Winston Churchill famously called Russia a "riddle wrapped in a mystery inside an enigma," but Churchill's renowned line could just as easily be applied to the human brain. There's so much we don't know about this complex organ. What is its role in human consciousness? How does it store -- and lose -- memories? And what is it doing while we sleep each night? These mysteries ensure that neuroscientists will have jobs for many years to come.
But while it seems like the human brain will never give up its secrets, it's important to realize just how much we've learned about it in the last few centuries. The brain has been a subject of research since the time of ancient Egypt, and this article celebrates some of the biggest accomplishments scientists have made since then.
10: Camillo Golgi and Santiago Ramon y Cajal Form an Unlikely Partnership
In 1906, Camillo Golgi and Santiago Ramon y Cajal shared the Nobel Prize in Physiology or Medicine. The two scholars met for the first time at the awards ceremony and gave acceptance speeches that were contradictory about the work for which they were being honored. Nonetheless, the two men's work formed the basis for all that we know about the basic structure of the brain.
In the 1870s, Golgi developed a means for staining the brain that was far more advanced than any other technique of its day. His staining technique allowed scientists to see for the first time the individual tissues and cells of the brain. Santiago Ramon y Cajal was the leading proponent of the idea that what scientists were seeing were individual nerve cells, as opposed to some sort of continuous network of cellular tissue. These nerve cells had been christened "neurons" by H. Waldeyer-Hartz in 1891, but it was Ramon y Cajal who used Golgi's staining method to prove that these individual neurons formed the operating structure of the nervous system. Golgi, despite the images his method produced, remained in the camp of researchers who believed neurons were continuous, which is why the two men's speeches sharply diverged when they received the Nobel.
9: Paul Broca Discovers the Seat of Language
The patient could only say one thing: "tan." He died a few days after French surgeon Paul Broca first met him in the 1860s. When Broca saw the patient's brain, he found a lesion on the surface of the left frontal lobe. Did the damage to this particular spot cause the patient's loss of language?
Broca met a second patient with speech problems, who, upon death, exhibited the same sort of brain damage; more and more patients followed. Broca documented these cases and established the connection between speech and the left frontal lobe. The surgeon's worked marked the first time that certain sections of the brain could be tied definitively to particular tasks, a precept that serves as the foundation for nearly every neuroscientist's work today.
Sharing a secret? We know more about language thanks to Paul Broca.
Image Credit: Tom Grill/Photographer's Choice RF/Getty Images
8: Alois Alzheimer Works with Auguste D
As we age, there are certain things we look forward to: retirement, grandchildren, senior citizen discounts. But even as we contemplate such perks, the dark cloud of dementia lurks. This condition, marked by a loss of brain function, strikes fear into people's hearts. It seems unfair that at a moment when we should be able to enjoy a life well-lived, we might lose our memories of that life.
While scientists remain hard at work learning about dementia, we must applaud the efforts of Alois Alzheimer, who described the disease that bears his name in 1906. Alzheimer met a woman named Auguste D in a German hospital, where she was receiving care for strange behavior, paranoia and memory problems. He interviewed the woman many times and then studied her brain after her death. In 1906, he gave a lecture describing the symptoms of this type of dementia and linked it to the plaques and tangles he found on her brain. Alzheimer's description of these defining features of the condition paved the way for the researchers working to prevent and treat it today.
7: Otto Loewi Has a Significant Dream
In 1921, Otto Loewi had a dream about an experiment that would prove whether synaptic signaling was chemical or electrical. He woke up, made a few notes about what he intended to do, and fell back to sleep. Come morning, though, Loewi couldn't read his handwriting, and he feared his breakthrough was lost forever. He had the same dream the next night, though, and rather than take any chances, he went into his lab in the wee hours of the morning to conduct the experiment. Loewi took two beating frog hearts, bathed them in a saline solution, and mechanically slowed down the first heart. He then applied the solution from the first heart to the second heart, which caused it to slow down as well. The slowdown indicated that there was some sort of chemical in the first heart's saline solution that affected the second heart. This chemical was eventually discovered to be acetylcholine, which had been identified by Loewi's good friend Henry H. Dale. The two men shared the Nobel Prize in 1936 for researching how chemical transmission between neurons, via neurotransmitters such as acetylcholine or norepinephrine, takes place.
If you dream about experimenting with frogs, you should probably pay attention!
Image Credit: Comstock/Thinkstock
6: Walter Cannon Describes 'Fight or Flight'
In 1929, physiologist Walter B. Cannon coined the term "fight or flight" to describe the response animals have to external threats. Cannon's work was immensely important to understanding the link between the brain and stress.
When we encounter a stressful situation, our brain goes to work. It enlists three communication systems -- the voluntary nervous system, the autonomic nervous system and the neuroendocrine system -- to send messages and hormones throughout the body. As a result, we experience physical symptoms such as the quickening of the heart, sweaty palms and constricted blood vessels. These responses prime the human body to take on the threat or to run away from it, which demonstrates the role that our brains have played in our survival.
Researchers have used Cannon's work to learn more about how stress affects the body and the brain, and doctors have used the research to help patients defuse stressful situations. If you can train your brain not to see certain situations as stressful, you can avoid the resultant physical effects.
