Introduction to psychology
Chapter 6
Mechanisms of motivation and emotion

The general principles of motivation

Motivation: the entire constellation of factors, some inside the organism and some outside, that cause an individual to behave in a particular way at a particular time.

Motivational state, or drive.
An internal condition that orients an individual toward a specific category of goals that can change over time in a reversible way. (The drive an increase and decrease).
Different drives direct a person toward different goals.
Those are hypothetical constructs! We infer the existence from the animal’s behavior.

Motivated behavior is directed toward incentives, the sought-after objects or ends that exist in the external environment.
Incentives are also called reinforces.

Drives and incentives complement one another in the control of behavior. If one is weak, the other must be strong to motivate the goal-directed action.
They also influence each other’s strength. A strong drive can enhance the attractiveness of a particular object.
A strong incentive can strengthen a drive.

Varieties of drives

In general, drives motivate us toward goals that promote our survival and reproduction. Some drives promote survival by helping us maintain the internal bodily conditions that are essential for life.

Drives that help preserve homeostasis.

Homeostasis: the constancy of internal conditions that the body must actively maintain.
Maintaining homeostasis involves the organism’s outward behavior as well as its internal processes.
The basic physiological underpinning for some drives is a loss of homeostasis, which acts on the nervous system to induce behavior designed to correct the imbalance.

Limitations of homeostasis: regulatory and nonregulatory drives

Homeostasis is not enough for understanding many drives.
Two general classes of drives:

• Regulatory drive:
  Like hunger, helps preserve homeostasis
• Nonregulatory drive
  Like sex, that serves some other purpose

A functional classification of mammalian drives

Five categories of mammalian drives:

• Regulatory drives
  Drives that promote survival by helping to maintain the body’s homeostasis
• Safety drives
  Drives that motivate an animal to avoid, escape or fend of dangers such as precipices, predators or enemies. (Like fear).
• Reproductive drives
  Like the sexual drive and the drive to care for young once they are born.
  When at peak, these drives ca be extraordinarily powerful.
• Social drives
  Many mammals require the cooperation of others to survive.
• Educative drives
  Primarily the drives to play and explore.
  When other drives are not too pressing, the drives for play and exploration come to the fore.

Human drives that seem not to promote survival or reproduction

One view:
Pursuits of art, music and so on are extensions of our drives to play and exploration.

A different view:
Art, music and literature appeal to us not because we have special drives for them, but because they tap into many of our already existing drives and proclivities, which evolved for other purposes.
It is for satisfying other drives rather than drives in and of themselves is not to diminish them.
These pursuits enrich our lives. They extend us beyond evolutions narrow dictates of mere survival and reproduction.

Drives as states of the brain

Drives are products of physical processes within the body, particularly within the brain. In theory, every drive that we experience corresponds with some state of the brain.

Central-state theory of drives
Different drive correspond to neural activity in different sets of neurons in the brain.
A set of neurons in which activity constitutes a drive is called a central drive system.
Although the central drive systems for different drives must be at least partly different from one another, they may have overlapping components.

Characteristics a set of neurons must have to serve as a central drive system.

• It must receive and integrate the various signals arise or lower the drive state.
• It must act on all the neural processes that would be involved in carrying out the motivated behavior. It must direct perceptual mechanisms toward stimuli related to the goal, cognitive mechanisms toward working out strategies to achieve the goal and motor mechanisms toward producing the appropriate movements.

The central drive systems are part of the top of the hierarchal model of the control of action.
To affect behavior they must influence the activity of motor systems at lower levels of the hierarchy.

The hypothalamus is the hub of many central drive systems.
It is centered at the base of the brain, just above the brainstem and it is strongly interconnected with higher areas of the brain.
It has direct connections to nerves that carry input from, and automatic motor output to, the body’s internal organs.
It has many capillaries and is more sensitive to hormones and other substances carried by the blood than are other brain areas.
Through its connections to the pituitary gland it controls the release of many hormones.

Reward mechanisms of the brain

Motivated behavior involves the input of rewards.

Three components of reward: liking, wanting and reinforcement

A reward has three interrelated, but in some ways separable, meanings. It is something:

• That we like
  • Liking
    The subjective feeling of pleasure or satisfaction that occurs when one receives a reward.
• That we want
  • Wanting
    The desire to obtain reward.
    Before a reward is received.
    Measured by assessing the amount of effort an individual will exert, the amount of pain the individual will bear, in order to obtain the reward.
    Wanting and liking can be separated.
• That serves as a reinforcer in learning
  • Reinforcement
    The effect that rewards have in promoting learning.
    Animals and people learn to attend to stimuli that signal the availability of rewards, and they learn to make responses that bring rewards in the presence of those stimuli. Through its effects in the brain, a reward helps to stamp in the memory of stimuli and actions that occurred just before the reward was received.
    Such learning helps the individual to become more effective in finding and producing him same type of reward in the future.

