No Picky Eaters Among Successful Argentine Ants

No Picky Eaters Among Successful Argentine Ants

 
The Argentine ant, which invades and displaces local ant species, has been shown to have a flexible diet.

The Argentine ant is a very successful invasive species, having conquered territories far from its native South America. Once introduced, inadvertently, by people, it marches across the landscape, displacing local ant species and making an agricultural pest of itself.

Researchers from the University of Illinois and the University of California at San Diego have uncovered one secret to the ant’s success: dietary flexibility. The insects can live high on the hog, but will eat at lower levels of the food chain if they have to.

Chadwick V. Tillberg and colleagues studied an invasion of ants across a canyon in Chula Vista, Calif., over eight years. They collected ants at various sites and analyzed the ratio of stable nitrogen isotopes in the insects, an indication of what they were eating.

As the researchers report in The Proceedings of the National Academy of Sciences, ants right at the invasion front showed higher levels of nitrogen-15, suggesting they were consuming native ants and other insects. But as the front moved on, nitrogen-15 levels declined, with the ants switching to food from plants, particularly the honeydew produced by aphids.

The researchers also compared isotope levels between ants in California and in their native range in Argentina. They found that the native ants ate higher on the food chain.

Taken together, the researchers say, the findings support the idea that a flexible diet makes for a successful invasion. What’s unclear is precisely why the dietary switch occurs. It may be forced upon the ants once they’ve munched through the other ant species in their territory. Or it may simply be that Southern California, with its citrus industry, has so many honeydew-producing aphids around for the ants to exploit.

Noble or savage?

Noble or savage?

The era of the hunter-gatherer was not the social and environmental Eden that some suggest

HUMAN beings have spent most of their time on the planet as hunter-gatherers. From at least 85,000 years ago to the birth of agriculture around 73,000 years later, they combined hunted meat with gathered veg. Some people, such as those on North Sentinel Island in the Andaman Sea, still do. The Sentinelese are the only hunter-gatherers who still resist contact with the outside world. Fine-looking specimens—strong, slim, fit, black and stark naked except for a small plant-fibre belt round the waist—they are the very model of the noble savage. Genetics suggests that indigenous Andaman islanders have been isolated since the very first expansion out of Africa more than 60,000 years ago.

About 12,000 years ago people embarked on an experiment called agriculture and some say that they, and their planet, have never recovered. Farming brought a population explosion, protein and vitamin deficiency, new diseases and deforestation. Human height actually shrank by nearly six inches after the first adoption of crops in the Near East. So was agriculture “the worst mistake in the history of the human race”, as Jared Diamond, evolutionary biologist and professor of geography at the University of California, Los Angeles, once called it? 

Take a snapshot of the old world 15,000 years ago. Except for bits of Siberia, it was full of a new and clever kind of people who had originated in Africa and had colonised first their own continent, then Asia, Australia and Europe, and were on the brink of populating the Americas. They had spear throwers, boats, needles, adzes, nets. They painted pictures, decorated their bodies and believed in spirits. They traded foods, shells, raw materials and ideas. They sang songs, told stories and prepared herbal medicines.

They were “hunter-gatherers”. On the whole the men hunted and the women gathered: a sexual division of labour is still universal among non-farming people and was probably not shared by their Homo erectus predecessors. This enabled them to eat both meat and veg, a clever trick because it combines quality with reliability.

Why change? In the late 1970s Mark Cohen, an archaeologist, first suggested that agriculture was born of desperation, rather than inspiration. Evidence from the Fertile Crescent seems to support him. Rising human population density, combined perhaps with a cooling, drying climate, left the Natufian hunter-gatherers of the region short of acorns, gazelles and wild grass seeds. Somebody started trying to preserve and enhance a field of chickpeas or wheat-grass and soon planting, weeding, reaping and threshing were born.

Quite independently, people took the same step in at least six other parts of the world over the next few thousand years: the Yangzi valley, the central valley of New Guinea, Mexico, the Andes, West Africa and the Amazon basin. And it seems that Eden came to an end. Not only had hunter-gatherers enjoyed plenty of protein, not much fat and ample vitamins in their diet, but it also seems they did not have to work very hard. The Hadza of Tanzania “work” about 14 hours a week, the !Kung of Botswana not much more.

