While too much alcohol can certainly destroy healthy brain tissue, drinking in moderation may be good for your mind. A study published earlier this year in the Journal of Biological Chemistry found that the antioxidant EGCG—found in red wine and green tea—helped stop beta-amyloid proteins from harming brain cells in the lab. Additionally, research from UCLA found that wine’s antioxidants may block proteins that build brain-destroying plaques. In other recent news, British researchers discovered that rats improved spatial memory when they consumed what would be the equivalent of a daily glass of champagne; certain antioxidants in the bubbly may encourage growth of and better communication among nerve cells.
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.
Cost-wise, the gum itself (~$5) is an irrelevant sunk cost and the DNB something I ought to be doing anyway. If the results are negative (which I’ll define as d<0.2), I may well drop nicotine entirely since I have no reason to expect other forms (patches) or higher doses (2mg+) to create new benefits. This would save me an annual expense of ~$40 with a net present value of <820 ($); even if we count the time-value of the 20 minutes for the 5 DNB rounds over 48 days (0.2 \times 48 \times 7.25 = 70), it’s still a clear profit to run a convincing experiment.
Safety Warning Do not exceed recommended dose. Not intended for pregnant or nursing mothers or children under the age of 18. Individuals taking blood thinners, any other medications, or have any known medical conditions should consult a physician before using any herbal supplements. Discontinue use and consult your doctor if any adverse reactions occur. Not intended to treat obesity; consult a physician before beginning any weight loss program. KEEP OUT OF REACH OF CHILDREN. DO NOT USE IF SAFETY SEAL IS DAMAGED OR MISSING. KEEP BOTTLE CLOSED TIGHTLY AND STORE IN A COOL, DRY PLACE. Do not exceed recommended dose. Not intended for pregnant or nursing mothers or children under the age of 18. Individuals taking blood thinners, any other medications, or have any known medical conditions should consult a physician before using any herbal supplements. Discontinue use and consult your doctor if any adverse reactions occur. Not intended to medical conditions; consult a physician before beginning any weight loss program. KEEP OUT OF REACH OF CHILDREN. DO NOT USE IF SAFETY SEAL IS DAMAGED OR MISSING. KEEP BOTTLE CLOSED TIGHTLY AND STORE IN A COOL, DRY PLACE. CAUTION: Do not exceed recommended dose. St. John’s Wort may contribute to photosensitivity resulting in skin irritation and redness in persons exposed to strong sunlight or tanning booths. Avoid use in patients at risk of bleeding, taking anticoagulants, or with clotting disorders, based on case reports of bleeding. Discontinue use 2-3 weeks prior to some surgical and dental procedures due to increased risk of bleeding. Avoid use in couples who are trying to conceive, based on theoretical reduction of fertility. Pregnant or nursing mothers, children under 18, individuals with history of seizure, taking MAO inhibiting drugs, or with a known medical condition should consult a physician before using this or any dietary supplement. This product is manufactured and packaged in a facility which may also process milk, soy, wheat, egg, peanuts, tree nuts, fish and crustacean shellfish. — This product is a dietary supplement. If you feel an adverse reaction, please contact our support staff immediately to notify us of the issue so that we can offer assistance. Please consult with a physician prior to beginning this supplement. This product has not been approved by the Food and Drug Administration. Keep out of reach of children. Do not use if safety seal is damaged or missing. Store at a room temperature. Avoid in patients at risk of bleeding, taking anticoagulants, or with clotting disorders, based on case reports of bleeding. Discontinue use 2-3 weeks prior to some surgical and dental procedures due to increased risk of bleeding. Use cautiously in patients with history of seizure, based on reports of seizure due to Ginkgo seed ingestion. Not intended for children under 18 years of age. Avoid use in couples who are trying to conceive, based on theoretical reduction of fertility. Pregnant or nursing mothers, children under 18, individuals making MAO inhibiting Drugs, or with a known medical condition should consult a physician before using this or any dietary supplement.
