001

Table of Contents
 
Title Page
Copyright Page
Dedication
Acknowledgements
Preface
Introduction
You Gotta Know the Territory: A Short Tour of Your Brain
Your Neurotransmitters
Charting the Day: Your Body Clocks
The Best of Times?
 
Part 1 - COMING TO CONSCIOUSNESS AWAKE AND AWARE 5 A.M. TO 8 A.M.
 
5a.m. - Waking to the World
 
Your Inner Alarm Clocks
Your Brain Chemicals
Larks and Owls
Coming to Our Senses
An Orchestra of Sensory Harmony
Touch and Movement: Feeling Our Way
Varieties of Touch
 
6 a.m. - Coming to Consciousness
 
The Seat of Consciousness
Emotion, Memory, and Consciousness
It’s Always About Networking
Little Gray Cells and Big White Matter: Myelin in Your Brain
Prime Time for Heart Attack and Stroke
 
7 a.m. - Those Morning Emotions
 
Reason Needs a Neurochemical Boost
Can Meditation Help Master Those Emotions?
Is There a God Spot in Your Brain?
Practice Makes Compassion
 
8 a. m. - Finding Your Way
 
Why His Brain May Not Ask Directions
How We Know Where to Find Our Lost Keys
 
Part 2 - ENGAGING THE WORLD GETTING OUT AND ABOUT 9 A.M. TO NOON
9 a.m. - Encountering Others
 
That Face, That Familiar Face
Friend or Foe? Read My Face
Mirror, Mirror: Copycat Neurons in the Brain
The Broken Mirror: Autism Insights from Mirror Neurons and Face Perception
 
10 a.m. - Peak Performance—or Stress?
 
Stress in the Brain
The Alarm That Doesn’t Stop: Why Chronic Stress Is So Bad
Stress Destroys Neurons
Stress Ups the Risk of Alzheimer’s Disease
The Very Thought of It Is Enough
Multitasking—Again?
The Limits of Multitasking
How Your Brain Helps Your Job Kill You
You Can Lull Your Brain Away from Stress
Flow Versus Stress
 
11 a.m. - Decisions, Decisions, and More Decisions
 
The Brain’s CEO
“Chemo Brain” Can Ambush Your CEO
Choosing Economically
Making an Emotional Moral Choice
Choosing Wearies Your Brain
The Brain Has a Section for Regret
 
12 noon - The Hungry Brain
 
How Hunger Works in Your Brain
We’re Losing Our Scents
Still Hungry? When Hunger Goes Awry
Why Calories Taste Delicious
Addicted to _______________ (Fill in the Blank)
Self-Control Sucks Your Energy
Yes, There Is Such a Thing as Brain Food
 
Part 3 - THE GUTS OF THE DAY GETTING DOWN TO BUSINESS 1 P.M. TO 4 P.M.
1 p.m. - The Tired Brain
 
Partial Recall: Why Memory Fades with Age
Can You Help Your Brain Stay Young(er)?
Predicting Alzheimer’s Disease
How Forgetting Is Good for the Brain
Asleep at the Wheel-Almost? It Could Be Narcolepsy
1:54 P.M. Just Time for a Six-Minute Power Nap
 
2 p.m. - Bored Bored Bored
 
Can’t Get No Satisfaction? Maybe It’s ADHD
ADHD and Risk Taking Could Be Good—Sometimes
Wired and Hooked: Addicted to Technology
 
3 p.m. - Your Pain Is Mainly in the Brain
 
How Pain Hurts Your Brain
Mind Under Matter, Mind over Brain
Is Hypnosis Real?
A Window into Traumatic Forgetting
 
4 p.m. - Exercise Your Brain
 
Exercise Grows Neurons and Improves Memory
Why We Get Food Cravings
The Most Dangerous Time for Teens
The Teen Brain Is Still Changing
But Don’t Forget Hormones
 
Part 4 - TIME OUT LETTING GO AND COMING HOME 5 P.M. TO 8 P.M.
5 p.m. - The Dimming of the Day
 
Is It Really Depression? Or Just a Bad Patch?
Searching for the Pathway to Depression
Maybe You’re Just SAD
Magnetic Energy May Work When Meds Fail
A Peak Time for Suicide
Good Grief: Addicted to Grieving
 
6p.m. - Coming Home
 
An Oxytocin High
Nobody Home? Loneliness Hurts
Oh, Those Comforting Cravings. Or Is It Addiction?
Bottoms Up: Where Many Alcoholics End
Is Addiction the Result Rather Than the Cause of Brain Damage?
Still Crazy After All These Years? Aging Isn’t Stopping Drug Use
 
