Bespoke electrophysiological and imaging equipment
Troubleshooting and frequently asked questions
Having problems with your electrophysiological recordings?
You could either contact us directly or try and find a solution in this page. Here are solutions to frequent problems with single fiber (suction electrodes or oil chambers) and compound action potential (CAP) recordings.
1) There is no signal coming from the tissue preparation
- You might have damaged your tissue while preparing. Try searching for apparent signs of tissue damage
under the microscope. In case you find a nerve damage along the main trunk you could try cutting it at a
distal point and resume recording attempts.
- If you are using a single fibre chamber with a separate oil compartment for splitting, it may be that the
solution (SIF for example) level is too low or not existing. In case you are using a single fiber chamber with
a suction electrode or a compound action potential chamber with isolated glass pipettes, it may be that
your recording electrode inside the glass is not touching the fluid (e.g. SIF). Check that the fluid levels are
optimal.
- One of the cables in the rig is either broken or not in contact (i.e., not connected properly). Go over all
cable connections to check for lose ones.
2) The noise level in the rig is too high to be able to find fibers
- Grounding might be a problem. Try to ground each piece of equipment (don’t forget the light source)
individually to see where the problem is and to solve it.
- One of the electrodes (recording/reference) is broken.
3) Signal-to-noise level is not optimal
- Even without noticeable noise, it might be that one piece of equipment is not properly grounded. Try
grounding as in #2 above.
- Chamber is overflowed and fluid might have penetrated one of the electrical devices. Check whether this
could be the case.
- The problem might be with the viability of your tissue which is not maximal. See Problem #1 above
4) There are too many fiber signals to obtain a single fiber recording
Often due to fiber clustering in a remak bundle it is hard to obtain a single fiber recording. If there are too
many conducting fibers, other than splitting you could also try:
- Search the innervated tissue mechanically or electrically to see if you could find a place with a receptive
field you could isolate. Even if there are other receptive fields, finding a remote one means you could
isolate it with a metal ring and work as if you found a single innervating fiber.
- Try to very gently stroke and pull back the nerve bundle you are recording from with your forceps. In case
you are lucky you would manage to ruin some of the fibers in the remak bundle and be left with single
ones.
5) The compound action potential waveform is jagged in its amplitudes and “broken” into multiple
peaks
- This means you have multiple clusters of fibers conducting in various latencies. If the fibers in the nerve
trunk you are recording from normally have one average conductance latency (which is often the case) the
fibers in your nerve are either damaged, underwent use-dependent latency changes and "spreading" of
latency or there is some other disturbance preventing from some fiber classes to conduct. In other words,
such form changes could either come from change in conduction latencies of the individual fiber classes
or their blockade.
6) How do I make sure I am recording from the same fiber I found with my mechanical search (applies
if your single fiber search method is mechanical stimulation)?
- Use a "falling leaf plot" to do a marking technique in which you are stimulating the receptive field ongoing
with one stimulus (e.g. electrical) and occasionally add another one (e.g. mechanically). If the fiber you are
seeing when electrically stimulating is the same as the one you hear when you are simultaneously
stimulating mechanically it should "jump" latencies upon simultaneous stimulation and slowly return to the
original latency during single stimulation.