Your brain uses less power than your refrigerator light

The brain uses 12 watts of power. Over the course of a day, your brain uses the amount of energy contained in two large bananas. Curiously, even though the brain is very efficient, it's an energy hog. It is only 3 per cent of the body's weight, but consumes 1/6 (17 per cent) of the body's total energy. Most of its energy costs go into maintenance; the added cost of thinking hard is barely noticeable.

Frequent jet lag can damage memory

Jet lag is not simply annoying; in repeated doses it can be dangerous to your brain's health. People who often cross many time zones can experience brain damage and memory problems. This probably results from the stress hormones released during jet lag that are known to damage the temporal lobe and memory. You probably don't need to worry because, unless you work for an airline, few people fly across multiple time zones more often than every two weeks. Shift workers are more likely to be at risk. Like repeated jet travel, frequent drastic changes in working hours are likely to cause stress on the body and brain.

Why you can't hear phone conversations in a noisy room

Talking on your mobile phone in a noisy place can be difficult. Your mobile makes the brain's task harder by feeding sounds from the room you're in through its circuitry and mixing them with the sound it gets from the other phone. This makes it a harder problem for your brain to solve because your friend's transmitted voice and the room noise are tinny and mixed together in one source. Cover the mouthpiece when you're trying to hear your caller and you'll stop the mixing.

Shoot-'em-up video games can help you to multitask

Sustained multitasking increases your ability to pay attention to many things at the same time. A significant source of practice is playing action video games where the aim is to shoot as many enemies as possible before they shoot you. These games make you distribute attention across the screen, and quickly detect and react to events. Playing Tetris (an early puzzle-based video game) doesn't have the same effect, perhaps because you have to concentrate on only one object at a time, rather than multitask. Does this mean that you should encourage your kids to play shoot-'em-up action games? We wouldn't go out of our way to expose kids to violent images, but at least you can take heart that video game-playing has positive effects.

The brain has a joke centre

Humour is hard to define, but we know it when we see it. One theory suggests that humour consists of a surprise - we don't end up where we thought we were going - followed by a reinterpretation of what came earlier to make it fit the new perspective.

To make it a joke instead of a logic puzzle, the result needs to be a coherent story that isn't strictly sensible in everyday terms. Some patients with damage to the frontal lobe of their brain, particularly on the right side, don't get jokes at all. Typically, this is because they have trouble with the reinterpretation stage of the process. For instance, given a joke with a choice of punchlines, they can't tell which one is funny.

There's a reason you remember those annoying songs

Having a song or, more often, part of a song stuck in your head is incredibly frustrating. But sequence recall has a special and useful place in our memories. We constantly have to remember sequences, from the movements involved in signing our name or making coffee in the morning, to the names of the exits that come before the motorway turn-off we take to drive home every day.

The ability to recall these sequences makes many aspects of everyday life possible. As you think about a snippet of song or speech, your brain may repeat a sequence that strengthens the connections associated with that phrase. In turn, this increases the likelihood that you will recall it, which leads to more reinforcement.

You could break this unending cycle of repeated recall and reinforcement - which may be necessary for the normal strengthening and cementing of memories - by introducing other sequences. Thinking of another song may allow a competing memory to crowd out the first one: find another infectious song and hope that the cure doesn't become more annoying than the original problem.

Sunlight makes you sneeze

Many people sneeze when they look into bright light. Why would we have such a reflex and how does it work? The basic function of a sneeze is fairly obvious: it expels substances or objects that are irritating your airways. The sneezing centre is located in the brainstem, in a region called the lateral medulla; damage to this site means that we lose the ability to sneeze.

Sneezing usually is triggered by news of an irritant that is sent through brain pathways and into the lateral medulla. This information gets to the brain from the nose through several nerves, including the trigeminal nerve, which carries a wide variety of signals from the face into the brainstem. It's a really crowded nerve, which might explain why bright light could induce a sneeze. A bright light, which would normally be expected to trigger pupil contraction, might also spill over to neighbouring sites, such as nerve fibres or neurons that carry nose-tickling sensations.

Bright light isn't the only unexpected sensation that is known to trigger sneezes; orgasm can also trigger sneezes in men. Fundamentally, a crossed-wire phenomenon, like the photic sneeze reflex, is possible because the circuitry of the brainstem is a jumbled, crowded mess.

You can't tickle yourself

When doctors examine a ticklish patient, they place his or her hand over theirs to prevent the tickling sensation. Why does this work? Because no matter how ticklish you may be, you can't tickle yourself.

This is because your brain keeps your senses focused on what's happening in the world; important signals aren't drowned out in the endless buzz of sensations caused by your actions. For instance, we are unaware of the feel of a chair and the texture of our socks, yet we immediately notice a tap on our shoulder.

To accomplish this goal, some brain region must be able to generate a signal that distinguishes our touch from someone else's. The cerebellum, or “little brain”, may be the answer. It is about 1/8 of our total brain size - a little smaller than our fist - and weighs about 4oz (113g). It is also the best candidate that scientists have for the part of the brain that predicts the sensory consequences of our own actions.

The cerebellum is in an ideal location for distinguishing expected from unexpected sensations. If a prediction matches the actual sensory information, then the brain knows that it's safe to ignore the sensation because it's not important. If reality does not match the prediction, then something surprising has happened - and you might need to pay attention.

Yawns wake up the brain

Although we associate yawning with sleepiness and boredom, its function appears to be to wake us up. Yawning expands our pharynx and larynx, allowing large amounts of air to pass into our lungs; oxygen then enters our blood, making us more alert. Many vertebrates do it, including all mammals and perhaps birds. It also has been observed in human foetuses after just 12 weeks of gestation. In non human primates, it is associated with tense situations and potential threats.

Think of yawns as your body's attempt to reach full alertness in situations that require it. They are contagious, as anyone who has attempted to teach a roomful of bored students knows. No one is sure why, though it might be advantageous to allow individuals quickly to transmit to one another a need for increased arousal. They are not contagious in non primate mammals, but the ability to recognise a yawn may be fairly general: dogs yawn in response to stressful situations and are thought to use yawning to calm others. You can even sometimes calm your dog by yawning.

Altitude makes the brain see strange visions

Many religions involve special visions that occurred at great heights. For example, Moses encountered a voice emanating from a burning bush on Mount Sinai and Muhammad was visited by an angel on Mount Hira. Commonly reported spiritual experiences include feeling and hearing a presence, seeing a figure, seeing lights (sometimes emanating from a person) and being afraid.

Similar phenomena are reported by mountain climbers, a group generally not thought to be very mystical. Could it be something about the mountains? Acute mountain sickness occurs above altitudes of 8,000ft (2,400m). Many of the effects are attributable to the reduced supply of oxygen to the brain. At 8,000ft or higher, some mountaineers report perceiving unseen companions, seeing light emanating from themselves or others, seeing a second body like their own, and suddenly feeling emotions such as fear. Oxygen deprivation is likely to interfere with brain regions active in visual and face processing, and in emotional events.

© Sandra Aamodt and Sam Wang 2008 Extracted from Welcome To Your Brain: The Science of Jet Lag, Love and other Curiosities of Life (Rider Books, £12.99). Available from Times Books First for £11.69, p&p free. Phone 0870 1608080 or visit timesonline.co.uk/booksfirst

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