7 p.m. - Gotta Sing, Gotta Dance
 
The Musical Path to the Brain
Music Survives Brain Damage
Your Brain Expands to Store Music
So You Think You Can Dance?
Born to Rock?
The Creative Brain
Right Brain, Left Brain?
Don’t Oversimplify That Right Brain Stuff
The Musical Ear Is Learned, Not Born
 
8 p.m. - Humor Is Healthy
 
The Best Medicine
Tracking Your Internal Laugh Track
TV Addiction Is No Mere Metaphor
 
Part 5 - WINDING DOWN FEAR, SEX, SLEEP, AND DREAMS 9 P.M. TO MIDNIGHT
9 p.m. - Things That Go Bump in the Night
 
How Fear Works in Your Brain
Who’s Afraid? Not These Brain Cells
When the Brain Decides It’s Time to Scram
The Many Parts of a Violent Brain
 
10 p.m. - Lust, Sex, and Love
 
Your Brain on Sex
Women, Men, and Orgasms: How Alike Are They?
Does the Penis Have a Brain of Its Own?
What’s Love Got to Do with It? Plenty, It Turns Out—for Women
Are You Born Gay? Sexual Orientation Is Biology, Not Choice
 
11 p.m. - Falling Asleep
 
The Five Stages of Sleep
Insomnia: Curse of the Night
Perhaps Less Is More?
Interrupted Sleep? Don’t Call It Insomnia. It’s Normal
Call Me Sleepless
Still Awake? Can You Catch Up on Lost Sleep?
Is Insomnia Worse for Night Owls?
 
12 midnight - Sleeping in the Midnight Hour
 
Strolling in Your Sleep
Drifting into Dreamland
Do Banished Thoughts Resurface in Dreams?
Want to Dream More? Try Sleep Deprivation
 
Part 6 - NIGHT CREW AT WORK 1 A.M. TO 4 A.M.
1 a.m. - Night Crew at Work
 
Cleaning Up Your Neural Garbage
Why Your Brain Doesn’t Take a Break Already
The 10 Percent Myth
 
2 a.m. - Going Against the Clock in Your Brain
 
Disasters on the Night Shift
Lack of Sleep Affects Doctors as Much as Alcohol
Less Sleep? More Fat
Biorhythm and Blues: Faulty Clocks
Resetting Your Body Clock
 
3 a. m. - Awake and Anxious
 
Where the Nightmare Begins
A False Alarm
That Pill to Fix Your Ills Has a Price
3:30 A.M. Night Nurse on Duty
 
4 a.m. - Last Sleep
 
4:30 A.M. Awake So Early? You May Be an Unlucky Lark
 
Your Brain Tomorrow
Sources
Illustration Credits
Glossary
About the Author
Index

001

For my beautiful and brainy grandchildren: Isabela, Ragsdale Blue, Raj, and Raina Leela (Lulu)

Acknowledgments
This book would not have been possible without the research and the articles of the many excellent contributors of Scientific American and Scientific American Mind: their work is in large part the basis of this book and is acknowledged in detail in the Sources. Thanks to the staff at Scientific American—Diane McGarvey, director of ancillary products, and Linda Hertz, manager of permissions and rights—for help with the many editorial details involved in processing hundreds of articles from the archives. The Jossey-Bass team provided invaluable support: thanks to publisher Paul Foster, who originated the concept for this book, marketing manager Jennifer Wenzel, production manager Carol Hartland, copywriter Karen Warner, and copyeditor Beverly Miller. Special thanks to executive editor Alan Rinzler and senior editorial assistant Nana Twumasi. I am grateful to several scientists who gave this text a careful read and some thoughtful commentary, especially Merrill M. Mitler, program director at the National Institute of Neurological Disorders and Stroke, Kelly A. Dakin, a doctoral candidate in the Program in Neuroscience at Harvard University/Harvard Medical School, and Jason Coleman, a Howard Hughes Medical Institute postdoctoral fellow at the Picower Institute for Learning and Memory at MIT. Many thanks also to literary agent Andrea Hurst, author and editor Jennifer Basye Sander of Write By the Lake, and my many fellow writers, including Ann Crew, Joan Aragone, and the Writers Who Wine (you know who you are) for their support and encouragement.

