Using the data shown in
Figure 2, we calculated the vectors of the mean amplitudes and phases of the fundamental components at each frequency. The calculated vectors for the three types of mice for temporal frequencies of 5.859, 11.718, 17.578, and 23.438 Hz are shown in
Figure 3. The vectors of the WT mice are shown in black, those for the Pika
−/− mice in red, and those for the mGluR6
−/− mice by blue dotted lines. We assumed that the ON pathway of the WT mice was normal and that the mGluR6
−/− mice completely lacked contributions from the ON pathway. To estimate the contribution of the ON pathway of Pika
−/− mice, we subtracted the vectors of the mGluR6
−/− mice from those of the Pika
−/− mice and examined the residual ON pathway response of the Pika
−/− mice. We also subtracted the vectors of the mGluR6
−/− mice from those of the WT mice to evaluate the normal ON pathway. The obtained vectors for the ON pathway of Pika
−/− and WT mice are shown in pink and green solid arrows, respectively. The differences of phase between Pika
−/− and mGluR6
−/− mice caused by ON pathway functioning in Pika
−/− mice and the reduction of the phase lag between the two types of mice at higher frequencies corresponded to a decrease of the ON pathway in Pika
−/− mice. The lengths of the vectors for the Pika
−/− were much shorter than those for the WT mice, but the ON pathway was detected at frequencies of 5.859 and 11.718Hz. We plot the amplitudes of the calculated vectors for each frequency in
Figure 4. The amplitude of the ON pathway in WT mice was largest (44.85 μV) at a frequency of 5.859 Hz, and it steadily decreased as the stimulus frequency increased. The amplitudes of the ON pathway in the Pika
−/− mice were 5 to 7 μV at frequencies between 3.906 and 15.625 Hz, or 12% to 25% of those of the WT mice. The amplitudes of the ON pathway Pika
−/− mice fell below 3 μV at the higher frequencies of 19.531 to 31.250 Hz, which, as shown in
Figure 2A, is the noise level.