10 Amazing Facts About the Infant Brain

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While there’s little argument that babies are generally cute, it’s far more difficult to determine how intelligent they are, since we can’t measure their know-how by standards of adult brain development. Yet infants’ brains develop so rapidly they are pure, consolidated potential in their first three years. Consider that a 4-week-old fetus forms new neurons at a rate of 250,000 every minute, and by the time a child is three, their brain will reach 80 percent of adult volume and process close to 1000 trillion connections between neurons. Here are 10 mind-blowing facts about the amazing infant brain.

1. ALL BABIES ARE BORN "EARLY."

Thanks to the size of the average human birth canal, and the heavy metabolic burden a baby places on its mother in gestation, a baby’s head can only be so big and still emerge from its mother, which means babies are born with underdeveloped brains that are hypersensitive to stimulus. One popular theory explaining this is that their first three months of life outside the womb equal a “fourth trimester” which may be why newborns like to be wrapped tightly and respond well to loud white noise, details which mimic the conditions of life in utero. Further theory suggests that humans are designed to be social and cultural animals, and that being born earlier may allow an infant’s brain to soak up the many impressions and senses of being raised within a group of people. 

2. BABIES ARE BORN WITH ALL THE NEURONS THEY WILL EVER HAVE. 

Assuming normal development, a healthy baby will emerge from the womb with 100 billion neurons, nearly twice as many neurons as adults, in a brain that’s half the size. This massive number of neurons is necessary for the tremendous amount of learning a baby has to do in its first year of life. While brain volume will double by the age of 3, not all of those neurons will stick around; synaptic pruning takes place as a baby ages, in which the brain gets rid of weaker synaptic connections in favor of stronger ones.  

3. BIRTH TO AGE 3 SEES THE FASTEST RATE OF BRAIN DEVELOPMENT IN THE ENTIRE HUMAN LIFE SPAN.

Though you may think your darling is growing like a weed as chubby toddlerhood gives way to lanky kid, in the first three years of your child’s life, their brain is growing faster than any other body part. At birth, a baby's brain is about one-third the size of an adult's brain. In 90 days, it more than doubles its volume, to 55 percent of its final size. The cerebellum in particular, a brain structure at the back of the brain involved in controlling movement, grows the fastest of all brain structures; in just three months it will be 110 percent bigger than it was at birth.

4. MOST OF THE ENERGY A BABY EXPENDS IS CONCENTRATED IN THE BRAIN.

As a result of all that rapid brain development, 60 percent of a baby’s metabolic energy (primarily the consumption of glucose) is spent on growing those soon-to-be massive brains. In contrast, the brain of an adult uses only about 25 percent of the body’s metabolic energy. 

5. BABIES' BRAINS PREPARE FOR SPEECH LONG BEFORE THEY UTTER A WORD. 

A study of 7-month-old babies at the University of Washington showed activation of motor parts of babies’ brains associated with the physical aspects of speech—Broca’s area and the cerebellum—before they actually began to speak. This suggests that the brain sets up a transitional groundwork in a process known as “analysis by synthesis” in which the brain predicts the motor movements that will be required to make the sounds of speech and prepares to do so.

6. BILINGUAL BABIES' BRAINS HAVE STRONGER EXECUTIVE FUNCTION.

Not only are babies capable at birth of learning any language, those babies who are spoken to regularly in two or more languages have better executive function later in life, specifically the ability to control attention to conflicting perceptual or representational features of a problem. In other words, bilingual children have better attention or focus, which bodes well for school and work performance. 

7. PHYSICAL TOUCH STRENGTHENS BABIES' SYNAPSES.

Babies who receive regular touch have stronger neuronal connections, and greater overall well-being. It’s well known now that babies who are deprived of touch suffer a number of negative health effects, from low weight to emotional disorders such as anxiety and depression. A study of 92 7- to 9 year-olds, who had previously been studied in preschool, showed that those who had received more nurture by their mothers (or caregivers) had a thicker hippocampus than those who were not as well nurtured. A stronger hippocampus is associated with improved memory, better focus, ability to retain learning, and more.

