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08 January

In his famous 1944 painting Dream Caused by the Flight of a Bee Around a Pomegranate, the Spanish artist Salvador Dalí depicted a vision he imagined his wife dreamed moments before awakening from a nap.

14 October 2015

Every brain has a different internal life. Each its own unique story.

That story is the story of you—who you are and who you will become, says neuroscientist David Eagleman. In his new book The Brain, he looks at this universe inside your head from the beginning to the end, and discusses how this small organ generates "you" and the reality around you.

The Brain is a companion book to a PBS series of the same name, which premieres tonight. Opening with fundamental questions, such as "what is reality?" or "who am I?" Eagleman takes viewers and readers on a fascinating introductory journey focused on the brain. But that shouldn't be a turn-off for the initiated; the ride contains enough depth to keep neuroscientists as engaged.

The brain itself takes a journey throughout one's life, enduring a constant shape shifting that occurs as we grow and as life experiences build up. We are "born unfinished," Eagleman says. Infants have many unconnected neurons that go on to form two million connections every second as the newborn brain grows, doubling its initial size in just the first few months. Infants also have many wrongly connected neurons in dire need of pruning. "You become who you are not because of what grows in your brain, but because of what is removed," Eagleman writes.

Although the radical shape shifting eventually slows down, the brain remains plastic, changes with every new experience, shapes who we become, and sometimes even reflects who we are. This concept is manifested most famously in the case of London cabbies whose memorization of streets and paths is reflected in their enlarged hippocampus, the brain structure crucial for memory formation. Many other professions and skills, too, are found to leave their particular imprint on our brains.

But biology still has a say— in the most dramatic cases, brain damage or a tumor could fundamentally change a person. Just like what's believed to have happened to Charles Whitman, who, to the surprise of anyone who knew him, turned into a violent mass murderer in 1966. He later was found to have a tumor compressing his amygdala, a brain structure involved in emotional processing.

The brain not only determines who you are, but also what the world around you looks like. Our internal perception of the outside world is hardly a precisely mirrored image. Instead, what we perceive is composed of a sampling of the world, with the brain filling in the gaps using built-in mechanisms. How closely our version of reality matches the outside world is at the mercy of the brain, which itself has no direct access to the outside. "Sealed within the dark, silent chamber of your skull, your brain has never directly experienced the external world, and it never will," Eagleman writes. So what is reality? It's whatever simulation your brain makes. Examples of visual illusions and Eagleman's own space-bending and time-warping experiments bring this point home.


But as black-boxed and isolated our brains are, they can't be left alone. One chapter (and episode) titled "Why Do I Need You?" discusses the social brain and how we interact with others. To understand how important social interaction is for the brain to function normally, one just needs to look at extreme cases of isolation, such as solitary confinement for extended periods. Eagleman also discusses the field of social neuroscience, examining everything from how we read others' emotional states to how we treat members of an outside group and how such a highly social species can also commit horrendous anti-social acts such as genocide.

Our brains are fascinating just the way they are, but that doesn't mean technology won't provide an upgrade. Eagleman discusses his own vision of the future, one in which the internet is streamed directly into our bodies and we enjoy our new additional senses of the weather and stock market trends. Although this sounds like science fiction, Eagleman argues it's based on the reality of how the brain works. If you feed it data, it uses its special talent for extracting patterns, and you end up with a whole new sensory modality. And our bodies, too, could be augmented—the idea is a natural extrapolation from mind-controlled robotic arms and other brain-computer technology that already exists.

To join Eagleman in exploring the wonders and mysteries of the brain, get The Brain: The Story of You (Pantheon Books), available on Amazon and Barnes & Noble or watch the series debuting tonight Wednesday Oct. 14 at 10 p.m. ET (9 p.m. Central) on PBS.

Odd Brains
07 October 2015

Modern neuroscience evolved over the centuries as physicians learned about the brain from horrific head injuries, vexing diseases, and congenital abnormalities.

In The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness, and Recovery (Little, Brown and Company), Sam Kean, an award-winning science writer based in Washington, D.C., explores the serendipitous history of brain research. Until the past few decades, neuroscientists waited for brain damages to strike patients and then assessed how the patient's function was affected. Dueling Neurosurgeons is filled with cases of dreadful wounds, strokes, seizures, genetic anomalies, and bungled operations, as well as seemingly miraculous survivals and incredible resilience.

