On the 26th of December Philip O’Keefe sent out a tweet. This wouldn’t have been any surprising, if not for the fact that Mr O’Keefe suffers from severe paralysis due to ALS (Amyotrophic lateral sclerosis) and did not use any voice-recognition messaging tool.
The tweet read “no need for keystrokes or voices. I created this tweet just by thinking it”
How was Mr O’Keefe able to tweet?
He made used of a new Brain Machine Interface (BMI) produced by Synchron, a company with headquarters in Brooklyn, New York.
What are BMI?
BMI are implantable medical devices that can record and sometimes stimulate brain activity. Hence, they can decode intention and help producing an action, being it movement or speech. This makes them of incredible importance for patients with ALS, Spinal Cord Injury (SCI) or locked in syndrome. The first of its kind was implanted in 2004 in a tetraplegic patient, by Cyberkinetics Inc.
With the advance of technology, these days most BMIs are equipped with multiple (recording/stimulating) channels, use low power, and have compact electronics making them more and more useful in medicine. Moreover, it is possible to use a range of recording options (or electrode types) according to the need of the patient and the invasiveness of the electrode.
Roughly, there are 3 traditional types of electrodes, ordered here by invasiveness: ECog grids, Utah arrays and Michigan arrays.
- ECoG grids look like tape that can be stuck to the top of the brain cortex (under the skull) without the need for puncturing the brain. They are widely used in epilepsy research.
- Utah arrays look like a hairbrush (infinitesimally smaller, or course) with needles that puncture the brain tissue and can recording/stimulate from neurons at a certain depth (not just from the top of the cortex).
- Michigan arrays, which are nail like structures that can record/stimulate from an even higher depth.
What type of electrodes has Mr O’Keefe in his BMI?
None of the above!
Synchron is developing an innovative approach that uses the blood vessels to send a stent-scaffold electrode array to a brain region of interest. The stent-electrode never leaves the blood vessel but is still capable of recording and stimulated to the same extend as if it was directly on the brain.
Is this the future of rehabilitative medicine?
https://doi.org/10.1016/j.copbio.2021.10.001 (including the figure)