In the case of Mr. V, he was very intelligent and even scored in the top 5
percent of the WAIST. He clearly knew he was paralyzed and in a wheel chair
but he failed to understand its implications or understand its significance.
The fact that he was unable to hike in the woods did not figure into his plans.
An emotional response consists of 3 types of components
1. Behavioral: muscular movements that are appropriate to the situation
that elicits them
2. Autonomic: facilitate the behaviors and prove quick mobilization of
energy for vigorous movement (increase activity if sympathetic branch
and decrease activity of parasympathetic branch).
3. Hormonal: hormones secreted by glands like the adrenal medulla an
adrenal cortex reinforce the autonomic responses.
The amygdala plays a special role in physiological and behavioral reactions
to objects and situations that warn of pain, unpleasant consequences, and
signify the presence of food, water, salt, potential mates or rivals.
Single neurons in the various nuclei of the amygdala become active when
emotionally relevant stimuli are presented.
Physiology of the Amygdala:
Locates within the temporal lobes
Consists of several groups of nuclei each with different functions
The amygdala has been subdivided into approximately 12 regions, each
containing several sub-regions.
o 3 major regions: lateral nucleus, the basal nucleus, the central nucleus
Lateral Nucleus: Receives info from all regions of the neocortex (including
the ventromedial and prefrontal cortex) the thalamus and the hippocampal
formation. Sends info to the basal nucleus, the dorsal medial nucleus of the
thalamus and the ventral striatum. The LN and the BN send info to the
ventromedial prefrontal cortex and the central nucleus. The central nucleus
projects to regions of the hypothalamus, midbrain, pons and medulla.
ACTIVATION OF THE CENTRAL NUCLEUS elicits behavioral, autonomic and
o The central nucleus is the single most important part of the brain for
the expression of emotional responses provoked by aversive stimuli.
Damage to the CN reduces a wide range of emotional behaviors and
physiological responses including no longer showing fear when
confronted with stimuli paired with aversive events, lower blood
levels of stress hormones and acting more tame when handled by
humans. Monkeys with no CN show no fear of snakes. Long term
stimulation of the CN produces stress induced illnesses like gastric
o Loud unexpected noises, the approach of large animals, heights and
specific odors automatically activate the CN. o Also the ability of the animal to learn that a particular stimulus or
situation is dangerous is very important.
Conditioned emotional response: a classically conditioned response that
occurs when a neutral stimulus is followed by an aversive stimulus; usually
includes autonomic, behavioral and endocrine components such as changes
in heart rate, freezing, and secretion of stress related hormones.
o In emotional response conditioning, the animal begins to elicit the
same physiological responses to the CS that the animal would
normally show to the US. In addition, the animal will show behavioral
arrest such as freezing (a CR response).
o Research indicates the physical changes responsible for the classical
conditioning of a conditioned emotional response takes place in the
lateral nucleus of the amygdala (this is the area that communicates
with the CN which is responsible for behavioral/hormonal changes).
o The purpose of a conditioned emotional response is that it prepares
an animal to confront an aversive stimulus.
o In the lab, if the CS is presented repeatedly by itself, the previously
established CR becomes extinguished. Note that extinction does not =
forgetting. The memory for the association between the CS and the US
is not erased but rather inhibited by the ventromedial prefrontal
cortex (vmPFC) lesions of the vmPFC impair extinction. The
vmPFC also modulates the expression of fear in different
Research with Humans
Specific Response: A response that is aimed at terminating the painful
stimulus, like letting of something that is hurting you.
Nonspecific response: Responses elicited by the painful stimulus that are
controlled by your autonomic nervous system (like blood levels going up,
hormones being secreted etc.)
Stimulation of parts of the brain produces autonomic responses that are
often associated with fear and anxiety but that only when the amygdala was
stimulated did people also report that they actually felt afraid. Those with
lesions to the amygdala show a decrease in people’s emotional responses.
Most humans fears are acquired socially and not through firsthand
experience. This can occur by watching another person being attacked or by
seeing another person display signs of fear or through instruction.
Human studies have shown that there is an increased activity of the medial
prefrontal cortex with extinction of the conditioned response.
Damage to the amygdala interferes with the effects of emotions on memory.
Normally, when people encounter events that produce a strong emotional
response, they are more likely to remember these events. No increase in
those with Alzheimer’s disease.
