Emotions, the amygdala, and the right hemisphere

No effort has still been made to integrate within a general model of emotions the relations between amygdala, fear (and other emotions) and the right hemisphere. This integration is the aim of this review that will start with the description of a model viewing emotions as a primitive adaptive system, alternative to the cognitive system. I will then analyze the main characteristics of the amygdala and of its subcortical pathway that allows to detect, with an urgency procedure, life-threatening stimuli, and to provide, with automatic and unconscious processing modalities, rough sensory data to the amygdala. Since this subcortical pathway is lateralized to the right hemisphere in humans, but not in animals, the reasons of this evolution will be discussed with reference to the "crowding model" , which assumes that brain lateralization may serve to avoid conflicts between systems (such as the emotional and the cognitive ones) competing at the decisional level. This model could explain the left lateralization of language and the consequent complex renovation of the working modalities of both hemispheres. Support to this model comes from the observation that the right hemisphere is characterized not only by a greater representation of emotions, but also by automatic and unconscious processing modalities typical of the emotional system, whereas the left hemisphere is characterized by language-mediated conscious and intentional functioning modalities.