Gibson and Green (2002), talking about a possible link between glucose and cognition, wrote that research in the area …is based on the assumption that, since glucose is the major source of fuel for the brain, alterations in plasma levels of glucose will result in alterations in brain levels of glucose, and thus neuronal function. However, the strength of this notion lies in its common-sense plausibility, not in scientific evidence… (p. 185).
Those bright, round yolks are rich in choline, a B vitamin-like nutrient. When you eat eggs, your brain uses choline to make acetylcholine, a neurotransmitter that may be important for maintaining memory and communication among brain cells. Boston University researchers tracked the eating habits of nearly 1,400 healthy adults for 10 years and found that choline intake correlated positively with better performance on certain types of memory tests. These simple brain exercises will help you get smarter.
However, despite these apparent good results, it’s recommended that you don’t run to the pharmacy just yet. The long term effects of taking Modafinil haven’t been studied conclusively or in-depth yet; to the contrary and in direct opposition to the many claims that Modafinil is completely safe, 50% of modafinil users report a number of short term side effects, such as mild to severe headaches, insomnia, nausea, anxiety, nervousness, hypertension, decreased appetite, and weight loss.
Harriet Hall, MD also known as The SkepDoc, is a retired family physician who writes about pseudoscience and questionable medical practices. She received her BA and MD from the University of Washington, did her internship in the Air Force (the second female ever to do so),  and was the first female graduate of the Air Force family practice residency at Eglin Air Force Base. During a long career as an Air Force physician, she held various positions from flight surgeon to DBMS (Director of Base Medical Services) and did everything from delivering babies to taking the controls of a B-52. She retired with the rank of Colonel.  In 2008 she published her memoirs, Women Aren't Supposed to Fly.
Blinding stymied me for a few months since the nasty taste was unmistakable and I couldn’t think of any gums with a similar flavor to serve as placebo. (The nasty taste does not seem to be due to the nicotine despite what one might expect; Vaniver plausibly suggested the bad taste might be intended to prevent over-consumption, but nothing in the Habitrol ingredient list seemed to be noted for its bad taste, and a number of ingredients were sweetening sugars of various sorts. So I couldn’t simply flavor some gum.)
(People aged <=18 shouldn’t be using any of this except harmless stuff - where one may have nutritional deficits - like fish oil & vitamin D; melatonin may be especially useful, thanks to the effects of screwed-up school schedules & electronics use on teenagers’ sleep. Changes in effects with age are real - amphetamines’ stimulant effects and modafinil’s histamine-like side-effects come to mind as examples.)
Aside from the obvious pleasure some derive from this traditional combo, are there any actual benefits to simultaneously smoking and drinking coffee? One study in the Journal of Epidemiology and Community Health definitely concludes that the answer is yes. In the study, researchers analyzed 497 men and women with confirmed cases of papilloma, carcinoma and polyps of the bladder. All study participants, along with 1,113 control cases, were interviewed to determine the use of tobacco, exposure to secondhand smoke and coffee drinking.
Caffeine metabolism is primarily determined by the cytochrome enzyme P-450 1A2 (CYP1A2), and studies have shown that different ethnic populations exhibit widely varying expressions of the gene responsible for CYP1A2. Evidence suggests that a particular CYP1A2 impacts caffeine consumption by modifying the risks of certain diseases that are associated with caffeine consumption. It has also been shown that variations in the expression of genes that code for adenosine and dopamine receptors play a role in mediating your response to caffeine. For example, in Caucasians, the presence of certain genetic expressions for both adenosine and dopamine receptors is associated with caffeine-induced anxiety. Variations in CYP1A2 are also responsible for the speed at which different people metabolize caffeine.
There are a ton of great rosemary snack options. Personally, I always keep some flavored natural sea salts in my desk to spice up my snacks and meals at the office. Here’s a great option for rosemary flavored sea salt. Another great choice is the Parmesan Rosemary Popcorn from Quinn’s Popcorn. They never use GMO corn, coatings or chemicals on the bag, or any other scary stuff found in traditional microwave popcorn. This is truly microwave popcorn reinvented.
Jump up ^ Weyandt LL, Oster DR, Marraccini ME, Gudmundsdottir BG, Munro BA, Zavras BM, Kuhar B (September 2014). "Pharmacological interventions for adolescents and adults with ADHD: stimulant and nonstimulant medications and misuse of prescription stimulants". Psychol. Res. Behav. Manag. 7: 223–249. doi:10.2147/PRBM.S47013. PMC 4164338. PMID 25228824.