The first farmers were less healthy than the hunter-gatherers had been in their heyday. Aside from their shorter stature, they had more skeletal wear and tear from the hard work, their teeth rotted more, they were short of protein and vitamins and they caught diseases from domesticated animals: measles from cattle, flu from ducks, plague from rats and worms from using their own excrement as fertiliser.

They also got a bad attack of inequality for the first time. Hunter-gatherers' dependence on sharing each other's hunting and gathering luck makes them remarkably egalitarian. A successful farmer, however, can afford to buy the labour of others, and that makes him more successful still, until eventually—especially in an irrigated river valley, where he controls the water—he can become an emperor imposing his despotic whim upon subjects. Friedrich Engels was probably right to identify agriculture with a loss of political innocence.

Agriculture also stands accused of exacerbating sexual inequality. In many peasant farming communities, men make women do much of the hard work. Among hunter-gathering folk, men usually bring fewer calories than women, and have a tiresome tendency to prefer catching big and infrequent prey so they can show off, rather than small and frequent catches that do not rot before they are eaten. But the men do at least contribute.

Recently, though, anthropologists have subtly revised the view that the invention of agriculture was a fall from grace. They have found the serpent in hunter-gatherer Eden, the savage in the noble savage. Maybe it was not an 80,000-year camping holiday after all.

In 2006 two Indian fishermen, in a drunken sleep aboard their little boat, drifted over the reef and fetched up on the shore of North Sentinel Island. They were promptly killed by the inhabitants. Their bodies are still there: the helicopter that went to collect them was driven away by a hail of arrows and spears. The Sentinelese do not welcome trespassers. Only very occasionally have they been lured down to the beach of their tiny island home by gifts of coconuts and only once or twice have they taken these gifts without sending a shower of arrows in return.

Several archaeologists and anthropologists now argue that violence was much more pervasive in hunter-gatherer society than in more recent eras. From the
!Kung in the Kalahari to the Inuit in the Arctic and the aborigines in Australia, two-thirds of modern hunter-gatherers are in a state of almost constant tribal warfare, and nearly 90% go to war at least once a year. War is a big word for dawn raids, skirmishes and lots of posturing, but death rates are high—usually around 25-30% of adult males die from homicide. The warfare death rate of 0.5% of the population per year that Lawrence Keeley of the University of Illinois calculates as typical of hunter-gatherer societies would equate to 2 billion people dying during the 20th century.

At first, anthropologists were inclined to think this a modern pathology. But it is increasingly looking as if it is the natural state. Richard Wrangham of Harvard University says that chimpanzees and human beings are the only animals in which males engage in co-operative and systematic homicidal raids. The death rate is similar in the two species. Steven LeBlanc, also of Harvard, says Rousseauian wishful thinking has led academics to overlook evidence of constant violence.

I know it's a drag Godric, but it's progress

Not so many women as men die in warfare, it is true. But that is because they are often the object of the fighting. To be abducted as a sexual prize was almost certainly a common female fate in hunter-gatherer society. Forget the Garden of Eden; think Mad Max.

Constant warfare was necessary to keep population density down to one person per square mile. Farmers can live at 100 times that density. Hunter-gatherers may have been so lithe and healthy because the weak were dead. The invention of agriculture and the advent of settled society merely swapped high mortality for high morbidity, allowing people some relief from chronic warfare so they could at least grind out an existence, rather than being ground out of existence altogether.

Notice a close parallel with the industrial revolution. When rural peasants swapped their hovels for the textile mills of Lancashire, did it feel like an improvement? The Dickensian view is that factories replaced a rural idyll with urban misery, poverty, pollution and illness. Factories were indeed miserable and the urban poor were overworked and underfed. But they had flocked to take the jobs in factories often to get away from the cold, muddy, starving rural hell of their birth.

Homo sapiens wrought havoc on many ecosystems as Homo erectus had not

Eighteenth-century rural England was a place where people starved each spring as the winter stores ran out, where in bad years and poor districts long hours of agricultural labour—if it could be got—barely paid enough to keep body and soul together, and a place where the “putting-out” system of textile manufacture at home drove workers harder for lower pay than even the factories would. (Ask Zambians today why they take ill-paid jobs in Chinese-managed mines, or Vietnamese why they sew shirts in multinational-owned factories.) The industrial revolution caused a population explosion because it enabled more babies to survive—malnourished, perhaps, but at least alive.

