CHAPTER
3

Bio Psycho What?

In This Chapter

“Let’s brainstorm.” “Watch it, you pea brain.” “She’s the brains behind it.” When we listen to the words we use, it’s clear we know who rules the roost when it comes to human behavior: the brain.

To understand human nature, we must first understand how the brain functions because there’s a biological counterpart to every thought or feeling we have. As you’ll see, physical changes in the brain can produce dramatic changes in human behavior.

After reading this chapter, you’ll be up to speed on the biological hardware that programs human behavior as we explore the parts of the brain that cause us to think, feel, and do the things we do. We also explore how they do it, how different parts of the brain communicate with each other and the rest of the body, and how hormones and other chemicals influence human behavior. So let’s get started at the real essence of psychology—the brain.

It’s Evolutionary

We’re all winners from an evolutionary perspective. The very fact that we exist means our ancestors possessed favorable characteristics that enabled them to adapt and flourish in their natural environment. They passed these advantageous traits on to the next generation, who passed them on to their children, and so on, until here we are. We’re the “fittest” in the “survival of the fittest.”

Adapting to Changes

Just imagine; there our struggling ancestors were, trying to adapt to their environment as best they could, and suddenly nature decided to play a joke or two. Resources became scarcer or the average temperature suddenly skyrocketed. These environmental shifts drastically changed which physical characteristics were favored.

In particular, two environmental adaptations assured us the highest place on the evolutionary totem pole, and of course, all humans share these things today. These adaptations were bipedalism, the ability to walk upright, and encephalization, which is the development of a larger brain. Encephalization led to an increased ability to reason, remember, and plan.

From a psychological standpoint, though, we’re more interested in what our evolutionary path means for brains living here and now. How do our brains help each one of us solve our problems, remember birthdays, and plan our future? To answer these questions, let’s take an inside look at the human brain.

INSIGHT

A neuropsychologist is a psychologist specially trained in the assessment and rehabilitation of brain damage. Neuropsychological assessment includes observation, a detailed personal history of the patient, and many specialized tests for memory, intelligence, and other functions. Unlike a CT (computerized tomography) or an MRI (magnetic resonance image), which give us a picture of what the brain looks like, a neuropsychological assessment tells us what a person can do after injury or disease strikes.

The Headquarters of Human Behavior

The brain contains more cells than there are stars in the universe. And each one works together to produce, direct, and choreograph what we think, feel, and do.

A Living Record of Time Travel

From the neck up, the brain is structured in the order in which it evolved. The brain stem, the bulb where the brain meets the spine, is the oldest part of the brain; the midbrain and higher brain evolved on top of it in much the same way newer buildings are constructed on the old foundations of an ancient city.

As with your brain’s structure, so developed the behavior each part of your brain controls. They, too, go from primitive to most sophisticated. The lower brain is responsible for aggression, territoriality, and rituals. The midbrain holds the limbic system, the seat of powerful emotions, sexual instincts, and the sense of smell. Over the top arches the cerebral cortex, the part of the brain that regulates higher levels of cognitive and emotional functioning. This is the site of reasoning, planning, creating, and problem solving, and it is the part that makes us human.

PSYCHOBABBLE

From a psychological standpoint, you can see why it can be challenging to use your reasoning and self-control to keep from acting on powerful feelings or strong desires. After all, those desires have been around much longer than your logic!

Hello Central!

The bottom-up approach reveals the human brain’s structural evolution inside each of us. Human behavior evolved from base instincts to thoughtful planning.

If the brain is the headquarters of human behavior, the cerebral cortex is unquestionably the commander in chief. Not only does it make up two-thirds of your brain, its job is to coordinate all the brain’s units. When we say “use your brain,” the cerebrum is the part we’re talking about.

Getting Your Brain Organized

Because our cerebrum plays such a big role in human behavior, the lower and middle portions of the brain often get overlooked. However, without these more primitive parts, you couldn’t survive long.

A quick rundown of the parts of the brain will give you a good sense of the way cognitive tasks are parceled out. Each part is a specialist:

brain stem    Regulates the internal physiological state of the body

medulla    Regulates breathing and the beating of the heart

pons    Regulates brain activity during sleep

reticular formation    Arouses the brain to attend to new stimuli even during sleep

thalamus    The relay station between senses and the cerebral cortex

cerebellum    Organizes physical balance and movement

limbic system    Regulates motives, drives, feelings, and some aspects of memory

hippocampus    The key player in long-term memory

amygdala    The tough guy, with roles in aggression, memory, emotion, and basic motives

hypothalamus    Regulates eating, drinking, sexual arousal, body temperature

cerebrum    Regulates higher levels of thinking and feeling

cerebral hemispheres    Each half controls different cognition and emotions

corpus callossum    Connects the two hemispheres, allowing them to communicate with each other

Left Brain, Right Brain

Do you prefer geometry or English? Would you rather be a painter or a writer? Are you creative or logical? Depending on how you answered, popular psychology would classify you as “right-brained” or “left-brained.”

