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On-Demand | Fundamentals of Electrical Stimulation

Highly-controlled electrical stimulation can provide a unique tool to discern sensory functions and associated physiological responses. Electrical stimulation, which can take several forms, must be tightly controlled in lab environments for the comfort and safety of participants—human and animal. In this online event, BIOPAC experts will review the fundamentals of electrical stimulation and demonstrate how to safely set up an experiment using electrical or haptic stimulation.

Join David Pollack, BIOPAC Technical Support Manager, and Tim Cook, BIOPAC Product Expert, to learn about the applications and solutions when including electrical stimulation for physiology research.

What You Will Learn:

Application Note 111—Nerve Conduction Velocity



Welcome, everyone, and thank you for joining us today. I’m Brenda from BIOPAC Systems and I will be your moderator on today’s webinar, The Fundamentals of Electrical stimulation.


We are going to get into the world of simulation today. We’re going to talk about voltage, current and safety, and we’re going to show you how to set up your own experiments. Before we dive in, I have some housekeeping I’d like to share with you.


All attendees are muted, so please submit your questions and comments through the GoToWebinar control panel. That is how you communicate with me your moderator.


Today’s webinar is being recorded, we’ll send each of you a link once the recording is processed. Finally, we will have a survey at the web at the end of the webinar.


We’d love to hear your feedback and ideas for future webinars.


Now, on to our presenters, I am excited to introduce Tim and David today. Tim is a product expert here at BIOPAC. He’s also the BIOPAC sales manager and Central Region Representative. He has his M.S. in health and human development with a focus on biometrics. Welcome, Tim.


Thank you, Brenda.


And David is the Technical Support Manager and a test engineer. He has a strong understanding of BIOPAC products and an extensive knowledge of the BIOPAC basic scripting language. He also has a background in physics. Welcome, David.

Glad to be here.

All right, welcome, everybody. This is Tim. Thanks for taking the time out of your day to join us, as the title says, we’re going to cover some essential things related to electrical stim today, and show a couple of specific use cases, highlighting some of our various stimulator options.


Obviously, we’re not able to cover all stimulator options, and all types of applications in one setting. So this initial webinar is kind of meant to set the stage, for future and more focused, and more in-depth webinars. So we’ll definitely keep you apprised of when we have those scheduled. Hopefully, you can join us for those as well.


So, real quickly, I know many attending are likely using BIOPAC already in some capacity, but for those who may be new to BIOPAC, a just a quick introduction, BIOPAC has been in business now for over 30 years.


And we’re proud to be able to say that 98% of top universities run BIOPAC systems throughout their departments.


It’s kind of neat to know these numbers were actually just updated just yesterday, actually by a third party source that we were meeting with.


So it was kind of fortuitous, but BIOPAC has now been cited over 40,000 times in various research journals with approximately 230 new citations occurring each month. And that’s just something we’re really proud of and it’s definitely the result of being both pioneers in the world of the physiological data acquisition starting years and years ago, and working hard to remain in the forefront of technology.


So, today’s webinar is focused on electrical stim, but just real quick, we just want to let you know that we, we work in all types of stim.


We have stimulators available for haptic stim, thermal, olfactory, which is scent delivery systems, visual, and auditory. So all of these can be tied in conjunction with electrical stim or other applications,  such as E-prime or SuperLab.


We have a new presentation license software package, which we will be touching on a really quick later on where these things could be tied in and controlled via those packages and also in virtual reality type data.


So, diving into electrical stim, what exactly is it? In short, it’s just the act of sending controlled, and that’s definitely the key word we want to focus on, controlled electrical pulses through the body of a subject. That subject can be human, animal, or even tissue.


And obviously, today, you know, we’re just touching on human type applications. But do keep in mind that we regularly work with both animal and in tissue type applications.


So, we’re happy to answer questions and provide consultation regarding that as well. In terms of overall use cases, some common ones that we regularly work with are nerve conduction velocity, biofeedback, pain conditioning, fear conditioning, transcranial direct current stimulation, which definitely seems to be by some of the questions we’ve already received is definitely of interest, and H-Reflex.


So, one of the biggest questions that generally comes up with when we’re talking with those interested in adding the Electrical stim to their research is generally concern in overall safety.


So it’s good to know that regulations are in place for nerve and muscle stimulators that we must abide by, and in that likely the main thing to mention is that those regulations limit the max output voltage to 500 volts.


Which is obviously still a lot, but there is a limit. In terms of our specific, amplifiers or stimulators we’re actually limited max voltage output to no more than 400, and in most cases, no more than 200.


So looking at real quickly, a couple of our stimulators, which David will be touching on in just a few minutes.


We have this unit here, which you can see, which is our STM100C. And this actually in and of itself only has a max voltage of 20 volts.


So this can be used for, you know, tissue applications, Invasive mussel applications with needle electrodes, anything that requires, you know, very, very low voltage, to be passed through it.


But other than that, it is also used in conjunction with our other stimulators and it’s kind of like the driving unit behind them.


So the other units pictured here are STMISOC, D and E series.


So basically these connect the inner interface with this stim ISO C and they basically provide additional amplification for this module.


So where this is limited to 20 volts max, when paired and partnered with, the STMISOD, it actually allows for a max output of 100 volts. So this basically has a multiplier in it of the amplifier that allows that to be multiplied by a factor of five.


