Fig. 1.

Effect of stimulus energy and stimulation site on nocifensive behaviors. Stimulus-induced nocifensive behaviors were quantified as follows: no movement (score = 0), head turning (including shaking or elevating the head; score = 1), flinching (i.e., a small abrupt body jerking movement; score = 2), withdrawal (i.e., paw retraction from the laser stimulus; score = 3), licking and whole body movement (score = 4). Behavioral scores are significantly modulated by stimulus energy (F = 161.2, p < 0.001), but not by stimulation site (F = 1.94, p = 0.14). Colored lines represent single-animal behavioral scores.