Role of the medial and lateral septum in a variable goal spatial problem solving task

Abstract

Rats with lesions to the medial (MS) or lateral septal (LS) nuclei were compared to normal controls (CNT) in the acquisition of a spatial working memory task. In this task, animals were first allowed to explore the unbaited three-table apparatus before being fed on one of the two possible goal tables. Animals were then tested on their ability to return to the table where they just had been fed. Only rats with medial septal damage were clearly impaired on this problem, an impairment that dissipated over days. In contrast, the performance of LS rats was not significantly different from controls. During the second phase of the experiment, the same animals received either atropine sulphate (50 mg/kg, IP), atropine methylnitrate (50 mg/kg, IP), or an equivalent volume of saline. Atropine sulphate produced a sharp decrease in performance by all subjects. Meanwhile, atropine methylnitrate produced a mild temporary deficit only in LS rats. Overall, these results confirm that the medial septum plays a crucial role in the acquisition of problem solving. In addition, these results also suggest that the lateral septum may play a possible role in some form of spatial behavior easily disrupted by atropine methylnitrate.