Identification of reward neurons in the brain

Rats and other animals will work hardest and longest to stimulate a tract in the brain called the medial forebrain bundle.
The neurons of this tract that are most crucial for this rewarding effect have their cell bodies in nuclei in the midbrain and synaptic terminals in a large nucleus in the basal ganglia called the nucleus accumbens.
The accumbens itself has connections to large areas of the limbic system and the cerebral cortex, and it is a crucial center for behavioral effects of rewards.

The medial forebrain bundle and the nucleus accumbens become active in all sorts of situations in which and individual receives a reward.
Damage of either of these brain structures destroys all sorts of motivated behavior.
Without a functioning medial forebrain bundle or nucleus accumbens, animals will not work to find or obtain rewards and will die unless they are provided with food and water through a stomach tube.

Separating the liking and wanting systems

Many of the neurons of the medial forebrain bundle that terminate in the nucleus accumbens release dopamine as their neurotransmitter.
This release is essential for ‘wanting’ the component of reward, but not for the ‘liking’ component.
Dopamine helps motivate the animal to obtain the reward but is not essential for the pleasure received from obtaining the reward.
The larger the expected reward, the greater degree of dopamine release in the nucleus accumbens.

Some neurons of the medial forebrain bundle that terminate in the nucleus accumbus release a transmitter that is in the endorphin family.
Endophins are chemicals created within the body that have effects similar to those of morphine and other opiate drugs such as opium and heroin; they are best known for their role in inhibiting the sense of pain.
Endorphins released into the nucleus accumbens are crucial for the immediate pleasure experienced when rewards are received or consumed.

Role of dopamine in reinforcement for learning

The learning component of reward is closely related to the wanting component.
Animals learn that certain cues signal the availability of a reward, and those cues prompt the animal to search for or work for the reward, which is the behavioral indicator for wanting.
The release of dopamine into the nucleus accumbens appears to be crucial not just for motivating animals to work for their rewards, but also for their ability to learn to use clues to predict when and where rewards are available.

• Dopamine release promotes long-term potentiation (LTP) of neural connections within the nucleus accumbens. LTP is believed to be part of the cellular basis for learning throughout the brain.

When a reward is unexpected, dopamine release immediately after the reward helps to reinforce an association between the reward and any stimulus or response that happened to precede it.
When the cues and responses leading to a reward have already been well learned, there is no need for further reinforcement of that learning, and dopamine release in response to the reward ceases. Dopamine release now occurs in response to the signal preceding reward because now the animal’s interest lies in learning how to predict when the signal will appear or how to make it appear.

Hijacking the brain’s reward system

Drug addiction

Drugs exert their euphoric and habit-producing effects through action on the brain’s reward pathways.
These drugs mimic or promote the effects of dopamine and endorphins in the nucleus accumbens.

The nucleus accumbens is a key area where drugs act to produce their addictive effects.

Not only do drugs produce an immediate sense of euphoria, but even more significant for the problem of addiction, they strongly activate the dopamine-receiving neurons in the nucleus accumbens that are responsible for promoting reward-based learning.
Normal rewards activate those neurons only when the reward is unexpected, but drugs, through their chemical effects, activate those neurons every time the drug is taken.
The result is a sort of super learning.
With each dose of the drug, the dopamine response acts to reinforce, once again, associations between any cues that are present in the environment and the feelings and behaviors of wanting and taking the drug.

Drug addicts lose their ‘liking’ of the drug, even while their ‘wanting’ of the drug increases.
The loss of ‘liking’ occurs, presumably, because of drug-induced changes in the brain that reduce the endorphin-mediated pleasure response.
Because the dopamine response is not reduced, the learned drug craving and habit continue to grow stronger with each dose.
The carving itself becomes the main reason for taking the drug.

A brain-based theory of compulsive gambling

Compulsive gambling is in some way similar to drug addiction.
Gamblers claim to feel a euphoric high when they are gaming and winning, and to experience withdrawal symptoms when they try to abstain.
Every cue in the environment that has been previously associated with gambling elicits in them a strong urge to gamble.

Games of chance with monetary rewards are powerful activators of the nucleus accumbens and other structures known to be part of the brain’s reward system.
Because the payoff is never predictable, every instance of payoff results in a new burst of dopamine release in the nucleus accumbens, no matter how many times the person plays.

Hunger: an example of a regulatory drive

Neural and hormonal control of appetite

The purpose of hunger and satiety is to regulate the amount of food materials in the body at an appropriate level for survival and well-being.

Any regulatory system makes use of feedback control.
The substance or quality being regulated feeds back upon the controlling device and inhibits the production of more that substance or quality when an appropriate level is reached.
Like a thermostat, but far more complicated.
Sets of neurons in the brain’s hypothalamus raise or lower the animal’s drive to eat, and these neurons are themselves regulated by the body’s deficit or surfeit of food materials.

