The systemic approach to the stability and plasticity of neurophysiological processes during adaptive brain activity.

The problem of the stability and adaptability of regulatory processes is considered, taking as a point of departure N. P. Bekhtereva's theory regarding stable pathological states, and inflexible and adaptable links in control systems. The need to introduce a probabilistic approach is emphasized. Generalizations are made on materials relating to the connectability of the separate components of the biorhythms of functional systems, and to the stability of their amplitude-frequency characteristics. The corpus of facts permitted the successful development in clinical practice of functional biocontrol and feedback.