The wiring of our brain looks a bit like the logic circuits of a

The Brain 99 The wiring of our brain looks a bit like the logic circuits of a computer, and our best guess is the cells in our brain form some kind of computer. The brain cells — a specialized form of nerve cell — connect to the rest of the body via the nerve cells that largely run down our spine. Thoughts trigger action and, in reverse, the nerves in our extremities sense things in the environment and relay information back to the brain. If I think, ‘move my finger’ my finger will move, and if it touches something I will feel the sensation. Interestingly if my finger touches something hot a reflex will kick in. Reflexes work without involving the brain. We don’t have to think, “that hurts” Instead, our finger reflexively pulls away. We may say ouch, but by the time we do, our fingers already moved away from the heat. Nerve cells are much slower than the electronic systems we build with copper and silicon. This speed is quite noticeable and limits the rate we can do certain things. It takes around 0.08 seconds for a nerve impulse to run down to the tips of our fingers, initiate an action and return to give us the sensation of the action. This may sound fast but if you're a tennis player in a rally or a pianist faced with a fast passage, the nerves don't have time to make a full round trip signal before the next action must be initiated. In these instances we need to run on autopilot and there are parts of the body where the nervous system takes action without the brain getting involved. This is particularly the case with things like walking and balance, which must respond fast to changes in ground conditions. The signals just don’t have time — and don’t need — to go all the way up to the top of the body for instructions. Rather like the heat reflex above, the peripheral nervous system can process information locally. After all, brain cells and nerve cells are really all one type of cell. If you have a group of people, you can conduct a fun experiment to show the speed of nerves. Hold hands in a big circle and squeeze the hand of the person next to you. When they feel you squeeze, they should squeeze the next person’s hand and so on. The rate at which people squeeze hands around the circle is limited by the speed at which nerves conduct the signals across our bodies. Imaging the Brain There are several ways to look inside the brain without recourse to a bone saw. The methods are fascinating in their own right, even before we start looking at the results. Each image is generated using a different physical principle. HOUSE_OVERSIGHT_015789