The effects of septal and olfactory bulb lesions on stimulus reactivity

Abstract

The present investigation was concerned with the reactivity of rats with septal lesions and rats with olfactory bulb lesions to sensory stimulation. The investigation consisted of five independent experiments, each concerned with a different sense modality. It was found that septal rats were hyperreactive to thermal stimulation, sound stimulation, and shock stimulation. Since previous research has shown that septal animals are hyperreactive to taste stimuli and light stimulation it was tentatively concluded that septal rats are hyperreactive to most forms of sensory stimulation. This finding was offered as an explanation of many of the phenomena associated with septal lesions reported in the literature, such as hyperemotionality and changes in avoidance behavior. It was also found that septal rats were quite able to inhibit these responses in the tasks used and the explanation that septal lesions destroy some inhibitory mechanism was not supported by these studies. In the anosmic animal the results are not clear. The anosmic appears hyperreactive to heat, shock, and possibly light, but not to sound, or taste stimuli. Much more research is needed with anosmics before even tentative generalizations can be made regarding their reactivity to sensory stimulation. It does appear, however, that the anosmic has difficulty in inhibiting his responses. In nearly all of the escape tasks the anosmic animals had the shortest latencies in extinction. A number of improvements in methodology were suggested for future research.