Figure 6.
Responses of V1 complex cells to stimuli consisting of spatially superimposed dual gratings. A, Spatiotemporal response surface for the example complex cell used in this figure. Vertical lines indicate the spatial frequencies chosen for the two dual-grating stimuli. B, C, Firing rate as a function of speed for a representative neuron, for pairs of sine-wave gratings of low (B) or high (C) spatial frequencies (sf). The top row of speed-tuning curves show responses to single sine-wave gratings; each panel shows responses to two spatial frequencies. In the bottom row of speed-tuning curves, the open circles show the actual responses to dual gratings of the spatial frequencies used in the companion graphs in the left column, and the filled circles show the predicted firing based on simply adding the responses to the two gratings presented singly. Curves were obtained by fitting Equation 2 to the data. D, E, Population summaries for V1 (D) and MT (E). The scatter plots show the relationship between the predicted and actual preferred speeds for dual-grating stimuli from speed-tuning curves like those in B and C. Open and filled symbols show data for dual-grating stimuli comprising spatial frequencies above and below the preferred spatial frequency of the neuron under study.
