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- Title
Detection of Interaural Time Differences in the Alligator.
- Authors
Carr, Catherine E.; Soares, Daphne; Smolders, Jean; Simon, Jonathan Z.
- Abstract
The auditory systems of birds and mammals use timing information from each ear to detect interaural time difference (ITD). To determine whether the Jeffress-type algorithms that underlie sensitivity to ITD in birds are an evolutionarily stable strategy, we recorded from the auditory nuclei of crocodilians, who are the sister group to the birds. In alligators, precisely timed spikes in the first-order nucleus magnocellularis (NM) encode the timing of sounds, and NM neurons project to neurons in the nucleus laminaris (NL) that detect interaural time differences. In vivo recordings from NL neurons show that the arrival time of phase-locked spikes differs between the ipsilateral and contralateral inputs. When this disparity is nullified by their best ITD, the neurons respond maximally. Thus NL neurons act as coincidence detectors. A biologically detailed model of NL with alligator parameters discriminated ITDs up to 1 kHz. The range of best ITDs represented in NL was much larger than in birds, however, and extended from 0 to 1000μs contralateral, with a median ITD of 450μs. Thus, crocodilians and birds employ similar algorithms for ITD detection, although crocodilians have larger heads.
- Subjects
AUDITORY pathways; ALLIGATORS; NEURONS; BIRDS as laboratory animals; ACOUSTIC nerve; COCHLEAR nucleus
- Publication
Journal of Neuroscience, 2009, Vol 29, Issue 25, p7978
- ISSN
0270-6474
- Publication type
Article
- DOI
10.1523/JNEUROSCI.6154-08.2009