The book's title comes from the 1559 case that brought the two most prominent physicians in Europe—Andreas Vesalius and Ambroise Paré —to the bedside of French King Henri II. The king had suffered a serious head injury in an ill-considered jousting match and, despite the efforts of these celebrated surgeons, the king expired. But the doctors emerged from this hopeless case with a new understanding of brain injury: a blow to the head may cause severe damage even when there is no gruesome external wound.

Kean vividly demonstrates how doctors have followed in the footsteps of Vesalius and Paré to continue to learn about the brain from the plight of ill or wounded people whose struggles and resilience created the foundation of neuroscience today. He talked about his book by telephone from his office in Washington, D.C.

Robin Lindley: How did you come to write this book on the brain in history?

Sam Kean: Actually, I read a few of the stories in the book and I didn't believe them. I thought they sounded like baloney actually. In particular, I was thinking of stories of people who suddenly lost the ability to recognize only animal or plants. That just seemed so strangely specific to me—that you could lose that ability but not anything else. I just couldn't believe it. Also, the stories of people who lost the ability to speak but could still sing just fine. I thought there's no way this could possibly be true. But I looked into them, and not only did I realize the stories were true, but that they provide insight on how the brain is organized, how it evolved, and how it works.

So I was thinking about these stories one day and I thought I could do a whole history of the brain based on stories like that and that would be a fun to book to write. That's how it came about.

You also note that you had issues with a neurological problem—a form of sleep paralysis. Did that also motivate the book?

Yes. That taught me that there was a lot of power in this approach. As I explain in the book, sleep paralysis is kind of the opposite of sleep walking. With sleep walking, your body is awake but your mind is asleep. In sleep paralysis, your mind is awake but your body is asleep—you can't move your body or do anything.

I found that the cause of sleep paralysis was based on some fairly simple, basic brain chemistry. When you are dreaming, a part of your brainstem sends signals through your neurons to your spinal cord that temporarily paralyze muscles so that you're not taking swings at dream monsters or trying to run away. It's a benefit to be partly paralyzed in your sleep.

Sleep paralysis arises when your body forgets to turn off the spigot on these chemicals that make you paralyzed and your body remains paralyzed and you can't move. What I found interesting was you can start with something simple like neurons and chemicals and you can jump up to some high-level processes like sleeping and dreaming.

And your problems with sleep paralysis resolved?

Yes. If people experience sleep paralysis, they usually encounter it when sleeping on their backs. For me, that's especially the case. When I'm on my back, it's not that uncommon, so I have to make sure that I'm never on my back.

History is story—and you talk about developments in neuroscience through stories. You mention the power of story in dealing with complex scientific information. Can you talk about your use of story?

Yes. I think stories are important when talking about any kind of communication, but especially when talking about science for a few reasons. One, I think that stories are the way the human brain best absorbs information. If you give people a table of fact-based numbers or if you tell them a story about what the numbers mean, they're going to remember the story much better. That's not to say that facts aren't important. They are important, but the default way the human brain works is that we remember information best if presented in a story form, and it's less intimidating for people when they learn science through character—people they can relate to who struggle with issues. Just the fact that human beings are involved makes it easier for people to get interested.

And I think stories play an especially important role in neuroscience, maybe more than any other scientific field, because when you talk about the way the brain works, you're talking about emotion, about our interactions with loved ones, our memory, our language, our ability to express ourselves, our personality. All of these things spring from our brain. They are the stories we tell about our own lives so that, when getting into the brain, you naturally get into the elements that make up stories. There's a natural connection between neuroscience and stories even more than in any other scientific field.

The book opens with the powerful story of King Henri II of France who suffered a head wound when jousting in 1559.

Because he was a king, when he was injured in a jousting match, they called in the two best neurosurgeons in Europe—Andreas Vesalius and Ambroise Paré —to try to save him. They were rivals—that's the dueling neurosurgeons aspect—but they banded together here.

This story is interesting for several reasons. One, they diagnosed King Henri with a concussion, which was a controversial diagnosis then because not many people knew about them. And not many people believed in concussions because usually the outside of the skull is intact and people thought that, if the skull is okay, the brain inside must be fine. As if you have an egg and the shell is intact, then the yolk inside must be fine. But [Vesalius and Paré] reasoned that the brain was damaged.

That's interesting because we're still dealing with that same issue now. Four hundred and fifty years later you still hear about football and hockey players who suffer concussions but, because there's no gory wound outside, they go back on the field. We're still learning this historical lesson today.

