by Eduardo Bellomo, Ph.D.
Scientific Consultant (Brain Products)
In the first article of the hyperscanning1 series, we discussed our gold-standard recommendations for hyperscanning with BrainAmp, our stationary, lab-based, modular system, which may be used with passive or active gel-based electrode technology. This is a great solution, but have you ever thought about bringing this setup into a different direction? What if we told you that you can do hyperscanning in real world scenarios, with no gel, no residuals, no cap preparation time, and in a fully mobile, wireless setting?
In this second article of our hyperscanning series, we will focus on the CGX Quick Systems, which are innovative active, dry electrode EEG headsets integrated with Brain Products’ technology and software.
The Quick Systems, namely the Quick-20r v2 and the Quick-32r, are a game changer in the EEG world, thanks to a series of features that enable a fast, intuitive, clean, and mobile setup, while still ensuring high data quality.
When it comes to hyperscanning, the signal from multiple participants is measured for subsequent co-analysis, therefore, it is crucial to find a way of synchronizing the different time series of data. One way to do so is to share triggers between the different devices. The good news is that the CGX Quick Systems meet these requirements for your wireless hyperscanning setup.
So, how do we do hyperscanning with the Quick Systems?
The answer is easy: you should combine the Quick Systems with the CGX Wireless StimTrigger.
The CGX Wireless StimTrigger is a multi-purpose triggering device, co-developed by CGX and Cedrus, that can receive input from different sources and forward them via wireless transmission to a virtually unlimited number of in-range CGX devices (~20 meters).
The device is essentially plug-and-play because it automatically pairs with all the compatible devices in the environment and sends the desired triggers, without the need for software timing compensation for latency and jitter. This provides millisecond precision (<2 ms), making experiments simple and reliable, as in a traditional wired setup.
Additional advantages of the Quick Systems for hyperscanning applications are intrinsically connected to the design of this headset solution. In fact, the Quick Systems can be self-donned and easily used in real-life environments, such as offices or classrooms, where participants are not necessarily willing to engage in a lengthy cap preparation and subsequent hair washing. Moreover, thanks to the one-size-fits-all concept (fitting range: 52 – 62cm, adolescents through adults), you do not have to worry about which cap sizes you should bring. Finally, since the Quick Systems are wireless, the range of movement of your participants is not limited by the length of wires or cables between the participant and the recording computer.
In principle, the number of recipient devices with which the Wireless StimTrigger can share triggers is virtually unlimited. However, it should be kept in mind that the more wireless devices and physical barriers in the same environment, the higher the likelihood for wireless data transmission to be affected. In ideal conditions, up to 8 Quick Systems can be simultaneously used. Keep in mind, however, that it is always better to pilot test your setup before committing to a full-blown data collection. Below, you can find some suggestions that you might want to consider in order to optimize your hyperscanning experience and make subsequent analysis as smooth as possible:
Optimization of the recording environment
Use one recording computer per Quick System, i.e., run only one instance of BrainVision Recorder for CGX on a PC and turn off all other programs and background processes during recording.
Space the Bluetooth® dongle of each recording computer at 1-1.5 meters from each other to reduce the likelihood for cross-device wireless interference.
Make sure that all units have a direct line of sight (i.e., no physical barriers) to the CGX Wireless StimTrigger and the receiving Bluetooth® dongle.
Remove all unnecessary devices from the recording environment (e.g., devices sending Bluetooth® or WiFi signals like mobile phones).
Send frequent and regular synchronization triggers (e.g., one trigger every 5 seconds) to all devices, in addition to your experiment triggers.
Pilot test your setup before the actual data collection.
Visualization, peripheral physiology, and trigger codes
For visualization purposes, you can use the LSL streaming option of Recorder for CGX. Thanks to this option, you will be able to combine multiple instances of the BrainVision LSL Viewer to monitor the signal from all participants on the same computer.
Add peripheral physiology to your hyperscanning setup either via the 2 dropdown ExG channels with touch-proof connectors or by combining the headsets with several AIM Physiological Monitor devices. In fact, just as the Quick Systems, each AIM will receive the wireless triggers from the Wireless StimTrigger.
Curious to learn more about the AIM Physiological Monitor? Re-watch our dedicated AIM webinar!
To make your life easier during analysis, you might want to think ahead and set specific trigger codes, for example, for a subset of participants. With the Wireless StimTrigger, you can use up to 16 bits for your triggers. You can also reprogram the bits individually with the Xidon utility from Cedrus.
1 Hyperscanning refers to obtaining simultaneous recordings from more than one participant. It is useful for interactive and social studies and we have observed a growing interest in this topic in terms of support requests and publications in recent months and years. In this series, we will focus mainly on how to record EEG, but we will also provide you with the necessary information on how to complete the setup by adding other physiological signals or signals coming from various sensors (see our sensor tutorial for some examples).