Percentage of relay and intrinsic neurons in two sensory thalamic nuclei projecting to the non-cortical telencephalon in reptiles Caiman crocodilus.

Large injections of horseradish peroxidase were placed in the non-cortical telencephalon in a reptile, Caiman crocodilus. The number of retrogradely labeled and unlabeled neurons in two sensory thalamic nuclei, nucleus rotundus (vision) and nucleus reuniens pars centralis (audition) were counted. The percentage of unlabeled cells in each nucleus was less than 1%. These data suggest that each of these thalamic nuclei contain few, if any, intrinsic or local circuit neurons.