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Re: Cochlea Amplifier models : a new list
The data in that figure (nerve response as a function of stimulus level,
Fig. 7B) can be taken to suggest any number of things. Your
interpretation is one possibility, but I could give you several others.
For example, as sound level goes up, the fiber's response area broadens,
especially towards lower frequencies. This would be entirely consistent
with the BM tuning dependence on level, combined with a saturating
response of the fiber. The fact that at 100 dB only (not 90 dB) there
appear to be two best frequencies could be attributed entirely to the
stochastic nature of the fiber response, i.e. at 5.5 kHz the response
just happens to be a bit low (only 10% below maximum). There are no
error bars so it is not clear whether this is a real dip in the response
or not. My interpretation isn't any better or worse than yours if
neither of us can offer a stochastic model of the fiber response that
explains this data. Its all to easy to find features you are looking
Another problem is that this data is from the 6 kHz CF place - I assume
this is not in the basal turn for squirrel monkey so we really do not
know the BM mechanics at that point.
Your conclusion (point 4) based on the paper you quote is therefore
neither perfect nor obvious.
I'm sure the data is real, but it is incomplete, and explaining it not
For an example, take Fig. 7B in this paper:
Here we see that at one single auditory nerve fiber recording site the
firing rate was strongest at the lowest sound levels of 40 and 50 dB,
the probe tones had a frequency 6 kHz. At a sound level of 100 dB the
rate was *again* strongest, when the probe tones had a frequency 6
interestingly, the data for the 100 dB probe tones show a second peak
kHz. So, the neural data mainly reflect the OHC tuning, and
reflect the passive BM tuning. At following stages of neural processing
these secondary peaks are then filtered out by lateral inhibition.