Neuronal responses to plaids

The majority of neurons in the visual cortex are orientation selective. When presented with a plaid, i.e. a stimulus generated by adding two gratings of different orientations, these neurons respond to the individual gratings making up the plaid. However, there are some pattern selective neurons in Area MT of the monkey visual cortex which respond in accordance with the combined plaid. The present study used computer simulation to investigate the response properties of simulated MT neurons to orthogonal plaids. The MT neurons were simulated by first multiplying the outputs of conventional orientation selective V1 neurons and then normalizing the product. It was discovered that pattern selective responses may emerge when the outputs from two orientation selective neurons, which differ in optimal orientation by more than about 50 degrees, are combined in this manner. This demonstrates that pattern selectivity may be the result of a very simple although nonlinear mechanism.