It is limited to voltage only, though.


The STIMISOE, on the other hand, this basically has an amplifier that amplifies things by a factor of 10 to give you a max output of 200 volts. And again, it’s limited to voltage only.


The STIMISOC on the other hand it’s similar to the E in that it has voltage up to 200 volts, but it also has the ability to run in a current mode.


So this is of the three. This is the most versatile, versatile one of the stim ISO series.


Also, all of these are limited in terms of the overall output pulse width that they can deliver.


So they’re limited to a max of two milliseconds.


One thing I would like to say is that E stim Getting into Electrical stimulation unlike recordings simple by a potentially you know whether we’re recording ECG EMG, things like that.


Those are all passive, there’s really no known ability to harm the subject in any way.


Electrical stimulation is definitely a different world in and does require far more understanding and it’s not something that you just want to delve into without proper training.


Especially putting things in the hands of you know, undergrads or even research assistants who haven’t done it before, training them up on the proper use of these devices is really important.


Looking then, at our STIMISOLA, this is by far our most versatile stimulator, but also with increased versatility, comes increased risk or increased precautions that need to be taken.


This stimulator can actually be run in either voltage or current or constant current mode, um, and it can be controlled through any analog signal.


So that signal could come from one of our data acquisition systems or it could come from E-prime is a common one that’s used to drive it along with MATLAB or Labview.


So, this one’s really quite unfettered and it has a max output voltage of 400 volts.


Any current mode, a max output of 100 millamps.


So there are some limitations on it just for protection.


There is a low output mode, which can be used for things, such as tDCS, where you don’t need the high output, and you need to maintain a very long output waveform.


So this in low voltage mode or low current mode does support arbitrarily long, constant, and non varying direct output curves which are necessary for applications such as tDCS.


Other safety things that we have in place that we always are, at least in the case of the CBLCFMA we always recommend. That’s basically just a throughput cable and a feedback cable that feeds back into our data acquisition system, so that you’re basically recording the amount of stimulus that is being delivered to the subjects, to always know what they’re receiving.


Then the CBLLIMIT2, this is primarily used for tDCS applications to where we need to limit the overall potential of the STMISOLA. Because, again, that has a very wide potential up to 400 volts or 200 mille amps, which would far exceed what we would ever want to pass into a subject for a tDCS application.


So when this cable is used, we basically tune it, it has a potentiometer in it, so we can limit, basically set any limit we want, which is really nice. It’s very customizable. But for tDCS, we limited to a max of three milliamps and that’s just a safety feature.


So even if “a mistake is made”, by yourself or research assistant that something is set, inappropriately in the software, at the wrong level, this is going to ultimately be another safety measure in place to assure that the subject is not going to receive too much current through them.


Looking at some of the larger picture safety concerns, the number one rule in using stimulation is to never put a current across the heart.


So we’re never just stimulating the subjects as a whole, we’re just basically stimulating their body. That’s just not happening.


We’re always stimulating a specific location on the subject and that could be a nerve or a muscle, but the electrodes, when they’re placed, they’re always placed on a specific area of the body close together as close together as possible and on the same side of the body. We’re never putting electrodes anywhere that’s going to be across the pathway of the heart, whether it be, you know, right arm left arm across the chest in any way.


We’re always going to be putting electrodes on a specific spot of the body that way. We’re only stimulating a very focused area and we’re never sending an electrical charge across the heart.


We also always want to just make sure that, when we’re hooking somebody up that the stimulator is off or set to the lowest possible setting, removing all rings and jewelry is a good extra safety measure.

Making sure that everything is properly grounded, and then we’ll talk a little bit more about just electrodes and just the absolute importance of making sure that they are firmly attached to the subject to avoid any aberrant shocks or unwanted shocks.


OK, so Brenda is going to dive into a first audience poll to see what everybody’s up to, and then David will hold our first demonstration.


All right, thanks Tim. And I see some questions coming in.


So while we’re launching the poll and getting your responses, Tim I answered this question and then I was like oh gosh, I’m not a scientist. Maybe I should have you answer this question for everybody. So Leonard asked about what is Haptic Stim?

Haptic e is basically just that specific stimulator is providing like a pulse to the hand. So basically, you know like tapping somebody.


So, more of the sensory, shaking or tap or buzzing, or you know, that kind of yeah.


I mean yeah, like this one is like a little plunger that actually comes out of that device and you can tape it on or tip that you place on the body just to provide that type of a stimulus. Haptic can also be used in  vibration platforms, like a lot of times in virtual reality applications. You’ll sit on a vibration platform which basically just has the nice big subwoofer under it to create like a vibration or like a shaking feeling.


And we offer of stuff that does that as well.


Yeah, we do, we actually offer all of that, so with the virtual reality setup, OK, Christian, let me know if Tim answered your question about the cables because you just have that slide up about STMISOLA.


So, if there are questions that you have about that, let me know. And thank you, everyone, for participating in the poll.


It looks like 31% of people are using electrical stim already. 33% are not.


And 34% of people say it’s like a third of people are, third aren’t, and the third are not sure yet.


Maybe you all, maybe they’ll think about it more after this webinar, so, thank you everyone for participating. I closed the poll and now, David, you are up.


