The role of the septal complex in the modulation of emotion
A great amount of research has implicated the septal complex as being involved in emotional processes. The nature of this involvement, though, is not well understood. In most tasks, septal function is assessed with a single cue being the discriminating or conditioned stimulus. Contextual cues, though, are able to serve as a discriminatory cue or conditioned stimulus as well. The present thesis sought to examine the possible involvement of the septal complex in the emotional processes which involve contextual cues. In the first experiment (1), the effects on fear responses elicited by contextual and phasic conditioned stimuli (CS) were examined in animal with septal damage. Septal lesions were found to potentiate the conditioned fear response elicited by the contextual cue, but not those elicited by the CS. This effect was shown to be attributed to the medial nucleus of the septum (experiment 2). In the subsequent experiments, a novel context was found to be able to elicit fear responses in animals with lesions of the septal complex that had been previously conditioned (experiment 3a), and this effect was shown to be due to the previous conditioning and not due to the novelty (experiment 3b). In addition, lesioned animals were found to not exhibit a decrease in responding to a CS that was presented in a novel context, an effect observed in control animals (experiment 3a). Septal damage also was found to have varying effects on the responding elicited by the CS when the CS was presented alone before training (experiment 4). Finally, the effects of lesions of the septal complex were diminished when the fear levels in the task were low (experiment 5). These data indicate that the effect of damage of the septal complex varies, and is dependent on the demands of the task. These results are discussed in terms of the role that the septum may play in the control of emotions in times of high risk or danger.