Steven Pinker -- How the Mind Works - Hampshire High Italian ...

The Mind's Eye 287One can even make an educated guess about the anatomy of mentalimagery. The incarnation of a 2V2-D sketch in neurons is called a topographicallyorganized cortical map: a patch of cortex in which each neuronresponds to contours in one part of the visual field, and in whichneighboring neurons respond to neighboring parts. The primate brainhas at least fifteen of these maps, and in a very real sense they are picturesin the head. Neuroscientists can inject a monkey with a radioactiveisotope of glucose while it stares at a bull's-eye. The glucose is taken upby the active neurons, and one can literally develop the monkey's brain asif it were a piece of film. It comes out of the darkroom with a distortedbull's-eye laid out over the visual cortex. Of course, nothing "looks at" thecortex from above; connectivity is all that matters, and the activity patternis interpreted by networks of neurons plugged into each corticalmap. Presumably space in the world is represented by space on the cortexbecause neurons are connected to their neighbors, and it is handy fornearby bits of the world to be analyzed together. For example, edges arenot scattered across the visual field like rice but snake along a line, andmost surfaces are not archipelagos but cohesive masses. In a corticalmap, lines and surfaces can be handled by neurons that are highly interconnected.The brain is also ready for the second computational demand of animagery system, information flowing down from memory instead of upfrom the eyes. The fiber pathways to the visual areas of the brain aretwo-way. They carry as much information down from the higher, conceptuallevels as up from the lower, sensory levels. No one knows what thesetop-down connections are for, but they could be there to download memoryimages into visual maps.So mental images could be pictures in the head. Are they? There aretwo ways to find out. One is to see if thinking in images engages thevisual parts of the brain. The other is to see if thinking in images worksmore like computing with graphics or more like computing with a databaseof propositions.In the first act of Richard II, the exiled Bolingbroke pines for his nativeEngland. He is not consoled by a friend's suggestion to fantasize that heis in more idyllic surroundings: