Limbic System Report

Match the behavioral processes below with the part of the brain to which they are most closely related

1. increased activity here when you are memorizing the names of brain areas 
A. limbic system B. amygdala C. hypothalamus
E. septal area

2. increased activity here when you watch a video that makes you sad
A. limbic system C. hypothalamus
D. hippocampus and related structures E. septal area

3. Animals will work very hard to turn on weak electrical stimulation here .
C. hypothalamus


4. damage here make an animal very irritable and jumpy
A. limbic system B. amygdala C. hypothalamus
D. hippocampus and related structures
D. hippocampus and related structures
B. amygdala
A. limbic system
D. hippocampus and related structures
B. amygdala
E. septal area
E. septal area
Greek: "Sea Monster"
B. HIPPOCAMPUS



Found deep in temporal lobe, shaped like a seahorse.
Consists of "two horns" that curve back from the amygdala.
Short-term & long-term memory
When damaged, a person cannot build new memories.
EX: 50 First Dates
Furthermore, impairment can occur fr prolonged exposure to stress hormones such as Glucocorticoids (GCs) that cause disruption in explicit memory.

EX1: In a study performed by Parkad, rats were given the task of correctly making their way through a maze & were stressed by shock or restraint that caused an impaired effect on the hippocampal-dependent memory.

EX2: 27-yr-old Henry Gustav Molaison underwent bilateral removal of almost all his hippocampus in 1953…participated in thousands of tests, semantic & episodic events faded w/in minutes, yet emotions, were often retained. Tragic "experiment" in 2013 book.
Various processes of cognition involve the hippocampus:

Spatial memory
Dorsal Hippocampus – important component for the generation of new neurons, called adult-born granules (GC).
Left Hippocampus – key component in the retrieval of spatial memory.
Parahippocampal region – just like left hippocampus.
 
Learning
CurlikShors - examined the impact of neurogenesis in the hippocampus and its effects on learning.
Hippocampus of Rat
 
C. AMYGDALA


Emotional center of the brain.
Two almond-shaped masses of neurons on either side of the thalamus at the lower end of the hippocampus.
Involved in evaluating the emotional valence of situations (e.g., happy, sad, scary)
Helps recognize potential threats & helps body for flight-or-fight reactions by increasing heart & breathing rate.
When stimulated electrically, animals respond w/ aggression.
Episodic-autobiographical memory (EAM)
Attention and emotional processes
a. Attention – ability to home in some stimuli while ignoring others
A deficit of these cells would result in low emotional functioning, leading too high retention rate of mental diseases, such as anxiety disorders. (Pessoa, 2009).
HYPOTHALAMUS (Cont.)

Provide info about ion balance and temperature of the blood.
Recent discoveries, leptin w/c is released by fat cells when we overeat. The hypothalamus apparently senses the levels of leptin in the bloodstream & responds by decreasing appetite.
EX: People who have mutation in a gene w/c produces leptin can't tell that they have had enough to eat.
However, many overweight people don't have this mutation – there's still a lot of research to do!
The hypothalamus sends instructions to the rest of the body in two ways:

ANS – allows hypothalamus to have ultimate control of things like blood pressure, heartrate, breathing, digestion, sweating, & all the sympathetic & parasympathetic functions.
Via the pituitary gland – "master gland", pumps hormones called releasing factors into the bloodstream. Growth & metabolism.
The hypothalamus receives inputs from a number of sources:

From the vagus nerve, it gets information about blood pressure & the distension of the gut (how full your stomach is).
From the reticular formation (in the brain stem), info about skin temperature.
From optic nerve, light and darkness.
From unusual neurons lining the ventricles, about contents of the CSF, including toxins that lead to vomiting.
From Olfactory nerves, info that helps regulate eating and sexuality.

Hypothalamus
Cannon-Bard theory of emotion and sham rage
Bard, a student of Cannon's, made serial transections, essentially disconnecting the cerebral cortex from outflow pathways in cats. When transection just included the forebrain (a), a range of behaviors constitutive of rage was observed when a cat was presented with innocuous stimuli.
These behaviors included:
Arching of the back
Extension of claws
Hissing
Spitting
Pupil dilation
Increased blood pressure, heart rate and adrenal secretion

Cannon-Bard theory of emotion and sham rage (2)
This rage was called "sham rage" because animals retained emotional responses, but the responses lacked aspects of emotional behavior that was normally observed during rage. Besides being elicited by innocuous stimuli, sham rage subsided rapidly upon stimulus removal and was undirected; animals even bit themselves.
When Bard performed progressive transections (b and c), when the posterior hypothalamus was disconnected, no coordinated rage response was observed.


