Neurophysiology of Emotions

Introduction

Complex organisms must not only perceive and evaluate changes in their internal and external environment, but also generate appropriate responses to survive. In general, emotions help an organism to survive by embodying a multitude of nervous system functions for perception of the valuable components of the external environment. At the same time, emotions are a way for directly communicating our internal world to others through non-verbal means (Öztürk et al., 2005). Emotions aid an individual to interact with his/her external –or more specifically social- environment in a flexible way, while also helping in the regulation of an individual’s internal world.

Emotional information is used for personal, as well as social decision making of an individual with respect to the surrounding dynamical processes. Briefly, we can say that an emotion is an evaluative response. These responses are physiological and behavioral impulses that prepare the organisms for escaping or approaching dangerous versus safe objects. Actually, emotions consist of not a single but a multitude of responses in presence of a stimulus (Öztürk et al., 2005).

In summary, we can say that ‘emotions may be characterized as a response to an environmental event that allow for goal-directed behavior in the adaptation of the organism to changing environmental demands. This response involves cognitive, affective, behavioral, and autonomic sub-systems’ (Oatley & Jenkins, 1996; Hagemann et al., 2003). At a physiological level, most of the recent research in affective neuroscience strive to elucidate the prominent components of neural networks of emotion. When considered from this perspective, there are three distinct but complementary components of emotions (Bownds, 1999):

• 1.

  Physical sensation: Consists of the components within the autonomic nervous system which we call physiological arousal.

• 2.

  Emotional expression: Consists of our behaviours such as facial expressions, gestures and posture for reflecting our feelings such as sadness, anger, happiness.

• 3.

  Subjective experience: Consists of the personal feeling of our current emotion such as fear, anger, and happiness.

It is extremely difficult to identify all emotional states that we go through. Because of this, emotions can be simply categorized as basic (primary) and social (secondary). The basic emotions are innate and related to the anatomical structures in the limbic system (for ex. Amygdala). They consist of organized automatic and stereotypical behaviours (Izard, 2009), that are consistent across cultures. These basic emotions are essential for survival, evolution and development. There are six basic emotions that are widely accepted: happiness, sadness, anger, fear, disgust, and surprise. These emotions can further be grouped as pleasant (happiness, surprise) and unpleasant (sadness, anger, fear, disgust). The pleasant emotions consist of positive affect causing approach to stimuli whereas the unpleasant emotions consist of negative affect that is repellant (Izard, 2009). On the other hand, social emotions differ from the basic emotions primarily because they are learned through social interaction as the individual grows. Social emotions embody personal experiences such as guilt, embarrassment/shame, and pride (Damasio, 1994). Other than these, it is also necessary to consider background emotional processes such as mood, which are elicited in a totally different way.

Physical Sensation And Autonomic Nervous System

When we investigate areas that are responsible of the complementary components of emotions, we would have to say that the hypothalamus, brain stem, and medulla spinalis are specifically responsible from the physical sensations which include physiologic components of the autonomic nervous system (see Figure 1).

Figure 1.

Main structures those are responsible from the physical sensation of emotion