5: H.M.'s Amnesia Provides Clues to Human Memory
H.M. is one of the most famed patients in all of neuroscience, and it's thanks to him that we have an understanding of how memory works in the brain. H.M. (so named to maintain his privacy) had a severe form of epilepsy, and in 1953, surgeon William Scoville performed an experimental operation to correct it. The surgery, which removed parts of H.M.'s temporal lobes, left H.M. with profound amnesia; the young man was unable to form new memories or remember the names of people he met. Scoville brought psychologist Brenda Milner onto the case, and she spent hours with H.M. administering various memory tests. Before this work, scientists thought that memories were distributed throughout the brain, but Drs. Scoville and Milner were able to tie H.M.'s amnesia to the parts of the brain that had been removed. One of Milner's tests also demonstrated how different types of memory were maintained in different parts of the brain. Because H.M. could learn new tasks, scientists realized there was a subconscious motor learning system that was distinct from the declarative memory system. The latter system is governed by the hippocampus and is responsible for memories like names, faces and experiences.
4: Brain Imaging Devices Provide a Peek Inside the Brain
A good map can make or break an expedition, and the landscape of the brain is no exception. Though the dead have offered up their brains for centuries, advances in neuroimaging have allowed researchers to study living brains in detail. In 1918, neurosurgeon Walter Dandy pioneered ventriculography, which involved injecting air into the brain, and in 1927, Egas Moniz introduced cerebral angiography, which used contrast agents to produce images of the blood vessels. Both methods had the potential for dangerous side effects, though.
Neuroimaging hit its stride in the 1970s and 1980s, when computerized axial tomography (CAT scanning), positron emission tomography (PET scanning) and magnetic resonance imaging (MRI) were introduced. These sophisticated scanning tools allowed researchers to see specific slices of the brain, observe how blood flows in the brain, and detect changes in the brain over time. In the early 1990s, functional MRI (fMRI) revolutionized the field of neuroscience because it provides a glimpse of how the brain is actually working. With fMRI, researchers are learning what the brain does when provided with certain stimuli, and some researchers have been able to predict what a person will do when faced with a decision, based solely on brain activity.
3: Prozac Gains Wide Acceptance
In 1946, President Harry Truman signed the National Mental Health Act. With the end of World War II, the United States was greeting soldiers who were returning home far different from who they were when they'd left. Depression and mental illness were subjects not mentioned in polite society, but the need for an organization to tend to the shell-shocked soldiers was necessary.
The 1950s were an extremely productive time in the field of mental health. Most notably, researchers began to learn more about how medication could affect brain chemistry, which led to a class of treatment that didn't involve lobotomy, electroshock or psychoanalysis. In 1954, the Food and Drug Administration (FDA) approved chlorpromazine, which had an immense calming effect, and by 1964, 50 million people around the world had taken the drug [source: PBS]. Other antidepressants and medications for mental illness followed, but few had the impact of Prozac, or fluoxetine, which was introduced in 1987. Prozac had fewer side effects than previous drugs and has been prescribed for everything from depression to eating disorders. Though some researchers believe that the drug is overused, it helped destigmatize mental illness, and it helped some people get life-saving help for mental illness.
Prozac has been linked with suicide attempts and violence.
Image Credit: Stephen Chernin/Getty Images
2: Italian Researchers Identify Mirror Neurons
If you've ever sat through a presentation made by someone who's extremely nervous, you may have noticed yourself getting nervous as well. And if you've ever watched someone trip and fall in a bustling school cafeteria, you might have experienced pangs of sympathy at the person's plight. But why do the activities of complete strangers evoke such reactions from us? Italian researchers may have solved that puzzle in the 1980s and 1990s, when they identified mirror neurons. The researchers claimed that watching and performing an action causes the same neurons to fire, so simply seeing a person go through an embarrassing, triumphant or nerve-wracking situation could cause us to feel as if we had gone through it ourselves. Mirror neurons could be involved in empathy and acquisition of language, while a deficiency of mirror neurons could help to explain autism.
1: Neuroplasticity Portends Decades of New Discoveries
One of the most recent achievements in neuroscience is also one of the most significant, heralding the next age of brain exploration. For centuries, scientists thought the brain became a fixed, unchanging object after its initial development in younger years. We're born with all of the neurological equipment we'll ever have and our early education shapes and molds the brain's landscape -- but if something goes wrong in older years, tough luck. In recent years, though, researchers have discovered the concept of neuroplasticity -- evidence that our brains can be rewired and adjusted.
The concept of neuroplasticity has implications for education and for potential treatments for neurological disorders. Intense study of a subject, at any age, can change the area of the brain associated with the subject, as demonstrated in the way the hippocampus of London cab drivers enlarges during their training (the hippocampus is the area of the brain associated with navigation) [source: BBC]. And no longer does having a stroke mean irreversible brain loss; recent efforts indicate that the structure of the brain can adjust to compensate for lost function.
Researchers have investigated how a lack of sight causes other areas of the brain to change themselves.
Image Credit: Michael Hitoshi/Digital Vision/Getty Images
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