The story also shows the genesis of neuroscience [with] the first significant autopsy in medical history. There were autopsies before, of course, but they were usually on criminals to punish the person. They'd be sentenced to be hanged and the body dissected afterwards.

In this case, it's not clear why the queen permitted an autopsy on Henri's body because it was clear what killed him and he obviously not a criminal. But it's important that the surgeons did because they were able to check their assumptions and learn about the brain. It's also important because what happened to the king set the standard for medical practice for other people. The king had an autopsy and that made it okay for autopsies for others, and the idea spread after that.

And this case also resonates now with thousands of troops who suffered traumatic brain injury in the wars in Iraq and Afghanistan.

Again, it's that same lesson. Just because there's not something obviously wrong with the outside of the head people don't get the treatment they need or other people don't believe they have anything wrong with them because you don't see blood or any obvious wound, although there is underlying brain damage.

It's surprising that traumatic brain injury wasn't studied earlier. It must have been an overwhelming issue a century ago in the massive industrialized cataclysm of World War I and in the wars since then.

Wars have been critical to all of medicine, and neuroscience is a good example of that. You learn about phantom limbs from the Civil War. Injuries in the Russo-Japanese war in the early 1900s gave insight on how vision works. In World War I, soldiers were hit in the head and face, and reconstruction of the face affects one's psychology. When you see your face in the mirror, it affects who you think you are, your sense of self.

You tell the story of Silas Mitchell who studied phantom limb syndrome—the phenomenon of feeling sensation in a limb that no longer exists—in the Civil War and after. What did he discover?

Silas Weir Mitchell was an American physician working in Philadelphia during the Civil War. He did some of the first extensive clinical studies on phantom limbs. Before that, we knew about phantom limbs. There are references to phantoms limbs in Moby Dick and Charles Darwin's grandfather Erasmus Darwin investigated phantom limbs. But they were very rare because amputations were much less common before the Civil War.

The Civil War introduced a new soft-lead bullet that you could load quickly into a gun and you could fire more often. It caused many shattered bones and limbs, so you saw more people with amputation. Mitchell, because he worked in a military hospital, ended up seeing enough of these patients to do credible studies and destigmatize them. Most people who lose an arm or leg experience phantom limb of some sort, and it doesn't mean they're crazy or losing their minds. It's a natural phenomenon and the outcome of how the brain and nervous system work. The brain expects this feeling from our body, and there's nothing unusual about this effect.

I was surprised that even some people born without a limb or limbs will also experience phantom limb.

That was fascinating to me too. The story I remember is about a girl who was born without forearms, so she wasn't feeling phantoms as a memory that was stirring to life. In school, she could feel her phantom fingers, and she would do arithmetic on her phantom fingertips. That story blew my mind, but it teaches you that the brain expects to find four full limbs. That's the default setting of the brain and that's how it interacts with the body—even though with this girl, the brain could see she had no forearms. But that hardwired scaffold is so inbuilt and fundamental to the brain that it overrides visual information and gives the sensation of having a full limb.

Early in the book, you focus on Charles Guiteau, a mentally ill man who assassinated President James Garfield in 1881. This case signaled another development in neuroscience with the examination of Guiteau's brain after his execution.

I think that any modern observer would look back on that case and say that Guiteau was clearly was out of his mind. There was nothing sane about the man. It's almost entertaining to read the trial transcripts when he jumped up to sing "John Brown's Body" and gave impromptu speeches comparing himself to Cicero and Napoleon. He was selling glamour shots out of his cell.

He was clearly insane but because of the hatred for him because he killed the president, there was no chance he would escape the death penalty. It was really the first time that the North and South were reunited since the Civil War in mourning for James Garfield. They brought in a few psychiatrists. One in particular said Guiteau was clearly insane and the fact that he said God ordered him to do this was further evidence that he had lost his mind and we could not hang him. But the jury decided to convict him and sentence him to death.

And physicians decided to examine Guiteau's brain. On a gross level there were a few things that weren't completely normal, but for the most part the brain appeared to be fairly normal. But when they looked at his cells, they realized something drastic had happened to his brain. Most people at the time would not have believed that because, for a person to be truly insane, you had to have some obvious sign of brain injury, [which] goes back to King Henri II where you had to see something obviously wrong. But scientists said no—we can look at the cell and see if something is wrong. Again, it's jumping up from the level of neurons and neurotransmitters to big questions about how the brain works—with issues like insanity.

