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The Amazing Infant Brain

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We may be biased, but we think the human brain is pretty special. All this week, mentalfloss.com is celebrating this miracle organ with a heap of brain[y] stories, lists, and videos. It all leads up to Brain Surgery Live With mental_floss, a two-hour television event hosted by Bryant Gumbel. The special airs Sunday, October 25 at 9 p.m. EST on the National Geographic Channel.

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.   

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techbint, Flickr // CC BY 2.0
7 Famous Human Brains and Brain Collections You Can Visit
Original image
techbint, Flickr // CC BY 2.0

We may be biased, but we think the human brain is pretty special. All this week, mentalfloss.com is celebrating this miracle organ with a heap of brain[y] stories, lists, and videos. It all leads up to Brain Surgery Live With mental_floss, a two-hour television event that will feature—yes—live brain surgery. Hosted by Bryant Gumbel, the special airs Sunday, October 25 at 9 p.m. EST on the National Geographic Channel.

Scientists have been collecting human brains ever since the techniques to preserve them were perfected in the mid 19th century. These days, many of those collections languish in basements and back rooms—thanks to imperfect preservation, lack of funding, and the decreased need to study actual specimens in an age where we can scan the brains of living patients with sophisticated techniques.

Fortunately, a few of the world’s most interesting brains and brain collections are on view to the public. Some of these collections were amassed to study neurological issues, while others were put together in a failed attempt to correlate brain size with race, sex, and intelligence. (Despite what many scientists once thought, humans with larger brains aren’t necessarily more intelligent.) Below, seven collections to help you create your own brain-based travel itinerary:

1. EINSTEIN // MÜTTER MUSEUM

It seems fitting that you can see the brain of the man who became practically synonymous with the term during the 20th century: Albert Einstein. Since 2011, the Mütter Museum in Philadelphia has owned 46 slides of Einstein’s gray matter, stained with cresyl violet and mounted on glass slides. Neuropathologist Lucy Rorke-Adams donated them to the museum in 2011, after receiving them from a colleague in the 1970s. 

Ironically, Einstein might have balked at the idea of having his brain on display. He told friends and family he wanted to be cremated after his death, so no one would “worship at his bones.” Most of his body was cremated, but the pathologist on duty during his autopsy, a man named Thomas Harvey, decided to take the brain in order to study. He wanted to see if he could find any kind of neuroanatomical evidence of what make Einstein so brilliant. (Einstein’s family was furious, and Harvey only received retroactive permission to keep the brain for scientific analysis. He’s frequently been portrayed as a thief, but pathologists at the time often saved organs from autopsies.) Since then, it’s been a long, strange trip—and the research about whether Einstein’s brain had anything to do with his intelligence is still inconclusive. (Later this week we'll talk to Dean Falk, a researcher who studied Einstein's brain, about the evolution of the human brain.)  

2. PAUL BROCA’S SPECIMENS // MUSÉE DUPUYTREN

The Musée Dupuytren in Paris’ Latin Quarter is crammed to the ceiling with hundreds of skeletons, wax moulages of skin diseases, and organs floating in glass jars. It’s also home to two of the most famous brain specimens in the history of science.

In 1861, the eminent French surgeon and anthropologist Paul Broca was the first to prove the doctrine of cerebral localization—the idea that a particular part of the brain could be responsible for a particular function. Broca’s autopsies on two aphasic patients, a Mr. Leborgne and a Mr. Lelong, showed a link between lesions in the third convolution of the left frontal lobes and speech loss (patients with the lesions couldn’t form articulate speech, but only repeat a few basic words or syllables). Broca’s research paved the way for modern neuroscience, and the speech production center of the brain is now named Broca’s Area.

Today the brains of Leborgne and Lelong sit alongside the other eerie anatomical oddities at the Musée Dupuytren, housed in what was once a 15th-century refectory. Even Broca’s own brain is sometimes said to be inside the museum, but staff claim that’s not the case; the whereabouts of the scientist’s own brain seem to be something of a mystery. For now, visitors have to be content with seeing the brains of his most famous patients.

3. CHARLES BABBAGE // LONDON (TWO LOCATIONS)

Babbage's brain at the Science Museum in London. Image credit: Anne-Lise Heinrichs, Flickr // CC BY 2.0

English mathematician, inventor, and engineer Charles Babbage is often credited as the “father of the computer”—his Difference Engine No.1, invented in 1821, was the first successful automatic calculator, and his later “analytical engines” shared characteristics with today’s computers. Babbage is also frequently remembered for his work with Ada Lovelace, Lord Byron’s daughter, who some consider the first computer programmer.

