Posted by: R. Douglas Fields | September 29, 2015

What’s in Your Nightmares? The Top 5 Recurring Dreams of Adults and Kids

dreams-skull-lowresWe spend a third of our life in a completely altered state of consciousness, indeed madness. Dreaming is a descent into what would otherwise be a severe form of psychosis, and often these hallucinations are terrifying. Dreams that reoccur are especially disturbing, and nearly everyone has experienced them. A new study reveals the most common content of recurring dreams and finds very different hallucinations in the dreaming minds of adults and children.

What’s in your dreams — especially dreams that revisit night after night? Are you flying high above the heads of other people in gleeful euphoria? Are you sharing a tender moment with a loved one in a beautiful surrounding? Or are you terror struck, running for your life from a monster or murderer, immobilized by paralysis or rendered mute as an intruder breaks into your bedroom. Maybe you are tumbling through the air helplessly or badly injured?

The first finding of this study of several hundred boys and girls between the ages of 11 and 15, by Aline Gauchat, Psychologist at the Université de Montréal and colleagues, is that most reoccurring dreams are not pleasant. They are most often terrifying confrontations with deadly threats of some sort. But the reoccurring dreams of kids, adolescents, and adults differ in interesting ways.

There is a long history of research on dreams of adults, but according to Gauchat, their new study published in the journal of Consciousness and Cognition is the first to investigate the content of recurrent dreams reported directly by children. Up to now, insight into recurrent dreams of children was gleaned by questioning adults about their personal memories of their childhood dreams. Such recollections are likely to be unreliable, as memory fades and can be very selective.

Here are the most common themes of recurrent dreams categorized in the present study:

Common themes in recurrent dreams

Being chased (Dreamer is chased but not physically attacked)

Physical aggression (Threat or direct attack on one’s person or character, including sexual aggression, murder, being kidnapped or sequestered)

Falling (Feeling of falling in mid-air, off cliffs or from another elevated object)

Car accidents (The dreamer or another character is involved in a car accident)

Contact with strangers

Death of the dreamer

Death in the family

Confrontation (Dreamer is confronted by monsters, animals, zombies, or similar creatures)

The dreamer is injured or ill

Stranger entering the dreamer’s house (A stranger is breaking into the dreamer’s house or trying to enter it)

Being stuck or trapped

Others (Dreams including flying or of control and facing natural forces as well as other idiosyncratic themes)

The first finding was that only 9% of the recurrent dreams of children between the ages of 11 and 15 were positive experiences. Most recurrent dreams involved serious threats, with confrontations with monsters, animals or zombies, being the most frequently reported category. The next most common theme in recurrent dreams of children involved threats of physical aggression, falling, and being chased. In 87.9% of the children’s dreams, the dreamer is the target of the threat. Themes involving car accidents occurred in 6.9% of boys and girls, but the threats to girls were twice as likely to be related to being chased (11.3% vs. 6.5%). All the other common themes reported in recurrent dreams comprised only 6% of the narratives children reported.

It is interesting to compare these new results with a 1996 study by Zadra et al., on 110 adults. As with children, most of the recurrent dreams of adults were disturbing (77.3%). In contrast to children where 45.5% of the threats involved recurrent dreams of aggression and violence, this theme dropped to third place in the top 5 themes of content in adult recurrent dreams, with escapes and pursuits being the most commonly experienced recurrent dream of adults (25.9%). Interestingly, dreams of physical anomalies were common in the recurrent dreams of adults, but this terror was absent from the sampling of children reporting their dreams.

Table 1. Most common recurrent dreams of children

1. Aggression and violence (45.5%)

2. Accidents and misfortunes (28.8%)

3. Escapes and pursuits (22.7%)

4. Disasters (4%)

Dreams about failures and physical anomalies were not reported by children.

Table 2. The most common recurrent dreams of adults

1. Escapes and pursuits (25.9%)

2. Accidents and misfortunes (19.7%)

3. Aggression and violence (19.0%)

4. Physical anomalies (17%)

5. Failures (6.9%)

Dreams that the researchers found were absent from interviews with children, were the adult dreams of losing one’s teeth, being unable to find a private toilet, and discovering or exploring new rooms in a house. One striking result was that while friendly interactions were present in almost one third of girls’ recurrent dreams, they occurred in fewer than 3% of boys’ recurrent dreams. In studies of adults, women’s bad dreams are more frequently centered around interpersonal conflicts and women’s dreams are twice as likely to contain friendly interactions as men’s are.

What’s it all mean? The authors speculate that recurrent dreaming is related to life stresses and that imagining these threats in a dream state simulates threatening events of real life, thereby enabling our mind to rehearse strategies to avoid and confront such threats. Since real world threats to boys and girls, men and women, are somewhat different, so too are their threatening recurring dreams. Children are much more likely to experience threats from imaginary creatures and monsters than adults are. Adults, through life experience, have learned that monsters do exist, but they are usually human beings.


Gauchat, A., Seguin, J.R., McSween-Cadieux, E., and Zadra, A. (2015) The content of recurrent dreams in young adolescents. Consciousness and Cognition 37, 103-111.

Photo credit: Photo and video clip by the author, from the catacombs beneath the streets of Paris.

Posted by: R. Douglas Fields | July 25, 2015

Alzheimer’s Disease—America’s Tsunami

us-senate-vote-ipoWASHINGTON, D.C.– Amidst a tempest of election season political turbulence, a wave of bipartisan unity is rising in support of biomedical research, according to two US Senators speaking on Tuesday at an Alzheimer’s disease forum in Washington D.C., organized by AtlanticLIVE. “Every one of us knows how vulnerable we are,” says Senator Dick Durbin, D-IL. The Democratic senator shared the stage with Republican Senator, Susan Collins, R-ME who warns that the nation is facing a “tsunami of cases.” As baby boomers enter old age and people are living longer, one out of two people who reach the age of 85 will develop Alzheimer’s disease. “Alzheimer’s disease is going to bankrupt Medicare and Medicaid,” she says. “We cannot afford not to make this investment [in research].”

Despite the prolonged budget battles in congress, funding for medical research seems to be emerging as a possible exception to the long string of miserly cuts in federal spending. “This is special,” Durbin says of funding research on disease. “I believe this issue covers the spectrum [of political opinion].” Senator Collins is seeing the same support building from her Republican allies. “Constituents resonate to Alzheimer’s disease [as a government priority],” she says. Even ardent critics of the contentious Affordable Care Act (Obama Care), including Sen. Lindsey Graham, R-SC, and former Florida Governor Jeb Bush, are united with liberal Democrats on this issue. Collins cites a recent concrete example, “Republicans are in control of the Senate,” she says, “and they just authorized a 60% increase in Alzheimer’s disease funding.”

