Posted by: R. Douglas Fields | March 17, 2015

Big Brains/Little Brain: Whale Brains Provide Clues to Cognition

The cerebellum of whales suggest its role in higher level cognition.  Photo by the author

The cerebellum of whales suggest its role in higher level cognition. Photo by the author

A fascinating report on NPR by science correspondent Jonathan Hamilton yesterday (March 16, 2015) tells the story of Jonathan Keleher, a rare individual born with a major portion of his brain missing: the cerebellum. The name in Latin means “little brain,” because the cerebellum sits separately from the rest of the brain looking something like a woman’s hair bun. Neuroscientists have long understood that the cerebellum is important for controlling bodily movements, by making them more fluid and coordinated, but researchers have also long appreciated that cerebellum does much more. Exactly what these other functions are, have always been a bit mysterious. It is difficult to pinpoint the more hidden functions of the cerebellum, because some of them seem not to involve straight-forward actions that can be easily observed, for example controlling breathing or vision. But this suggests that the little brain is doing something far more complex and interesting.

Whale brains provide interesting insight into the possible functions of the cerebellum beyond its important role in regulating movement. A comparison of cetacean brains supports the growing body of research indicating that the cerebellum contributes to higher level cognitive function. A study by Sam Ridgway and Alicia Hanson compares the brains of two animals with the largest brains on earth: sperm whales and killer whales. (Pause for a minute and consider that last sentence. Having done some anatomical studies on whales as a graduate student, I can say that doing neuroanatomy on an animal that can reach 60 feet in length and 60 tons in weight, is not easy. This is not a job for a scalpel. Electric saws, chisels, and hatchets are the surgical instruments required.) Killer whales are well known from marine aquarium shows, and sperm whales are the enormous beasts harpooned in Herman Melville’s tale of Captain Ahab’s quest. What this study found is that the animal with the biggest brain on the planet (sperm whale) has a smaller cerebellum (proportionately) than a killer whale. In fact, in proportion to the size of the cerebrum, sperm whales have the smallest cerebellum of any mammal on land or sea. Why?

Both killer whales and sperm whales swim in the same way, by undulating their enormous tail (flukes). Both of these whales echolocate. They both have long gestational periods and live long lives. They are closely related animals evolutionarily; both being members of the toothed whales (odontocete). The mass of the killer whale’s cerebellum is 13.7% of its entire brain mass, but the cerebellum of sperm whales is only 7% of its brain mass.

Killer whales are much different from sperm whales in their behavior. Killer whales are the ocean’s top predator, working in organized groups to hunt down a large variety of different fish, birds, and marine mammals, whereas sperm whales graze in the deep ocean on primarily one food source: giant squid and some fish. The authors conclude that the group coordination during hunting by killer whales on a variety of elusive prey requires higher level cognition and creativity to outfox their prey, to communicate and cooperate with other members of their group. This could explain why they have a larger cerebellum proportionately than sperm whales.

The researchers cite other evidence in support of the function of the cerebellum in higher level cognition. The cerebellum increases in size going up the evolutionary tree from monkeys to great apes. Increased cerebellar size is also seen in hominoid evolution. Fossils show that early hominids had a relatively small cerebellum.

Mr. Kehler’s remarkable brain is giving similar insights into the function of this poorly understood part of the brain, but also more. His inspirational story shows how adaptable the human brain can be in some people who are fiercely determined to develop their abilities to the highest level possible.

Hamilton, J (2014) A man’s incomplete brain reveals cerebellum’s role in thought and emotion. NPR, March 16, 2015

Ridgway, S.H. and Hanson, A.C. (2013) Sperm whales and killer whales with the largest brains of all toothed whales show extreme differences in cerebellum. Brain Behavior and Evolution, 83;266-274.

Posted by: R. Douglas Fields | February 5, 2015

Brian Williams ‘False Memory’–a Neuroscience Perspective

Brian WilliamsNBC News anchor Brian Williams apologized for his erroneous account of being aboard a helicopter forced to make an emergency landing after being hit by enemy fire while reporting on the Iraq war in 2003. Williams blames the fallibility of human recall for the error. How can the neuroscience of memory (and false memory) provide insight?

“I would not have chosen to make this mistake,” Williams told the Washington Post. “I don’t know what screwed up in my mind that caused me to conflate one aircraft with another.”

Williams’ bewilderment is perhaps understandable. We all know that memory is fallible. Eye witness testimony has been shown often to be false, even though the witness firmly believes his or her account of what they personally experienced. Rapists sent to prison on the basis of a victim identifying the attacker without any doubt, have been found to be innocent through DNA evidence years later.

“I spent much of the weekend thinking I’d gone crazy, Williams says in the Washington Post article. “I feel terrible about making this mistake.” This is the same remorse and disbelief that shakes the victim of a rape who is forced by facts to accept that her memory was false.

To understand false memories one must first understand what a memory is and what it is not in terms of brain function. Memory is not a recording. A recording of our day-to-day experiences would be worse than useless; it would be counterproductive. Memories are fabrications, and they have to be.

“That hole [in the helicopter] was made by a rocket-grenade, or RPG. It punched cleanly through the skin of the ship, but amazingly it didn’t detonate.” This account by Williams we now know is entirely false, but consider for a moment the following. What if this picture of the helicopter with a hole pierced through it was indeed a snapshot of a true experience embossed in the mind’s ‘memory bank.” Even if it were accurate, this picture is not a memory. This picture would be much like a single frame snipped out of a movie reel. Without context, sequence, and significance in relation to other experiences, there is no memory of what had transpired.

Consider all the various sights, sounds, tastes, smells, emotions, that must be combined together to form a coherent memory, and assembled in the proper temporal sequence and in meaningful relationships between these new experience and past experiences that are essential to form a coherent memory. These multiple sensory inputs and the other aspects of mental processing required to associate emotions and other events with the new experience, must somehow tie together multiple mental functions taking place all over the brain into one scene, which we call a memory. Memory researchers call this a schema. How this assembly is accomplished is still poorly understood, but this stitching together of a mental scene is the essence of what a memory is.

One of the brain’s remarkable abilities is that it can fill in missing information to connect the dots and form a coherent memory. We can recognize a specific individual from a skilled cartoonist’s squiggly line. This mental filling in is where false memories can begin to form.

Secondly, a memory needs to be continually updated. Of what use is an outdated image of a person in our memory in recognizing that individual now or in the future? Even a picture of a loved one from years ago surprises us because we have completely forgotten that they once looked that way. That memory has been erased. We constantly update memories according to new information, and much of this happens while we sleep. Memories are not recordings; they are fabrications.

Can Williams’ false report be understood in the context of a false memory? Consider that Williams is a reporter. His function and purpose while on the scene in Iraq was to record facts and to do so accurately. There is no opportunity for false memory in this situation. Just as a scientist would never falsify data, because doing so would completely undermine their objective, neither would a reporter. Researchers do sometimes fudge data, but scientists do not. Likewise, there is not and cannot be any false memory in the mind of a reporter.

Paul Farhi February 4, 2015. Brian Williams admits that his story of coming under fire while in Iraq was false. The Washington Post

Posted by: R. Douglas Fields | January 27, 2015

Synapse Poisons in Croc Bile Beer the Likely Killer in Mozambique

aleOn January 11, 2015 news swept the globe reporting that scores of people died and 200 were sickened by drinking beer poisoned with crocodile bile in Mozambique. Thinking is now shifting to the possibility of poisoned synapses, not reptilian bile as the cause of these deaths.

A horribly tragic incident occurred at a funeral on January 9, 2015 in Mozambique, when people who had come to pay their last respects suffered poisoning from consuming the traditional home-made beer that was served. The mass fatalities of over 70 people devastated families, leaving many children orphans overnight. The toxic substance in the beer is still not known, but the media frenzy is astonishing. Is crocodile bile a deadly poison? How much bile can a person drink anyway? What is it in croc bile that could be so potent, trace amounts too weak to taste could kill and sicken hundreds of people?

Science writer for Forbes, David Kroll, traced the story back to the source. What he found was rumor and superstition, and what is more important, a likely cause of all this death. I refer you to his article for the details of his investigation and the suspicion that croc bile was not likely the poison in this brew.

The cause of these deaths is not yet known, but if it wasn’t croc bile that killed the beer drinkers, let’s have a look at the alternatives being suggested–all of them are related to nervous system function, and along the way delve a bit into the science of homebrew.

