Today, extraordinary research is showing that bacopa has the remarkable ability to increase levels of BDNF, a protein responsible for the growth, maintenance and survival of neurons, and the creation of new neural connections in the brain. It also has been shown to help promote the growth of new neurons and neural pathways, which helps to explain why it’s such a powerful memory and concentration booster.
It is at the top of the supplement snake oil list thanks to tons of correlations; for a review, see Luchtman & Song 2013 but some specifics include Teenage Boys Who Eat Fish At Least Once A Week Achieve Higher Intelligence Scores, anti-inflammatory properties (see Fish Oil: What the Prescriber Needs to Know on arthritis), and others - Fish oil can head off first psychotic episodes (study; Seth Roberts commentary), Fish Oil May Fight Breast Cancer, Fatty Fish May Cut Prostate Cancer Risk & Walnuts slow prostate cancer, Benefits of omega-3 fatty acids tally up, Serum Phospholipid Docosahexaenonic Acid Is Associated with Cognitive Functioning during Middle Adulthood endless anecdotes.

Professor David O Kennedy published a book in 2014 called Plants and the Human Brain. In his book he summarizes the last 15 years of research into cognitive nutrition, including the work he's done with colleagues at the Brain Performance Nutrition Research Center at Northumbria University. It's a great read and a good guide to what sorts of herbs and other plants to include in our weekly diet and it is all based on hard science rather than mere assertion or trendy but unsubstantiated beliefs.
Although piracetam has a history of “relatively few side effects,” it has fallen far short of its initial promise for treating any of the illnesses associated with cognitive decline, according to Lon Schneider, a professor of psychiatry and behavioral sciences at the Keck School of Medicine at the University of Southern California. “We don’t use it at all and never have.”
Choline is a nootropic: it enhances your ability to pay attention and learn efficiently,[18] probably because you use a lot of acetylcholine during mentally-demanding tasks, and choline helps you synthesize enough to work harder and go longer.[19] Choline also links to decreased brain inflammation in a dose-dependent manner — the more choline you eat, the less inflamed your brain tends to be.[20]
[…] The verdict is out on brain health and aging. Scientists now know that memory loss and cognitive decline are not an inevitable part of growing older. In fact, the research proves quite the contrary. You can keep your mind sharp well into old age with a strategy that combines a healthy, active lifestyle with a brain-protecting diet and brain-boosting supplements. […]
Supplements, medications, and coffee certainly might play a role in keeping our brains running smoothly at work or when we’re trying to remember where we left our keys. But the long-term effects of basic lifestyle practices can’t be ignored. “For good brain health across the life span, you should keep your brain active,” Sahakian says. “There is good evidence for ‘use it or lose it.’” She suggests brain-training apps to improve memory, as well as physical exercise. “You should ensure you have a healthy diet and not overeat. It is also important to have good-quality sleep. Finally, having a good work-life balance is important for well-being.” Try these 8 ways to get smarter while you sleep.
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…
Mosconi clarifies a few concepts. Other authors have advanced that the brain needs fat, including saturated fat, and cholesterol to function properly. Not so, Mosconi indicates that the fats we eat (saturated fat from animal protein) and cholesterol can’t even cross the blood-brain barrier. The brain needs a completely different type of fat: essential Polyunsaturated Fatty Acids (PUFAs). They include Omega-3s and Omega-6s fatty acids. Good sources of Omega-3s include fish, oils, eggs.

Eugeroics (armodafinil and modafinil) – are classified as "wakefulness promoting" agents; modafinil increased alertness, particularly in sleep deprived individuals, and was noted to facilitate reasoning and problem solving in non-ADHD youth.[23] In a systematic review of small, preliminary studies where the effects of modafinil were examined, when simple psychometric assessments were considered, modafinil intake appeared to enhance executive function.[27] Modafinil does not produce improvements in mood or motivation in sleep deprived or non-sleep deprived individuals.[28]