Apart from the risks that accompany drugs with dopaminergic effects, amphetamines, even when used to treat neurological disorders like ADHD, have been known to frequently and predictably cause anorexia, weight loss and insomnia. High doses can cause psychotic behavior, and even normal doses have been known to produce psychosis that ranged from the loss of short-term memory to horrific visual and auditory hallucinations. Are you getting the impression that using synthetic stimulants to flood your brain short-term with excessive or unnaturally high levels of hormones and neurotransmitters may not be a good idea, especially when done frequently or in excess?
Since coffee drinking may lead to a worsening of calcium balance in humans, we studied the serial changes of serum calcium, PTH, 1,25-dihydroxyvitamin D (1,25(OH)2D) vitamin D and calcium balance in young and adult rats after daily administration of caffeine for 4 weeks. In the young rats, there was an increase in urinary calcium and endogenous fecal calcium excretion after four days of caffeine administration that persisted for the duration of the experiment. Serum calcium decreased on the fourth day of caffeine administration and then returned to control levels. In contrast, the serum PTH and 1,25(OH)2D remained unchanged initially, but increased after 2 weeks of caffeine administration…In the adult rat group, an increase in the urinary calcium and endogenous fecal calcium excretion and serum levels of PTH was found after caffeine administration. However, the serum 1,25(OH)2D levels and intestinal absorption coefficient of calcium remained the same as in the adult control group.
Perhaps the most well-known natural nootropic stimulant and neuroenhancer is caffeine. Caffeine has been shown to prevent memory deficits in experimental models of Alzheimer’s disease and may even restore memory following impairment. In studies performed with college students, caffeine was shown to have particularly potent effects on memory improvement during students’ non-optimal time of day, in this case, early in the morning. Caffeine’s benefits go even further because it’s never found in an isolated vacuum in nature, meaning that it’s always located in some kind of plant such as green tea or bean such as coffee that carry additional beneficial compounds which often enhance the effects of caffeine, including, most notably, certain cholesterols, polyphenols and antioxidants. In fact, one study determined that caffeine alone does not account for the benefits caused by coffee consumption. Rather, the phytochemical content of coffee (coffee contains over 1,000 different natural chemicals!) gives it potent antioxidant and anti-inflammatory properties that complement the neuroprotective effects of caffeine on the central nervous system.
I took 1.5mg of melatonin, and went to bed at ~1:30AM; I woke up around 6:30, took a modafinil pill/200mg, and felt pretty reasonable. By noon my mind started to feel a bit fuzzy, and lunch didn’t make much of it go away. I’ve been looking at studies, and users seem to degrade after 30 hours; I started on mid-Thursday, so call that 10 hours, then 24 (Friday), 24 (Saturday), and 14 (Sunday), totaling 72hrs with <20hrs sleep; this might be equivalent to 52hrs with no sleep, and Wikipedia writes:
Cocoa flavanols (CF) positively influence physiological processes in ways which suggest that their consumption may improve aspects of cognitive function. This study investigated the acute cognitive and subjective effects of CF consumption during sustained mental demand. In this randomized, controlled, double-blinded, balanced, three period crossover trial 30 healthy adults consumed drinks containing 520 mg, 994 mg CF and a matched control, with a 3-day washout between drinks. Assessments included the state anxiety inventory and repeated 10-min cycles of a Cognitive Demand Battery comprising of two serial subtraction tasks (Serial Threes and Serial Sevens), a Rapid Visual Information Processing (RVIP) task and a mental fatigue scale, over the course of 1 h. Consumption of both 520 mg and 994 mg CF significantly improved Serial Threes performance. The 994 mg CF beverage significantly speeded RVIP responses but also resulted in more errors during Serial Sevens. Increases in self-reported mental fatigue were significantly attenuated by the consumption of the 520 mg CF beverage only. This is the first report of acute cognitive improvements following CF consumption in healthy adults. While the mechanisms underlying the effects are unknown they may be related to known effects of CF on endothelial function and blood flow.