The nucleus in the hypothalamus serves as an appetite-control center

The neurons that constitute the food-o-stat exist in several closely interconnected portions of the hypothalamus, but are most concentrated in the arcuate nucleus. The arcuate nucleus lies in the center of the lowest portion of the hypothalamus, very close to the pituitary gland.
This is the master control center for appetite and weight regulation.
It contains two classes of neurons that have opposite effects:

• Appetite-stimulating neurons
  Promote all the effects that are associated with increased hunger
• Appetite-suppressing neurons

Both of the classes exert their effects on other brain areas through the release of slow-acting neurotransmitters, which have the capacity to alter neural activity for long periods of time. (From minutes to several hours).
One of the appetite-stimulating neurons is neuropeptide Y (NPY). This is the most potent appetite stimulator yet discovered.

The neurons of the arcuate nucleus are themselves acted upon by many different inputs that, in one way or another, reflect the need or lack of need for food.

Many internal signals contribute to short-term regulation of appetite

Eating a large meal produces a number of physiological changes in the body.

• Slightly elevated body temperature
• Increased blood level of glucose
• Distention of the stomach
• Intestines and the release of certain hormones produced by endocrine cells in the stomach and intestines

All these changes can either directly or indirectly incite neurons in the arcuate nucleus and nearby areas of the hypothalamus to activate hunger-suppressing neurons and inhibit hunger-stimulating neurons.
When all these effects are operating properly, the result is a decline in appetite for several hours following ingestion of a meal.

One appetite-suppressing hormone that has received considerable attention is peptide Y-Y3-36 (PYY). This is produced by special endocrine cells in the large intestine.
Food entering the intestines stimulates secretion of PYY into the bloodstream.

Insufficient PYY production can be a contributing cause of obesity.

Leptin contributes to the long-term control of appetite and body weight

The hunger mechanism is sensitive to the amount of fat stored in the body.

Fat cells secrete a hormone, called leptin, at a rate that is directly proportional to the amount of fat that is in the cells.
Leptin is taken up into the brain and acts on neurons in the arcuate nucleus and other parts of the hypothalamus to reduce appetite.

Animals with no production of leptin become extremely obese.
Many obese people feel chronically hungry, not because their lack of leptin, but because their brains are relatively insensitive to the hormone.

Roles of sensory stimuli in control of appetite

Hunger is provoked not just by events inside us, but also by sensory stimuli in the environment.
Evolution led us and other animals to be opportunist with regard to food, our hunger increases when food is available.
Classical conditioning can bring on a sudden surge of appetite.
Once a person begins to eat, the taste of the food can influence the reduction or prolongation of appetite during the meal.

Sensory-specific satiety. If an individual eats a type of food until they are satiated experience renewed appetite when a different food, with a different taste is placed before him.
This is mediated primarily by the sense of taste. When people eat one food at a meal, their rating of the taste pleasantness of that food declines relative to their rating of the taste pleasantness of other foods.
The sight and smell of a new food can result in renewed activity in appetite-stimulating neurons in the hypothalamus after the animal has been sated on different food.

Problems of obesity

Effects of genes and nutrition on body weight

The environmental conditions that promote obesity are fairly constant within one culture, so differences in weight have mostly to do with genetic differences in how individuals respond to those conditions.

Across cultures, environmental differences can have a large effect on body weight.

The genes that promote obesity in our culture do so by increasing the person’s attraction to high-calorie foods, by decreasing one or another of the feedback effects that high food intake or fat level has on the hunger mechanisms in the hypothalamus, and by decreasing the body’s ability to burn up excess calories quickly.
Where high-calorie foods are unavailable, the same genes generally don’t lead to obesity.

All sugars are not alike as far as the brain is concerned, and fructose, found in abundance in many prepared foods, may be a particular problem when it comes to obesity.

Modern live is also marked by a decrease of physical activities.

Woman with poor diets when pregnant are more apt to have children who are overweight. Such infants typically have lower birth weight than infants with better prenatal nutrition. The infants show elevated levels of leptin. They develop thrifty phenotypes, storing more fat.
Predictive adaptive responses.

Problems of dieting

Weight gained is often very difficult to lose.
Decreased food intake not only activates the hunger mechanisms in the brain, but can also produce a decline in basal metabolism (the rate at which calories are burned while the individual is at rest) making the body convert food more efficiently to fat.

A combination of exercise and dieting is far more effective in producing long-term weight loss than is dieting alone.
Regular exercise not only burns op calories immediately, but also build muscle which, even when resting, burns calories at a higher rate than do other body tissues.

Sex: an example of a nonregulatroy drive

Keep in mind: this is only physiological

Among nonhuman animals, copulation occurs in a stereotyped way, one set of postures and movements for the female and a different set for the male.
Humans differ from other species also in the hormonal regulation of the sexual drive, especially females.

Hormonal influences on male sex drive

The most crucial hormone for the maintenance of the sexual drive is testosterone, a form of androgen, produced by the testes.

Testosterone maintains the capacity for male sex drive

The medial preoptic area of the hypothalamus is a crucial part of the central drive system for sex in male animals. Testosterone acts there in a rather prolonged way to enable neural activity to occur and sustain the drive.

