Multisensory integration in the tadpole medulla arises from discrete and overlapping regions of endorgan projection.

Abstract

Vestibular and auditory nuclei in the medulla are inherently multimodal in developing bullfrogs (Rana catesbeiana), responding to pressure, particle motion, and lateral line input. While brainstem and midbrain connectivity of these nuclei have been well mapped across metamorphic development, developmental changes in projection patterns from individual endorgans in the otic capsule (sacculus, utricle, lagena, and amphibian and basilar papilla) to the medulla are less well understood. Using small (26 nl) focal injections of neurobiotin in preganglionic branchlets for specific endorgans, we were able to map input from the separate peripheral organs to different medullary nuclei (medial, superior and lateral vestibular nuclei, the dorsal medullary nucleus, and the anterior lateral line nucleus). Some secondary trans‐synaptic label of the reticular gray and cerebellum was also noted. Projection patterns are correlated with different patterns of medullary responses to vibratory and to pressure stimulation. Endo...