It looks like the overall picture is that nicotine is absorbed well in the intestines and the colon, but not so well in the stomach; this might be the explanation for the lack of effect, except on the other hand, the specific estimates I see are that 10-20% of the nicotine will be bioavailable in the stomach (as compared to 50%+ for mouth or lungs)… so any of my doses of >5ml should have overcome the poorer bioavailability! But on the gripping hand, these papers are mentioning something about the liver metabolizing nicotine when absorbed through the stomach, so…
Took pill 12:11 PM. I am not certain. While I do get some things accomplished (a fair amount of work on the Silk Road article and its submission to places), I also have some difficulty reading through a fiction book (Sum) and I seem kind of twitchy and constantly shifting windows. I am weakly inclined to think this is Adderall (say, 60%). It’s not my normal feeling. Next morning - it was Adderall.
By the way, before we move on, allow me to clarify what I mean by “slow caffeine metabolizer”. Ever wondered why your co-worker can slam four giant mugs of coffee during a brief morning of work, while one shot of espresso leaves you jittery and irritated? Turns out that not everyone metabolizes caffeine the same. Generally speaking, in healthy adults, caffeine has a half-life that ranges from about 3 to 7 hours. For example, if the half-life of caffeine in your blood is 5 hours, that means that it takes 5 hours for caffeine levels to be reduced by 50%. Then it takes another 5 hours for that amount to be reduced by 50%. While caffeine metabolism time also depends upon age and environmental factors, a big influence on varying caffeine half-life times is your genetic makeup.

I am sort of a health nut. I only use natural medicines- never prescriptions. Lately I have been experiencing some brain fog in spite of my detoxing, so I tried this product. I LOVE IT! I really can tell a difference. I have tried many memory and brain support supplements before, but this one seems quite different. I love the daytime and separate night time formulas. I have never slept so soundly in my life. In fact, I've always had a lot of trouble sleeping, but I sleep like a baby and wake feeling refreshed and full of energy.
I stayed up late writing some poems and about how [email protected] kills, and decided to make a night of it. I took the armodafinil at 1 AM; the interesting bit is that this was the morning/evening after what turned out to be an Adderall (as opposed to placebo) trial, so perhaps I will see how well or ill they go together. A set of normal scores from a previous day was 32%/43%/51%/48%. At 11 PM, I scored 39% on DNB; at 1 AM, I scored 50%/43%; 5:15 AM, 39%/37%; 4:10 PM, 42%/40%; 11 PM, 55%/21%/38%. (▂▄▆▅ vs ▃▅▄▃▃▄▃▇▁▃)
Surgeries – Here's another unpleasant surprise. You're probably thinking we're referring to a brain surgery, but that's not the only surgery that can influence the blood flow to your brain the bad way. For example, a heart surgery can cause hypoperfusion. How? Fat globules, which are released during these kinds of procedures, can find their way to your brain and disrupt the optimal blood flow.
By the way, since I’ll throw around the term a few more times in this article, I should probably clarify what an adaptogen actually is. The actual name adaptogen gives some hint as to what these fascinating compounds do: they help you to adapt, specifically by stimulating a physiological adaptive response to some mild, hormesis-like stressor. A process known as general adaptation syndrome (GAS) was first described by the 20th-century physician and organic chemist Hans Selye, who defined GAS as the body’s response to the demands placed upon it. When these demands are excessive and consistent, it can result in the common deleterious symptoms now associated with long-term exposure to chronic stress. GAS is comprised of an alarm stage (characterized by a burst of energy), a resistance stage (characterized by resistance or adaptation to the stressor), and – in the case of excessive and chronic stress – an exhaustion stage (characterized by energy depletion). Adaptogens are plant-derived compounds capable of modulating these phases of GAS by either downregulating stress reactions in the alarm phase or inhibiting the onset of the exhaustion phase, thus providing some degree of protection against damage from stress.

