The existence of a layer IV in the rat motor cortex

We have reconstructed the laminar pattern of rat primary motor cortex (Fr1)using a computerized analysis system based on the so-called 'opticaldissector'. Data were visualized on a graphics terminal. In contrast tocurrent views, which state that there is no prominent layer IV in the motorcortex of the rat, our method of analysis revealed a genuine layer IVconsisting of densely packed small neurons.