Lecture 11a: Intro to Affective Neuroscience (The Emotion System)

Section 1: Theories of Emotion

Definitions of Emotion

• Cabanac (2002): Emotional experiences with high intensity and hedonic content.

• Ekman & Cordaro (2011): Discrete, automatic, involuntary responses influenced by life experiences.

• Merriam-Webster: Conscious mental reaction with intense feeling, often related to a particular object, involves physiological and behavioral changes.

• Oxford Dictionary: Strong feelings such as love or fear; part of a person’s character based on feelings.

• Textbook definition: Subjective mental state with distinctive feelings, cognition, behaviors, and physiological changes.

Theories of Emotion Overview

1. Folk Notion (Common-Sense Theory): Emotions cause automatic reactions.

   • Example: "I'm scared, so my heart races".

2. James-Lange Theory: Automatic reactions trigger feelings.

   • Example: "I feel fear because my heart races".

3. Cannon-Bard Theory: Simultaneous emotional experience and physiological reaction.

4. Schachter-Singer Two-Factor Theory:Cognitive attribution of emotion to arousal

   • Stimulus - physiological response - emotional response - interpretation

Section 2: Physiology and Behaviours of Emotion

Internal vs. External Experience

• Internal: Feelings (happy, anxious, sad).

• External: Behaviors (smiling, fidgeting, shouting).

• Emotions drive behaviours, e.g., anger -> aggression, happiness -> sociability.

Nervous System and Emotions

• Autonomic Nervous System: Activation leads to physical sensations associated with emotions.

  • Sympathetic Nervous System: Prepares body for fight-or-flight response.

  • Parasympathetic Nervous System: Prepares body for rest and recuperation (rest and digest)

Brain Structures Involved in Emotion

• Limbic System: group of brain structures crucial for regulating emotions

  • Amygdala: Processing emotions, particularly fear.

  • Hypothalamus: Manages physical responses to emotions.

  • Hippocampus: Involved in memory preservation and retrieval relevant to emotional experiences.

• Papez: lesions in the limbic system would impair emotional processing

• Emotions are a result of complex interactions across multiple neural networks, not solely confined to the limbic system. The limbic system plays a key role in the formation of neural chemicals and memories

Understanding Empathy

• Not strictly an emotion; influences emotionanal response via:

  • Cognitive: Understanding others’ emotions.

  • Affective: Sharing others’ emotions.

• Linked disruptions in empathy to mental health disorders like SUD and psychopathy.

Section 3: Core Emotions

Understanding Core Emotions

• Darwin’s perspective on universal expressions of emotions.

• Evidence from non-human primates and even mice regarding distinct emotional facial expressions.

• Emotional processing systems activated during emotional cues observed in mice.

Core Emotions

• Evolutionary significance: essential for survival (e.g., fear as threat detection, disgust as avoidance) and social communication

• Cultural variations in how expressions are displayed but some expressions are universally recognized.

Theories by Ekman and Plutchik

• Ekman's Core Emotions (8):

  • Anger, Sadness, Happiness, Fear, Disgust, Surprise, Contempt, Embarrassment.

• Plutchik's Wheel of Emotions: Distinct pairs of opposite emotions at varying intensities (aggressiveness to love, ecstasy to grief).

Summary of Core Emotions

• Biologically hardwired to facilitate survival and decision making

  • Amygdala and ANS regulate emotional responses

• Affected by cultural display rules and reflected in both humans and animals.

Section 4: Stress and the Body

Definition of Stress

• Viewed as a multidimensional process involving stress stimuli, processing systems, and physiological/behavioural responses.

Role of the Brain in Stress

• The hypothalamus is key in stress detection and response regulation.

• Allostasis: Brain’s adjustment of the body’s physiological state in response to stressors.

Stress Response Stages

1. Alarm Reaction: Immediate response, activation of the sympathetic nervous system, release of epinephrine (adrenaline) and norephinephrine (nonadrenaline) from adrenal medulla

2. HPA Axis Activation: Longer-term stress response involving hypothalamus stimulating the anterior pituitary and ACTH triggering the adrenal cortex to release cortisol

3. Adaptation: Adjusting to ongoing stressors

Hormones Involved in Stress

• Epinephrine & Norepinephrine: Increase heart rate and prepare the body for immediate action

• Cortisol: A steroid hromone that helps regulate metabolism and immune responses but can cause damage in excess

• ACTH (Adrenocorticotropic Hormone): Triggers cortisol production from the adrenal glands

• Glucocorticoid Receptors: Found in the brain; regulate cortisol levels and influence memory and learning

Long-term Effects of Stress

• Chronic stress can result in:

  • Increased cortisol levels impacting memory and learning

  • Structural changes in key brain regions

    • Shrink the hippocampus

    • Heighten amygdala activity

    • Impair prefrontal cortex function

  • Higher risks for anxiety, depression, and cognitive decline.

Conclusion on Stress

• Stress is a complex process involving multiple brain regions and physiological responses.

• Effective management of stress is critical for health.