PSYCHOBABBLE

This “left brain/right brain” craze started with the discovery that the two sides of the cerebrum have different processing styles: the right half sees things holistically, while the left is more logical. In addition, they divide up the work. Some functions are more under the control of the right hemisphere and some are more under the control of the left.

A Leftward or Rightward Slant?

For most people, the left brain is more involved in language and logic. The right half of the brain handles visual patterns and spatial relationships. Hence, painters are thought to be more “right-brained” and writers are thought to be more “left-brained.”

This division of labor holds true for our feelings as well. The left hemisphere is associated primarily with positive emotions while the right hemisphere is responsible for negative emotions like anxiety and depression. Given that painters and sculptors use their right hemisphere so much, maybe there’s something to the idea of a tortured artist!

Sports psychologists have put the “right brain/left brain” concept to good use. By teaching athletes to use both sides of the brain, they help them improve their performance. For example, tennis players naturally exercise their left brain every time they swing their tennis rackets. The series of steps that form a backhanded swing is a left-brain activity. However, players can also use their right brain to play tennis: lying awake at night, they can mentally practice their game. Tennis players who visualize the perfect swing in their mind’s eye and practice it are making creative use of the right hemisphere’s holistic processing. And it works!

Partners for Life

In reality, though, the popular left brain/right brain distinction is overly simplistic. These two halves of your brain are actually partners; they constantly talk to each other through a huge bundle of fibers that connect the two hemispheres, the corpus callosum. They also work in sync. For example, when you run into an acquaintance, your left hemisphere remembers his name and your right hemisphere recalls his face.

Oddly enough, the left cerebral hemisphere controls the movement on the right side of the body and the right hemisphere controls the left. When you write your name with your right hand, your left hemisphere is actually doing the work. Specifically, your left parietal lobe is busy—which brings us to the next topic of conversation: the four lobes that make up each hemisphere.

Meet the Mother Lobes

You have more lobes than the ones you hang your earrings on. Each half of your brain has four lobes—a parietal lobe, a temporal lobe, a frontal lobe, and an occipital lobe.

Front and Center

The frontal lobes, which sit just behind your forehead, are the newest additions to the human brain. They’re considered the “executive” part of the brain—the seat of purposeful behavior. They plan, make decisions, and pursue goals. They also inhibit or override more primitive behavior, such as calling your boss an idiot!

BRAIN BUSTER

Chronic pain is bad for your brain. In a healthy brain, when one region is neuronally active, the others are quiet. But a brain in constant pain gets stuck firing in a frontal cortex area associated with emotion, wearing out—and even killing off—neurons, and altering their connections to each other.

Temporally Speaking

Your temporal lobes sit directly behind your ears—convenient, since their job is to make sense of what you hear. The left temporal lobe enables you to understand speech. Your right temporal lobe helps you to understand music, the ringing of the telephone, and other nonverbal sounds. In neuropsychological terms, telling someone that she has an ear for music translates into saying she has excellent right temporal lobes.

Parietals Rule

Your parietal lobes sit at the top of your head and integrate sensory information from the opposite sides of your body: your left parietal lobe makes sense of information coming in from the right side of the body, and your right parietal lobe takes care of the left side. These lobes help you understand what you’re touching. When you reach into your purse or pocket, for example, your parietal lobes help you distinguish between a quarter and a dime just by the way they feel.

An Occipital Complex?

If you cup your hand on the back of your head, you are touching your occipital lobes. These lobes make sense of what you see; their primary job is to process visual information. So you do have eyes in the back of your head!

The left occipital lobe controls the right visual field in both your eyes, while the right occipital lobe controls the left visual field. To see how this works, hold your hands out in front of your face so that your palms are facing you. Now, draw an imaginary vertical line down the middle of each hand. The right visual field is the right half of each hand; the left visual field is the left half of each hand.

