Frequently Asked Questions¶

These are the questions students ask most often about the brain and about this book. Each answer is short and points you to the chapter section or glossary entry where you can learn more. Numbers and claims were checked against sources such as the NIH, the CDC, and peer-reviewed research.

Not medical advice

This FAQ is for learning. It is not medical advice. If you have questions about your own health, talk to a doctor. If you or someone you know is in crisis, call or text 988 in the U.S.

Getting Started¶

What is this book about?¶

From Neuron to Bedside is a free, interactive neuroscience textbook. It starts with a single neuron, tours the whole brain, and ends with how doctors examine patients. Every chapter closes with a fictional patient case, so you see how the science connects to real medicine. See the Course Description for the full list of topics.

Who is this book for, and what do I need to know first?¶

It is written for high school students in grades 9 to 12, Brain Bee competitors, future doctors, and teachers. The only real prerequisite is one year of high school biology, plus basic algebra for reading graphs. The chemistry you need, like ions and charge, is reviewed in Chapter 1.

Yes. The book is free to read online and is shared under a Creative Commons CC BY-NC-SA 4.0 license. That means you may share and adapt it for non-commercial purposes, as long as you give credit and share your version under the same license. The License page explains the details, and How to Cite shows how to give credit.

How should I use this book?¶

Every chapter follows the same pattern: a hook, the core science, an interactive simulation, a bedside case, common misconceptions, Brain Bee practice, exercises, and key takeaways. Read Chapters 1 to 4 first, because later chapters build on them. Try each practice question before you open the answer, because struggling to recall something and then checking makes memories stronger. How to Use This Book suggests study paths for curious readers, Brain Bee competitors, future doctors, and teachers.

What is a MicroSim, and do I need to know how to code?¶

A MicroSim is a small interactive simulation that runs in your web browser. For example, you can fire an action potential, block a synapse with a drug, or build a night of sleep stage by stage. You do not need to know any programming. Just move the sliders and click the buttons. Chapter 2's Action Potential Simulator is a good one to start with.

Is this book medical advice?¶

No. This book is for education only. The patient cases are fictional composites, except for well-documented historical cases like Phineas Gage and Patient H.M. If you have a health question, talk to a doctor. In an emergency in the U.S., call 911. See the Disclaimers.

Is this book connected to the Brain Bee or the Society for Neuroscience?¶

No. This is an independent student project. It is not affiliated with or endorsed by the International Brain Bee, the Society for Neuroscience, or any university or school. The book covers the kinds of topics the Brain Bee tests, but you should always check your own competition's official rules and study materials. See the Disclaimers.

Who is Ply the Sea Slug?¶

Ply is the book's mascot, an Aplysia californica sea slug. Scientists like Eric Kandel used Aplysia to learn how synapses change during learning, and Kandel shared the 2000 Nobel Prize in Physiology or Medicine partly for that work. You can meet Ply's real-life relatives in Section 9.10.

How was this book made, and what if I find a mistake?¶

The book was created by Aaryav Sharma, a high school student, using Dan McCreary's open-source intelligent-textbook framework. Every statistic, date, and drug approval was checked against sources like the NIH, the CDC, and peer-reviewed research. Mistakes can still slip through. If you find one, please use the Contact page. You can read more on the About This Book page.

Brain Basics¶

How many neurons does the human brain have?¶

About 86 billion. That number comes from a 2009 study that dissolved whole brains and counted the cell nuclei (Azevedo et al., 2009). The same study found roughly as many non-neuron cells as neurons. The older "100 billion" figure was a rough estimate that was never carefully measured. See Section 1.1.

What do glial cells do? Aren't they just "glue"?¶

Glia do much more than hold neurons together. They make myelin, supply neurons with fuel, clean up chemical messengers at synapses, help form the blood-brain barrier, and act as the brain's immune defense. You may have heard that glia outnumber neurons ten to one, but a review of 150 years of cell counting found the ratio in the whole human brain is about one to one or a little less (von Bartheld et al., 2016). See Section 1.7.

