Figure 11.
A, Phase functions of neuron shown in Figure 2. Phase, derived from SVD (see Fig. 7B), plotted as a function of velocity and density. For both directions, slopes correspond to temporal position (group delay) and spectral position (BF), see Equation 7. Phases for downward/upward sweep directions, χdown and χup, consist of temporal and spectral parts, θ and ϕ (Eq. 8). In this example, χdown = 0.88π − 0.81π = 0.07π and χup = −(−0.51π − 1.19π + 2π) = −0.30π, thus ϕ = (χup + χdown)/2 = −0.36 = −21° and θ = (χup - χdown)/2 = −0.57 = −33°. B, Temporal positions, or group delays, for upward versus those for downward sweep direction. C, Differences of group delays for upward and downward as shown in B, as a function of direction selectivity D. D, Spectral positions for upward versus those for downward sweep direction. The spectral positions are between −1.25 and 1.25 octave. When the difference between the two positions is >1.25 octave, a 2.5 octave correction is made. The diagonal in B and C represents the y = x line. E, Distribution of temporal phase constant θ (−180° < θ < 180°). F, Distribution of spectral phase constant ϕ (−90° < ϕ < 90°).