Rats low frequency hearing

["Didier Depireux, PhD" <ddepi001@xxxxxxxxxxxxx>]

I may be the only person on this list who never recorded from a rat, but
that should not prevent me from making a comment about rat hearing and how
thresholds changes from one strain to another...

Various people have reported various "lowest audible frequency" for rats,
from 250Hz to 1kHz. I understand "threshold" depends on what level you use,
but I also notice that Rutkowski et al (Hear Res 181 (2003) p116) don't
mention neural responses below 500Hz. On the other hand, I read the review
of the whisker system by Chris Moore et al (Neuron 42 (2004) 451-463) and on
page 452, they show that whiskers have natural resonance frequencies from
175 to 700Hz.
On the other hand, Moore also published a book chapter
(top publication in http://web.mit.edu/moore/publications.html )
that shows that whiskers respond to sounds (though he doesn't give any
levels that I could find by a cursory reading). Also, whiskers are very very
sensitive to displacements.
The question then becomes: how much do behavioral audiograms depend on
"whisker hearing". Alternatively, would the behavioral audiogram change
dramatically if whiskers were by-passed, say by using an etymotic sound
delivery system. In Rutkowski et al, sounds are delivered to the ear, so
that their measurements correspond only (mostly?) to cochlear hearing. Or
maybe one could find responses to whisker stimulation in auditory cortex, in
the low-frequency part of the tonotopic axes?

And that's the random thought of the day.

                                    Didier

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Didier A Depireux             ddepi001@xxxxxxxxxxxxx
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