Not what made Milwaukee famous

The beverage brewed in Mozambique is a far cry from the Bud Light that most Americans associate with beer. Called pombe, the brew is a mixture of corn, bran, sorghum, and sugar, fermented with a different species of yeast (Schizosaccharomyces pombe) from the Saccharomyces cerevisiae used for making beer and wine. Beer as we know it is made from malted barley and hops. The fermented drink in Mozambique appears to somewhat resemble the corn-based traditional beverage, called chicha, which has been made in South America for centuries.

Professor Javier Carvajal Barriga, a microbiologist at Pontificia Universidad Católica del Ecuador in Quito, Ecuador, has resurrected yeasts from ancient fermentation vessels and other sources all over the world, including fermentation pottery from a pre-Incan tomb. From a fermentation vessel dating from 650 AD, Professor Carvajal Barriga resurrected dormant yeast and discovered an entirely new species, which he named Candida theae. This discovery also provided clues to how the ancient brew was made. Human spit was used to break down the corn starch into sugar that yeast can ferment into alcohol. (Saliva contains the starch digesting enzyme, amylase). His microbiological research also supported what conquistadores recorded about the traditional chicha recipe: that human feces were added to start the pot fermenting.

This is not how beer is made today. Malted barley is used, making spit unnecessary. Malting is a process whereby the grain is moistened and allowed to start sprouting. When a seed sprouts it generates enzymes to break down the starch to sugar, which is the energy store that will feed the sprouting plant. Beer makers hijack Nature’s intentions by roasting the freshly sprouted barley to stop the germination process right after the enzyme is made. Then the brewer adds water to make a porridge that must be held at a precise sequence of temperature steps to coax the enzymes to make sugar from the starch. Yeast can then convert the sugar to alcohol and carbon dioxide. How early humans figured this all out is baffling, but no less amazing than the ingenuity used to make chicha.

So I when I heard of this mass death in Mozambique from poison pombe, I contacted Professor Carvajal Barriga for his insights.

“I’m really surprised by this news of poisonous beer,” Carvajal Barriga says. In the middle ages they used rats, cats, a number of flowers and other elements like fungi to give magical properties to their brews. Some of those primitive beers would have been poisonous as well.”

When I visited his lab in Quito in 2012, we shared a wonderful Belgian style ale that Carvajal Barriga had brewed from yeast he resurrected from an ancient oak vat that had held the first beer brewed in America. I remember him telling me how plants or mushrooms with psychoactive properties often would be added to the ancient chicha. (He could see this, by identifying species of yeasts in the ancient fermentation vessel that are associated with these other plants.) The ancient brew masters resorted to this because the species of yeast that they had to work with is killed by relatively low alcohol concentrations. So, unable to achieve the alcohol content of the beer we enjoy today, (outside the state of Utah), the bier meisters would toss in other substances to give the brew more of a kick.

“The poisoning in Mozambique may be due to chemicals added to the beer via flowers or even microtoxins produced by molds living on cereals,” he suggests.

This is the same theory considered by Kroll in his Forbes article; specifically, the possibility that the foxglove plant might have been added to the Mozambique brew. Foxglove is the source of digitalis, a drug used for regulating heartbeat. The plant compound acts on the vagus nerve, part of the parasympathetic nervous system regulating heartbeat, and also acts directly on cardiac muscle, by changing the concentration of sodium ions inside these nervous system cells. The cellular voltage produced by neurons and muscle cells results from an imbalance in charged ions across the cell membrane–just as voltage is produced in a battery. Digitalis inhibits a membrane pump (sodium-potassium ATPase) that pushes sodium ions out of the cell and sucks potassium ions into the cell. When the pump is impaired by digitalis, sodium ions seep back in and the cellular voltage drops. This has a number of consequences, most importantly, changing the amount of calcium ions inside the cell. Calcium ions control many vital cellular processes, including the firing of synapses (i.e., release of neurotransmitter).

Poisoning synapses

Mass deaths at social gatherings often result from food poisoning, frequently caused by clostridial toxins made by bacteria found naturally in the soil, for example botulinum toxin. Botulinum toxin is one of the most deadly toxins known to man. The reason for this is that this toxin attacks the fundamental mechanism of communication in the brain–synaptic transmission.

When a nerve impulse reaches a nerve terminal, voltage-sensitive channels in the neuronal membrane open briefly and admit a spurt of calcium ions. These ions activate a protein called synaptotagmin, which is part of a complex machinery of molecules that tether synaptic vesicles next to the cell membrane of the nerve terminal. Synaptic vesicles are like submicroscopic “water balloons” filled with neurotransmitters, small molecules of various types that carry messages between neurons. When stimulated by an electrical impulse, this molecular machinery causes the synaptic vesicles to fuse to the cell membrane and rapidly dump its contents out of the neuron to stimulate receptors on the next neuron in the circuit.

Botulinum toxin (and tetanus toxin), cut the synaptic vesicle release proteins, thereby blocking synaptic transmission. (Either the synaptic proteins synaptobrevin, SNAP-25, or syntaxin can be attacked, depending on the specific type of Botulinum toxin.) The consequences of cutting communication lines in the nervous system are catastrophic, and food poisoning from clostricial toxins can kill quickly.

But beer is not often a source of food poisoning. This is because the process of brewing beer, unlike the process of making wine, requires prolonged boiling. Even a dead rat would become sterilized in the process of brewing beer. The poisoning in Mozambique most likely attacked synapses, but in a different manner.


The extraordinary potency of clostridial toxins inspired the creation of man-made neurotoxins that work in a similar way for use in warfare against other people (nerve gas) or against insects (pesticides). At this point, this explanation seems the most likely cause of the mass death among the beer drinkers in Mozambique, according to the Forbes article. The brew was concocted in large barrels. If these or other utensils used in brewing, had been recycled from drums with pesticide residue in them, even low levels of organophosphates could have proven fatal.

Organophosphate pesticides work by inhibiting neurotransmission at synapses that use the nerurotransmitter acetylcholine to communicate. This includes the synapses called neuromuscular junctions that control our muscle contractions. Once acetylcholine is released from the nerve terminal and activates the muscle, the chemical signal to contract muscles must be terminated. This is accomplished by an enzyme in the synapse (acetylcholinesterase), which rapidly breaks down acetylcholine. Organophosphate pesticides and Sarin nerve gas prevent this enzyme from working. Unable to control muscles for breathing and other essential bodily functions that are controlled by synapses using acetylcholine, the victim (bug or enemy) dies quickly and quite miserably.

This brings the Mozambique tragedy close to home. An FDA analysis determined that 49% of fruit, 29% of vegetables, and 26% of grain products produced in the United States have pesticide residue. 50% of shallow water wells have pesticide contamination at detectable levels. Children are especially vulnerable to pesticide exposure because their smaller bodies make the same amount of pesticide on one apple a much higher dose than for an adult. Also, children crawl on the floor, play in dirt and put things in their mouths, increasing their exposure to pesticides. Organophosphate pesticide levels in people living in agricultural areas are higher than in people living in urban areas, but in a large sample of children between ages 8-15 in the general population, the level of pesticide residue in urine samples correlates directly with a risk for attention deficit hyperactivity disorder (ADHD).

In a 2012 review article in the journal Pediatrics the authors conclude that organophosphate exposures that are being experience by US children in the general population may have adverse neurodeveopmental consequences. The consequences of organophosphate exposure to the fetus and young children are known to include decreased IQ, ADHD, neurodevelopmental disorders, and cancer. For example, a study of Latino farm worker families from agricultural regions showed that organophosphate levels in urine from pregnant women were associated with lower IQ in their children at 7 years of age. Finally, many veterans of the Gulf War suffered chronic illness, which appears to be related to low-level exposure to Sarin gas and organophosphate pesticides they were exposed to on the battlefield.

We can only hope that the cause of the poisoning in Mozambique can be found, and that we learn from the tragedy.

Figure Caption An ale made by infusion mash of English pale malted barley, crystal and dextrin malt, and Monteuka, Nelson Sauvin and Green Bullet hops from New Zealand and Nottingham Ale yeast.


