Limbic System & Physiology of Emotion

Question 1

Characteristics of the “Great Limbic Lobe”

Answer 1

• group of nuclei @ medial surface of brain; right underneath cortex
• important structures:
  
  • medial and lateral olfactory stria ==> form a V-shape
    
    • cortex w/in the “V” = cingulate pole ==> cingulate gyrus
    • cingulate gyrus continues around corpus collosum, eventually ==> parahippocampus ==> hippocampus
  • anterior perforated substance = behind olfactory stria
    
    • ventrial striatium/pallidum abut pial surface
    • diagonal band of broca = part of ant. perforated subtance = extends from amygdala ==> curves into interhemispheric fissure
      
      • contains populations of cholinergic nuclei

Question 2

Structures w/in Papez Circuit

Answer 2

• hypothalamus + mamillary bodies
• anterior thalamic nucleus
• cingulate gyrus
• hippocampus

Question 3

Papez hypothesis about limbic system

Answer 3

• cortical operation ==> cingulate gyrus = primary center of experience of emotion
• cingulate ==> hippocampus ==fornix==> hypothalamus = center for expression of emotion (e.g. HR changes, sweating, etc/)
• hypothalamic expression feeds back to cingulate/cortex via mamillothalamic tract ==> anterior thalamic nuclei

Question 4

Subsequent research on the “limbic system”

Answer 4

• limbic system = commonly used, but controversial term without clear definition or definitive understanding
• further research has shon that “Papez circuit” has different roles:
  
  • hippocampus = more memory involvement
• structures not identified by Papez that have roles in emotion
  
  • ventral-medial frontal lobe (“oribtofrontal cortex”)
  • amygdala
  • ventral striatum
  • dopaminergic neurons of ventral tegmental area

Question 5

Cognition definition

Answer 5

• faculty for processing of information, applying knowledge, and changing preferences
• includes:
  
  • memory
  • attention
  • language
  • problem solving
  • planning

Question 6

Emotion definition

Answer 6

• psychophysiologic experience of an individual’s state of mind as interacting with biochemical and environmental influences
• involves “physiologic arousal, expressive behaviors, and conscious experience”
• associated w/mood, temperament, personality, motivation
  
  • physiology of emotion and physiology of motor system (==>certain behaviors/movements)

Question 7

Mood definition

Answer 7

• “affective state” (like emotion)
• emotion = clear focus vs. mood = unfocus and diffuse
• mood = tone and intensity + structured set of predicitions about future experience of reward or punishment

Question 8

Affect definition

Answer 8

• experience of feeling or emotion
  
  • part of the process of an organism’s interaction with stimuli
• affect display = facial, vocal, or gestural behavior that serves as an indicator of affect
• “external and dynamic manifestation of a person’s internal emotional state”

Question 9

Personality definition

Answer 9

• characteristics patterns of thoughts, feelings and behaviors exhibited by a person fairly consistently throughout life
• personality types = psychologic classifications of individuals vs. personality traits = smaller behavioral groupings applied to individuals

Question 10

Aygdala role in emotion/decision-making

Answer 10

• primary roles: formation and storage of memories associated w/emotional events
  
  • role in creating associations between sensory stimuli and specific behavioral/autonomic responses (e.g. fear-conditioning experiments)
  • both aversive and appetitive conditioning
• sensory stimuli ==> lateral nuclei ==> associations w/memories of stimuli mediated by long-term potentiation
• lateral nuclei ==> central nuclei + bed nuclei of stria terminalis (BNST) ==> elicit fear behavior

Question 11

Role of central nucleus of amygdala in emotion/decision-making

Answer 11

• elicts/mediates fear behavior in response to stimulation by lateral nuclei
• fear behaviors:
  
  • (via central gray) freezing (immobility)
  • (via hypothalamus) tachycardia
  • increased respiration
  • BNST (part of central nucleus) ==> Corticotropin-releasing hormone release from pituitary ==> stress-hormone (epinephrine and cortisol) release @ adrenal gland

Question 12

Orbitofrontal (ventromedial prefrontal) cortex role in emotion/decision-making

Answer 12

• involved in anticipatory emotional response to impending punishment (but not registration of actual consequences
• e.g. Iowa gambling task
  
  • pt.s w/lesions @ orbitofrontal lack aversion/emotional response to “bad decks” (that lose them money)
• ==> pt.s demonstrate inadequate inhibition of aggression, sexual behavior, anxiety, and appetitive fxns + fail to correctly employ these behaviors in appropriate circustances

Question 13

Ventral striatum & dopamine role in emotion/decision-making

Answer 13

• important reinforcing zone = medial forebrain bundle = dopaminergic neurons @ ventral tegmental area (VTA) ==> nucleus accumbens @ ventral striatum
• VTA neurons ==> nucleus accumbes <==> VMPFC
  
  • these connections represent a corticostriatial network that (via dopamine), can reinforce or reduce predictions about risks/rewards of a given behavior
  • excessive dopamine ==> excessive reinforcement = hallmark of addiction
• dopamine is used in brian to “update the value” attached to different actions and stimuli