Ngo has experimented with piracetam himself (“The first time I tried it, I thought, ‘Wow, this is pretty strong for a supplement.’ I had a little bit of reflux, heartburn, but in general it was a cognitive enhancer. . . . I found it helpful”) and the neurotransmitter DMEA (“You have an idea, it helps you finish the thought. It’s for when people have difficulty finishing that last connection in the brain”).
The brain of animals features in French cuisine, in dishes such as cervelle de veau and tête de veau. A dish called maghaz is a popular Muslim cuisine in Pakistan, Bangladesh, parts of India, and diaspora countries. In Turkish cuisine brain can be fried, baked, or consumed as a salad. In Chinese cuisine, brain is a delicacy in Chongqing or Sichuan cuisine, and it is often cooked in spicy hot pot or barbecued. In the southern part of China, pig brain is used for "Tianma Zhunao Tang". In South India goat brain curry or fry is a delicacy.
Omega-3 fatty acids—DHA in particular—contribute to a healthy brain. “The brain’s membranes use these fats to improve cellular structure and brain signaling, which translates into better cognitive function,” says Vasanti Malik, ScD, a research scientist in the Department of Nutrition at the Harvard T.H. Chan School of Public Health. DHA also quells chronic inflammation that can harm brain cells and lead to cognitive decline.
…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.
Some people warn of the dangers of modafinil. There are anecdotal personal accounts online of people becoming dependent on this drug. Modafinil is the generic of the brand Provigil, a nootropic. Provigil is FDA-approved to stimulate wakefulness in people suffering from sleep disorders, such as narcolepsy and sleep apnea. Initially, Provigil was thought to have a benign, non-addiction-forming profile. As such, the Drug Enforcement Administration classifies Provigil as a Schedule IV drug, a category reserved for drugs with low abuse potential; however, recent research conducted by the National Institute on Drug Abuse (NIDA) has found that Provigil may in fact be addictive.
Thanks to the many years of research in the field, we know now that what we eat can have a strong impact on our mental health. Not only can it protect us from developing Alzheimer's, but it's an act of self-care on its own. "Biology is all about harmony, about finding equilibrium and homeostasis," says Dr. Lisa, which is why her approach differs from food restrictions and focuses on minimizing intake of those foods that don't help us feel better.
The power calculation indicates a 20% chance of getting useful information. My quasi-experiment has <70% chance of being right, and I preserve a general skepticism about any experiment, even one as well done as the medical student one seems to be, and give that one a <80% chance of being right; so let’s call it 70% the effect exists, or 30% it doesn’t exist (which is the case in which I save money by dropping fish oil for 10 years).
Vitamin C has long been thought to have the power to increase mental agility, and some research suggests that a deficiency may be a risk factor for age-related brain degeneration including dementia and Alzheimer's. Furthermore, interesting studies demonstrate that vitamin C may be useful in managing anxiety and stress. One of the best sources of this vital vitamin are blackcurrants. Others include red peppers, citrus fruits such as oranges and broccoli.
This is why it was so refreshing to stumble across Dr. Lisa Mosconi's new book "Brain Food: The Surprising Power of Eating for Cognitive Power" . "Our brains aren't keeping up with the historical change in dietary consumptions", says Dr. Lisa. And it's quite evident in her book when she does a historical overview and draws an important relationship between what our ancestors were eating and the concept of longevity. Her contribution to the fascinating new world of "neuro-nutrition" differs drastically from the diet culture we are all so used to and can help us understand why including (and excluding) certain foods, will actually boost our brain health.