Always a forward-thinker, Babbage also donated his brain to science. Today it’s on display in two places in London: half is at the Science Museum, and the other half at the Hunterian Museum in the Royal College of Surgeons. You can see a video of it here.

4. CORNELL BRAIN COLLECTION

The Cornell Brain Collection was assembled by the noted anatomist Burt Green Wilder, creator of Cornell University’s anatomy department and founder, in 1889, of the Cornell Brain Society, devoted to collecting the brains of "educated and orderly persons.” Wilder hoped to show how such brains differed from those of criminals, minorities, the mentally ill, and women. Research showed they didn’t—at least not in ways observable by 19th-century technology.

At its peak, the collection included hundreds of specimens. Today, while 70 unidentified brains are housed in a Cornell basement, eight identified specimens are on display at the university’s Uris Hall alongside text explaining their biographies. Notable items include the brain of Helen Hamilton Gardener, an author, activist, and civil servant who donated her brain intending to prove that women were just as intelligent as men—and that their brains could be just as big.

Wilder even donated his own brain to the collection, and it remains on display. Also on view: the brain of murderer Edward H. Rulloff, turned a minty green thanks to poor preservation techniques.

5. CUSHING CENTER BRAIN TUMOR REGISTRY

 For decades, the brains in Yale’s Cushing Center collection languished in the basement of the Harkness Dormitory, where breaking in to see them was a ritual among medical students. Today, the brains sit in a well-appointed display that cost $1.5 million to create—a somewhat rare concentration of resources for a brain collection, which these days often stay hidden in storage rooms.

The brains were collected by Dr. Harvey Cushing, a neuroscience professor at Yale and a pioneer of modern neurosurgery, who willed them to the school upon his death. The most famous specimen belonged to Leonard Wood, who served as the personal physician to two presidents as well as Army Chief of Staff. Cushing successfully removed a large tumor from Wood’s brain in 1910, ending his seizures—one of the few such successful operations at the time. Sadly, Wood died in 1927 after an operation to remove a second tumor.

The brains are also notable for being displayed with before-and-after photos of the patients—less harrowing and more fascinating than they sound. Cushing’s journals, surgical instruments, and other specimens complete the exhibit.

6.  PERU BRAIN MUSEUM

The little-known Brain Museum at the Institute of Neurological Science in Lima, Peru, contains close to 3000 specimens, many of which show the marked effects of Alzheimer’s, alcoholism, tumors, or stokes. One of the star brains belonged to someone who suffered from Creutzfeldt-Jakob disease, sometimes called “human mad cow disease,” and which has been caused by some tribes eating human brains as part of their funerary practices. (On the other hand, at least one tribe appears to have developed a genetic resistance to the disease thanks to its former brain-eating ways.) The museum has been collecting specimens since 1947 and is one of the few large collections of brains that’s regularly open to the public.

7. TRAUMATIC BRAIN INJURY EXHIBIT // NATIONAL MUSEUM OF HEALTH AND MEDICINE

The National Museum of Health and Medicine in Washington, D.C. holds eight different neuroanatomical collections—but the specimens are off-limits except for researchers with an appointment. However, if brains are your thing and you don’t have a PhD., you can still check out the museum’s Traumatic Brain Injury exhibit, which is open to the public. The exhibit features 30 specimens with a host of brain damage, including hemorrhages, blunt force trauma, and bullet wounds, as well as the surgical tools used to treat said injuries. It sounds fascinating, but maybe don’t visit right after lunch.

Trepanation: The History of One of the World's Oldest Surgeries

During the 1860s, a United States diplomat named E.G. Squier traveled to Cuzco, Peru. While visiting the home of a wealthy woman who collected antiquities, he was shown an ancient skull. Discovered in an ancient Inca cemetery in the Valley of Yuca, the skull dated to pre-Columbian times and had a large, rectangle-shaped hole near its top front.

Squier—a well-educated polymath whose areas of expertise also included archaeology and Latin American culture—was immediately intrigued. So in 1865, Squier brought the skull to New York, where he presented it to members of the New York Academy of Medicine.

Squier believed that the skull was clear evidence that Peru’s ancient people had performed prehistoric brain surgery. The hole’s cross-hatched outlines were the work of a human hand; Squier noted that they were most likely made with a burin, a tool used by engravers on wood and metal. Even more shockingly, he observed, the skull showed signs of healing—meaning the patient had survived the procedure for at least one to two weeks before they died.