Returning to hunter-gatherers, Mr LeBlanc argues (in his book “Constant Battles”) that all was not well in ecological terms, either. Homo sapiens wrought havoc on many ecosystems as Homo erectus had not. There is no longer much doubt that people were the cause of the extinction of the megafauna in North America 11,000 years ago and Australia 30,000 years before that. The mammoths and giant kangaroos never stood a chance against co-ordinated ambush with stone-tipped spears and relentless pursuit by endurance runners.

This was also true in Eurasia. The earliest of the great cave painters, working at Chauvet in southern France, 32,000 years ago, was obsessed with rhinoceroses. A later artist, working at Lascaux 15,000 years later, depicted mostly bison, bulls and horses—rhinoceroses must have been driven close to extinction by then. At first, modern human beings around the Mediterranean relied almost entirely on large mammals for meat. They ate small game only if it was slow moving—tortoises and limpets were popular. Then, gradually and inexorably, starting in the Middle East, they switched their attention to smaller animals, and especially to warm-blooded, fast-breeding species, such as rabbits, hares, partridges and smaller gazelles. The archaeological record tells this same story at sites in Israel, Turkey and Italy.

Another fine environmental mess we've got ourselves into

The reason for this shift, say Mary Stiner and Steven Kuhn of the University of Arizona, was that human population densities were growing too high for the slower-reproducing prey such as tortoises, horses and rhinos. Only the fast-breeding rabbits, hares and partridges, and for a while gazelles, could cope with such hunting pressure. This trend accelerated about 15,000 years ago as large game and tortoises disappeared from the Mediterranean diet altogether—driven to the brink of extinction by human predation.

In times of prey scarcity, Homo erectus, like other predators, had simply suffered local extinction; these new people could innovate their way out of trouble—they could shift their niche. In response to demographic pressure, they developed better weapons which enabled them to catch smaller, faster prey, which in turn enabled them to survive at high densities, though at the expense of extinguishing many larger and slower-breeding prey. Under this theory, the atlatl or spear-throwing stick was invented 18,000 years ago as a response to a Malthusian crisis, not just because it seemed like a good idea.

Soon collecting wild grass seeds evolved into planting and reaping crops, which meant fewer proteins and vitamins but ample calories

What's more, the famously “affluent society” of hunter-gatherers, with plenty of time to gossip by the fire between hunts and gathers, turns out to be a bit of a myth, or at least an artefact of modern life. The measurements of time spent getting food by the !Kung omitted food-processing time and travel time, partly because the anthropologists gave their subjects lifts in their vehicles and lent them metal knives to process food.

Agriculture was presumably just another response to demographic pressure. A new threat of starvation—probably during the millennium-long dry, cold “snap” known as the Younger Dryas about 13,000 years ago—prompted some hunter-gatherers in the Levant to turn much more vegetarian. Soon collecting wild grass seeds evolved into planting and reaping crops, which reduced people's intake of proteins and vitamins, but brought ample calories, survival and fertility.

The fact that something similar happened six more times in human history over the next few thousand years—in Asia, New Guinea, at least three places in the Americas and one in Africa—supports the notion of invention as a response to demographic pressure. In each case the early farmers, though they might be short, sick and subjugated, could at least survive and breed, enabling them eventually to overwhelm the remaining hunter-gatherers of their respective continents.

It is irrelevant to ask whether we would have been better off to stay as hunter-gatherers. Being a niche-shifting species, we could not help moving on. Willingly or not, humanity had embarked 50,000 years ago on the road called “progress” with constant change in habits driven by invention mothered by necessity. Even 40,000 years ago, technology and lifestyle were in a state of continuous change, especially in western Eurasia. By 34,000 years ago people were making bone points for spears, and by 26,000 years ago they were making needles. Harpoons and other fishing tackle appear at 18,000 years ago, as do bone spear throwers, or atlatls. String was almost certainly in use then—how do you catch rabbits except in nets and snares?

