Truth Saves - Human Brain

Brief Introduction to the Brain

People commonly picture the human brains as "part of us" when in fact we are a part of it. Everything that makes us who we are, including our consciousness, resides within our brain and are 100% dependent on the physical structure of our brain. Any physical alterations to sections of the brain changes our personality, way of thinking, emotions, memory and who we are.

Quick Links
• Thinking & Intelligence
• Split-Brain
• Movement & Freewill
• Memory
• Emotions
• Personality
• Belief & Superstition
• The Developing Brain
• Evolution of the Brain

Thinking & Intelligence

Intelligence refers to the ability to learn about, learn from, understand, and interact with one's environment. It embraces many different types of skills, such as physical dexterity, verbal fluency, concrete and abstract reasoning, sensory discrimination, emotional sensitivity, numeracy, and also the ability to function well in society.

The Brain's Superhighway

The frontal lobes have long been considered the seat of intelligence since damage to them affects the ability to concentrate, make sound judgements, and so on. Yet frontal-lobe damage does not always affect a person's IQ, so other brain areas must also be involved. Recent research suggests that intelligence relies on a neural "superhighway" that links the frontal lobes, which plan and organize, with the parietal lobes, which integrate sensory information. The speed and efficiency with which the frontal lobes receive a stream of ready-to-use data via this route may affect IQ.


	Why we can't do two things at once If you try to do something while still working on a previous task, your brain stalls. This may be because the prefrontal cortex, which disengages attention from on task and switches it to another, cannot do so instantly, resulting in a short "processing gap." The brain is also unable to do two similar things simultaneously because the tasks compete for the same neurons. For example, listening to speech while reading words activates overlapping brain areas, so it is difficult to achieve, but listening to a speech while looking at landscape is easy.

Location of Intelligence

There are regions in both sides of the brain (orange) as well as areas in the left hemisphere only (blue) that are strongly associated with intelligence and reasoning. The arcuate fasciculus (green), a think bundle of nerve fibers, provides a neural link between the parietal and frontal lobes.

Making Decisions

Intelligence is largely the ability to make sensible decisions, which involves calculating pros and cons. First, the brain assesses the "goal value" - the reward expected as a result of the decision. Next, it calculates the "decision value" - the net outcome, or the reward minus the cost. Finally, the brain makes a prediction of how likely it is that the decision will deliver the reward envisaged. The more complex the problem, the more the frontal areas of the brain are involved.

Activity in the medial orbitofrontal cortex correlates with goal values (red); activity in the central orbitofrontal cortex (yellow) correlates with decision values; and activity in the ventral striatum, part of the caudate nucleus and putamen, correlates with prediction errors (green).

The Creative Process

Our brains are continuously bombarded with stimuli, most of which are ignored. This "shutting out" ensures we use the most relevant information to guide our thoughts. Opening our minds to new information kicks off the creative process. This happens when the brain relaxes out of sharp attentiveness into "idling," which is characterized by slow, relaxed alpha waves. In this mode, stimuli that might otherwise be ignored enter awareness and resonate with memories, generating new thoughts and ideas that may be both novel and useful.

Split-Brain

The right hemisphere (RH) is our artistic half and is used when drawing, imagining and dealing with shapes. The left hemisphere (LH) is our logical half and is used during verbal communication, writing, counting and dealing with sequences. Also, the RH is connected to our left eye and hand while the LH is connected to our right eye and hand. The two hemispheres of our brains are linked by the corpus callosum, through which they communicate and coordinate.

A split-brain patient is one who has had their corpus callosum cut preventing communication and interaction with our two hemisphere. Such a process is done to cure violent cases of epilepsy. When a split-brain patient stares at the center of a screen visual information projected on the left side goes to the patients RH and vice versa. When the patient is asked what he saw on the left he is unable to verbally say what he saw but he can draw the answer. When asked what he saw on the right side he can only verbally say what he saw.

Movement & Freewill


	Damage to the rear of the left parietal lobe gives rise to a condition of ideomotor apraxia . People have difficulty making movements and gestures. The problem is less severe for the use of concrete objects ("Show me how to use a hammer."), especially if the object is actually present.

	It is most severe for symbolic gestures, such as greeting or saluting. Particularly when these have to be performed outside their normal social context. What is lost is the ability to make voluntary movements that are not prompted by the environment.

Free Will & the Frontal Lobes

When Penfield stimulated the motor cortex of conscious surgical patients, they assured him that they experienced their consequent movements as involuntary, not willed. When asked why they just lifted their arm patients would reply, "I didn't, you did." The motor cortices are at the back of the frontal lobes. Their role is to initiate execution of cortically generated movements, as opposed to movements generated sub-cortically or spinally. But Penfield's patients bear eloquent witness that they are not the seat of the will.

