Figure 3.

Interpretation of the feature pooling field radius. The feature pooling field in the fwRF model specifies the pooling radius (σ_g) over feature map pixels (feature map illustrated as blue plane; pixels indicated by pink grid; feature pooling field illustrated as black dashed circle). The pixels in a feature map (two pixels are labeled by black dots) have their own intrinsic scale that is specified by a pooling radius (σ_f, solid gray circles in white plane) over pixels in the stimulus (white plane). Assuming that both the feature pooling field and the pooling field of the feature map pixels are Gaussian, an estimate of the square of the population receptive field radius (σ_pRF, large solid black circle in the white plane) can be obtained by summing the square of the feature pooling field radius with the square of the pooling radius of the feature map pixels.