The change in the neuronal activity of the sensorimotor area of the cerebral cortex of the cat was investigated in awake animals as a function of the level of differentiation of the components of a simultaneous heteromodal complex stimulus. Two groups of neurons in the sensorimotor cortex were distinguished on the basis of the character of this relationship and a number of other parameters. It was shown that the parameters of the reactions of all neurons recorded to the positive conditional stimulus following the consolidation of the conditioned motoric reaction are established first. Suchparameters of the responses as degree of manifestation, intensity, duration, and the length of the latent period changed in the process of development. The reactions of neurons of both groups to inhibitory signals were stabilized only after the consolidation of the differentiation skill. In the process only the pattern of the discharge changed in the neurons of the first group, while in the neurons of the second group, the degree of manifestation of the response, its sign, duration, and length of the latent period could vary. Fluctuations in the level of differentiation following the development of the inhibitory conditioned reactions had an effect only on the responses of the neurons of the second group to the components of the complex.