mPFC activity, a circuitry that the animal literature suggests is critical to the assessment of stimuli that predict potential positive vs negative outcomes.
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Our Social Self Preservation Theory asserts that situations which threaten the "social self" (ie, one's social value or standing) elicit increased feelings of low social worth (eg, shame), decrements in social self-esteem, and increases in cortisol, a hormone released by the hypothalamic-pituitary-adrenal axis. To test our theoretical premise, cognitive, emotional, and physiological responses to the performance of laboratory stressor tasks were compared in participants who performed these tasks in the presence or absence of social-self threat. Pre- and poststressor emotion, self-esteem, heart rate, blood pressure, and salivary cortisol were compared in 81 participants randomly assigned to complete speech and mental arithmetic stress tasks with social evaluation present (n = 41) or absent (n = 40). As hypothesized, participants in the social evaluation condition exhibited greater increases in shame and greater decrements in social self-esteem. Other psychological states (eg, anxiety, performance self-esteem) did not show differential changes as a function of the social context. Salivary cortisol increased in social evaluation condition participants but did not increase in participants who performed the same tasks in the absence of social evaluation. Cortisol increases were greater in participants who experienced greater increases in shame and greater decreases in social self-esteem under social-self threat. Threat to the social self is an important elicitor of shame experience, decreases in social self-esteem and cortisol increases under demanding performance conditions. Cortisol changes may be specifically tied to the experience of emotions and cognitions reflecting low self-worth in this context.
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