Mechanisms of experience-dependent plasticity in the auditory localization pathway of the barn owl |
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Authors: | E I Knudsen |
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Institution: | (1) Department of Neurobiology, Fairchild Building D257, 299 Campus Drive, Stanford, CA 94305-5125, USA e-mail: eknudsen@leland.stanford.edu Tel.: +1-650-723-5492; Fax: +1-650-725-3958, US |
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Abstract: | Sound localization is a computational process that requires the central nervous system to measure various auditory cues and
then associate particular cue values with appropriate locations in space. Behavioral experiments show that barn owls learn
to associate values of cues with locations in space based on experience. The capacity for experience-driven changes in sound
localization behavior is particularly great during a sensitive period that lasts until the approach of adulthood. Neurophysiological
techniques have been used to determine underlying sites of plasticity in the auditory space-processing pathway. The external
nucleus of the inferior colliculus (ICX), where a map of auditory space is synthesized, is a major site of plasticity. Experience
during the sensitive period can cause large-scale, adaptive changes in the tuning of ICX neurons for sound localization cues.
Large-scale physiological changes are accompanied by anatomical remodeling of afferent axons to the ICX. Changes in the tuning
of ICX neurons for cue values involve two stages: (1) the instructed acquisition of neuronal responses to novel cue values
and (2) the elimination of responses to inappropriate cue values. Newly acquired neuronal responses depend differentially
on NMDA receptor currents for their expression. A model is presented that can account for this adaptive plasticity in terms
of plausible cellular mechanisms.
Accepted: 17 April 1999 |
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Keywords: | Sound localization Auditory system Inferior colliculus Superior colliculus Optic tectum Plasticity |
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