What is the blood-brain barrier?¶

The blood-brain barrier is a tight seal formed by the walls of the brain's blood vessels, with help from glial cells. It lets in what the brain needs, like glucose and oxygen, and keeps out many germs and chemicals. It also blocks many medicines, which is why doctors treating Parkinson's disease give levodopa instead of dopamine itself. See Section 1.9 and Section 7.10.

What is myelin, and what happens when it is damaged?¶

Myelin is a fatty wrapping around many axons that works like insulation on a wire, letting signals jump quickly from gap to gap. In multiple sclerosis (MS), the immune system mistakenly attacks myelin in the brain and spinal cord, which slows or blocks signals (NINDS). There is no cure yet, but approved treatments can reduce attacks and slow the disease. See Section 1.6 and the Chapter 1 bedside case.

Signals and Chemistry¶

What is an action potential?¶

An action potential is the brief electrical "spike" a neuron uses to send a message down its axon. At rest, the inside of a neuron is slightly negative, like a charged battery. When the neuron is pushed past a trigger point called threshold, sodium channels open, sodium rushes in, and the voltage briefly flips positive before potassium channels reset it. The whole spike lasts only about 1 to 2 milliseconds. See Section 2.5 and the glossary entry for Action Potential.

How fast do nerve signals travel?¶

Much slower than electricity in a wire. In thick, myelinated axons, signals can travel on the order of 100 meters per second, while thin unmyelinated pain fibers carry signals at only about 1 meter per second. Pain itself travels on fibers of different speeds: thin myelinated fibers carry the sharp "ouch" of stubbing your toe faster than unmyelinated fibers carry the slower, aching pain, so you feel the sharp part first. See Section 2.9.

If every spike is the same size, how does the brain tell a light touch from a hard push?¶

Action potentials are all-or-none: once a neuron reaches threshold, the spike is always about the same size. So the nervous system codes strength in other ways. A stronger stimulus makes each neuron fire more often, and it also activates more neurons. Think of it as "louder means faster, not bigger." See Section 2.8.

How do neurons talk to each other across a synapse?¶

At most synapses, neurons do not touch. When a spike reaches the axon terminal, it releases chemical messengers called neurotransmitters into a tiny gap. They bind to receptors on the next cell, like keys fitting locks, and nudge that cell toward firing or away from it. The signal is then cleaned up, often by being pumped back in, which is called reuptake. See Section 3.3.

Is dopamine the brain's "pleasure chemical"?¶

Not exactly. Dopamine is more about wanting and motivation than about the pleasure itself. In classic rat experiments, animals with almost no dopamine still showed normal "liking" reactions to sweet tastes (Berridge and Robinson, 1998). Dopamine also helps control movement, which is why losing dopamine neurons causes Parkinson's disease. See Section 3.7 and Chapter 3's Common Misconceptions.

How does caffeine keep you awake?¶

Caffeine is an antagonist, a drug that blocks a receptor without activating it. While you are awake, a chemical called adenosine builds up and signals "you've been up a long time." Caffeine blocks adenosine receptors, so that tiredness signal can't get through (Nehlig et al., 1992). It hides tiredness for a while, but it does not replace sleep. See Section 3.8.

Why does my lip go numb at the dentist?¶

Dental numbing shots use a local anesthetic, a drug that temporarily blocks the sodium channels in nearby nerves. Without working sodium channels, the nerves cannot fire action potentials, so pain signals never reach your brain. As the drug washes away over a few hours, the channels work again and feeling returns. The nerve is not damaged. See Section 2.10.

Brain Anatomy¶

What are the lobes of the brain, and what does each one do?¶

Each hemisphere has four main lobes. The frontal lobe handles planning, decisions, and movement. The parietal lobe handles touch and knowing where things are in space. The temporal lobe handles hearing, language understanding, and memory, and the occipital lobe handles vision. Real abilities depend on networks linking many areas, so these are "main jobs," not the only jobs. See Section 4.4.

Why does the left side of the brain control the right side of the body?¶

Most of the motor fibers that run from the brain to the spinal cord cross to the other side at the bottom of the brainstem. Many sensory pathways cross too. So a stroke in the left hemisphere usually causes weakness on the right side of the body. Doctors use this crossing rule every day to figure out where damage is. See Section 7.5.