8. BABY BRAINS ARE HARDWIRED TO PREFER THEIR MOTHER'S SCENT.

Much of the infant-mother bond in the early days is determined by smell and touch, more specifically the bonding hormone oxytocin, which can induce a feeling of euphoria and love in humans. Studies have shown that babies are imprinted with, and attracted to, the scent of their own amniotic fluid, which helps them to find their mother’s nipple. Over several days, healthy babies grow to prefer the scent of their mother’s breast. One study even showed that formula-fed babies still prefer the odor of their mother’s breast to that of their formula up to two weeks after birth.

9. A BABY'S UNWILLINGNESS TO LEAVE A PARENT SIGNALS THE DEVELOPMENT OF LONG-TERM MEMORY.

Mothers who find they must pry a suddenly crying baby off of them when they prepare to leave might be relieved to know it may be the earliest signs of long-term memory development. Jerome Kagan, a Harvard University professor of psychology, suggests that around 9 months, an infant’s unwillingness to leave their parent is a sign that the child has a clear memory of his or her mother “being there” and can now form an emotional association to the event. 

10. HYPOTHERMIA CAN PROTECT NEWBORN BRAINS. 

A new study at Children’s Hospital Los Angeles of newborns treated for hypoxic-ischemic encephalopathy (HIE)—a condition that occurs when the brain is deprived of an adequate oxygen supply—found that inducing hypothermia through a targeted cooling of the brain had a neuroprotective effect.

Without treatment, these babies often develop cerebral palsy or other severe complications that affect as many as 1 million babies worldwide. The study found that hypothermia works by reducing energy metabolism, but also reduced the synthesis of glutamate and other excitatory neurotransmitters.   

Why Can You Sometimes See Your Breath?

Chalabala/iStock via Getty Images
Chalabala/iStock via Getty Images

The human body is made up of about 60 percent water, meaning that when we breathe, we don’t just exhale carbon dioxide—we also exhale a certain amount of water vapor.

Water molecules need a lot of energy in order to remain in a gaseous form. When the warm water vapor molecules from your lungs reach colder air, they condense into “tiny droplets of liquid water and ice,” according to Wonderopolis. In fact, this process of condensation is also how clouds are formed.

But it’s actually relative humidity, not just temperature, that determines whether you can see your breath. The water vapor in your breath condenses into a liquid when it hits dew point—the temperature at which the air is saturated and can’t hold any more water in gas form. Since cold air can’t hold as much water vapor as warm air, you're much more likely to see your breath on a chilly day, but that's not always the case.

On more humid days, you may be able to see your breath even when it’s relatively warm outside. That’s because the air is already more saturated, making the dew point higher. And on especially dry days, even if it's cold outside, you may not be able to see your breath at all. Dry, unsaturated air can hold more water vapor, so you can huff and puff without seeing any evidence of it at all.

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7 Facts About Blood

Moussa81/iStock via Getty Images
Moussa81/iStock via Getty Images

Everyone knows that when you get cut, you bleed—a result of the constant movement of blood through our bodies. But do you know all of the functions the circulatory system actually performs? Here are some surprising facts about human blood—and a few cringe-worthy theories that preceded the modern scientific understanding of this vital fluid.

1. Doctors still use bloodletting and leeches to treat diseases.

Ancient peoples knew the circulatory system was important to overall health. That may be one reason for bloodletting, the practice of cutting people to “cure” everything from cancer to infections to mental illness. For the better part of two millennia, it persisted as one of the most common medical procedures.

Hippocrates believed that illness was caused by an imbalance of four “humors”—blood, phlegm, black bile, and yellow bile. For centuries, doctors believed balance could be restored by removing excess blood, often by bloodletting or leeches. It didn’t always go so well. George Washington, for example, died soon after his physician treated a sore throat with bloodletting and a series of other agonizing procedures.

By the mid-19th century, bloodletting was on its way out, but it hasn’t completely disappeared. Bloodletting is an effective treatment for some rare conditions like hemochromatosis, a hereditary condition causing your body to absorb too much iron.

Leeches have also made a comeback in medicine. We now know that leech saliva contains substances with anti-inflammatory, antibiotic, and anesthetic properties. It also contains hirudin, an enzyme that prevents clotting. It lets more oxygenated blood into the wound, reducing swelling and helping to rebuild tiny blood vessels so that it can heal faster. That’s why leeches are still sometimes used in treating certain circulatory diseases, arthritis, and skin grafting, and helps reattach fingers and toes. (Contrary to popular belief, even the blood-sucking variety of leech is not all that interested in human blood.)