Fields, RD (2012) Raising the Dead: New Species of Life Resurrected from Ancient Andean Tomb Scientific American on-line February, 19, 2012

Kroll, David, (2015) Did crocodile bile really kill 73 people in Mozambique. Forbes January 12, 2015

Kroll, David, (2015) Crocodile Bile Expert Suspects Toxic Pesticide In Mozambique Tainted Beer Tragedy Forbes, January 14, 2015

Roberts, JR and Karr CJ Pesticide Exposure in Children Pediatrics 130: e1765, 2012

US FDA Center for Food Safety and Applied Nutrition. Pesticide residue monitoring program

Posted by: R. Douglas Fields | January 14, 2015

Neuroscience of ‘Under the Skin,’ Starring Scarlett Johansson

UnderSkin (2)In the eerie science fiction film, Under the Skin, starring Scarlett Johansson as an alien vixen clothed in human skin, roaming the earth in search of single men for nefarious purposes, a turning point comes when she offers a hooded man on a dark road a ride in her vehicle. When the man takes off his hood we see his shockingly disfigured face. It is not make up. The disfigurement is caused by a genetic condition, neurofibromatosis, affecting actor Adam Pearson. Pearson’s brother has the same disorder, but no disfigurement. Instead he suffers memory problems. The film is a head scratcher–in the best possible way–but neurofibromatosis is not. Let’s have a look.

When Adam Pearson was a school boy he was often taunted as “Elephant Man” by bullies. In fact, one prevailing theory is that the real Elephant Man, Joseph Merrick, suffered from neurofibromatosis. A new paper by Huntley, Hodder and Ramachandran, in the journal Gene, gives a vivid account of the discovery of the Elephant Man in Victorian England, and recounts the scientific sleuthing over the last 125 years to identify the medical condition that caused Merrick to have skin and body features resembling an elephant.

Joseph Merrick was a single-case study presented to the Royal London Hospital in 1884 at the age of 21. Merrick, from Leister England, was discovered at a Freak Show by Sir Frederick Treves, Surgeon to Queen Victoria. The doctor did not routinely seek such entertainment; he went there specifically to see a man on exhibition advertised as having the features of an elephant. Treves paid a shilling to have a private viewing after hours. Sir Treves’ examination documented that Merrick had a large number of disfiguring growths all over his body that made it difficult for the man to speak, sleep or walk. Many of his bones were misshapen and his skull was grossly enlarged, and malformed. Sir Treves described Merrick as “the most disgusting specimen of humanity that I have ever seen.” (Read that with a proper British accent for full effect.)

Soon after the paper describing the case of the Elephant Man was published in 1885 in the journal Trans. Pathol. Soc. London, “A Case of Congenital Deformity,” Freak Shows in Jolly Old London were outlawed. Adding to that tragedy, Merrick was robbed of his life savings by his show manager and he ended up stranded at the Liverpool Street Station, homeless, penniless, and unable to make himself understood because of his speech impediment. The police brought him to Sir Treves, who appealed to the good-hearted public for assistance in a letter to the Times. Within one week he collected enough money to support Merrick the rest of his life at the hospital.

For the rest of the fascinating story of the real Elephant Man, and a recent determination of the medical condition that afflicted Merrick, I highly recommend this new article in the journal Gene. Spoiler alert: the authors conclude that Merrick did not have neurofibromatosis, but instead suffered from a condition called Proteus Syndrome, which is caused by a mutation in the gene PTEN.

Neurofibromatosis is a genetic disorder that causes tumors to grow in the nervous system. I actually published a small paper on neurofibromatosis from research in my lab, which is as close as I expect I will ever get to Scarlett Johansson.

In your dreams, buddy.

In your dreams, buddy.

The tumors in nerves cause disfigurement. As you would expect, they often cause a wide range of neurological problems, from hearing loss to learning impairment, depending on where the tumors grow and interrupt normal communication through nerve axons.

Neurofibromatosis 1 (NF1) causes harmless spots on the skin and tumors under the skin anywhere on the body. Bone growth is often deformed, for example by bowed lower legs or a curved spine. Mild learning disabilities are common, as well as attention-deficit/hyperactivity disorder (ADHD), but not in all cases. The head is typically larger than normal. So there are indeed several similarities to the features exhibited by the Elephant Man, but these are only superficially similar to neurofibromatosis.

Neurofibromatosis 2 (NF2) also causes nerve tumors by unregulated growth of Schwann cells, the glial cell of the peripheral nervous system. Schwann cells form the myelin sheath that is essential for rapid impulse conduction through axons in peripheral nerves. Other Schwann cells encase bundles of slender axons that conduct impulses slowly because they lack the myelin insulation. Hearing loss and balance problems are a common but the tumors can grow in many different nerves causing a wide range of symptoms.

The NF1 gene is on chromosome 17. It normally makes the protein neurofibromin, which helps regulate cell growth. NF2 is caused by the NF2 gene located on chromosome 22. This gene produces the protein merlin, which also controls cell growth.

In either case, you need to inherit only one copy of the mutant gene to get the disorder (autosomal dominant), which means that if you have neurofibromatosis there is a 50:50 probability that your offspring will inherit the disease.

“My kids are going to be genetically awesome anyway,” Pearson says displaying the spunk that has made him a successful actor in a major film. “Now that I’ve appeared nude with Scarlett, I want to be a Bond Villain,” he says. Pearson is also a supporter of the charity Changing Faces which supports people who have medical conditions or injuries that affect their appearance by helping them cope with life. Fundamentally, the coping techniques are to help such people deal with other people’s prejudices and societal reactions to those who are disfigured by burns, injuries, or genetic deformities.

In the movie, the moment when the female alien in human skin meets the character played by Adam Pearson the plot turns, because like the alien herself, the real person who is Adam Pearson, is to be found under the skin.


After my scathing reviews* debunking the inane science fiction movie Lucy, starring Scarlett Johansson, it is nice to have this opportunity to endorse Under the Skin. People either love or hate Under the Skin. This can be explained by the fact that Lucy is a movie, but Under the Skin is a film. A film is a work of art. Art presents captivating and thought-provoking images and performances, left to interpretation by the viewer. Art transcends language in illuminating humankind and the natural world. Under the Skin exposes core issues of sex, gender roles, what it is to be human, and inhuman, but it does it in a way that requires the viewer to bring to the performance their own elusive perceptions, intrinsic beliefs, and fantasies that lie beneath the surface of thought.

For a good review of this film I recommend:

Seitz, M.A. (2014) Under the Skin Movie Review. http://www.rogerebert.como/reviews/under-the-skin-2014

* Fields, R.D. (2014) Cinema Peer Review: Douglas Fields Reviews ‘Lucy’ World Science Festival, July 29, 2014

*Fields, R.D. Lucy Debunked, Science Friday, August 8, 2014


Changing Faces http://www\

Day Elizabeth (2014) How Scarlett Johansson helped me challenge disfigurement stigma. The Guardian, April 12, 2014.

Huntley, C., Hodder, A., and Ramachandran (2015) Clinical and historical aspects of the Elephant Man: Exploring the facts and the myths. Gene 555:63-65.

Pearson, A. (2014) ‘Now that I’ve appeared nude with Scarlett, I want to be a Bond villian’: TV’s Beauty and the Beast star hopes to beat prejudice after big-screen debut. Daily Mail, March 29, 2014.

Posted by: R. Douglas Fields | December 21, 2014

The Absurdity of “Medical Marijuana”

marijuana leafMarijuana use is legal in many states for medical purposes, most of them dealing with neurological conditions (pain, epilepsy, tremor, multiple sclerosis, and many others). From the perspective of a neuroscientist researcher, the situation with respect to “medical marijuana” is absurd.

I watched as the young woman inhaled the pungent smoke deeply into her lungs and held it for a second. Clouds of blue-gray smoke exploded from her mouth and nose in a series of short violent coughs. “Sorry, this strain is kind of harsh,” she said.

Rebecca, a bright graduate student at one of the nation’s leading universities, was eager to demonstrate to me the immediate medical benefit marijuana provided her. Out of respect for her privacy, I will not delve into the specific neurological condition Rebecca had discovered was improved by the use of marijuana; moreover, the issue here is much larger than any one condition. The issue is the absurdity of current regulations on medical marijuana and the profound injury these laws are causing thousands of people, while fortifying a wall of ignorance that neuroscientists cannot easily surmount.