Patients with amygdala damage had no trouble with musical perception
(recognizing dissonance vs. consonance) but were unable to recognize scary
music (or any music that is normally associated with fear). Anger, Aggression and Impulse Control
Almost all species of animals engage in aggressive behaviors, which in most
cases is species specific. Many aggressive behaviors are related to
reproduction (i.e. behavior to attract mates/defend territory to build nest
In an aggressive situation, an animal might display:
a. Threat behaviors: postures or gestures that warn the adversary to
leave or it will become the target of the attack useful in reinforcing
social hierarchies in organized groups of animals.
b. Defensive behaviors: threat behaviors or an actual attack against the
animal that is threatening.
c. Submissive behaviors: behaviors that indicate that it accepts defeat
and will not challenge the other animal.
While engaged in attacking a member of the same species or defending itself
against the attack, an animal appears to be extremely aroused with activity of
the sympathetic branch being very high.
Predation: The attack of a member of one species on a member of another,
usually because the latter serves as food for the former. The sympathetic
nervous system is not really activated when a predator attacks because it is
not angry but rather killing as a means to an end.
The neural control of aggressive behavior is hierarchical: the perceptual
system detects the status of the environment, which activates the limbic
system, the hypothalamus and amygdala control the activity of the brain
stem circuits which controls particular muscular movements that an animal
makes in attacking or defending itself.
Investigators found that aggressive attack and predation can be elicited by
stimulation of different parts of the PAG and that the hypothalamus and the
amygdala influence those behaviors through excitatory and inhibitory
connections with it.
Three principle regions of the amygdala and two regions of the
hypothalamus affect defensive rage and predation, both of which appear to
be organized by the PAG.
Lots of evidence suggests that activity of serotonergic synapses inhibits
aggression. The destruction of seretonergic axons in the forebrain facilitates
Investigators studied the levels of 5-HIAA (a metabolite of serotonin) in
monkeys and found that those with the lowest levels of 5-HIAA were the
most likely to engage in risky behavior, picking fights with those much larger
than themselves and to show high levels of aggression. Serotonin does not
simply inhibit aggression; rather it exerts a controlling influence on risky,
which includes aggression.
Early experiences can certainly foster the development of aggressive
behavior, but studies have shown that heredity plays a significant role. They
found a higher correlation between monozygotic twins than dizygotic twins on measure of antisocial behaviors genetic component in development of
traits. No evidence was found that a shared environment played a role.
A depressed rate of serotonin are associated with assault, arson, murder and
Taking Fluxetine (prozac), a serotonin agonist, can decrease irritability and
The ventro medial prefrontal cortex which includes the medial orbitofrontal
cortex and the subenual anterior cingulated cortex plays an important role in
regulating our urges to respond emotionally to stimuli. It is found at the
bottom of the front of the cerebral hemispheres. It’s inputs provide it with
info about what is happening in the environment and what plans are being
made by the rest of the frontal lobes and its outputs permit it to affect a
variety of behaviors and physiological responses, including emotional
responses organized by the amygadala.
Phineus Gage: Before his injury he was serious, industrious and energetic.
Afterward, he became childish, irresponsible and thoughtless of others. He
was unable to make or carry out plans and his actions appeared to be
capricious and whimsical. His accident had largely destroyed the vmPFC
People whose vmPFC has been damage are still able to assess the significance
of a situation but only in a theoretical sense. One patient always gave sensible
answers in response to what should be done in a hypothetical situation but in
his own life, he acted irresponsibly and irrationally. So he could recall the
normal patterns of social behavior before his brain legion in real life, he
failed to evoke them. the vmPFC serves as an interface between automatic
emotional responses and complex behavior.
Damage to the vmPFC really causes emotional dysregulation. Unfortunately,
there is a significant correlation between emotional dysfunction and
impairments in real world competencies emotional problems (rather than
cognitive problems) lie at the base of the real-world difficulties exhibited by
people with vmPFC damage.
Courage is also associated with the vmPFC. Brain imaging showed that
people who displayed courage had an activation of the sgACC, an area of the
Recent research suggests that emotions and emotional reactions to things
play an important role-perhaps the most important role- in the formation of
moral judgments (and not rational decision making) the vmPFC is
involved in moral judgments.
o Patients with vmPFC damage, demonstrate utilitarian moral judgment
such as “killing one person is better than letting five people get killed”
these are judgments based on rational reasoning and not emotions.
