Responses of tectal neurons to three different types of visual stimuli.

<p><b>A₁.</b> Mean responses (n = 3) to grating motion (red), motion of a random dot pattern (blue) and counterphase flicker of the grating (black) of the neuron shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062846#pone-0062846-g003" target="_blank">Figure 3</a> (ex1) in eight different directions (0°–315°). <b>A₂</b>. Polar plots for the three different types of visual stimuli shown in A₁. The plot shows the mean amplitude of the responses with the shaded areas indicating one standard deviation. The neuron had a clear and significant directional tuning for both, the moving random dot pattern (blue) and the moving grating (red), but was unselective for the orientation of the flicker stimulus. Throughout the figure, responses to grating motion are shown in red, responses to motion of the random dot pattern are shown in blue, and responses to counter-phase flicker are indicated in black. Note that for uniformity with the motion stimuli each of the four different flicker conditions is represented by pairs of opposite “directions”, e.g. 0° and 180° both denote flicker of a grating with vertically oriented bars (compare <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062846#pone-0062846-g001" target="_blank">Figure 1C</a>). <b>B</b>. Example from a second neuron in the same preparation (see white square in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062846#pone-0062846-g003" target="_blank">Figure 3A</a>, ex2). As in A₁–A₂, this cell was directionally selective but with a different preferred direction (290°) and was non-selective for the orientation of the flicker stimulus.