New research also suggests that we all have two visual systems that operate independently of each other. The visual system that shows you a coffee cup sitting on your desk isn’t the same one that guides your hand to pick it up. The first system, called “vision-for-perception,” enables you to recognize objects and build a “database” about the world. The other, less-studied, “vision-in-action” system provides the visual control you need to move about and interact with objects.

INSIGHT

Read Oliver Sacks’s The Man Who Mistook His Wife for a Hat for a close look at the impact of brain disorders on everyday life. The title of this book comes from one of Dr. Sacks’s patients, whose inability to recognize faces caused him to mistake his wife’s head for a hat; as a result, he attempted to pick it up off her shoulders!

These systems are completely separate. Brain scans have located the vision-for-perception system deep in the cerebral cortex near the memory and language areas. This system is more interested in the identity of an object than in its orientation in space. In contrast, the vision-for-action system, located toward the top of the cerebral cortex near the motor and touch areas, is more interested in the object’s orientation than its identity.

Patients with damage to the perception system can’t recognize an object by looking at it but can accurately reach out and grasp it. Conversely, patients with damage to the action system have a hard time finding an object even though they still know what it looks like.

The Plastic Brain

Twenty years ago, we thought that once neural networks were wired, they were permanent. But as it turns out, our brains are capable of plasticity—that is, they are flexible and adaptive, which can come in handy in the event of disease, injury, or disorder.

DEFINITION

Brain plasticity, also known as neuroplasticity, refers to the brain’s ability to rewire itself, rerouting information or processing functions to different brain areas and/or neural networks to compensate for damaged brain pathways and lost functions.

A brain trauma patient who has spent 19 years in a minimally conscious state of coma suddenly wakes up … a stroke victim regains the use of her left arm …. How are these events possible? The patients’ plastic brains built new neural pathways and evolved new anatomical brain structures.

Our brains don’t have to be damaged for plasticity to occur, though. Plasticity also occurs with learning. You’ve heard the old expression “practice makes perfect”? Studies of musicians and athletes have shown that repetition (rehearsal) solders in and optimizes neuronal connections in specialized areas of the brain responsible for “fine” movements of the hands.

Our brains are also more flexible when we’re younger and become more specialized as we mature. This helps explain why children who injure a large part of one brain area tend to recover well, often completely.

PSYCHOBABBLE

Unfortunately, our brain’s flexibility only goes so far. The largest known ingestion of ecstasy pills—40,000 over a nine-year period—was recently reported. Known as Mr. A, this gentleman hasn’t taken X for seven years but still suffers from memory problems, paranoia, hallucinations, and depression.

Working with Half a Brain

Once psychologists realized that the different brain hemispheres did different jobs, they started wondering what one would do without the other. What would happen if the two halves couldn’t communicate back and forth? Would they fight with each other? Would they get along?

In the 1960s, researchers Roger Sperry and Michael Gazzaniga found some amazing answers to these questions. They studied patients whose corpus callosum (which connects the left and right hemispheres of the brain) had been cut in order to reduce the severity and frequency of their epileptic seizures. On the surface, these patients seemed fine; they walked normally, had no drop in their I.Q., and could carry on a good conversation. But when information was presented to just one visual field, they behaved as if they had two separate minds.

PSYCHOBABBLE

Could you really live with just half a brain? More than 50 epileptic children are successfully doing so. These children had severe, uncontrollable seizures confined to only one hemisphere; as a last-ditch measure, a hemispherectomy—the removal of one half of the brain—was performed. All are expected to lead normal lives.

In their experiments, Sperry and Gazzaniga flashed pictures of common objects on a screen and asked a participant to identify them. When the objects were flashed to the right, the person would look at the researchers as if they were complete idiots and say, “It’s an apple.” However, when the picture was flashed to the left, the participant would either deny that an object had appeared or would make a random guess.

When participants were next asked to reach under a barrier and touch the object that had just been flashed, they could reliably identify the object with the left hand but not the right! The right hemisphere could remember the feel and shape of the apple but couldn’t produce the word for it. If you never forget a face but never remember a name, you can relate!

What was going on? Remember that the right hemisphere controls sensation and movement from the left half of the body and vice versa. Remember, also, that input from the right visual field goes first to the left hemisphere and vice versa. Recall that, in most people, the left hemisphere controls language, and the right dominates spatial perception (faces, pictures, geometry). Because the connection that let the hemispheres communicate had been cut, the information simply couldn’t get where it had to go to be processed!

However, the brain can call upon some super-powered equipment that virtually guarantees good communication. Let’s look at the fastest communication system in the world—your nervous system.

