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Neuroscience & Karma
skin, or of the operations of some internal organ(s) of the body. The disordered signals serve to symbolize that something is wrong and this sets off the programs that may put it right, which in man may be very complex. Pain may initiate the brushing away of a wasp, or be the stimulus for the foundation of a research institute for the treatment of cancer. 4. Seeing A. Structure of the EYE
Although seeing is not like photography, we shall begin by saying that the eye is, in some ways, very much like a camera. It has a lens and a diaphragm (the iris) and a focusing device. What is more, the first step in the process of vision is a photochemical cbange somewhat like that in a photographic plate. The retina contains a mosaic of more than one hundred million separate receiving elements of two sorts, the rods and cones, each of which detects a tiny part of the image that is thrown on it by the lens, producing a minute electrical or chemical change. Only the cones are sensitive to colors and most of them are concentrated near the centre of the eye. Here there is a small area, the fovea, containing only about 30,000 receptive cones. These perform nearly all the detailed work of seeing, except in dim light. In order to see things, we have, therefore, continually to explore them by minute movements of the eyes around them, examining the part we want to see by the fovea. This is of fundamental importance for oursystem for thinking about vision because the program that control these eye-movements, largely determines what we see. B. VISION
Vision is not like taking a series of photos but is part of a whole lifesystem. Thus vision is a dynamic process, using a series of scans, but these are not rigidly determined as in a television raster. They are varied according to the nature of the scene itself and the previous experience of the individual. Moreover the scanning does not work by converting the information in the spatial scene into a single channel, but puts it into many parallel channels, which maintain the spatial relations, so in a sense
