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Bio Amp Owner’s Guide
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EMG . Electromyography; a recording of the electrical activity of a muscle,
using surface electrodes. The recorded activity may be a voluntary
contraction, or evoked by motor nerve stimulation.
EOG . Electro-oculogram; a recording of the potential difference between the
front and back of the eyeball, as projected on to the face. Bilateral
measurements require a Dual Bio Amp, or two Bio Amps.
ERG . Electroretinogram; a recording of the electrical signals produced in the
retina by a light stimulus. Bilateral measurements require a Dual Bio Amp, or
two Bio Amps.
Cortical Evoked Potentials . Averaged recordings of the electrical activity of
the brain when subject to stimulation: visual evoked response, auditory
evoked response, and somatosensory response. These should be done with
signal averaging, using Scope.
SNAP . Sensory nerve action potential; a recording of evoked responses in
stimulated nerves. This is usually done with signal averaging, using Scope.
Bio Amps are unsuitable for:
• work requiring high-impedance electrodes or a high bandwidth. Such
tasks include intracellular micropipette recordings, which are made from a
very fine, electrolyte-filled tube inserted into a nerve or muscle cell, and
require an electrometer amplifier, and
• needle electromyography; the intramuscular recording of the electrical
activity of a muscle, which requires low input capacitance and a driven
guard.
For these a headstage is required. The bandwidth is limited to approximately
5 kHz.
Recording Technique
Several problems can arise when using the Bio Amp to record signals. These
are basic problems of technique, and should be addressed before setting up. It
is important to understand the types of problems that can occur, how they
manifest, and what can be done to remove them or to minimize their effect.
Potential problem areas include aliasing, frequency distortion, saturation,
ground loops, electrode contact, motion artifacts, electromagnetic fields, and
data display.