In article <HUNTER.91Aug14150200 at work.nlm.nih.gov>, hunter at work.nlm.nih.gov (Larry Hunter) writes:
>> I think it might be simpler to consider an action potential (or lack
> thereof) as a single message. That way, a neuron has 2 output states,
> and the time it takes to transmit a single message is the period
> between action potentials when the cell is firing at its maximum rate.
> Since S is 2, this reduces to
>> I = N/t = Nf
>> where f = maximum firing frequency of a neuron, as action potentials/second.
>> Granted, this ignores signal propagation via voltage changes that are
> not sufficient to generate action potentials. There is some evidence
> that this mode of transmission may be important, but let's skip that
> for the time being.
>> So, in yet another attempt to rephrase my question:
>> 1. How many sensory neurons are there in an adult human being?
>> 2. What is the maximum firing rate of a neuron? If this varies among
> populations of neurons, what is the distribution of maximum firing
> rates?
I'm not a neurophysiologist. So I don't know what an action potential is,
but I assume it is what is commonly called a _spike_.
If that is the case, then you can certainly compute the possible maximal
information _transfer_ rate between successive layers of neurons as described;
however, this does not imply anything about the maximal information
flow a layer of neurons would have to deal with, but can only give an
_absolute_ upper limit for that flow.
This is so since computation by neurons take place through detection of
correlations between incoming spike trains, as far as I know;
If we consider individual, uncorrelated spikes as messages, we ignore:
a) the correlation between spikes coming in simultaneously from
different sources, and b) the integration of spike trains.
the effective maximal information _processing_ rate could thus be much lower.
(Note that the term _information_ is seen here context-free, in the information-
scientists' sense; thus could be misleading here; the term data would be
better, since, IMHO, information, in the biological sense, presupposes an environment where _data_ has __meaning_, and thus can be interpreted as _information_; the same caveat, obviously, applies to the term _information_
transfer rate; _data_ transfer rate might be more suitable)
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