Chapter 18 Outline

Brain Mechanisms and Emotions

• Affects

  • Affective Neuroscience: the investigation of the neural basis of emotion and mood

  • Affective Disorders: mood disorders such as depression

• Emotional Experience vs. Emotional Expression

  • Emotional Experience: the subjective, phenomenological experience of emotions

  • Emotional Expression: the physiological and behavioral responses associated with emotional states

• Basic Emotions vs. Dimensional Theories

  • Basic Theories of Emotion: certain emotions are unique, indivisible experiences that are innate and universal across cultures

    • Basic Emotions: anger, disgust, fear, happiness, sadness, and surprise

    • Experiments: the meaning of basic emotions can be translated through photos, regardless of the subjects background

  • Dimensional Theories of Emotion: emotions can be broken down into smaller fundamental elements combined in different ways and differing amounts

    • Affective Dimensions: valence (pleasant—unpleasant) and arousal (weak emotion—strong emotion)

    • Problems: does not distinguish between emotions like fear and anger that are both high arousal and negative valence

    • Solutions: Psychological constructionist theories of emotion - an emotional state is constructed from physiological processes that do not concern only emotion

      • Examples: language, attention, internal sensations, and external stimuli

      • Results: produces emotions as a consequence

• Early Theories of Emotion

  • Humourism: the body is filled with four fluids whose concentrations reflect emotional expressions

    • Blood: (sanguine) passion [red]

    • Yellow Bile: (choleric) anger

    • Black Bile: (melancholy) depression

    • Phlegm: (phlegmatic) dullness [blue]

  • James-Lange: we experience emotion in response to physiological changes in our body

  • Cannon-Bard: subcortical brain activity triggers emotional experience and autonomic response

  • Schachter: the body responds to a stimulus and appraisal (thinking of the situation) causes a conscious feeling

  • Common Sense: we experience an emotion which causes an autonomic response

• Capilano Canyon Suspension Bridge

  • Experiment: male participants were tasked to either take a path across a scary bridge or a boring path

  • Outcome: males that crossed the bridge had a racing heart rate

  • Twist: an attractive female researcher met the male participants at the end of the bridge or boring path and were asked to call if they wanted to

    • Outcome: the males who crossed the scary bridge were more likely to call

    • Proposed Reasoning: the racing heart rate switched from thinking of the scary bridge to the arousal from the female researcher on the other side

• The Papez Circuit

  • Theory: there is an emotion system lying on the medial wall of the brain that links the cortex with the hypothalamus

  • Circuit: emotional stimulus → thalamus → sensory cortex → cingulate cortex (feeling) → hypothalamus (bodily response → anterior thalamus → cingulate cortex

• The Limbic System

  • Paul Maclean: proposed this system by expanding on the Papez circuit; added the amygdala

  • Problems: no reason to think that only one system is involved + inclusion of the hippocampus makes the it more of a memory system

• Phineas Gage

  • Story: A large metal rod went through his head damaging the prefrontal cortex, but did not disturb his perception or intelligence

  • Findings: Changes in emotional expression and increased behavioral problems

    • Further Findings: Gage may have recovered from some of his injuries related to behavioral problems

• Emotions and Decision Making

  • Importance: emotions are important for decision making

    • Evidence: damage to the ventromedial prefrontal cortex makes it difficult to make decision

• Fear and Temporal Lobectomy (w/ Amygdala)

  • Changes in Monkeys: lack of fear and anxiety, hypersexuality, oral fixations, decrease of fear and aggression

  • Changes in Humans (following Kluver-Bucy syndrome): flattened affect, inappropriate sexual behaviors, oral fixations, poor visual object recognition

• Fear Conditioning

  • Learned Fear: memories and emotional events that cause us to avoid certain behaviors

  • Classical (Pavlova) Fear Conditioning: experiments that suggest neurons in the amygdala can learn to respond to stimuli associated with pain, which evokes a fearful response

    • Experiment:

      • A mouse is put in a room and played a sound

      • A shock (unconditioned stimulus) is given when the sound is played, which causes the mouse to freeze (unconditioned response)

      • Eventually, the mouse freezes (conditioned response) when the sound is played (conditioned stimulus) regardless if the shock is given

• Amygdala Pathways and Fear Conditioning

  • Divisions of the Amygdala: basolateral, corticomedial, and central nuclei

  • Basolateral: receives auditory, visual, gustatory, and somatosensory info

  • Corticomedial: receives olfactory info

  • Central: triggers behavioral, ANS, and hormonal responses

• SM’S Amygdala Lesion

  • Symptom: decreased ability to recognize fear in faces from visual input alone

  • Free Viewing of Faces: SM would not look at people’s eyes when trying to recognize facial expressions

  • Instructed Viewing of Faces: SM was able to recognize the facial expression better when told to look at an individual’s eyes

  • Feinstein et. al. Experiment: researchers exposed SM to snakes, spiders, and a haunted house; SM showed no fear

• Unconscious Emotion

  • Unconscious Emotions: sensory input causes emotional effects on the brain without us being aware of the stimuli

  • Experiment: subjects were shown an emotional face then an angry face with an unpleasant sound, ANS skin conductance was recorded; showing an angry face a split second before an expressionless face caused increase skin conductance via the ANS and higher amygdala activity even though the subjects were not aware of the angry face

• Anger vs. Aggression

  • Anger: emotional response

  • Aggression: violence or threat of violence

    • Types of Aggression: defensive, rage, predatory, intermale, maternal, and territorial

    • Predatory: involves attacks against a member of a different species for the purpose of obtaining food

      • Instrumental Aggression: premeditated aggression

    • Affective: involves a show of aggression rather than aggression to kill for food (vocalizations)

      • Reactive Aggression: hot-headed aggression

• Feline Aggression

  • Medial Hypothalamic Stimulation: leads to affective aggression (hissing & growling)

  • Lateral Hypothalamic Stimulation: leads to predatory aggression (quiet biting)

• Rage Circuits

  • Affective Aggression Pathway: amygdala → medial hypothalamus → periaqueductal gray

  • Predatory Aggression Pathway: mesolimbic dopamine system (substantia nigra and VTA)

• 5-HT and Testosterone

  • 5-HT: important in regulating anger and aggression; inverse relationship

    • MAO-A “Warrior” Gene: monoamine oxidase does not break down 5-HT, resulting in more aggressive behavior

  • Testosterone: stimulates vasopressin production, which promotes intermale aggression (in non-human animals)

    • Other Effects: less clear in other types of aggression