Preface
What’s your brain doing right now? What was it doing when you woke up, got hungry, went to work, danced, made love, got angry, got happy, dreamed, and fell asleep? How in the world does your brain recognize people and places, and how does it make decisions and memories? What is happening in your brain as you go through a typical day and night?
These questions (and more) were the spark for this book: an hour-by-hour journal of a day in the life of your brain and how it affects you as you go about your day. The editors at Jossey-Bass conceived the idea and took it to Scientific American magazine, a treasure trove of fine articles about these very issues.
I was brought to the project to weave it together from the Scientific American articles, editing, restructuring, and adding materials to give a daily progression that most of us can recognize in our own lives.
It was a pleasure to delve into the excellent articles in the Scientific American archives, and hard not to get lost in all of the fascinating material. I found many surprises, recognized many processes in my own brain, and was left with even more respect than ever for this three pounds of “thinking meat.”
The book is structured by the clock, beginning at 5:00 A.M. as we (or some of us) awake, and ending at 4:00 A.M., in the last moments of sleep. You might find yourself comparing the activities of your own brain as you read.
As scientists continue to study the brain, we’ll know even more about how our brain works and influences us moment to moment. We’ll also know more about how to control it. Meanwhile, this book represents the fascinating and entertaining state-of-the-art brain science that we can use in our daily lives.
 
JUDITH HORSTMAN

Introduction
Your brain is the most important organ in your body. Without it, nothing else would work—and you wouldn’t be aware of it if it did.
It’s the repository of memory, mind, and feeling; the conductor of the orchestra that’s your body; the seat of consciousness that is you.
Every day this three pounds of “thinking meat” navigates you through the ordinary and extraordinary events of being human—from waking to sleep, and everything in between. It guides your body through motions of intricacy and delicacy, ranging from the most gross to the most subtle of movements, emotions, and thoughts; from unconsciousness to wide awake and even hyperawareness. It allows you to see the stars through a telescope and a molecule in a microscope—and using instruments the brain has created.
Until recently, most of what we know about how the brain works came from examining damaged brains, where scientists learned what was lost, or by studying animal brains (it is, after all, unethical and illegal to cut up living humans).
Today specialized imaging techniques and instruments have given us new windows into the living brain, thanks to volunteers, from meditating monks to copulating couples, who agree to have their brains imaged in action. Using instruments such as functional magnetic resonance imaging (fMRI) to view the brain as thoughts, feelings, and actions occur, researchers are able to see which parts are activated when we have sex, eat, express anger, listen to music, dance, sleep, or meditate.
There have been many surprises.
Your brain, for example, is more like a Rube Goldberg contraption than the computer to which it is so often compared. It’s jam-packed with functions, programs, connections, and interconnections that often overlap with each other. That’s probably because its many complex and diverse parts evolved over time, piggybacked in ways that intertwine and are still not completely understood.
And it’s even less like the old phrenology models of a human head, with their neatly color-coded brain compartments. In fact, your brain is not even like the basic texts on brain science of a few decades ago.
Processes thought to be hardwired are turning out to be adaptable. The brain is not as set in stone as previously thought. We are finding that the same neurotransmitters and brain regions that foster love, cooperation, and trust also foster lust, addiction, and fear. Sex, drugs, and rock and roll have the same address. Memory is handled by several different parts of the brain and seems to do much of its short-term work while we sleep. Music plays in many parts of the brain. And when push comes to shove, your most primitive emotional brain part, the amygdala, rules. There are many more connections from the amygdala to the thinking brain than the other way around.
Most exciting is the finding that your brain is teaching old neurons new tricks and even making new neurons. When some sections of the brain go dark, other parts of the brain can learn to take over part of those functions. In fact, many who have half their brain removed for medical reasons function pretty well with just one hemisphere. See “Do You Need Only Half a Brain?” page 7.
A caveat: although we title this book A Day in the Life of Your Brain, it cannot be so. Your brain is unique and uniquely yours, affected by your age, genes, race, ethnic and cultural origins, family culture, diet, and even birth order: all the things that make you you. However, there are universal processes, and the equipment is basically the same in most of us, except for the extremes of aging and disease and trauma.
DID YOU KNOW . . . ?
• Your brain has an estimated 100 billion neuron cells and 40 quadrillion connections. But nobody knows for sure.
• You used to have even more cells and connections. By the time you were born, you lost half the neurons you had as a fetus. In your teens, you lose even more as your brain streamlines itself for optimal function.
• Your brain is big. With its many creases, folds, and layers, it would take up more than three times its area if it were spread out flat.
• Your brain is an energy hog. Although your brain occupies only 2 percent of your body, it sucks 20 percent of your body energy when you are at rest.
• Your brain can make new neurons. Scientists are discovering the brain makes new connections and creates neurons in some areas to meet new needs, and it does so into old age.
• The brain can change. It can adapt from exterior and interior experiences to take on new functions. The more you repeat something—an action or a thought—the more brain space is dedicated to it. In musicians, for example, the part of the brain that controls fingers used to play an instrument is up to 130 percent larger than that section in the rest of us. While the very young brain is most adaptive, old brains can be retrained as well.
• Your brain prunes itself. Much as a gardener prunes roses, the brain weakens less-used connections and strengthens useful connections, which actually improves memory.
• Stress can shrink your brain—and meditation and exercise strengthen your brain and your ability to relieve stress.
• Your brain’s surface itself has no sensation. You could touch it (and surgeons do) and feel nothing. Only when the interior parts are stimulated do you feel, both tactilely and emotionally. This anomaly allows patients to be conscious when doctors perform delicate brain surgeries.
You’re probably neither a computer tech nor a brain scientist. What we suspect you want to know is: What’s happening in there as you go about your day? Which part does what, how, when, and—if we know—why? The hour-by-hour sections of this book explain what’s going on during some of our most ordinary and extraordinary everyday events.