You include several stories about brain damage and memory. What are a few things historians should know about memory?

One thing that jumps out is how malleable memories are—how they can change over time or be distorted so you need to be circumspect and careful about what you believe. Everyone knows, on some level, that people misremember things or that people sometimes get facts wrong, but I don't think we appreciate how common that is, how memories get distorted all of the time, even as a matter of course. It's just something that human brains do. It's not even a lapse. People do it—maybe not consciously— perhaps because they want to save face or suppress a traumatic memory.

Especially with firsthand recollections that are long removed, you can't say that everything a person says is totally wrong, but you have to be circumspect about those things. It's important to realize that memory by its nature can be changed rather easily.

And your stories about how memory works are illuminating. For example, the unusual memory loss of the English musician Clive Wearing.

Clive Wearing had a brain infection from the herpes virus—not the STD, but a related virus that causes cold sores. Once in a while, these viruses migrate up the nose, along the olfactory or smell nerves and into the brain. Once they're inside the brain, they tend to wreak a lot of havoc. In Clive's case, they destroyed his hippocampuses, the parts of the brain very involved in forming historic memory. The result was that he woke up with amnesia and, in fact, the most profound amnesia that doctors had ever seen.

Some stories that stood out for me. He'd be playing solitaire and he would turn his head and then look back at the cards and the cards would seem to have rearranged themselves on the table. Or he might blink and the color of somebody's shirt would seem to have changed before his eyes.

His short-term memory could not last from the beginning of a blink to the end of a blink. That's how fleeting his short-term memory was. That's unusual because most amnesiacs retain some short-term memory. Their memories may fade very quickly in seconds or minutes, but not as quickly as Clive's memory faded. He lost his short-term memory and his long-term memory—and that's why doctors described him as the most profound amnesiac that they've ever known.

But he retained memory for writing and some other tasks.

Yes, he retained a few types of memory. He retained motor memory of the ability to do physical things. The classic example is riding a bicycle. You don't forget the ability to ride a bicycle because of motor memory. Other motor memories include the ability to write. He could still write and still play the piano because moving your hands on a piano is a motor memory. There were abilities he retained depending on which memory system in the brain was being engaged. His long-term and short-term memory were gone, but his muscle memory, a different type of memory, remained intact.

I was intrigued also by the case of KC who suffered brain trauma in a 1981 motorcycle accident. After that he could recall trivia but could not remember personal episodes in his life. Why was that?

This case provided further insight into the fact that we have different memory systems within the brain. His case showed two types of memory. He retained semantic memory of names, dates, facts and those things. A way to think of semantic memory is basically the things you could look up in a reference book. But he lacked personal memory, memories like when he was excited by a birthday gift or what it felt like to be attracted to someone or to be lonely. He lost all of those memories, which were completely wiped from his mind.

This shows that we have different memory systems. One is dedicated to bare information or facts devoid of emotion and context, and the other system involves very personal things about our lives.

What did you learn about brain function to explain the unusual situations that you first thought were apocryphal such as losing the ability to speak yet retaining the ability to sing, and losing the ability to recognize animals but retaining the ability to recognize plants?

People can lose the ability to speak but not sing when connections between the language nodes and the motor parts of the brain that control the mouth go down. In that case, both the language centers themselves and the mouth still work fine, but they can't communicate with each other, and speak falters as a result. But, the brain contains numerous back alleys and alternative pathways to send information around. So if the direct connection is broken but the alternative pathway is still intact, people might still be able to sing because the language centers can still activate the mouth by routing information through, say, the musical centers of the brain.

As for the animal recognition, we seem to have various circuits in our brain that each specialize in recognizing a certain class of things like animals, plants, faces, etc. Those circuits give us a big advantage in some sense. But those circuits can also be damaged and go down, and when they do, the ability to recognize that entire class of things can evaporate from the mind. That seems to be what happens when people lose the ability to recognize animals, but not other classes of things.

You also consider the vexing question of consciousness. The neurosurgeon Wilder Penfield was fascinated by consciousness and he explored it by studying epilepsy, "the sacred disease," and mapping the brain.

Epilepsy is a disease that seemed very mysterious, but once researchers got a handle on it, it provided good insights on how the brain worked.