The important factors seem to be: #1/MR6 (Creativity.self.rating, Time.Bitcoin, Time.Backups, Time.Blackmarkets,, #2/MR1 (Time.PDF, Time.Stats), #7/MR7 (Time.Writing, Time.Sysadmin, Time.Programming,, and #8/MR8 (Time.States, Time.SRS, Time.Sysadmin, Time.Backups, Time.Blackmarkets). The rest seem to be time-wasting or reflect dual n-back/DNB usage (which is not relevant in the LLLT time period).

Similarly, we could try applying Nick Bostrom’s reversal test and ask ourselves, how would we react to a virus which had no effect but to eliminate sleep from alternating nights and double sleep in the intervening nights? We would probably grouch about it for a while and then adapt to our new hedonistic lifestyle of partying or working hard. On the other hand, imagine the virus had the effect of eliminating normal sleep but instead, every 2 minutes, a person would fall asleep for a minute. This would be disastrous! Besides the most immediate problems like safely driving vehicles, how would anything get done? You would hold a meeting and at any point, a third of the participants would be asleep. If the virus made it instead 2 hours on, one hour off, that would be better but still problematic: there would be constant interruptions. And so on, until we reach our present state of 16 hours on, 8 hours off. Given that we rejected all the earlier buffer sizes, one wonders if 16:8 can be defended as uniquely suited to circumstances. Is that optimal? It may be, given the synchronization with the night-day cycle, but I wonder; rush hour alone stands as an argument against synchronized sleep - wouldn’t our infrastructure would be much cheaper if it only had to handle the average daily load rather than cope with the projected peak loads? Might not a longer cycle be better? The longer the day, the less we are interrupted by sleep; it’s a hoary cliche about programmers that they prefer to work in long sustained marathons during long nights rather than sprint occasionally during a distraction-filled day, to the point where some famously adopt a 28 hour day (which evenly divides a week into 6 days). Are there other occupations which would benefit from a 20 hour waking period? Or 24 hour waking period? We might not know because without chemical assistance, circadian rhythms would overpower anyone attempting such schedules. It certainly would be nice if one had long time chunks in which could read a challenging book in one sitting, without heroic arrangements.↩
Pop this pill and improve your memory. Swallow that one and reduce your cognitive decline. We see ads for such products all the time and I suspect they will increase as the baby boomers reach senior citizenhood. The most popular brain boosting supplements are fish oil pills and they are also probably the best studied ones. The results are not encouraging. When all the studies are pooled, we are left with the possibility of a barely significant improvement in recalling lists of words soon after they have been learned, but the effect does not last. Extracts of the ginkgo biloba tree are also popular, and here the prospects are even dimmer. There is no impact on memory, despite claims of increased circulation in the brain. And ginkgo can interfere with the action of anticoagulants and has also been shown to be an animal carcinogen.

Walnuts are chock-full of heart-healthy and anti-inflammatory nutrients, and are the only good nut source of alpha linolenic acid (ALA), HuffPost Healthy Living earlier reported. That means they help promote blood flow, which in turn allows for efficient delivery of oxygen to the brain. And research presented at the 2010 International Conference on Alzheimer's found that mice with the disease who were regularly fed walnuts had improved memory, learning and motor skill coordination, according to MyHealthNewsDaily.

Growing up, Joe was plagued with a myriad of health issues such as gut problems, autoimmune issues, chronic fatigue, brain fog, insomnia, and general inflammation. Both conventional and alternative doctors weren’t able to help him, so he decided to fix himself. With lots of health questions and few satisfying answers, Joe decided to read every research paper he could get his hands on and conduct thousands of experiments on his own body in order to fix his health issues. Joe started SelfHacked in late 2013 when he successfully fixed all of his issues, and now it gets millions of readers a month looking to educate themselves about how they can improve their health. Joe is now a thriving author, speaker, and serial entrepreneur, founding SelfDecode & LabTestAnalyzer.
…researchers have added a new layer to the smart pill conversation. Adderall, they’ve found, makes you think you’re doing better than you actually are….Those subjects who had been given Adderall were significantly more likely to report that the pill had caused them to do a better job….But the results of the new University of Pennsylvania study, funded by the U.S. Navy and not yet published but presented at the annual Society for Neuroscience conference last month, are consistent with much of the existing research. As a group, no overall statistically-significant improvement or impairment was seen as a result of taking Adderall. The research team tested 47 subjects, all in their 20s, all without a diagnosis of ADHD, on a variety of cognitive functions, from working memory-how much information they could keep in mind and manipulate-to raw intelligence, to memories for specific events and faces….The last question they asked their subjects was: How and how much did the pill influence your performance on today’s tests? Those subjects who had been given Adderall were significantly more likely to report that the pill had caused them to do a better job on the tasks they’d been given, even though their performance did not show an improvement over that of those who had taken the placebo. According to Irena Ilieva…it’s the first time since the 1960s that a study on the effects of amphetamine, a close cousin of Adderall, has asked how subjects perceive the effect of the drug on their performance.

