Emotion

1
Emotion

• Expression Experience

2
What is emotion?

• No scientific definition
• Controlled by distinct neuronal circuits within
  the brain
• We experience emotion consciously
• therefore there is a cognitive element, most
  likely involving the cerebral cortex
• Emotion can be viewed as an outcome of the
  interaction of peripheral central factors

3
Responses to Emotion

• Emotion is accompanied by autonomic, endocrine
  skeletomotor responses
• Thus it also depends on sub-cortical parts,
  including
• amygdala
• hypothalamus
• brain stem

4
Peripheral Responses

• Peripheral responses prepare the body for action
• Communicate emotions to other people
• Example fear
• increased heart rate respiration
• dry mouth
• tense muscles
• sweaty palms

5
The Autonomic Nervous System Emotion

• Most changes that accompany emotional states are
  mediated by autonomic nervous system
• The autonomic system is primarily an effector
  system
• controls smooth muscles, heart, exocrine glands
• autonomic is involuntary

6
Three Divisions of the ANS

• Sympathetic
• governs fight or flight response
• response to stress
• Parasympathetic
• rest and digest
• Normal conditions
• Enteric

7
(No Transcript)
8
Role of the Hypothalamus

• Contains many of the neuronal circuits that
  regulate functions that vary with emotion
• Temperature
• heart rate
• blood pressure
• water and food intake
• also controls pituitary gland thereby the
  endocrine system
• controls output of autonomic nervous system
•  

9
Hypothalamic Control of the ANS

• The hypothalamus acts on ANS in 2 ways
• Projects to 3 important regions in the brain stem
  spinal cord
• to the nucleus of the solitary tract
• receives sensory input from viscera
• to the brain stem in the rostral ventral medulla
• leads to general sympathetic activation
• directly to the autonomic outflow of the spinal
  cord
• The hypothalamus acts on endocrine system to
  release hormones that influence autonomic
  function

10
(No Transcript)
11
Experimental Evidence

• Emotional states are elicited by stimulating the
  hypothalamus
• Stephen Ranson - 1932
• stimulated different regions of the hypothalamus
  in anesthetized animals
• Evoked autonomic reactions including changes of
  heart rate, blood pressure, etc.
• Walter Hess - 1940s
• used awake animals
• produced behaviors and physiologic changes
  characteristic of particular emotions e.g. fear

12
Cortical Centers of Emotion

• Physiological inputs to the hypothalamus act on
  the brain stem autonomic nervous system.
• This information reaches the cerebral cortex from
  the peripheral organs.
• This gives rise to the conscious perception of
  emotion
• So where is the cortical representation of
  emotion?

13
The Limbic System Concept

• Is there a system ( a group of structures that
  function together) responsible for emotion?
• Scientists identified the limbic system as the
  key pathway in emotion 1930s
• Paul Broca
• James Papez

14
Brocas Limbic Lobe

• Paul Broca 1878
• Identified a portion of cortex present in all
  mammals which is different from surrounding
  cortical tissue
• These areas form a ring or border around the
  brainstem
• Limbus border , thus limbic lobe
• Includes
• cortex around the corpus callosum, especially in
  the cingulate gyrus
• Cortex on the medial surface of the temporal
  lobe, including the hippocampus
• Broca did not relate these structures to emotion

15
(No Transcript)
16
The Papez Circuit

• James Papez- 1930s
• Proposed that there is an emotion system that
  links the cortex to the hypothalamus
• Emotion is determined by the activity of the
  cingualte cortex
• Emotional expression is governed by the
  hypothalamus
• The Papez Circuit
• A group of structures, each connected to the next
  by a major fiber tract
• The cingulate cortex projects to the hippocampus,
  which projects to the hypothalamus through the
  fornix the hypothalamus projects to the anterior
  nuclei of the thalamus, which reach back to the
  cortex

17
Papez Circuit
18
Studying Emotion

• Emotional expression
• behavioral manifestations of internal emotion
• Emotional experience
• subjective feelings of emotion
• Limitations of animal models
• can study emotional expression but cannot
  investigate emotional experience
• Limitations of human experiments
• very often the medical situation which provides
  information involves damage to or compromise of
  other neural structures and functions in an
  uncontrolled way

19
Theories of Emotion- James Lange

• William James Karl Lange - 1884
• Proposed that the experience we call emotion
  occurs after the cortex receives signals about
  physiologic changes
• Emotional expression precedes emotional
  experience
• Physiological changes occur in response to
  stimuli, then we feel emotions
• Emotion is the consequence of information from
  the periphery
• We feel sorry because we cry
• The physiological changes are the emotion

20
Critique of James Lange

• Emotions are experienced even if physiological
  changes arent sensed
• Patients animals with transected spinal cords
  do not have lessened emotions
• The same physiological changes accompany
  different emotions and can have other causes
• e.g. fear, anger disease can all increase heart
  rate cause sweating

21
Theories of Emotion Cannon Bard

• Walter Cannon and Phillip Bard - 1927
• Stimuli cause emotional experience
• Emotional experience can occur independently of
  emotional expression
• The thalamus plays a pivotal role in emotional
  sensations
• Emotions are produced when signals reach the
  thalamus directly from sensory receptors or by
  descending cortical input
• The emotion is determined by the pattern of
  activation of the thalamus