You Gotta Know the Territory: A Short Tour of Your Brain

Your brain is about three pounds of flesh, nerves, and fluid that looks like an oversized walnut but is much softer. Nestled in the protective shell of your bony skull, it has the squiggly consistency of gelatin.
The overall brain is often described in three parts, from the bottom up, just the way your brain evolved over millennia.
The primitive brain—the brain stem or hindbrain—that sits at the top of the spine is the oldest part of your brain. It takes care of basic business such as breathing, heartbeat, digestion, reflexive actions, sleeping, and arousal. It includes the spinal cord, which sends messages from the brain to the rest of the body, and the cerebellum, which coordinates balance and rote motions, like riding a bike or catching a ball.
Above this, the brain is divided into two hemispheres connected by a thick band of fibers and nerves called the corpus callosum. Most brain parts from here on up come in pairs, one in each hemisphere. And although these two halves are very similar, they are not twins. Each side functions slightly differently from the other. In an oft-cited overgeneralization, the right hemisphere is associated with creativity and the left hemisphere with logic. For reasons unknown, the messages between the hemispheres and the rest of our body criss-cross, so that the right brain controls our left side, and vice versa.
Your emotional brain—the inner brain or limbic system—is tucked deep inside the bulk of the midbrain and acts as the gatekeeper between the spinal cord and the thinking brain in the cerebrum above. It regulates sex hormones, sleep cycles, hunger, emotions, and addictions.
The amygdala handles survival needs and emotions such as fear and anger. It’s responsible for the fight-or-flight reaction. The tiny The thalamus passes along sensory information to and from the cerebrum, the limbic system, and the spinal cord. The basal ganglia surrounds the thalamus and is responsible for voluntary movement. The so-called pleasure center or reward circuit is also based in the limbic system, involving the nucleus accumbens and ventral tegmental area.
WHY DOES YOUR BRAIN USE SO MUCH POWER?
Your brain is an energy hog. It takes up 2 percent of your real estate, but uses 20 percent of the body’s total energy haul when you are at rest—more energy than any other human organ. That’s probably because your brain never seems to rest.
Scientists believe it uses the bulk of that energy—two-thirds of it—to fuel the electrical impulses neurons use to “fire” or send signals to communicate with one another. A study in the Proceedings of the National Academy of Sciences suggests that your brain uses the remaining third for “housekeeping,” or cell health maintenance.
Housekeeping is important for keeping brain tissue alive and well, and for the many biological and chemical exchanges processed in the brain. Charged sodium, calcium, and potassium atoms (or ions) are continuously passed through the membranes of cells so that neurons can recharge to fire. Adenosine triphosphate (ATP) supplies the energy required for these ions to traverse cell membranes. When researchers measured the brain level of ATP in rats, they found the more alert animals used more of this substance. When the lab rats were knocked out, they produced 50 percent fewer ATP molecules than when they were mildly anesthetized. That ATP seems to go mostly toward cell maintenance, scientists believe.
hippocampus is the gatekeeper for short-term memories, and the hypothalamus controls your biological clock and hormone balance.
At the very top of the brain is the wrinkly and crevassed cerebrum—the part we usually see when we picture a brain and what is sometimes called “the crown jewel” of the body. The actual crown is the nickel-thin layer of the cerebral cortex (or neocortex) that covers the cerebrum. This is the most recently evolved part of the brain—the part, some say, that makes us human. It controls thoughts, reasoning, language, planning, and imagination.
The cerebrum has four major sections or lobes. Research has found that the frontal lobes take care of speech, movement commands, and reasoning. The occipital lobes in the back take care of vision, while the temporal lobes (above your ears) are responsible for hearing and for understanding speech and appreciating music. The parietal lobes run across the top and sides of the brain and are the primary sensory areas, receiving information about taste, temperature, touch, and movement. They are also involved in reading and math.
But your brain is more than geography. It’s chemistry and electricity as well.
All of these parts are made up of nerve cells called neurons that carry information throughout your body. Some neurons are three feet long, and most of them live as long as you do (in contrast to other cells that die and are renewed). These neurons are separated by microscopically tiny gaps called synapses. Each neuron can communicate with hundreds of thousands of other neurons by releasing neurotransmitters—chemicals to carry messages over the synaptic gap—or by a minute electrical impulse. Billions of tiny blood vessels (capillaries) feed your brain, carrying oxygen, glucose, nutrients, and hormones to brain cells so they can do their work.

