“Let me use a second metaphor. Imagine that you found a tangle of seaweed on the edge of the shore and lifted it. The heaviest parts rest on the sand in a mesh, but some skeins extend vertically. This neural network is shaped like that: it looks like a tangled skein of a hundred thousand golden threads that has been drawn upward. The mass of it gathers in the pelvis, but strands from the same network extend upward to the spinal cord and brain.”