FIGURE 11-21 Pain Gate A spinal cord interneuron receives excitatory input (plus signs) from the fine-touch and pressure pathway; and inhibitory input (minus signs) from the pain and temperature pathway. The interneuron’s relative activity then determines whether pain and temperature information ascends to the brain.

Information from R. Melzack (1973). The Puzzle of Pain (p. 154). New York: Basic Books.