[MURG] Eric: BCI design etc

[Yan King Yin]

Hi Eric

Sorry for the delay, I was updating my web site...

>I recall the word "impedance" being used when I was
>told it couldn't be done :)
>my understanding (which is likely incomplete) is that
>a wire sensitive enough for intracellular recording
>can't handle the current needed for stimulation

(Correct me if I'm wrong, I don't have any lab experience
yet) If the electrical stimulation is single-cell, intracellular,
the current injection required to trigger an action potential
is on the order of nA's (nano-Amperes). For extracellular
stimulation the order of mA is required, depending on how
close the electrode is placed, and whether it is perfectly
insulated. So it seems the current will not be a problem....

The impedance of neurons can be estimated from simple
models. I think impedance matching is not too serious
because of the current advanced state of electronics =)
So I think sharing the same electrode for both recording
and stimulation is OK. Maybe you can ask your friend to
state the problem more specifically...

>if this is exactly the problem (which I doubt), my
>proposal is to draw a glass micropipette out to a
>small diameter and run a thin strip of insulated metal
>down the outside.. then ions could be pumped into the
>cell for stimulation and the metal strip could be used
>for intracellular measurements (but not necessarily at
>the same time due to the possibility of induced
>current from the ions)

Anyway, if you're thinking uploading, chemical information
is needed in addition to electrical information. Your idea
may be good for experimental purpose, but in the long run
it is probably insufficient =)

See my new BCI page -- the organization of this page is
really messy right now, so it may be hard to follow.
http://www.geocities.com/Softuploading/DNI.htm

Dale's Principle
===========
>in invertebrate species it's been found that a
>transmitter can be localized to different parts of a
>neuron says a textbook I have here (2003)
>but they say it isn't known if this is true in mammals
>yet, although proteins are specifically localized, so
>it is possible

Thanks for the quality information you shared =)
I just found out Dale's principle also seems to be incorrect
for some mammalian dopamine neurons. Very problematic =(

yan King Yin
-- http://www.geocities.com/Softuploading



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