Lecture 11b: Introduction to Affective Neuroscience

Various Theories of Emotion

  • Folk Psychology

    • Feeling triggers autonomic reaction

    • Process:

    • Perception/Stimulus (e.g., Bang!)

    • Interpretation (e.g., danger)

  • James-Lange Theory

    • The autonomic reaction triggers the feeling

    • Process:

    • Specific pattern of autonomic arousal (e.g., heart races) leads to experienced emotion (e.g., fear)

  • Cannon-Bard Theory

    • Simultaneous feeling and autonomic reaction

    • Process:

    • Stimulus (Bang!) perceived as danger, resulting in

    • Concurrent arousal of autonomic reaction and experienced emotion (e.g., fear)

  • Schachter & Singer Theory

    • Cognitive attribution of emotion to arousal

    • Process:

    • Stimulus (Bang!) perceived as danger leads to

    • General autonomic arousal (e.g., heart races)

      • Followed by cognitive appraisal of context

      • Attribution of specific emotion (e.g., fear) responsible for arousal

Definitions of Emotion

  • Joseph LeDoux: Everybody knows what emotion is until asked to define it.

  • The Free Dictionary: Mental state arising spontaneously with physiological changes.

  • Oxford Dictionary: Instinctive or intuitive feeling, distinct from reasoning.

  • Merriam-Webster: Strong feeling directed toward a specific object with physiological and behavioral changes.

  • Kalat’s Biological Psychology: Emotions comprise cognitions, actions, and feelings.

Startle Reflex

  • Automatic responses to loud noises or sudden stimuli (e.g., puff of air to the eye).

  • Occurs within 5-10 milliseconds, varying with emotional state:

    • Increased in anxious state.

    • Decreased in relaxed or positive state.

Emotion Processing Pathways

  • Reflexive Pathway:

    • Sensory receptors → Pons.

  • Automatic Pathway:

    • Sensory receptors → Thalamus → Amygdala.

  • Conscious Pathway:

    • Sensory receptors → Thalamus → Visual Cortex → Amygdala.

Positive vs. Negative Emotions

  • While they are all based on similar definitions, positive and negative emotions differ significantly.

Positive Emotions

  • Benefits: Motivational, goal-oriented.

  • Too much leads to:

    • Impulsivity, reward-orienting, as if wearing horse-blinders, manic behaviour

  • Too little leads to:

    • Apathy, lack of motivation

Negative Emotions

  • Benefits: Protective against danger and harm.

  • Too much leads to:

    • Anxiety/depressive disorders, chronic stress

  • Too little leads to:

    • Poor choices, antisocial behavior, repeated mistakes

Stress and its Effects

  • Stress: Reaction to harm or threat.

  • Stressors: Stimuli causing stress.

  • Chronic Psychological Stress: Linked to health problems.

    • Short-term stress can be adaptive; long-term stress is maladaptive.

Stress and Brain Health

  • Hippocampus has many glucocorticoid receptors

  • Following stress:

    • Dendrites of pyramidal cells are shorter and less branches

    • Adult neurogenesis of granule cells are reduced

  • Effects blocked with adrenalectomy; produced with corticosteroids

Emotion System Evolution

  • Immune Function: Protects against foreign agents and bacteria

  • Pain: To protect against immediate external agents

  • Anxiety: To protect against non-immediate external agents

Relationship between Stress and Immune System

  • Acute stress can enhance immune function, whereas chronic stress impairs it

  • Stress triggers stress hormone:

    • Anterior-pituitary-adrenal-cortex system

      • Glucocorticoids, epinephrine, norepinephrine

    • Cytokines

      • Causing inflammation and fever)

  • Examples:

    • Rats receiving tail shocks show fever and increased white blood cell counts, indicating stress affects immune response.