🚀 go-pugleaf

The best place to start is to go to a medical library and check out
books on neurobiological techniques.  My experience has been from
being a volunteer subject.  An electrode is designated as an
indifferent from which potentials will be measured.  Following a
chart of standardized stereotaxic coordinates, other electrodes are
placed on the scalp.  Occasionally, a second reference electrode is
placed on the head to pick up electromyographic response from eye
blinks, and other facial muscular response.  This is helpful for
removing muscle artifact from the EEG response.

The electrodes are usually small gold (plated?) cups that are
filled with a conductive paste that looks like toothpaste.  The
electrodes are taped in place.  Removing the tape and getting the
paste out of your hair later on isn't a lot of fun, but this is
science, you know.  I belevie you can get the paste and electrodes
from the Grass Instrument company.

The EEG response is pretty tiny - only a few microvolts.  The
amplifiers on the set-up to which I was connected had a gain of
10^4 and a frequency response of about .5 - 3000 Hz.  I had to
perform a task of trying to distinguish two slightly dissimilar
current stimuli.  The researchers were looking for specific
cortical evoked potentials and also looked for what was hoped would
be cellular responses by high pass filtering the resultant data.

There diagnostic EEG tests taht look for certain well known evoked
potential responses that occur at known latencies following the
onset of a stimulus.  An audio click stimulus can be used to
generate a BSEP resonse.  A trained technician can make neural
diagnostic assesments by observing the BSEP.  I suspect that
diagnostic type EEG equipment may be much simpler than that used
for research applications because a specific response is
investigated.

The other thing you want to watch out for is strict adherence with
safety procedures when you go about wiring up people to devices.
Battery powered amplifiers with optical or RF isolation are a good
idea.  Everything should be fused with fast acting very low mA
fuses too.

Joseph Carr has written several good books for do-it-yourself
computer interfacing and biological projects. 


-- 
Bill Mayhew      NEOUCOM Computer Services Department
Rootstown, OH  44272-9995  USA    phone: 216-325-2511
wtm@uhura.neoucom.edu (140.220.1.1)    146.580: N8WED