Topic: feature processing

The mapping from the visual field to V1 can be approximated by a log-polar transform. In this domain, scale is a left-right shift, and rotation is an up-down shift. When fed into a standard shift-invariant convolutional network (CNN), this provides scale and rotation invariance. Remarkably, despite the property of rotation invariance, this model provides a novel explanation for the inverted face effect. The effect comes about because, while the scale shift maps directly onto the flat cortex, rotation, as a circle group, does not. When the face is inverted, the features simply shift up and dow