The effect of the functional state of some thalamic and hypothalamic nuclei, modified by anode polarization, on spatial synchroneity of cortical potentials (SSCP) and the speed of elaboration of a conditioned defensive reflex (CDR) were studied in chronic experiments on 15 rabbits. Reversible blockade of the studied subcortical structures considerably affected the local SSCP form and the reflex execution. In intrasignal periods the global SSCP practically did not change. A comparative analysis of the results permits an assumption that the mammillary bodies play an important role in the formation of local SSCP at the beginning of defensive conditioning and that in the stabilized reflex, this SSCP form requires the activity of non-specific thalamic nuclei.