Nor was this virtuosity confined to practicalities. A horse, carved from mammoth-ivory and worn smooth by being used as a pendant, dates from 32,000 years ago in Germany. By the time of Sungir, an open-air settlement from 28,000 years ago at a spot near the city of Vladimir, north-east of Moscow, people were being buried with thousands of laboriously carved ivory beads and even little wheel-shaped bone ornaments.

Incessant innovation is a characteristic of human beings. Agriculture, the domestication of animals and plants, must be seen in the context of this progressive change. It was just another step: hunter-gatherers may have been using fire to encourage the growth of root plants in southern Africa 80,000 years ago. At 15,000 years ago people first domesticated another species—the wolf (though it was probably the wolves that took the initiative). After 12,000 years ago came crops. The internet and the mobile phone were in some vague sense almost predestined 50,000 years ago to appear eventually.

There is a modern moral in this story. We have been creating ecological crises for ourselves and our habitats for tens of thousands of years. We have been solving them, too. Pessimists will point out that each solution only brings us face to face with the next crisis, optimists that no crisis has proved insoluble yet. Just as we rebounded from the extinction of the megafauna and became even more numerous by eating first rabbits then grass seeds, so in the early 20th century we faced starvation for lack of fertiliser when the population was a billion people, but can now look forward with confidence to feeding 10 billion on less land using synthetic nitrogen, genetically high-yield crops and tractors. When we eventually reverse the build-up in carbon dioxide, there will be another issue waiting for us.

 

Jets Spiral in 'Reverse Whirlpool' from Star

Jets Spiral in 'Reverse Whirlpool' from Star

 
This artist's concept shows the protostar HH 211, as it accretes material from a surrounding disk. Some of the material from the disk is ejected outward in a bipolar jet. The matter in the jet rotates around the jet's axis, carrying away angular momentum so the star can grow.

Astronomers have observed for the first time a jet of matter spiraling outward from an infant star, as if a lengthy strand of curly pasta.

The enormous jet, which shoots out in two directions, is rocketing material away from the so-called protostar and into interstellar space at more than "supersonic speeds." From end to end, the bipolar jet extends 16,000 astronomical units (AU), where 1 AU is the average distance between the Earth and sun.

Called Herbig-Haro (HH) 211, the protostar is located about 1,000 light-years away in the constellation Perseus. Scientists have estimated HH 211 started gathering stellar material about 20,000 or so years ago.

"It's like an infant compared to the sun," said astronomer Qizhou Zhang of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "Ultimately this object we observed will grow into a star like the sun, but right now it's only 6 percent of the mass of the sun."

The finding, detailed in the Dec. 1 issue of the Astrophysical Journal, confirms a key step of star formation, one that astronomers have suspected since the 1980s.

Stellar birth

Stars are thought to form at the center of rotating disks of hydrogen gas and dust. Over time, protostars pack on material from spinning disks, meanwhile getting hotter and hotter, until they begin nuclear fusion. This hydrogen-burning process keeps full-blown stars aglow.

However, there's a stellar glitch of sorts. Similar to dizzying rides that rotate so swiftly riders stick to the outer walls, as a disk rotates faster and faster, the swirling matter sticks to the disk's outer edge. The gas can't fall inward toward the star until it sheds excess spin power called angular momentum.

"It has to get rid of the spin energy otherwise the matter will just keep swirling around in this disk around the star without actually going into the star," Zhang told SPACE.com.

Reverse whirlpool

Theory suggests nascent stars could shed excess angular momentum in the form of gas spiraling outward around shooting jets. Zhang and his colleagues glimpsed such spiraling gas using the Submillimeter Array (SMA), which consists of eight radio telescopes located atop Mauna Kea in Hawaii.

Measurements showed matter rotating around the jet's axis in a sort of "reverse whirlpool." The results suggest the bipolar jet moves outward at a speed greater than 200,000 mph (322,000 kph), while matter swirls around the jet's major axis at more than 3,000 mph (4,828 kph).

"HH 211 essentially is a 'reverse whirlpool,'" Zhang explained. "Instead of water swirling around and down into a drain, we see gas swirling around and outward."

