Emotion (neuro)

Question 1

What is emotion?

Answer 1

- Emotional expression
• Animal and human studies
- Emotional experience
• Human studies
- Affective Neuroscience
•  neural basis of emotion and mood
• (mood as an emotion extended in time)

Question 2

Drug influence

Answer 2

• increase of anxiety-like behaviour following long-term opioid abstinence
• increase in depressive-like behaviour following long term-opioid abstinence
• long-term morphine abstinence abolishes social preference

Question 3

Brain mechanisms of emotion

Answer 3

• Emotions:
  • Love, hate, disgust, joy, shame, envy, guilt, fear, anxiety, etc.
• Theories of emotion:
  • James- Lange:
• We experience emotions in response to physiological changes in our body
  • Cannon-Bard:
• We can experience emotions independently of emotional expression (dissociations)
• Emotions are produced when signals reach the thalamus either directly from sensory receptors or by descending cortical input

Question 4

James-Lange vs. Cannon- Bard

Answer 4

• The James–Lange theory: emotion experienced in response to physiological changes in body
• The Cannon–Bard theory: emotions occur independent of emotional expression - no correlation with physiological state

Question 5

Is there a brain system responsible

for Emotions?

Answer 5

- Broca’s Limbic lobe
• Limbus (latin) means border
• primitive cortical gyri that form a ring around the brain stem
- Broca’s limbic lobe includes
• the parahippocampal gyrus
• the cingulate gyrus
• the subcallosal gyrus

Question 6

The Limbic system

Answer 6

• Broca’s limbic lobe

• Areas of brain forming a ring around corpus callosum: cingulate gyrus, medial surface temporal lobe, hippocampus

Question 7

The Papez circuit

Answer 7

• Limbic structures, including cortex, involved in emotion
• Emotional system on the medial wall of the brain linking cortex with hypothalamus
• Cortex critical for emotional experience
• Hippocampus governs behavioral expression of emotion:
  • Rabies infection implicates hippocampus in emotion -> hyperemotional responses
• Anterior thalamus:
  • Lesions lead to spontaneous laughing or crying.
• Paul MacLean popularized the term limbic system:
  • Evolution of limbic system allows animals to experience and express emotions beyond stereotyped brain stem behaviors.

Question 8

Limbic system as we define it

Answer 8

• Cingulate gyrus
• Parahippocampal structures
• Septal nuclei
• Amygdala
• Enthorinal cortex
• Hippocampal complex:
  • dentate gyrus
  • CA1-CA4 subfields
  • subiculum
• Difficulties with the single emotion system
  concept
• Diversity of emotions and brain activity
• Many structures involved in emotion
  • No one-to-one relationship between structure and
  function
• Limbic system: use of single, discrete emotion
  system questionable

Question 9

Functions of limbic system

Answer 9

• Anatomically the limbic system appears to have a role in attaching a behavioral significance and response to a stimulus, especially with respect to its emotional content
• Damage to the limbic system leads to profound effects on the emotional responsiveness of the animal
• Cingulate gyrus:
  • role in complex motor control
  • pain perception
  • social interactions-mood
• Hippocampus proper and parahippocampal areas:
  • primary function in memory (critical role in
  connecting certain sensations and emotions to these memories)
• Amygdala:
  • involved in learning and storage of emotional
  aspects of experience

Question 10

Emotion theories and neural representations

Answer 10

• Early theories of emotion and limbic system
  built on introspection and inference from
  brain injury and disease.
• Studies of disease and consequences of
  lesions not ideal for revealing normal
  function.
• More recent theories of emotion
  • Basic emotion theories
  • Dimension emotion theories

Question 11

Amygdala

Answer 11

• Greek word for almond
• Critical structure for emotion in particular
  • fear and aggression, anxiety

Question 12

Human brain activity in response to emotional stimuli

Answer 12

• neutral and fearful faces were used as visual stimuli
• fearful faces produced greater activity in the amygdala than neutral faces
• no difference in amygdala activity occurred in response to happy/neutral faces

Question 13

Amygdala structure and connections

Answer 13

• Receives input from neocortex
  • All lobes, including hippocampal, and cingulate gyri
• Basolateral nuclei
  • Receives information from all sensory systems
• Corticomedial nuclei
• Central nuclei
• Output to hypothalamus (region involved in expression of emotion)
  • Stria terminalis
  • Ventral amygdalofugal pathway

Question 14

Amygdala fear

Answer 14

• The Kluver-Bucy syndrome (rhesus monkeys)
• Temporal lobe removal (temporal cortex, amygdala, hippocampus):
  • Good visual perception but poor visual recognition
  • psychic blindness
  • oral tendencies
  • emotional changes (reduced fear)
  • altered sexual behaviour
• Amygdalectomy (humans):
  • Reduce fear
  • Reduce Aggression
  • Hypersexuality
  • Oral tendencies
  • Reduce ability to recognize a fearful expression (can recognise happiness):
  • Flattened emotions
• Electrical stimulation:
  • Increased vigilance
  • Anxiety
  • Fear
  • Aggression

Question 15

Learned fear

Answer 15

• amygdala involved in forming memories of emotional and painful events
• confirmed by fMRI images and PET imaging

Question 16

Agression

Answer 16

• Multi facetted behaviour (kill for freedom, murderer,
  power, dominance)
• Endocrine mechanisms (testosterone, castration)
• Brain mechanisms
  Predatory aggression:
  • Attacks made against a member of a different
  species, to obtain food
  • No sympathetic activity
  Affective aggression:
  • For show, threatening posture
  • Social hierarchy
  • High levels of sympathetic activity: Amygdala important role in aggression related to social
  hierarchy

Question 17

Amygdala and aggression

Answer 17

- Surgery to reduce human aggression:
• Amygdalectomy
• Psychosurgery—now treatment of last resort
- Results:
• Reduced aggressive behavior
• Relief from anxiety
• Profound, unpleasant side effects
- Karl Pribram (rheusus monkeys, humans)
- Amygdala removal 
• Transformation from dominant to subordinate 
(social hierarchy, reduced agression)

Question 18

Neural Components of Anger and

Aggression Beyond the Amygdala

Answer 18

• The hypothalamus and aggression
  • Removal of cerebral hemispheres (cats) but not
  hypothalamus -> sham rage
  • Remove both cerebral hemispheres + anterior
  hypothalamus -> sham rage
• Also remove posterior hypothalamus -> No sham rage
• Electrical stimulation of hypothalamus leads to affective and predatory aggression

Question 19

Hypothalamus and aggression

Answer 19

Flynn’s research:

• Elicited affective aggression by stimulating medial hypothalamus
• Predatory aggression elicited by stimulating lateral hypothalamus

Question 20

Neural circuit for anger and aggression

Answer 20

• Two hypothalamic pathways to brain stem involving autonomic function:
  • Medial forebrain bundle -> ventral tegmental area; predatory aggression
  • Dorsal longitudinal fasciculus -> periaqueductal gray matter; affective aggression

Question 21

Serotonin and aggression (primates)

Answer 21

• Serotonin deficiency hypothesis
  • Aggression is inversely related to serotonergic activity.
• 5HT antagonist increase aggression
• Agonists of 5HT1A or 5HT1B decrease anxiety and aggressiveness
  • In humans also, reports of negative correlation between serotonin activity and aggression