1. What is the brain?
The brain is simply a collection of neurons (nerve cells) and other cells, gathered together in one place to simplify the wiring. A brain can be just a handful of cells, as found in some simple invertebrates, or billions, as in humans.
2. What does it do?
It allows animals to adapt their behaviour to changes in the environment, on a much quicker timescale than evolution. It helps them collect information, act on that information and store the result for future reference - in other words, it is a sensory system, a motor system and a memory.
3. What is special about the human brain, compared to the brains of other primates?
Human brains, particularly the cerebral hemispheres are bigger and better developed than in other primates. The frontal and prefrontal lobes of the cerebral hemispheres deal with complex kinds of thought and social interaction, such as planning, decision making, empathising, lying, and making moral judgements. But corrected for body size, the differences are surprisingly small.
The difference between a human brain and a chimp or gorilla brain seems to be largely the way neurons are connected. Humans have several unique genes that seem to control nerve cell migration as the brain develops, and different patterns of gene expression in the brain. So, the machinery doesn't look that different, but it certainly works differently.
As for non-primates - other mammals have smaller brains, with less well developed frontal lobes. Further down the evolutionary tree, animals lose the cortex altogether, with reptiles having a brain that resembles just our own brainstem. In simple animals, the brain becomes more of a swelling at the top of the nerve cord or around the mouth area.
4. How does the human brain think and solve problems?
All brain activity takes place as electrochemical signals. The signals form within neurons, pass along the branch-like axons and - by the release neurotransmitter chemicals - they jump from one neuron to the next across gaps called synapses.
The pattern, size, shape and number of these signals, what they communicate with, and the region of the brain in which they happen, determine what they achieve. It's a bit like the wiring and components of a computer and the sequence of coded 1s and 0s it uses, only far more powerful.
Most people define thought as an active and conscious brain activity - in other words, a brain signal we are aware of. No one knows why some brain signals, such as those controlling our muscles or heart beat are completely subconscious.
Solving problems can happen in two ways. It can be a type of thought or calculation - pulling information from memory, filtering new information, combining it all and weighing up alternatives. Or it can be a gut instinct - a decision made by the more primitive emotional part of our brain, like the mental equivalent of a reflex.
The most creative problem solving can be a long term process of both mulling things over in thought and in our unconscious mind, with the answer finally popping out.
5. How are memories stored in the human brain?
There are several types of memory - for facts, skills or events - and several brain areas devoted to it.
At a neuronal level, memory is any change that increases the chance of a signal passing along a particular pathway, or that increases the size or strength of this signal. At first the change can be a simple increase in the amount of signalling chemical released. Gradually, the connections are built up physically with more and bigger synapses. Eventually more branches may form.
For these more permanent changes, genes become active and produce building materials to form the structural changes. But memories are never stored in an immutable form - they are continually being changed and reactivated.
6. Is language hardwired into the brain?
Some people argue yes, others no. Linguist Noam Chomsky famously argued that it was hardwired - that all babies are born with the nuts and bolts of language and grammar rules.
Other researchers say that language and its rules are all picked up through experience - a process called statistical learning. They believe that the brain is born naïve, and learns through example.
Yet others believe the truth lies somewhere in between. Under this scenario, we are all born with a hardwired ability to pick up language and to extract rules from examples, but that the words, concepts, syntax and grammar are all learned.
7. What do alcohol and drugs do to our brains?
They enter the brain and interfere with the normal signalling mechanisms. Often drugs of abuse are very similar to one of the natural neurotransmitter chemicals. Marijuana contains compounds similar to our natural cannabinoids, morphine and heroin mimic our natural pain-killing opiods, amphetamines and cocaine tinker with dopamine and serotonin signalling.
They can either mimic, block or extend the usual signals, hence the wide variety of sensations and behaviours they lead to. All drugs of abuse have some effect on our dopamine and opioid systems, which provide some of our sense of pleasure and reward. This means the reward system can be corrupted into addiction by drug use over extended periods, or in people with certain genetic predispositions.
8. Is it true that we only use a small amount of our total brain capacity?
At any one time, yes. Some people say 10%, others say 1%. But every part of the brain has a function, so we get round to using it all at some time.
And it's not as though using more of our brain at one time would necessarily make us smarter. In fact it would be disastrous - something like a massive epileptic fit.
Certainly there's no simple relationship between how much brain activity there is and how intelligent we are. When people are being creative, their brain waves are actually quieter than less creative types, and the better you are at something, the less brain activity there needs to be.
9. What are dreams?
Dreams are a type of brain activity occurring during or near sleep. The most vivid seem to happen during a sleep stage called REM (rapid eye movement). Emotional, visual and other sensory areas are very active during dreams, and many researchers think that they might be a kind of "offline" filing, sorting and consolidation time for the brain.
10. Could you build an artificial human brain?
No - at least not yet. There has been some success at mixing electronics with real cells. Some experiments have got real-looking signals to come in and go out of artificial brains, and even to result in learning.
Devices similar to pacemakers can substitute for simple functions or control epilepsy, and prosthetic sensory systems can give some sensation back. But the fundamental complexity of the human brain is so great that no electronic system could currently come close.
11. What is consciousness?
This is the biggest mystery in the study of the human brain. Consciousness is the opposite of the subconscious. It is a state of wakefulness and awareness, but also more, in that it also includes our sense of self, a feeling of embodiment and of having a sense of a personal history - a "stream of consciousness".
Wondering why people have a clear sense of themselves has long been the realm of philosophers,. But more recently, brain researchers have sought to identify regions of the brain that correspond to consciousness.
However, even if they can identify the regions, or types of brain activity, that differ between conscious and subconscious states, the problem of why pulses of chemical and electrical signals can feel like anything at all, remains.
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