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[Neuroscience] Advice Requested: Whole Nerve CAP Recording.

r norman NotMyRealEmail at _comcast.net
Wed May 31 11:25:11 EST 2006


On Wed, 31 May 2006 07:40:57 +0200, "Dr. Michael Ferber"
<Michael.Ferber at gmx.de> wrote:

>Hi Martin,
>I am used only to invertebrate (Insect) extracellular recording. I found that 
>under normal recording conditions a gain of 1000 was sufficient. Furthermoer 
>I always used custom built amplifiers. and a seperate solution for the data 
>acquisition and storage, because monolitic solutions (as the one of ADI) 
>never met my requirements. 
>

My experience is also invertebrate (crustacean).  Spikes can be on the
order of 10 microvolts so whatever gain you need for decent recording
can be calculated.  Preamps of 1000 gain produce 10 mv signals which
often are sufficient for the next stage of recording/display
equipment.

In general, gain is never the problem.  Rather, noise is what you must
worry about and input characteristics for the preamp.  You probably
need high input impedance and low input current with extremely low
noise characteristics and differential input with excellent common
mode rejection.  You also need good control of the upper and lower
frequency cutoffs of filters to help eliminate a variety of noise and
interference.

You don't say what kind of electrodes you are going to use.   That
makes a BIG difference in the kind of preamp you need.  You also don't
indicate what experience you have in such recording, especially in
terms of noise elimination -- especially line frequency interference
from capacitative pickup (i.e. "out of thin air") and ground loops.
If you have a good technique for making electrical contact with the
nerve and can eliminate noise and interference, you are in.  If not,
the choice of preamp isn't going to help.




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