Yeah, so, we’re about to watch a prerecorded, video of a demo of pain threshold, it had to be prerecorded for COVID reasons.


This is a very standard protocol that you probably want to do with basically every new subject you bring in. And with that, Brenda, whenever you’re ready, go ahead and play it.


OK, here we go.


Let’s start with the demo. With me is Conner Fultz, the newest member of the tech support team. He’ll be our test subject today, and I’ll be administering the shocks.


We’ll be doing a very common procedure with him that many researchers will do for every test subject to minimize subject discomfort.


As I said, we’re using the STMISOLA in constant current mode.


As the name suggests, this means current is being held constant, and the voltage is allowed to drift. You’ll see that the red protect light is on, that’s a standard feature that will activate on startup.


This helps to ensure that we’re not accidentally shocking the subject during setup.


You’ll see on the front of the stimulator there’s a useful table that shows the output ranges of the STMISOLA.


We have a row for constant voltage and a row for constant current.


So, now, for our setup we have our EL509s hooked up to Conner here with LEAD110s connected to the stimulator.


These are very basic LEAD110s, which are simply touchproof ends that go to a basic clip and here’s a closeup on the electrodes that we will be using today.


These are EL509s which are standard for simulation.


We’re applying additional gel, this case the GEL104 to the electrodes.


We’re using this GEL104 as it is a low salt content gel, which is what you want for stimulation.


The reason for this is because we’re already pushing ions through the subject and we don’t need to add anymore.


Now, we’re gonna show you how to apply electrodes.


First, take an abrasive pad.


Gently abrade the area you intend to stimulate.


It shouldn’t hurt the subject, just lightly irritate skin.


The area should just be a little red when you’re finished.


You should also remember to take any jewelry, rings, et cetera from the subject.


We don’t want to let any other path to ground exist other than the one we intended.


Then take one electrode.


And apply a drop of gel to it.


Not too much. Just a drop.


Then apply to the skin.


Ideally, you’ll have the electrode on the skin, 5 to 6 minutes before starting to record or stimulate. We’ve had Conner put these electrodes on a few minutes before we started this.


Now, in order to properly do this pain threshold protocol, we need to know how much current we’re actually putting out the stimulator.


To do this we use our CBLCFMA. This part is crucial to successful stimulation.


I tell the customers I talk to, if they don’t already have one to get one, if they’re doing anything with stimulation. Essentially there’s a Y cable that goes between the output of the STMISOLA, and the electrode located on Conner’s arm here.

The other end goes into the INISOA which in turn goes into the AMI100D. And we’ll be running this in AcqKnowledge, just as any other analog channel would be. This gives us precise timing and amplitude of the stimulation that we’ve applied.


Now the last essential piece of the puzzle is the STM100C. This is what we connect to the STMISOLA in order to apply stimulation.


This unit controls the stimulation, but it does not create it.


In our case, that comes from the MP160


What’s useful about the STM100C is the level control knob. This attenuates the stimulation, so that at 0%, nothing is sent, while at 100%, we send the full stimulation that we’ve created, from in this case AcqKnowledge.


We keep it at 0% during setup as a safety precaution.


This method allows us to fully raise the stimulus until our subject can feel it at the right amount.


It’s important to remember what is right for one subject might be too much for another.


This lets us find the optimal level quickly and efficiently.


Now let’s go into AcqKnowledge to look at the software setup.


And hopefully you can see this, we’re going to create and record an experiment.


What I’m going to do first is add our CBLCFMA, and that’s very easy.


All we do is go to our AMI channel one. So, this one right here.


Select the preset for CBLCFMA.


Now, for the stimulation, there’s three ways we can do this.


The easiest is to go through our stimulator feature here.


Now, this is already set up to how I want it, but I’ll show you how we would set that up.


If I hadn’t already done that. So normally if you’ve never done this before, this is what you’d be seeing.  This is the shape of the stimulus that will be sent out.


And as you can see here, we have a few options. So we can make it a sine wave.


We can have this triangle sort of ramp wave, and we can also use another graph to be our source.


Today we’re going to use a simple square wave, and you can either modify it in here and you’ll see that I put that segment to zero because you just use that level for segment. I’ll set it to two or set it to six but let’s go ease in for Conner here and have a five volt waveform that starts exactly 819 milliseconds after we hit start.

You can control that here as well.


We can also output it continuously but in our case we just want to output it once, and we can also  output it as soon as we start recording or we can use this switch here to choose when to start/stop.

Also you should always check this button here for STM100C and make sure this is checked. This is critical for it to work.


And with that let’s start recording.


So you can see that its sitting at zero or slightly above it, it is a flatline right now.


And we still have the STM100C at zero.


We will go ahead and try it out just to be safe and just to make sure we aren’t getting anything that we’re not expected to. So I’m gonna hit this button, and Conner, did you feel anything.




Every time, I want to ask him if he felt anything, he said he felt nothing which is to be expected, its at 0% and we did not see any change here.


So I’m setting the level knob slightly above 0% probably a quarter way above zero, so 25% and I’m gonna hit it again.


Conner did you feel anything?


So he said he felt it a little bit, so that gives us about .25 milliamps right now, that’s negative but that doesn’t really matter for our purposes or for most purposes really.


