Chapter 3.3 - Affective System, Emotions, and Stress

Abstract

The affective system is a network of cortical and subcortical anatomical structures which map sensory stimuli into rewards and punishments, express emotions in response to those stimuli and are responsible for feelings of those emotional reactions. Thus the affective system provides two new dimensions to behavior: negative and positive affective reactions and states. One of the hypotheses suggests asymmetric involvement of prefrontal cortical regions in positive affect (dominance of the left hemisphere), and negative affect (dominance of the right hemisphere). The left–right frontal asymmetry in human subjects is assessed in the anterior alpha asymmetry index of QEEG. The key structure of the affective system is the amygdala which receives sensory information, extracts affective memories, and sends the results to the prefrontal cortex. The amygdala reacts with increased activation to fearful stimuli and via feedback connection enhances early visual ERPs components (seen in anxiety). The other key structure of the affective system is the ventral part of the anterior cingulate cortex which receives strong input from amygdala and is in position of regulating the emotional state from restless anxiety to focused relaxation. The affective and cognitive control systems are mutually interconnected so that the dysfunctioning of the affective system can lead to impairment of cognitive control. The loss of cognitive control during stress exposure in turn leads to a number of maladaptive behaviors, such as drug addiction, smoking, drinking alcohol, and overeating. Prolonged stress is a major risk factor for depression, and exposure to traumatic stress can cause post-traumatic stress disorder. Among all neuromodulators the highest concentration of serotonin are found in the affective system.