Do you trust your triggers? Novel product presentation: StimTrak
by Nicola Soldati, Ph.D.
Scientific Consultant (Brain Products)
It is time to present another novel product in the family of Brain Products solutions: the StimTrak. The StimTrak combines creativity and rigor, making a very versatile tool which is destined to become a must-have for any kind of laboratory.
The creativity
The StimTrak is a powerful small tool which will be loved by everybody who needs a non-standard way to create the triggers necessary for experiments. The only limit to its applications is your creativity. The StimTrak answers all your questions, like “I have a nonstandard signal (e.g. sensor, external device, etc.) and I want to get a trigger out of it!”. The StimTrak has an input for various kinds of signals. Once the signal is in the box, several options are available. It can be forwarded with the same properties or with a gain factor for amplification so that it can be used to make the StimTrak transparent to other hardware and software.
The same signal can also be recorded by any amplifier through the AUX output. Galvanic isolation guarantees safe measurements in all the cases where the stimulus will come directly from hardware or a device that is not recommended to be in contact with the subject. It protects against any current transmission which could run through the amplifier.
Moreover, the StimTrak can be tuned to detect when the input signal is above a selected threshold and then send a trigger. Thus any signal can generate a trigger based on specific properties and needs.
The StimTrak also includes a built in microphone to record voice or sounds, for example the answers of the subjects or commands. You could thus send a trigger by clapping your hands! How about that!
The rigor
You might be thinking: “I do standard ERP analysis with auditory stimuli delivered by the system, so I don’t need StimTrak”. But, this is not necessarily so. The StimTrak promises to be useful even if you do not need creative trigger generation. In all standard experiments where the rigorousness and precision of the trigger timing plays a crucial role, the StimTrak can definitely become the most important companion of high quality set up and experiments. In fact it can be used to evaluate the characteristics of your stimulus delivery system, and maybe discover hidden errors (and correct them!).
For example, how can you be sure that your auditory stimulus trigger has no jitter? Does the stimulation software do all it claims to? Or what about the hardware? And what about the interaction between the two? With StimTrak you can determine if the trigger timing of the stimulus delivered by the hardware is really what you expect it to be. Take an example: You are doing an Auditory Oddball experiment in which a subject is listening auditory stimuli and has been instructed to spot the rare ones. This paradigm will elicit a stimulus-locked P300 peak in the EEG data. Since this is a typical ERP experiment, you are strongly relying on the robustness of your marker timing in order to average over all the samples to obtain the peak of interest.
But if the marker set via software is inaccurate or jittery, the EEG data will be time locked to the wrong auditory signal portion. The figures show a real measurement of how the auditory stimulus can change if an average over all the stimuli (800 auditory stimuli) is based on the marker given by the software (Figure 1, left) or those given by the StimTrak (Figure 1, right) below.
Figure 1 (left): Auditory stimulus without StimTrak. Blue: average of the auditory stimulus intensity, using the triggers provided by stimulation software. Red: standard deviation. Figure 1 (right): Auditory stimulus with StimTrak. Black: average of the auditory stimulus intensity, using the triggers provided by StimTrak. Red: standard deviation.
It is striking how the standard deviation is reduced by the use of the StimTrak as well as how the amplitude of the signal is increased, thanks to the fact that with the StimTrak the signal is not smeared by the jittering of the marker. And more reliable markers mean more statistical significance and thus highest quality results.
With the StimTrak you can extract a lot of information from your set up. Jitters and delays can be discovered and addressed in any kind of set up, letting you correct for them and improve the quality of all your experiments! We are sure that you will be interested in this product, and we would be happy to answer your questions.