Low testosterone men are generally capable of the mechanisms of sexual behavior, but have relatively little desire for it until injected with testosterone.

Causes and possible consequences of increased testosterone secretion

The amount of testosterone that men secrete into their blood is affected by psychological conditions.
Conditions that would seem to promote self-confidence tend to increase a man’s production of testosterone.
Pleasant social encounters with woman may also increase testosterone production in men.

Fluctuating levels of testosterone may affect a man’s aggressive and competitive tendencies more than sexual drive per se.
On average, men with naturally high testosterone levels are more aggressive and more interested in competition and status than are men with lower levels.
Injections of testosterone can increase indexes of aggressiveness and competitiveness in men.
High status and dominance is one route by which men attract women, so an effect of testosterone on competition and status seeking could be an indirect means toward increased sexual behavior.

Hormonal influences on female sex drive

After puberty, a female’s ovaries begin to secrete the female hormones estrogen and progesterone in a cyclic pattern over time. Producing the cycle of physiological changes referred to as the menstrual cycle in humans (and the estrous cycle in other mammals). This cycle controls ovulation. This cycle of hormones also influences sexual drive.

Effects of the estrous cycle in nonhuman mammals

In most mammals, female sexual drive and behavior are tightly controlled by the estrous cycle.
The female will seek out opportunities for mating and will copulate, only at that time in the cycle when she is ovulating.
Removal of the ovaries completely abolishes sexual behavior in most nonhuman female mammals. Injection of hormones can fully restore it.

(At least in rats) the ventromedial area of the hypothalamus plays a role in sexual behavior in the female analogous to that of the preoptic area in the male.
The cyclic variation in ovarian hormones acts on the ventromedial area to cause the cyclic waxing and waning of sexual drive.

Androgen refers to a category of hormones, including testosterone, which are produced by the testes in male and are normally thought of as ‘male hormones’. These hormones are also produced at lower levels by the adrenal glands, in females as well as in males.

Effects of the menstrual cycle in women

Human females exhibit still greater liberation of sexual behavior from cyclic hormonal control than do other primates.
Women can experience a high or low sex drive at any time in their hormone cycle.
In women, hormonal activation of the drive has been taken over largely by adrenal androgens.
The cycle still influences it to some degree.
Women are significantly more motivated sexually at the time in their cycle when they are fertile than at other times.

Arousability: the capacity to become sexually aroused in response to appropriate stimuli.
Proceptivity: the person’s motivation to seek out and initiate sexual activity, even when sexually arousing stimuli are nor already present.

Aurousability remains relatively constant for women over the course of the menstrual cycle, but proceptivity increases during the fertile period.
The increased proceptivitiy might result from the rise of estrogen and/ or progesterone during the fertile period, but it could also result from the rise of adrenal androgens.
Secretion of adrenal androgens, especially testosterone, increases markedly during the fertile stage of the menstrual cycle.

Sexual differentiation and determinants of sexual orientation

Sex hormones influence the sexual drive and behavior through two different kinds of effects in the brain.

• Activating effects
  Occur around the time of puberty and after, when hormones work on already-developed brain structures to prime, or activate, sexual drive.
• Differentiating effects
  Occur before and (in some species) immediately after birth and cause the brain to develop in male or female direction. They are responsible for the biological differences between males and females in sexual drive and orientation.

Brain-differentiating effects of the early presence or absence of testosterone

The only initial difference between the two sexes, in all mammals, is that females have two X chromosomes and males have a small Y chromosome in place of the second X.
A specific gene on the Y chromosome causes the growth of testes from structures that would otherwise develop into ovaries. Before birth the testes begin to produce testosterone, which acts on the brain and other bodily structures of the fetus to steer development in the male direction. The rudimentary genitals of the fetus develop into male structures (penis and scrotum) if testosterone is present, and they develop into female structures if testosterone is absent.
The testes in turn produce mullerian inhibiting substance, which inhibits the male fetus’s mullerian ducts from developing into female reproductive tissue. Early testosterone also promotes the development of brain pathways involved in the male sex drive and inhibits the development of brain pathways involved in the female sex drive.

In order to produce these brain-differentiating effects, testosterone must at within a critical period in the animal’s development. In humans this period ends before birth. The critical period for testosterone’s effect on the brain is later than that for its effects on the genitals.
Because of this difference in timing of critical periods, manipulation of hormones at the appropriate time van produce animals that have genitals of one sex but the brain structures and behavior of the other sex.

Female hormones are produced by pregnant females at high levels and get into the tissues of all fetuses. So a male hormone plays the key role in early sexual differentiation in mammals.