Penfield was a neurosurgeon who was interested in consciousness. Often, when he opened the brain and tried to figure out what part of the brain he needed to remove to cure a person of epilepsy, he would take a small electrode and stimulate the surface of the brain to see what happened. A person might make a noise or speak or kick, but once in a while a person would have a very strong, vivid memory, and that interested him because he was [seeking] the seat of consciousness in humans.

In the book, I talk about cases like Dostoyevsky and what we can learn about people who suffer from epilepsy, especially those who suffer temporal lobe epilepsy, which is often associated with people seeing visions or having supernatural feelings. They might see flashes of light or hear an angelic chorus singing. Dostoyevsky saw and felt these kinds of things, and you can see that in his writing. He had characters with epilepsy or other neurological syndromes, and people experiencing world shattering moments in the way Dostoyevsky did. He's a very typical case of temporal epilepsy.

And both Dostoyevsky and Penfield were very religious. Dostoyevsky because he was feeling these direct contacts with God and Penfield just happened to be religious by upbringing and emotional outlook on life. Penfield used his work to further his ideas about where the soul is in the brain and the spiritual aspects of his own life. Not a lot of neurosurgeons nowadays agree with the conclusions he drew, but everyone acknowledges that he did some amazing work in exploring how the brain works and figuring out certain aspects of consciousness.

Neuroscientists are still involved in mapping the brain and considering whether we have a unified brain or whether brain functions are localized.

Yes. Historically, it goes back and forth between the view that the whole brain together gives rise to language and memory. Others say no, the brain is a collection of individualized, specialized organs. And that debate continues today.

It's intriguing that many of the physicians and scientists you profile were as quirky or damaged as their patients. I had thought of Harvey Cushing as great brain surgeon and researcher, but I learned from your book that he also had an explosive temper. Did the eccentricities of the doctors also strike you?

Yes. When you get into the lives of the physicians, many were flawed. If you looked into anyone's life, you would find flaws, but with great scientists maybe we have the expectation that they were also great human beings. But there's no necessary connection between being a great scientist and being a good person. Or, in the case of someone like Harvey Cushing, his flaws may have made him great: his temper, his ruthlessness, his obsession. Those things didn't make him easy to get along with, but they drove him into new areas and pushed him to greatness. He was definitely willing to do things that would strike us as cold today. There were stories about illicit autopsies and other [activities] because he was so eager to get information on how the brain works.

You re-tell the famous story of Phineas Gage and stress his resilience while debunking the view that he became a sort of degenerate after he suffered a severe brain injury.

Phineas Gage is probably the most famous case in neuroscience and maybe the most famous case in medical history. He was a railroad worker in Vermont. A four-foot iron rod was blown through the top of his skull. The fact that he survived this injury was an absolute miracle. In fact, he walked away from the accident claiming that he never even lost consciousness, as mind blowing as it is.

He's important because his is the first well-documented case we know of where someone suffered an injury to the brain and his personality drastically changed afterward. The problem with the case though is knowing how his personality changed. His doctor in his notes makes it clear that Gage changed in some way. Unfortunately, he's ambiguous about what changes took place or when the changes took place. It's not clear if he wrote immediately after the accident or if it was long-term or if it maybe got better.

Unfortunately, as the decades passed, distortions or fabrications in the Gage story crept in. Eventually, a century after the accident, you had stories circulating about Phineas Gage turning into a drunken lout or a criminal or doing dastardly things as if this wholly virtuous person had suddenly become a lunatic and an awful person.

You have to look back in the historical record to see that there's very little evidence that such a drastic and bad transformation took place. In fact, there's some evidence that Phineas Gage might have recovered over time. He didn't become the Phineas Gage of old, but he might have recovered something like a normal life. Not many people know that he actually went to Chile for seven years and worked on his own as a stage coach driver. He took off for a foreign land and presumably learned a new language while he was there and dealt with customers. And he did this for seven years. This doesn't sound like someone with severe brain damage. Again, there's evidence that he might have gotten better, and when you look at the entirety of the Phineas Gage story it throws a new light not only on neuroscience but also on how the history of science is written.

Gage and Wearing and KC and others in your book retained abilities following serious brain injuries or illness. Indeed, many of your stories reveal stunning resilience or recovery after very severe brain damage.

That's how the book grows from beginning to end. There are a lot of tales of people getting injured because that's how neuroscience progressed and that was the only way we had of doing neuroscience for centuries. But, by the end of the book, I think there's a sense that we were not only learning about the brain through injury, but we were learning about the brain through ways that people recover from injuries and the way the brain is able to heal itself.