What does the cerebellum do?¶

The cerebellum, the "little brain" at the back of the head, coordinates movement, balance, and timing, and it helps you learn new motor skills. It makes up only a small part of the brain's mass, but it contains roughly four out of five of the brain's neurons. Damage to it causes clumsy, unsteady movements rather than paralysis. See Section 7.8 and the glossary entry for Cerebellum.

What happened to Phineas Gage, and why does he matter?¶

In 1848, railroad foreman Phineas Gage survived an iron rod passing through the front of his skull and frontal lobe. His doctor reported that his personality and judgment changed, which helped scientists link the frontal lobe to behavior and self-control. Later historians found that some popular stories about him were exaggerated, and he appears to have recovered a good deal in later years (Macmillan and Lena, 2010). See What Really Happened to Phineas Gage.

Senses and Movement¶

Do humans really have only five senses?¶

No. Besides sight, hearing, touch, taste, and smell, you sense balance through your inner ear, body position through receptors in your muscles and joints (proprioception), temperature, and pain. Each one has its own receptors and pathways into the brain. See Section 6.2 and Section 6.5.

Each eye has a spot where the optic nerve leaves the retina, and there are no rods or cones there to detect light. You don't notice the hole because your two eyes cover each other's blind spots, and your brain fills in the gap using the surrounding scene. This is one example of how seeing is built by the brain, not just recorded by the eye. See Section 5.3.

Is there a "tongue map" with separate zones for sweet, salty, sour, and bitter?¶

No. Every part of the tongue with taste buds can detect all of the basic tastes, including umami, the savory taste. The famous map came from a misreading of a small 1901 study that found only slight differences in sensitivity around the tongue. See Section 6.8.

Why does rubbing a bumped elbow make it hurt less?¶

Rubbing activates large touch fibers, and those signals can "close a gate" in the spinal cord that reduces how many pain signals travel up to the brain. This idea is called gate control theory, first proposed by Ronald Melzack and Patrick Wall in 1965. The brain can also turn pain signals up or down depending on attention, emotion, and expectations. See Section 6.11.

How can someone feel pain in an arm or leg that has been amputated?¶

This is called phantom limb pain, and it is real, not imaginary. The brain still has a map of the missing limb, and changes in the nerves, spinal cord, and that body map can produce sensations, including pain, that feel like they come from the missing part. Doctors usually combine several treatments. Some also try mirror therapy, which aims to retrain the brain's map, but the evidence for it is mixed. See Section 6.12 and the Chapter 6 bedside case.

How does a reflex happen without the brain?¶

In a reflex like the knee-jerk, a sensory neuron carries the signal into the spinal cord, which sends a command straight back out to the muscle. The brain is not part of that loop, so the response is very fast, and the brain finds out afterward. Doctors test reflexes because changes in them help show where the nervous system is damaged. See Section 7.4.

What is Parkinson's disease?¶

Parkinson's disease happens when dopamine-making neurons in a small brain area called the substantia nigra slowly die (NINDS). Without enough dopamine, the basal ganglia act like a car with the parking brake on, causing slowness, stiffness, balance problems, and often a tremor. Levodopa, which the brain turns into dopamine, and deep brain stimulation can ease symptoms, but there is no cure yet. See Section 7.10.

Development and the Teenage Brain¶

Is the brain finished developing at 25?¶

"25" is a rough shorthand, not a finish line. The National Institute of Mental Health says the brain finishes developing and maturing in the mid-to-late 20s, and that the prefrontal cortex, which helps with planning and self-control, is one of the last parts to mature (NIMH). Different brain measures level off at different ages, and people vary a lot. The teen brain isn't broken, though: it is in a normal remodeling phase, and NIMH notes that most teens go on to become healthy adults. See Section 8.9.

Why do teenagers take more risks, especially around friends?¶

During adolescence, the brain's reward system becomes extra sensitive, while the prefrontal "brakes" are still maturing. In a well-known experiment, people took more risks with friends present, but the effect was much stronger for teens and young adults than for adults (Gardner and Steinberg, 2005). This isn't all bad: the same drive helps teens explore, make friends, and learn new skills. See Section 8.10.

