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This Article Full Text Full Text (PDF) All Versions of this Article: 93/1/454    most recent 00569.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Pienkowski, M. Articles by Harrison, R. V. Search for Related Content PubMed PubMed Citation Articles by Pienkowski, M. Articles by Harrison, R. V.

Tone Frequency Maps and Receptive Fields in the Developing Chinchilla Auditory Cortex

Auditory Science Laboratory, Department of Otolaryngology and Brain and Behaviour Division, The Hospital for Sick Children, Toronto, Ontario; and Department of Physiology and the Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada

Submitted 1 June 2004; accepted in final form 20 August 2004

Single-unit responses to tone pip stimuli were isolated from numerous microelectrode penetrations of auditory cortex (under ketamine anesthesia) in the developing chinchilla (laniger), a precocious mammal. Results are reported at postnatal day 3 (P3), P15, and P30, and from adult animals. Hearing sensitivity and spike firing rates were mature in the youngest group. The topographic representation of sound frequency (tonotopic map) in primary and secondary auditory cortex was also well ordered and sharply tuned by P3. The spectral-temporal complexity of cortical receptive fields, on the other hand, increased progressively (past P30) to adulthood. The (purported) refinement of initially diffuse tonotopic projections to cortex thus seems to occur in utero in the chinchilla, where external (and maternal) sounds are considerably attenuated and might not contribute to the mechanism(s) involved. This compares well with recent studies of vision, suggesting that the refinement of the retinotopic map does not require external light, but rather waves of (correlated) spontaneous activity on the retina. In contrast, it is most probable that selectivity for more complex sound features, such as frequency stacks and glides, develops under the influence of the postnatal acoustic environment and that inadequate sound stimulation in early development (e.g., due to chronic middle ear disease) impairs the formation of the requisite intracortical (and/or subcortical) circuitry.

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