The present proposal is directed at understanding the connections of cholinergic cell groups in the basal telencephalon of turtles. These cell groups have recently been identified and have been shown to resemble the cholinergic cell groups of the basal forebrain of mammals in their location, histochemistry, and known projections. The basal forebrain cholinergic cell groups in mammals have been implicated in cognitive function and memory. Because the forebrains of nonmammals are considerably less complicated than those of mammals, they provide ideal preparations for studying the cholinergic system. The proposed experiments will study the connections of each of the major cholinergic cell groups: the medial septum, the ventral paleostriatum (anatomically similar to the nucleus basalis of Meynert in mammals), and the horizontal limb of the diagonal band of Broca. The research proposed here has two aims. The first is to investigate more thoroughly the anatomy of the basal forebrain systems by (a) studying the efferents of the cholinergic cell groups and (b) studying the afferents to these groups. Anterograde and retrograde tracing techniques will be employed. The second is to develop a new neuroanatomical tracing technique for use with turtles. This technique, which uses Phaseolus vulgaris leucoagglutinin (PHA-L), a kidney bean lectin, has proven useful as an anterograde tracing technique with mammals but has not yet been employed with nonmammals. Study of the simpler forebrain cholinergic system of reptiles should permit a better understanding of this system in mammals. It will also provide the foundation for behavioral studies on the function of the system in cognition and memory in reptiles.
