Development of tonotopic representation in the Mongolian gerbil: a 2-deoxyglucose study

The spatial representation of frequency in the central auditory system of the neonatal gerbil was mapped with the 2-deoxyglucose (2-DG) autoradiographic technique. At 14 days after birth (DAB), pure tone stimulation produced recognizable patterns of 2-DG uptake. However, at this age, tone-induced areas of increased 2-DG uptake occurred at locations which in the adult respond to higher frequencies. The degree of shift in tonotopic representation was approximately two octaves. The normal adult tonotopic organization of auditory nuclei was achieved by 18 DAB, consistent with the rapid development of auditory function in the gerbil. The results suggest that the spatial distribution of frequency in the cochlea of neonatal animals is different from that in adults. Stimulus-evoked 2-DG uptake occurred first in brainstem auditory nuclei, and was observed in midbrain and forebrain auditory structures only at later ages. This is consistent with a sequential development of function in the central auditory pathway.