Emotions

biology

The Amygdala
And its role in emotions
Animals with damaged amygdalas cannot develop conditioned fear responses. People with damaged amygdalas cant
recognize fear in other people, though they may be able to experience fear themselves.

sympathetic nervous system, which prepares the body for action, the parasympathetic nervous system keeps the body still.

The galvanic skin response is an increase in the skins rate of electrical conductivity, which occurs when subjects sweat during
emotional states. Researchers also use indicators such as blood pressure, muscle tension, heart rate, and respiration rate to
measure emotion.

The psychologist Paul Ekman and his colleagues have identified six basic emotions: happiness, sadness, anger, fear, surprise,
and disgust. Worldwide, most people can identify the facial expressions that correspond to these emotions.

Ekman's famous test of emotion recognition was the Pictures of Facial Affect (POFA) stimulus set published in 1976. Consisting
of 110 black and white images of Caucasian actors portraying the six universal emotions plus neutral expressions, the POFA
has been used to study emotion recognition rates in normal and psychiatric populations around the world.

The Catharsis Hypothesis
The catharsis hypothesis suggests that anger can be decreased by releasing it through aggressive actions or fantasies.
However, although catharsis helps in some cases, researchers have generally found that catharsis does not decrease anger in
the long term. In fact, aggressive actions or fantasies can sometimes increase anger.
The Facial-Feedback Hypothesis
Some researchers have proposed that the brain uses feedback from facial muscles to recognize emotions that are being
experienced. This idea is known as the facial-feedback hypothesis. It follows from this hypothesis that making the facial

expression corresponding to a particular emotion can make a person feel that emotion. Studies have shown that this
phenomenon does indeed occur.

The limbic system is a group of structures in the brain associated with emotions and drives. It is made up of four main
structures: the amygdala, the hippocampus, regions of the limbic cortex, and the septal area. These structures form
connections between the limbic system and the hypothalamus, thalamus, and cerebral cortex. The hippocampus is important
in memory and learning, while the limbic system itself is central in the control of emotional responses.

The limbic system is associated with a number of functions including the sense of smell, behavior, learning, long-term
memory, emotions, and drives. The word limbic comes from the Latin word limbus, which roughly means "belt" or "border."
This system is shaped somewhat like a doughnut and forms an inner border to the cortex.
The limbic system influences other systems including the autonomic nervous system and the endocrine system. It is also linked
to the prefrontal cortext and the brain's pleasure center.
he hippocampus is a small, curved formation in the brain that plays an important role in the limbic system. The hippocampus is
involved in the formation of new memories and is also associated with learning and emotions.
Because of brain symmetry, the hippocampus is found in both hemispheres of the brain. When both sides of the hippocampus
are damaged, the ability to create new memories can be impeded.

The Emotional Nervous System

Dr. C. George Boeree

Emotion involves the entire nervous system, of course. But there are two parts of the nervous system that are especially
significant: The limbic system and the autonomic nervous system.
The Limbic System
The limbic system is a complex set of structures that lies on both sides of the thalamus, just under the cerebrum. It includes
the hypothalamus, the hippocampus, the amygdala, and several other nearby areas. It appears to be primarily responsible for

our emotional life, and has a lot to do with the formation of memories. In this drawing, you are looking at the brain cut in half,
but with the brain stem intact. The part of the limbic system shown is that which is along the left side of the thalamus
(hippocampus and amygdala) and just under the front of the thalamus (hypothalamus):

