The central auditory pathway of the gerbil Psammomys obesus: a deoxyglucose study

The tonotopic organization of the central auditory pathway of the gerbil Psammomys obesus was mapped with deoxyglucose autoradiography under anesthesia. Animals, injected with tritiated deoxyglucose, were stimulated with 0.8, 2.5 and 17.0 kHz tone bursts monaurally in the free field and compared with non-stimulated controls. Apart from the medial geniculate body, all auditory structures showed sound-specific uptake of tracer. Frequency selective tracer accumulation could not be discriminated in the auditory cortex, the nuclei of the lateral lemniscus or the superior olivary complex. Isofrequency laminae could be determined most precisely in the dorsal cochlear nucleus and the central nucleus of the inferior colliculus. About half the mass of each of these nuclei is devoted to the processing of sound below 2.5 kHz. This disproportionately large representation of low frequencies matches the very high sensitivity of the peripheral auditory system in that range.