Читать книгу Noises from the Darkroom: The Science and Mystery of the Mind - Guy Claxton - Страница 27

The brain is the centre where information gathered by the rest of the nervous system, about the state of things both inside and outside the body, is collated and integrated. It is the ‘General Communications Head-Quarters’ of the body. Information continually arrives along all the neural pathways, coded as patterns of electrical impulses. The eyes, ears, tongue and nose bring news of what is happening offshore. Internal monitoring stations tell of the level of blood sugar, the fullness of the bladder, the oxygen/carbon dioxide balance in the lungs, the acidity of the gastric juices…and a hundred other indices of the well-being, or the imminence of required action, in different parts of town. The lookouts have just sighted something – is it the long-awaited supply of fresh meat, or is it that marauding pirate? The miller has more corn to grind than he can cope with: is the store-house full or not? The garbage disposal operatives say it is time to take a dump. The power-station workers are complaining because they have missed their tea-break…All these different ‘interests’ make claims on the attention and orientation of the community as a whole. Cases must be heard, priorities decided, less urgent needs postponed, plans of action prepared.

For example, receptors in the skin, the joints and the muscles tell of aches and pains, pricks and tickles, and update the story about where the limbs are, so that when you need to move, perhaps in an emergency, you already have information about where ‘here’ is, and can therefore compute the arm movement required to get from ‘here’ to ‘there’. A baby reaching for a toy makes a ‘ballistic swipe’: it throws out the hand like a harpoon fired from a ship. If the toy is moved after the movement is started, there is nothing she can do to correct the movement in mid-air. But an older child, whose monitoring of body states and dynamics is more developed, can change the direction of reach immediately. Her hand is now not a simple projectile but a toy-seeking missile, locked on to the target in a much more subtle and responsive fashion. She has learnt how to link the sight of the toy, the sight of her arm, the feel of the arm as it is moving, and the muscular commands that control the arm movement, in a flexible way.

In this chapter I have explained the evolutionary value of plastic brains, and illustrated some of the different jobs that they may be called upon to do. And we have seen how the design function of a brain gets more complicated as the sophistication and differentiation of its body increases. We have developed an overview of what the brain does. But in order to understand it in more detail, we need also to be able to talk about what it is: what it is like, and how it does what it needs to do in order to fulfil its role. This is the subject of the next chapter.