Members of congress from both sides of the aisle are calling for a national strategy to defeat Alzheimer’s disease, modeled on the rapid response to the AIDS epidemic or the war on cancer started 40 years ago. Last week Senator Collins proposed new legislation to address the lack of long-term care, for example to provide the custodial in-home care that an Alzheimer patient must have. Senator Durbin has proposed a 5% increase in budget to the NIH per year for 10 years to make the necessary investment for breakthroughs in Alzheimer’s disease and other biomedical research.

From Senator Durbin’s perspective this issue goes beyond improving health and relieving human suffering; he sees biomedical research as a matter of national security. The number of research grants funded by the NIH has declined every year for the past 10 years. Between 1999 and 2009, Asia’s share of worldwide research and development expenditures grew from 24 percent to 32 percent. Meanwhile, American expenditures fell from 38 percent to 31 percent. “America’s place as the world’s innovation leader is at risk as we are falling behind in our investment in biomedical research,” he says.

Biomedical research is a powerful force for economic growth. Senator Durbin cites the Human Genome project as an example where the federal investment has been paid back many times over in technological development and economic gain. This is something that has not escaped notice of leaders in other countries, Senator Durbin observes. “Look at what China is doing. They want to be dominant [in biomedical research and in political leadership in the 21st century]. “We better wake up to this reality,” Durbin warns. “America needs to make a strong commitment to biomedical research in the 21st century,” he says.

But is a cure for Alzheimer’s disease realistic? With the exception of rare genetically-induced forms of early onset Alzheimer’s, no one believes that there will be a silver bullet cure for Alzheimer’s disease. This is because Alzheimer’s disease and dementia are a multifactorial problem, says Richard Mohs, Vice President for Neuroscience Clinical Development at Eli Lilly and Company, who also spoke at the forum. Looking to the future from his perspective in the pharmaceutical industry he predicts, “I don’t think we’ll see the disease disappear–at least not in my lifetime. But the risk will go down, just as it has with heart disease.”

This is far more than a glass-half-full view of the problem, because slowing the progress of the disease may be enough. “It [Alzheimer’s disease] is a slow underlying pathology. . . Slowing the disease is essentially a cure for many,” he says, “because of their advanced age.” Senator Collins adds, “If we can delay onset even five years, it pays for the cost of research,” because the cost of caring for someone with Alzheimer’s disease is so enormous. Mohs predicts that the solution to Alzheimer’s disease will involve a combination of life-style changes (including diet and exercise) and drug treatments, much the way diabetes is managed successfully today.

The key will be early diagnosis. PET (positron emission tomography) scanning is a brain imaging technique that can detect amyloid deposits in the brain 10 to 15 years ahead of the memory loss. These deposits eventually damage brain cells and cause dementia. Drugs that have been developed to attack these deposits of amyloid protein show promise, but they don’t cure the disease. In fact, in some cases these drugs have worsened the disease. The consensus of experts is that drug treatment must be started much earlier, before years of slowly advancing pathology reach a point of no return. This is why identifying risk factors and early signs of Alzheimer’s disease at the pre-symptomatic stage are so important. PET scanning can do this a decade before symptoms begin to appear, but the technique is specialized, expensive, and invasive. Unlike MRI brain imaging, radioactive substances must be injected into patients to reveal the amyloid deposits in the brain using a PET scan. New tests to detect proteins in body fluids, cerebral spinal fluid, and even saliva, hold great promise as early warning signs of the disease that could warrant further testing. If simple tests find evidence for Alzheimer’s disease, then early treatments could be started to knock the amyloid deposits out before the brain becomes severely damaged. “Recovery may be possible,” Mohr says, even in those who now have AD, if the progress of the disease could be slowed or therapies to promote cell regeneration and repair were used, because the brain will repair itself if it can.

Alzheimer’s disease affects not only the person afflicted, erasing their memories and leaving them isolated, lost, and dealing with multiple debilitating brain dysfunctions, but it also affects everyone in the family. Senator Collins knows this from “having seen this very close [in her family]. . . Alzheimer’s disease affects even a grandchild whose name is no longer remembered.”

Today there are 5 million Americans with Alzheimer’s disease. There are 43 million family caregivers dealing with the chronic debilitation in loved ones, $450 billion in uncompensated long-term care. Americans aged 85 and older are the fastest growing segment of the population. What we are seeing is only the start of what is certainly a health care tsunami about to roll over American. Making the investment in medical research now will better prepare us to meet that impending crisis.


Alzheimer’s: The Cost of Caring, The AtlanticLIVE

Durbin Introduces The American Cures Act, Press release March 12, 2014

Senator Collins Announces New Legislation in Support of Family Caregivers at National AARP Event. Press Release, July 8, 2015.

Adapted from, Fields, R.D. Burying Political Hatchets to Fight Alzheimer’s Disease. Scientific American Guest Blog, July 23, 2015

Posted by: R. Douglas Fields | July 20, 2015

Why no one helped

KnifeOn Saturday, July 4, 2015, a horrifying bloodbath erupted before the eyes of passengers on the Red Line Metro subway train heading to Fourth of July festivities in Washington, DC. Wide-spread criticism in the press and social media erupted over the “apathetic” response of onlookers who reportedly said or did nothing to help the victim. But from the perspective of brain science, this scornful criticism is misguided.

A man on the Metro train snatched a cell phone from 24-year-old Kevin Joseph Sutherland. In the struggle the robber viciously beat, kicked, and stabbed the life out of the young man, inflicting 30-40 knife wounds. Passengers fled to opposite ends of the car and watched as the recent college graduate was murdered gruesomely. At the next stop the blood-spattered murderer walked casually off the train and escaped into the crowd. Police later identified 18-year-old Jasper Spires from bloody clothing, a knife, and other evidence found in a trash can.

In a commentary in the Washington Post, columnist Petula Dvorak contrasts the apathy of Metro riders with the heroic action of passengers on United Flight 93 who resisted the September 11, 2001 hijackers, and with a local man, Dylan Rawls, 31, who instantly risked his life to save a stranger being violently attacked in a parking lot. Disgusted, some cite the Metro subway tragedy as a sign of society’s moral decay. Others boast with empty bravado in online superhero fantasies about how they would have dispatched the killer. Traumatized witnesses are agonized, second guessing their reaction to the horror.

