Approach-avoidance dissociations in rat brain

Two electrode pairs were implanted in each rat, one in dorso-medial tegmentum or medial hypothalamus and one in lateral hypothalamus. Four sequential tests were repeatedly administered in a two-pedal Skinner box: hypothalamic self-stimulation, tegmental self-stimulation, hypothalamic escape, and tegmental escape. Results indicate that with electrodes in medial forebrain bundle regions of hypothalamus, there is self-stimulation but no escape; with electrodes in dorso-medial tegmentum, there is escape but no self-stimulation. In both cases, this holds for all suprathreshold stimulus levels. With electrodes placed more medially in hypothalamus, or lower in tegmentum, the same electrode may yield both self-stimulation and escape depending on the nature of the test.