Pyritinol: Pyritinol has anti-oxidant effects for supporting the long-term health of the brain. But its primary benefit is aiding glucose uptake for periods of extended mental strain. If you are studying or working for a long period of time, your brain will start to diminish its glucose (sugar) stores which are the primary way that the brain derives its energy.

* These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure or prevent any disease. The information on this site is for educational purposes only and should not be considered medical advice. Please speak with an appropriate healthcare professional when evaluating any wellness related therapy. Please read the full medical disclaimer before taking any of the products offered on this site.
I follow Jesus and use nootropics to help me glorify God with my mind. Many conservative Christians would say that micro-dosing on LSD is a sin because it is somewhat mind altering and we are called to be sober-minded (1 Peter 5:8). I am just curious. I have a follow Christian brother who uses cannabis as a supplement to help him do work on a daily basis..yet I worry about him sometimes because his tolerance is so high. It’s a grey area for sure because the Bible isn’t explicit about the topic.
After informally testing various formulas of Qualia OS on themselves and friends, Collective founders did an unblinded pilot study with nine volunteers that Dr. Stickler says showed significant benefits in cognitive function and stress response in eight of the subjects. Still, he admits this isn’t airtight scientific proof that the product works. He says the Collective is hoping to do a placebo-controlled study, but in the meantime, he’s confident the stack works because of the results he’s seen in patients.
The U. S. nootropics industry was valued at more than $1.3 billion in 2015 and is projected to reach $6 billion by 2024. This growth is due in part to slick marketing from biohacking “experts” such as Dave Asprey (founder of Bulletproof) and Josiah Zayner, Ph.D. (CEO of the Odin), who’ve built big social-media and podcast followings as well as customer bases. At the grassroots level, there are meetups across the country like the one at Idea Coffee, plus a vibrant online community.
Theanine can also be combined with caffeine as both of them work in synergy to increase memory, reaction time, mental endurance, and memory. The best part about Theanine is that it free of side effects and is easily available in the form of capsules.  A natural option would be to use a good green tea brand which constitutes of tea grown in the shade, because then Theanine would be abundantly present in it.
An important dietary step to avoid heavy metal toxicity is choosing seafood and fish that has reduced levels of exposure. The Seafood Watch web page is a fantastic resource that has an extensive list of fish, seafood and sushi products that are safe, as well as those that are best to stay away from. For example, choosing wild pacific caught salmon is safer than Atlantic caught salmon.
“We stumbled upon fasting as a way to optimize cognition and make yourself into a more efficient human being,” says Manuel Lam, an internal medicine physician who advises Nootrobox on clinical issues. He and members of the company’s executive team have implanted glucose monitors in their arms — not because they fear diabetes but because they wish to track the real-time effect of the foods they eat.
Speaking of addictive substances, some people might have considered cocaine a nootropic (think: the finance industry in Wall Street in the 1980s). The incredible damage this drug can do is clear, but the plant from which it comes has been used to make people feel more energetic and less hungry, and to counteract altitude sickness in Andean South American cultures for 5,000 years, according to an opinion piece that Bolivia’s president, Evo Morales Ayma, wrote for the New York Times.
Using neuroenhancers, Seltzer said, "is like customising yourself - customising your brain". For some people, he added, it was important to enhance their mood, so they took antidepressants; but for people like him it was more important "to increase mental horsepower". He said: "It's fundamentally a choice you're making about how you want to experience consciousness." Whereas the 1990s had been about "the personalisation of technology", this decade was about the personalisation of the brain - what some enthusiasts have begun to call "mind hacking".