Responsive Movements

Forward of premotor and supplementary cortex lies the prefrontal cortex. This area has many incoming and outgoing connections. The upper and lower visual pathways from the parietal and temporal lobes terminate here.

In front of the motor cortex are the premotor cortex and supplementary cortex. These areas select movements that the motor cortex will execute. Premotor cortex selects movements in response to external triggers, as when you rise from your seat in response to the phone ringing or dial a number read from the phone book. Supplementary cortex selects movements in response to internal triggers, as when your rise from our seat in response to feelings of discomfort or dial a phone number from memory.

Frontal Lobe Damage & Unwanted Responses

Failure to inhibit unwanted responses also shows up in environmentally driven behavior. Individuals with frontal lobe damage often react to stereotyped ways to objects they encounter, however socially inappropriate the setting. Seeing a toothbrush, they may pick it up and use it, even though it belongs to someone else and they are not in a bathroom. Entering someone's home, they may overtly inspect the pictures on the walls, commenting upon them and pricing them as though in a gallery. When the inappropriateness of their behavior is pointed out, they may become confused or confabulate fantastic explanations of their actions.

Memory

Our memory is the re-creation of past experiences by the synchronous firing of neurons that were involved in the original experience. The subsequent combined firing of the neurons reconstructs the original expericne, producing a "recollection" of it. The act of recollecting makes the neurons involved even more likely to fire again in the future, so repeatedly reconstructing an event makes it increasingly easy to recall.

5 Types of Memory

Episodic: Comprises reconstructions of past experiences, including sensations and emotions; these usually unfold like a moive and are experienced from one's own point of view.

Semantic: Non-personal factual knowledge that "stands alone."

Working: The capacity to hold information just long enough to use it.

Procedural: Comprise learned actions such as walking, swimming or riding a bicycle.

Implicit: Memories we don't know we have. They affect our actions in subtle ways; for example you might take an inexplicable dislike to a new person because they remind you of someone nasty.

Learning Is Good For You

Learning involves making new connections between clusters of neurons in different parts of the brain. This builds up the brain, making it fitter. For example, practicing spatial skills such as finding your way around a city has been shown to increase the size of the rear hippocampus. The more connections you create the better you can use what you learn and the longer it takes you to forget it.

FORMING MEMORIES

The initial perception of an experience is generated by a subset of neurons firing together. Synchronous firing makes the neurons involved more inclined to fire together again in the future which recreates the original experience. If the same neurons fire together often they eventually become permanently sensitized to each other, so that if one fires the others do as well.		1 INPUT An external stimulus triggers two neurons to fire simultaneously. In future, if one fires, the other is likely to fire too.

2 CIRCUIT FORMATION A third neuron fires. One of the initial pair is stimulated to fire with it, triggering the second, so the three become linked.		3 INCREASING ACTIVITY The three neurons are now sensitized to one another, so that if one fires, the other two are likely to fire as well.

Just like a computer, if you remove the physical memory storage device you an no longer store new information.

Importance of the Hippocampus

In 1953 surgery was performed on a patient known as HM to relieve the symptoms of severe epileptic seizures. The operation involved removing a large part of the hippocampus. This controlled the seizures but it also produced a severe memory loss. From the time HM woke up from the operation he was unable to lay down conscious memories. Day-to-day events remained in his mind for only a few seconds or minutes. When he met someone could not recognize them no matter how many times they have met before. HM also believed himself to be a young man right into his eighties because the years since his operation did not effectively exist for him. His case shows how essential the hippocampus is for our memory.

Location of Memories

Although the Hippocampus is used to lay down our memories, memory is stored throughout the brain by the neurons that created them. Groups of neurons in the visual cortex will encode a sight and neurons in the amygdala will store an emotion. The hippocampus pulls them all together. The simultaneous firing of all these groups constructs the memory in its entirety.

Emotions

Emotions may seem to be conscious feelings but they are in fact "inner motions" - physiological responses to stimuli - which push us away from danger and toward reward. Emotions are actually generated constantly but much of the time we are completely unaware of them.

Emotions are generated in the limbic system which initially evolved very early in mammalian history for evaluating smells. Each emotion results in the release of hormones that produce physical reactions such as increased heart rate and muscle contraction.


	Unconscious Emotion We have evolved a conscious emotional system but we retain the primitive, automatic emotional responses. A frightening sight or sound registers in the amygdala before we are even conscious of it. While the sensory information is sent to the cortex to be made conscious, the amygdala is already sending messages to the hypothalamus, which triggers changes that ready the body a physical reaction. This allows us to take instant action to save ourselves instead of waiting for instructions from our conscious mind. When we are startled by a loud noise, then relax after realizing it is harmless, we are experiencing both stages - the unconscious reaction followed by the conscious response.