Armodafinil is sort of a purified modafinil which Cephalon sells under the brand-name Nuvigil (and Sun under Waklert21). Armodafinil acts much the same way (see the ADS Drug Profile) but the modafinil variant filtered out are the faster-acting molecules22. Hence, it is supposed to last longer. as studies like Pharmacodynamic effects on alertness of single doses of armodafinil in healthy subjects during a nocturnal period of acute sleep loss seem to bear out; anecdotally, it’s also more powerful, with Cephalon offering pills with doses as low as 50mg. (To be technical, modafinil is racemic: it comes in two forms which are rotations, mirror-images of each other. The rotation usually doesn’t matter, but sometimes it matters tremendously - for example, one form of thalidomide stops morning sickness, and the other rotation causes hideous birth defects.)
The chemical Huperzine-A (Examine.com) is extracted from a moss. It is an acetylcholinesterase inhibitor (instead of forcing out more acetylcholine like the -racetams, it prevents acetylcholine from breaking down). My experience report: One for the null hypothesis files - Huperzine-A did nothing for me. Unlike piracetam or fish oil, after a full bottle (Source Naturals, 120 pills at 200μg each), I noticed no side-effects, no mental improvements of any kind, and no changes in DNB scores from straight Huperzine-A.
A total of 330 randomly selected Saudi adolescents were included. Anthropometrics were recorded and fasting blood samples were analyzed for routine analysis of fasting glucose, lipid levels, calcium, albumin and phosphorous. Frequency of coffee and tea intake was noted. 25-hydroxyvitamin D levels were measured using enzyme-linked immunosorbent assays…Vitamin D levels were significantly highest among those consuming 9-12 cups of tea/week in all subjects (p-value 0.009) independent of age, gender, BMI, physical activity and sun exposure.
Many people quickly become overwhelmed by the volume of information and number of products on the market. Because each website claims its product is the best and most effective, it is easy to feel confused and unable to decide. Smart Pill Guide is a resource for reliable information and independent reviews of various supplements for brain enhancement.
After trying out 2 6lb packs between 12 September & 25 November 2012, and 20 March & 20 August 2013, I have given up on flaxseed meal. They did not seem to go bad in the refrigerator or freezer, and tasted OK, but I had difficulty working them into my usual recipes: it doesn’t combine well with hot or cold oatmeal, and when I tried using flaxseed meal in soups I learned flaxseed is a thickener which can give soup the consistency of snot. It’s easier to use fish oil on a daily basis.
The metal magnesium (Examine.com), like potassium (which didn’t help me), plays many biological roles and has an RDA for me of 400mg which is higher than I likely get (most people apparently get less, with 68% of American adults
B vitamins are also sold with claims of enhancing memory, usually rationalized by their reduction of homocysteine, a chemical in the blood that may affect circulation in the brain. No benefits from B vitamin intake have been demonstrated when it comes to memory or cognitive function except in the case of people who have high homocysteine levels due to a diet that is very low in B vitamins. There is some concern that folic acid, one of the B vitamins, may spur the growth of polyps in the colon at doses greater than 800 micrograms a day. Phosphatidyl serine is a natural component of nerve cell membranes and its promoters argue that a deficiency leads to impaired communication between nerve cells which in turn impairs cognitive function. Sounds reasonable, except that proper controlled trials have come up empty. The same goes for vinpocetine, a compound originally isolated from the lesser periwinkle plant by Hungarian chemist Csaba Szantay in 1975. It is widely used in Europe to treat strokes and memory problems with claims of increased circulation to the brain. It does indeed increase circulation, much like ginkgo, but there is no compelling evidence for memory improvement.
Oxidative stress refers to a biochemical process that occurs as a result of an accumulative everyday exposure to toxic burdens such as chemicals in cosmetics, furniture, paints, cars, and pollution. Our body has its own way of armouring itself from the damage that exposure to toxins can create through its production of endogenous antioxidants, which is nature’s way of neutralising oxidative stress. Although we have our own production of these wonder molecules, when we are continuously overloaded with toxins in our environment and have problems detoxifying, the liver can become overwhelmed. Research shows that over time oxidative stress can lead to an increase in inflammatory molecules such as cytokines, which have been shown to correlate with depression (5).This is why it is important to have a high intake of nutrients that support the liver in metabolising and removing toxins from the body, as well as regulating the inflammatory response. There are a few things we can change in our diet to support this area, for example eating foods such as the cruciferous family of vegetables which includes kale, cauliflower, broccoli and cabbage. These are particularly effective at supporting the liver in ushering out toxins as they all share an antioxidant compound called indole-3 Carbinol, which plays an important role in liver health (6). In addition, bitter greens such as collard greens, rocket, chicory and swiss chard are also great for supporting the liver’s own antioxidant defence system.
