Journal of Neurophysiology, Vol 71, Issue 1 79-94, Copyright © 1994 by APS

ARTICLES

Adaptive plasticity of the auditory space map in the optic tectum of adult and baby barn owls in response to external ear modification

E. I. Knudsen, S. D. Esterly and J. F. Olsen
Department of Neurobiology, Stanford University School of Medicine, California 94305-5401.

1. This study demonstrates the influence of experience on the establishment and maintenance of the auditory map of space in the optic tectum of the barn owl. Auditory experience was altered either by preventing the structures of the external ears (the facial ruff and preaural flaps) from appearing in baby barn owls (baby ruff-cut owls) or by removing these structures in adults (adult ruff-cut owls). These structures shape the binaural cues used for localizing sounds in both the horizontal and vertical dimensions. 2. The acoustic effects of removing the external ear structures were measured using probe tube microphones placed in the ear canals. In both baby and adult ruff-cut owls, the spatial pattern of binaural localization cues was dramatically different from normal: interaural level difference (ILD) changed with azimuth instead of with elevation, the rate of change of ILD across space was decreased relative to normal, and the rate of change of interaural time difference (ITD) across frontal space was increased relative to normal. 3. The neurophysiological representations of ITD and ILD in the optic tectum were measured before and > or = 3 mo after ruff removal in adults and beginning at 4.5 months of age in baby ruff-cut owls. Multiunit tuning to ITD and to ILD was measured using dichotic stimulation in ketamine-anesthetized owls. The tectal maps of ITD and ILD were reconstructed using visual receptive field location as a marker for recording site location in the optic tectum. 4. Adjustment of the tectal map of ITD to the altered spatial pattern of acoustic ITD was essentially complete in adults as well as in baby ruff-cut owls. This adjustment changed the magnification of ITD across the tectum, with resultant changes in ITD tuning at individual tectal sites of up to approximately 25 microseconds (approximately 5% of the physiological range) relative to normal values. 5. Adaptation of the tectal ILD map to the ruff-cut spatial pattern of acoustic ILD was substantial but clearly incomplete in both adult and baby ruff-cut owls. Although changes of up to approximately 15 dB (approximately 47% of the physiological range) relative to normal tuning were observed at certain tectal sites, the topography of the ILD map was always intermediate between normal and that predicted by the ruff-cut spatial pattern of acoustic ILD.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				E. I. Knudsen, W. Zheng, and W. M. DeBello Traces of learning in the auditory localization pathway PNAS, October 24, 2000; 97(22): 11815 - 11820. [Abstract] [Full Text] [PDF]

				J. I. Gold and E. I. Knudsen Abnormal Auditory Experience Induces Frequency-Specific Adjustments in Unit Tuning for Binaural Localization Cues in the Optic Tectum of Juvenile Owls J. Neurosci., January 15, 2000; 20(2): 862 - 877. [Abstract] [Full Text] [PDF]

				P. Faure and R. Hoy Auditory symmetry analysis J. Exp. Biol., January 11, 2000; 203(21): 3209 - 3223. [Abstract] [PDF]

				J. I. Gold and E. I. Knudsen Hearing Impairment Induces Frequency-Specific Adjustments in Auditory Spatial Tuning in the Optic Tectum of Young Owls J Neurophysiol, November 1, 1999; 82(5): 2197 - 2209. [Abstract] [Full Text] [PDF]

				C. H. Parsons, R. G. Lanyon, J. W. H. Schnupp, and A. J. King Effects of Altering Spectral Cues in Infancy on Horizontal and Vertical Sound Localization by Adult Ferrets J Neurophysiol, November 1, 1999; 82(5): 2294 - 2309. [Abstract] [Full Text] [PDF]

				D. R. Moore, J. E. Hine, Z. D. Jiang, H. Matsuda, C. H. Parsons, and A. J. King Conductive Hearing Loss Produces a Reversible Binaural Hearing Impairment J. Neurosci., October 1, 1999; 19(19): 8704 - 8711. [Abstract] [Full Text] [PDF]

				Y. E. Cohen and E. I. Knudsen Representation of Binaural Spatial Cues in Field L of the Barn Owl Forebrain J Neurophysiol, February 1, 1998; 79(2): 879 - 890. [Abstract] [Full Text] [PDF]

				Y. E. Cohen, G. L. Miller, and E. I. Knudsen Forebrain Pathway for Auditory Space Processing in the Barn Owl J Neurophysiol, February 1, 1998; 79(2): 891 - 902. [Abstract] [Full Text] [PDF]

				J. W. H. Schnupp, A. J. King, and S. Carlile Altered Spectral Localization Cues Disrupt the Development of the Auditory Space Map in the Superior Colliculus of the Ferret J Neurophysiol, February 1, 1998; 79(2): 1053 - 1069. [Abstract] [Full Text] [PDF]