The finger-pointing reflects a fundamental misunderstanding of the neuroscience of how the brain responds to sudden threats. I know, because like Kevin Sutherland, I was once robbed on a subway, and I reacted the same way he did. I instinctively fought with the robber to get my wallet back. I succeeded, but I was lucky. Had my chance encounter been with a homicidal maniac of the likes that intersected Kevin’s path, I could have been killed just as brutally. But I didn’t think. I just reacted. In a fraction of a second I risked my life in a deadly fight with a criminal without any conscious deliberation. As a neuroscientist, I was driven to understand the threat detection circuits inside my brain.

The actions these threat detection circuits trigger–to fight, freeze, or flee–have momentous consequences. Enormous amounts of data must be evaluated instantaneously. If done consciously this analysis would take too long; moreover, the demands of this complex analysis would overload the feeble capacity of our conscious mind. “I wasn’t thinking,” Rawls said in recalling his heroic act. “Had I stopped, thought about it, weighted the pros or cons, had I had time to react, I might’ve scared myself out of helping.”

It may be comforting to indulge in speculation about how you would have responded to the deadly attack on Kevin, but the fact is that it is difficult to know how anyone will react to a sudden threat. A person’s response depends on a complex set of situational factors, the nature of the treat, and internal states of body and mind at the moment–all assessed in a fraction of a second and acted upon instantly. This must be so. The multiple factors and uncertainties presented means that there is rarely one correct response to a sudden threat. The identical reaction Kevin and I had to being robbed, with opposite outcomes, demonstrate this dramatically.

Some of the factors determining how one will respond to a sudden threat are being identified as neuroscience is beginning to tease apart the complex circuitry of our brain’s threat detection mechanism. This circuitry is largely subcortical; that is, it operates beneath the level of consciousness. Of paramount importance in threat detection and rapid response is the amygdala, located deep in the brain, which alerts us to danger, learns from bad experiences, and engages the body’s automated “fight or flight” response. This response is triggered when the amygdala activates the same region of the brain that controls other powerful unconscious urges including sex, thirst, and hunger: the hypothalamus. The release of adrenalin and other signals set our heart racing, muscles twitching, and body sweating to battle or to flee.

Danger signals shoot through high speed pathways to the brain’s threat detection circuits rather than engage our cerebral cortex. For example, there is a high-speed pathway from the retinas in our eyes to the center of the brain’s threat detection region. Most visual information from our eyes is transmitted to the cerebral cortex at the back of the brain. Here complex analysis enables us to interpret the shifting patterns of light and shows cast on our retinas as objects in space, with color, dimension, motion, and identity. But, this sophisticated visual processing takes time–too much time to dodge a left hook, for example. In bypassing the visual cortex, the rapid subcortical pathway from the eyes to the amygdala alerts our threat detection system like a motion detector in a home security system. No image is formed, but whatever has just intruded into our visual field should not be there!

New research is finding that different types of threats engage different threat detection circuits. A mother rat snapping aggressively to protect her young, for example depends on circuits in the ventral premammilary nucleus (PMv) of the hypothalamus, but a different type of threat, aggression related to social defense for example, passes through a different hippocampal relay point, the dorsal premammillary nucleus. Genetic and environmental factors will also influence the strength of these different circuits in different individuals, as will hormonal fluctuations, chronic stress, and many other factors.

Bystander apathy is a psychological phenomenon in which witnesses to a person being harmed are less likely to intervene the more people there are present. This is thought to be a consequence of the herding instinct of human beings to do as they see others do. But when many people are present it is a much more complex situation. This leads to confusion. Is the person being attacked a victim or are they gang members in combat? But neither apathy nor confusion is what those riders on the Metro train experienced. They experienced terror.

I cannot know what those witnesses lived through on that train, but I am confident from my knowledge of neuroscience that they did exactly the right thing. Their response is not a matter of bravery or cowardice or apathy; it is a matter of deadly strategy. Engaging the homicidal robber physically could have resulted in mass casualties. From all the situational information those people rapidly assimilated, that was their collective conclusion. Instead, the passengers tried to appease the robber with cash. No one else lost their life.

Honed by eons of evolution in a dangerous world of survival of the fittest, the reaction these neural circuits trigger is usually correct; otherwise our species would have gone the way of dinosaurs. This is why rational Monday morning quarterbacking about the passengers’ response on the Metro Red Line is misguided. No fault should be leveled against any individuals on that train. They did as their brain and evolution has equipped them to do.


Dvorak, P., “Hear the roar of armchair Metro heroes, The Washington Post, July 10, 2015, p. 9A.

Hermann, P., “Horrified passengers witnessed brutal July 4 slaying aboard Metro car. The Washington Post, July 7, 2015.

Motta, S.C. et al., (2013) Ventral premammillary nucleus as a critical sensory relay to the maternal aggression network. Proc. Natl. Acad. Sci. USA August 27, 2013 110:14438-43.

Shang, C., et al., (2015) A parvalbumin-positive excitatory visual pathway to trigger fear responses in mice. Science, June 26, 2015, 348:1472-7.

Adapted from: Fields, R.D. Why Nobody Intervened in the July 4 Metro Murder. Scientific American Guest Blog: July 17, 2015

Why We Snap, by R. Douglas Fields

Posted by: R. Douglas Fields | June 26, 2015

To Flee or Freeze? Neural Circuits of Threat Detection Identified

jack-nicholson-shelley-duvall-shiningSuddenly something streaks into your peripheral vision. Instantly, you jump back and raise your arms defensively. “What was that!” You exclaim in shock. Only then do you realize that the blurred streak you just dodged was a wayward basketball zinging like a missile on a collision course for your face. A rush of adrenaline flushes through your blood setting your heart pounding and muscles twitching, but there is nothing left to do. Your brain’s rapid response defense system has already detected the threat and avoided it before your conscious mind is even engaged. How is that possible, scientist, Peng Cao and colleagues of the Chinese Academy of Sciences wondered?

The mystery runs deeper. The sight of a sudden threat can trigger the completely opposite response–you may freeze like a deer in the headlights. Sometimes freezing is the best move. Spotting a rattlesnake in the bush, perhaps, is best handled by freezing. Running away could provoke the reptile to strike. But neither response–freezing nor fleeing–is a deliberate, conscious reaction to a threat that looms so quickly you can scarcely perceive what it is. These familiar facts must mean that all of the neural processing for this life-saving reaction takes place in neural circuits that are not located in the cerebral cortex where consciousness arises. These neural circuits that suddenly grip control of your behavior, known as the “fight-or-flight” response, must reside in deeper layers of the brain.

