Frequency representation in the dorsal medullary nucleus of the leopard frog,Rana p. pipiens

SummaryThe anuran auditory periphery has two papillae sensitive to different frequency ranges. The projections of fibers from these individual organs were traced to their termination sites in the dorsal medullary nucleus (DMN) by injecting HRP into their nerve roots. Fibers from the amphibian papilla (AP), sensitive to low and intermediate frequencies, were found to terminate throughout most of the DMN. Fibers from the high frequency-sensitive basilar papilla (BP) had terminal fields restricted to the extreme dorsomedial region of the nucleus. Multiunit recordings from the DMN revealed that high frequency neurons are restricted to the dorsomedial DMN, while low and intermediate frequency neurons are present across the width of the nucleus, thus corroborating anatomical results. Physiological results further suggest an orderly representation of frequency along the dorsoventral axis of the DMN, with low frequencies represented ventrally, high frequencies dorsally.

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