So we’re gonna set it at 50%, because he barely feels it but that’s not gonna be enough for most studies involving pain or pain thresholds, it just simply won’t be sufficient for him to barely feel it. He actually needs to be a little bit surprised by it.


So testing again.


Conner did you feel anything that time?


How bad was that on a scale of 1 to 10.


Probably four.


So he said probably a four, again, as you can see, we see the difference here.


The difference between the first pulse which was very small, and this one which was about halfway up.


So we’re gonna put it to about 75% and see how that feels.


So Connor did you feel anything there?


Scale of 1 to 10, how would you rate that? Probably a six? OK, I’ve stopped the recording and this has been a demonstration of what you’re going to want to do before you stimulate any subject.


You never want to stimulate more than you are expecting, and this is a good way to slowly and surely be certain of what you’re actually doing. All right, back to you.


OK, so before we go on to you, Tim, I just want to go back because I know that my screen changed when David was abrading the skin.


I want to make sure you guys can see everyone can see first, I was, I was able to see everything else. Operate the area you intend to stipulate.


It shouldn’t hurt the subject just lightly irritate the skin.


OK, so then he applies the gel to the electrode and puts the electrode on. I just wanted to cover that in case my screen blanked out.


So Tim back to you.


OK, there’s my screen showing correctly, OK, Perfect.


So, we definitely don’t want to give like a full physics lesson, but as I mentioned previously, EStim is not a passive recording.


And hence having a basic understanding of electrical principles, really as important as it’s just too easy with these devices to provide unwanted shocks to subjects.


And so, You know, the guiding principle behind everything is Ohm’s Law.


And that basically states that voltage equals current times resistance, and whenever we’re speaking about electricity, you can’t speak about one without the other.


Both voltage and current are required to send, you know, any type of electricity or electrical charge, through a subject. So, you’re always dealing with both of them.


And you can only control for one at one point in time.


And the one that you can’t control for is the resistance.


So, whenever you hear resistance or impedance, I know that they’re speaking about the same thing.


And resistance/impedance is basically a property that’s inherent in all subjects, and it’s simply the material’s tendency to resist the flow of charge.


So it’s probably everybody knows, you know, rubber has a very high impedance. So it’s extremely difficult to pass an electrical current through rubber. Whereas water has a very low impedance, you know, hence if you’re in a lightning storm the last place you want to be is in the lake.


99% of the body’s resistance to electrical current flow is actually at our skin. And that’s just how we’re designed, and it’s basically just the safety mechanism that we have to protect us from a lot of, electrical charge, or flow.


As an example, a calloused dry hand may have more than 100,000 ohms resistance, whereas the internal body has a resistance of much, much lower of about 300 ohms.


And that’s because once you get through the skin, everything is wet and moist.


And just that alone, obviously, as we know, water has a low impedance, so, you know, anything with our body fluids and stuff like that, it’s going to lower the impedance. And that’s important to keep in mind, because if a subject would come in with any type of burn on their skin or, you know, a cut or anything like that, you would never want to put electrodes over that area because it could cause further damage, obviously to that area and it’d be much easier to cause damage to those areas.


But on the other hand, proper skin prep is key.


So really the only thing we can do is that is just a properly prep the skin, which is David showed, lately, abrading the skin, even taking some gel and rub it into the skin. Prior to placing the electrodes on can just help decrease the impedance as much as possible.


We want to keep the impedance saying we don’t want that changing throughout the experiment if we can help it.


So doing proper skin prep on the front end is really the best that we can do.


Now I know I have a hard time kind of seen just the difference between kind of seeing and understanding the different screen voltage and current and how they interact with each other just in my head, so make sure the same way.


So, to me, it kinda helps to use what is a very common analogy, just, it’s a water-based analogy, and so, the amount of water equates to the overall charge.


And then the pressure which would be tied to the steepness of the slope relates to the voltage. And so the  voltage can be thought of as the actual force that pushes the current through the body.


Then, on the other hand, the flow can be equated to the amount of water on the slope.


And that relates to the overall current.


And, overall, only a small, only small amounts of current are actually needed to cause physiological effects, but always keep in mind that both current and voltage are required to deliver any amount of electricity.


So, given, what we know, even if it’s a little about voltage and current, the big question that always comes up is: which one do I use: do I want to stimulate using voltage, or do I want to stimulate using current?


Again, we can’t control the impedance.


We can only control either voltage or current, but not both at the same time.


Personally, I’m always hesitant to speak to what method is best for a particular application? I mean, that’s, that really is where it comes up.


To the end user, did you guys doing your homework and reviewing the literature, and what’s currently being done in your field, to get a good handle on the preferred methods for a specific study?


Then with that information, you know, we’re obviously, that’s when we’re best able to help equip you with, with the proper stimulator, and things like that, to get everything in place, that it’s going to be necessary to carry that out.


In spite of that, it will say that just through working with BIOPAC, now, for over 16 years, constant current does seem to be generally preferred. So, let’s just quickly look at the pros and cons of both.


Looking at constant voltage, the biggest advantage there is that it’s generally deemed a little bit safer.


And that’s primarily because if you have an error with an electrode, say an electrode slips off, you generally don’t get the dangerously high current density and the subject generally doesn’t get as big of aberrant or unwanted shock.


