The Journal of Neuroscience, November 5, 2008, 28(45):11557-11570; doi:10.1523/JNEUROSCI.0545-08.2008
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Behavioral/Systems/Cognitive
Virtual Adult Ears Reveal the Roles of Acoustical Factors and Experience in Auditory Space Map Development
Robert A. A. Campbell,
Andrew J. King,
Fernando R. Nodal,
Jan W. H. Schnupp,
Simon Carlile, and
Timothy P. Doubell
Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford OX1 3PT, United Kingdom
Correspondence should be addressed to Dr. Andrew J. King, Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Parks Road, Oxford OX1 3PT, UK. Email: andrew.king{at}dpag.ox.ac.uk
Auditory neurons in the superior colliculus (SC) respond preferentially to sounds from restricted directions to form a map of auditory space. The development of this representation is shaped by sensory experience, but little is known about the relative contribution of peripheral and central factors to the emergence of adult responses. By recording from the SC of anesthetized ferrets at different age points, we show that the map matures gradually after birth; the spatial receptive fields (SRFs) become more sharply tuned and topographic order emerges by the end of the second postnatal month. Principal components analysis of the head-related transfer function revealed that the time course of map development is mirrored by the maturation of the spatial cues generated by the growing head and external ears. However, using virtual acoustic space stimuli, we show that these acoustical changes are not by themselves responsible for the emergence of SC map topography. Presenting stimuli to infant ferrets through virtual adult ears did not improve the order in the representation of sound azimuth in the SC. But by using linear discriminant analysis to compare different response properties across age, we found that the SRFs of infant neurons nevertheless became more adult-like when stimuli were delivered through virtual adult ears. Hence, although the emergence of auditory topography is likely to depend on refinements in neural circuitry, maturation of the structure of the SRFs (particularly their spatial extent) can be largely accounted for by changes in the acoustics associated with growth of the head and ears.
Key words: virtual acoustic space; receptive field; ferret; linear discriminant analysis; head-related transfer function; sound localization
Received Feb. 6, 2008;
revised Aug. 29, 2008;
accepted Sept. 25, 2008.
Correspondence should be addressed to Dr. Andrew J. King, Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Parks Road, Oxford OX1 3PT, UK. Email: andrew.king{at}dpag.ox.ac.uk
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364(1515):
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[Abstract]
[Full Text]
[PDF]
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