PSYC10003 Lecture Notes - Lecture 10: Autonomic Nervous System, Adrenal Medulla, Cerebral Cortex
12 Jun 2018
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Lecture 10, Wednesday 23 March 2016
PSYC10003 - MIND, BRAIN & BEHAVIOUR 1
LECTURE 10
THE NEURAL BASIS OF EMOTION
THE CONCEPT OF EMOTION
•The concept of emotion has several different meanings. It is often used to refer to the positive or
negative feelings we experience in particular situations, such as happiness when we see a close
friend, or fearfulness when we are confronted by a wild dog. Emotion can also be used to refer to
the physiological or behavioural changes that accompany certain situations, such as an increase in
heart rate, rapid breathing, changes in posture or eye gaze, and so on.
•Feelings are strong motivators (factors that form the basis for action), and thus they exert an
influence on how we are likely to behave in particular situations. Emotional behaviours are likely
to have played an important part in the evolution of our central nervous system.
•Charles Darwin, in his 1872 publication The Expression of Emotion in Man and Animals,
suggested that particular, stereotyped responses tend to accompany similar emotional states in all
members of the same species. Thus, for example, in humans facial expressions tend to accompany
the same feelings of emotion in all individuals, regardless of culture.
•Darwin believed that expressions of emotion, like all other behaviours, evolve through the process
of natural selection. He suggested that expressions of emotion evolve from behaviours that
indicate what an animal is likely to do next (i.e., 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 though their original function may be lost.
•The idea behind Darwin’s proposition is that behaviours that originally served a function such as
fighting would evolve to become a display of the intention to fight, without actually being
enacted. In this way an elaborate threat display might evolve and obviate the need for real
fighting, which in turn would lead to fewer deaths within the species due to conflict. To be
effective, displays that convey intentions must be easily recognisable and readily distinguishable
from other emotional displays within the species.
EMOTIONS AS RESPONSE PATTERNS
•Emotional responses have three components:
•1. Behavioural – muscular changes that are appropriate to the situation that elicits them. For
example, a dog may seek to defend its territory in the face of an intruder by adopting an
aggressive posture (growling, ears forward, back and tail up, teeth bared). If this behavioural
display is sufficiently effective, the intruder may in turn adopt a submissive posture (ears back,
back and tail down). If it is not effective, the defending dog may run toward the intruder and
attack. Note that the displays of aggression and submission in this example are clearly
distinguishable by the opposite movements and postures (what Darwin called the principle of
antithesis).
•2. Autonomic – physiological changes induced by the autonomic nervous system facilitate the
behavioural responses. In the example of the dog defending its territory, activity of the
sympathetic branch of the autonomic nervous system increases whereas activity of the
parasympathetic branch decreases; the dog’s heart rate increases, and blood is diverted from the
digestive system to the muscles.
•3. Hormonal – these reinforce the autonomic changes. To continue the example, the dog’s
adrenal medulla secretes epinephrine and norepinephrine, which act to further increase blood flow
to the muscles and cause nutrients stored in the muscles to be converted into glucose.
NEURAL CONTROL OF EMOTIONAL RESPONSE PATTERNS
•In a series of ablation studies conducted in the 1920s, Bard found that cats who had had their
cerebral cortex surgically removed from both hemispheres (decortication) behaved in an
excessively aggressive manner in response to the slightest stimulation. A simple touch would make
the cats hiss, arch their backs, raise their fur and bare their teeth. Such behaviour is abnormal in !
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Lecture 10, Wednesday 23 March 2016
PSYC10003 - MIND, BRAIN & BEHAVIOUR 1
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two respects: first, it is particularly exaggerated, and second, it is not directed at an environmental
stimulus that would normally elicit such an emotional reaction.
•Bard called this behaviour following decortication sham rage. Crucially, when the surgical
removal of brain tissue also included the
hypothalamus, sham rage was no longer
elicited, which led Bard to conclude that the
hypothalamus is responsible for the
expression of aggressive behaviour, and that
the cortex normally inhibits and controls
such behaviour.
THE LIMBIC SYSTEM OF EMOTION
•The neuroanatomist James Papez
(pronounced ‘Payps’) in 1937 suggested that
a distinct circuit of brain structures
subserves emotional expression; this circuit
included the hypothalamus, anterior
thalamus, cingulate gyrus, fornix and
hippocampus. Some years later, in 1949,
Paul McLean coined the term the ‘Papez
circuit’, and he added the amygdala,
orbitofrontal cortex, and some nuclei of the basal ganglia.
He called this extended neural circuit the limbic system.
(The circuit borders the thalamus, and limbic means
‘border’.)
•The hippocampus formed the central element of McLean’s
limbic system (denoted here by a seahorse). It was believed
to receive inputs from the various senses, as well as from the
internal organs. Although the concept of the ‘limbic system’
is still used, it is now clear that it has several shortcomings,
including the fact that the hippocampus plays a much more
important role in learning and memory than in emotion.