Your Neurotransmitters

There are more than a hundred different neurotransmitters, with more being discovered. Scientists are finding that many hormones can play the role of neurotransmitter as well. Here are some of the neurotransmitters your brain uses every day:
• Acetylcholine gets us going: it excites cells, activates muscles, and is involved in wakefulness, attentiveness, anger, aggression, and sexuality. Alzheimer’s disease is associated with a shortage of acetylcholine.
• Glutamate is a major excitatory neurotransmitter, dispersed widely throughout the brain. It’s involved in learning and memory.
• GABA (gamma-aminobutyric acid) slows everything down and helps keep your system in balance. It helps regulates anxiety.
• Endorphins act as hormones and neurotransmitters: they reduce pain sensations and increase pleasure. The name, by the way, is a combination of end(ogenous) (m)orphine.
• Epinephrine, also called adrenaline, keeps you alert and your blood pressure balanced, and it jumps in when you need energy. It’s produced and released by the adrenal glands in times of stress. Too much can increase anxiety or tension. Norepinephrine (noradrenaline) is a precursor and has similar actions.
• Dopamine is vital for voluntary movement, attentiveness, motivation, and pleasure. It’s a key player in addiction.
• Serotonin helps regulate body temperature, memory, emotion, sleep, appetite, and mood. Many antidepressants work by regulating serotonin.
• Oxytocin is both a hormone and a neurotransmitter. It’s responsible for labor, breast milk, mother love, and romantic love and trust.
DO YOU NEED ONLY HALF A BRAIN?
A surgery that removes half the brain is a drastic solution for disorders that can’t be controlled any other way. Brain surgeons have performed hemispherectomies on patients who undergo dozens of debilitating seizures daily that primarily afflict one hemisphere and resist all medication and treatments. Left untreated, these disorders can damage the rest of the brain.
Surprisingly, this surgery usually has no apparent effect on personality or memory. Does that mean a person needs only half a brain? Yes and no. People can survive and function pretty well after the procedure, but they will have some physical disabilities. The body parts that are affected depend on the person’s age at the time of the surgery. For adults, there can be significant loss of function on one side of the body and some vision impairment. If the left side of the brain is taken out, most people have problems with their speech.
The younger a person is when having the hemispherectomy, the less likely there is to be speech disability. Neurosurgeons have performed the functional operation on children as young as three months old. In these tiny patients, memory and personality develop normally.
A study of 111 children who underwent the procedure at Johns Hopkins between 1975 and 2001 found that 86 percent are either seizure free or have nondisabling seizures that don’t require medication. Another study found that children who underwent a hemispherectomy often improved academically once their seizures stopped. One became champion bowler of her class, one was chess champion of his state, and others are in college doing very nicely.
Researchers are probing how the remaining cerebral hemispheres acquire language, sensory, motor, and other functions, which could shed a great deal of light on the brain’s ability to adapt.

Charting the Day: Your Body Clocks

Just about everything you do is run by the clock—your own inner biological pacemaker known as the circadian clock, from the Latin circa (“about”) and diem (“a day”). This timekeeper is hardwired into many cells throughout your body and runs on a twenty-four- to twenty-five-hour cycle that follows the turning of the globe.
The powerful master clock that keeps your time lies deep in your brain. Called the suprachiasmatic nucleus (SCN), this tiny but mighty clock paces all sorts of daily physiological fluctuations and cycles, including body temperature, blood pressure, heart rate, hormone levels, and sleep-waking times. It tells your brain’s pineal gland when to release melatonin to promote sleep and when to shut it off to help you awaken.
Scientists have found that active clock genes are not just in the SCN, but are scattered throughout the body, so that some organs and tissues may be running on different schedules, with their mini-clocks responding to other external clues such as exercise, stress, and temperature changes.
Some of these clocks are accurate but inflexible, and others are less reliable but under your conscious control. They rule all of your functions and actions, and maybe even your life span, by determining the number of times your cells can divide.

The Best of Times?

