Introduction to Behavioral Neuroscience: Emotions and Mood Study Guide

Definition and Core Concept of Emotion

  • Emotion is defined as complex instinctive feelings produced by synthesizing environmental cues and external stimuli that alert an organism that some action may be required of them.
  • The study of emotions and mood is classified under Chapter 13 of Behavioral Neuroscience by Dr. Cedric L. Williams and Elizabeth D. Kirby (OpenStax).

Chapter Outline

  • 13.1 Foundational and contemporary theories of emotion.
  • 13.2 What category of feelings are considered as "the basic emotions"?
  • 13.3 What is the contribution of brain structures in emotional states?
  • 13.4 Mood and emotional disorders associated with depression.

Foundational and Contemporary Theories of Emotion

  • Factors underlying emotions include environmental context, bodily or physiological states, and brain systems. Theories differ based on how these factors interact.

James-Lange Theory

  • This is a "bottom-up" theory.
  • It requires autonomic specificity.
  • Process sequence: 1. External stimulus, 2. Perception, 3. Autonomic/physiological response, 4. Emotional reaction.
  • Key brain structures involved in the physiological-to-emotional loop: Thalamus, Hypothalamus, Amygdala, Hippocampus, Fornix, and Cingulate gyrus.

Cannon-Bard Theory

  • This is a "top-down" theory.
  • Process sequence: 1. External stimulus, 2. Perception, followed by a simultaneous 2. Emotional reaction and 2. Autonomic/physiological response.
  • Information is processed through the Thalamus and distributed to the emotional and physiological centers at the same time.

Schachter-Singer Theory (Two-Factor Theory)

  • Proposes that emotional interpretation of physiological reactions is the final step.
  • Process sequence: 1. External stimulus and Perception, 2. Autonomic/physiological response, 3. Emotional interpretation of the physiological reaction.
  • Research Study: Participants were given injections of saline (control) or epinephrine and watched either a happy or an angry actor. Participants not told about the drug's effects reported emotions matching the actor's behavior, showing they interpreted their physiological arousal based on the social context.
  • Comparison: In scenarios like a roller coaster ride or airplane turbulence, James-Lange predicts the same emotional reaction (fear due to arousal), whereas Schachter-Singer predicts different emotions based on how the context is interpreted (excitement vs. fear).

Appraisal-Based Theories

  • Similar to Schachter-Singer, emphasizing that emotional reactions are produced by subjective interpretation/appraisal of stimuli relative to personal variables.
  • Emphasizes "ongoing relationships with the environment."
  • Variables for appraisal include: novelty, expectedness, pleasantness, goal-orientation, fairness, control, certainty, morality, and self-concept relevance.

Constructionist Theory

  • Proposes that the brain actively constructs a prediction of experience by integrating sensory info with memories of past experiences.
  • Unlike other theories that view the brain as a passive converter of sensory info, this theory highlights the role of previous events in generating current emotions.

The Basic Emotions

Paul Ekman and Universal Emotions

  • Facial expressions for the following emotions are identified across widely varying cultures: Anger, Fear, Surprise, Sadness, Disgust, Happiness.

Body Maps and fMRI Evidence

  • Each basic emotion is associated with consistent changes in blood flow in specific parts of the body.
  • fMRI studies where participants identified scenes or word imagery showed specific brain signatures:
        - Increased Insula activity is linked to fear and disgust.
        - Increased Amygdala activity is linked to happiness, fear, and disgust.
        - Participants are highly accurate at categorizing emotional words and identifying movie scene emotions.

Expanding the Emotional Spectrum: Robert Plutchik

  • Proposed a wider range of emotions beyond the basic set.
  • Plutchik’s model suggests emotions result from combining 8 basic emotions with varying intensities, often visualized as a color wheel (Plutchik-wheel).

Contribution of Brain Structures in Emotional States

  • Brain systems are responsible for: 1. Registering internal arrays of external stimuli, 2. Generating physiological/behavioral responses, 3. Assigning interpretation and subjective emotion.

The Papez Circuit and Allostasis

  • Essential for allostasis: the regulation of changes within the internal environment to meet perceived and anticipated demands from the external environment.
  • Key structures: Thalamus, Hypothalamus, Amygdala, Hippocampus, Insula, Orbitofrontal cortex, and Anterior cingulate cortex (ACC).
  • Kluver-Bucy Syndrome: Caused by lesions to temporal lobes (amygdala, hippocampus, tracts). Symptoms include placidity (no fear/anger), loss of satiety (feeding-related emotional loss), visual and tactile agnosia, amnesia, and hypermetamorphosis (compulsive exploration).