And so, obviously, it’s a little bit safer to the subjects, so can reduce the danger to them a little bit.


The biggest disadvantage, however, is that we cannot guarantee that the exact level of stimulation is going to be given to the subject every time, and that’s primarily because we’re limiting in the voltage only and we’re not accounting for the resistance in the skin.


So, because of that, and pretty much that alone, constant current stimulation does seem to be preferred.


The biggest pro is the fact that with constant current, we always know the exact amount of current that’s going to be delivered to the subject.


That’s a huge benefit.


Again, the biggest disadvantage you deal with is that it’s more prone to abberant shocks and most of that is due to, um, the contact of the electrodes. So it is extremely important to make sure that the that the electrodes stay in contact with the subject at all times. I would always use an electrode.


That is a very nice strong adhesive backing something that, you know, is going to take the subject a bit of effort to pull off.


Because what happens is, we’re holding current constant.


So if the impedance changes and so, basically, if an electrode starts to peel off, the voltage required to keep the current constant is going to, is going to increase.


And as it increases, most likely what happens and, again, you gotta keep in mind, most of this happens within a split second subject sees that electrode started to peel off. And they quickly put, press it back down, will that change an impedance?


Again, as it peeled off the impedance changed, the impedance increased so the voltage, is increasing to maintain the constant current.


When they’ve quickly put it back in place, the impedance immediately drops back down, and all that voltage has to dissipate.


Then, it dissipates between the electrodes on the subject, and it can be a shock as basically to the max level of the overall stimulator.


So in some cases, we’re looking at potential aberrant or unwanted shocks in the neighborhood of 200 to 400 volts.


If that happens, you’re obviously, you know, it hurts.


It actually hurts a lot and you’re going to have some very unhappy subjects in worst-case scenario.


And I have seen it happen to where a subject will go to like an IRB board and complain, and it can really put a damper on and even get your research shut down.


OK, Brenda. That’s all I have for now. We can go into our second poll and then David’s next demonstration.


OK, great, thanks Tim. I’m gonna go ahead and launch the poll.


And Ashish you asked about applications. Please share some applications where you need such high voltage levels, 200 volts and such?


So, do you guys have any other examples that you want to share of research that you’ve seen? Some people stimulate horses. Yeah, and animals definitely and in certain exercise science applications to where you’re doing like a maximal voluntary contraction.


And then at the peak of that contraction, a lot of times, they’ll hit them with the high voltage, basically, kind of see what they got left.


Some people just are really, resistant to this stuff. Like, I’ve had people who needed the need to put 80 volts through with them for them to feel anything, even with proper prep and stuff. Now, don’t start with that.


That’s not normal, but I’ve seen it.


Yeah, a lot of that to be based on the subjects, Just their body fat percentage, that plays a lot into it.


Even are hydrated that can play a factor, definitely, or the weather that day, even. Yeah?


OK, great, so the poll results are almost, and we have another, another 10 seconds or so before answering, but I want to remind everybody that we will have a Q and A session at the end. So the questions that are not getting answered during the poll, we don’t really have a ton of time for questions during the poll.


Its just to give you some initial answers, and also we will do more Q&A at the end.


All right. So we had 13% an exercise phys 30% Psycho Phys 30% bio and biomed.


And then 17% imaging and 11% other, which I always, I only have five answers. I always want to know what other is, so if you feel like sharing what your other is, go ahead and put it in the comments and questions pane.


Thank you all for participating in the poll.


David, I know we’re back to you. Yeah, so this next demonstration is going to be a little bit more interesting.


It’s nerve conduction velocity, which is a very common request we get here in support is how to do this.


So we made this demo in order to go through all the steps that you would need to successfully achieve that.


So Brenda, whenever you’re ready, go ahead and play it OK, here we go.


So now we’re gonna be showing you our nerve conduction velocity protocol and how to successfully implement.


You’ll see that we’re now using our STMISOC rather than our STMISOLA.


This is a lot smaller of a device.


Here’s a closeup of the STMISOC.


See that it has three operational modes. Two voltage modes, and one current mode. The current knob you see here only does anything while you are in current mode.


While in current mode, the input to the stimulator only triggers whatever stimulus you have set up.


Since we are in voltage mode for the setup, the current knob does nothing.


Like last time, the unit is plugged into the STM100C


This time, into the bottom bar.


The outputs of the STMISOC once again go into the CBLCFMA.


Now, although our setup for this particular protocol is that’s a bit more complicated, Also, we’ve moved our stimulating electrodes to lower down on the arm.


These electrodes are placed carefully in order to stimulate the ulnar nerve.


The exact location can be tricky to get right.


If you feel at the bottom of the subject’s elbow, you should be able to move in a parallel line upwards or downward on the on the elbow.


It doesn’t matter which way you choose, both will work.


Today we’ve decided to stimulate on this side of the elbow for no particular reason.


Also, you’ll notice we’ve added two electrodes here.


These are EMG electrodes as we’re going to be recording his muscles responses to those signals.


Hopefully we’ll see a clear response that will allow us to measure the time between the stimulus and the reaction. These red and white electrodes go into the EMG100C.


The EMG100C is one of our standard amplifiers, and works inside AcqKnowledge, just like any other analog signal.