Flirting 101, for Fiddler Crabs

Flirting 101, for Fiddler Crabs

Yoo-Hoo!
A male fiddler crab issues a grand, "yoo-hoo" type wave by stretching his large claw to the side, slowly lifting it high above his body and then dropping it back down to the resting position. Observations and experiments conducted on a population of mud flat-dwelling fiddler crabs at Bowling Green Bay in Queensland, Australia, revealed the males didn't stretch out their claws as much when the females were nearby.

When Elvis shook his hips, girls went wild, and so it is that the sight of a male

fiddler crab waving its single giant claw can send female crabs into a sexy swoon, according to a new study.

The study is one of the first to show that receiver distance affects visual signals in non-human animals: the males wave differently, depending on how close or how far away the female onlooker is.

People do this all of the time, such as when someone is trying to catch the attention of a loved one at an airport and jumps up and down while waving to do so. If the intended recipient of the signal is nearby, the person jumping up and down and waving would waste energy and look rather stupid.

Crabs too change their tactics, which also alters the meaning of the signals.

"I think that the long-range claw-waving signal is essentially saying, 'I'm a male Uca perplexa and I'm over here!,'" said Martin How, lead author of the study. "It acts as a beacon towards which receptive females can move."

How, a researcher in the Center for Visual Sciences at The Australian National University in Canberra, thinks the short-range claw waving display is different.

"In this case, the information of the signal changes, and probably says something along the lines of, 'I'm a big healthy crab with a nice burrow to raise a brood and would make an ideal mate!'" How told Discovery News.

He explained that the yoo-hoo type wave happens when the male stretches his large claw to the side, slowly lifts it high above his body and then drops it back to the resting position. Observations and experiments conducted on a population of mud flat-dwelling fiddler crabs at Bowling Green Bay in Queensland, Australia, revealed the males didn't stretch out their claws as much when the females were nearby.

In fact, when females were right in front of the males, the males really switched strategies by performing a less sweeping wave while lifting their bodies off the ground with their unflexed legs. How suggests that's a macho move for male crabs trying to show off their size to its best advantage.

The findings have been accepted for publication in the journal Animal Behavior

.

The male crabs have their work cut out for them because, if the big wave catches a female unawares, she may run for her life.

"Fiddler crabs carry their eyes on long vertical stalks in a fixed position above the body and the eye-stalks always stand upright," How explained.

They "can therefore simplify their visual world into things they see above the horizon and things they see below the horizon."

Since the crabs equate above-the-horizon sights with predators, like birds, the females can sometimes mistake the male's waving for the movements of a hungry threat.

"This could be a good thing, though, in that it taps into the anti-predator response of females, causing them to freeze and direct their attention towards the displaying male," How said. "But it could also backfire and cause the female to run away."

John Christy, a researcher in the Smithsonian Tropical Research Institute located both in Panama and Washington, D.C., told Discovery News that the new study "provides a detailed quantitative description" of crab communication.

Christy thinks the broader wave might allow females to choose among a variety of males, while the less dramatic wave, when she's up a bit closer, might serve to lure her into a particular burrow.

In the future, How hopes a big robotic claw might be designed to better test what specific information females glean from the sign language of their potential mates. 

Psychedelic Healing?

Psychedelic Healing?

Hallucinogenic drugs, which blew minds in the 1960s, soon may be used to treat mental ailments

 

Mind-Bending Therapies

• The drugs that put the “psychedelic” into the sixties are now the subject of renewed research interest because of their therapeutic potential.
• Psychedelics such as LSD and the compound in magic mushrooms could ease a variety of difficult-to-treat mental illnesses, such as chronic depression, post-traumatic stress disorder, and drug or alcohol dependency.
• Clinical trials with various substances are now under way in humans.

Mind-altering psychedelics are back—but this time they are being explored in labs for their therapeutic applications rather than being used illegally. Studies are looking at these hallucinogens to treat a number of otherwise intractable psychiatric disorders, including chronic depression, post-traumatic stress disorder, and drug or alcohol dependency.

The past 15 years have seen a quiet resurgence of psychedelic drug research as scientists have come to recognize the long-underappreciated potential of these drugs. In the past few years, a growing number of studies using human volunteers have begun to explore the possible therapeutic benefits of drugs such as LSD, psilocybin, DMT, MDMA, ibogaine and ketamine.