	Positive Emotion Limbic system structures next to the amygdala are involved in feelings of pleasure, mainly by reducing activity in the amygdala and in cortical areas concerned with anxiety.

Personality

Many different personality traits have been linked to specific patterns of activity in the brain, some of which are linked to the expression of certain genes or particular genetic mutations. For example, a person who produces more excitatory neurotransmitters is less likely to feel the need to seek thrills than someone who needs a lot of stimulation to experience the same level of excitement.

Extroversion	Extroverts have reduced activity, in response to stimuli, in the neural circuit that keeps the brain aroused (shown here). As a result, they need more environmental stimuli to keep them feeling energized.
Aggression	People with a version of a gene previously linked to impulsive violence show abnormally reduced volume and unusually low activity in the cingulate cortex - an area concerned with monitoring and guiding behavior.
Social Behavior	Socially secure people have a stronger response to friendly looking people in the striatum - an area concerned with reward - than shy people. Avoidant types show a stronger reaction in the amygdala to unfriendly looking people.
Novelty Seeking	People who like novelty may have better connections between areas shown here. The hippocampus sends signals to the striatum - which registers pleasure - when it identifies an experience as new.
Cooperation	Cooperative people show increased activity in the insula if they think their treatment is unfair. Uncooperative people do not register unfairness to the same extent, suggesting an underdeveloped sense of trust.
Optimism	Optimism is linked to enhanced activation in the amygdala and in the anterior cingulate cortex when imagining future events relative to negative ones.

Belief & Superstition

Our brains are constantly trying to make sense of the world in order to guide our actions. One way of doing this is by creating explanatory stories or ideas into which we fit our experiences. Such frameworks are often useful, but may not always be correct.

Religion in the Brain

Religious practice is largely determined by cultural factors. However, studies of identical twins who have been brought up separately suggest that genes also play a part in the likelihood of a person experiencing a religious conversion or spiritual transcendence. Spiritual transcendence shares some features with other "weird" experiences, such as out-of-body experiences, auras, and sensing the presence of spirits or ghosts. These are associated with flurries of unusually high activity in the temporal lobes.

Rigid belief systems can lead people to "see" things that do not exist. During the Salem witch trials of 1692, for example, religious bigots "saw" evidence of the devil in the behavior of entirely ordinary people.

Believing Is Seeing

Most people have some kind of belief system which forms a framework for their experiences. Some were taught their beliefs, while others arrived at them by examining their experiences and working out their own interpretations. Once a belief system has been formed, it acts both as an explanation for what has happened in the past and also a "working hypothesis" that is projected onto the world. For example, if a person believes that the world is governed by a benign supernatural being, they will "see" events such as coincidences or strokes of good fortune as evidence of this, while a person with a rational based belief system would interpret them merely for what they are, chance happenings. People who are quick to see meaningful connections between, for example, random events are more inclined than others to have a magical or superstitious belief system.

Pattern Making

The ability to "see" patterns helps us make sense of the world and respond appropriately. But we can be both too good and too poor at it.


	Autism Autistic people do not see patterns that are obvious to most of us, so they get swamped by information, all of which seems equally.


	Literal-mindedness Failure to recognize subtle patterns leads to concrete-mindedness, such as failure to understand metaphors (as seen in Asperger's syndrome).


	Superstition Too much pattern-making may lead people to "see" things that are not there, or make links between events that are not actually connected.

The Developing Brain

The formation of the highly complex human brain from a simple ball of cells is a remarkable process that takes many years to reach its full potential in terms of sensory, motor, and intellectual skills, although development does not occur at an even pace, it does follow a fairly predictable sequence.

Conception to Birth

In the days following conception, the embryo is just a minute ball of cells. Development of the brain and nervous system starts three weeks, with differentiation of cells to form the neural plate along the back (dorsal) part of the embryo; this broadens and folds to form the liquid-filled neural tube, which will become the brain and spinal cord. The brain starts to develop at about four weeks as a tiny bulb at the upper end of the neural tube, while the lower part begins to form the spinal cord. The main sections of the brain, including the cerebral cortex, are visible within seven weeks. During the next several weeks, the brain continues to grow and develop.


