Electronics
which explains the high development effort in this area. Recent studies have shown that physically impaired people currently benefit the most from the realisation of BCI/BMI, as they have the potential to enable patients with paraplegia and locked-in syndrome to communicate, write and eat again. Regular exercise with BCIs can even lead to the regeneration of motor skills. In addition, BCIs are used for brain research, such as brain mapping and studying neuronal diseases such as epilepsy and brain tumors.
BCI can be classified into non-invasive and invasive. Measurement of brain activity in invasive BCI proceeds via an electrocorticogram (ECoG) which is placed on the dura – one of the layers of connective tissue that make up the meninges of the brain – to measure spikes or local field potentials (LFPs). Implantation of these BCIs provides the highest resolution, making it of particular interest for brain research – but is also the most invasive method. Due to the implantation of microelectrodes directly at the dura and in the cerebral cortex, infections and bleeding can easily occur. As a result, this technique cannot be used permanently and is currently relegated to the laboratory. Also, a repeat surgery is required to remove the BCI, presenting further patient risk. Due to these limitations in use, there is currently no data on long-term stability.
The right signal
The medical technology company CorTec is working with clinical partners to produce an invasive medical device that is stable over the long term. The device would measure LFPs to convert neural signals into actions from external devices. With this, the neural signal can be transferred
BCI helps ALS patient communicate
Researchers at the Wyss Center for Bio and Neuro-engineering, in collaboration with the University of Tübingen in Germany, have enabled a man in his thirties with complete paralysis, who cannot speak, to communicate via an implanted brain-computer interface. The clinical case study has been ongoing for more than two years with the participant, who has advanced amyotrophic lateral sclerosis (ALS) – a progressive neurodegenerative disease in which people lose the ability to move and talk. The participant, who lives at home with his family, learned to generate brain activity by attempting different movements. These brain signals are picked up by the implanted microelectrodes and are decoded by a machine learning model in real time. The model maps the signals to mean either ‘yes’ or ‘no’. To reveal what the participant wants to communicate, a speller program reads the letters of the alphabet aloud. Using auditory neurofeedback, the participant is able to choose ‘yes’ or ‘no’ to confi rm or reject the letter, ultimately forming whole words and sentences. The team is also working on ABILITY, a wireless implantable BCI device designed
to fl exibly connect to either microelectrode arrays or ECoG electrode grids. This will allow detection and processing of signals from either highly specifi c or larger areas of the brain. The approach could enable speech decoding directly from the brain during imagined speech leading to more natural communication.
The results show that communication is possible with people who are completely locked
in because of ALS. The study was published in Nature Communications in March 2022. Source: Wyss Center
“Recent studies have shown that physically impaired people currently benefi t the most from the realisation of BCI/BMI, as they have the potential to enable patients with paraplegia and locked-in syndrome to communicate, write and eat again.”
into an electrical signal to control a computer, prothesis or wheelchair. Here, the ‘data processing’ takes place completely outside the body using wireless electronics, meaning patients can benefit from new developments in data processing, like more powerful hardware.
The implantable system is designed for bidirectional use, which means both the central and
CorTec °AirRay Electrodes: laser-based technology for application in the central and peripheral nervous system.
Medical Device Developments /
www.nsmedicaldevices.com 79
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