The Journal of Neuroscience, December 1, 2001, 21(23):9455-9459
Cochlear and Neural Delays for Coincidence Detection in Owls
José Luis
Peña1,
Svenja
Viete1,
Kazuo
Funabiki1,
Kourosh
Saberi2, and
Masakazu
Konishi1
1 Division of Biology, California Institute of
Technology, Pasadena, California 91125, and 2 Department of
Cognitive Science, University of California at Irvine, Irvine,
California 92697
The auditory system uses delay lines and coincidence detection to
measure the interaural time difference (ITD). Both axons and the
cochlea could provide such delays. The stereausis theory assumes that
differences in wave propagation time along the basilar membrane can
provide the necessary delays, if the coincidence detectors receive
input from fibers innervating different loci on the left and right
basilar membranes. If this hypothesis were true, the left and right
inputs to coincidence detectors should differ in their frequency
tuning. The owl's nucleus laminaris contains coincidence detector
neurons that receive input from the left and right cochlear nuclei.
Monaural frequency-tuning curves of nucleus laminaris neurons showed
small interaural differences. In addition, their preferred ITDs were
not correlated with the interaural frequency mismatches. Instead, the
preferred ITD of the neuron agrees with that predicted from the
distribution of axonal delays. Thus, there is no need to invoke
mechanisms other than neural delays to explain the detection of ITDs by
the barn owl's laminaris neurons.
Key words:
owl; nucleus laminaris; frequency tuning; coincidence
detection; delay lines; sound localization; stereausis
Copyright © 2001 Society for Neuroscience 0270-6474/01/21239455-05$05.00/0
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