Chapter 10: Emotion
Lecture Outline
Emotional Responses
Theories of Emotion
Communication of Emotion
Aggression
Emotion Definitions
Emotions refer to perturbations of
Response patterns (subserve function)
Behavioral: muscle response (jump, run, facial)
Autonomic: sympathetic activation
Hormonal: secretion of stress hormones
Feelings
Negative (anxiety, fear, anger)
Positive (euphoria: rarely studied)
Role of Central Amygdala Nucleus in Emotional Responses
Threat stimuli increase neural firing and fos activity within central nucleus of the amygdala
Lesions of central nucleus diminish emotional responses:
Reduced fear responses to threat stimuli
Reduced levels of stress hormones
Electrical stimulation of central nucleus induces fear and agitation
Conditioning of Emotional Responses
Fear stimuli elicit emotional responses
e.g. Loud noises, painful stimuli
Fear stimuli can be associated with neutral stimuli
e.g. Places, sights, sounds, smells
The neutral stimulus in turn can elicit the emotional response
Termed the Conditioned Emotional Response (CER)
Central Amygdala Nucleus and Fear
Lesions of the central nucleus abolish CER to tones previously paired with footshock (LeDoux experiments)
Central nucleus projects to LH and PAG
Mediates blood pressure changes, freezing
Tranquilizers act via the central nucleus to reduce anxiety
Damage to the Orbitofrontal Cortex
Phineas Gage: dynamite tamping rod penetrated orbitofrontal cortex
Damage reduced inhibitions and self-concern
Jacobsen: reported calming action of frontal lobe damage in monkeys
Led to development of prefrontal lobotomy technique (Moniz)
James-Lange Theory of Emotional Feelings
Emotional stimuli evoke physiological reactions including muscle contraction
Sensory feedback from reactions is perceived by brain to generate feelings
Supported by:
Hohman’s study of spinal cord transections:
Low transections produced greater reduction in emotional intensity
Facial Feedback
Ekman asked subjects to move facial muscles so as to create facial expressions that accompany emotions.
Different emotional expressions produced different changes in autonomic NS activity:
Anger: increased HR and skin temperature
Fear: increased HR but decreased skin temperature
Happiness: decreased HR, no change in skin temperature
Facial Expressions Signal Emotion
Darwin: emotions are innate patterns of muscle contraction, often of the facial muscles (snarling vs sneering)
Facial expressions signal our emotional states to others
Facial expressions are common across cultures
Facial expressions are similar in blind and sighted children
Recognition of Emotion
We infer emotional states using
Visual cues (facial expression, body language)
Auditory cues (intonation)
Recognition of emotion in others involves the right hemisphere
Left-ear and left-visual field advantage
Right hemisphere lesions impair recognition of emotions from facial expressions or hand gestures
Aggressive Behavior
Aggressive behaviors are
Threatening gestures (hissing, posturing)
Physical attack (biting, striking)
Aggressive behavior can be functional
Gain access to mates
Defend offspring against intruders
Distinct from predation
Aggressive Situations
Inter-male aggression
Female aggresion
Maternal aggression
Infanticide
Neural Controls of Aggression
Electrical stimulation of the PAG elicits defensive attack and predation
Separate neural circuits:
Defensive attack stimulation is aversive
Predatory attack stimulation is reinforcing
PAG stimulation is enhanced via activity of medial hypothalamic neurons
Serotonin and Aggression
Inverse relation between brain serotonin activity and aggression
Serotonergic agonists are used therapeutically to inhibit human aggression
Damage to forebrain 5-HT neurons increases aggression
Low 5-HIAA levels predict risk-taking behavior in monkeys
Hormonal Influences on Aggression
Aggressive behaviors contribute to reproduction
Hormones modulate intermale aggression in similar ways to effects on reproduction
Organizational effects of early androgen exposure
Activational effects of androgens in adulthood
Importance of medial preoptic area for aggression