KLUVER-BUCY SYNDROME & THE AMYGDALA
•In 1939 Klüver and Bucy described a syndrome in monkeys
that followed surgical removal of the anterior temporal
lobes. The monkeys ate virtually anything that was edible, showed increased sexual activity (often
directed at inappropriate objects), a tendency to explore all items with the mouth, and an absence
of fear.
•Monkeys that were previously difficult to handle became
completely tame after the surgery, showing no fear
whatsoever, even toward snakes, an animal that terrifies
most monkeys. It has been suggested that the Klüver-
Bucy syndrome arises from damage to the amygdala,
which is located in the anterior temporal lobe (and hence
was removed by the surgery).
•Klüver-Bucy syndrome is occasionally described in
humans. One such patient, described by Marlowe,
Mancall & Thomas (1985), became ‘flat’ and indifferent
to people and events after his brain damage (caused by an
infection). He would gaze for hours at the television, even
when it was turned off; he would imitate the actions of
others; he engaged in oral exploration of all objects
within his reach, lifting them to his mouth and sucking or !
Lecture 10, Wednesday 23 March 2016
PSYC10003 - MIND, BRAIN & BEHAVIOUR 1
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chewing on them. Despite being heterosexual prior to his illness, he made frequent sexual
advances toward other male patients.
STRUCTURE OF THE AMYGDALA
•It is now recognised that the amygdala plays a key role in the physiological and behavioural
reactions to objects and situations that have particular biological significance (e.g., those that are
likely to be painful, those that signify the presence of food or water, or the presence of a potential
mate or rival).
•The amygdala (or more accurately, the amygdaloid complex) is located in the anterior temporal
lobe, and consists of several nuclei with different functions:!
Medial nucleus – receives sensory input (including information from the olfactory system
concerning odours and pheromones) and relays information to the basal forebrain and
hypothalamus.
•Lateral/basolateral nuclei – receive sensory information from the primary sensory cortex,
association cortex, thalamus and hippocampus. They send axons to parts of the basal ganglia,
thalamus, and the central nucleus of the amygdala.
•Central nucleus – sends axons to regions of the hypothalamus, midbrain, pons and medulla that
are responsible for the expression of various emotional responses.
•Basal nucleus – receives axons from the lateral and basolateral nuclei and sends axons to other
amygdaloid nuclei and to the midbrain.
•The central nucleus is the most important part of the brain for the expression of emotional
responses to aversive or threatening stimuli. Damage to the central nucleus abolishes fear
responses to stimuli that have been associated with aversive events. By contrast, electrical
stimulation of the central nucleus induces a reaction of fear or agitation.
•Some of the effects of anxiolytic (anxiety-reducing) drugs are produced through the central
nucleus of the amygdala. The central nucleus contains a high concentration of opiate receptors. It
seems that some anxiety disorders may be due to overactivity of the central nucleus.
PHINEAS GAGE
•You will recall from Lecture 1 the case of Phineas Gage, and the personality changes that
occurred after damage to his frontal lobes. Here are the key details of the Gage case, as outlined
originally in Lecture 1:
•Phineas Gage was using a tamping iron to lay charges in rock, which was being blasted in order
to create a cutting for a railroad track. While tamping a charge into the rock the tamping iron
created a spark that ignited the gunpowder and sent the tamping iron shooting up from the hole
and into Phineas’ head. Phineas sustained extensive damage to the frontal lobes, but survived the
accident and lived for several years thereafter.
•Some months after the accident, probably in about the middle of 1849, Phineas felt strong enough
to resume work. But because his personality had changed so much, the contractors who had
employed him would not give him his place again. Before the accident he had been their most
capable and efficient foreman, one with a well-balanced mind, and who was looked on as a
shrewd smart business man. He was now fitful, irreverent, and grossly profane, showing little
deference for his fellows. He was also impatient and obstinate, yet capricious
and vacillating, unable to settle on any of the plans he devised for future
action. His friends said he was “No longer Gage.”
•It might be argued that many aspects of Phineas’ personality change are
attributable to alterations in his emotional reactions to people and situations
in everyday life.
CONSEQUENCES OF PREFRONTAL LEUCOTOMY
•You will also recall from Lecture 1 that frontal leucotomy was developed as a
treatment for psychiatric disorders, particularly those in which anxiety is a
prominent symptom.
•As outlined in that lecture, the long-term effects of the frontal leucotomy !
Document Summary
The concept of emotion: the concept of emotion has several different meanings. It is often used to refer to the positive or negative feelings we experience in particular situations, such as happiness when we see a close friend, or fearfulness when we are confronted by a wild dog. Thus, for example, in humans facial expressions tend to accompany the same feelings of emotion in all individuals, regardless of culture: darwin believed that expressions of emotion, like all other behaviours, evolve through the process of natural selection. In this way an elaborate threat display might evolve and obviate the need for real fighting, which in turn would lead to fewer deaths within the species due to conflict. To be effective, displays that convey intentions must be easily recognisable and readily distinguishable from other emotional displays within the species. Emotions as response patterns: emotional responses have three components, 1. Behavioural muscular changes that are appropriate to the situation that elicits them.