Rebecca has a legal prescription to use medical marijuana for her condition, which she administers by vaporizer. The condition Rebecca is using medical marijuana to treat by self-medication is chronic, serious, and there is no drug available to treat it. Rebecca has scoured the medical and neuroscience literature, and collected compelling scientific evidence for the possible benefit of marijuana for this condition, based on the expression of CB1 and CB2 cannabinoid receptors in the appropriate neural circuits involved. (These are the receptors on cell membranes that are stimulated by the active components in marijuana.) The problem is that the legal restrictions on studying marijuana in people are so arduous or impenetrable, that performing the simple experiments that would advance scientific knowledge and could lead to powerful new treatments for disease are nearly impossible.

Thankfully the horrors of the past when medical experiments were sometimes performed on people without their full knowledge and consent are gone. (In most countries.) All research involving human subjects in the United States must be reviewed and approved in advance by an independent review board that carefully weighs the risks and benefits to ensure that the experiments are ethical, scientifically warranted, and conducted properly to protect the health and interests of the person volunteering to participate in the study. This is a rigorous process and it should be.

The problem is that the laws regulating marijuana in some states, as well as federal laws, make it impossible or nearly impossible to do research on the biology of marijuana and its potential medical benefits. The PhD advisor of a graduate student I know laughed at him when he proposed to study the neuroscience of marijuana addiction in rats, because it would be so difficult to obtain the active ingredient in marijuana (THC) for experimental research. The mentor advised his student that he would be far better off to change his research to study cocaine. He did so.

A colleague of mine, a well-known expert on hippocampal synaptic function, became interested in what appeared to be a possible significant role of CB1 cannabinoid receptors on neurons in regulating development of a particular type of neural circuit. “Getting the clearance to work with THC was impossible,” he told me. The studies he proposed were on experimental rats not people, which is far less arduous than obtaining permission to do experiments on people. Undaunted, the researcher found a synthetic analog of THC that was unregulated, but was actually far more potent than THC, and he began his studies with this compound. Such cleaver circumvention of the restrictive laws on cannabinoids in experimental research are rarely possible. Moreover, any results obtained will have to be tested eventually with real marijuana, a plant that contains 60 different cannabinoids in various mixtures and concentrations that vary greatly in different plant strains.

In Rebecca’s case, the ethical issues related to studying the neurological effects of marijuana would seem much less problematic, because she has a legal prescription to use marijuana for her condition. The research would not subject her to additional risk; it would simply examine the biological effects on the patient of the currently prescribed medication. However, the researcher with the expertise to examine the effects of marijuana on her condition works at a University in another state where marijuana possession is a crime. The researcher has vigorously pursued the appropriate avenues to undertake this experiment, but it is not possible. The time and effort to gain approval to do the research are insurmountable obstacles, given the investigator’s other research responsibilities. Moreover, the judgment of officials familiar with such approvals are that regardless of the scientific merit and ethical justification for doing the research, marijuana is illegal in that state. The research could not be done there. Similarly, federal law criminalizes marijuana use, even for medical purposes, and most biomedical research is funded by federal grants.

A recent survey of the medical literature on the benefits of marijuana for the wide range of neurological conditions (published this year in the journal Neurology) found 34 studies performed between the years 1948 and 2013 that met their criteria for inclusion. Stop right there. 34 studies! Only 34 studies were found for the enormous range of neurological conditions where activation of CB1 and CB2 receptors in the brain by compounds in marijuana could have an effect? There are 32,836 studies in the scientific literature on “health and tobacco.” There are 87,735 studies on “health and alcohol” in the medical literature (PubMed search). The authors reviewing the scientific literature on marijuana found only a total of 1729 studies in the literature, but only 34 studies since the Truman Administration met the criteria to be useful for inclusion in an analysis of the efficacy of medical marijuana on neurological conditions. The criteria for inclusion required that the studies were well-designed, randomized, with placebo-controls, performed on humans; not anecdotal reports,human studies without controls or animals studies.

It is not the scientific rationale for possible effects of marijuana on neurological conditions that can account for the lack of research: the effects of marijuana on the central nervous system are obvious and potent. It is not a lack of interest among researchers in studying how CB1 and CB2 receptors regulate development and function of the brain, and how this new knowledge could lead to new drugs for treating disease and human suffering. The difference is that alcohol and tobacco are legal; marijuana is not.

Tobacco, alcohol, and morphine, are all plant products, just like aspirin. All life on this planet shares a common system of biochemistry. Compounds in plants have powerful effects on the human body, some are poisonous toxins and some are priceless cures. Plants have yielded a treasure trove of potent new drugs that have treated or cured diseases throughout human history, and eased human suffering. New drugs have been developed from plants that have changed the world. Oral contraceptives were developed from a jungle plant, leading to a technological development that has helped countless women with many medical conditions and transformed the lives of women and society by putting women in control of the biological systems at work in their own bodies. But marijuana is off limits.

Science is strangled by a government-imposed catch-22 that restricts access to marijuana on the basis that there is insufficient evidence supporting its medical benefits and safety, while blocking the research that would provide such information.

So we have this absurd situation where the use of medical marijuana is legal in 22 states, yet the scientific research that would uncover the molecular mechanisms by which this plant can treat a wide range of medical conditions is impossibly difficult to perform. In states where the drug is illegal, research is all but impossible. Businessmen decry onerous government regulations that hamper commerce and diminish financial profit, but there the losses are investor’s dollars not people’s lives to disease.

With 60 known cannabinoids in this plant, and the mixture and potency varying widely among strains and from batch-to-batch, patients are left to self-experimentation to find a strain that works for them. Is it Super Silver Haze, White Widow, Skywalker, or God’s Gift? Who knows? The patient is compelled by law to engage in desperate self-experimentation of the sort that would never be approved by an Institutional Review Board examining a proposed scientific study.

Meanwhile there are countless natural products approved for use and promoted for medical benefits that have dubious efficacy or scientific foundation– chondroitin sulfate, Gingko, green tea, resveratrol in red grapes, vitamins of every type and in endless combinations–but cannabis is banned, paradoxically precisely because the compounds in it do have obvious and potent effects on the CNS.

Rebecca discovered the beneficial effect of marijuana on her medical condition by chance in using marijuana recreationally, but she does not want to be dependent on it for her medical needs. There are far too many obvious adverse effects. Any potent drug has adverse effects, but without knowing exactly what compound or combination of compounds in marijuana are helping and which are hurting, and without the necessary scientific research to understand the biological facts that would accelerate the development of potent, effective, and safe new drugs, she has no choice. What she wants is to help scientists discover how this drug is working for her, and help them to develop the right drug that will work but not leave her stoned or at risk from other dangerous compounds in marijuana and the very real harmful effects of cannabis if used incorrectly.

So here we are in the 21st century condemned like cavemen to eat leaves or smoke them for medical uses because the legal regulations restricting access to this particular plant for scientific research are so arduous, for political reasons, that we are constrained by law to the practices of witch doctors.


Koppel, R.S. et al., (2014) Systematic review: Efficacy and safety of medical marijuana in selected neurological disorders. Neurology, 82, 1556-1563.

Posted by: R. Douglas Fields | December 8, 2014

How is the brain like a guitar? Hint: It is all about rhythm

guitarbearclawtop Typically we are introduced to the nervous system by analogy to an electrical circuit, like a door bell or a telephone line carrying a signal rapidly over long distance to activate a specific process. Never mind that electrical impulses are not transmitted through nerve axons anything like electrons flowing through a copper wire, this electronic circuit analogy is useful up to a point. If you want to understand how the brain works at a more complex level, you are going to need a new analogy, and if you play an acoustic guitar you’ll find it under your fingertips.

Dr. Hans Berger, working at the Psychiatric Clinic at the University of Jena, Germany in the 1920’s was the first person to discover that the human brain radiated waves of electrical energy that could be picked up by electrodes on the scalp. He performed his experiments in secret on hospital patients and on his own son in a small building separated from the rest of the hospital. Initially he believed that he had detected the physical basis for mental telepathy. He told no one in the scientific community about his mysterious findings until after five years of secret experiments.

Fundamentally, Berger, whose daily life was devoted to caring for people with mental illness, was searching for a physical basis for brain function. This was a leap of insight decades beyond his contemporaries. The idea that the human mind and mental illnesses have a physical basis of operation that could be reduced to physical principals and understood by approaching the operation of the mind in the same way a physicist would approach any other phenomenon in nature–by physical measurement–was well outside the realm of thinking among his colleagues in psychiatry.

