EU-funded project AsTeRICS was born with the main objective of developing a support platform to facilitate and improve communication resources of people with motor disabilities, with no cognitive impairment, no perceptual limitations (neither visual nor auditory) and with basic skills in using technologies such as PCs, cell phones, electronic agendas, etc. For most potential users simple approaches such as pushing buttons or switches worked fine but for those with severe motor limitations, different solutions had to be found.
To address these users’ limitations Starlab developed a platform where no physical body interaction was needed by implementing a brain-computer interface (BCI) music playing application. BCI systems measure and interpret the brain’s electrical activity along the scalp, which is known as electroencephalography (EEG), translating this information into commands that are sent to the platform to be controlled. Many BCI systems are based on the detection of event-related potentials (ERP), which is the measured brain response result of a specific event or stimulus. In this case the system developed was a Steady State Visual Evoked Potentials (SSVEP)-based BCI.
SSVEP are natural brain responses to visual stimulation at specific frequencies. When the retina is excited by a repetitive visual stimulus ranging from 4 to 100Hz the brain generates electrical activity matching the visual stimulation frequency and/or its harmonics. This phenomena appears mainly in the visual cortex and is recorded in the EEG.
An SSVEP-based BCI enables the user to select among several commands. Each command is associated with a repetitive visual stimulus (RVS) that has distinctive properties of frequency and phase. The stimuli are simultaneously presented to the user who selects the command to be carried out by focusing his/her attention on the corresponding stimulus. SSVEP-based BCI applications have been widely used and investigated in recent years due to their excellent signal-to-noise ratio, relative immunity to artifacts, short training compared to other BCI methods and high information transfer rate.
Starlab’s BCI application uses Enobio to record the user’s EEG and was configured to control a music player managing a pre-selected music playlist. Up to four external LED-based stimulation panels flickering at a configurable frequency can be used, each one associated to a different music player command: play/stop, play the next track, and raise the volume and lower the volume. Starlab’s approach relies on an asynchronous BCI application where the subject decides voluntarily when to interact with the application. Each time the user wants to carry out an action he/she voluntary blinks twice and immediately during a short time period of 3 seconds every panel flickers at a different frequency.
During the flickering stimulation period the user focus his/her attention on the panel associated with the music player event he wants to execute. After this stimulation period the response to every panel frequency is evaluated and a decision is taken on which frequency was responsible for eliciting the visual evoked potential. The action associated to the detected panel is afterwards immediately commanded
In the following video you can see one of the AsTeRICS partners testing the SSVEP-based BCI music player in its two-panel version. The panel on the left plays/stops the music and the one on the right plays the next track. Tests delivered an excellent performance achieving more than 90% of positive detection accuracy for every user that tried the system.
People with impaired motor abilities suffer from significant deterioration of their quality of life due to the numerous physical and psychological barriers. In order to achieve satisfactory levels of independence and social integration, which in the end represents an improvement in their quality of life, new ways of communication and control must be developed.
Brain Computer Interface technologies provide a promising additional option for recovering basic communication functionalities that will give impaired users the possibility of operating external devices, gaining control of their environment, as well as improving their communication capabilities.
BCI state-of-the-art systems demonstrate the potential of using BCI as an additional communication and control channel. An increasing number of BCI applications have been reported, however current BCI prototypes suffer certain limitations. It’s not only disabled people who could beneficiate from this technology, just imagine the possibilities of using BCI for applications such as home control or gaming!
