Julian Millar J.Millar at qmw.ac.uk
Tue May 2 03:30:58 EST 1995

It is not generally not worth making your own tungsten extracellular
electrodes unless you want something very special. Excellent commercial
electrodes are available from several manufacturers for example from 
A-M Systems (in USA 1-800-426-1306).  The extracellular action potentials
(spikes) recorded with  tungsten electrodes are very much smaller than
intracellular spikes, they are generally  of the order of 10-100
microvolts. Thus in order to get these spikes to a "normal" level of
about 0.1-1 volt for oscilloscope observation or computer logging,
amplification of between 1000 and 100000 is required. You will also need
some bandpass filters. The usual recording band is about 100 Hz to 10,000
Hz. A good book that describes the how to do this kind of recording and
the properties of different types of extracellular electrodes is
"Monitoring Neuronal Activity- A Practical Approach" ed. J.A. Stamford
(IRL Press, Oxford, 1992)

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