Dear Yuri,

Yes, very interesting question. Nevertheless there are many correlated questions. On one side a first question is , where is the code expressed? In the spike sequence? If so variability can depend on the previous history of the neuron, on experimental condition and on the diverse state of the neuron in the moment it receive the stimulus. What in the sequence express the code? The mean inter spike interval and correlated statistics? Could be since seems that spikes are the main output of the neuron and the way they transmit information information to other neurons. But what about the synapses. A single pyramidal neuron can have between 5000 and 60000 synapses that influences the output activity of the neuron. Each of these synapse belong to a neuron who has its own state with its variability in his spike generation. Are we sure that the spike sequence is the code? Can we exclude that spikes are only reset systems and that information transferred to other neurons are not as for example "Hi now I stop working time to work you?". We expect that code generation is of computational type, related to non linear process of neuron that end with a spike when "electrical activity" reach a threshold. We expect that code is of binary and some time of decimal or exadecimal type. I used this system too and model according to this idea, but I am not sure it is the place where to find the code. I am not at all sure that neuron has a digital type code. I think it is the most suitable for our scientific culture but this does not means necessarily that it is the right one. Another point. Why we should expect a single code for all type of neurones? In different area of brain they process different stimuli. They perform taskes very different each other. Why they should use a single code for all these activities? As a metaphor, it is the same as to expect that People of all the world speak the same language (uses the same code). All uses words (spikes) but languages are different (code) in grammar (spike sequence) and in words (spike duration and amplitude). So yes, it is a very interesting question the one you posted, but discussion on it can be very long, tedious and difficult. 

All the best.

Vito

Dear Vito.

Thanks for the answer. Of course, in the reaction of neuron may be several mechanisms of coding information. For example, frequency encoding in the sensory systems is well known. The existence of this mechanism is a proven and there is no doubt. However, other mechanisms are not so obvious. This raises the question: where are we looking for and that are we looking for?