Given all these ruling clocks, is there an absolute best time of day for differing activities? Perhaps. The field of chronobiology—the science of body time—is studying this now, with researchers in chronomedicine looking at the ways to match body cycles to medical care to maintain health and treat illnesses. Many body functions, diseases, and conditions peak and ebb at certain predictable times (see “A Time for Everything” on the following page). Every mom knows that childhood fevers rise at night, for example, and are lowest in the early morning, just as our temperatures when we are healthy follow that cycle. Doctors are finding that the timing of tests, treatments, or dosage may affect outcomes.
Your personal inner clock is unique, and understanding its rhythms may help you stay healthy longer. At the simplest level, people are either larks or owls: respectively, those who wake up and sleep early and those who perform best at late hours and prefer late rising. At its more sophisticated level, the time of day when patients receive chemotherapy, have surgery, or take daily medications or other treatments may have a great deal to do with their effectiveness. With the growing interest in patient-driven medicine and individualized medical care, circadian research is a fertile field.
A TIME FOR EVERYTHING: DAILY PATTERNS
Although each of us has a personal and slightly different body clock, surveys, observation, and research have found some overall patterns that follow the hours of the day. Your personal rhythm may not match the events listed here, of course, as the data are from many sources and represent an average.
002

Part 1
COMING TO CONSCIOUSNESS AWAKE AND AWARE 5 A.M. TO 8 A.M.

5a.m.
Waking to the World
One minute, you’re dead to the world. In dreamland. Incommunicado. The next second, or so it seems, you and your brain are being dragged into the waking world.
The wakeup call can be the relentless shrilling of an alarm clock, a baby’s cry, or the grind and beep of a garbage truck. Other senses—the smell and sound of brewing coffee, a shake or a splash of cold water, hunger, thirst, or an urge to urinate—can nudge you toward wakefulness. And with the first light, our body clocks chip in as well, setting off an ebb and flow of hormones and neurotransmitters to stimulate us to awareness.
The process of arousal actually takes several minutes and a literal brainstorm of neural activity with a complex combination of cues, neurochemicals, and body clocks to get you up and keep you awake.

Your Inner Alarm Clocks

A sentry system in your basic brain is set to arouse you when it detects change, such as that annoying alarm clock. Called the reticular activating system (RAS), it’s a part of your brain left over from the prehistoric era when you had to be able to detect danger immediately and wake abruptly.
The RAS acts as a gatekeeper for incoming stimulation and sensations, perking up when it detects something new and helping your brain wake up and stay alert and awake all day long. It connects your brainstem to your cortex, sensory organs, and limbic system to help process and regulate activity and consciousness in your thinking brain.
The RAS does this through fibers that project widely throughout your brain, many through the thalamus, considered to be the doorway between sensory input and the cerebral cortex. Reticular means “little net.” Like a net, the fibers of the RAS “catch” signals from the sensory systems about what’s happening in the body or its local environment.
A part of the RAS called the locus coeruleus is particularly attuned to respond to new, abrupt, or loud stimulation and is your brain’s major factory for norepinephrine, a neurotransmitter released in response to stress or other stimulation. As soon as the system detects a significant change, such as a snarling sabre-toothed tiger, a splash of cold water, or that ringing alarm clock, it pops out some strong chemicals to increase your state of alertness.
Meanwhile, as night turns to day, another alarm clock starts to “ring.” It’s the built-in light-dark alarm system of your body clock called the suprachiasmatic nucleus (SCN): two tiny bundles of ten thousand neurons, each no bigger than a letter on this page, nestled deep in your brain, very near the optic nerves.
As the morning light strikes your retina, photoreceptor cells there signal to the neurons in the SCN to begin firing. The SCN toggles a biological switch setting off a process that tells the pineal gland to shut off the flow of melatonin, start the waking process, and keep you awake all day.

Your Brain Chemicals

While you were sleeping, levels of adenosine, a neurochemical with a powerful effect on your sleep-wake cycle, were dwindling. Your entire metabolism slowed, bottoming out to its lowest rate about an hour ago, at 4:00 A.M. or so. Now, as you come to consciousness, a brew of chemical messengers from your brain is telling your metabolism to get up and go.
The neurotransmitter acetylcholine helps pass information to the rest of your brain’s sentry system for interpretation. As the amygdala detects a possible survival challenge (There’s an alarm!), your hippocampus helps decide how much focused attention and memory formation the stimulus warrants (it’s a wake-up alarm, not a fire alarm) and helps it get processed by your thinking brain where goal setting and decisions are made (if you ignore that alarm and are late again, you can lose your job, so you better get up now).
Other neurotransmitters jump in, including serotonin (necessary for mood regulation and involuntary movement) and dopamine (needed for voluntary movement and attentiveness). A hefty shot of cortisol jump-starts everything. Your body temperature, blood pressure, and respiration begin to rise. And these arousal systems don’t stop after they wake you. An active RAS is vital for ongoing awareness. In fact, if your brain’s RAS stops firing signals, you may fall asleep again, and damage to your RAS can cause coma. Many general anesthetics and some tranquilizers work on this part of your brain.
The SCN will also stay active most of the day, helping you stay awake until evening when the process reverses, and the rising levels of sleep-promoting chemicals such as melatonin and adenosine make you sleepy all over again.

