ANATOMICAL SUBSTRATE OF AMPHIBIAN BASAL GANGLIA INVOLVEMENT IN VISUOMOTOR BEHAVIOR

The optic tectum of amphibians is known to play a major role in the co ntrol of visually elicited orienting movements, such as prey-catching and avoidance behaviours, The recent finding of a direct striato-tecta l connection in the frog Rana perezi prompted us to study in detail th e anatomical substrate by which the basal ganglia of amphibians may mo dulate visuomotor behaviour, injections of anterograde tracers into th e striatum were combined with applications of retrograde tracers in th e mid-brain tectum. Apart from a direct striato-tectal connection, at least three indirect pathways were observed, viz, a striata-anterior e ntopeduncular-tectal pathway, a striato-pretectal-tectal pathway and a striato-tegmento-tectal pathway. The basal ganglia-tectal connections of anurans largely resemble those described for amniotes, but appear to be more extensive. However, a pallio-tectal connection comparable t o the cortico-tectal pathways of mammals Mras not observed in Rana per ezi. Therefore, the striatum of anurans, which receives multimodal sen sory information, seems to be the sole telencephalic structure that in fluences the mesencephalic tectum via a direct pathway.