Previously used methods to determine transiency of RGC light responses.

<p><b>(A).</b> modified Sustained-transience index (mSTI) is calculated by dividing the spikes (time stamps of spikes are shown on the top trace) that occur during the second 200 ms after the stimulus onset (dark grey shading) by the spikes corresponding to the first 200 ms of the response (light grey shading). <b>(B).</b> Panel displays the PSTH generated upon light responses of a representative ON-OFF RGC. In case of the ON response of this neuron no spikes are detected during the second 200 ms, thus calculated mSTI values (mSTI = 0) do not reflect response transiency properly. <b>(C).</b> The Tr₂₀₀ measurement is performed by determining the exact time of the response peak (t_peak) and then obtaining the amplitude value of the PSTH curve (A2) corresponding to the time that occurs 200 ms following the peak response (t₂₀₀). <b>(D).</b> The Tr₂₀₀ approach fails to provide a precise transiency value when the response PSTH displays fluctuations, local minimums and maximums. <b>(E).</b> The area measurement approach is performed by a normalization of the PSTH curve and then determining the area outlined by the PSTH curve and the on- (t₀) and offsets (t₅₀₀) of the light stimulus. <b>(F).</b> Contrary to the similar shape of ON- and OFF components of this ON-OFF RGC light response, the area measurement approach provides very different transiency values due to a more robust shoulder for the ON response component. <b>(G).</b> Two OFF RGC PSTHs resulted in similar area summation values, however they displayed very different response characteristics. The onset of the photopic light stimulus is shown by the white bar, whereas the black bar shows light offset in the bottom trace for all panels.