The chapter considers the problem of the functioning of the human operator in the structure of modern human–machine systems. The directions of automation and increasing human responsibility for decisions made based on the results of analyzing heterogeneous information in real time are discussed. It is shown that a human operator managing a complex human–machine system faces new problems, trying to understand the current situation and make effective decisions in conditions of increased information load and time pressure. In this regard, there has been an increase in demands on a person’s cognitive abilities, the content and properties of his mental models. Directions for research and analysis of mental models are highlighted in order to increase the efficiency of the human operator. A conceptual approach to the mathematical formalization of mental models of a human operator in terms of influencing decisions has been developed. The analysis of the features of human mental models is carried out and three groups of properties of these models that influence decision-making are formed. A technical implementation of the functions of a human operator, based on a synergetic neural network with the considered properties of mental models, is proposed. The parameters of the neural network in solving the problem of recognizing a situation are explained. It is shown how the presented model reflects the properties of mental models that influence decision-making.