Hypothalamus
The hypothalamus is a small part of the brain located just below the thalamus on both sides of the third ventricle. (The
ventricles are areas within the cerebrum that are filled with cerebrospinal fluid, and connect to the fluid in the spine.) It sits
just inside the two tracts of the optic nerve, and just above (and intimately connected with) the pituitary gland.
The hypothalamus is one of the busiest parts of the brain, and is mainly concerned with homeostasis. Homeostasis is the
process of returning something to some set point. It works like a thermostat: When your room gets too cold, the
thermostat conveys that information to the furnace and turns it on. As your room warms up and the temperature gets
beyond a certain point, it sends a signal that tells the furnace to turn off.
The hypothalamus is responsible for regulating your hunger, thirst, response to pain, levels of pleasure, sexual satisfaction,
anger and aggressive behavior, and more. It also regulates the functioning of the autonomic nervous system (see below),
which in turn means it regulates things like pulse, blood pressure, breathing, and arousal in response to emotional
circumstances.
The hypothalamus receives inputs from a number of sources. From the vagus nerve, it gets information about blood pressure
and the distension of the gut (that is, how full your stomach is). From the reticular formation in the brainstem, it gets
information about skin temperature. From the optic nerve, it gets information about light and darkness. From unusual
neurons lining the ventricles, it gets information about the contents of the cerebrospinal fluid, including toxins that lead to
vomiting. And from the other parts of the limbic system and the olfactory (smell) nerves, it gets information that helps
regulate eating and sexuality. The hypothalamus also has some receptors of its own, that provide information about ion
balance and temperature of the blood.
In one of the more recent discoveries, it seems that there is a protein called leptin which is released by fat cells when we
overeat. The hypothalamus apparently senses the levels of leptin in the bloodstream and responds by decreasing appetite. It
would seem that some people have a mutation in a gene which produces leptin, and their bodies cant tell the hypothalamus
that they have had enough to eat. However, many overweight people do not have this mutation, so there is still a lot of
research to do!
The hypothalamus sends instructions to the rest of the body in two ways. The first is to the autonomic nervous system. This
allows the hypothalamus to have ultimate control of things like blood pressure, heartrate, breathing, digestion, sweating, and
all the sympathetic and parasympathetic functions.

The other way the hypothalamus controls things is via the pituitary gland. It is neurally and chemically connected to the
pituitary, which in turn pumps hormones called releasing factors into the bloodstream. As you know, the pituitary is the so-
called master gland, and these hormones are vitally important in regulating growth and metabolism.
Hippocampus
The hippocampus consists of two horns that curve back from the amygdala. It appears to be very important in converting
things that are in your mind at the moment (in short-term memory) into things that you will remember for the long run
(long-term memory). If the hippocampus is damaged, a person cannot build new memories, and lives instead in a strange
world where everything they experience just fades away, even while older memories from the time before the damage are
untouched! This very unfortunate situation is fairly accurately portrayed in the wonderful movie Memento, as well as in a
more light-hearted movie, 50 First Dates. But there is nothing light-hearted about it: Most people who suffer from this kind
of brain damage end up institutionalized.
Amygdala
The amygdalas are two almond-shaped masses of neurons on either side of the thalamus at the lower end of the
hippocampus. When it is stimulated electrically, animals respond with aggression. And if the amygdala is removed, animals
get very tame and no longer respond to things that would have caused rage before. But there is more to it than just
anger: When removed, animals also become indifferent to stimuli that would have otherwise have caused fear and even
sexual responses.
Related areas
Besides the hypothalamus, hippocampus, and amygdala, there are other areas in the structures near to the limbic system that
are intimately connected to it:
The cingulate gyrus is the part of the cerebrum that lies closest to the limbic system, just above the corpus collosum. It
provides a pathway from the thalamus to the hippocampus, seems to be responsible for focusing attention on emotionally
significant events, and for associating memories to smells and to pain.
The ventral tegmental area of the brain stem (just below the thalamus) consists of dopamine pathways that seem to be
responsible for pleasure. People with damage here tend to have difficulty getting pleasure in life, and often turn to alcohol,
drugs, sweets, and gambling.

The basal ganglia (including the caudate nucleus, the putamen, the globus pallidus, and the substantia nigra) lie over and to
the sides of the limbic system, and are tightly connected with the cortex above them. They are responsible for repetitive
behaviors, reward experiences, and focusing attention. If you are interested in learning more about the basal ganglia,

Dr. C. George Boere

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above$the$limbic$system,$but$below$the$cingulate$gyrus$and$within$the$temporal$lobes.$$Although$
glutamate$is$the$most$common$neurotransmitter$here$as$everywhere$in$the$brain,$the$inhibitory$
neurotransmitter$GABA$plays$the$most$important$role$in$the$basal$ganglia.$
$
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caudate$nucleus$("tail"),$the$putamen$("shell"),$the$globus%pallidus$("pale$globe"),$and$the$
nucleus%accumbens$("leaning").$$All$of$these$structures$a$double$ones,$one$set$on$each$side$of$
the$central$septum.$