See that all five of our slots on the front of the EMG100C are filled even though we just have two recording elecrodes plus ground.


That’s because these are shielded leads, and those have two outputs.


One being for the shield and one being for the input itself.


The shield goes into the shield slot and the lead in this case goes into BN+.


The metal electrode lead goes to the ground electrode, which is located on the back of Conner’s arm.


This is the ground electrode here, which we’ve attached one of our EL503 standard electrodes.


So, much like the last time, we’re going to be slowly stepping up the voltage.


Using the level knob of the STM100C.


Once again, you start at 0% on the level knob.


We’re going to slowly ramp up the voltage until we can actually see Conner’s finger twitch, which if you would demonstrate for us, much like that, but a little bit less strong. Making his finger twitch is the goal of stimulating this specific nerve. This process should not be painful, though it might feel slightly strange.


Now, once again, we’re going to switch back over into the actual setup of the software.


So again, I’m starting from scratch.


Create a Graph.


So, first thing we gotta do is add our modules.


We have a CBLCFMA, just going to use the preset for that.


And then, we’re going to add our EMG100C.


That’s on channel 2.


And all those settings are correct. I’ve doublechecked them on the amplifier, always important.


And in the stimulator we’re going to use the same basic square wave, that’ll do just fine for what we’re doing.


So, Conner, can you grip your hand to see that we are getting a clean EMG signal? That’s good.




Before you do anything else.


So now we’re going to slowly ramp up voltage we’re giving him, again, as we did before.


So, starting at 0%.


Conner, did you feel anything?


OK, putting up to 25%, Conner, did you feel anything?


A little bit?


So you should see, his hand actually twitched when we hit it properly.


So, we should see his finger twitch, more accurately. At the same 25%.

Feel it?


Felt it, but couldn’t quite see it. Clearly, it’s not quite enough.


Going to increase the voltage again.


50% now.


And, did you feel it?


Now, I don’t think I actually saw a twitch, which means it’s not.


There we go.


Sure, yeah, that’s good, OK.


So that’s pretty good, you can see a twitch there, we’re going to increase it a little bit more so we can get a cleaner response.


Go on about 75%.


Let’s try that again.


There we go.


That’s a nice clean response right there.


If we stop the recording right here and zoom in:


We can see the response very nicely here.


So this red line is our feedback, what we’re actually sending into him.


And the blue line is our EMG.


Now you can see here that this dip mirrors the red dip because it is the same, it’s the same stimulation.


However, this might be a little more clear on another one, or if we zoom out.


This spike is our reaction.


If we zoom in on it, here, we can see you can actually measure the time it took for us to get a reaction after the stimulus, and that’s about six milliseconds, that’s very average, that’s to be expected.


So that’s actually a nice clean signal right there, and that’s what we’d be measuring normally.


Yeah, if we were taking this data for real, if we really wanted to measure nerve conduction velocity, that whole segment right there is what we need.


So that’s really all there is to it.


It’s actually a fairly simple setup, it’s not too hard to get clean useful data here, that’s about it.


All right, and back to you actually.


OK, one thing that’s always important to keep in mind with using our stimulators at least, is they’re not standalone stimulators meant to be used just as 100% standalone device. So basically that means that they do require a data acquisition system. Certain stimulators like the STMISOLA, which David has demonstrated today.


And I believe also like our STM200 which we don’t have the opportunity to demo today.


Those can be tied in with the many other third party systems, as I kind of previously mentioned. They can be used with anything that can create an analog output.


So whether it’s, you know, E-Prime, or SuperLab presentation, most of those have the ability to do that, as well as Matlab and LabView.


So those are some very, very common platforms to where those specific stimulators can be used..


You know, those specific stimulators can be used, Some of the other stimulators;  the STM100C with our STMISO, those who really do require our data acquisition systems.


And not every system we manufacture is actually able to be used for stim, our MP 160 is kinda the thoroughbred of our data acquisition systems. It allows for full 16 channels to be collected simultaneously. It can be used with any of our wired amplifiers, which are our C Series amplifiers, our brand-new D Series amplifiers, along with the full range of our wireless BioNomadix amplifiers or transmitters


And it’s also the most adaptable in terms of interfacing additional third party equipment.


The MP36R are, on the other hand, this is a really nice turn-key system that provides four channels of wired physiological data acquisition and this can also be used in conjunction with the majority of our stimulators. So that’s also an option.


The Smart Center and the Logger.


These are two, you know, data acquisition system options that are newer to our lineup, and I think we’re gonna actually going to be doing a more detailed webinar on these in early April. I believe that’s coming.


And so the Smart Center is just a really nice in-lab smaller in lab solution, it’s extremely portable.


You just hook it up via a USB via a laptop.


And so, it’s easily taken to anywhere you want to go, but data is data is streamed in real time, back to our software. So all data is seen in real-time.


And this works only with our wireless BioNomadix system.


So it can be paired with up to three different transducers. And each transducer is two channels. So, ultimately, you can collect six channels of wireless physiological data, with this system streamed in real time.


And this system also, it does have the ability to connect to other presentation packages such as E-Prime and SuperLab.


The Logger, the other hand, this is 100% full mobile remote data acquisition.