Two theories of emotion
A. HYPOTHALAMUS
A small part of the brain located just below the thalamus on both sides of the third ventricle.
One of the busiest parts of the brain.
Mainly concerned with homeostasis.
Homeostasis – process of returning something to some "set point".
EX: Thermostat
Responsible for regulating your hunger, thirst, response to pain levels of pleasure, sexual satisfaction, anger and aggressive behavior, and more.
Also regulates the functioning of the ANS. w/c in turn means it regulates things like pulse, blood pressure, breathing, and arousal in response to emotional circumstances.

Main components of the LIMBIC SYSTEM
Limbic system and hypothalamus
Functions of the Amygdala
Relate environmental stimuli to coordinated behavioral autonomic and endocrine responses seen in species-preservation.
Responses include:
Feeding and drinking
Agnostic (fighting) behavior
Mating and maternal care
Responses to physical or emotional stresses.
Social processing

Todorov's study – fMRI tasks. general evaluation of faces.
Koscik's study – trait of trustworthiness in the evaluation of faces. Individuals suffered damage tended to confuse trust & betrayal.
Rule's study in 2009 - Evaluating general first impressions & relating them to real-world outcomes. Involved first impressions of CEO's.
When damaged, disrupts emotional reactions in monkeys & makes them social outcasts.
When removed, animals get very tame & no longer respond to things that would have caused rage before or become indifferent to stimuli that would have otherwise have caused fear & even sexual responses. Monkeys appears cannot recognize the meaning of emotionally & socially important signals fr other monkeys.
Amygdaloid body :
Large nuclear group in temporal lobe.

Classic Experiments from Watson and Rayner demonstrating fear conditioning in an infant
Fear conditioning in rodents.
The amygdala has appropriate anatomical connections for mediating fear conditioning



Amygdala stimulation produces emotional behaviors through subcortical pathways
Summary of Emotion and Reward in the Limbic System
We reviewed old theories of emotion, the basic purpose of the limbic system, and the basic anatomy of the limbic system.
The hypothalamus plays an important role in generating emotional behaviors…but
The amygdala has been implicated in playing a prominent role in integrating information and coordinating emotional behaviors in response to sensory stimuli, events, and memories. These findings were demonstrated in:
Fear conditioning studies in rodents
Monkey studies (Kluver-Bucy)
Human neuroimaging and lesion studies
Studies of memory modulation by hormones in lower animals.
Reward processing occurs in distinct brain circuits.
Stimulation of these circuits can provide powerful reinforcement signals.
Dopaminergic neurons in the ventral tegmental area provide a learning signal that reflects a computation comparing the reward received to the reward expected.
Drugs of abuse act on reward circuits.
Psychiatric disorders such as depression, anxiety disorders, and addiction, all involve limbic system neural circuitry.
Fear conditioning is a tool for investigating neural substrates of emotion.
Fear conditioning is a process in which a neutral stimulus (conditioned stimulus, CS) is paired with an aversive stimulus (unconditioned stimulus, US), so that the CS comes to predict an aversive outcome, eliciting fear behaviors even in the absence of the US.
Fear conditioning can be found in a large range of animals, from rodents to rabbits to humans.
As early as the 1920s, fear conditioning was demonstrated in infants. A white rat presented to an infant does not innately elicit fear, but pairing the rat with an aversive noise, produces crying and attempts to crawl away, even when the rat was presented without the noise.
The amygdala in humans has been linked to emotional processing (2)
Imaging studies have revealed that the amygdala is activated differentially by emotional facial expressions.
Other functional imaging studies have shown the amygdala to respond to emotionally arousing stimuli.
PNS, Fig. 50-6
Drugs of abuse increase dopamine release in the brain
Cocaine and amphetamines increase dopamine release in the brain, especially in the shell of the nucleus accumbens. The nucleus accumbens shell receives dopaminergic input from midbrain dopamine neurons, and it projects to the hypothalamus and limbic structures mediating emotional responses. Both drugs appear to work by blocking the dopamine transporter responsible for dopamine reuptake, thus leaving dopamine present in the synapse.
Nicotine also enhances dopamine release, by acting on presynaptic cholinergic receptors.


The limbic system largely consists of what was previously known as the limbic lobe.