What is synaptic pruning, and is losing synapses a bad thing?¶

Young children make far more synapses than they will keep. During childhood and the teen years, the brain removes connections that are rarely used and strengthens the ones that are used often, a "use it or lose it" process called synaptic pruning. Like trimming a hedge, pruning makes circuits more efficient, so it is a normal and healthy part of growing up. See Section 8.5.

Why is nicotine from vaping especially risky for teens?¶

Nicotine is highly addictive, and because the teen brain is still developing, it may be more easily changed by nicotine. The CDC warns that nicotine can harm the parts of a teen's brain that control attention, learning, mood, and impulse control (CDC). See Section 15.9.

Is a small amount of alcohol during pregnancy safe?¶

The CDC says there is no known safe amount of alcohol during pregnancy, and no safe time to drink (CDC). Alcohol can disrupt how the baby's brain develops, causing fetal alcohol spectrum disorders (FASDs), which can affect learning and behavior for life. FASDs are preventable if a developing baby is not exposed to alcohol. See Section 8.12.

Learning, Memory, and Sleep¶

How does the brain make a memory?¶

Memories are stored as changes in the strength of connections between neurons. When two connected neurons are active together over and over, the synapse between them gets stronger, a process called long-term potentiation (LTP). The hippocampus helps turn new experiences into lasting memories, which are then gradually stored across the cortex. See Section 9.9 and Section 9.5.

Who was Patient H.M.?¶

Henry Molaison, known in research as "H.M.," had surgery in 1953 that removed parts of both of his temporal lobes, including much of the hippocampus, to treat severe epilepsy. Afterward, he could no longer form new memories of facts and events, but he could still learn new motor skills, like drawing while looking in a mirror, without remembering the practice. His case showed that different kinds of memory depend on different brain systems. See Section 9.6 and the glossary entry for Patient H.M..

Can an adult brain still change?¶

Yes. This ability is called neuroplasticity, and it is strongest early in life but continues in adults. Every new long-term memory changes synapses. One famous study found that London taxi drivers, who must memorize the city's maze of streets, had a larger back part of the hippocampus than people who did not drive taxis (Maguire et al., 2000). See Section 9.7.

What is the best way to study, according to brain science?¶

Two of the strategies with the most evidence behind them are spacing your study over several days and testing yourself instead of rereading. A major review of ten study techniques rated practice testing and distributed (spaced) practice the most useful, and rated rereading and highlighting low (Dunlosky et al., 2013). Try flashcards, practice questions, and short sessions spread out before a test. See Section 9.11.

Is pulling an all-nighter worth it before a big test?¶

Usually not. Sleep helps the brain stabilize new memories, and NINDS notes that forming and keeping new memories most likely requires both non-REM and REM sleep (NINDS). Skipping sleep also hurts attention the next day, right when you need it. Studying earlier and sleeping is usually the better trade. See Section 10.7.

How much sleep do teenagers need, and why is it so hard to fall asleep early?¶

The American Academy of Sleep Medicine recommends that teens aged 13 to 18 sleep 8 to 10 hours per 24 hours on a regular basis (Paruthi et al., 2016). Puberty shifts the body clock later, so many teens don't feel sleepy until late at night. That is a big reason the American Academy of Pediatrics recommends that middle and high schools start no earlier than 8:30 a.m. See Section 10.8.

What happens in the brain while I sleep?¶

Your brain stays busy all night. It cycles through light and deep non-REM sleep and then REM sleep, when most vivid dreaming happens and brain waves look a lot like being awake (NINDS). Each cycle takes about 90 minutes, and REM periods get longer toward morning. See Section 10.5.

What is narcolepsy?¶

Narcolepsy is a neurological sleep disorder, not just being very tired. In type 1 narcolepsy, the brain loses the neurons that make orexin (also called hypocretin), a chemical that keeps you steadily awake (NINDS). People can have sudden sleep attacks and cataplexy, brief muscle weakness often triggered by strong emotions like laughter. There is no cure, but treatments help manage symptoms. See Section 10.10 and the Chapter 10 bedside case.

