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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 for, otherwise.

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 straightforward

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, when
the probe tones had a frequency 6 kHz. At a sound level of 100 dB the firing
rate was *again* strongest, when the probe tones had a frequency 6 kHz. Most
interestingly, the data for the 100 dB probe tones show a second peak at 5.2
kHz. So, the neural data mainly reflect the OHC tuning, and secondarily also
reflect the passive BM tuning. At following stages of neural processing
these secondary peaks are then filtered out by lateral inhibition.