Falling in love

Sex among humans is often accompanied by romantic love or ‘falling in love’.
Falling in love is universal and associated with strong emotions.
Romantic love is not necessary for sex to occur, but it often increases tis likelihood. It also serves to form a bond between lovers.
Human pair bonding evolved as females required increasing protection and resources to care for their slow-developing offspring.
It also became in men’s best interest to support their mates and their mates’ children if they expected to pass along their genes to any grandchildren. The survival of their dependent offspring is greatly benefited by paternal support.
As a result, it became in both men’s and women’s best genetic interest to work together to rear their offspring. Falling in love is one mechanism to get this process started.

Falling in love involves three primary emotional systems that evolved to support mating, reproduction and parenting:

• Lust
  Driven in both men and women primarily by androgen hormones.
  It is not love, nor does it promote long-term attachment.
  Men with high levels of testosterone are less likely to marry.
  Becoming sexually excited.
• Attraction
  Synonymous for romantic love.
  Characterized by the strong emotions described earlier such as exhilaration, increased energy and loss of appetite.
  Associated with an increase in the neurotransmitter dopamine (high levels of which are related to heightened attention, motivation, goal-directed behaviors, euphoria, and increased mental activity)
  Also associated with increased levels of norepinephrine (associated with more acute memory for new stimuli and events.
• Attachment
  The male-female bonding
  Express feelings of closeness, security, anxiety when separated from one’s partner for an extended length of time, and mild euphoria when with one’s partner.
  This feelings are associated with hormones vasopressin and oxytocin. These are the same hormones that are released during sexual intercourse and are also with infant-mother attachment.
  Facilitates long-term relationships necessary to rear children.

People of all ages show basically the same behavioral and physiological reactions when they fall in love.
The mechanisms responsible for falling in love in adolescence and young adulthood seem to operate across the entire life span.

Effects of genes and prenatal environment on sexual orientation

Sexual orientation has at least three components

• Sexual/ romantic attraction, or arousal
  To which sex do people feel most attracted
• Sexual behavior
  With which sex do people have voluntary sexual acts
• Sexual identity
  How do people describe themselves?

These components are not always highly correlated with one another, so depending on which one component one uses, rates of same-sex orientation can vary greatly.

Bisexuality is greater in women than in men.

Genetic differences among individuals play a significant role in determing sexual orientation, but not the sole role.
Studies reveal that roughly 50 percent of the genetically identical twin brothers and sisters of gay and lesbian adults also have same-sex orientation. Compared with about 25 percent of the same-sex nonidentical twins or non-twins siblings
of gay and lesbian adults.
If sexual orientation were completely determined by genes, 100 percent of the identical twin brothers and sisters of gays and lesbians would have a same-sex orientation.

Studies suggest that sexual orientation might be affected by a variety of prenatal environmental factors (ranging from prenatal stress to certain medications taken by the mother during pregnancy) that alter the amount of testosterone or other androgens available to the fetus’s brain during a critical period in development.
Such work suggest that a high level of androgen action during the critical period may promote the development of brain mechanisms that predispose sexual attraction toward women and not toward men. A lack of androgen during the same period may promote the opposite.

The single most consistent, nongenetic influence on sexual orientation discovered to date is the fraternal birth-order effect on male homosexuality.
The more older brothers a man has, the greater the likelihood that he will be gay.
A couple’s first son has a 2.0 percent chance of being gay, the second 2,6 percent to 6.0 percent to the fifth son.
The number of older sisters a man has plays no role in the likelihood of his being gay, and there is no birth-order effect on sexual orientation of women.
For boys adopted, same-sex orientation increased with the number of older biological brothers, not the number of older adoptive brothers.
The most fully developed current hypothesis is that there is a ‘maternal memory’ for male gestations or births. Having a male fetus alters a woman’s immune system. Male fetuses are interpreted as foreign to a woman’s body and as a result she develops some male antibodies, which in turn affects subsequent male fetuses.

Possible effects of experiences, after birth, on sexual orientation

Recent research has revived the idea that experiences in life can affect sexual orientation, especially for women.
In general, women appear to be more flexible in their sexual orientation than men.
Because women are capable of sexual arousal to either men or women, they are more capable than are men of switching their sexual orientation at any time in life.
Women are more likely than men to report that their sexual orientation is a choice, and they are more likely than men to change their sexual orientation in response to events that occur in their lives. But some lesbians are more flexible in their sexual orientation than are others.

The sleep drive

Sleepiness operates in some ways like a regulatory drive.
The longer one goes without satisfying the sleep drive, the stronger the drives becomes.

Unlike other regulatory drives, it is not clear what the sleep drive regulates, except sleep itself.

Description of sleep as a physiological and behavioral state

Sleep is a condition of relative unresponsiveness to the environment.
Scientist who study sleep must focus on physiological and subtle behavioral changes.

The most valuable index of sleep is based on the electroencephalogram (EEG).

EEG waves accompanying wakefulness and stages of sleep

When a person is relaxed but awake, with eyes closed and not thinking of anything in particular, the EEG typically consists of large, regular waves called alpha waves, which occur at a frequency of about 8 to 13 cycles per second.
These relatively slow waves stem from a synchronized pulsing of neurons in the thalamus and cerebral cortex that occurs in the absence of focused mental activity or emotional excitement.