His brutal approach of stabbing a thermometer deep into the brain of his patients who had survived gunshot wounds leaving holes in the skull, and then provoking various emotional and sensory stimuli to see whether their brain tissue changed its temperature in the process of mental function raises ethical questions by today’s standards. His patients must have had no real understanding of what was being done to them or why, and an attempt to monitor the intricate workings of the human brain in the same way one might use a candy thermometer to monitor the process of making fudge, seems naive in retrospect. However, Berger did not have the advantage of our vantage point. In applying the crude tools available in his day, thermometers and the newly developed electronic amplifier, Berger was doing precisely the same thing that cutting edge neuroscientists today are doing with functional magnetic resonance imaging (fMRI), which allows us to see inside the brain at work and pinpoint where, when, and how its different parts operate. Berger was a man whose scientific ideas were a century ahead of the technology needed to study them.

Brainwaves had been detected in animals, but not in humans before Berger’s experiments. What he observed by attaching electrodes to the scalp and feeding the signals into an electronic amplifier was that the human brain’s electrical activity was not entirely confined to transmission through the wire-like axons connecting neurons into circuits. Instead, the electrical energy of neurons radiated out of the skull like the electromagnetic field radiating from a broadcast antenna or for that matter from any electrical circuit. This is something we all have experienced in hearing the annoying hum of 60 cycle electromagnetic interference that radiates from our electronic devices when it is picked up and amplified unintentionally by sensitive electronic instruments.

Psychiatric hospital in Jena, Germany where Hans Berger first recorded human brain waves

Psychiatric hospital in Jena, Germany where Hans Berger first recorded human brain waves

Moreover, Berger discovered that the electromagnetic energy emanating from the human scalp progressed in waves of certain characteristic frequencies that changed with mental state. The 8-12 Hz brainwaves that he measured, originally called Berger waves and now called alpha waves, swelled in his son’s brain as he sat quietly in that laboratory with his eyes closed, but when his son opened his eyes, his brainwaves abruptly changed. The alpha waves subsided like ocean waves squelched by rain on a windless sea.

Today we know that the electrodes on the scalp are intercepting the combined activity of millions of neurons in the surface layers of the brain, the cerebral cortex, each one sending signals to another neuron in complex circuits. Like the noise of a crowd in a baseball stadium, these electroencephalogram (EEG) recordings are the combined output of all the individual conversations and exclamations going on in the crowd of neurons beneath our skull. These conversations and exclamations wax and wane and sometimes burst with synchronized cheers in response to something that has stimulated them all. But why the oscillations at such characteristic frequencies?

Human brain waves first recorded by Hans Berger

Human brain waves first recorded by Hans Berger

Scientists soon discovered that there are several different characteristic frequencies of brainwave oscillations; each one accompanies different types of mental activities, including attention, consciousness, arousal, meditation, and many other cognitive processes. The question is whether these waves of electrical energy have any function or are simply an epiphenomenon, like the roar of an engine which changes with different states of activity, but the engine’s sound has no impact on the operation of the engine. To glimpse the answer to this question, which is at the forefront of current research in neuroscience, consider the guitar.

The difference between the rich and responsive sound of a classical guitar and the twang of a banjo has nothing to do with the action of the strings that generate the sound when they are plucked. The difference is in the resonance of the guitar’s body, which not only amplifies the sound of the strings vibrating, it blends all the sounds the strings can create into a harmonious and vibrant acoustic radiation. Some frequencies of sound combine and are thus amplified, and others are cancelled out because the two frequencies of oscillation are out of phase, dampening out the sound of the string at that frequency. In the same way that noise-cancelling headphones block out sound by generating the same waveform out of phase to cancel it, that particular frequency generated when the string is plucked makes no sound. If it did, the sound would create an annoying noise because it is not a frequency compatible with the musical scale.

Luthiers, who build acoustic stringed instruments like guitars and violins, are masters at crafting all the wooden components that go into constructing the instrument such that the instrument as a whole resonates harmoniously at just the right combination of frequencies, while dampening the sounds that interfere with the optimal operation of the instrument. The luthier achieves this result by carefully evaluating the weight, dimensions, and stiffness of all the wooden components that go into making the guitar, shaving them down to precise thickness and dimensions such that he or she can consistently produce a beautifully sounding and responsive instrument. This cannot be done by following a blueprint, because every piece of wood is slightly different in weight, stiffness, grain tightness and orientation. Different types of woods vibrate at different frequencies and reflect or absorb sound waves slightly differently. There are far too many variables to consider, which is why making fine guitars is an art, not a science.

Shaving the top braces of an acoustic guitar

Shaving the top braces of an acoustic guitar

The luthier fusses carefully over the top surface of the guitar, because this plate of wood acts like a speaker cone to radiate the sound, while the back and sides of the guitar operate like the speaker cabinet to further modify and direct the sound energy. The luthier will brace the top with slips of wood and shave them with a chisel to force it to vibrate in very precise ways that will combine all of the bass and treble sounds desired into a harmonious tone. He will shave the top plate of wood down carefully with a hand plane and test the acoustic effect periodically by lifting the plate to his ear by pinching it between thumb and finger, and tapping it briskly with his knuckle. A good sound board will ring with a complex and brilliant sound when it is tapped, so this process of carefully thinning down the wood is called “tap tuning.”

As the luthier carefully shaves the top thinner the tap tone lowers in frequency because the stiffness of the wooden plate is being reduced gradually, making it better at vibrating at low frequencies and worse at vibrating at high frequencies. The decision of when to stop thinning the top is critical and somewhat mysterious, because it is not a precise frequency that the luthier’s ear is listening for; it is a certain rich complexity of tones radiating with clarity and brilliance. If the top plate is thinned too much, it suddenly becomes useless. Knowing when to stop thinning is what separates the master luthier from a furniture maker.

Guitar resonating at 220Hz

Guitar resonating at 220Hz

Guitar resonating at 600 Hz.

Guitar resonating at 600 Hz.

It is possible to see the acoustic action of a guitar top by scattering glitter over its surface and playing specific frequencies of sound through a loudspeaker. Sweeping slowly from low frequency to higher frequency the glitter covering the top suddenly begins to vibrate and dance over the surface. Suddenly at a certain frequency of sound, all the particles of glitter dancing on the surface suddenly form a tight circle. This indicates that the entire top of the guitar is waving up and down, throwing the glitter off the vibrating surface and into the stationary borders, or node. This is the fundamental frequency of the guitar’s top. When the strings generate this frequency the guitar will broadcast a strong, loud tone at this frequency–the lowest frequency the guitar can generate effectively.

Now as the luthier slowly sweeps the sound from the loudspeaker to a higher frequency, the glitter suddenly begins to dance again, and like band members at halftime the glitter comes together, re-arranges, and forms two circles on the top of the guitar as shown in the accompanying photo. The guitar top is now vibrating at higher frequency such that the left and right sides of the guitar top are each oscillating simultaneously. This only occurs at this precise higher frequency. This same process will occur at other specific resonant frequencies making the guitar vibrate in different ways and revealed by different geometric patterns of glitter formed on its vibrating surface.

Now imagine that the top of this guitar in the figure accompanying this article were the top of your brain: the cerebral cortex. If the population of neurons in the sheet of brain cells in our cerebral cortex were firing at this specific frequency what would happen? Both parts of the cerebral cortex, separated by long distances, would suddenly begin to function in synchrony, just like the left and right sides of the guitar top shown above vibrating in synchrony at 600 Hz. This is what brainwaves do. Neurons fire electrical impulses when the voltage of their cell membrane reaches a specific threshold. If the membrane voltage is fluctuating up and down slightly below the threshold for generating an electrical impulse, a signal that arrives when that neuron is close to threshold will make it fire an electrical impulse, but the same signal that arrives when the oscillating voltage is at its trough would fail to reach threshold and the neuron would remain silent. Thus, brainwaves can couple activity of large population of neurons into functional groups, just as ocean waves move all boats at anchor in a harbor in synchrony even though they are not directly tethered to each other. In this way, the transmission and operation of neurons in the brain become coupled into functional assemblies.

