Fig. 3. Directional tuning curve for interneuron 10-2a. (A) Single puffs of air from eight different directions relative to the cricket (top traces) elicit various patterns of spiking activity (bottom traces) in an interneuron of class R10-2a. Scale bar: x 10 ms, y 875 mm s^–1 (stimulus)/10 mV (intracellular membrane potential). (B) To generate the tuning curve the same cell as in A was presented with 10 stimuli from each of 24 different directions in the horizontal plane (15° separation between samples). The number of spikes elicited in the 60 ms window following stimulus onset was counted for each trial, and mean and s.d. across trials is shown as a function of stimulus direction. The spontaneous firing rate of the cell was also determined, and the gray broken line shows the expected number of spontaneous spikes in a 60 ms window. Note that stimuli from angles –15° to 105° inhibit the firing activity of this cell below the spontaneous rate, which can also be seen as a slight hyperpolarization in the membrane potentials of A. (C) The mean values from B, plotted in polar instead of Cartesian coordinates.