Plastic changes occur where brain circuits behave differently. They may route information around damage or people may develop compensation strategies where the brain can do other things that solve the problems in a different way.

So the book grows because you see injuries but you also see how the brain changes over time. More and more scientists realize what a resilient organ the brain is. These stories on the surface seem to be of injury and woe, but if you look deep down at the person's whole life, there are stories of persistence and courage in the way the brain helps itself.

Robin Lindley is the features editor for the History News Network. This article is adapted from the original piece published at History News Network. Read the full article here.

12 October 2015

Neuroscience has come a long way since about 335 BC when Aristotle surmised that the heart is the seat of mental processes. And even in the past century, since Santiago Ramon y Cajal identified the nerve cell, neuroscience has quickly evolved from a branch of biology to a multidisciplinary science that now includes disciplines such as chemistry, pharmacology, computer science, psychology, philosophy, physics, genetics and more. In the not too distant past, researchers often worked in isolation and usually studied only one area of the brain but, with new technology, scientists now can monitor the entire brain and study the components of cells and subcellular structures as well as the processes of cell communication.

History is the best way to learn about the complex field of neuroscience, says Dr. Mitchell Glickstein, an Emeritus Professor of Neuroscience at University College London, in his sweeping new book, Neuroscience – A Historical Introduction (MIT Press). "Neuroscience is a human creation. It is of value to understand how it came about," Glickstein says.

Glickstein is an expert in neuroanatomy and the history of neuroscience. His work has involved the study of the brain's processing of visual information and the role of the cerebellum in vision and the sensory guidance of movement. In his book, Glickstein carefully describes the structure and function of the brain as he explains how we've gained this knowledge. He explores the process of discovery from ancient times to the present, such as how physicians learned about brain processes by studying injuries; how scientists built on the neuroanatomical studies of nerve cells; and how experiments on the brains of other mammals and invertebrates advanced human neuroscience. Glickstein presents the history by beginning with an overview of the nervous system and nerve cells and then discussing specific topics such as electrical and chemical transmission in the nervous system; the senses; movement; memory; neurological disease; personality and emotion; mental illness; and consciousness. Glickstein responded by email from London to a series of questions on his career and his new history of neuroscience.

Robin Lindley: You're an acclaimed neuroscientist. How did you come to write a book of history on neuroscience?

Mitchell Glickstein: I have taught Neuroscience for many years. A historical approach seemed the most effective in helping students understand the field of neuroscience. The experimental and clinical foundations of the field are often easy to understand, and they make the current advanced textbooks more accessible.

Rather than a strictly chronological history, you present the history in terms of structure, function and pathology. How did you decide on this approach?

There seems to me to be two historical approaches to teaching the history of neuroscience. What did we know in 1850? What did we know in 1860, etc.? Alternatively, the way I structured the book seemed preferable to me. Each scientist or clinician was most influenced by the previous ones within their field. The history may contain great gaps. In 1892 Cajal described in exquisite detail the structure of the vertebrate retina. It was a hundred years before physiologists had the methods with which they could begin to interpret the anatomical structure.

Who do you consider the earliest neuroscientist in history?

Neuroscience as a discipline emerged as a combination of anatomy, physiology and pharmacology after the Second World War. But its roots go much deeper. In my book I show an Assyrian sculpture from the British Museum of about 600 B.C. A lioness is shown with a spear cutting across her spine. The hind paws are obviously paralyzed; the front paws are not. The sculptor was not a neuroscientist, but was a careful observer.

What traits do you think the greatest neuroscientists share?

As a model, I think of other areas of biology; best is Charles Darwin. He combined years of careful study of animals and plants culminating in a profound insight. With Darwin as the standard, the great neuroscientists share these traits to a greater or lesser extent; perhaps a few hundred milli-darwins.

There are some persistent myths about the brain including the idea that we use only ten percent of our brain capacity. What's the reality that neuroscience has revealed?

A myth indeed. Some of it comes from the remarkable functional recovery people may make after brain injury. The brain does not re-grow, but lost function may return. This plasticity is most striking in children. A small child who loses an entire left hemisphere, may yet develop normal speech.

There are other myths. Neuroscientists often solemnly stated or wrote that the cerebellum is not necessary for normal movement because people may be born without a cerebellum, develop normally, and are discovered only at autopsy to lack a cerebellum. Also a myth.