Much remains unclear about the precise neural mechanisms governing how these drugs produce their mind-bending results, but they often produce somewhat similar psychoactive effects that make them potential therapeutic tools. Though still in their preliminary stages, studies in humans suggest that the day when people can schedule a psychedelic session with their therapist to overcome a serious psychiatric problem may not be that far off.

The Trip Begins
Psychedelic drug research began in 1897, when German chemist Arthur Heffter first isolated mescaline, the primary psychoactive compound in the peyote cactus. In 1943 Swiss chemist Albert Hofmann discovered the hallucinogenic effects of LSD (lysergic acid diethylamide) at Sandoz Pharmaceuticals in Basel while studying ergot, a fungus that grows on rye. Fifteen years later, in 1958, he was the first to isolate psilocybin and psilocin—the psychoactive components of the Mexican “magic mushroom,” Psilocybe mexicana.

Before 1972, close to 700 studies with psychedelic drugs took place. The research suggested that psychedelics offered significant benefits: they helped recovering alcoholics abstain, soothed the anxieties of terminal cancer patients, and eased the symptoms of many difficult-to-treat psychiatric illnesses, such as obsessive-compulsive disorder.

For example, between 1967 and 1972 studies in terminal cancer patients by psychiatrist Stanislav Grof and his colleagues at Spring Grove State Hospital in Baltimore showed that LSD combined with psychotherapy could alleviate symptoms of depression, tension, anxiety, sleep disturbances, psychological withdrawal and even severe physical pain. Other investigators during this era found that LSD may have some interesting potential as a means to facilitate creative problem solving.

Between 1972 and 1990 there were no human studies with psychedelic drugs. Their disappearance was the result of a political backlash that followed the promotion of these drugs by the 1960s counterculture. This reaction not only made these substances illegal for personal use but also made it extremely difficult for researchers to get government approval to study them.

Things began to change in 1990, when “open-minded regulators at the FDA decided to put science before politics when it came to psychedelic and medical marijuana research,” says Rick Doblin, a public policy expert and head of the Multidisciplinary Association for Psychedelic Studies (MAPS). “FDA openness to research is really the key factor. Also, senior researchers who were influenced by psychedelics in the sixties now are speaking up before they retire and have earned credibility.” Chemist and neuropharmacologist David E. Nichols of Purdue University adds, “Baby boomers who experienced the psychedelic sixties are now mature scientists and clinicians who have retained their curiosity but only recently had the opportunity to reexplore these substances.”

Research Begins Anew
The efforts of two privately funded organizations have catalyzed much of the recent wave of research: MAPS, founded in 1986 by Doblin, and the Heffter Research Institute, started in 1993. Outside the U.S. there are groups such as the Beckley Foundation in England and the Russian Psychedelic Society. These seek out interested researchers, assist in developing the experimental design for the studies, and help to obtain funding and government approval to conduct clinical trials. They have initiated numerous FDA-approved clinical trials in the U.S., Switzerland, Israel and Spain. So far the agency has approved seven studies, with two under review and more on the way.

Current studies are focusing on psychedelic treatments for cluster headaches, depression, obsessive-compulsive disorder (OCD), severe anxiety in terminal cancer patients, post-traumatic stress disorder (PTSD), alcoholism and opiate addiction. New drugs must pass three clinical milestones before they can be marketed to the public, called phase I (for safety, usually in 20 to 80 volunteers), phase II (for efficacy, in several hundred subjects) and phase III (more extensive data on safety and efficacy come from testing the drug in up to several thousand people). All the studies discussed in this article have received government approval, and their investigators are either in the process of recruiting human subjects or have begun or completed research on human subjects in the first or second stage of this trial process.

Psychedelic drugs affect all mental functions: perception, emotion, cognition, body awareness and one’s sense of self. Unlike every other class of drugs, psychedelic drug effects depend heavily on the environment and on the expectations of the subject, which is why combining them with psychotherapy is so vital.

