Figure 6.
Spatiotemporal tuning surfaces of MFR, OFR, and motion perception sensitivity. A, A two-dimensional Gaussian surface fitted to the MFR amplitudes for different spatiotemporal frequencies. Fs, Spatial frequency; Ft, temporal frequency. The color indicates the height (MFR amplitude) of the surface normalized by maximum and minimum values in the overall data: dark red, highest; dark blue, lowest. Magenta circles are the data points obtained in the experiment. The VAF was 0.84. The black curves superimposed on the fitted surface represent the data points for the constant stimulus velocities of 4, 10, 20, 60, 100, and 160 °/s. B, Top view of the fitted surface (color contour plot). MFR amplitude along any constant spatial frequency (ordinate) increases as spatial frequency decreases. MFR amplitude increases with temporal frequency until ∼15–20 Hz but decreases thereafter. This trend was also observed in the experimental data in Figure 4C. Small black dots denote the data point on the surface corresponding to the experimental data. C, Color contour plot of the tuning surface of the OFR amplitudes, fitted to the data of Miles et al. (1986). The VAF value was 0.91. D, Color contour plot of the tuning surface of the perceptual contrast sensitivity of visual motion. The VAF value was 0.99. For description of the basis functions fitted to the data, see Materials and Methods. The peak of the sensitivity-tuning surface is clearly different from those of the MFR (B) and OFR (C). In B–D, color indicates the height of the fitted surface normalized by maximum and minimum values in each region: dark red, highest; dark blue, lowest.