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Space and Frequency Are Represented Separately in Auditory Midbrain of the Owl

Knudsen, Eric I. and Konishi, Masakazu (1978) Space and Frequency Are Represented Separately in Auditory Midbrain of the Owl. Journal of Neurophysiology, 41 (4). pp. 870-884. ISSN 0022-3077.

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1. The influence of sound location and sound frequency on the responses of single units in the midbrain auditory area (MLD) of the owl (Tyto alba) were studied using a movable sound source under free-field conditions. With this technique, two functionally distinct regions in MLD have been identified: a tonotopic region and a space-mapped region. 2. MLD units were classified according to their receptive-field properties: 1) limited-field units responded only to sound from a small, discrete area of space; 2) complex-field units exhibited two to four different excitatory areas separated by areas of reduced response or inhibition: 3) space-preferring units responded best to a certain area of space, but their fields expanded considerably with increasing sound intensities; 4) Space-independent units responded similarly to a sound stimulus regardless of its location in space. 3. Limited-field units were located exclusively along the lateral and anterior borders of MLD. These units were tuned to sound frequencies at the high end of the owl's audible range (5-8.7 kHz). They usually responded only at the onset of a tonal stimulus; but most importantly, the units were systematically arranged in this region according to the azimuths and elevations of their receptive fields, thus creating a physiological map of auditory space. Because of this latter, dominant aspect of its functional organization, this region is named the space-mapped region of MLD. 4. The receptive fields of units in the larger, medial portion of MLD were of the space-independent, space-preferring, or complex-field types. These units tended to respond in a sustained fashion to tone and noise bursts, and these units were arranged in a strict frequency-dependent order. Based on this last property, this region is named the tonotopic region of MLD. 5. Because of the salient differences in the response properties of their constituent units, it is argued that the space-mapped region and the tonotopic region are involved in different aspects of sound analysis.

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Additional Information:© 1978 the American Physiological Society. Received for publication October 31, 1977. We thank Dr. A. J. Hudspeth for critically reviewing the manuscript. This research was supported by a National Institutes of Health postdoctoral fellowship to E. I. Knudsen and by a Spencer Foundation grant.
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Spencer FoundationUNSPECIFIED
Issue or Number:4
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Official Citation:Space and frequency are represented separately in auditory midbrain of the owl E. I. Knudsen, M. Konishi Journal of Neurophysiology Published 1 July 1978 Vol. 41 no. 4, 870-884
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62540
Deposited By: Ruth Sustaita
Deposited On:02 Dec 2015 18:56
Last Modified:03 Oct 2019 09:20

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