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sends$its$messages$to$the$frontal$lobe$(especially$the$orbital$cortex,$just$above$the$eyes),$and$
appears$to$be$responsible$for$informing$us$that$something$is$not$right$and$we$should$do$
something$about$it:$$Wash$your$hands!$$Lock$your$door!$$As$these$examples$are$meant$to$
suggest,$obsessive%compulsive%disorder$(OCD)$is$likely$to$involve$an$overactive$caudate.$$On$the$
other$hand,$an$underactive$caudate$may$be$involved$in$various$disorders,$such$as$ADD,$
depression,$aspects$of$schizophrenia,$and$just$plain$lethargy.$$It$is$also$involved$in$PAP%
syndrome,$a$dramatic$loss$of$motivation$only$recently$discovered$(see$below).$
$
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coordinating$automatic$behaviors$such$as$riding$a$bike,$driving$a$car,$or$working$on$an$assembly$

The prefrontal cortex, which is the part of the frontal lobe which lies in front of the
motor area, is also closely linked to the limbic system. Besides apparently being
involved in thinking about the future, making plans, and taking action, it also appears to
be involved in the same dopamine pathways as the ventral tegmental area, and plays a

part in pleasure and addiction.

The Autonomic Nervous System
The second part of the nervous system to have a particularly powerful part to play in our
emotional life is the autonomic nervous system. The autonomic nervous system is
composed of two parts, which function primarily in opposition to each other. The first
is the sympathetic nervous system, which starts in the spinal cord and travels to a
variety of areas of the body. Its function appears to be preparing the body for the kinds
of vigorous activities associated with fight or flight, that is, with running from danger
or with preparing for violence.

Activation of the sympathetic nervous system has the following effects:

dilates the pupils

opens the eyelids
stimulates the sweat glands
dilates the blood vessels in large muscles
constricts the blood vessels in the rest of the body
increases the heart rate
opens up the bronchial tubes of the lungs
inhibits the secretions in the digestive system
One of its most important effects is causing the adrenal glands (which sit on top of the
kidneys) to release epinephrine (aka adrenalin) into the blood stream. Epinephrine is a
powerful hormone that causes various parts of the body to respond in much the same
way as the sympathetic nervous system. Being in the blood stream, it takes a bit longer
to stop its effects. This is why, when you get upset, it sometimes takes a while before
you can calm yourself down again!
The sympathetic nervous system also takes in information, mostly concerning pain from
internal organs. Because the nerves that carry information about organ pain often travel
along the same paths that carry information about pain from more surface areas of the
body, the information sometimes get confused. This is called referred pain, and the
best known example is the pain some people feel in the left shoulder and arm when they
are having a heart attack.
The other part of the autonomic nervous system is called the parasympathetic nervous
system. It has its roots in the brainstem and in the spinal cord of the lower back. Its
function is to bring the body back from the emergency status that the sympathetic
nervous system puts it into.
Some of the details of parasympathetic arousal include...
pupil constriction
activation of the salivary glands
stimulating the secretions of the stomach
stimulating the activity of the intestines
stimulating secretions in the lungs
constricting the bronchial tubes
decreasing heart rate
The parasympathetic nervous system also has some sensory abilities: It receives
information about blood pressure, levels of carbon dioxide in the blood, and so on.
There is actually one more part of the autonomic nervous system that we don't mention
too often: The enteric nervous system. This is a complex of nerves that regulate the
activity of the stomach. When you get sick to your stomach or feel butterflies when you
get nervous, you can blame the enteric nervous system.

