The chaotic component of the high-frequency EEG of the rabbit cortex was studied during the development of a conditioned defensive reflex to nonrhythmic light stimulation with electric reinforcement applied to the animal's paw. Regular changes in the dynamic parameters of the chaotic component of the high-frequency EEG were demonstrated. Characteristic changes in the asymptotic evaluations of the correlational dimensionality of the attractor of the chaotic component (DCC) of the high-frequency EEG were detected in the cortical regions studied both during the action of the conditioned stimulus and in background conditions before presentation of combinations. These changes affected both the afferent and efferent cortical regions of the conditioned reflex arc, as well as regions not directly addressed by the conditioned or unconditioned stimuli. These results allow the dynamics of changes in the morphofunctional structures of the conditioned reflex to be seen at the cortical level during learning. Significant differences in the early and late stages of conditioned reflex formation were detected.