When a person concentrates on an external stimulus, or tries to solve a problem or becomes excited, the EEG pattern changes from low-amplitude, fast, irregular waves called beta waves.
The low amplitude indicates that neurons are firing in an unsynchronized manner, such that their contributions to the EEG tend to cancel one another out

When a person falls asleep, the EEG goes through a fairly regular sequence of changes. Four sleep stages:

1. A brief transition stage, when the person is first falling asleep.
2 -4 are successively deeper stages of sleep.

As sleep deepens, an increased percentage of the EEG is devoted to slow, irregular, high-amplitude waves, delta waves.
These waves are controlled by neurons in the thalamus that respond in an oscillating manner and synchronize the activity of billions of neurons in the cerebral cortex.
Corresponding to the EEG change, muscle tension, heart rate, and breathing rate decline. The person becomes increasingly hard to awaken.

Cyclic repetition of sleep stages through the night

Having reached stage 4, a person does not remain there for the rest of the night. After about 80 to 100 minutes of total sleep time, sleep rapidly lightens returning through stages 3 and 2. Then fascinating stage of sleep appears for a period of about 10 minutes or more.
During this new stage the EEG is unsynchronized, looking like the beta wave of alert wakefulness. Consistent with the EEG, other indices of high arousal are apparent: breathing and heart rate become more rapid and less regular, penile erection occurs in males, twitching movements occur in the small muscles of the fingers and face and the eyes move rapidly back and forth and up and down under the closed eyelids.
These eye movements give this stage of sleep its name, rapid-eye-movement sleep. REM sleep.
During REM sleep most dreams occur.
REM sleep is also sometimes called emergent state 1, it marks the onset of a new sleep cycle.
Stages 2,3 and 4 are referred to collectively as non-REM-sleep.

In a typical night’s sleep, a person goes through four to five sleep cycles, each involving gradual descent into deeper stages of non-REM sleep, followed by a rapid lightening of non-REM sleep, followed by REM sleep.
Each cycle takes about 90 minutes.
The deepest non-REM sleep occurs in the first cycle or two. With each successive cycle, less time is spent in the deeper stages of non-REM sleep, and more time is spend in light non-REM sleep and REM sleep.

Dreams and other mental activity during sleep

A true dream: experienced as if it were a real event rather than something merely imagined or thought about.
A true dream usually involves a progression of experiences, woven into a somewhat coherent through often bizarre story.
The more time the sleeper spends in REM sleep before awakening, the longer and more elaborate is the reported dream.

Essentially everyone dreams several times a night.

Generalities about dreams:

• Most dreams are about people, objects and activities that are well known and meaningful to the dreamer. But a few dreams are repetitions of events that actually happened in the dreamer’s daytime experience.
• Most dreams involve emotions, especially negative emotions (those are more common).

People who are awakened during non-REM sleep report some sort of mental activity just before awakening roughly half the time. This is sometimes of true dream, but more often of sleep-thought.

Sleep thought
Lacks the vivid sensory and motor hallucinations of true dreams and is more akin to daytime thinking.

A major difference between sleep thought and daytime thought is that the former is usually ineffective. No real progress is made.

During sleep, the eyes are closed, but all of the other sensory channels remain open.
The sleeping person’s brain sorts out sound by meaning to some degree.

Mental activity during sleep is quickly forgotten (not always). Such forgetting prevents us from carrying around thousands of bizarre and confusing memories or of mixing up real events with dreamed ones.

Theories about the functions of sleep

The preservation and protecting theory

Derives primarily from comparison of sleep patterns across different species of animals.
It posits that sleep came about in evolution to preserve and protect individuals during that portion of each 24-hour day when there is relatively little value and considerable danger in moving about.
An animal needs only a certain number of hours per day to do the thing that are necessary or useful for survival, and the rest of the time, according to this theory, it’s better off asleep. Quiet, hidden and protected from predators and other possible dangers.
Support: variations of sleep time among different species do not correspond with differences in physical exertion while awake. They do correspond with feeding habits and ways of achieving safety.
Animals that rely in vision generally forage during the day and sleep at night.
Infants who are being cared for by adults do not need to spend time foraging and sleep protects them from wandering away into danger. Their sleep also gives caregivers an opportunity to rest or attend to other needs.

The body-restoration theory

The theory that most people intuitively believe.
The body wears out during the day and sleep is necessary to put it back in shape.
Support:
Sleep time is a time of rest and recuperation.
Prolonged complete sleep deprivation in rats results in breakdown of various bodily tissues, leading within about 3 weeks to death.
Small mammals need to maintain a higher overall level of metabolism than do large mammals because they lose body heat rapidly, and higher metabolism leads to greater wear and tear on bodily tissues.