Such oscillation is what couples activity of neural circuits into groups, providing a way to couple neural circuits together over long distances so that they operate simultaneously, even though they are not directly tethered together. This resonance is what combines mental activities together and tunes our level of attention and other mental states. Consider, for example, how all the diverse aspects of an experience, sights, sounds, emotions, time and place, somehow get coupled together to form a memory. Without the simultaneous activity of all the neurons in different regions of the cerebral cortex all firing together, the scene (or schema) evoked by a memory could not develop. This is much like the unique sound of say, a C# minor chord, making the entire guitar operate as a system to evoke a rich and specific tone that evokes a very specific emotional and cognitive response in our brain when we hear it.

More to explore
1. For an excellent book on brain waves see: Buzaki, Rhythms of the Brain, Oxford University Press, 2011.

2. I was able to visit Hans Berger’s laboratory and go through his notebooks in researching the chapter on his research for my book The Other Brain, where interested readers can find more on Hans Berger and brainwaves.

3. Those interested in guitar building may find this article written for the Washington Post Sunday Magazine of interest. The title of the article is “The Last Guitar,” but it was changed by the publisher to “Guitar Hero.”

The guitar images accompanying this article are from the author’s workshop.

Posted by: R. Douglas Fields | November 6, 2014

‘Car Talk’ Host’s Death Illuminates Alzheimer’s

Tom and Ray “Turns out he wasn’t kidding,” said Ray. “He really couldn’t remember last week’s puzzler.” (1) On Monday Tom Magliozzi, co-host of NPR’s ‘Car Talk’ died of Alzheimer’s disease. For his many fans the dreaded disorder suddenly became personal. For many, it comes as a shock to learn that the mind-robbing disease can be fatal.

The passing of Tom Magliozzi, ‘Click or maybe he was Clack’ of NPR’s radio show ‘Car Talk’ is a bitter sweet moment, like the time my 72 VW bus threw a rod returning home to Bethesda, Maryland from a summer at Woods Hole, Marine Biology Lab right after we took a slight diversion to visit the Martin Guitar Factory in Nazareth, PA. Saddened by the abrupt ending, but grateful for the many years of joy and meandering adventures the bus had brought us. Over the years Tom and Ray entertained and enlightened us with their care-free witty banter about ailing cars and just as often faltering human relationships and they did it with obvious brotherly love. These were two guys you wanted to hang out with. They were fun and interesting, and you always seemed to learn something from them. With Tom’s death on Monday, I think he probably enlightened more people than anyone about the fact that Alzheimer’s disease can be fatal. It is perplexing that such a leading cause of death in the United States should be unknown as a potentially deadly disease to so many.

“I like to drive with the windows open. I mean, before you know it, you’re going to spend plenty of time sealed up in a box anyway, right?” (2)

Well, I hope so, but I wouldn’t be surprised if we learn that the practical joking brothers utilized Tom’s Dodge Dart in lieu of a traditional casket. Can you hear that infectious laughter?

If you don’t know Tom and Ray you will rightfully be offended by my unsanctimonious tone. But Tom was a guy who cared about things that mattered and he cared about the science of how things work. This is a guy whose favorite remedy for an idiot light that would not shut off was to cover it with a piece of black electrical tape. Pay attention to the things that matter. And no matter how seemingly ordinary the car repair question might be, Tom loved to take the scientific approach, beginning with first principles of physics to develop a complete understanding of what went wrong. So Tom would want you to know that people do die of Alzheimer’s and to understand how. Ray would groan and wait out the scientific explanation, but here it is:

Everyone knows that Alzheimer’s disease erodes memory, causes confusion, ultimately robs one of their personality and in the end can render them a terrified lost stranger in their own world, but the disease also damages other parts of the brain. This can include parts of the brain controlling vital functions, such as breathing, swallowing, and heartbeat. A study published in the journal Neurology earlier this year concluded that deaths from Alzheimer’s disease were greatly under-reported. The CDC had estimated Alzheimer’s as the sixth most common cause of death, but the new research places Alzheimer’s as the third leading cause of death, behind heart disease and cancer. “You can’t fix it,” Tom would say. There is no cure; not even a treatment that will arrest the disease once it is diagnosed. The odds of getting Alzheimer’s disease at age 85 are 50:50.

Even in leaving us, Tom enlightens.

To Ray, and the many friends and family, we share your loss, but also your blessing. According to the Car Talk website, “The family asks that in lieu flowers, or rotten fruit, fans of Tom make a donation in his memory to either their local NPR station or the Alzheimer’s Association. (3)

Write your condolences on the back of a $20 bill and send them to NPR: or to the Alzheimer’s Foundation of America:

James, B.D. et. al., (2014) Contribution of Alzheimer disease to mortality in the United States. Neurology 82:1-6.
50:50 odds at age 85 see:

Posted by: R. Douglas Fields | October 16, 2014

The Brain’s White Matter–Learning beyond Synapses

Oligodendrocyte forming myelin on axons

Oligodendrocyte forming myelin on axons

Recently scientists have been exploring part of the brain that has been relatively unexplored in learning–white matter, comprising half of the human brain. Here new research is detecting cellular changes during learning that are entirely different from the synaptic changes between neurons in gray matter. A new study shows that learning a new motor skill requires generation of new myelin, the electrical insulation on nerve axons.

Neural computation and information processing take place in the brain’s gray matter, the “topsoil” layer of brain tissue comprised of neurons communicating through synapses, but beneath gray matter billions of nerve axons connect neurons into circuits, much like underground communication cables connecting computers into functional networks over long distances. These dense bundles of cables in white matter held little interest to neuroscientists who were interested in how the brain processes information and learns. These functions were understood to depend on the formation and breaking of synaptic connections between neurons as well as adjustments in the strength of synaptic connections. But as any audiophile knows, cabling is critical to the performance of any communication system. Moreover, while it is important to board a train efficiently–much like signals entering a neuron through its synapses–the time it takes to travel between destinations can be even more important in the optimal function of the network compared with the process of “crossing the gap” into the train car. This concept, that the time it takes to transmit signals over long distances between neurons in the brain is important, has been largely overlooked in neuroscience theories of learning.

The most important factor in determining the maximal rate of impulse transmission through a nerve axon is whether or not the axon is coated with electrical insulation called myelin. Myelin boosts the speed of electrical impulse transmission by at least 50 times. People have always understood that if the myelin sheath breaks down in disease, such as multiple sclerosis, impulses can fail to travel beyond the damaged insulation and the neural circuit fails. In multiple sclerosis, for example, failure of transmission because of myelin damage results in blindness or difficulty walking. But what about the possibility that myelin might influence the proper rate of transmission between relay points in a neural circuit by adjusting the transmission speed so that impulses, like people arriving at appropriate times to catch a connecting flight, arrive at the right time at critical points in the circuit?

Evidence for changes in white matter structure during learning has accumulated in recent years from human brain imaging studies. At the same time, cellular neuroscientists have found that the formation of myelin can be influenced by electrical activity in axons. These two clues suggest that myelin may change during learning to optimize the flow of information through neural circuits. In a study to be published in Friday’s edition of the journal Science, a team of researchers from the laboratory of William Richardson at University College London, and colleagues in Australia, Japan, and Portugal, provide new evidence that learning a motor skill requires new myelin to be formed in the brain.

In the brain and spinal cord, myelin insulation is wrapped around axons by glial cells called oligodendrocytes. These cells develop from immature glia called oligodendrocyte progenitor cells (OPCs). Curiously, these immature glia persist in the adult brain in great numbers. In fact, OPCs are the major class of dividing cells in the adult brain. They comprise 5% of all cells in your brain. Why are these immature glia present in the adult brain long after fetal development?

One possibility is that these immature glia are there waiting to form myelin on bare axons in the adult brain to boost the speed of transmission in a circuit that is engaged in learning a new skill. If so, this would be a non-synaptic mechanism of learning. To test this hypothesis, the scientists studied mice that had been genetically engineered to prevent the OPCs from maturing into oligodendrocytes. They were able to control this block of OPC maturation by giving the mice a drug (tamoxifen) to block this process at any point in the animal’s life. The question they asked is whether or not new myelin is needed to learn a new skill, and by blocking the ability of OPCs to mature into oligodendrocytes, the formation of new myelin would be impaired while leaving myelin on existing fibers intact.