Functional Roles of Specific Structures

  • Thalamus: Gateway for Information; handles exteroception (external stimuli) and interoception (internal state awareness).
  • Hypothalamus: Responsible for reflexive emotion, appetitive responses (energy), agonistic behaviors (defense/attack), and reproductive mating instincts. It coordinates allostasis by changing internal physiology.
  • Amygdala: Handles reflexive emotion and emotional learning. For example, while the hypothalamus triggers hunger at the smell of food, the amygdala triggers hunger at the sight of students lining up for the cafeteria. It is central to fear.
  • Urbach-Wiethe’s Disease: A rare autosomal recessive mutation of extracellular matrix protein 1. Causes progressive destruction of the amygdala. Patient SM showed no fear to snakes, spiders, or horror films and could not recognize fear in faces.
  • Insula Cortex: Appraises incoming sensory info (interoceptive and exteroceptive) from the Thalamus and S1 to assign subjective feelings. Connects to PFC and ACC to incorporate sensory input with cognitive resources.
  • Prefrontal Cortex (PFC):
        - Orbitofrontal (ventromedial) PFC: Uses memories and if/then scenarios (inputs from cingulate/hippocampus) to determine emotional responses and assign conceptual meaning to sensory signals.
        - Dorsolateral PFC: Handles emotion regulation, social rules, and continuous updates/corrections of ongoing emotional states.
  • Anterior Cingulate Cortex (ACC): Monitors internal physiology and directs adjustments. It assigns value (positive or negative) to actions and sends plans to motor areas.

Neuroscience Research: Modeling Fear and Anxiety

  • Fear Conditioning: A tone is paired with a foot shock. When the tone is played later in a new context, the mouse freezes.
  • Optogenetic Fear Conditioning: Auditory inputs to the lateral amygdala are optogenetically stimulated with Channelrhodopsin-2 (ChR2) and paired with a shock. Activating the same neurons later in a new context causes freezing behavior even without a shock.

Mood and Emotional Disorders: Depression

  • Symptoms: Reduced appetite, sex drive, and motivation; sleep disturbances; decreased sympathetic activity (hypothalamic). Cognitive symptoms include worrying, obsessive anxiety, sadness, hopelessness, and social withdrawal. Symptoms must last more than 2 weeks.

Pharmacological Treatments

  • These target monoamine neurotransmitters:
        - Monoamine oxidase inhibitors (MAOIs).
        - Tricyclic antidepressants.
        - Selective serotonin reuptake inhibitors (SSRIs) like Prozac (fluoxetine).
  • SSRI Mechanism: Serotonin is cleared by reuptake into the presynaptic terminal. SSRIs block this reuptake, increasing serotonin in the synapse and enhancing postsynaptic signaling.

Brain Circuitry and Intervention

  • Case Study: A suicide attempt by gunshot damaged the ventromedial PFC (VMPFC) in both hemispheres but spared the dorsolateral PFC (DLPFC). Studies suggest distinct PFC regions mediate resistance or vulnerability to depression.
  • Deep Brain Stimulation (DBS): Pioneer Dr. Helen Mayberg uses DBS in Area 25 for depression. Area 25 sits at the junction of major white matter bundle tracts below the cingulate cortex. DBS electrode placement is verified via X-ray.

Questions & Discussion

  • Q: Public speaking causes sympathetic activity in everyone, but experienced speakers feel less distress. Which theory explains this?
      - A: Modern appraisal-based theories (or Schachter-Singer, depending on emphasis on personal variables/interpretation).
  • Q: People from different cultures are shown pictures of core emotions. Which will they recognize?
      - A: Happiness, Sadness, Disgust (All of the basic emotions).
  • Q: If you use optogenetics to inhibit the amygdala during fear conditioning training, what happens the next day?
      - A: The animal would not show freezing to the tone but would still freeze in response to the shock (as the shock is the direct stimulus, but the association was never formed).
  • Q: Dr. Farnsworth wants to target an area other than Area 25 with DBS to treat depression. Which makes the most sense?
      - A: Dorsolateral prefrontal cortex (due to its role in regulation and cognitive functioning).