With this experiment, I broke from the previous methodology, taking the remaining and final half Nuvigil at midnight. I am behind on work and could use a full night to catch up. By 8 AM, I am as usual impressed by the Nuvigil - with Modalert or something, I generally start to feel down by mid-morning, but with Nuvigil, I feel pretty much as I did at 1 AM. Sleep: 9:51/9:15/8:27
A week later: Golden Sumatran, 3 spoonfuls, a more yellowish powder. (I combined it with some tea dregs to hopefully cut the flavor a bit.) Had a paper to review that night. No (subjectively noticeable) effect on energy or productivity. I tried 4 spoonfuls at noon the next day; nothing except a little mental tension, for lack of a better word. I think that was just the harbinger of what my runny nose that day and the day before was, a head cold that laid me low during the evening.
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!
We felt that True Focus offered a good product but the price was slightly high compared to others. Their website doesn’t show a clear money-back guarantee though, which definitely reduced their rating. We found that their customer reviews were mixed and saw that some consumers did not mind paying a little more for a product that is more consumer friendly.
The methodology would be essentially the same as the vitamin D in the morning experiment: put a multiple of 7 placebos in one container, the same number of actives in another identical container, hide & randomly pick one of them, use container for 7 days then the other for 7 days, look inside them for the label to determine which period was active and which was placebo, refill them, and start again.
OptiMind - It is one of the best Nootropic supplements available and brought to you by AlternaScript. It contains six natural Nootropic ingredients derived from plants that help in overall brain development. All the ingredients have been clinically tested for their effects and benefits, which has made OptiMind one of the best brain pills that you can find in the US today. It is worth adding to your Nootropic Stack.
The human drive to be smarter is a familiar theme on the big screen. In 2011, Oscar-nominated actor Bradley Cooper played struggling writer Eddie Morra in the sci-fi thriller Limitless. In the film, Morra acquires a (fictitious) nootropic NZT-48 that allows him to access 100 percent of his mind. Although he finds himself in lots of trouble, his use of the nootropic transforms him from a desperate writer to a multimillionaire who ultimately runs for the U.S. Senate. The film is a testament to a dream deeply entrenched in the American psyche – that an everyman can become superhuman and lead an extraordinary life.
Clarke and Sokoloff (1998) remarked that although [a] common view equates concentrated mental effort with mental work…there appears to be no increased energy utilization by the brain during such processes (p. 664), and …the areas that participate in the processes of such reasoning represent too small a fraction of the brain for changes in their functional and metabolic activities to be reflected in the energy metabolism of the brain… (p. 675).