The subject actually wears this on their person, along with up to three BioNomadix wireless transmitters. So, again, up to six channels of physiological data can be recorded. This also has a built-in triaxial accelerometer for overall activity information, and you can even record voice notes into it.


You could set tapping functions to insert markers. So, this is one where the subject goes out into the real-world.


You collect the data, they come back, you plug it in, and download the data in, and move forward with analysis.


In terms of overall signal acquisition, pretty much everything you see here, this, and this isn’t even a complete list, to be honest.


But these are all amplifiers that we manufacture. and for the vast majority of these, they’re available in either wired or wireless options.


So all the core biopotentials many additional measures, such as noninvasive cardiac output, laser doppler flow, O2 CO2 and then a wide gamut of transducers: temperature, pulse, goniometery, and so on.


Then we’re also extremely good system integrators, so we work with a lot of third-party manufacturers to pull in additional physiological data options such as fNIR systems, continuous non invasive blood pressure, EEG systems, advanced brain monitoring, and stationary and mobile eye tracking solutions through Eyetech and Argus.


And speaking of eye tracking, the next demo that David is going to do real quickly is a brand new feature within AcqKnowledge, and it was touched on by Alex Dimov in his last webinar, which was held just about 2, 2.5 weeks ago.


And we now have within AcqKnowledge 5.0.6, a new presentation design.


It basically takes the place of, you know, E-Prime, SuperLab, those presentation packages. So, everything is integrated now, within AcqKnowledge.


We can build your own presentation designs and integrates with our eye tracking system through Eyetech, this bar that you can see pictured here. It also integrates with facial expression analysis FaceReader through Noldus.


And one of the cool things we’re going to show today is the AI driven Eastham.


So, basically, you know, as you’re setting up a paradigm, you can create areas of interest for the subject to focus on in the presentation, and as they’re focused on those areas, in this case, we’re going to drive the stimulator based on a specific area of interest that we define.


It can also be used for the other stim systems that I showed earlier, like for example, the scent delivery system. We could set it up to where if they’re looking at a picture and there’s flowers in the background or foreground.


Once they focus on those flowers for a second, For example, we set up an AOI over that, and area of interest and as they look at that, it could actually trigger the scent palette to output the scent of flowers into their world.


So you know, this really far reaching on what you can do with this in terms of virtual reality applications and things like that, so we’re really excited to show this today.


All right, David, you’re up.




So, the last video we have here, the last demo, I’m just going to be going over our stimulus presentation package and we now have in AcqKnowledge or are about to have and how to interface with a stimulator and it’s pretty straightforward as you’ll see. So, Brenda, whenever you’re ready, go ahead and play that.


So, we’re going to show our presentation package and how you can use that to activate the stimulator and cause a shock. Like last time, we’re using STMISOLA in current mode, and we have it feeding back into analog one up here, let me just get that going up here.


And, as you can see, we have current feedback and on our calculation channel all because we’re using our stimulus presentation package, which, of course, includes eye tracking, we have all of these metrics for the placement of the eye on the screen.


I won’t go into that right now, but that’s what these are.


And under simulator, we have a square wave just like this.


So I want to open a project I already have created here.


Just a short sequence of images and we have and eye tracking bar here that is going to track where I’m looking, and act as I tell it to when I enter certain areas of interest.


For instance, I have this shark image and I want to use this shark image to activate the stimulator.


I did this, and I’ll show you how I did it just right now, I’ll go ahead and do it again. Just make an area of interest with the square tool here, call it something interesting like mouth works fine.

When I enter it I want to start the stimulator, and when I exit it, I want to stop the stimulator.


That means when I look in that area I want to start the stimulator, and when I look out of that area it will stop.


So, this could work for a variety of studies, for instance, fear conditioning, or, something along those lines.


So, let’s go ahead and give us a try. Let’s go ahead and run this.


Get a good image of your eyes here so you can track it.


So this is the calibration step.


Trying to follow the red cross as best as I can with my eyes.


So, now the presentation is actually about to start.


So this is a series of images that will track my eyes and my eye movement across the images. For this, every time I look at different focus areas, AcqKnowledge will be triggered and we’ll be able to see that in the graph. For instance everytime I look at the beer in this image, AcqKnowledge is recognizing that, and we’ll be able to have a count of that at the end.


As far as stimulation goes, every time I look at shark’s mouth, I’m actually shocked.


As you can see here, the stimulator  actually did actually fire off a few times and I did feel it, I set it to low.




This is an fMA channel, and you can see that it did fire two pulses.


Basically as simple as that as far as setting it up, there’s not too much to it, just setting your area of interest and tell it to activate the stimulator.


Then, we can quickly take a look at our other channels.


So this is the y axis of where it thinks I was looking and this is the x axis of where it thinks I was looking. There are some dropouts, I did look off the screen for a bit, so that would be why, because I was looking at this graph, but for the most part it was tracking my eye pretty well.


We’ll most likely get into this stimulus presentation package at a later webinar, but I just wanted to show it off and present it as an option if you’re looking to merge stimulus presentation with electrical stimulation. That’s about all I have. So, back to you.


OK, thanks, David.


OK, we have made it through the main presentation. Now, we are going into the Question and Answer section of the webinar. So, first of all, thank you David and Tim for putting all this together.