Previous research has shown that there is a high-speed pathway from the retinas in our eyes to the center of the brain’s threat detection region, which includes the amygdala and related structures comprising the limbic system. The majority of visual information detected by the retinas is transmitted to the cerebral cortex at the back of the brain, where complex analysis enables us to interpret the shifting patterns of light and shows cast on our retinas as objects in space, with color, dimension, motion, and identity. This sophisticated visual processing takes time. The subcortical pathway from the eyes to the amygdala is fast, but we are not able to actually see what the object is, because the necessary analysis for vision requires the cerebral cortex. But that route through the visual cortex takes far too long to dodge something like an opponent’s right hook. This high-speed, subcortical threat detection pathway is like a motion detector in a home security system. A moving object in the environment sets off an alarm that there is an intruder. Whatever it is, we can’t say for sure, but it should not be there!

Cao and colleagues traced out this circuitry in detail and they have identified the specific neurons that control whether we flee or freeze when an object suddenly looms in our visual field. The first relay point for high-speed information transmission from the retina to the brain is a region called the superior colliculus. There are three different types of neurons in the superior colliculus that can be identified by the different types of proteins that are contained in them. One set of neurons contains a protein called parvalbumin (PV). Mixed in with these, are neurons that contain either the protein somatostatin (SST) or vasoactive intestinal peptide (VIP). The researchers found that when they stimulated the PV neurons, the mouse immediately bolted or froze.

To stimulate these neurons selectively, the researchers used genetic manipulation to insert light-sensitive ion channels specifically into the PV neurons. These channels will activate when stimulated by light delivered through a fiber optic cable surgically implanted into the mouse’s brain, thereby causing the PV neurons to fire electrical impulses. When researchers flipped on the fiber optic light, the mouse fled away, and then it cowered after they stopped stimulating the PV neurons. This suggests that the PV neurons are a vital part of a threat detection circuit in the visual pathway. This function of PV neurons was further supported by monitoring the electrical activity in these neurons in anesthetized mice. The researchers found that when a virtual object on a computer screen that resembled a soccer ball came flying directly toward the animal’s head, the PV neurons began firing electrical impulses vigorously. The mouse’s heart rate accelerated and the stress hormone corticosterone increased in the blood stream–the bodily responses we experience as fear in the fight-or-flight reaction. But if the ball moved through the visual field in any other direction except on a collision course, the PV neurons remained silent. The mouse’s heartrate remained calm.

But what determines whether the animal flees or freezes? Interestingly the researchers found that the same neurons controlled both behaviors. Strong stimulation of the PV neurons caused the animal to escape rather than freeze. Either a brighter laser beam, or longer pulses of light, or higher frequency of flashes, would cause the animal to escape rather than freeze.

An interesting observation was that male and female mice responded somewhat differently. Females tended to escape, whereas males tended to freeze–stand their ground, perhaps, in the face of a sudden visual threat that stimulated these PV neurons. Further research will be required to uncover the additional factors that predispose males and females to respond differently to the same visual threat. The researchers then traced the circuit from these neurons and found that they did indeed connect to the amygdala, via a relay neuron in a part of the brain called the PBGN (parabigeminal nucleus). Further analysis showed that PV neurons stimulated neurons to fire by using the excitatory neurotransmitter glutamate. This is unusual because PV neurons elsewhere in the brain use a different neurotransmitter (GABA) to inhibit firing of the neurons they connect to.

This work advances our understanding of how visual threats trigger a fight-or-flight response, but there is much more to be discovered. “What are the functions of the other two pathways?” Peng Cao asks in response to my question about the next step in his research. (He is referring to the function of the SST and VIP neurons in the superior colliculus.)

“Do human beings share a similar pathway with rodents?” He wonders. Cao’s hunch is that these neurons are relevant to fear disorders. “We speculate that this pathway in mice may be genetically defined and subject to environmental modifications.” If humans have the same circuitry from their retina to the amygdala via PV neurons in the superior colliculus, Cao suspects that, “this pathway may be involved in fear disorders such as PTSD.” The amygdala is involved in fear and in learning to avoid dangers, but in addition to this anatomical evidence suggesting that PV neurons may be involved in fear disorders, Cao and his colleagues noticed something interesting. When they stimulated this pathway in the superior colliculus of mice repeatedly, the mice began to show depression and avoidance-like behaviors, much as people do who develop PTSD after surviving an extremely traumatic event.

Note: Readers who are interested in this subject may be interested in my new book Why We Snap, to be published this year by Dutton and available for pre-order now. The unconscious neural circuitry of the fight-or-flight response is involved in many other responses to threats, fear, and when they misfire: snapping in rage.

WWS cover low res

Shang, C., et al., (2015) A parvalbumin-positive excitatory visual pathway to trigger fear responses in mice. Today’s edition of Science, June 26, 2015.

Photo credit:

Posted by: R. Douglas Fields | June 20, 2015

Bruce Jenner and Changing Your Brain’s Sex

Bruce Jenner after his sex change.  Did the treatment affect his brain?

Bruce Jenner after his sex change. Did the treatment affect his brain?

The debut of Bruce Jenner’s sex change on the cover of Vanity Fair was stunning, but superficial. A deeper question than her new-found beauty is: What about her brain?

Just like the anatomy of nearly every other part of the human body, the brains of guys and gals are slightly different. The biggest differences are in the part of the brain controlling automated behaviors and urges–hunger, thirst, sexual behavior and reproductive physiology–the hypothalamus. In fact, one part of the hypothalamus, the preoptic nucleus which is important in sexual reproduction, is twice as big in males as in females. But receptors for sex hormones are found on neurons and glia throughout the adult human brain. It is fascinating to wonder why. But the fact is that cells throughout the brain are acutely keyed into the amount of male and female sex hormones circulating in the body. From this alone it should not be too surprising to learn that sex differences in the brain are hardly limited to the hypothalamus.

His and her differences can be found throughout the brain. Parts of the limbic system, which is involved in arousal and other emotional responses; the basal ganglia, which is part of the brain’s reward system giving us that elated sensation of satisfaction; portions of the prefrontal cerebral cortex, notably the insula, as well as many other brain regions are slightly enlarged in one sex and diminished in the other. Overall, men’s brains have slightly more white matter than women’s, and men’s brains are bigger. So, what happens when a person undergoes a sex change procedure to correct an accident of birth in which a person’s mind is mismatched to the sex of their body?

A study performed in the Netherlands by Hilleke Hulshoff Pol and colleagues used MRI brain imaging to compare the anatomy of the brains of transsexual men and women before and after treatment to reassign their sex. In all, eight men changing their bodies into female, as in Bruce Jenner’s transformation into Caitlyn, and six transgender females becoming male were studied. In addition to surgery, male-to-female transsexuals are treated with “female sex hormones” (estrogens) and blockers of “male sex hormones” (anti-androgens) to suppress the production and physiological effects of androgens. In fact, estrogen and testosterone are normally present in both males and females, but the amount of each hormone differs by sex. Female-to-male transsexuals undergoing sex reassignment are treated with testosterone. The study found that after only four months of hormonal therapy there were widespread changes in the brains of transsexuals that align the brain’s anatomy with their body’s new sex.