Emotion, Stress, and Mental Health¶

Is the amygdala the brain's "fear center"?¶

That nickname is too simple. The amygdala flags anything emotionally important, including good things like rewards, and it helps make emotional memories stronger. Fear also depends on other areas, including the hypothalamus, hippocampus, and prefrontal cortex. See Section 11.4.

What happens in my body when I'm stressed? Is stress always bad?¶

Stress turns on two systems. Within seconds, the sympathetic nervous system releases adrenaline, which speeds your heart and breathing ("fight or flight"). Over minutes, the HPA axis releases cortisol, which supplies fuel. Short bursts of stress can actually help you perform, but stress that is too intense or never switches off can harm sleep, mood, and health. See Section 11.6 and Section 11.8.

What is PTSD, and can it be treated?¶

Post-traumatic stress disorder (PTSD) can develop after a frightening or dangerous event, when a person keeps feeling stressed or afraid even though they are no longer in danger (NIMH). It is not a sign of weakness. It reflects real changes in how the brain's fear and stress circuits learn and recover. Many people recover, and evidence-based therapies and medications can help. See Section 11.10 and the Chapter 11 bedside case.

Is depression caused by a "chemical imbalance"?¶

Not in the simple way that phrase suggests. A 2022 review found no consistent evidence that depression is caused by low serotonin (Moncrieff et al., 2022), though other researchers have debated how to read that evidence. Depression comes from many interacting biological, psychological, and social factors. That does not mean treatment doesn't work: therapy and medicines help many people. See Section 15.3.

How common are mental health conditions?¶

Very common. In the 2025 National Survey on Drug Use and Health, about 20.6% of U.S. adults (54.6 million people) had a mental illness in the past year (SAMHSA, 2026). You almost certainly know someone who has been affected. Talking about mental health openly, with respectful, person-first language, helps reduce stigma and makes it easier for people to get help. See Section 15.2 and Section 15.11.

Where can I get help if I or a friend is struggling?¶

If you or someone you know is in crisis or thinking about suicide, call or text 988 in the U.S., or chat at 988lifeline.org. It is free, confidential, and available 24/7. For help finding mental health or substance use treatment, call SAMHSA's National Helpline at 1-800-662-4357 (1-800-662-HELP), which is free, confidential, and available 24/7 (SAMHSA). Talking to a trusted adult, school counselor, or doctor is also a good first step. In an emergency, call 911.

Is addiction a choice or a lack of willpower?¶

No. The National Institute on Drug Abuse describes addiction as a chronic, relapsing disorder that changes the brain's circuits for reward, stress, and self-control (NIDA). Genes, together with the effects of environment on how genes work, account for an estimated 40 to 60 percent of a person's risk. Like heart disease, addiction is preventable and treatable. See Section 15.8.

Brain Disorders and Treatments¶

What is a stroke, and how can I spot one?¶

A stroke happens when blood flow to part of the brain is blocked by a clot (ischemic stroke) or when a blood vessel bursts (hemorrhagic stroke). Most strokes are ischemic. The CDC's BE FAST check is: Balance loss, Eye or vision changes, Face drooping, Arm weakness, Speech changes, Time to call 911 (CDC). Note when symptoms started, because treatment depends on time. See Section 14.7.

Do you have to be knocked out to have a concussion?¶

No. A concussion is a brain injury caused by a bump, blow, or jolt to the head, or a hit to the body that makes the head move quickly back and forth (CDC). Most concussions happen without any loss of consciousness. Anyone with a possible concussion should stop playing and be checked, and a worsening headache, repeated vomiting, or unusual drowsiness needs emergency care. See Section 14.3 and Section 14.4.

What should I do if someone has a seizure?¶

Stay with the person, keep them safe by moving hard objects away and cushioning their head, and turn them on their side. Time the seizure. Never hold them down or put anything in their mouth. Nobody can swallow their tongue. Call 911 if the seizure lasts longer than 5 minutes, if it is their first seizure, if they are injured or have trouble breathing, or if it happens in water (CDC). See Section 14.10.