You’ve Got Nerve

The Internet has nothing on your nervous system—it’s a huge network of more than 100 billion nerve cells that rapidly relays messages to and from the brain. These nerve cells, called neurons, are specialized cells that receive, process, or relay information to other cells within the body. The fastest of these messengers can send electrical impulses at a rate of up to 250 miles per hour.

DEFINITION

A nerve is a bundle of sensory or motor neurons. When someone is getting on your nerves, you have 43 pairs for the person to get on—12 pairs from the brain and 31 pairs from the spinal cord. A neuron is a nerve that specializes in information processing.

The nervous system has two substations: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of all the neurons in the brain and the spinal cord, whereas the PNS is made up of all the neurons forming the nerve fibers that connect the CNS to the rest of the body.

If the body were an army, the brain would be the general, synthesizing and coordinating all bodily functions, interpreting all the messages coming in from the body, and sending strategic commands appropriate to the environmental situation. The spinal cord, a trunk line of neurons that connects the brain to the PNS, would be the lieutenant.

All the messages directed to the CNS are sent and received through the spinal cord. Damage to the spinal cord disrupts the brain’s ability to send and receive messages and, if the spinal cord is severed, the brain can no longer receive important messages from its limbs. So for instance, you wouldn’t feel pain even if a toe was roasting in the fireplace. Without the lieutenant, the general can’t send commands for the body to protect itself. Your regular soldiers—your sense organs—would be completely disabled.

PSYCHOBABBLE

It’s hard to believe that wisdom comes with age when you realize you lose almost 200,000 neurons each day. Fortunately, you start out with so many that even after 70 years you’ve still got more than 98 percent of your original supply. Besides, it’s the connections between the neurons that count. Albert Einstein had no more brain cells than you or I, but he allegedly had incredibly dense connections between the various parts of his brain.

Speedy Delivery

Neurons are the basic unit of the nervous system. We have three types: sensory neurons, motor neurons, and interneurons. Sensory neurons carry information in from the senses toward the central nervous system. When someone steps on your toes, the sensory neurons get excited and send the scoop to the brain.

Motor neurons carry messages from the central nervous system back to the muscles and glands. Since sensory neurons rarely communicate directly with motor neurons, the interneurons act as brokers, relaying messages back and forth between the two and, occasionally, communicating with other interneurons.

PSYCHOBABBLE

A new class of brain cells has recently been discovered. Tagged “mirror neurons,” they fire both when we perform an action and when we watch one being performed. Some scientists speculate that a mirror system forms our basis for social behavior, for our ability to imitate, acquire language, and show empathy and understanding.

Doing the Neuron Dance

All neurons have a soma, dendrites, and an axon. The soma contains the nucleus of the cell and the cytoplasm that supports it. At one end of the soma are the dendrites, a bunch of branched fibers that receive messages from other neurons. The soma integrates the information from the dendrites and passes it on to a single, extended fiber called an axon.

The axon’s job is to carry electrical impulses, called “action potentials,” from the neuronal cell body to other cells. A neuron’s message lies in the number of action potentials that move down the axon, which are determined by the speed with which electrical impulses are produced. The axon conducts these electrical impulses along its length until they literally reach the end of their rope—swollen, bulblike structures called terminal buttons that lie at the end of the axons. Action potentials trigger the release of chemical substances called “neurotransmitters” from each terminal button.

When a neuron is stimulated by another neuron’s impulses or by sensory stimulation, it fires off its own electrical impulse. The neural impulse travels the length of the neuron along the axon, finally arriving at the terminal buttons.

Synaptically Speaking

Here’s where it gets a little tricky, because there is no direct physical contact between a terminal button and the impulse’s next destination. Instead, there’s a gap at the near junction of two nerve cells—we call this gap a synapse. The traditional view of neurotransmission has been that, when an impulse leaps the gap from a terminal button to the next stage in its journey, a small packet holding neurotransmitters (a synaptic vesicle) moves to the inner membrane of the terminal buttons.

The vesicle ruptures, spilling its neurotransmitters into the synaptic gap, and neurotransmitters attach themselves to the dendrites of neurons on the other side of the gap. If the neurotransmitter inputs are sufficiently stimulating, the receiving neuron will either fire or be prevented from firing, relaying the impulse message from cell to cell.

However, we now know that neuronal firing does not occur exclusively at the synapse. Rather, neurons may release neurotransmitters along the entire length of the axon, exciting neighboring cells. Whew! It’s even more complicated than we thought!

White Matter Matters!