The hypothalamus increased in size in transsexual women undergoing reassignment to men, and it shrank in transsexual men undergoing reassignment to women. Most striking was a dramatic decrease in total brain volume in male-to-female subjects. The opposite effect was seen in female-to-male subjects. The change in brain volume was not subtle. Total brain volume decreased by 31 ml (about the size of a shot glass) in male-to-female subjects after only four months of treatment. On the basis of this research one would expect that Jenner’s body would have lost not only muscle, but also lost brain tissue to adapt her body appropriately to the innate differences between sexes in their body and brain.

Appearances can be misleading. Are the anatomical changes taking place in the brains of transsexuals accompanied by functional differences? Another study used functional magnetic resonance imaging (fMRI) to investigate brain activity that was provoked by sexual arousal. In this study, male-to-female transsexuals were shown erotic nude pictures of either male or female bodies after their sex reassignment surgery. Sexual arousal stimulates activity throughout the brain, and the neural circuits that are involved are well documented. As one would expect, these include parts of the limbic system, hypothalamus, and prefrontal cortex. Electrical stimulation of the anterior cingulate gyrus in animal studies, for example, provokes autonomic and endocrine responses, including erection of the penis and secretion of hormones from the gonads. The study on transsexuals found that seeing nude pictures of men activated wide-spread areas of the brain of male-to-female transsexuals. Pictures of nude men caused a surge in brain activity that swept through the cerebellum, hippocampus, the amygdala and other parts of the limbic system, the brain’s reward center (caudate nucleus), and the insula. These changes in brain activity reflect brain function that is associated with sexual arousal being provoked by viewing the male nude body. All of these brain areas cooperate in the powerful sensation of sexual arousal, which involves many components, including cognitive, emotional, motivational, and autonomic physiological processes.

On the other hand, viewing female nudes activated predominantly the hypothalamus and septal areas. The hypothalamus is the most powerful control center of sexual behavior in animals, and the strong activation of the hypothalamus and septal area in male-to-female transsexuals viewing female nudes is perplexing. Other studies show that neither heterosexual individuals viewing videos of the same sex nor homosexual individuals viewing images of the opposite sex show activation of the hypothalamus. Although the reasons are unclear, activation of these areas triggering sexual responses in male-to-female transsexuals when viewing female nude pictures, which is opposite to the sexual orientation of these individuals, suggests that it is overly simplistic to regard transsexuals as homosexuals or heterosexuals who self-identify with the opposite sex.

Will these anatomical and functional changes in the brain of transsexuals also change behavior? In animal studies, it is well established that hormonal treatment alters both the brain and behavior. For example, treating adult female canaries with testosterone triggers changes in brain areas that control singing and this in turn changes the female signing behavior into that of a male canary. In studies of male-to-female transsexuals receiving estrogen treatment and testosterone suppression for three months, there is a measurable decline in anger, aggression, sexual arousal, sexual desire, spatial ability (usually males outperform females), and an increase in verbal fluency (usually females outperform males). The opposite behavioral and cognitive responses were found in female-to-male transsexuals.

Being born into the body of the wrong gender from your mind’s point of view is one of many accidents of birth that modern science can now help to alleviate. As the cover of Vanity Fair shows, the effects of hormonal treatment on the former Olympic gold medalist’s body were profound, but the treatment must also have changed Jenner’s brain. And so it must be. Otherwise, sex reassignment treatment would be a superficial failure.

Pol, H.E.H., et al., (2006) Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure. Europ. J. Endocrinology 155:S107-114.

Oh, S.-K., et al., (2012) Brain activation in response to visually evoked sexual arousal in male-to-female transsexuals: 3.0 Tesla functional magnetic resonance imaging. Korean J. Radiology 13:257-264.

Photo credit: “VanityFairJuly2015” by Source (WP:NFCC#4). Licensed under Fair use via Wikipedia –

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

Watching TV Alters Children’s Brain Structure and Lowers IQ

TV viewing changes brain structure and lowers IQ of children

TV viewing changes brain structure and lowers IQ of children

From the black-and-white days of I Love Lucy to the blue-ray lasers of today’s Game of Thrones in dazzling 3D, parents have worried that television might harm their child’s brain development. Now the answer is plain to see. Brain imaging (MRI) shows anatomical changes inside children’s brains after prolonged TV viewing that would lower verbal IQ.

Neuroscientists in Japan imaged the brains of 290 children between the ages of 5 and 18 years and sorted the data according to how many hours of TV each child had watched. The results showed significant anatomical differences in several brain regions that correlated with the number of hours of TV viewed. These findings were strengthened when the researchers re-examined the same children several years later and were able to see many of these anatomical changes taking place in the children’s brain over time. The more hours of TV children watched, the greater the changes were in brain structure.

The parts of the brain affected are involved in emotional responses, arousal, aggression, and vision. The brain regions that bulked up in children watching more television include gray matter increases in the hypothalamus, septum, sensory motor areas and visual cortex, but also in a frontal lobe region (frontopolar cortex), which is known to lower verbal IQ. Tests confirmed that the children’s verbal IQ had lowered in proportion to the hours of TV watched, ranging from 0 to more than 4 hrs/day. Changes were also observed beneath the cerebral cortex in the brain’s wiring network “white matter regions.” The changes in brain tissue were evident regardless of the sex of the child, age, family income, and many other factors.

The increase in visual cortex is likely caused by exercising vision in TV viewing, but changes in hypothalamus are characteristic of patients with borderline personality disorder, increased aggressiveness and mood disorders. The frontopolar region is active in monitoring and regulating internal mental states, and enlargements in frontopolar cortex are known to be associated with lower verbal IQ. Several previous studies have found lower verbal IQ and increased aggressiveness in proportion to the amount of television children watch. This new research uncovers the biological mechanism for these changes in behavior and drop in intelligence.

The brain alterations could be caused directly by TV viewing, or indirectly by the different life experiences gained through physical and virtual activities while the young brain is maturing. The more time spent sitting on the couch, the less time spent in physical activity, reading, and interacting with friends. Consider that children who watch 4 or more hours of TV a day, spend more than half of their free time watching the tube, assuming they devote 8 hrs for sleep and 8 hours for school. “Guardians of children should consider these effects when children view TV for long periods of time,” the researchers conclude.

