AI Article Synopsis
- - The bullfrog's amphibian papilla shows frequency selectivity in auditory fibers, similar to mammals, despite lacking a flexible basilar membrane.
- - Researchers discovered that hair cells in this structure exhibit frequency selectivity in their synaptic output when stimulated at various frequencies, influenced by their position.
- - A gradient of Ca(2+) buffers in hair cells helps maintain the sharpness of frequency tuning, suggesting that synaptic tuning is a key mechanism for enhanced frequency selectivity in the amphibian papilla.
Article Abstract
The activity of auditory afferent fibers depends strongly on the frequency of stimulation. Although the bullfrog's amphibian papilla lacks the flexible basilar membrane that effects tuning in mammals, its afferents display comparable frequency selectivity. Seeking additional mechanisms of tuning in this organ, we monitored the synaptic output of hair cells by measuring changes in their membrane capacitance during sinusoidal electrical stimulation at various frequencies. Using perforated-patch recordings, we found that individual hair cells displayed frequency selectivity in synaptic exocytosis within the frequency range sensed by the amphibian papilla. Moreover, each cell's tuning varied in accordance with its tonotopic position. Using confocal imaging, we observed a tonotopic gradient in the concentration of proteinaceous Ca(2+) buffers. A model for synaptic release suggests that this gradient maintains the sharpness of tuning. We conclude that hair cells of the amphibian papilla use synaptic tuning as an additional mechanism for sharpening their frequency selectivity.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3468150 | PMC |
| http://dx.doi.org/10.1523/JNEUROSCI.1246-12.2012 | DOI Listing |
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