Chapter 18 Brain Mechanisms of Emotion

Introduction Significance of Emotions –Emotional experience; Emotional expression –Study behavioral manifestations Animal models, brain lesions –Human brain imaging techniques Renaissance in the study of emotion Affective neuroscience Neural basis of emotion and mood

What Is Emotion? Theories of Emotion –The James-Lange Theory of Emotion - within human beings, as a response to experiences in the world, the ANS will create physiological events such as muscular tension, a rise in heart rate, perspiration, and dryness of the mouth etc. Therefore, emotions are feelings that arise as a result of these physiological changes, rather than being their cause. –The Cannon-Bard Theory - also known as the thalami theory, suggests that individuals experience emotions and physiologically react simultaneously.

William James & Carl Georg Lange

William Cannon and Phillip Bard

The Limbic System Concept Broca’s Limbic Lobe –Cortex forming a ring around corpus callosum: Cingulate gyrus, medial surface temporal lobe, hippocampus

What Is Emotion? Unconscious Emotions –Stimulus can have emotional impact without conscious awareness and increased activity in the amygdala

The Amygdala and Associated Brain Circuits Anatomy of the Amygdala

The Limbic System Concept The Papez Circuit – the major pathway of the limbic system chiefly involved in the cortical control of emotion. This circuit plays a role in storing memory. Papez discovered the circuit after injecting rabies virus into a cat's hippocampus and monitoring its progression through the brain. The initial pathway was described as follows:

James Papez

The Limbic System Concept The Papez Circuit –Cortex: Emotional experience –Hippocampus: Behavioral expression of emotion Rabies infection:Implicates hippocampus in emotion, -> Hyperemotional responses –Anterior thalamus Lesions lead to spontaneous laughing, crying –Paul MacLean popularized term “limbic system” Evolution of limbic system allows animals to experience and express emotions beyond stereotyped brain stem behaviors Paul MacLean

Serotonin and Aggression Neurotransmitter Serotonin Serotonergic raphe neurons project to the hypothalamus and limbic structures via the medial forebrain bundle  Serotonin turn-over  aggression in rodents