Recap: the amydala plays an important role in provoking anger and violent
emotional responses and the vmPFC inhibits this behavior. The amygdala
matures early in development whereas the vmPFC natures later in late
childhood. A study showed that aggressive behavior during parent-child interactions was positively related to the volume of amygdala and negatively
related to the relative volume of the vmPFC.
In emotional murders, who are impulsive, there seems to be a decrease in
prefrontal activity and increase in subcortical activity.
People with antisocial personality disorder showed an 11 percent reduction
in volume of the gray matter of the prefrontal cortex.
The prefrontal cortex and serotonergic neurons, two entities that are
associated with the control of aggression appear to be linked. The prefrontal
cortex receives a major projection of serotonergic axons. Research indicates
that serotonergic input to the prefrontal cortex activates the region. The
release of 5-HT has been found to increase the activity of the prefrontal
cotex. Decreased input from sertonergic neurons to the prefrontal cortex can
result in emotional problems like aggression.
Aggression in Males
Many forms of aggressive behavior are affected by hormones
Early androgenization has an organizational effect that stimulates the
development of testosterone-sensitive neural circuits that facilitate
The organizational effect of androgens on intermale aggression is important
but it is not an all or none phenomenon. Prolonged administration of
testosterone will eventually induce intermale aggression even in rats that
were castrated immediately. Exposure to androgens early in life basically
decreases the amount of exposure needed to activate aggressive behavior
later in life. It sensitizes the neural circuits.
Testosterone implanted in the Medial Preoptic Area reinstated intermale
aggression castrated rats. The testosterone directly activated the behavior
by stimulating the androgen sensitive neurons located there. The MPA is
related to intermale aggression among a number of other things.
Male rodents are able to tell the sex of the intruder of his territory but the
use of pheromones. Intermale aggression was found to be abolished in mice
by cutting the vomeronasal nerve, which deprives the brain of input from
the vomeronasal organ.
Aggression in Females
Normally females are much less aggressive in neutral territories but an
increase in testosterone makes them more aggressive (estradiol has no
Androgens have an organizational effect on the aggressiveness of females
and an increase exposure to testosterone in the womb causes the female rat
to be more aggressive as an adult.
Females of some primate species tend to be more aggressive around the
time of ovulation and just before menstruation.
Effects of Androgens on Human Aggressive Behavior
Prenatal androgenization increases aggressive behavior in humans as well. After puberty, androgens also begin to have activational effects. Boys
Testosterone levels begin to increase during the early teen, at which time
aggressive behavior and intermale fighting also increase.
In a study comparing twins consisting of a girl-girl, and a boy-girl the girl
from the latter group proved to be more aggressive presumably because of
more prenatal exposure to Testosterone. However, it is very possible the
increase aggressiveness was due to growing up with a twin brother.
Girls with the condition of CAH which results in an increased production of
androgens cause girls to be more aggressive and to display “boyish interests”
as a child.
Castrating males appears to lower sex related aggression but because of
obvious moral issues there has been a lack of conclusive studies.
Individuals who display high aggression and instances of sexual assault have
been treated with synthetic steroids that inhibit the production of androgens
by the testes. But the effect of these drugs are not irreversible and have no
effect on other forms of aggression that are related to sex-aggression.
Most studies have found a positive relationship between men’s testosterone
levels and their level of aggressiveness.
However it has been suggested that the primary social effect of androgens
may be not on aggression but on dominance.
But we must keep in mind that correlation does not indicate causation so
even though these studies indicate that higher T levels increases aggression
we can never be sure. For instance, a person’s environment effects his/her T
levels. Losing a game or watching your team lose decreases T levels and
winning it increases T levels.
Studies have shown that sports competitors that take anabolic steroids and
synthetic hormones that have androgenic effects makes them more
aggressive. But again, causation cannot be inferred.
Studies have found that there is an interaction between alcohol and social
status and testosterone. In the mating season, when male monkeys had 2 to 3
times higher levels of T the DOMINANT monkeys became even more
aggressive when given alcohol. During the nonmating season, only the
dominant monkeys that were injected with T and given alcohol increased
their aggressive behavior. Subordinate moneys did not have this increase in
behavior presumably because they had learned not to be aggressive.
Communication of Emotions
Many species of animals communicate their emotions to others by means of
postural changes, facial expressions and nonverbal sounds. These
expressions serve useful social functions: they tell other individuals how we
feel and-more to the point-what we are likely to do. They warn a rival that we
are angry or tell them that we are sad and want comfort etc. Emotions are
used in communication.
Darwin suggested th