Interview with EMOTIV’s CTO, Dr Geoffrey Mackellar on EPOC X’s new features

What inspired you to develop EPOC X? What improvements were made and why?

2019 was the tenth anniversary of the release of the original EMOTIV EPOC device and we were inspired to commence a redesign and refresh of the product in order to bring it up to a new standard and to take advantage of new technologies and chipsets which are at the cutting edge of consumer electronic devices.

Our last major update to our flagship EMOTIV EPOC product line was released in 2014 when we released EPOC+. At that time, we took the opportunity to upgrade the motion sensor to a 9-axis device and to expand our communication options to include support for the new Bluetooth™ 4.0 SMART protocol. We continued to upgrade the capabilities of EPOC+ by firmware upgrades, including support for hardware marking and USB-based data transfer using Emotiv EXTENDER, expanding the use of EPOC+ into the ERP community.

Last year we undertook a complete review and redesign of the EPOC+ system to address requests from our community and to include the latest technologies in our new flagship product, EMOTIV EPOC X. It took almost a year between our first design meetings and the delivery of the first EPOC X units from our manufacturing facility.

We made major improvements in the following areas:

Electronics and communications

• The new Bluetooth™ 5.0 standard was released, including high-bandwidth Low-Energy wireless protocols designed for iOT. Compatible chipsets are now being deployed in new computers and mobile devices by major manufacturers. We redesigned our wireless hardware to take advantage of the new standard, while maintaining compatibility with our existing protocols. Data rate and wireless range are both significantly improved and we upgraded and re-tuned the antenna system to provide an enhanced emission pattern and higher efficiency, while reducing the already extremely low radio power directed towards the user.
• Motion sensing technology has advanced substantially since the 2014 release of EPOC+. We selected a new MEMS-based 9-axis sensor which includes an on-chip motion processing engine, cancelling inherent drift and noise using the super-high-speed signals available from the sensors. The corrected signals are sampled for transmission at lower rates. EPOC X provides motion data as absolute quaternion outputs and the corrected accelerometer and magnetometer signals. The stability and accuracy of the motion sensor outputs has been significantly enhanced.
• We revisited our award-winning analogue electronics design, upgrading performance and reducing inherent noise substantially. We split the amplifier arrays into two boards located much closer to the sensors on both sides of the head, reducing electrostatic and mains interference levels and improving immunity to movement of the user. We retained and enhanced the common-mode cancellation systems and our patented real-time contact quality monitoring system to maintain the same level of usability.

Mechanical and usability features

• We completely redesigned the mechanical structure of the headset and sensor system and moved to a new, very high quality supplier who can provide a greatly improved part finish and quality and to eliminate many of the issues which affected our customers.
• We maintained the same arm structure and support system, and the exact placement and montage of the sensors, so users can switch seamlessly between headset models without needing to compensate for changed EEG outputs. Our system still provides the same level of mechanical isolation between sensors which made EPOC and EPOC+ the device of choice for so many different research studies.
• The headband structure was redesigned as a single strip and is now made from pure polycarbonate. The new design is lighter, stronger, less prone to breakage and fatigue, and is also more comfortable.
• We received feedback from our community that users could not properly fit EPOC+ while using a head support in a vehicle or wheelchair, or during sleep studies. We addressed this need by adding a rotating hinge which allows the headband to lock in either the traditional location behind the head, or to lock in a vertical position leaving the rear of the head free to rest against supports or cushions. Locations can be switched without needing to remove the headset.
• EPOC and EPOC+ used the same clip-in sensor system, meaning it was easy to exchange and replace sensors at will. However the clips are very small and fragile and many users needed to buy replacement sensor kits regularly. Following the successful launch of our EMOTIV EPOC Flex Saline 32-channel head cap research system, where the sensor structure was completely redesigned to allow users to remove and replace only the felt sensor pads, we designed the new EPOC X sensor system following the same principles. Users can pre-wet sensors in bulk and fit them easily and securely into each sensor socket, and the socket also includes an outward-facing refill port, allowing the user to re-hydrate the sensors in place, without the need to remove the headset. This means that users can make significantly longer recordings without interrupting the process to remove, rehydrate and refit the headset.
• As part of the design process for Flex Saline, we also invested heavily in electroplating technology, allowing us to directly plate Ag/AgCl onto the sensor contacts. This material replaces the polymer-based electrolytic paste which was known to produce green salty deposits inside the sensor bodies. Although not harmful to the users or detrimental to the signals, the salty material was quite unsightly and sometimes built up to such a degree that the mechanical coupling was compromised. The new electroplated material has shown no signs of corrosion in over two years of use in the Flex Saline prototypes and production devices.

How can neuroscientists and researchers do their work better with EPOC X?

All of the above improvements mean that EPOC X is now a much more user-friendly device for use in research, and for all classes of user. The rotating headband increases the number of potential applications to include people who need head support or who need to lie down during use. While our software currently does not support the full Bluetooth™ 5 feature set, the hardware is fully compatible and is ready to support these features when our Cortex software is upgraded. Our improvements to the wireless communication system means cleaner signals with less packet loss even using legacy protocols, in more difficult experimental settings. High quality data can be collected using mobile devices in the most challenging circumstances, and customers using motion sensor data will notice a significant improvement in accuracy and stability.

The new sensor design is much more convenient, allows for easy and inexpensive change of sensors between subjects for hygiene reasons, and permits longer experiments and easier setup by allowing sensors to be re-hydrated without removing the headset.

The EEG signals are cleaner and less prone to interference by movement and electrical mains pickup, meaning more of your data is usable even in difficult situations. The montage and calibration of EPOC X is unchanged from EPOC+ and EPOC, meaning you can continue long-term experiments using upgraded equipment with no effect on data you have already collected with older devices.

EPOC X will interface with EMOTIV Extender, allowing researchers to extend battery life, record data directly to SD card, enter event markers directly into the EEG data stream with extremely high timing accuracy (ideal for ERP studies). Extender also allows electrically safe operation of the headset directly over an isolated USB connection, without wireless emissions.

EPOC+ and Extender have been rigorously tested in independent research studies at Macquarie University Department of Cognitive Science <1> where SSVEP, passive and active auditory oddball N1 ERPs and face-sensitive N170 evoked response potentials have been simultaneously collected using either EPOC+ or EPOC Flex, co-located with a high-end clinical-grade EEG system (Neuroscan™ Synamps), and shown to produce statistically identical responses. The same authors have verified that EPOC X matches or exceeds the performance of EPOC+ in this setting (private communication), and these results will be published later in 2020.

<1> Williams, N., McArthur, G., de Wit, B., Ibrahim, G. and Badcock, N., in press.