Nonlinear analysis of motion energy calculations in cat visual cortex

The authors have applied a set of one- and two-bar tests to directionally selective (DS) complex cells in the cat´s striate cortex, and also to a motion energy model. Both one- and two-bar responses of DS complex-cells match closely the unidirectional output of the motion energy model, which depends on a squaring operation. It thus appears that DS cortical neurons responding to a moving image calculate a signal very nearly equal to the unidirectional movement energy. The authors consider how the visual cortex could calculate the squaring operation needed for the energy model