Physical And Motor Skills Babies are born able to perform basic reflex actions such as grasping. By a process of trial and error, they gradually acquire other physical skills and develop motor coordination. Initially, babies master control of their body posture and head, then go onto develop physical skills such as crawling, standing, and walking.
Vision And Manual Dexterity A newborn baby can only see clearly up to about a yard away. Vision gradually improves, and after about six months objects several yards away are clear. With the improvement in vision, and also with the continuing maturation of the motor system, dexterity and hand-eye coordination develop.
Social Skills And Language Within a few weeks of birth, a baby turns toward sounds and also starts to squeal and smile spontaneously. As the baby hears language, he or she starts to associate words with objects, and may start to say "dada" and "mama" to the parents as early as about nine months of age. Social skills improve rapidly as the ability to communicate develops.

The Aging Brain

The traditional view of aging is that the brain and body start to degenerate. This is true in that neurons are lost and, for those that remain, impulses are transmitted more slowly. This can lead to slowing thought process, memory problems, and deteriorating reflexes which can cause problems with balance and movement.

Natural Degeneration

In the past, it was rare for people to live to the age of 50 and beyond, so we have not evolved to use the brain in such advanced years. This makes the aging brain a relatively new phenomenon in human history and evolution. The natural degeneration of the brain and nervous system is not caused by disease, so it should not be confused with the pathology of dementia, which is associated with a pattern of specific brain changes. Recent research shows that most neurons actually remain healthy until you die, but brain volume and size decrease 5-10 percent from the age of 20-90. There are also changes in topography, with the grooves widening and tangles and plaques (small, disk-shaped growths) forming. However, the role of these deficits is not absolutely clear. They can occur in the brains of both healthy and sufferers of Alzheimer's disease.

Evolution of the Brain

Brains evolved to enable animals to respond to environmental changes. The human brain has evolved to its present complexity through several stages, many of which are common to all animals. Its origins can be seen in the brains of other species, in which more primitive structures remain.

Invertebrate Brain Evolution

Earthworm Brain
The earthworm has a crude brain, the cerebral ganglion, which is connected to a cord of nervous tissue (the ventral nerve cord) that runs the length of its body. Nerve fibers from the cord extend into each segment, so muscle contraction along the body can be coordinated to produce movement in response to stimuli.

All animals have to respond to changes in their internal and external environment in order to survive. To do this, they have evolved cells that are sensitive to stimuli such as light and to vibrations. The sensory cells are, in turn, connected to other cells that can move the organism or change its state in response to the stimulus. This system of interconnected nervous tissue is a crude form of brain. In invertebrates, such as worms, the nervous system is distributed throughout the creature's body, as a loose network of reactive fibers. Some of these networks contain small masses of nerves, known as ganglia. These are the forerunners of the structures that, in some species, have become the central nervous system of the brain.

Primitive Nervous System
The simplest system, as seen in this hydra (a tiny aquatic invertebrate), consists of a loose network of sensory cells with clumps of interconnected cells called ganglia.

Vertebrate Brain Evolution

Through the course of evolution, the brain has undergone considerable changes. Compared to the primitive nervous system of invertebrates, the brain of vertebrates is a well-developed, highly interconnected organ. The central nervous system is connected to the rest of the body by a peripheral nervous system that includes the fibers running to and from the sensory organs. The basic vertebrate brain - also sometimes referred to as the "reptilian brain" - consists of the cluster of nuclei that lies just above the brainstem in humans. They include the modules that produce arousal, sensation, and reaction to stimuli. It is unlikely, however, that these nuclei alone are sufficient to produce consciousness. This basic vertebrate brain does not include more advanced features, such as the limbic system or cerebral cortex, which exists only in the brains of mammals.

brain evolution

Three Brains in One
Our brain has a "layered" architecture, with newer parts built on top of the earlier parts.

The first and most ancient, the R-complex (the R refers to reptiles), developed as an extension of the upper brain stem. This area influences our territoriality, mating, and aggression - our basic "survival brain."

Above the R-complex lies the limbic system (evolved with the earliest mammals), which produces our emotional states - our "feeling brain."

Our cerebral cortex is the thick, outer layer of our brain - our "thinking cap." With this new brain mass, we developed the traits that make us uniquely human.

Hominid Brains

The brains of hominids (modern humans and their ancestors) underwent a surge of evolutionary changes that left them, in some ways, distinctly different even from their near relatives, such as chimpanzees and gorillas. The main distinction between human and other mammalian brains is the size and density of the cortex, and particularly of the frontal lobe, which is responsible for complex thought, conscious judgement, and self-reflection. No one knows yet why the human brain evolved as it did - it may have been due to some change in diet forced by the environment, or the product of living in groups that depended on close interdependence for survival.

Sources include: The Human Brain Book by Rita Carter
Introducing Mind & Brain by Angus Gellatly & Oscar Zarate
The Way Life Works by Mahlon Hoagland & Bert Dodson - Three Rivers Press

Unconscious Emotion

Positive Emotion

Autism

Literal-mindedness

Superstition