I know that it takes a lot of work to put these presentations together so I know, I appreciate it and everybody on the call, I’m sure is appreciating it too.


All right, so Christian had a bunch of questions and I’m going to read through them and then we’ll go back to the top of the questions as well.


So, OK, so I’m using cable and you if I need to show your screen again Tim, let me know. I’m using CBLCFMA and according to this monitoring, the system is sending half the current.


I am sending it to the subjects in an H reflex protocol.


How can I improve the impedance of the system system that’s not relative the change in electrode size?


Neither skin preparations


And he also asked about, and which is the better cable to use with the STMISOLA.


If you’re getting the, this is kind of a more advanced tech support question, and I don’t want to take up too much time here.


I’d like to discuss this further. So, you can send this to


Well, I think that’s a good idea because he had some other questions too, about the variability of the STMSOLA and the function of the and so and so on, OK? So what you can see on the settings and the software, that would kinda be good to look into.


OK, so, this is how you can reach out to support. You can just go to, or to the the Support tab right here, and to submit a ticket.


There’s a ticket submission for requests , and then you can also just e-mail support at, and we’ll show the phone number again, in a little bit.


OK, and let’s see here, let me get back to those other questions.


All right. So David asks, Is it possible using a program like DirectRT


And a parallel, t.t.l. port to trigger the STMISOLA in a similar fashion to using a E-Prime.


Long and short, yes.


I mean anything that can generate a t.t.l. analog out can drive that stimulator.


And so Christian but also asked about maybe that was a different person actually, different spelling how to safely record EMG while using E Stim we answered that.


And we do provide a questions and answers document.


You know, in a follow up e-mail to you over the next few weeks when we get them all together.


OK, so let’s see here we had Youssef.


So T D S is devices. What’s it’s like, Oh, but that’s the cost


So, yes, what’s the cost of your research grade EEG devices and fNIRS devices?


So the best way for you to get a price is to just go to our website and then from any pages you can scroll down and reach out to your local sales representative.


You can also, that’s up here with a demo request or info request, but if you want to find out who your local sales representative is.


Mine is Aimee Walker because I’m in California.


But wherever you come from you’d see your local sales representatives, Tim is based in Colorado, so you’d see him there.


So that’s how you can reach out and get questions answered about price.


OK, I’m actually a bunch of people are asking for more quote type things. So see if there’s anything else here?


OK, somebody asked about, How to do it with a MCE100C, that something you can address now, or is that more a follow-up question?


Probably follow up. I mean, that’s a recording amplifier. Not a not a stim amplifier, so.


OK, OK, all right, so then Ana asked, can you please comment on the use of electrical stim on MRI, environment, compatibility, and security issues?


Yeah, From there, it’s, we do have some limitations on what stimulator can be used.


But we do have a turnkey platform that actually uses our STM100C with one of our stim isolators that I talked about earlier, in conjunction with E-Prime.

All right.


Magdalena as asking do you ever work with researchers to do custom wireless acquisition platform?


But we do have our as I as I spoke on a little bit, we have our Logger  system, which is, this is basically a wireless platform.


So we just need to learn a little bit more about the specific application that you’re looking to do, the specific physiological measures you’re interested in and we can dial it in with the correct wireless BioNomadix units to pair with that device, you know, for your research.


It’s true. The account manager really works with you to figure out what the best product is. So it’s best to reach out to them and explain what you’re trying to do and then they can help you figure it out.


All right another question in the video of nerve conduction what is the difference of stim artifact and genuine EMG activation? It seems that the EMG only gets the stim artifact. Yeah. There’s going to be a lot of stim artifact in that.


Yeah, I should have gone back and try to show that a little bit more. Maybe we’ll link to our application note on it when we send this out so that you can see a little bit better. There will be a delay between just an artifact and actual EMG response.


The EMG response will be more of a regular pulse rather than the sharp up and down of the stim artifact.


It can be hard to see sometimes. The positioning of electrodes really, really matters.


OK, Well, great, thank you so much, that’s all we have time for today. Again, wonderful information, thank you, guys. So, I just have a few closing comments that I’d like to share by. BIOPAC provides webinars monthly throughout the year. You know, we take a break in the summer. And then, the holidays.


But, we are often publishing webinars. In fact, we have close to 50 webinars on our website.


And I’m just going to show you how to get to those real quick, because there’s a lot of great information and training in these recordings, and we’re recording this one today, of course. But if you scroll down, you can, you know, AcqKnowledge tips, and tricks, best practices, all kinds of wonderful content here for you to review.


Our next webinar, we’re gonna cover fNIRS and workload assessment on March 18. So, be sure to sign up for that.


You can visit for additional resources, including: application notes, additional training videos, screencasts with, you know, specific features, and analysis tools, and, of course, upcoming on future webinars and events.


We do miss seeing you all in person, so we look forward to being able to travel again towards the end of the summer or end of the year, and we hope to be able to meet you in person again soon. So panel: anything else before we conclude?


I don’t think so.


Sure, nope. You can always reach us for support at that number shown, or at, always happy to talk to you.


All right, well thank you, audience for attending and for your engagements, I’m getting lots of thank you guys from our audience. So thank you to Tim and David for all over your work and for answering the questions.


This concludes today’s webinar. Stay safe, everyone.


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