In a nutshell: A newly developed virtual keyboard reveals the importance of usability and realistic testing when developing brain-computer interface systems.

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Brain–computer interfaces (BCI) allow hands-free control of external devices by converting brain activity into computer commands. Using BCI spellers, for example, people can type out words and phrases without lifting a finger. Such technology is crucial for people who are unable to use normal keyboards, but could also be developed to allow anyone to communicate without manual input.

The best-performing BCI spellers can support a typing rate of around 10 words per minute. However, this rate is based on testing by experienced users who repetitively type a small number of predefined phrases. It is not clear whether people using the technology for the first time could communicate freely – which involves thinking of the right words and their correct spelling – at the same rate.

To find out, Brain Function CoE investigators Angela Renton, Jason Mattingley and David Painter, from the University of Queensland, developed a high-performance BCI speller specifically for novice users. They also tested the speller’s performance based on genuine free communication rather than memorized phrases.

Participants viewed a computer display showing a virtual keyboard with keys that each flickered at a unique frequency. To spell a word, participants fixed their gaze on one letter at a time. Focusing attention on a particular frequency of flickering light causes brain cells to respond in a way that can be measured by electroencephalography (EEG), a non-invasive brain-imaging technique. These EEG measurements can then be translated into the corresponding letter, and the participant can move on to selecting the next letter in their chosen word.

The researchers first tested whether novice users could type rapidly on the new BCI speller in a prompted free word association task. Then they developed an interface to allow two users to communicate with one another.

The results showed that free communication was possible, but it was slowed down by users voluntarily making corrections to their spelling and by taking turns during conversations. Based on these results, the researchers identified seven ways to improve existing BCI systems, not only to reduce the time it takes to select characters, but also to increase the system’s accuracy in identifying selected characters.

This work emphasizes the importance of usability when developing BCI systems and the need to test new systems using real-life scenarios.

To encourage other researchers to use the high-performance, non-invasive BCI communication system in their own applications – such as virtual reality, for example – the team has made the underlying code and data freely available. They hope that scientists will use the open-source code to design new BCI spellers and improve the software further.

Next steps:
By adopting many of the techniques used to develop the BCI speller, the team is currently developing a neurofeedback approach to train people to improve their attention. Neurofeedback is a BCI aimed at training participants to change specific patterns of brain activity.

Renton, A.I., Mattingley, J.B., & Painter, D.R. (2019). Optimising non-invasive brain-computer interface systems for free communication between naïve human participants. Scientific Reports, 9, 18705. doi:10.1038/s41598-019-55166-y

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Image credit: David Painter