Response to periodic inputs—DA model predictions.

<p>Parameter set B was used for theory curves in this figure (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003289#pcbi-1003289-t002" target="_blank">Table 2</a>). (A) Traces of model responses (thin lines) to 25%, 50%, and 100% contrast sinusoidal inputs with frequencies 0.1, 1.25, 2.5, and 5 Hz, superimposed on a background light intensity of 3.6·10⁵ photons/µm²/s. The thick line represents the input. The abscissae are scaled so as to allow for two periods. Horizontal lines for each trace represent the potential when the input sinusoid has 0 amplitude. (B) ‘Effective gain’, calculated as the ratio of the trough-to-peak amplitude of the response to the through-to-peak amplitude of the input. Different colors correspond to different background intensities, varying from 360 to 7.2·10⁵ by factors of ∼2. At low input contrast (thin lines), the DA model behaves as a band-pass filter, while at high input contrast (thick lines) it behaves nearly as a low-pass filter.