In 2011, as part of the Silk Road research, I ordered 10x100mg Modalert (5btc) from a seller. I also asked him about his sourcing, since if it was bad, it’d be valuable to me to know whether it was sourced from one of the vendors listed in my table. He replied, more or less, I get them from a large Far Eastern pharmaceuticals wholesaler. I think they’re probably the supplier for a number of the online pharmacies. 100mg seems likely to be too low, so I treated this shipment as 5 doses:
The abuse liability of caffeine has been evaluated.147,148 Tolerance development to the subjective effects of caffeine was shown in a study in which caffeine was administered at 300 mg twice each day for 18 days.148 Tolerance to the daytime alerting effects of caffeine, as measured by the MSLT, was shown over 2 days on which 250 g of caffeine was given twice each day48 and to the sleep-disruptive effects (but not REM percentage) over 7 days of 400 mg of caffeine given 3 times each day.7 In humans, placebo-controlled caffeine-discontinuation studies have shown physical dependence on caffeine, as evidenced by a withdrawal syndrome.147 The most frequently observed withdrawal symptom is headache, but daytime sleepiness and fatigue are also often reported. The withdrawal-syndrome severity is a function of the dose and duration of prior caffeine use…At higher doses, negative effects such as dysphoria, anxiety, and nervousness are experienced. The subjective-effect profile of caffeine is similar to that of amphetamine,147 with the exception that dysphoria/anxiety is more likely to occur with higher caffeine doses than with higher amphetamine doses. Caffeine can be discriminated from placebo by the majority of participants, and correct caffeine identification increases with dose.147 Caffeine is self-administered by about 50% of normal subjects who report moderate to heavy caffeine use. In post-hoc analyses of the subjective effects reported by caffeine choosers versus nonchoosers, the choosers report positive effects and the nonchoosers report negative effects. Interestingly, choosers also report negative effects such as headache and fatigue with placebo, and this suggests that caffeine-withdrawal syndrome, secondary to placebo choice, contributes to the likelihood of caffeine self-administration. This implies that physical dependence potentiates behavioral dependence to caffeine.
L-Alpha glycerylphosphorylcholine or choline alfoscerate, also known as Alpha GPC is a natural nootropic which works both on its own and also in combination with other nootropics. It can be found in the human body naturally in small amounts. It’s also present in some dairy products, wheat germ, and in organic meats. However, these dietary sources contain small amounts of GPC, which is why people prefer taking it through supplements.
On 8 April 2011, I purchased from Smart Powders (20g for $8); as before, some light searching seemed to turn up SP as the best seller given shipping overhead; it was on sale and I planned to cap it so I got 80g. This may seem like a lot, but I was highly confident that theanine and I would get along since I already drink so much tea and was a tad annoyed at the edge I got with straight caffeine. So far I’m pretty happy with it. My goal was to eliminate the physical & mental twitchiness of caffeine, which subjectively it seems to do.
The easiest way to use 2mg was to use half a gum; I tried not chewing it but just holding it in my cheek. The first night I tried, this seemed to work well for motivation; I knocked off a few long-standing to-do items. Subsequently, I began using it for writing, where it has been similarly useful. One difficult night, I wound up using the other half (for a total of 4mg over ~5 hours), and it worked but gave me a fairly mild headache and a faint sensation of nausea; these may have been due to forgetting to eat dinner, but this still indicates 3mg should probably be my personal ceiling until and unless tolerance to lower doses sets in.
The advantage of adrafinil is that it is legal & over-the-counter in the USA, so one removes the small legal risk of ordering & possessing modafinil without a prescription, and the retailers may be more reliable because they are not operating in a niche of dubious legality. Based on comments from others, the liver problem may have been overblown, and modafinil vendors post-2012 seem to have become more unstable, so I may give adrafinil (from another source than Antiaging Central) a shot when my modafinil/armodafinil run out.
I’ve been taking nootropics on and off for a month, and despite my spurts of productivity, I’m still not 100 percent sure that they’re working. I could well be placebo-ing myself into thinking I'm working harder and focusing better than I typically do. But apparently enough people are feeling some effect, placebo or not, because nootropics start-ups are thriving. There’s truBrain, Nootrobrain, Nootroo, and a host of others. Nootrobox, the company that makes my pills, says that it’s selling "five figures" worth of cognitive supplements monthly to customers that include top Silicon Valley executives and Hollywood moguls.
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.
Systematic reviews and meta-analyses of clinical human research using low doses of certain central nervous system stimulants found enhanced cognition in healthy people. In particular, the classes of stimulants that demonstrate cognition-enhancing effects in humans act as direct agonists or indirect agonists of dopamine receptor D1, adrenoceptor A2, or both types of receptor in the prefrontal cortex. Relatively high doses of stimulants cause cognitive deficits.