What is neuroplasticity and how did scientists learn about this remarkable brain process?

Neuroplasticity is a general concept relating to the fact that the brain is organized to learn. Plasticity refers to the mechanism of what happens at a cellular level in the brain that is associated with learning.

It seems brain function is often discovered as the result of brain trauma. There's the famous frontal lobe injury suffered by Phineas Gage in the nineteenth century that led to better understanding of the brain's role in memory and personality, and you describe Dr. Tatsuji Inouye's study of bullet wounds to the brain during the Russo-Japanese War to determine visual loss. What are some examples of important discoveries about the brain from injury that impressed you?

There are many. The early Greek physicians, for example, knew that a head injury may result in loss of function on the opposite side of the body. My book has other examples. For example a patient with unquenchable thirst after head injury, and a woman without fear with the absence of a particular brain region.

You've said that Santiago Ramon y Cajal may be the most important neuroscientist in history. What did he do and why is his work so significant?

Camillo Golgi had discovered the silver based staining method that is named for him. Cajal used the method to describe in remarkable detail the cellular structure of the brain and spinal cord. His textbook, published over a hundred years ago, first in Spanish, then in French and lately in English remains the standard for detailed description of neural structure. He coupled this work with a deep intuition about how nerve cells connected to one another.

Was Cajal's work the foundation for the discovery of neurotransmitters?

Not directly. Cajal argued forcibly that neurons may touch one another, but that they do not fuse. He thus raised the question of how they communicated. It was progress in the pharmacology of the autonomic nervous system that led to modern understanding of the role of transmitters in linking neurons to one another and to muscles.

You were a colleague of Roger Sperry, a Nobel Prize-winning neuroscientist who is famous for his split-brain experiments. What did his research show and why are his findings so important for neuroscience today?

Before the work in Sperry's lab there was no evidence that memory could be localized to a particular region of the brain. Ronald Myers, working with Roger Sperry in the 1950s, showed that a memory trace can be formed in one side of the brain, and remain inaccessible to the other. Based on these discoveries, Mike Gazzaniga, also working with Sperry, explored the independent capacity of each human cerebral hemisphere.

You are an expert on vision and movement. How does the brain process visual images and how did we learn this?

By the beginning of the nineteenth century the location of the primary visual area in the human brain was established. The next phase in understanding were due to clinical studies by physicians like Tatsuji Inouye and Gordon Holmes who studied blindness within the visual field caused by brain injury. Experimental study of the response of single neurons in the primary visual cortex, especially that of David Hubel and Torsten Wiesel, began to uncover the cellular basis of visual processing in the primary visual cortex. But there are vast areas in the parietal and temporal lobes that are involved in further processing of vision. Semir Zeki was a pioneer in showing the number of these visual areas, and the nature of the responses of the cells within them.

What are a few things neuroscientists are learning now that may be helpful in addressing diseases such as dementia and mental illness?

I believe that the next generation will see major advances in the understanding and then the treatment of neurological and psychiatric diseases at a cellular and molecular level. There are insights from the study of patients that one small mutation in one gene can lead to a devastating neurological disease. Understanding at that level may help to suggest mechanisms for treatment.

Who are your inspirations as a neuroscientist and a historian?

I remain an avid consumer of popular history in books and TV. Most influential for me in the history of science are former colleagues. Harry Patton was chairman of the Physiology Department at the University of Washington. His lectures to the medical students were inspirational for me. He didn't teach simple textbook physiology. He taught not just what we know, but how we know it. What were the clinical and scientific studies that led to our current understanding of brain function?

There's a sense that we've learned more about the brain in the past two or three decades than in all the previous centuries. What's your sense of the arc of where neuroscience has been and where it's headed?

Neuroscience has gone from a study of structure of the brain and spinal cord and the nature and connections of the cells within it. The next major advances will be at the molecular level; understanding the molecular basis of disease, and suggesting routes for dealing with them.

Is there anything you'd like to add for readers about neuroscience and history or anything else?

Neuroscience is a fascinating branch of biology dealing with the nature of human sensation, movement and thought. But we are far from understanding it all. Now, as in the past, some will claim more authority that they may not deserve. It is important to distinguish established facts and principles from those that are more speculative.

Robin Lindley is the features editor for the History News Network. This article is adapted from the original piece published at History News Network. Read the full article here.