 Copyright 2002, 2009, C. George Boeree

Circumplex model[edit]

The circumplex model of emotion was developed by James Russell.[10] This model
suggests that emotions are distributed in a two-dimensional circular space, containing
arousal and valence dimensions. Arousal represents the vertical axis and valence
represents the horizontal axis, while the center of the circle represents a neutral valence
and a medium level of arousal.[9] In this model, emotional states can be represented at any
level of valence and arousal, or at a neutral level of one or both of these factors. Circumplex
models have been used most commonly to test stimuli of emotion words, emotional facial
expressions, and affective states.[11]
Russell and Lisa Feldman Barrett describe their modified circumplex model as
representative of core affect, or the most elementary feelings that are not necessarily
directed toward anything. Different prototypical emotional episodes, or clear emotions that
are evoked or directed by specific objects, can be plotted on the circumplex, according to
their levels of arousal and pleasure.[12]

Vector model[edit]
The vector model of emotion appeared in 1992.[13] This two-dimensional model consists of
vectors that point in two directions, representing a "boomerang" shape. The model
assumes that there is always an underlying arousal dimension, and that valence

determines the direction in which a particular emotion lies. For example, a positive valence
would shift the emotion up the top vector and a negative valence would shift the emotion
down the bottom vector.[9] In this model, high arousal states are differentiated by their
valence, whereas low arousal states are more neutral and are represented near the
meeting point of the vectors. Vector models have been most widely used in the testing of
word and picture stimuli.[11]

Positive activation negative activation (PANA) model[edit]

The positive activation negative activation (PANA) or "consensual" model of emotion,
originally created by Watson and Tellegan in 1985,[14] suggests that positive affect and
negative affect are two separate systems.
Similar to the vector model, states of higher arousal tend to be defined by their valence,
and states of lower arousal tend to be more neutral in terms of valence.[9]
In the PANA model, the vertical axis represents low to high positive affect and the
horizontal axis represents low to high negative affect.
The dimensions of valence and arousal lay at a 45-degree rotation over these axes.[14]

Plutchik's model[edit]
Robert Plutchik offers a three-dimensional model that is a hybrid of both basic-complex
categories and dimensional theories. It arranges emotions in concentric circles where inner
circles are more basic and outer circles more complex. Notably, outer circles are also
formed by blending the inner circle emotions. Plutchik's model, as Russell's, emanates from
a circumplex representation, where emotional words were plotted based on similarity.[15] In
computer science, Plutchik's model is often used, in different forms or versions,[16] for tasks
such as affective human-computer interaction or sentiment analysis.

Plutchik demonstrates a selection of major human emotions, how they are

related to each other, and how they are different too (or bipolar as he calls the
emotions at opposite sides). At the center of this wheel there are eight basic
emotions (as he refers to them) such as ecstacy and grief. Then each of these
is connected to two more subtle emotions that lead to what Plutchik calls the
eight advanced emotions those around the outside. For this wheel to work
well you need to cut it out and attach each of the leaves to each other such
that acceptance is alongside apprehension, for example, and annoyance next to

boredom. The result is a three-dimensional cone shape.

PAD emotional state model[edit]

The PAD emotional state model is a psychological model developed by Albert Mehrabian
and James A. Russell to describe and measure emotional states. PAD uses three
numerical dimensions to represent all emotions.[17][18] The PAD dimensions are Pleasure,
Arousal and Dominance.
The Pleasure-Displeasure Scale measures how pleasant an emotion may be. For instance
both anger and fear are unpleasant emotions, and score high on the displeasure scale.
However joy is a pleasant emotion.[17]
The Arousal-Nonarousal Scale measures the intensity of the emotion. For instance while
both anger and rage are unpleasant emotions, rage has a higher intensity or a higher
arousal state. However boredom, which is also an unpleasant state, has a low arousal
value.[17]

The Dominance-Submissiveness Scale represents the controlling and dominant nature of

the emotion. For instance while both fear and anger are unpleasant emotions, anger is a
dominant emotion, while fear is a submissive emotion.[17]

Lvheim cube of emotion[edit]

Lvheim cube of emotion

In 2011, Lvheim proposed a direct relation between specific combinations of the levels of
the signal substances dopamine, noradrenaline and serotonin and eight basic emotions. A
three-dimensional model, the Lvheim cube of emotion, was presented where the signal
substances forms the axes of a coordinate system, and the eight basic emotions according
to Silvan Tomkins are placed in the eight corners. Anger is, according to the model, for
example produced by the combination of low serotonin, high dopamine and high
noradrenaline. Lvheim wrote that as neither the serotonin nor the dopamine axis is
identical to the "pleasantness" (i.e. valence) dimension in earlier theories, the cube seems
somewhat rotated when compared to these models.[19]

Solomon