TIME (s) TIME (s) FIG. 4. Increases in the responses of a primate STT neuron to knee flexion and to mechanical stimulation of the skin during the development of acute arthritis. The drawing shows the sites on the skin that were stimulated. The receptive field increased in size as arthritis developed following injection of a mixture of kaolin and carrageenan into the knee joint. The histograms show the enhanced background activity, increased responses to knee flexion, and increased responses to BRUSH and PINCH of the skin. (From ref. 23.) Click here to see the graphic at a different resolution