The brain-maintenance theory of REM sleep

REM sleep provides regular exercise to groups of neurons in the brain.
Synapses can degenerate if they go too long without being active, so neural activity during REM sleep may help preserve important circuits.
Support:
The longer a person sleeps, the greater is the proportion of sleep time spent in REM sleep.
In the REM sleep of the fetus, REM sleep is accompanied by body movements such as kicking and twisting, which are apparently triggered by the burst of activity in motor areas of the brain. So muscles as well as brain circuits are exercised.

Do dreams have functions?

Nobody knows if the dreams that accompany REM sleep serve useful functions. 

One theory:
Founded on the observation that dreams so often involve fearful and negative emotions. The theory is that dreams somehow provide a means of rehearsing and resolving threatening experiences that either have happened or could happen in the person’s real live.

Other theory
Dreams are side effects of the physiological changes that occur during REM sleep.
Neurons in visual and motor areas of the brain become active during REM sleep and hallucinations of sight and movements may be an inevitable consequence of such activity.
Neurons involved in memory retrieval and emotions also become active, and these may bring familiar images and strong emotional feelings into the sleeping person’s mind.
In research done in 1960’s, electrical stimulation in portions of the cerebral cortex produced dream-like hallucinations in people who were awake.
Because of reduced mental captivity during sleep, the story of the hallucination is less logical than one the awake brain would develop, but it still contains some degree of logic.

Even if dreams are triggered by random events in the brain, the actual images, emotions and story lines of the dream are not random.
They contain elements based on the dreamer’s experience, and because they occur at a time of reduced mental capacity, ideas of feeling that are normally suppressed by higher mental processes could emerge and perhaps be useful in psychoanalysis.

Individual variations in the sleep drive, and effects of failure to satisfy that drive

The sleep drive varies from person to person.

Nonsomniacs; people who sleep much less than most of us and yet do not feel tired during the day. (Very rare)
Nonsomnia is compatible with physical and psychological health. This adds to the evidence that only a relatively small amount of sleep is needed for body repair and growth of new synapses in the brain.
Yet, most of us need 8 hours of sleep to function well. We need this because we have a sleep drive that overwhelms our mind and makes us tired.

Insomniac
Someone who has a normal drive for sleep but who, for some reason, has great difficulty sleeping at night. (Relatively common).
Unlike a nonsomniac, an isomniac feels tired during the day as a result of not sleeping. And so do people who voluntarily reduce their sleep.

Brain mechanisms controlling sleep

Sleepiness, unlike other drives, is actively promoted by neural mechanisms located in the hypothalamus and in brain areas closely connected to the hypothalamus. There are several of such mechanisms.

Rhythm-generating neurons in the hypothalamus control the daily cycle of sleepiness

In all vertebrates the sleep drive waxes and wanes in a cyclic manner over the 24 hours day. This continues even in a ‘time free’ environment.

Circadian rhythm
The technical term for any repetitive biological change that continues at close to a 24-hour cycle in the absence of external cues. 
The clock that controls the circadian rhythm of sleep in all mammals is located in a specific nucleus of the hypothalamus called the suprachiasmatic nucleus.
This nucleus contains rhythm-generating neurons that gradually increase and decrease their rate of action potentials over a cycle of approximately 24 hours even when surgically isolated from other parts of the brain.

In addition of controlling sleepiness, the suprachiasmatic nucleus also controls a daily rhythm of body temperature and of certain hormones.
The hormone that is most directly locked to the circadian clock is melatonin.
Melatonin is produced by the pineal gland, begins to be secreted into the bloodstream in the evening, typically about 2 hours before a person is ready to fall asleep, and is secreted at relatively high levels until approximately the time when the person is ready to awaken naturally in the morning.

Input from the eyes synchronizes the hypothalamic clock to the light-dark cycle

Under normal conditions, the circadian clock is synchronized with the 24-hour day by the regular waxing and waning of daylight, so rhythms occur in periods of exactly 24 hours.
This cycle can be lengthened and shortened, by as much as a couple of hours either way, by artificially changing the period of light and dark. The cycle can be reset trough exposure to bright fluorescent light.

Foundations for understanding emotions

Much of our thought and behavior is tinged with emotion.

The nature and value of emotions

An emotion is a subjective feeling than is mentally directed toward some object.
Self-conscious emotions all depend on an individual’s self-awareness (like embarrassment).
Other-conscious emotions are related to the expectations and opinions of other people for one’s behavior. These emotions (mature forms of which are not seen until late in the second year of life) seem to require a sophisticated cognitive system.

The feeling associated with emotion, independent of the object, is referred to as affect. Such feelings can vary along two dimensions:

• The degree of pleasantness of unpleasantness of the feeling
• The degree of mental and physical arousal

An emotion depends on the object as well as the feeling. (So the feeling of pleasure may be experienced as the emotion pride when the object is oneself and as the emotion love when the object is someone else).

Emotional feelings are not always attached to objects.
In that case, if it last for a sufficiently long period, it is referred to as a mood.