“Psychedelics may be therapeutic to the extent that they elicit processes that are known to be useful in a therapeutic context: transference reactions and working through them; enhanced symbolism and imagery; increased suggestibility; increased contact between emotions and ideations; controlled regression; et cetera,” says psychiatrist Rick Strassman of the University of New Mexico School of Medicine, who from 1990 to 1995 performed the first human study using psychedelic drugs in about 20 years, investigating the effects of DMT on 60 human subjects. “This all depends, though, on set and setting,” he cautions. “These same properties could also be turned to very negative experiences, if the support and expectation for a beneficial experience aren’t there.”

Mechanisms and Targets
Scientists divide classical psychedelic drugs into two basic chemical groups: tryptamines (such as LSD, DMT and psilocybin) and phen­ethylamines (such as mescaline and MDMA). In addition, some people consider so-called dissociative anesthetics (such as ketamine and PCP) to be psychedelic drugs, although the way they affect the brain is quite different.

The exact mechanisms differ, but all the tryptamine hallucinogens—which make up the majority of psychedelic drugs—selectively bind to specific serotonin receptors on neurons, mimicking the effects of the nerve-signaling chemical, or neurotransmitter, serotonin on these receptors. Phenethylamines mimic the chemical structure of another neurotransmitter, dopamine. They actually bind to many of the same serotonin receptors activated by the tryptamines, however. Serotonin is responsible for many important functions, including mood, memory, appetite, sex and sleep. It is such an essential neurochemical that any substance—such as a hallucinogen—that interferes with its action might be expected to produce dramatic changes in brain function.

How do the drugs create their perceptual effects? Neuroscientists believe that activation of a particular set of serotonin receptors, the 2A subtype, which are highly expressed (or present) in the cortex, the outermost layer of the brain, interferes with the processing of sensory information. Consciousness is thought to involve a complex interaction among the cortex, the thalamus and the striatum. Disruption of this network by activation of serotonin 2A receptors is now the most popular theory for the mechanism of action for tryptamine and phenethylamine psychedelics.

“There are at least two possible mechanisms for beneficial actions,” Nichols says. “The first simply involves a change in the numbers of brain serotonin 2A receptors. Activation of serotonin 2A receptors by psychedelics causes the number of receptors expressed on the surface of neurons to decrease, a process called downregulation. For some disorders, such as OCD, it may be this receptor downregulation that could be therapeutic,” he explains. “The other possible mechanism is a psychological effect that is harder to define but in some way produces changes in the way the subject perceives pain and distress. Psychedelics seem able to produce a profound cognitive change that provides the patient with a new insight—the ability to see the world from a new perspective—somehow reducing anxiety and raising the pain threshold.”

MDMA (3,4-methylenedioxy-N-methylamphetamine) is also chemically classified as a phenethylamine, but its action in the brain is substantially different from that of other drugs discussed in this article. “In contrast to most psychedelics, MDMA does not directly stimulate serotonin 2A receptors but instead causes dopamine, serotonin and norepinephrine [another neurotransmitter] to be released from their stores in neuron endings,” Nichols says. There is some controversy about whether MDMA has neurotoxic effects. Most researchers believe, however, that the occasional moderate use of MDMA at therapeutic doses would not be damaging. There have been no recent studies using mescaline, although MAPS plans to initiate some in the future.

In contrast to the traditional psychedelics, the dissociative anesthetics selectively bind to N-methyl-D-aspartic acid (NMDA) receptors, block­ing the neurotransmitter glutamate from activating these receptors. “Because glutamate is an essential neurotransmitter that activates neurons, this blocking effect seems to prevent the processing of sensory information by the brain,” Nichols states.

Ketamine appears to hold particular promise as a psychedelic therapy because it is already among the selections in Western medicine’s pharmacopoeia. In addition to being part of a different chemical class of drugs than the other psychedelics, ketamine is in a separate legal class as an FDA-approved schedule III drug. This designation means that any physician can administer it for an off-label use if he or she believes it will help the patient.

Although some research indicates that psychedelic drugs may enhance suggestibility and certain aspects of psychotherapy, the benefits of dissociative anesthetics such as ketamine and ibogaine may simply be the result of enduring biochemical changes in the brain. For example, in 2006 Carlos Zarate of the National Institute of Mental Health published a study demon­strating ketamine’s unusual antidepressant properties [see “Good News about Depression,” by Walter Brown; Scientific American Mind, June/July 2007]. A single infusion of ketamine relieved symptoms of depression in some patients within a few hours, and that relief persisted for several days.