Upon examining the photographs, I noticed no difference in eye color, but it seems that my move had changed the ambient lighting in the morning and so there was a clear difference between the two sets of photographs! The before photographs had brighter lighting than the after photographs. Regardless, I decided to run a small survey on QuickSurveys/Toluna to confirm my diagnosis of no-change; the survey was 11 forced-choice pairs of photographs (before-after), with the instructions as follows:
Working memory has been likened to a mental scratch pad: you use it to keep relevant data in mind while you're completing a task. (Imagine a cross-examination, in which a lawyer has to keep track of the answers a witness has given and formulate new questions based on them.) In one common test subjects are shown a series of items - usually letters or numbers - and then presented with challenges: was this number or letter in the series? Was this one? In the working-memory tests, subjects performed better on neuroenhancers, though several of the studies suggested that the effect depended on how good a subject's working memory was to begin with: the better it was, the less benefit the drugs provided.
Herbs and plants have been used for cognitive enhancement for at least 5,000 years in Indian and Chinese medicine, long before the first synthetic nootropic was created. The practice of Indian Ayurvedic medicine includes the use of a group of nootropic plants known as Medhya Rasayana, the four primary plants of which are Mandukaparni, Yastimadhu, Duduchi and Shankhapushpi, though other lesser known plants are also used. One of the most common supplements in Ayurvedic medicine is Brahmi, known scientifically as “Bacopa monnieri” or “B. monnieri “ and more commonly as water hyssop, Thyme-leaved Gratiola, herb of grace or Indian pennywort. It is named after Lord Brahma, the creator God and originator of Ayurveda, and has been used for centuries to treat disorders ranging from pain and epilepsy to inflammation and memory dysfunction. The exact mechanism behind its action is not fully understood, but it is believed to promote antioxidant activity as well as protect neurons in the prefrontal cortex, hippocampus and corpus striatum against cytotoxicity and DNA damage associated with Alzheimer’s. The prefrontal cortex is critical in rational, social and personality behavior, the hippocampus is believed to be the seat of memory and the autonomic nervous system and the striatum play a role in the reward system of action, so the protection Brahmi provides is extremely helpful in preventing the degeneration of many important cognitive faculties. An effective dose ranges from 300 to 450 mg per day. Winter cherry (ashwagandha) is another well-known Ayurvedic supplement that can promote improved cognitive development, memory and intelligence and reduce the effects of neurodegenerative diseases such as Parkinson’s, Huntington’s and Alzheimer’s. The optimal dose is 6,000 mg per day divided into three 2,000 mg doses. Aloeweed (shankhpushpi) is also used in Ayurvedic medicine to improve memory and intellect as well as treat hypertension, epilepsy and diabetes. Effective doses for most neuroenhancing benefits range as high as 40 g per day.
There are over a thousand websites and hundreds of reference guides chock full of complicated methods for combining many of the compounds you’ve just discovered. There’s a reason for this: the practice of “stacking” nootropics and smart drugs into specific combinations can be far more powerful and efficacious than consuming a single, lonely compound in isolation. For example, dosing choline sources with your morning coffee can make your brain feel fresh for hours or mixing curcumin with black pepper can dramatically amp up the neural anti-inflammatory effects of both compounds. Ultimately, a teaspoon of lion’s mane extract just isn’t as titillating as lion’s mane blended with caffeine, theanine, nicotine and a touch of vinpocetine.

One might suggest just going to the gym or doing other activities which may increase endogenous testosterone secretion. This would be unsatisfying to me as it introduces confounds: the exercise may be doing all the work in any observed effect, and certainly can’t be blinded. And blinding is especially important because the 2011 review discusses how some studies report that the famed influence of testosterone on aggression (eg. Wedrifid’s anecdote above) is a placebo effect caused by the folk wisdom that testosterone causes aggression & rage!
Feeling behind, I resolved to take some armodafinil the next morning, which I did - but in my hurry I failed to recall that 200mg armodafinil was probably too much to take during the day, with its long half life. As a result, I felt irritated and not that great during the day (possibly aggravated by some caffeine - I wish some studies would be done on the possible interaction of modafinil and caffeine so I knew if I was imagining it or not). Certainly not what I had been hoping for. I went to bed after midnight (half an hour later than usual), and suffered severe insomnia. The time wasn’t entirely wasted as I wrote a short story and figured out how to make nicotine gum placebos during the hours in the dark, but I could have done without the experience. All metrics omitted because it was a day usage.