Members of the medical community were skeptical, and didn't believe that the cuts were made prior to death. So Squier sought the opinion of renowned French surgeon and anthropologist Paul Broca. In turn, Broca looked at the skull, and concluded that early indigenous societies had been performing “advanced surgery” long before Europeans arrived.

The practice of drilling or scraping a hole into the skull’s cranial vault to expose the brain’s dura mater and treat brain injuries is called trepanation. First mentioned by the Hippocratic corpus, it’s one of the world’s oldest surgeries. (In fact, the word trepanation comes from Greek, and means “auger” or “borer.”) Today, the medical community would refer to it as a craniotomy.

Throughout history, trepanation has been practiced in nearly every part of the world. It was performed in ancient Greece and Rome, and is today even reportedly used in parts of Africa, South America, and the South Pacific. In ancient Greece, it was used to relieve pressure, remove skull fragments from the brain after a traumatic accident, and for drainage. From the Renaissance until the beginning of the 19th century, trepanation was routinely used to treat head wounds, and into the 18th century, it was used to treat epilepsy and mental disorders.

The Victorian physicians of Squier and Broca's time had never considered that “primitive” cultures throughout history may have attempted the procedure. Also, since survival rates from the surgery were so poor due to hospital-acquired infections, they doubted that ancient patients could have lived for long following the operation.

After Broca acknowledged Squier’s find, scientists began discovering trepanned skulls across the globe, dating back to the Neolithic period. Hole-filled heads were discovered in Western Europe, South America, and the Americas. Over the years, it became clear that trepanation was attempted by many societies across the globe, starting in the late Paleolithic period.

Techniques varied from culture to culture. Prehistoric trepanations performed in early Peru were done with a ceremonial knife called a tumi, which was used to scrape or cut through the bone. The Hippocratic school invented the trephine drill, which bored holes into the skull. In the South Pacific, they sometimes used sharpened seashells; in Europe, flint and obsidian. By the Renaissance period, trepanation was routinely performed, and a range of instruments had been developed. However, due to the high infection rate, the practice soon waned.

Trepanation was performed on young and old, male and female. In many instances, the prehistoric patients had lived for years after the surgery. According to writings by Charles Gross, a professor of neuroscience at Princeton University, estimates for survival range from 50 to 90 percent. However, in many cases, the surgeon's motive for performing trepanation remains unclear.

John Verano, a professor of anthropology at Tulane University who studies trepanation in Peru, tells mental_floss he's convinced that “in Peru, the South Pacific, and many other parts of the world, trepanation began as a very practical treatment for head injuries. Say somebody has a head wound that’s torn up their skull. You’d clean it out and remove little broken fragments and allow the brain to swell a little bit, which it does after injuries.”

In some instances, trepanned skulls show clear evidence of trauma—meaning there must have been an underlying reason why the procedure was performed. However, archaeologists have also uncovered trepanned skulls that don’t show depressed fractures. Squier's famous skull, for instance, didn't indicate any signs of a head wound. Skulls with multiple holes have also been unearthed, revealing that patients sometimes had—and survived—more than one surgery.

According to Verano, modern eyewitness accounts from Africa and the South Pacific state that trepanation is still used to treat head wounds, headaches, or pressure on the brain. In other parts of the world, it’s thought that trepanation might have once been used to release evil spirits, or to treat insanity or epilepsy. But without any written record, we’ll never quite know why these kinds of surgeries were performed in the absence of obvious injury.

Individuals who underwent trepanation weren't administered anesthesia. Did the procedure hurt?

As Verano points out, they might have likely been unconscious during the surgery if they had suffered a head wound. Otherwise, they would have been awake. “The scalp has a lot of nerves, so it hurts to cut your scalp,” Verano says. “It also bleeds a lot, but then it stops. But the skull has very few nerves, and the brain has no nerves.” But Verano also points out that ancient trepanners weren’t cutting through the brain’s dura mater. (If they did, the patient would have gotten meningitis and died.) 

In today’s modern Western hospital, trepanation is no longer viewed as its own curative procedure. It’s used to debride a wound (remove dead or infected tissue), relieve pressure in the skull, or perform exploratory surgery. However, it’s fascinating to realize that the surgery survived many millennia—and that as early as prehistoric times, humans were already connecting the brain’s functioning to the body. We can only wonder what people of the future will think of our own modern brain surgeries

Additional Sources: A Hole in the HeadTrepanation (Studies on Neuropsychology, Development, and Cognition)

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