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Basic Neuron Questions

Didier A. Depireux didier at rai.isr.umd.edu
Wed Apr 9 08:40:26 EST 2003


John H. <johnh at faraway.xxx> wrote:
> At what time scale does the nervous system operate?

Well,  that's still an open question isn't it? There are 2 schools of
thought (grossly oversimplifying), one that says timing is exquisitely
important, and the relative timing of 2 spikes might encode information down
to the 100 microsecond range, and the other that says that only the average
firing rate, averaged over a certain time window and over neighboring
spikes, is what matters. 
If you look at the book "Spikes" by Bialek and others, they take the
position that it's half-way between the time code and the rate code, i.e.
you have about 1 spike per relevant time-scale. Say you listen to speech, 
and extract the spectral envelope which changes (phonemic rate) _about_ every
30 msec. If the primary auditory cortical neurons are the ones in charge of
extracting spectral envelope, you will find as a correlate that primary
auditory neurons fires at about a rate of 30 Hz...

So the answer, as ever, is "it depends". 

For timing issues, look at the paper on
http://homepage.mac.com/cariani/CarianiWebsite/Publications.html
called "As if time really mattered"


						Didier

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Didier A Depireux         ddepi001 at umaryland.edu  didier at isr.umd.edu
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