The foods we eat directly affect our brain function, and eating the right foods has been proven to sharpen your memory, boost intelligence, improve your mood and emotional stability, and keep your mind young.
So what foods and nutrients are essential brain-boosters?
Glucose is the most important nutrient of all for the brain and nervous system; it is sometimes referred to as brain fuel. The brain consumes more glucose that any other organ, and some carbohydrates are better at fueling the brain than others.
Slow-releasing carbohydrates, like whole grains or vegetables, and simpler carbohydrates like fruit, take longer to digest than refined carbohydrates. They therefore release energy steadily and gradually, providing an even supply of glucose to the brain.
When sugars are refined, the sweetness from the food is isolated, and produces a concentrated form of sugar devoid of vitamins and minerals. When consumed, these refined sugars cause a rapid increase followed by a sharp drop in blood sugar levels, by releasing the hormone insulin. This tries to balance the blood sugar levels by compensating for the effect of extra sugar in the body. Other refined carbohydrates like white bread and processed cereals have a similar effect.
Studies have shown that these types of carbohydrates can directly affect brain function. One study found a 25% difference between the IQ scores of children who consumed refined carbohydrates, with those that didn't . Further research found that dips in blood sugar were directly associated with poor attention, poor memory and aggressive behavior. 
Good carbohydrate foods
Generally, whole, unprocessed foods are slow to release their sugar and therefore provide good brain fuel. These include whole grains, lentils, beans, nuts, seeds, fresh fruit and vegetables. Choose dark green, leafy and root vegetables like watercress, carrots, sweet potatoes, spinach, broccoli, or peppers.
The first two can be made in the body, but the omegas have to be topped up through the diet.
omega-3 is important because it helps to make prostaglandins, extremely active hormone-like substances. These have been found to have many important functions for the body, and in the brain they regulate the release and performance of neurotransmitters (chemical substances that transmit nerve impulses).
The two forms of omega-3 - EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are unsaturated and so are prone to damage by cooking, heating and food processing, which is why many people are deficient in these oils.
omega-6 is found in the highest proportion in the brain, of all tissues of the body. Good sources of omega-6, especially gamma-linolenic acid (GLA) are evening primrose oil and borage oil (also known as starflower oil).
To top up your intake of fatty acids, put one measure of sesame, sunflower and pumpkin seeds, and three measures of flax seeds in a jar. Keep the jar in the fridge and simply eat one heaped tablespoon of these seeds, ground first in a coffee grinder (for maximum nutrient benefit), for a good daily intake of your essential fatty acids.
Phospholipids are the 'intelligent' fats in your brain. They help in the production of a substance called myelin, which insulates all nerves and so promotes a smooth running for all signals to the brain. They also help make acetylcholine, the brain's neurotransmitter, as well as supplying nutrients that help to keep the body in balance. Phospholipids enhance mental performance and protect against age-related memory decline.
Although the body can make phospholipids, getting some extra from your diet is even better. The richest source found in foods is from the compound choline, abundant in egg yolks, organ meats and sardines.
Amino acids; the building blocks of proteins, act as brain messengers. Neurotransmitters are built from amino acids, and deficiencies in these powerful molecules can cause depression, apathy, poor memory and concentration. For example, a form of the amino acid tryptophan has proven more effective in double-blind trials that the best anti-depressant drugs.  The amino acid tyrosine improves mental and physical performance under stress better than coffee. 
Neurotransmitters are made directly from amino acids taken into the body from food. From the eight essential amino acids (see article Amino Acids Explained), our body can make the other amino acids needed for the brain, from which neurotransmitters are made.
The best way to tune up your brain is to ensure you have an adequate intake of amino acids in your diet, by eating more protein. The quality of a protein is determined by its balance of amino acids, and the better the quality and 'usability' of the protein you eat, the less you actually need to be optimally nourished.
These are the vitamins and minerals that 'fine tune' your brain, and aid in processes like helping to turn glucose into energy, amino acids into neurotransmitters and simple fats into more complex essential fats.
As you can see, your brain needs a good supply of high-quality foods to ensure it works at its peak, and to protect it from degenerative diseases.