Object exploration, habituation, and response to a spatial change in rats following septal or medial frontal cortical...

Normal rats and rats sustaining septal or medial frontal cortex lesions were compared in experiments dealing with object exploration, habituation, and reaction to novelty (measured by renewed exploration following a spatial change). Normal rats exhibited high levels of initial exploratory activity which decreased over time. Following a spatial change, they reinvestigated both the displaced object and the nondisplaced ones. Frontal animals were similar to normal subjects with respect to their initial exploratory level and habituation pattern. However, frontal rats reexplored only the displaced object and completely neglected the nondisplaced ones. In contrast, the behavioral pattern displayed by septal rats was markedly different from that of normal and frontal animals. Septal rats had lower levels of initial exploratory activity, did not habituate over time, and failed to react to either displaced or nondisplaced objects. These results show that although the septo-hippocampal complex and the medial frontal cortex may share some common function in spatially organized behaviors, both structures have unique roles. Some hypotheses about the possible basic processes subtended by the septal area or the medial frontal cortex are briefly mentioned and discussed.