Gain and stability in cortical microcircuits

Neurons in the cerebral cortex of vertebrates are arranged in functional groupings called cortical microcircuits. The dynamics of such circuits in the visual cortex of turtles have been studied using light intensity step functions. The analyses indicate that the circuits have high feedforward gains. Feedforward and feedback inhibition play important roles in controlling the responses of the circuits to visual stimuli, but are not required for the stability of the circuits because of the stability provided at the front end of the system by microcircuits in the retina.