The mice were trained on a running wheel that had some of the rungs missing. At first the mouse stumbled over these missing rungs, but with practice, the animal learned to anticipate the missing rungs and step past them nimbly to run the treadmill with ease. The results showed that the mice that could not make new myelin learned this task much slower than normal mice. So no matter what changes in synaptic communication were taking place in gray matter to help the mouse learn to run on the modified wheel, if new myelin could not form, the animal’s performance would be impaired.

The researchers found that when an animal is trained on the running wheel, OPCs started to divide in its brain (in the corpus callosum, which are axon cables connecting the right and left hemisphere). By 4-6 days after training, there was a 40% increase in the number of OPCs that were dividing, and by three weeks there were many newly formed oligodnedrocytes. When this increase in oligodendrocyte production was impaired by genetic manipulation, the ability of mice to learn to run on the wheel was impaired.

An interesting finding was that quite similar increases in OPC cell division were also seen in the brains of control mice that were allowed to run on a standard running wheel, compared with mice kept in a normal cage without a running wheel. Possibly motor functions common to wheel running, such as grasping the rungs, are improved through myelination by running on the normal wheels as well. Alternatively it might be that exercise or novelty increase OPC production in the adult brain, not necessarily learning specifically. This benefit of enriched environments and exercise on OPC production in the adult brain is something that has been noticed in several other studies. This raises the question of whether new myelin is formed by the learning process to speed impulse transmission through the circuit required for the task, or instead there might be a general benefit of capacity for myelination in the adult brain by providing a better network structure for motor learning and performance.

Studies in aged humans show that myelin begins to degrade in aging and that learning new skills improves the integrity of white matter in the brain by slowing loss of myelin (Engvig, et al., (2012). The mice in this study were not aged, but still there might be a constant process of myelin renewal that could be difficult to detect but important for motor performance. This renewal would be undermined by the genetic manipulation blocking the formation of new myelin. In an e-mail, William Richardson agrees that this is an alternative possibility, but he doubts that this is as important as the formation of new myelin on circuits that must improve their performance during motor learning. “There is no detectable loss of oligodendrocytes after one month or three months,” the age at which these studies were performed, he says.

Richardson also offered a peek at what may be on the horizon. In comparing the rates of learning between controls and mice unable to form new myelin they noticed, “That the difference between [experimental and control mice] starts to develop less than 2 hours after first introduction to the wheel. At face value, therefore, myelin…is involved in the early events as well as the later events [of learning].”

This is intriguing because recent brain imaging studies have detected changes in white matter structure in the human brain by magnetic resonance imaging within two hours of training on a race car video game (Hofstetter et al., 2013). “Maybe the early events involve new protein production (Wake et al. 2011), while the later events contribute to long-term memory/consolidation,” Richardson says. (The study he is referring to found that the synthesis of myelin proteins is stimulated by electrical activity in axons, so that oligodendrocytes in contact with axons firing impulses begin to form myelin rapidly on those fibers.)

After a century of research focused on the synapse to understand the cellular basis of learning and memory, neuroscientists are excited to find that there may be much more in store in the neglected white matter regions of the brain involving non-neuronal cells, glia, that have been largely overlooked by most neuroscientists. The questions presented by this elegant new research are fascinating. For example, how do oligodendrocytes know which neural circuit to myelinate during learning, that is, how do they sense electrical activity in axons? What are the molecular mechanisms that control activity-dependent myelination? If these molecules can be identified, new approaches to treating nervous system disorders might be found, because abnormal transmission of information is associated with mental illnesses as well as neurological illnesses. How is this cellular mechanism of learning different from learning based on synaptic plasticity? For example, do improvements in transmission of information through a neural network explain why learning a difficult motor skill, such as riding a bike, takes so much practice, but suddenly everything kicks in and once the training wheels come off, you never forget how to ride a bike the rest of your life?

“Plenty more experiments up ahead!” Richardson exclaims.

More to explore

Bracken, Kassie (2009) The brains behind talent, The New York Times

Engvig, A., et al., (2012) Memory training impacts short-term changes in aging white matter: a longitudinal diffusion tensor imaging study. Human Brain Mapping 33, 2390-2406.

Fields, R.D. (2008) White Matter Matters, Scientific American (March 2008) 298, 54-61.

Fields, R.D. (2012) Social interaction in early life affects wiring to the frontal lobes The Huffington Post November 13, 2012

Hofstetter, S., Tavor, I., Moryosef, S.T., and Assaf, Y. (2013) Short-term learning induces white matter plasticity in the fornix. J. Neurosci. 33, 12844-50 (2013).

**McKenzie, I., Ohayon, D., Li, H., Paes de Faria, JH., Emery, B., Tohyama, K., and Richardson, W.D. (2014) Motor skill learning requires central myelination. Science, October 17, 2014 issue.

Wake, H., Lee, P.R. and Fields, R.D. (2011) Control of local protein synthesis and initial events in myelination by action potentials. Science 333, 1647-51.

** Reviewed in this article.

Posted by: R. Douglas Fields | October 13, 2014

Ebloa on the Brain

On September 23, 1976, while the nation’s attention was focused on the battle between Gerald Ford and Jimmy Carter for President of the United States, a 42-year-old woman half way around the world was engaged in a personal battle. Outside the limelight of world view, her struggle for life in a remote third world country marked the crossing of a threshold for our species. Rapidly others from her region began to appear in hospital with the same symptoms: fever, sore throat, muscular pains, vomiting, diarrhea, and most shockingly breakdown of the body’s capillaries and small blood vessels, causing internal bleeding. The whites of their eyes turned red with blood seeping into tissue. A disturbingly high percentage of hospital personnel quickly developed the same fatal disease. This was a highly contagious and highly fatal disease unlike any other known.

Specimens from throat swabs, urine, and blood from these patients were sent to labs around the world; first to the Microbiological Research Establishment in England and to the University of Antwerp. Then from the lab in England samples were sent to the Virology Division at the Center for Disease Control in Atlanta, Georgia. Through electron microscopes in these modern laboratories human beings saw for the first time a new virus and a new deadly threat to humanity. The virus particles had a close relation to the Marburg virus, but the envelope encapsulating it was clearly but subtly different. In consultation among the world’s experts they named this new virus Ebola, after a small river flowing westward north of Yambuku in Zaire, past the small village where the first person became ill and provided the sample to isolate this new germ.

The disease is categorized as a hemorrhagic fever, meaning that it is accompanied by bleeding and fever. The virus ravages the body’s organs, liver, spleen, kidney, lungs, testis, and especially the vascular system, but the purpose of this article is to describe how the virus affects the brain. Most of what we know about Ebola comes from animal research on rats, rabbits, guinea pigs, and monkeys.

Clearly the brain is affected in Ebola patients, who quickly lose the ability to walk and suffer convulsions. The assault on the brain comes from two fronts: injury to the brain’s vascular supply and biochemical disruptions in the body as a result of kidney and other organ failure. The blood vessels in the brain become severely congested and some begin to bleed causing brain stroke. Disruption of the normal potassium, sodium, and calcium concentrations, and other biochemical changes in the body from renal failure, disrupt the mechanisms of brain cell communication and ultimately damage brain cells. Primarily, though, the virus replicates in the vascular system, infecting the cells that make the walls of blood vessels, as well as cells flowing in the blood, the lymphocytes and monocytes. As the blood vessels degenerate, blood seeps out into the surrounding tissue. The patient goes into shock caused by severe blood and fluid loss, which makes it impossible for the heart to supply blood to the body’s organs, and they stop working and die. The brain is very vulnerable to loss of blood flow. The brain uses 20% of the body’s energy supply even though it comprises only 5% of body weight.

While you read this article consider for a moment how the world torn as it is by politics and separated by geography is united in biology. And consider that in Dallas, Texas today another woman whose name is not public lays suffering in bed in a hospital room completely isolated. She is a nurse who cared for and comforted Thomas Eric Duncan through the last horrible days of his life. Duncan was the first patient to become ill with Ebola in the United States. He died last Wednesday.

The heroism of service men and women in combat and of the brave first responders who rush into burning buildings to save the life of a stranger that we so justly admire and honor with metals cannot allow us to overlook the silent selfless heroism of nurses and other health care providers who silently and with unwavering commitment risk their own lives for the same cause: to help another human being who is facing death. The courage to risk surrendering one’s own life to save the life of a stranger reflects the noblest character of mankind.