Does having one seizure mean someone has epilepsy?¶

Not necessarily. A seizure is a burst of abnormal electrical activity in the brain, and it can be triggered by things like a high fever or very low blood sugar. Epilepsy is usually diagnosed after two or more unprovoked seizures at least 24 hours apart (NINDS). Many people with epilepsy control their seizures with medicine. See Section 14.9.

Is dementia a normal part of getting old?¶

No. Some slowing of memory and thinking speed is normal with age, like taking longer to recall a name. Dementia is different: it is caused by diseases, such as Alzheimer's disease, that damage the brain and interfere with daily life. Many people live into their 90s without dementia. See Section 13.2 and Chapter 13's Common Misconceptions.

Are there any treatments for Alzheimer's disease?¶

Yes, though none is a cure. Some medicines help with symptoms. Two anti-amyloid antibodies, lecanemab (traditional FDA approval in July 2023) and donanemab (FDA approval in July 2024), are approved for early-stage disease and modestly slow decline by clearing amyloid plaques. They can cause side effects, including brain swelling or small bleeds seen on MRI, so doctors monitor patients closely. See Section 13.7.

What are ALS and Huntington's disease?¶

ALS (amyotrophic lateral sclerosis) destroys the motor neurons that control muscles, causing weakness that spreads over time. Huntington's disease is caused by a repeated stretch of DNA (a "CAG repeat") in the HTT gene, and each child of a parent with it has a 50% chance of inheriting it (NINDS). Drugs that target genes are a newer approach. For example, tofersen received FDA accelerated approval in 2023 for ALS caused by mutations in the SOD1 gene. See Section 13.9 and Section 13.10.

What is naloxone?¶

Naloxone is a medicine that can quickly reverse an opioid overdose by knocking opioids off their receptors and restoring breathing (NIDA). It comes as a nasal spray or a shot, and in 2023 the FDA approved Narcan nasal spray for sale without a prescription. Signs of an overdose include very small pupils, slow or stopped breathing, and not waking up. Always call 911 too, because naloxone can wear off before the opioid does. See Section 15.10.

How Doctors Examine the Brain¶

What happens during a neurological exam?¶

A neurological exam is a head-to-toe check of how the nervous system is working, done mostly with simple tools like a reflex hammer and a light. The doctor checks mental status, the cranial nerves, strength, reflexes, sensation, and coordination and walking. Each part tests a different pathway, so the pattern of results points to where a problem is. See Section 16.4.

What does "where before what" mean in neurology?¶

Neurologists first figure out where in the nervous system the problem is, then what is causing it. For example, weakness of the right arm and right face plus trouble speaking points to the left hemisphere. Only then does the doctor rank possible causes, like stroke or tumor, which is called a differential diagnosis. See Section 16.2 and Section 16.5.

What's the difference between a CT scan and an MRI?¶

A CT scan uses X-rays, which are a form of ionizing radiation, to build cross-section pictures quickly. It is very good at showing bleeding in the brain (NIBIB). An MRI uses a strong magnet and radio waves instead of X-rays and shows soft tissue in more detail, but it takes longer (NIBIB). In a stroke emergency, a fast CT is often done first to check for bleeding. See Section 16.6.

Can a brain scan read your thoughts?¶

No. Scans measure physical things, like tissue density, water in tissue, blood oxygen, or electrical activity on the scalp. Functional MRI (fMRI) tracks changes in blood oxygen levels: when an area works harder, extra oxygen-rich blood flows in, which is a delayed, indirect sign of neural activity. It can show that a language area got busier, but not the sentence you were thinking. See Section 16.6 and the glossary entry for Functional MRI.

What is a lumbar puncture, and does the needle hit the spinal cord?¶

A lumbar puncture, or spinal tap, collects a small sample of cerebrospinal fluid (the fluid around the brain and spinal cord) to check for problems like infection or bleeding. The needle goes into the lower back, usually below the level where the spinal cord ends in adults, so it does not touch the cord (MedlinePlus). See Section 16.7.

