TELENCEPHALIC CONNECTIONS IN LIZARDS .1. PROJECTIONS TO CORTEX

The afferent connections to 5 cortical regions in 2 distantly related species of lizards (Gekko gecko and Iguana iguana) were studied by means of retrograde transport of horseradish peroxidase conjugated to wheat germ agglutinin. Each of the 5 cortical regions is characterized by a specific pattern of projections from telencephalic, thalamic, hypothalamic and brainstem regions. Subdivisions within the 5 cortical regions also receive different patterns of projections. The thalamo-cortical projections are as follows. The small-celled mediodorsal cortex receives a projection from nucleus dorsolateralis anterior pars magnocellularis. The large-celled mediodorsal cortex receives projections from nucleus dorsolateralis anterior pars parvicellularis and pars magnocellularis. The dorsal cortex receives a projection from nucleus dorsolateralis anterior pars parvicellularis. The lateral cortex receives a projection from nucleus dorsolateralis anterior pars magnocellularis. The pallial thickening receives projections from nucleus dorsomedialis and nucleus intercalatus. The latter nucleus receives a direct retinal projection. Thus, the pallial thickening is the recipient of a retino-thalamo-cortical projection. Apparently, the organization of cortical regions among reptiles is more similar than previously realized.