Figure 1.

Contrast response and size tuning for a complex cell. A, The response as a function of contrast for a grating of the optimal orientation, spatial and temporal frequency, and drift direction presented in a circular window that was the optimal size for the CRF. Closed circles and error bars indicate average firing rate (mean ± 1 SEM). The solid line is the best-fitting Naka–Rushton function. The arrows show the contrast eliciting 50 (C₅₀) and 90% (C₉₀) of the maximum response of the neuron, which were the contrasts used for subsequent contextual experiments. The dashed line indicates the spontaneous firing rate. B, The response as a function of the radius of the circular window containing an optimal grating as described in A. The arrow shows the smallest window radius eliciting the peak response of the neuron, which is the size of the central patch used in subsequent contextual experiments. C, A full-field optimal grating was presented that included a central gray circular region, where the radius of the central region varied from 0 to 4°, in 1/2 octave steps. The arrow shows the smallest radius of central blank gray region that elicited no response from the neuron. This size was used as the inner radius of stimuli presented to the eCRF and the outer radius of the gray annulus separating stimuli in the CRF from the eCRF (see the configuration in Fig. 2B,C).