"In an era of confusion about what we should eat, Brain Food is a shining light. This is the straight story about 'neuro-nutrition' firmly rooted in research by a neuroscientist who has a deep understanding of how food affects our cognitive health. Dr. Mosconi gives us advice we can easily implement into our lives and a story about the science behind it that is both delightful and accessible. A must read!"
Essential fatty acids (EFAs) cannot be made by the body which means they must be obtained through diet. The most effective omega-3 fats occur naturally in oily fish in the form of EPA and DHA. Good plant sources include linseed (flaxseed), soya beans, pumpkin seeds, walnuts and their oils. These fats are important for healthy brain function, the heart, joints and our general wellbeing. What makes oily fish so good is that they contain the active form of these fats, EPA and DHA, in a ready-made form, which enables the body to use it easily. The main sources of oily fish include salmon, trout, mackerel, herring, sardines, pilchards and kippers. Low DHA levels have been linked to an increased risk of dementia, Alzheimer's disease and memory loss whilst having sufficient levels of both EPA and DHA is thought to help us manage stress and helps make the good mood brain chemical, serotonin. If you're vegetarian or vegan, you may wish to add seeds like linseed and chia to your diet, or consider a plant-based omega-3 supplement. If you are considering taking a supplement speak to your GP first.

Is a powerful antioxidant that can help you deal with the brain aging process caused by the harmful effects of free radicals. This ingredient does an amazing job of protecting you against muscle catabolism and brain deterioration. In addition, it helps your blood vessels to expand, so all essential ingredients and oxygen are delivered to your brain. The traditional Chinese medicine has been using this herb to boost memory and mental performance.
Caffeine + L-Theanine: Since caffeine can produce unwanted side effects in high amounts (such as jitteriness and headaches), most people, and especially “slow caffeine oxidizers” find that by adding L-Theanine to a caffeine source such as coffee, any negative side effects of caffeine can be controlled. Caffeine and L-Theanine in combination have been researched and proven to boost concentration, attention, and energy while reducing anxiety. For this stack, use a ratio of four parts L-Theanine to one part caffeine, such as 400 milligrams of L-Theanine along with 100 milligrams of caffeine. You may want to start out with a smaller dose such as 200 milligrams of L-Theanine and 50 milligrams of caffeine and work your way up to find the best dose for you (the average cup of coffee has about 100mg of caffeine).
Conversely, you have to consider that the long term effects of Modafinil haven’t been studies very well. It significantly upsets sleep cycles, and 50% of Modafinil users report a number of short term side effects, such as mild to severe headaches, insomnia, nausea, anxiety, nervousness, hypertension, decreased appetite, and weight loss. PET scans show it affects the same areas of the brain that are stimulated by substance abuse.
With the new wave of mindful eating, I feel like we're getting a step closer to eliminate the "diet culture" that is constantly sending us messages that our bodies aren't enough, how we need to comply with certain beauty standards, and restrict ourselves from certain meals because they affect the way we look. An important shift needs to be made in the latter: we should pay attention to the way food makes us feel, not to the way it makes us look. 
As Sulbutiamine crosses the blood-brain barrier very easily, it has a positive effect on the cholinergic and the glutamatergic receptors that are responsible for vital activities impacting memory, concentration, and mood. The compound is also fat soluble, which means it circulates rapidly and widely throughout the body and the brain, ensuring positive results. Thus, patients with schizophrenia and Parkinson’s disease will find the drug to be very effective.

True Focus offers several very positive elements. The ingredients are excellent quality and all natural and without side effects. We like the fact they offer a product that is both vegan and vegetarian friendly, as well as being gluten, soy and dairy free. This allows many consumers to experience the benefits of this product. The fact they do not offer a clear money-back guarantee, we felt, placed them in a weaker position. Moreover, the lack of multi-purchase price deals left us feeling that this was slightly expensive, as with no options to reduce the cost per bottle, consumers will be stuck paying slightly more for each bottle.
Jump up ^ Greely, Henry; Sahakian, Barbara; Harris, John; Kessler, Ronald C.; Gazzaniga, Michael; Campbell, Philip; Farah, Martha J. (December 10, 2008). "Towards responsible use of cognitive-enhancing drugs by the healthy". Nature. Nature Publishing Group. 456 (7223): 702–705. Bibcode:2008Natur.456..702G. doi:10.1038/456702a. ISSN 1476-4687. OCLC 01586310. PMID 19060880. Retrieved March 25, 2014. (Subscription required (help)).