AbstractThe development of size and tonotopy in the inferior colliculus of the kitten was studied using the 14C2‐deoxyglucose technique and tone stimulation with 2 and 15 kHz at a maximum 110 dB sound pressure level. At 2 days of age, frequency‐specific labelling cannot be detected. Two kilohertz labelling is distinctly visible in the rostral and central inferior colliculus at day 6; 15 kHz labelling occurs first at day 11. In the rostral and central inferior colliculus, 2 kHz labelling starts at a ventral and central position and shifts dorsalwards and to a more lateral location between postnatal days 6 and 21. Such a shift is not seen in the caudal inferior colliculus. There, the focus of 2 kHz labelling remains rather constant; only the extension of the labelling increases in the older animals. In all parts of the inferior colliculus, 15 kHz labelling starts at a ventromedial position and shifts to a more lateral location while extending also more dorsalwards as the age increases. These changes in 15 kHz labelling continue up to 3 months. In addition to the ventromedial‐to‐dorsolateral shift and expansion of labelling, there is also a rostral‐to‐caudal gradient of maturation, in that in older animals frequency‐specific labelling reaches farther caudalwards. The reported changes in frequency representation in the inferior colliculus can be explained on the basis of a shift in frequency input and input sensitivity to the laminae of the inferior colliculus, mainly due to maturational changes within the cochlea and/or as a consequence of the increasing size of the inferi
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