Figure 3.

AFD neuronal activity in unrestrained worms navigating spatial thermal gradients. A, The undulating path of an unrestrained worm crawling ∼8 mm on a spatial temperature gradient in the vicinity of T*_AFD. The color and position of each data point represent the ratiometric emission signal and position of the AFD thermosensory neuron of the moving worm, respectively. The black circle indicates initial position. To indicate scale, the gray silhouette shows the approximate relative size of the worm body. B, The top and bottom panels show the time-varying temperature at the worm's head and the ratiometric emission signal from AFD for the data shown in A. C, A compilation of data showing the ratiometric emission signals for worms cultivated at 20°C navigating spatial thermal gradients at different absolute temperatures from ∼15 to ∼25°C. The ratiometric emission signal exhibits position dependence only at temperatures above ∼17°C (i.e., T > T*_AFD). A black circle indicates the initial position of each data trace.