Figure 7.

The vertical extent of a small stimulus. (A) The doublet pairs presented using the whole-screen mode. The doublet pair has the same width as before, but is now only 1° high, just below the size of an individual ommatidium. (B) Intracellular HS neuron response to the doublet pair shown in A, as it passes through the receptive field in the preferred direction (blue = decreasing contrast, red = increasing contrast). (C) The mean response to the doublets as shown in part B. N = 1, n = 9 (t-test done across repetitions in the single neuron, errorbar calculated across n). NS, no significant difference (Student's t-test). (D) The doublet is now 1.8° high. (E) Intracellular HS neuron response to the doublets as they pass through the receptive field in the preferred direction. (F) The mean response to the doublets moving in the preferred and anti-preferred direction. N_pref = 4, n = 135. N_null = 1, n = 20 (t-test done across repetitions in the single neuron, errorbar calculated across n). ^*Indicates a significant difference (p < 0.05, Student's t-test). NS, no significant difference (Student's t-test). (G) The average response difference between the increasing and decreasing contrast pairs as a function of their vertical extent. A positive difference indicates that the response to the increasing contrast ensemble is larger. N = 1, N = 8 (errorbars calculated across n).