Larks and Owls

The trip from sleep to consciousness seems longer for some people than others. Some of us seem to wake up instantly: as soon as our eyes pop open, we appear to be fully awake and often upright. Others struggle toward consciousness, moving and sometimes speaking but not fully connected for a half-hour or more, responding to a body clock set a bit later.
Some of us are morning people; some of us are not. Scientists don’t know why yet, but all of us know which is which. In case you don’t know which you are (or are not sure about someone else) here’s a list of characteristics that makes it clear that larks and owls march to different body clocks.
The numbers in brackets are points you scored for each answer. You’ll find out how to use them at the end of the questionnaire.
ARE YOU AN OWL OR A LARK?
1. Breakfast: How’s your appetite in the first half-hour after you wake up in the morning?
a. Very poor [1]
b. Fairly poor [2]
c. Fairly good [3]
d. Very good [4]
2. For the first half-hour after you wake up in the morning, how do you feel?
a. Very tired [1]
b. Fairly tired [2]
c. Fairly refreshed [3]
d. Very refreshed [4]
3. When you have no commitments the next day, at what time do you go to bed compared to your usual bedtime?
a. Seldom or never later [4]
b. Less than one hour later [3]
c. One to two hours later [2]
d. More than two hours later [1]
4. You are starting a new fitness regime. A friend suggests joining his fitness class between 7:00 A.M. and 8:00 A.M. How do you think you’d perform?
a. Would be in good form [4]
b. Would be in reasonable form [3]
c. Would find it difficult [2]
d. Would find it very difficult [1]
5. At what time in the evening do you feel tired and in need of sleep?
a. 8:00 P.M. to 9:00 P.M. [5]
b. 9:00 P.M. to 10:15 P.M. [4]
c. 1:15 A.M. to 1:45 A.M. [3]
d. 1:45 A.M. to 2:00 A.M. [2]
e. 2:00 A.M. to 3:00 A.M. [1]
6. If you went to bed at 11:00 P.M., how tired would you be?
a. Not at all tired [0]
b. A little tired [2]
c. Fairly tired [3]
d. Very tired [5]
7. One night you have to remain awake between 4:00 A.M. and 6:00 A.M. You have no commitments the next day. Which suits you best?
a. Not to go to bed until 6:00 A.M. [1]
b. Nap before 4:00 A.M. and sleep after 6:00 A.M. [2]
c. Sleep before 4:00 A.M. and nap after 6:00 A.M. [3]
d. Sleep before 4 A.M. and remain awake after 6:00 A.M. [4]
8. Suppose that you can choose your own work hours but have to work five hours in the day. When would you like to start your workday?
a. Midnight to 5:00 A.M. [1]
b. 3:00 A.M. to 8:00 A.M. [5]
c. 8:00 A.M. to 10:00 A.M. [4]
d. 10:00 A.M. to 2:00 P.M. [3]
e. 2:00 P.M. to 4:00 P.M. [2]
f. 4:00 P.M. to midnight [1]
9. At what time of day do you feel your best?
a. Midnight to 5:00 A.M. [1]
b. 5:00 A.M. to 9:00 A.M. [5]
c. 9:00 A.M. to 11:00 A.M. [4]
d. 11:00 A.M. to 1:00 P.M. [3]
e. 5:00 P.M. to 10:00 P.M. [2]
f. 10:00 P.M. to midnight [1]
10. Do you think of yourself as a morning or evening person?
a. Morning type [6]
b. More morning than evening [4]
c. More evening than morning [2]
d. Evening type [0]
Scoring: Add up the points you scored for each answer. The maximum score for these questions is 46. The minimum is 8. The higher your score, the more of a morning person you are. The lower the score, the more you’re a night owl.