22
The Somatic Marker Hypothesis

• Stanley Schacter
• The cortex constructs emotion out of signals
  received from the periphery
• This is called the somatic marker hypothesis
• Emotion is a story the brain concocts to explain
  bodily reactions
• Depends expectations, experience, social context
• Thus the same responses can accompany different
  emotions

23
Current Theories

• Antonio Damasio -
• Expanded somatic marker hypothesis
• Draws a close connection between emotion and
  cognition.
• Emotions are biologically indispensable to
  decisions.
• Studied patients with damage to the amygdala or
  prefrontal cortex
• Research on patients with frontal lobe damage
  indicates that feelings normally accompany
  response options
• Operate as a biasing device to dictate choice.
• Descartes error separating mind body

24
The Current View

• No single neural system produces emotions
• Different emotions may depend on different neural
  circuits, but many of these circuits converge in
  the same parts of the brain
• The limbic system may be involved in some
  emotional experiences, but it is not the sole
  neural system underlying emotion
• Feelings (emotion) result from the interplay
  between
• The amygdala, hypothalamus, brain stem
  autonomic nervous system and . . .
• between amygdala and frontal limbic cortex

25
Fear Anxiety

• The amygdala is the critical structure
• Also involves the hypothalamus ANS
• Demonstrated by
• Kluver-Bucy Syndrome
• Electrical stimulation experiments
• Patients with damage to the amygdala

26
Klüver-Bucy Syndrome

• Heinrich Kluver Paul Bucy - 1939
• bilateral removal of the temporal lobes in
  monkeys (which contains the amygdala
  hippocampal formation) ?
• Radical changes in emotional behavior
• increased and bizarre sexual behavior
• highly oral
• failed to recognize familiar objects (psychic
  blindness)
• temporal lobe destruction of visual cortices
• emotionally flat
• absence of fear - amygdala missing

27
Kluver-Bucy Syndrome
28
The Amygdala

• Structure critical to emotional part of
  Kluver-Bucy syndrome is the amygdala
• The amygdala is part of the limbic system
• Human patients with damaged amygdalas have
  reduced ability to recognize fear in others
• Electrical stimulation leads to fear and anxiety
• A learned fear response, where pain is associated
  with a sensory input, may involve a circuit
  through the basolateral nuclei central nucleus
  of the amygdala
• These effects are mediated through the
  hypothalamus autonomic nervous system.

29
The Amygdala
30
Anger and Aggression

• Definitions
• Predatory aggression
• leads to an attack for food
• motive is to kill other animal
• Affective aggression
• behavior for show to scare other animal
• lots of sympathetic ANS activity
• Mediated by the hypothalamus, midbrain amygdala
• May also involve serotonin

31
The Role of the Hypothalamus

• When the entire cerebral hemispheres are removed,
  sham rage results
• Small stimuli provoke violent responses
• Difficult to interpret because the entire
  neocortex is missing
• Removal of anterior hypothalamus, sham rage still
  occurs
• Removal of the posterior hypothalamus, sham rage
  vanishes
• Conclusion posterior hypothalamus is important
  for aggression and is normally inhibited by
  neocortex
• Electrical stimulation of the hypothalamus
• Stimulation of medial hypothalamus leads to
  affective aggression - hiss and spit at mouse
• Stimulation of lateral hypothalamus leads to
  predatory aggression

32
Possible Role of the Midbrain

• Major outputs of hypothalamus to brain stem are
• Medial forebrain bundle (mfb)
• project to ventral tegmental area
• Electrical stimulation of ventral tegmental area
  can cause predatory aggression
• Lesions in ventral tegmental area can abolish
  affective aggression
• Dorsal longitudinal fasciculus (dlf)
• project to periaqueductal gray matter
• Electrical stimulation of PAG can elicit
  affective aggression and lesions can abolish
  affective aggression

33
Possible Role of the Amygdala

• Ablation experiments indicate that the amygdala
  is also involved in aggression
• amygdalectomy reduces aggression
• Two pathways for aggression
• Predatory aggression - cortex amygdala
  lateral hypothalamus mfb ventral tegmental
  area
• Affective aggression - cortex amygdala medial
  hypothalamus dlf periaqueductal gray matter
• Led to psychosurgical procedures to destroy
  amygdala in humans
• Frontal lobotomy is another example of
  psychosurgery

34
Possible Role of Serotonin

• Experimental evidence suggests that blocking or
  reducing the synthesis or release of serotonin
  may increase aggressive behavior
• When the gene for serotonin receptors are removed
  in mice, they become more aggressive
• The type of receptor that is most effective when
  deleted is normally found in the amygdala,
  periaqueductal gray matter, and basal ganglia, as
  well as the raphe nuclei

35
Summary

• No single neural system produces emotions
• Brain structures involved in emotion are multi
  functional
• there are interesting relationships among
  emotion, memory, and olfaction
• Emotion results from the interplay between
• The amygdala, hypothalamus, brain stem
  autonomic nervous system and . . .
• between amygdala and frontal limbic cortex