[Eeglablist] Is this what we see in the EEG?

[Евгений Машеров]

> Hi Yevgeny and Jack,
> 
>> True brain activity manifests itself in the higher frequency range and
> 
> over a very broad frequency band (which corresponds to the conclusions of
> information theory regarding bandwidth and information transmission
> intensity).
> 
> Mathematics captured the universe, but did information theory so too? There
> seems to be different types (definitions) of information than that in
> Shannon's sense. People talk about brain's interregional 'connectivity' by
> showing phase coherence etc., but has anyone proven what is communicated
> between the regions? What is the principle of brain's calculation?
> 
> I even think these questions are perhaps wrong in Wittgenstein's sense.
> 
> Another random skepticism: Electric fields in the extracellular space is
> mostly epiphenomenal in the sense that they do not carry any functions (an
> exception is ephaptic coupling, which occurs in much smaller
> spatial scale). Am I correct? I always think that measuring EEG to estimate
> brain's state is like using a stethoscope to diagnose a car engine. A car
> engine makes noise, but its purpose is to drive a car. If this is the case,
> then how can we be so sure that critical information must be, and always,
> contained in the signal? In fact, we already know that scalp
> EEG's sensitivity to various brain functions and states are patchy.
> 
Information is what can change our actions. Shannon's definition, through probability, is simply a way to make measurable what is intuitively estimable. In this case, it's a way to poorly measure something that can't be measured otherwise. Clearly, any analogies with technology are imprecise, but nevertheless, similar problems sometimes generate similar solutions.
It seems to me that electric fields are secondary to ionic concentration (I'd say "epiphenomenon," but I'm afraid to confuse epileptologists). And in this sense, changes in the field at one point can be related to the field at another, albeit indirectly. As for the analogy with listening to the knock of an engine to detect a malfunction, that's a good one, but I can offer another: when the Tsar ordered Dmitri Mendeleev to discover the secret of French smokeless powder, he examined the factory dump.

Eugen Masherov