This was the third study that showed ketamine’s powerful and enduring antidepressant effects. In an intriguing finding from one of the previous studies, subjects received the ketamine as an anesthetic for orthopedic surgery—so they were not even conscious during the mind-altering segment of the drug’s action in the brain—and the antidepressant effects occurred postoperatively.

In other work seeking to help cure addicts, a preliminary ketamine study, in which psy­chiatrist Evgeny Krupitsky of St. Petersburg, Russia, treated 59 patients with heroin dependency, produced encouraging results. And the Iboga Therapy House in Vancouver, Canada, has recently begun a study that has so far successfully treated three out of 20 opiate-addicted subjects with ibogaine. The experimental procedure substantially reduced the withdrawal symptoms associated with opiate addiction, helping the addicts to recover and break their dependency on the drug.

OCD, Cluster Headaches and Cancer
In addition to the promising work with ibogaine and the dissociative anesthetics, progress is also being made in the study of conventional psychedelics. In 2006 investigators at the Johns Hopkins School of Medicine published the results of a six-year project on the effects of psilocybin, in which more than 60 percent of the participants reported positive changes in their attitude and behavior after taking the drug, a benefit that lasted for at least several months.

In another 2006 study, researchers at the University of Arizona, led by psychiatrist Francisco Moreno, found that psilocybin relieved the symptoms of nine patients with OCD. The patients suffered from a wide range of obsessions and compulsions. Some of them showered for hours; others put on their clothes over and over again until they felt right. All nine experienced improvements with at least some of the doses tested.

“What we saw was a drastic decrease in symp­toms for a period of time,” Moreno says. “People would report that it had been years since they had felt so good.” Moreno cautions that the goal

was simply to test the safety of administering psilocybin to OCD patients and that the true effectiveness of the drug is still in question until a larger controlled study can be conducted. Such a study is being planned, although there are currently no funds available for it. According to Moreno, however, no treatment in the medical literature eases OCD symptoms as fast as psilocybin does. Whereas other drugs take several weeks to show an effect, psilocybin worked almost immediately.

Preliminary results of a current study led by psychiatrist Charles Grob of the Harbor-UCLA Medical Center suggest that psilocybin may reduce the psychological distress associated with terminal cancer. This research seeks to measure the effectiveness of psilocybin on the reduction of anxiety, depression and physical pain in advanced-stage cancer patients. Grob’s study is almost complete; 11 out of 12 subjects have already been treated. Although the formal data analysis has not been completed, “my impression,” Grob says, “from just staying in touch with these people and following them is that some do seem to be functioning better psychologically. There seems to be less anxiety, improved mood and an overall improved quality of life. There also seems to be less fear of death.”

The first studies of psychedelic drugs at Harvard University since 1965 are also now under way. In one study, psychiatrist John Halpern and his colleagues are looking into using LSD and psilocybin to treat the debilitating symptoms of cluster headaches. The researchers, who are in the process of recruiting subjects, will probably begin trials in early 2008.

Acute Anxiety and PTSD
Another study at Harvard, also led by Halpern, will look into MDMA-assisted psychotherapy in subjects with anxiety associated with advanced-stage cancer—similar to Grob’s psilocybin study—using measures to evaluate anxiety, pain and overall quality of life. This study is also in the process of recruiting human subjects.

Psychiatrist Michael Mithoefer in Charleston, S.C., is running an MDMA study for treatment-resistant PTSD victims of crime, war or childhood sexual abuse. So far 17 out of 20 such subjects have already undergone the experimental therapy. “At this point the results are very promising,” Mithoefer says. “I think we’re seeing pretty strong, robust effects in some people. I hasten to add these are preliminary findings—we’re not ready to draw conclusions yet. But assuming it keeps going this way for the rest of the study, it certainly seems that there’s very good reason to go on to larger phase III trials.”

Although we are still in the early days of psychedelic therapy research, the initial data show considerable promise. A growing number of scientists believe that psychedelic drugs may offer safe and effective help for people with certain treatment-resistant psychiatric disorders and could possibly help some people who receive partial relief from current methods to obtain a more complete healing.