place coding, take two

well, I've spent the past few days musing over my notes on this topic, and while I feel reasonably confident that I could write on it (save citations), there is one little hiccup. One of the broad umbrella questions here is "how do we know tonotopic organization is important?" For this question, I feel a little bit like a mother who's kid just asked why the sky is blue or something like that. Now I know there is a good explanation for the sky being blue, most parents will just say "it just is". Well, tonotopic organization is important because "it just is".

In this whole frequency selectivity argument, there is an important distinction between the two theories of frequency encoding: place and temporal code. The basilar membrane can be equated as a series of bandpass filters, tuned in frequency from high to low due to a graded stiffness. Each point along the basilar membrane is maximally tuned to a particular frequency. This in itself implies that place is important. But where the proof? Well, here it gets a little tricky. There are sort of two approaches I can see taking to answer this question. One approach would be to ask the question, what happens when we lose tonotopic organization? The second is to ask where does the other model (temporal code) fail to explain frequency selectivity? Hmmm... it's quite possible that those mean the same thing... maybe there are subtle differences.

Ok, the first question: what happens if tonotopic organization is lost (or impaired)? How would we impair tonotopicity? Well, for one thing, we could knock out part of the cochlea. The problem with this is that it could also impair the other potential explanation.

And here I am stuck for the moment.