Figure 1.

Assay for the spatial dissection of the thermal noxious response. (A) Schematic of the localized thermal pulse assay. (B) An infrared laser pulse with a 220 um beam diameter (full width half maximum) was used to locally stimulate the entire worm from head to tail, N = 442. The head (1–10), midbody (16–26), and tail (31–41) regions are demarcated using the 41 points along the entire “skeleton” of the worm body. An example of the selective targeting of the head is shown. The probability of the first behavioral state after the laser pulse is shown for head, midbody, and tail regions. The head, midbody, and tail responses are statistically different, p < 0.001, Fisher’s exact test. (C) Raw video data of the worm after a head-applied laser stimulus is shown as a time-lapse sequence. After the laser pulse is applied, the worm enters a reversal (red), followed by an omega turn (green), and then resumes its forward motion (blue). (D) Thermal profile of 133 ms IR pulse measured using a thermal camera for three pulse amplitudes (60, 100, and 150 mA), where the largest full width half maximum (FWHM) was measured to be 220 μm for the 150 mA laser pulse.