Takeuchi, H., et al., The impact of television viewing on brain structures: Cross-sectional and longitudinal analyses. Cerebral Cortex, May, 2015; 25: 1188-1197.

Posted by: R. Douglas Fields | May 2, 2015

Heisenberg Uncertainty and the Baltimore Riots


Yesterday I encountered a colleague outside the elevator. He was profoundly troubled, as are many, anguished by the violence in Baltimore this week. The looting, burning, and scores of injured from angry youths hurling bricks at police were sparked by the violent death of a black man, Freddie Gray, in police custody.

“I was there yesterday,” I told my concerned colleague.

“What? Where?”

“I went to the CVS Drugstore that was looted and burned,” I replied.

In disbelief he asked, “What was it like?”

“I was too late. All of the DVR’s and other good stuff were already gone,” I said.

My reply can be taken as a crass, inappropriate outburst of dark humor, but there is a deeper message. It is a message that every scientist knows well and grapples with every day–the Heisenberg uncertainty principle. Fundamentally, reporters and scientists are driven by the same passion. Both are engaged in the challenging process of trying to find truth from primary evidence. Thus science and reporting, subject to the same types of errors, sometimes fail for similar reasons.

The facts are that a young black man died a violent cruel death while in police custody. His spine was snapped. He was restrained by handcuffs and leg irons and mortally injured while being transported inside a police wagon in the custody of six police officers. Angry riots erupted in rage against police brutality.

We watched it all live on TV. Hordes of angry black men armed with clubs and stones, facing off against a phalanx of police in black riot gear, wearing modern armor, helmets and shields that harken back to medieval battles between knights of the kingdom and oppressed peasants. We have seen this angry scene thousands of times through thousands of years of human history. As the city of Baltimore burned those of us who remember the horror of the summer of violence that plunged the country into chaos in 1968, were sickened.

“Can’t we all get along?” Rodney King pleaded during riots in Los Angeles in 1992. The black taxi driver was brutally beaten by Los Angeles Police officers after a high-speed chase in 1991. That beating by police was videotaped by a citizen appalled by the brutality erupting on the street beneath his balcony. After a trial that acquitted the police of serious charges, Los Angeles was consumed by riots in which 53 people were killed, 2000 were injured, and the neighborhoods were looted and burned. The military was dispatched to restore order, but many neighborhoods never fully recovered and the violence spread to other cities.

Rodney King’s plea echoed the bewilderment of everyone, and unfortunately the answer to his vexing question cannot be more obvious or more disheartening. Such turmoil and brutality are a deadly consequence of the human mind that within milliseconds of observing another person categorizes the individual into either “us or them.” It happens as quickly and as automatically as the brain attaches the color red or green to an apple. Paradoxically, those automated brain circuits are the essence of human success. They enabled our species to coalesce spontaneously into groups for mutual protection and common purpose, and often to do so through violence. This is the double-edged sword of the human brain. There can be no patriotism without a foreign adversary; no maternal bonding without seeing other babies differently.

The heavy thumping of helicopter blades circling overhead, the smell of charred wood, sirens squealing from every direction, echoing hysterically through the alleyways and streets it is impossible for me to tell where they originate. In a flash a fire truck, police car, or ambulance streaks past, ablaze with flashing red lights, racing toward the violence or away from it to hospitals or police stations.

Stepping into the neighborhood surrounding the CVS drugstore triggers screeching alarms in your brain that raise hair on the back of your neck and make your spine shiver. Groups of men loiter on street corners, drinking oversized cans of malt liquor from rumpled paper bags and smoking. Others pass the day sitting on the stoops of red brick row houses as if discarded. The windows of buildings are boarded with plywood weathered into a furry gray, warped and pealing, the homes and businesses have been abandoned for ages. It is a neighborhood of pawn shops, discount liquor stores, mom and pop corner markets with bars on the doors and windows, of bail bonds and check cashing establishments. Faded tent cities rot under an overpass, cluttered with shopping carts and scavenged junk. It is a perilous place of danger, crime, and drugs. 25 percent of the men are unemployed. They have nothing to do. Nowhere to go. Trapped, they have no way out. Children grow up in squalor and poverty.

All eyes follow me. They are the eyes of black men. I am white. There is not a thing in the world that either of us can do about that. Ours is the biological legacy of genetics; mine following a line of descent from northern Europe, theirs from Africa. It shouldn’t make much difference, but it does.

The violence, though, is not exactly the result of racism; it is the result of tribalism, a human trait that divides the world into us vs them. I suspected as much when I visited the boarded up drugstore, but today we learned that three of the six police officers charged with assaulting Freddie Gray are black. The driver of the police wagon now facing murder charges was a black officer. An unfortunate result of tribalism can be festering pockets of poverty, neglect, hopelessness, divisions between the haves and the have not’s, and instantaneous violence unleashed by brain circuits designed for herding, defense, and mutual cooperation in groups.

But this is not what I wish to explore in this article, which is targeted to those with an interest in science. As we watched the looting streamed live into our homes on TV, what we did not see was the view from the opposite direction. When I visited the burned and boarded up CVS store this week, in the midst of the protests and before the police were charged with the crime, I saw the streets lined with TV vans, satellite dishes, cameramen, soundmen, reporters interviewing men in suits and residents gathered around ogling and curious. Reporters, some of them from foreign countries, positioned carefully so that the camera angle would capture the person being interviewed with a snippet of boarded storefront in frame as the backdrop, carefully avoiding the throngs of other reporters and gawkers loitering around.

A good example is the large photograph on the front page of today’s Washington Post (May 2, 2015). It shows a black woman with orange blond hair standing up through the moon roof of her vehicle jubilantly cheering with her arms outstretched in the air. In her hand, partially cropped from the frame she holds not stones, but rather a cell phone. She is surrounded by others mugging for the camera. I was at that same spot on Wednesday. Look past her and you see not a crowd, but rather people milling about, eyes fixed on their cell phones, and two other cameramen caught in the frame trying to snap the same image that would carry the day’s narrative.

People do not behave the same in private and in public. If a reporter does not block them off, people will jump into the scene and clown for the camera. Morning news shows exploit this human phenomenon by shooting live weather reports on the streets outside the TV studio in Manhattan so people will mug for the camera and liven up the otherwise boring announcement of temperature and rain fall.

What effect did the media circus have on the youths watching the looting of stores or of protestors assembling, or of youthful gangs collecting into peer groups intent on confrontation with police? The situation sets up a sort of street theater in which people assume roles and act out in the way they see others doing or in the way that aligns them with others to which they aspire to be. The act of trying to capture the events runs the risk of altering them–the Heisenberg uncertainty principle.