Coming to Our Senses

As you swing out of bed and start your morning ritual, your senses wake up to guide you through the day. Taking your morning shower, brushing your teeth, tying your shoes: you probably don’t give any of this much thought, and you don’t need to. Your brain is directing these actions on a subconscious level. (See “Your Brain Prefers Autopilot,” page 24.)
WHY DO MEN AWAKE WITH ERECTIONS?
Waking up with an erection is fairly common for a healthy male. In fact, an erect penis may be the default state. (Women also have nighttime erections. But more about that later. See “10:00 P.M.”)
Nocturnal erections don’t (usually) have much to do with sexy dreams or the need to urinate. Men have three to five cycles of nocturnal penile tumescence through the night during phrases of rapid eye movement (REM) sleep. Women go through the same cycle, with an engorgement of the labia, vagina, and clitoris.
These erections don’t usually wake us up, and researchers still don’t know exactly why they happen. Some speculate this ebb and flow over the long hours of sleep is part of nature’s way of keeping a blood supply to the sex organs.
Others think an erect organ may be the default state. Most of the time, the sympathetic nervous system puts the brakes on many functions, including erections, and it’s known that the sympathetic neurons in the locus coeruleus that connect to the spinal cord are turned off during REM sleep. This may allow nocturnal erections to occur.
Researchers are interested in morning erections as a clue to solving erection problems. If a man who has erectile dysfunction is getting morning erections, the cause could be psychological rather than physical. There hasn’t been much interest among researchers in women’s nocturnal turn-ons.
But no matter how simple (or unconscious) the action, each involves a multiplicity of complex memory, sensory, and muscle functions that, not surprisingly, involve many regions of the brain and frequently overlap with incoming data from other senses.
Take the simple act of getting a cup of coffee. You smell the coffee: it triggers a memory that you like and want coffee. You look around and see the coffee pot, hear it perking and bubbling, and get up and walk across the room and pour a cup. In just the milliseconds that your frontal lobes decide to get that cup of coffee, a tidal wave of neural signals sweeps across a multitude of brain regions.

An Orchestra of Sensory Harmony

Each step in the act of getting your coffee draws on a different combination of senses and brain regions to receive and interpret these incoming data. Your brain has to coordinate vision and sound with balance, touch, smell, and spatial awareness. It has to decide which muscles to activate to move you across the room and how much pressure to use when you pick up the cup and coffee pot, when to tip the pot and when to stop pouring coffee, whether the brew tastes strong enough for you, if it needs sugar or milk, if it’s too hot or too cool.
Smell pulled you toward the brew. It’s our most intense and ancient sense, profoundly connected to memory, sex, and survival. Even bacteria “smell” poisons or nutrients, danger or safety. Smell helps us select our sex mates and remember the good and bad. Many animals rely on smell to know the sex, social rank, territories, and reproductive status of others and to identity their own mates or offspring.
Smell is profoundly linked with memory. Just think how suddenly a familiar scent can whisk you into the past, even many decades ago. Proust surely did: he wrote thirty-two hundred pages featuring the power of memory, spurred by the remembered taste and smell of a small French cake, the madeleine.
Research shows he was right: smell can help the brain encode memories. Volunteers in one study memorized the locations of several objects while smelling a rose scent; then some of them were exposed to the same scent while they slept. Those with perfumed sleep remembered the locations of the objects much better than their fragrance-free peers did, because the scent probably reactivated memories stored temporarily in the hippocampus.
And no wonder. While human sense of smell is relatively weak compared to that of other mammals, we nevertheless have 347 different types of sensory neurons in the olfactory layer for smell inside the nose. Each one detects a different type of odor, and all the varied aromas and stenches we know result from mixtures of responses of these 347 types of receptor cells. By comparison with sight, for example, every color we see results from signal combinations of only three types of sensory neurons in the retina (red-, green-, or blue-sensitive cones).
THE VERY SMELL OF COFFEE MAY HELP THE RAT RACE
As you inhale that coffee aroma, the very smell intensifies alertness, partly because our brain remembers it as the scent of waking.
There may be a scientific basis for that coffee high. It seems that the aroma of coffee alone could be helpful to the stressed-out brain—in rats, at least, according to a report in the Journal of Agricultural and Food Chemistry.
Scientists had laboratory rats, including some that were sleep deprived, inhale the aroma of roasted coffee beans. They found the smell activated seventeen different genes in their brains, and thirteen of them produced proteins known to protect nerve cells from the damaging effects of stress. The experiment hasn’t been tried on humans yet (the rat brains were dissected for the study), but it’s known that caffeine also offsets the effects of adenosine, a sleep-promoting hormone.
You can conduct your own nonscientific study without shelling out four dollars for that latte. Just walk by the counter instead, inhaling deeply. The smell alone might be enough to kick-start your day.
Vision shows you where to go as information streams in through your retina, moving through the optic nerve to the thalamus and then to the occipital cortex. There your brain has to make various adjustments to “see” the coffee pot. Since light was criss-crossed when it passed through the lens, it was received upside down. And since the optic nerves partially cross over at the optic chasm, each hemisphere of the brain receives slightly different input from both eyes. Your brain combines the data for a three-dimensional effect and then neatly turns the image right-side-up. Finally, the parietal and temporal lobes interpret what the brain is “seeing.”
Sound helps you orient yourself in time and space. It enters the eardrums and travels through several complex processing and filtering centers, including the thalamus, and ends up in the temporal gyrus of our thinking brain where it is interpreted and processed further. Speech, for example, gets shunted to the left hemisphere language centers.

Touch and Movement: Feeling Our Way