Surrounding the neurons is white matter, which contains axons and ancillary cells—cable ducts—that link the left and right hemispheres of the brain. Even though white matter contains no dendrites or synapses, neurotransmission still takes place. When an electrical impulse travels through an axon cable, tiny bubbles containing the neurotransmitter glutamate travel to the axon membrane and release their content into the brain.

Researchers believe that glutamate guides cells in the white matter known as oligodendrocytes, “insulating cells,” to produce myelin, a fatty layer that surrounds the axons and ensures rapid retransmission of signals. Axons travel through the cable ducts in the white matter to the brain’s grey matter, where the message is relayed at the synapse to receptor dendrites, but also to other areas in the gray matter which do not contain synapses. The axon not only excites receptor dendrites but also other surrounding nerve cells as well.

BRAIN BUSTER

Too much glutamate can be hazardous to these insulating cells. During an epileptic seizure, for example, nerve cells fire rapidly and fiercely, sending a torrent of impulses through axons and releasing too-high doses of glutamate that can damage the oligodendrocytes.

With all this firing going on, it’s no surprise that there are often tiny leftover “sputtering” releases of neurotransmitters, even up to a few minutes after the main firing event. And, if left unchecked, these leftovers can lead to neurological chaos.

Enter complexins, small proteins that typically prevent neurotransmitters from releasing prematurely. However, if there’s a breakdown in this mechanism, spontaneous mini-firings can occur, rewiring neural pathways and spurring massive amounts of synaptic new growth. MIT researchers believe this chaos may be the culprit behind neurological disorders such as schizophrenia. Controlling this area may one day allow us to rewire brain areas involved in neurological disease.

Blame It on Your Hormones

Remember all the weirdness you went through in your teens? Hair sprouting in different places and body parts growing at different speeds? How about those mood swings? This was all caused by your hormones.

The endocrine system, controlled by the hypothalamus in the midsection of the brain, produces and secretes hormones into the bloodstream. These chemicals are involved in many different bodily functions, from your sexual development to your arousal, mood, and metabolism. Your endocrine communication system helps you regulate everyday alertness and mood. It also helps you respond to emergencies. The most famous hormone is adrenaline, an energizer that responds to emergencies by preparing you for “fight or flight.”

PSYCHOBABBLE

A new study reveals that cognitive decline in normal aging may be caused by a breakdown of neural crosstalk. Age slowly degrades white-matter nerve axons that act as communication conduits between different brain regions—for example, between the network that processes information from the outside world and our internal “default network,” which kicks in when we muse to ourselves.

Adrenaline Alert

When something frightens you, your heart pounds, your muscles tense, and you break out in a cold sweat. That’s your endocrine system preparing you to respond to a life-threatening situation. In fact, long after the danger passes, you may still feel your endocrine system doing its job.

Brain Booboos

Imagine that your spouse is diagnosed with a brain tumor. After the initial shock, you and he discover that the tumor is benign and, although large, quite operable. During surgery, the tumor is removed, recovery goes well, and your spouse is pronounced completely cured.

Except that he’s not. Ever since his surgery, you feel like you’ve been living with a different person. Your sweet, patient, adoring spouse now seems moody, impatient, and short-tempered. Although your well-meaning friends and family are telling you both how lucky you are, inside you feel increasingly confused, frustrated, guilty, and scared. And you’re no longer sure you want to stay married to the stranger your spouse has become.

Given the link between our minds and our brains, it’s not surprising that physical injuries to our brains can do a number on our psyches. The severity and type of personality change usually depends on the part of the brain that’s been injured. For example, because the frontal lobes often serve as “the brakes” in controlling our emotions, impulses, and instincts, a person with frontal lobe damage may have difficulty inhibiting inappropriate behavior. This person may be particularly prone to saying and doing things that may appear insensitive or irritable.

INSIGHT

Boost your brain—and help ward off Alzheimer’s—with exercise! Researchers have found that regular exercise controls the expression of genes in an area of the brain important for memory and maintaining healthy cells in the brain; this maintenance breaks down with Alzheimer’s disease.

You can see that much of what goes on in our brain is outside our conscious awareness. You can also see that we’re discovering new things about—and developing more respect for—our brains every day; take a look at just some of the cutting-edge research that’s emerged.

The mind may be more of an interpreter than a leader; although it gives us rational explanations for our behavior, it may not always be in the driver’s seat. In the next chapter, we explore two areas that influence how well we drive: nature and nurture.

The Least You Need to Know