Bilateral ablation of the frontal parts of the neocortex and the hippocampus enhances the rats' reactivity to artificial stimuli (light and sound), and at the same time diminishes their sensitivity to signals of defensive excitation in another individual. Simultaneous bilateral ablation of the frontal neocortex, the lateral and ventromedial hypothalamus enhances in equal measure the rat reactivity to light, sound and the partner's pain cry. Comparison of the results with facts previously obtained and with published data suggests that individual correlations of the "information system" (the frontal neocortex and the hippocampus) with the "motivational system" (the amygdala and hypothalamus) underlie the extra-introversy parameter. Correlation between the "frontal neocortex--hypothalamus" and "hippocampus--amygdala" systems is manifested on the neuroticism (emotionality) scale. Activity of the "hypothalamus--hippocampus" system is of great importance for the lability versus inertia factor. The different forms of disturbance of normal interaction of the above four brain structures are likely to determine the basic varieties of neuroses.