Brain Bee and Careers¶

What is the Brain Bee?¶

The International Brain Bee is a neuroscience competition for teens, founded by Dr. Norbert Myslinski at the University of Maryland (International Brain Bee). Students usually compete first in a local Brain Bee. Local winners advance to their national competition, and national champions can compete in the IBB World Championship. The official FAQ says Brain Bees are typically open to students aged 13 to 19, but rules differ by chapter, so check yours. See Section B.5.

How can I use this book to prepare for the Brain Bee?¶

Read the chapters in order and do each MicroSim. After each chapter, try the quiz and the Brain Bee Practice questions without peeking, and keep a list of terms you miss to review in the Glossary. Study Chapter 16 and every bedside case for rounds that test patient diagnosis. Always check your own competition's official rules and study materials, which differ by chapter and year. See the Brain Bee path in How to Use This Book.

How long does it take to become a neurologist?¶

In the U.S., the usual path is about 4 years of college, 4 years of medical school (MD or DO), and a 4-year neurology residency, so roughly 12 years after high school. Neurosurgery takes longer, with a 7-year residency. Many doctors also add a fellowship to specialize in areas like stroke or epilepsy. See Section B.3.

Do I have to major in biology to go to medical school?¶

No. The Association of American Medical Colleges says most medical schools don't have a preference about your major (AAMC). You do need to take the required science courses, at minimum a year each of biology, general chemistry, organic chemistry, and biochemistry, and do well on the MCAT. Check each school's requirements. See Section B.3.

What careers use neuroscience besides being a doctor?¶

Many. Neuroscientists do research, nurses and physical, occupational, and speech therapists help patients recover, engineers build tools like brain-computer interfaces, data scientists analyze brain data, and teachers and science writers explain the brain to others. In high school, you can explore by taking strong science and statistics classes, joining or starting a neuroscience club, competing in the Brain Bee, volunteering, and shadowing professionals. See Appendix B.

Common Myths¶

Do we only use 10% of our brains?¶

No. Brain imaging shows that over the course of a day, practically every part of the brain is active, even during sleep (Scientific American). Damage to almost any brain area causes some problem. And the brain uses about a fifth of the body's energy, which would make no sense if 90% of it sat idle. See Chapter 1's Common Misconceptions.

Are some people "left-brained" and others "right-brained"?¶

No. Some functions do lean to one side. For example, language relies more on the left hemisphere in most people. But a study of brain scans from 1,011 people aged 7 to 29 found no evidence that people have an overall stronger left or right brain network (Nielsen et al., 2013). Logic, creativity, math, and art all draw on both hemispheres. See Section 12.5 and Chapter 4's Common Misconceptions.

Does listening to Mozart make you smarter?¶

No good evidence says so. A 1993 study reported a short-lived boost on one kind of spatial task after listening to Mozart, which became known as the "Mozart effect." Later analyses pooling many studies found the effect was small, short-lived, and likely due to music putting people in a better mood or more alert state, not to Mozart specifically (Chabris, 1999; Pietschnig et al., 2010). Enjoy music for its own sake, but don't count on it to raise your IQ.

Do people learn best in their own "learning style" (visual, auditory, or kinesthetic)?¶

People do have preferences, but there is little evidence that matching teaching to a person's preferred style helps them learn more. A major 2008 review found virtually no well-designed studies supporting that idea, and the few that existed contradicted it (Pashler et al., 2008). Strategies like spacing and self-testing help nearly everyone. See Chapter 9's Common Misconceptions.

Do brain-training apps and games make you smarter?¶

People do get better at the specific games they practice. But a large 2016 review found little evidence that those gains carry over to different tasks or to everyday life, like school performance (Simons et al., 2016). In 2016, the maker of the Lumosity app agreed to pay $2 million to settle U.S. Federal Trade Commission charges that its brain-health advertising claims were deceptive (The Scientist). Chapters 9 and 10 explain how practice and sleep help your brain learn.

Does a bigger brain mean a smarter person?¶

Only weakly. A 2015 analysis of more than 8,000 people found that brain size explains only about 6% of differences in IQ test scores (Pietschnig et al., 2015). Size is only a small part of what makes one brain different from another. See Chapter 4's Common Misconceptions.