Representation of Sound Localization Cues in the Auditory Thalamus of the Barn Owl

Barn owls can localize a sound source using either the map of auditory space contained in the optic tectum or the auditory forebrain. The auditory thalamus, nucleus ovoidalis (N.Ov), is situated between these two auditory areas, and its inactivation precludes the use of the auditory forebrain for so...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1997-09, Vol.94 (19), p.10421-10425
Main Authors: Proctor, Larry, Konishi, Masakazu
Format: Article
Language:English
Subjects:
Acoustic Stimulation
Animals
Audio frequencies
Auditory Pathways - physiology
Barns
Behavioral neuroscience
Biological Sciences
Birds - physiology
Brain
Ears & hearing
Electrodes
Forebrain
Inferior colliculus
Injection sites
Neurons
Owls
Sound localization
Thalamus
Thalamus - physiology
Tyto alba
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Summary:Barn owls can localize a sound source using either the map of auditory space contained in the optic tectum or the auditory forebrain. The auditory thalamus, nucleus ovoidalis (N.Ov), is situated between these two auditory areas, and its inactivation precludes the use of the auditory forebrain for sound localization. We examined the sources of inputs to the N.Ov as well as their patterns of termination within the nucleus. We also examined the response of single neurons within the N.Ov to tonal stimuli and sound localization cues. Afferents to the N.Ov originated with a diffuse population of neurons located bilaterally within the lateral shell, core, and medial shell subdivisions of the central nucleus of the inferior colliculus. Additional afferent input originated from the ipsilateral ventral nucleus of the lateral lemniscus. No afferent input was provided to the N.Ov from the external nucleus of the inferior colliculus or the optic tectum. The N.Ov was tonotopically organized with high frequencies represented dorsally and low frequencies ventrally. Although neurons in the N.Ov responded to localization cues, there was no apparent topographic mapping of these cues within the nucleus, in contrast to the tectal pathway. However, nearly all possible types of binaural response to sound localization cues were represented. These findings suggest that in the thalamotelencephalic auditory pathway, sound localization is subserved by a nontopographic representation of auditory space.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.94.19.10421