Emotions have several components, beginning with behavioral expression.
We have the ability to regulate emotions.
We also can recognize emotions by people’s voice or body language.
Emotions are not independent of cognitions. The same physiological arousal may represent different emotions depending on how we interpret the situation.

How many emotions are there?

This depends of how finely graded a taxonomy (system of classification) we wish to create.

One useful classification:
Eight primary emotions, which can be arranged in four pairs of opposites:
Joy and sorrow, anger and fear, acceptance and disgust, surprise and expectancy
These primary emotions can mix with one another in any number of ways to produce an essentially infinite variety of different emotional experiences.

Emotions serve adaptive functions

Emotions must have come about through natural selection because of their adaptive value.
Emotions are universal and have species-specific adaptive functions, reflected by facial expressions (Darwin). Each emotion confers some adaptive benefit to the individual person or animal expressing them.
The belief that basic emotions are innate and associated with distinctive bodily and facial reactions is referred to as discrete emotion theory.

The motivating qualities of emotions
Emotions motivate us to approach objects that can help us and to avoid or repel objects that hinder us in our efforts to survive and reproduce.

Emotions promote our survival and reproduction through their capacity to communicate our intentions and needs to others.
Self-conscious emotions are of critical importance for successful social life.
Nearly all social interactions involve emotion. Our social situations affect our emotions and our emotions affect our behavior.

Facial expressions of at least some emotions may server more than communicative value: they may be part of the body’s way of dealing with the emotion-arousing situation. (Like fear which involves widening of the eye and opening of the nasal passages which increases the field of vision and the sensitivity of odors).

The effects of bodily responses on emotional feelings

Most emotional states are accompanied by peripheral changes in the body. These are all changes in the body outside of the central nervous system. (Like heart rate or activation of certain glands).
The changes, overall, are adaptive because of their communicative function or their role in helping prepare the body for possible action.

James’s peripheral feedback theory of emotion

The bodily reaction to an emotion-provoking stimulus is automatic, occurring without conscious thought or feeling. The assessment of one’s emotional state comes later and is based on the perception of the bodily state.

Schachter’s cognition-plus-feedback theory

The feeling of an emotion depends not just on sensory feedback pertaining to the body’s response, but also on the person’s perceptions and thoughts (cognitions) about the environmental event that presumably evoked that response.

The perception and thought about the environment influence the type of emotion felt, and sensory feedback about the degree of bodily arousal influences the intensity of the emotion felt.
Highly physiological arousal increases emotion only when people believe that the arousal is caused by the external situation.

Influence of facial feedback on emotional experience

Sensory feedback form facial expressions contributes both to emotional and to the production of the full-body reactions that accompany emotions.

Induced facial expressions not only alter self-reports of emotion, but also can produce physiological responses throughout the body that are consistent with the induced expression.

Different patterns of arousal accompanied different emotions, but the pattern of a given emotion was the same whether the person has been asked to relive that emotion or simply to move certain facial muscles.

Brain mechanisms of emotion

The brain is the center both for producing the bodily changes and for experiencing emotional feelings.
Research on the brain’s emotional systems has focused particularly on two structures:

• The amygdala
• The prefrontal portion of the cerebral cortex

The amygdala assesses the emotional significance of stimuli

The amygdala is a cluster of nuclei buried underneath the cerebral cortex in the temporal lobe. It is a part of the limbic system.
This structure is the brain’s early warning system.
It receives stimulus input from all of the body’s sensory systems, preforms continuous, rapid assessments of that input, and alerts the rest of the brain and body if it judges that some sort of whole-body or behavioral reaction may be called for.

The amygdala receives sensory input by way of two routes.

• A very rapid subcortical route
  It analyzes incoming information before that information has been processed by sensory areas of the cerebral cortex.
• A somewhat slower cortical route.
  It analyzes in more detail information that has been processed by the cerebral cortex.

The amygala sends it output to many other brain structures.
Through this outputs it alerts the rest of the brain to pay attention to the stimulus of concern, and it generates such bodily reactions as increased heart rate and muscle tension.

The amygdala may be activated by stimuli that induce positive emotions, and may be more generally involved in processing the relevance of stimuli both positive and negative.

Sensory areas of the cortex are essential for conscious perception of stimuli, but not for unconscious emotional responses for them.
The fact that emotional responses can be generated by subcortical pathways to the amygdala helps explain why our emotions are often irrational and so difficult to control though conscious reasoning.

The prefrontal cortex is essential for conscious experience of emotion

The amygdala is essential for unconscious emotional responses.

The prefrontal cortex is essential for the full conscious experience of emotions and the ability to act in deliberate, planned ways based on those feelings.

The prefrontal cortex receives input from the amygdala and from the somatosensory cortex. Such input provides it with information about the amygdala’s assessment of the stimulus and the body’s state of arousal.

Research suggest that the two cortical hemispheres are involved in processing different emotions.
Right prefrontal cortex: responses that entail withdrawal, or moving away from the emotional stimulus.
Left prefrontal cortex: responses that involve approach, or moving toward the emotional stimulus.