I want to measure nerve conduction velocities and compound action potentials in rat sciatic nerves. Which OpenBCI board would be best for this application?
Normally OpenBCI boards read biosignals via 'surface' attached electrodes. Signals such as EEG, EMG, ECG. These signals are in the microvolts to millivolts range.
I have no knowledge of the measures you mention, but they do not sound like voltage amplitudes. Which is all the boards can measure. How do lab systems measure 'velocities' or 'compound action potentials'? My guess that a velocity could be constructed from two times series channels, with your software determining the propagation time by subtracting the time stamps of the two spikes. But if I recall, nerve signals are not simple spikes, but spike trains. So you would have to be able to align the trains to compare time delays.
Note that for the velocity subtraction, you would not be using the OpenBCI / Brainflow 'time-stamp', which is not microsecond accurate. But instead just determine the number of 'samples' difference in the 'spike' location in your two channels, and multiply by sample time interval. Which is 4ms for Cyton (250Hz) and 5ms for Ganglion (200Hz).
I think the larger issue may be, is 4ms sample interval small enough? Cyton and Ganglion can run at higher sample rates, but this requires the Wifi Shield, which is currently not in the Shop, due to some engineering changes in progress.
I agree with the above. You want a sample interval of about 1 microsecond for good axon spike recordings from rat sciatic nerve. I would ask the lab instructor or company that is providing your rats about whom to ask for such gear (maybe rent for the experiment from someone who has it already?).
Even if BGPKN could run the TI ADS1299 (ADC in the Cyton) at the highest sample rate (16kHz), that would only be a 1/16000 = 62.5 microsecond resolution. It's possible there are open source designs for spike measurement using other chipsets. Open Ephys comes to mind.
But actually from this tutorial, it looks like the more common setup is to just use a digital storage oscilloscope. So relatively inexpensive. The IntanTech gear above is thousands of dollars. Not sure that EMG type equipment is really even needed for velocity measurements.
Way back when, I knew someone who did experiments using a type of snake venom on rat sciatic nerve. He used an oscilloscope, but that was way before laptops existed.
There are many "usb oscilloscopes" available on Amazon and other places. Some even have built in signal generators, that could produce a stimuli. These scopes interface with a supplied PC program to record and do other operations. Some examples,
Comments
Hi BGPKN,
Normally OpenBCI boards read biosignals via 'surface' attached electrodes. Signals such as EEG, EMG, ECG. These signals are in the microvolts to millivolts range.
I have no knowledge of the measures you mention, but they do not sound like voltage amplitudes. Which is all the boards can measure. How do lab systems measure 'velocities' or 'compound action potentials'? My guess that a velocity could be constructed from two times series channels, with your software determining the propagation time by subtracting the time stamps of the two spikes. But if I recall, nerve signals are not simple spikes, but spike trains. So you would have to be able to align the trains to compare time delays.
You might also be aware of the spikerbox project.
https://backyardbrains.com/experiments/teachersguide/spikerbox
Regards, William
Note that for the velocity subtraction, you would not be using the OpenBCI / Brainflow 'time-stamp', which is not microsecond accurate. But instead just determine the number of 'samples' difference in the 'spike' location in your two channels, and multiply by sample time interval. Which is 4ms for Cyton (250Hz) and 5ms for Ganglion (200Hz).
To measure velocities, you may need a precise trigger time. You might need different kit, as in the message above, for better accuracy.
Thank you both for the helpful information. @Billh, do you have any kits that you would recommend?
Cyton supports recording an external trigger channel. It has three 'Aux' channels in addition to the 8 ExG channels.
https://docs.openbci.com/Cyton/CytonExternal/
I think the larger issue may be, is 4ms sample interval small enough? Cyton and Ganglion can run at higher sample rates, but this requires the Wifi Shield, which is currently not in the Shop, due to some engineering changes in progress.
I agree with the above. You want a sample interval of about 1 microsecond for good axon spike recordings from rat sciatic nerve. I would ask the lab instructor or company that is providing your rats about whom to ask for such gear (maybe rent for the experiment from someone who has it already?).
Bill, thanks.
Even if BGPKN could run the TI ADS1299 (ADC in the Cyton) at the highest sample rate (16kHz), that would only be a 1/16000 = 62.5 microsecond resolution. It's possible there are open source designs for spike measurement using other chipsets. Open Ephys comes to mind.
https://open-ephys.org/
https://open-ephys.org/acq-board [uses chipsets below]
https://www.intantech.com/
https://www.intantech.com/RHS_system.html [combination stim and record, 30 kHz sample rate]
But actually from this tutorial, it looks like the more common setup is to just use a digital storage oscilloscope. So relatively inexpensive. The IntanTech gear above is thousands of dollars. Not sure that EMG type equipment is really even needed for velocity measurements.
https://openwetware.org/wiki/Lab_9:_Conduction_Velocity_of_Nerves
Regards, William
Way back when, I knew someone who did experiments using a type of snake venom on rat sciatic nerve. He used an oscilloscope, but that was way before laptops existed.
There are many "usb oscilloscopes" available on Amazon and other places. Some even have built in signal generators, that could produce a stimuli. These scopes interface with a supplied PC program to record and do other operations. Some examples,
https://www.amazon.com/s?k=usb+digital+oscilloscope
https://www.amazon.com/EspoTek-Labrador-Easy-Use-All/dp/B07CVB7ZJG/ [open source project]
https://www.amazon.com/Hantek-Digital-Storage-Oscilloscope-Analyzer/dp/B015XVPPJ6/
https://www.amazon.com/OSC482X-Oscilloscope-Generator-Analyzer-Resolution/dp/B07WGFZSW2/
https://github.com/EspoTek/Labrador
https://espotek.com/labrador/