PSYC10003 Lecture Notes - Lecture 10: Papez Circuit, James Papez, Orbitofrontal Cortex
10. Neural Basis of Emotion
The Concept of Emotion
• Concept of emotion has several different meanings
• Often used to refer to positive/negative feelings experienced in particular situations
• Can also be used to refer to physiological or behavioural changes accompanying certain situations
o ↑ heat ate, apid eathig, hages i i postue/ee gaze, etc.
• feelings are strong motivators (factors that form the basis for action)
o ∴ exert influence on how we are likely to behave in particular situations
o emotional behaviours likely play important part in evolution of CNS
• Charles Darwin, 1872, The Expression of Emotion in Man and Animals, suggest that particular
stereotyped responses tend to accompany similar emotional states in all members of species
o Eg. Human facial expressions tend to accompany same feelings of emotions in all individuals,
regardless of culture
o Believed expressions of emotion, like all other behaviours evolve through the process of
natural selection
o Suggested expressions of emotion evolve from behaviours that indicate what an animal is
likely to do next (ie behaviours that have predictive value), and that if these expressions are
of benefit to the animal they may evolve in ways that enhance their communicative value
even through their original function may be lost
o Idea ehid Dais popositio: ehaious that oiginally served a function such as fighting
would evolve to become a display of the intention to fight, without actually being enacted
o This way an elaborate threat display might evolve and obviate the needed for real fighting,
which in turn would lead to fewer deaths within the species due to conflict
o To be effective: displays that convey intentions must be easily recognisable and readily
distinguishable from other emotional displays within species
Emotions as Response Patterns
Emotional response have three components:
1. Behavioural – muscular changes that are appropriate to situation that
elicits them
a. eg. Dog wanting to defend territory may adopt aggressive
posture, if effective, intruder may adopt submissive posture
b. note: displays of aggression and submission in this example are
clearly distinguishable by opposite movements and posture
(what Darwin called the principle of antithesis)
2. Autonomic – physiological changes induced by ANS facilitate the
behavioural responses
a. Eg. In dog defending territory, activity of SNS increases whereas
aeas of P“N“ deeases; heat ate ↑, lood dieted fo
digestive system to muscles
3. Hormonal – reinforce autonomic changes
a. Dogs adeal edulla seetes epiephie ad oepiephie → at to futhe iease
blood flow to muscles and cause nutrients stored into muscles to be converted to glucose
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2
Neural Control of Emotional Response Patterns
• “eies of alatio studies i s
o Bard found cats who had cerebral cortex surgically removed from both hemispheres
(decortication) behaved in excessively aggressive manner in response to slightest
stimulation
o Simple tough would make them hiss, arch back, etc.
o Such behavior is abnormal in two ways:
▪ Particularly exaggerated
▪ Not directed at an environmental stimulus that would normally elicit reaction
• Called this behavior sham rage
o When surgical removal of brain tissue also included hypothalamus, no sham rage
o Bard concluded hypothalamus responsible for expression of aggressive behavior & cortex
normally inhibits and controls behavior
Limbic System of Emotion
• Neuroanatomist, James Papez, 1937 suggested that a distinct circuit of brain structures subserves
emotional expression including:
o Hypothalamus
o Anterior thalamus
o Cingulate gyrus
o Fornix
o Hippocampus
• 1949, Paul McLean coined the te, Papez
iuit ad added:
o amygdala
o orbitofrontal cortex
o some nuclei of basal ganglia
o called this extended neural circuit in
limbic system, circuit borders thalamus,
limbic = border
• Hippoapus foed the etal eleet of MLeas lii sste
• Believed to receive inputs from various senses and internal organs
• Coept of lii sste still used ut has a fe dofalls:
o Fact that hippocampus plays more important role on learning & memory than emotion
Limbic System of Emotion
• 1939, Kluver and Bucy described syndrome in monkeys after surgical removal of anterior temporal
lobes
• ate virtually anything edible, ↑ sexual activity (often at inappropriate objects), tendency to explore
all things with mouth, absence of fear
• monkeys prev. difficult to handle became tame after surgery, showing no fear at all, even towards
snakes suggested that the Kluver-Bucy syndrome arises from damage to amygdala in anterior
temporal lobe
• occasionally described in humans
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• patient described by Marlowe, Mancall & Thomas (1985), eae flat ad idiffeet to people
and events after brain damage (caused by infection)
• gaze for hours at TV even when turned off
• imitate actions of others
• engaged in oral exploration of all objects within reach; sucking or chewing
• was heterosexual but made sexual advances to other male patients afterwards
Structure of the Amygdala
• plays key role in physiological and behavioural reactions to objects and situations that have
particular biological significance (likely to be painful, those that signify presence of food/water,
presence of potential mate or rival)
• amygdala (or, amygdaloid complex) is in anterior temporal lobe, consists of several nuclei with
different functions:
o medial nucleus – receives sensory input (incl. From olfactory system concerning odours and
pheromones) and relays info to basal forebrain and hypothalamus
o lateral/basolateral nuclei – receive sensory info from primary sensory motor cortex,
association cortex, thalamus and hippocampus. Send axons to parts of basa ganglia,
thalamus and central nucleus of amygdala
o central nucleus – sends axons to regions of hypothalamus, midbrain, pons and medulla that
are responsible for expression of various emotional responses
o basal nucleus – receives axons from lateral and basolateral nuclei and sends axons to other
amygdaloid nuclei and to the midbrain
• central nucleus most important part of brain for expression of emotional responses to aversive or
threatening stimuli
• damage to central nucleus abolishes fear responses to stimuli associated with aversive events
• contrastingly, electrical stimulation of central nucleus induces reaction of fear or agitation
• some effects of anxiolytic (anxiety-reducing) drugs are produced through central nucleus of the
amygdala
• central nucleus contains high concentration of opiate receptors
• seems some anxiety disorders may be due to overactivity of central nucleus
Phineas Gage
• oths afte aidet ≈ iddle of 4, felt stog eough to esue ok
• personality changed so much, previous employers would not give his place again
• pre-accident: most capable and efficient foreman, with well-balanced man and shrewd, smart
businessman
• post-accident: fitful, irreverent, grossly profane, show little deference for fellows, impatient,
stubborn, capricious and vacillating, unable to settle on any plans he devised
• No loge Gage
• agued Phieas pesoalit hage ae attiutale to alteatios i his eotioal eatios to
people and situations in everyday life
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Document Summary
From olfactory system concerning odours and pheromones) and relays info to basal forebrain and hypothalamus: lateral/basolateral nuclei receive sensory info from primary sensory motor cortex, association cortex, thalamus and hippocampus. Consequences of prefrontal leucotomy: only later it became clear that it was of little therapeutic value and had many side effects, apathy (lack of motivation, emotional unresponsiveness, disinhibition (lack of self-control, lack of foresight, inability to plan. Orbitofrontal cortex and decision making: orbitofrontal cortex located on ventral surface (underside) of frontal lobes, immediately above orbits that contain eyes, more medial region known as ventromedial prefrontal cortex, more lateral region called lateral-orbital prefrontal cortex. Independently suggested similar explanations for feelings associated with emotions. Some will love it, other will hate it. We may also love the experience one time and hate it the next, depending on how we react to physiological responses it arouses. The orbitofrontal cortex and the somatic marker hypothesis.