More to Explore
Bowen, E.T.W. et al., (1977) The Lancet March 12, p. 571
Pattyn, S., et al., (1977) Isolation of Marburg-like virus from a case of haemorrhagic fever in Zaire. The Lancet, March 12, p. 573
Johnson, K.M., et al., (1977) Isolation and partial characterization of a new virus causing acute haemorrhagic fever in Zaire. The Lancet, March 12, 1977
Baskerville, et al., (1985) Ultrastructural pathology of experimental Ebola haemorrhagic fever virus infection. J. Pathol. 147:199-209.

Posted by: R. Douglas Fields | August 30, 2014

Sharks Use ESP


As beachgoers flock to the ocean over Labor Day, thoughts of “jaws” will inevitably surface. A shark’s ability to home in on the scent of blood is legendary, but many people are surprised to learn that sharks have a stealthy sixth sense to find prey and explore the world around them. Sharks have the ability to sense an electric aura that surrounds all creatures in seawater–including people.

This sixth sense works where vision fails, in murky water, at night, and when prey animals are buried under sand. This extra sense of perception (ESP) is called “electroreception.” Human beings can only imagine what it must be like to “see” a world of electrical auras the way sharks do.

For four hundred million years sharks and their relatives, the chimaeras and rays, have been using a force of nature that our species learned about only recently–electricity. And, sharks knew something about electricity that scientists never imagined until the 1970s: that all organisms in seawater are surrounded by a weak bioelectric field that pulsates and changes with the animal’s movements and physiological activity. With the surprising discovery of bioelectrical fields, a neuroanatomical mystery extending back to the 1600s was finally solved.

If you look closely at the head of any shark or ray you will see that it is stippled with small pores focused around the mouth. The first person to have examined a shark must have seen them, but what are they?

In 1678, anatomist Stephano Lorenzini guessed that they might be the openings of glands to coat the fish with slime. Squeezampullae raying the pores does expel a crystalline jelly substance. But this doesn’t seem quite right. Sharks are not slimy. In fact, the clear gel inside the pores does not resemble any bodily secretion.

Lorenzini had second thoughts. Writing by candle light centuries before electricity was discovered, and he wrote in his notebook that these mysterious openings must have some hidden function; thus calling on scientists of the future to solve this puzzle of Nature.

If the shark’s skin is peeled away carefully you will see that the pores are openings of long clear tubes, some nearly the diameter of a spaghetti noodle and in some cases nearly as long, but most are much smaller. The tube ends in a swelling somewhat like an eyedropper bulb. A slender nerve trails out of the end of the swollen ending. This structure reminded anatomists of Roman long-necked flasks, called ampulla, so these strange tubes found only under the skin of sharks and their close relatives became known as “ampullae of Lorenzini.”

Anatomists tracing the nerves from the ampulla saw that they entered the brain through the top side or dorsal surface. This vital clue meant that ampullae of Lorenzini are sense organs, not glands, because sensory input to the brain–touch, temperature, pain, etc., enters through the dorsal side of the spinal cord, whereas nerves that control muscles exit from the ventral (bottom) side of the brain and spinal cord. But what sense could these strange tubes, unlike any other sense organ in any other animal, possibly detect?

Soon after the electronic amplifier was developed early in the 20th century, physiologists began to use them to detect the weak electrical impulses traveling through nerves. Alexander Sand in 1938 found that when he amplified the signals sent out the nerves of the ampullae of Lorenzini the impulses changed their rate of firing depending on the temperature. The organs were extremely sensitive “thermometers,” detecting changes in temperature as small as 0.2 degrees C. Thus, these organs must allow sharks to detect small temperature differences in seawater.

But when R.W. Murray was repeating Sand’s experiments in the 1960’s, he accidentally switched on an electrical stimulator and the ampullae of Lorenzini responded by firing a burst of electrical impulses down the nerve. Startled by this discovery, he did further tests and found that the organs were remarkably sensitive “voltmeters.” Astonishingly they were more sensitive to weak electric fields than all but the most sensitive electrical instruments available to measure voltage.

Further research by Murray and others showed that gently touching the ampullae also caused nerve impulses to fire, and that the salt concentration and pH of a solution applied to the openings also stimulated nerve impulses in the organs. Now neuroscientists faced a difficult question: How is it possible to know which of these stimuli is the natural stimulus for these sense organs? Touch, taste (salt and pH), and temperature are common senses, but other animals cannot sense such weak electricity. Is it possible that these creatures have a 6th sense that other animals do not have? But if the ampullae of Lorenzini were “voltmeters,” why would a shark have sense organs to detect electricity?

The answer came in the 1970s when neuroscientist Adrianus Kalmijn made a surprising discovery. Using very sensitive electronic instruments he found that all animals in seawater have a very weak electrical field surrounding their body. Further behavioral experiments showed that sharks could locate prey by sensing the fish’s bioelectric field, even when hidden beneath the sand. Moreover, electrodes buried in the sand that emitted weak electric fields just like those surrounding any fish, provoked the shark to attack just as if the electrodes were a hidden prey item. This proved that the sense organs were indeed used by sharks in a normal behavior (feeding) to detect weak electric fields.

This bioelectric aura is not mysterious. It is generated just like electricity is produced in an electric battery. When positive and negatively charged ions in a solution are separated by a barrier, the imbalance in charges in the two compartments creates a voltage, simply because positive and negative charges attract. If there is not an equal balance of charges on both sides of the barrier, a small voltage will be created. In animals the barrier of separation is the animal’s skin and the two different salt solutions are the salty ocean outside the skin and the somewhat different salts in body fluids. This creates and extremely weak voltage, but ampullae of Lorenzini are so sensitive, they could detect whether or not a 1.5 V flashlight battery connected across the distance of the Atlantic Ocean was switched on or off.

In research on electroreception studying blue sharks at sea near the Woods Hole Oceanographic Institution, my colleagues and I observed that sharks would follow the scent of bait (ground-up fish that we pumped through a tube), but in the last moment of attack electroreception would take over and the shark would bite electrodes emitting a weak electric field placed a meter away from the food source. This revealed that surprisingly, electroreception is the most important sense a shark uses to orient its jaws in the final moments of attack, even overriding the scent and smell of blood.

I don’t believe that a shark repellent can be made to stop a shark in a feeding frenzy, but from these experiments I can see how we might use electroreception to avoid being attacked by sharks. By trailing a slender wire behind a swimmer or surfer emitting a weak electric field, the shark would attack the decoy electrode instead of chomping down on its intended meal. Like lizards escaping a predator by dropping its tail as a decoy, the electrical decoy could be life-saving.

Interestingly, in 2003, physicists temporarily and mistakenly revived the long-discarded theory that ampullae of Lorenzini are temperature receptors. This was based on an experiment in which they squeezed out some of the clear gel from the ampullae of Lorenzini onto a microscope slide. The researchers put the two electrodes from their sensitive voltmeter into the gel and heated or cooled one end and discovered that a voltage was generated. What they overlooked was something sharks know well. Metal in contact with a salt solution creates a battery, and the probes of the voltmeter were metal. As everyone knows, the amount of voltage a battery generates depends on temperature.

In reality, the salty gel inside the tubes is just a good electrical conductor. It does not generate electricity. The gel conducts the voltage through the tubes acting like an antenna to collect the bioelectrical signals and send them to voltage sensing cells in the bulb-like ending of the organ. This also explains why so many different kinds of stimuli affect ampullae of Lorenzini. This happens because voltages are affected by very many factors. This also illustrates how rich the sense of electroreception must be. Salt concentration, temperature, pH, and many other factors will affect the bioelectric field surrounding an animals, just as light is reflected differently from many different kinds of surfaces, giving us great insight into properties of different materials that we see. Sharks must be able to learn a great deal about the world from their sense of electroreception.

Experiments using food to study shark behavior can lead to an overly simplistic view of the purpose of ampullae of Lorenzini. Like vision or hearing, electroreception does not exist for only one purpose. Electroreception provides sharks with a unique and very sophisticated means of analyzing the world around them. We humans can only imagine what it must be like to see the world through a strange sixth sense.

More to explore
Fields, R.D. (2007) The shark’s electric sense. Scientific American, August, p. 75-81.

Fields, R.D., Fields, K.D., and Fields, M.C. (2007) Semiconductor gel in shark sense organs? Neuroscience Letters, 426, 166-170.


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