RELATED AREAS
Cingulate gyrus
- Part of the cerebrum that lies closest to the limbic system, just above the corpus collosum.
- Provides pathway fr the thalamus & to the hippocampus.
- Responsible for focusing attention on emotionally significant events. Associating memories to smells & to pain.
Ventral tegmental area (below the thalamus)
- Consists of dopamine pathways that seem to be responsible for pleasure.
- EX: People w/ damage here tend to have difficulty getting pleasure in life, & often turn to alcohol, drugs, sweets, & gambling.
Basal Ganglia
- Lie over & to the sides of the LS & are tightly connected w/ the cortex above them.
- Responsible for repetitive behaviors, reward experiences, & focusing attention.
- Receives input fr the cerebral cortex w/c sends outputs to the motor centers of the brain stem,
- A part of the basal ganglia called the striatum controls posture & movement. Research indicate that, inadequate supply of dopamine, the striatum is affected, can lead to Parkinson's disease.
*Surprisingly, patients w/ Parkinson's Disease can make a quick, automatic reactions to specific triggering stimuli, especially under stress. EX: A former baseball player who was paralyzed this way could quickly raise his hands to catch a ball thrown at him unexpectedly.
The ff: structures are, or have been considered, part of the LS:
1. Cortical areas:
Limbic lobe
Orbitofrontal cortex, process of decision-making.
Piriform cortex, part of the olfactoriy system
Extorhinal cortex, related w/ mem & associative components
Hippocampus
Fornix, a white matter structure connecting the hippocampus w/ other brain structures, particularly the mammillary bodies & septal nuclei.

2. Subcortical areas:

Septal nuclei – pleasure zone
Amygdala
Nucleus accumbens: involved in reward, pleasure & addiction
EX: In 1954, Olds & Milner research on rats. Electrical stimulation
Electrical self-stimulation and reward
In 1954, James Olds and Peter Milner found that brain stimulation to parts of the hypothalamus and related structures can act as a reinforcer. This stimulation worked independent of drive state (e.g. hunger), and has been replicated in many brain structures.
A key finding in these studies is that brain stimulation activates neurons in the ventral tegmental area. These are midbrain dopamine neurons that form most of the mesolimbic and mesocortical projections involved in reward. Stimulating these neurons leads to dopamine release. Rats will often choose self-stimulation over food and sex.

5. becomes more active when you get thirsty 
A. limbic system B. amygdala
D. hippocampus and related structures E. septal area

6. the system essential for normal motivation and emotion; it includes all the other brain areas in the list
B. amygdala C. hypothalamus
D. hippocampus and related structures E. septal area

7. Some babies are born with damaged basal ganglia. Which of the following are they likely to show as grown-ups? 
A. difficulty in consciously learning and remembering things they see, read, or hear about
 

C. problems with motivation, emotion, and reward 
D. problems planning what they must do to get a job done successfully 
E. problems waking up or falling asleep
 C. hypothalamus
A. limbic system
B. jerky, awkward, poorly timed movements, making even simple actions like walking difficult



History
Paul Broca
coined the term based on its physical location in the brain, sandwiched
b/w 2 functionally diff components.
- The term "le grand lobe limbique" was first used by Broca in 1878.

2. James Papez
American physician described his anatomical model of emotion, Papez circuit.

3. Paul D. MacLean
- The term 'limbic system' was first used by MacLean in 1952.
- Evolution
- triune brain theory
- Limbic system is older than other parts of the fore brain.
- Had evolved in early mammals to control fight-or-flight responses.
- From epileptic patients, turned to cats, monkeys, & other models.

4. Heinrich Kluver & Paul Bucy
– bilateral removal of the temporal lobes in monkeys created an extreme emotional syndrome. Monkeys showed decrease in aggression.
- Revealed reduced threshold to visual stimuli, & were thus unable to recognize objects that were once familiar.
The Emotional Nervous System
Limbic System

and Basal Ganglia
Anatomy of limbic system
The functions of the limbic system are also ancient, and they play an important role for survival in the animal kingdom. Limbic functions can be divided into the following four basic categories:
1. Homeostatic functions,
including autonomic and neuroendocrine control
2. Olfaction
3. Memory
4. Emotions and drives
"HOME"
What are the main functions of Limbic System?
LIMBIC SYSTEM

Definition/Explanation

Limbic – Latin – Limbus, for "border" or "edge".
Emotional life is largely housed in the LS.
Primarily responsible for our emotional life & formation of memories.
Defined by Paul Broca as a series of cortical structures surrounding the limit b/w the cerebral H. & brainstem.
Includes the hypothalamus, the hippocampus, the amygdala, and several other nearby areas.
Supports a variety of functions including epinephrine flow, emotion, behavior, motivation, long-term memory & olfaction.
Emotional & motivational processes.
Involved in motivation, emotion, learning, & memory.
Operates by influencing the Endocrine System & ANS.
Some of the disorders associated w/ the LS are epilepsy, schizophrenia, Alzheimer's disease, anterograde amnesia, retrograde amnesia, & Kluver-Bucy syndrome.








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