Freedom of the press is essential. It is the only real means to find truth in public affairs. It is the only way to shed light on shady dealings, and to counter the inevitable corruption and abuses of power that otherwise overtake government and industry. Without the videos broadcast by the media of Rodney King being beaten and of the violent protests this week in Baltimore, there is no question that injustice and abuse of power would have gone unchecked. But the same conundrum that perplexes scientists applies to reporters.

Heisenberg’s principle cannot be overcome. It can only be recognized. The laser scanning confocal microscope in my laboratory has revealed wonderful insights for me into how living brain cells operate and communicate, but I know and must always be mindful of the fact that the laser beam that illuminates the cell is also stimulating it and changing it. The light illuminating the cell also heats it, blanches it, drives chemical reactions that generate toxic products, and so do the lights of TV cameras on a crowd.

Posted by: R. Douglas Fields | April 26, 2015

The Kathmandu earthquake will alter brain structure of survivors

Brain structure was altered in survivors of Wenchuan earthquake

Brain structure was altered in survivors of Wenchuan earthquake

The disastrous earthquake in Kathmandu has killed hundreds of people and brought grievous tragedy to thousands. Even among the survivors, the earthquake will leave its mark in the form of altered brain structure, according to neuroimaging research performed on survivors of the Wenchuan earthquake of 2008.

Studies by Lui and colleagues on survivors of the 2008 Wenchuan earthquake in China report changes in brain structure that can be seen by MRI. The 7.9 magnitude Wenchuan earthquake (also called Sichuan earthquake) rocked the mountainous central region of Sichuan province in southwestern China on May 12, 2008. 90,000 people died. 375,000 people were injured. Millions of people were rendered homeless.

A 2013 study was performed on 44 survivors, male and female, 25 days after the earthquake and compared to 38 matched controls who had their brains scanned for other reasons prior to the earthquake. The results showed a decrease in gray matter in the insula, hippocampus, and caudate, and an increase in the orpitofrontal cortex (OFC) and parietal cortex.

The OFC is important in modulating emotional responses in the hippocampus, amygdala, ventral striatum and insula. The increase in gray matter is consistent with elevated demands for top-down (that is executive functioning of the cerebral cortex) regulation of threat, fear, and stress circuitry in the limbic system. The increase in parietal cortex has been reported previously in other types of trauma survivors, and this may reflect enhanced neural activity related to the hyper-vigilant state.

The authors suggest that the lower grey matter volume in the insula, striatum, and hippocampus may result from decreased neurogenesis and increased synapse elimination that are seen in studies of experimental animals subjected to chronically elevated stress hormone levels. Acute stress elevates corticotropin-releasing hormone to activate the hypothalamic-pituitary-adrenal axis that is engaged in the “fight-or-flight” response, but prolonged elevation of this stress response is damaging to the brain and body in many respects.

Scientific data on the effects of stress on the human brain are difficult to obtain for ethical reasons, and extrapolating complex cognitive processes of human stresses from animal research is problematic. Studies of people who have survived natural disasters or traumatic events can provide important insights into the effect of stress on human brain structure.

Similar brain changes have been observed in people who have experienced other major life stresses. Studies have reported altered brain structure in patients with PTSD involving regions that function in threat detection and fear, notably the amygdala, hippocampus, and prefrontal cortex (anterior cingulate and medial frontal gyrus). The altered gray matter volume in the prefrontal to limbic and striatal systems found in earthquake survivors are recognized to be involved in emotional and conscious decision making. The striatum and parietal regions are activated in making decisions under time pressure. These regions also undergo changes in people with anxiety disorders, and these brain regions are engaged when processing fear and pain.

The authors conclude that survivors of severe emotional trauma may experience substantial change in brain function and also in the structural anatomy of the prefrontal-limbic, parietal and striatal brain system. These changes are not necessarily pathological. Rather they reflect in part the brain’s remarkable capacity to modify its structure and function rapidly in response to environmental experience. The changes found in earthquake survivor’s brains likely increase the ability of survivors to respond rapidly and appropriately to the danger and trauma. However, if these brain modifications do not return to normal after the threat has passed, this can result in dysfunction. This is well demonstrated by brave military men and women who suffer post-traumatic stress disorder after returning to a safe environment. Similar changes in the brains of people under stress that helped them survive in combat, can become debilitating after returning to civilian life.

Cohen, R.A. et al., (2006) Early life stress and morphometry of the adult anterior cingulate cortex and caudate nuclei. Biol. Psychiatry 59: 975-82.
Davidson, R.J. (2000) Dysfunction in the neural circuitry of emotion regulation — a possible prelude to violence. Science 289: 591.
Lui, S. (2009) High-field MRI reveals an acute impact on brain function in survivors of the magnitude 8.0 earthquake in China. Proc. Natl. Acad. Sci. USA 106; 15412-7.
Lui, S., et al., Bran structural plasticity in survivors of a major earthquake. J Psychiatry Neurosci. 2013 Nov;38(6):381-7
McEwen, B.S. (2007) Physiology and neurobiology of stress and adaptation: central role of the brain. Physiol. Rev. 87:873-904.

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

Snakes on the Brain

Pit vipers have infrared vision.  (Photo by author.)

Pit vipers have infrared vision. (Photo by author.)

After repeated encounters with a friendly rattlesnake last week I have snakes on the brain. Serpents are a storehouse of fascinating neuroscience. Infrared vision, venom, fast-twitch muscles to energize its “warning buzzer,” and more…

The western diamondback rattlesnake can rattle its tail at frequencies of 90 Hz and do this continuously for hours. This is about the frequency of sound handled by the subwoofer in your fancy home theater system. Even a piano virtuoso can’t begin to approach this feat of turbocharged muscle contraction executed with ease by the lowly cold-blooded viper. Try it. You’ll find you can tap your finger at a feeble maximum rate of about five taps/sec (5 Hz), and you’ll quickly poop out.

Hi speed rattling

High speed rattling

You may not know that the simple test of finger tapping rate provides revealing insight into your brain function. The maximum rate of finger tapping correlates with IQ. The finger tapping rate also declines with age in parallel with cognitive decline. So how does the rattler shake its tail into a fuzzy blur, you, and envious surf rock guitarist Dick Dale, might ask?

Dick Dale

Dick Dale

The tailshaker muscle is absolutely packed with energy producing mitochondria. This enables the tailshaker muscle to use oxygen at a much faster rate than muscles of other warm or cold-blooded animals. Hummingbirds have shared this design principle to flutter their wings so fast they can hover in place.