2. Scientists didn't understand how blood circulation worked until the 17th century.

William Harvey, an English physician, is generally credited with discovering and demonstrating the mechanics of circulation, though his work developed out of the cumulative body of research on the subject over centuries.

The prevailing theory in Harvey’s time was that the lungs, not the heart, moved blood through the body. In part by dissecting living animals and studying their still-beating hearts, Harvey was able to describe how the heart pumped blood through the body and how blood returned to the heart. He also showed how valves in veins helped control the flow of blood through the body. Harvey was ridiculed by many of his contemporaries, but his theories were ultimately vindicated.

3. Blood types were discovered in the early 20th century.

Austrian physician Karl Landsteiner discovered different blood groups in 1901, after he noticed that blood mixed from people with different types would clot. His subsequent research classified types A, B and O. (Later research identified an additional type, AB). Blood types are differentiated by the kinds of antigens—molecules that provoke an immune system reaction—that attach to red blood cells.

People with Type A blood have only A antigens attached to their red cells but have B antigens in their plasma. In those with Type B blood, the location of the antigens is reversed. Type O blood has neither A nor B antigens on red cells, but both are present in the plasma. And finally, Type AB has both A and B antigens on red cells but neither in plasma. But wait, there’s more! When a third antigen, called the Rh factor, is present, the blood type is classified as positive. When Rh factor is absent, the blood type is negative.

Scientists still don’t understand why humans have different blood types, but knowing yours is important: Some people have life-threatening reactions if they receive a blood type during a transfusion that doesn’t “mix” with their own. Before researchers developed reliable ways to detect blood types, that tended to turn out badly for people receiving an incompatible human (or animal!) blood transfusion.

4. Blood makes up about 8 percent of our total body weight.

Adult bodies contain about 5 liters (5.3 quarts) of blood. An exception is pregnant women, whose bodies can produce about 50 percent more blood to nourish a fetus.)

Plasma, the liquid portion of blood, accounts for about 3 liters. It carries red and white blood cells and platelets, which deliver oxygen to our cells, fight disease, and repair damaged vessels. These cells are joined by electrolytes, antibodies, vitamins, proteins, and other nutrients required to maintain all the other cells in the body.

5. A healthy red blood cell lasts for roughly 120 days.

Red blood cells contain an important protein called hemoglobin that delivers oxygen to all the other cells in our bodies. It also carries carbon dioxide from those cells back to the lungs.

Red blood cells are produced in bone marrow, but not everyone produces healthy ones. People with sickle cell anemia, a hereditary condition, develop malformed red blood cells that get stuck in blood vessels. These blood cells last about 10 to 20 days, which leads to a chronic shortage of red blood cells, often causing to pain, infection, and organ damage.

6. Blood might play a role in treating Alzheimer's disease.

In 2014, research led by Stanford University scientists found that injecting the plasma of young mice into older mice improved memory and learning. Their findings follow years of experiments in which scientists surgically joined the circulatory systems of old and young mice to test whether young blood could reverse signs of aging. Those results showed rejuvenating effects of a particular blood protein on the organs of older mice.

The Stanford team’s findings that young blood had positive effects on mouse memory and learning sparked intense interest in whether it could eventually lead to new treatments for Alzheimer’s disease and other age-related conditions.

7. The sight of blood can make people faint.

For 3 to 4 percent of people, squeamishness associated with blood, injury, or invasive medical procedures like injections rises to the level of a true phobia called blood injury injection phobia (BII). And most sufferers share a common reaction: fainting.

Most phobias cause an increase in heart rate and blood pressure, and often muscle tension, shakes, and sweating: part of the body’s sympathetic nervous system’s “fight or flight” response. But sufferers of BII experience an added symptom. After initially increasing, their blood pressure and heart rate will abruptly drop.

This reaction is caused by the vagus nerve, which works to keep a steady heart rate, among other things. But the vagus nerve sometimes overdoes it, pushing blood pressure and heart rate too low. (You may have experienced this phenomenon if you’ve ever felt faint while hungry, dehydrated, startled, or standing up too fast.) For people with BII, the vasovagal response can happen at the mere sight or suggestion of blood, needles, or bodily injury, making even a routine medical or dental checkup cause for dread and embarrassment.

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