Infrared night-vision cameras are the ultimate imaging technological that can peer through walls and see clearly in complete darkness. Recall the ghostly glowing image of the Boston Bomber hidden inside the fiberglass boat shot from a police helicopter’s infrared camera as the SWAT team closed in? Cool technology, but snakes have had this stealthy equipment for eons.

Boston Bomber seen by infrared camera

Boston Bomber seen by infrared camera

Have a look at the lovely face of the rattler who greeted us repeatedly last week in the backcountry of Nevada. Notice those tiny openings below the eyes? Snakes do have nostrils, but snakes “smell” with their tongues (that’s another story). They flick their tongue in the direction of a warm blooded prey item just before striking–something I observed, but my trigger finger was too slow to catch it on camera. The second set of pits on the reptile’s face are unique sense organs that give pit vipers infrared vision and also give them their name “pit vipers.”

In 1937 Noble and Schmidt put blindfolds on rattlesnakes and found that the blindfolded snakes could magically strike at moving objects very accurately, such as a dead rat or a cloth-wrapped light bulb. Moreover, the snakes had the ability to distinguish between identical warm and cold objects. In 1952, Bullock and Cowles took an electrophysiological approach to understand the function of these pits and uncover how they worked. The scientists surgically exposed the superficial branch of the superior maxillary division of the trigeminal nerve that connects the pit organs to the brain. They suspended the slender nerve on a pair of wire electrodes that were connected to an electronic amplifier powering a loudspeaker. (Try that sometime. I’m leaving out some thrilling procedural details.) What they heard on the loud speaker was a constant barrage of nerve impulses shooting from the sense organ to the brain. The researchers found that when a warm or cold object was held in front of the snake’s face, the firing rate of nerve impulses either suddenly increased or decreased depending on whether the object was slightly warmer or colder than room temperature. An ice cube, for example, held in front of the snake caused the firing rate to instantaneously slow–within 50 ms (5/100s of a second). This response was much too fast to be explained by actual heating or cooling of tissue in the snake’s sense organ. They concluded that these sense organs had to be detecting infrared radiation emitted by warm objects– but how?

(I am fortunate to have had Ted Bullock as one of my mentors when I was a graduate student. His stories of delivery men and secretaries unwittingly walking into the lab and being perplexed by the sudden cacophony of buzzing surrounding them, emanating from burlap bags suspended from the ceiling, are precious. “Rattlesnakes,” he would explain offhandedly to the wide-eyed visitors who immediately departed, propelled by a jolting primal response embedded in the amygdala of human brains by evolution.)

It is difficult to imagine a sensory ability that we humans do not have, but these pit organs likely give the viper a visual sense. The neural pathways from the pit organs connect to the same brain structure as pathways from the snake’s eyes, the optic tectum. Behavioral studies by Bakken and Krochmal in 2007 indicate that the pit organ must be able to respond to temperature changes as minute as 0.001 degree C or less! This is sensitive enough to provide a detailed gray-scale image of objects from the emitted infrared radiation.

In 2002 Terashima and Ogawa reported that capsaicin, the fiery ingredient in hot peppers, caused the nerve terminals in the infrared receptors of snakes to degenerate. This is a clue that the molecular mechanism of detecting warmth somehow shares affinity with how we sense the burn of hot sauce. Indeed, in 2010, Grachevia et al., reported that the molecular basis of infrared detection by pit vipers was provided by an ion channel TRPA1 (transient receptor potential channels). This is a member of a large family of ion channels that give our own heat-sensing neurons the ability to respond to temperature changes and also give us the painful sensation of heat from hot sauce. The researchers discovered this by analyzing the genes expressed in sensory cells in the pit organs. There are many members of the TRP channel family, but more recent studies show that the same TRPA1 ion channel operates as a thermoreceptor in a wide range of animals from mosquitos to rats.

Countermeasures to heat seeking missiles--not news to squirrels

Countermeasures to heat seeking missiles–not news to squirrels

Fighter jets use thermal decoys to confuse heat seeking missiles, but ground squirrels have been using the same cleaver decoy against their venomous predators long before the DoD stumbled upon the same countermeasure. Rundus et al, found that California ground squirrels add an infrared component to their shaking tail when confronted by infrared-sensitive rattlesnakes, but squirrels don’t emit strong infrared signals from their wagging tails when confronted by gopher snakes, which lack the infrared receptors. Using a robotic squirrel to test the rattle snake’s response, the researchers found that when an infrared component was added to the flagging robotic tail, the rattlesnakes shifted from predatory to defensive behavior. This did not happen when the tail was flagged without the added infrared component. That behavior provoked the snake to strike.

Infrared emissions from squirrel tail only when encountering pit vipers, a countermeasure to rattlesnake infrared imaging.  PNAS 2007 104:14382-6.  Fig. 2.

Infrared emissions from squirrel tail only when encountering pit vipers, a countermeasure to rattlesnake infrared imaging. PNAS 2007 104:14382-6. Fig. 2.

Gees, already 1000 words and I’ve hardly gotten started. This story will have to be continued as a sequel–“Snakes on the Brain, Part II.”

Bonus Question: Can someone tell me what species of rattler it is in the photo above?


Bakkens, G.S. and Krochmal, A.R. (2007) The imaging properties and sensitivity of the facial pits of pitvipers as determined by optical and heat-transfer analysis. J. Exp. Biol. 210: 2801-10.

Bullock, T.H. and Cowles, R.B. (1952) Physiology of an infrared receptor: The facial pit of pit vipers.

Gracheva E.O., et al., (2010) Molecular basis of infrared detection by snakes. Nature 464: 1006-11.

Nobel, G.K., and Schmidt, A. (1937) Physiology of an infrared receptor: The facial pit of pit vipers. Proc. Am. Phil. Soc. 77: 263.

Rundus, A.S. et al., (2007) Ground squirrels use an infrared signal to deter rattlesnake predation. Proc. Natl. Acad. Sci. USA 104:14372-6.

Schaeffer, P., et al., (1996) Structural correlates of speed and endurance in skeletal muscle: the rattlesnake tailshaker muscle. J. Exp. Biol. 199: 351-8.

Terashima, S. and Ogawa, K., (2002) Degeneration of infrared receptor terminals of snakes caused by capsaicin. Brain Res. 958: 468-71.

Tomoko Aoki, Yoshiyuki Fukuoka (2010) Finger Tapping Ability in Healthy Elderly and Young Adults. Med Sci Sports Exerc. 2010;42(3):449-455

Warner MH, et al., (1987) Relationships between IQ and neuropsychological measures in neuropsychiatric populations: within-laboratory and cross-cultural replications using WAIS and WAIS-R. Clin Exp Neuropsychol. 1987 Oct;9(5):545-62.

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.

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