Outstanding stability of ECoG signals recorded epidurally with the WIMAGINE implants in a context of BCI clinical trials
Résumé
Introduction: In the framework of two clinical trials involving participants with chronic spinal cord injury, we intend to take advantage of the remaining brain motor activity to drive effectors to compensate motor handicap. To this aim, we developed WIMAGINE a fully implantable battery-less device able to record ECoG signals on 64 channels through the duramater.
In BCI & tetraplegia clinical trial (NCT02550522), tetraplegic participants are trained to drive an exoskeleton to walk in the lab or to reach and grasp objects from the daily life whereas in STIMO-BSI clinical trial (NCT04632290), a paraplegic participant is also implanted with a spinal neurostimulator to elicit motor activity of their lower limbs.
Results: When we started the design of the WIMAGINE implant, there was a great challenge on such a Brain Computer approach based on epidural signals. Indeed, the signals might have been too weak or their quality might have lessened dramatically after several months due to fibrotic reaction. However, based on our clinical data, we have demonstrated the great interest of our approach and device. The analysis of the signal stability (based on ECoG signal magnitude (RMS), signal to noise ratio, band power levels of the signal spectrum) was performed on three participants. The signal stability of the 1st participant has highlighted an outstanding signal stability even over a three years implantation period. For the two following participants with a respective follow-up duration of 1.5 year and 6 months, the signal stability follows the same trend.
Thanks to this good stability performance, we can foresee uses of the WIMAGINE ECoG recorder during rehabilitation period or for chronic use in the participant's daily life. Note that these implants embedded in the skull thickness can be considered as passive/inert devices once the head-set providing the power thanks to the inductive link at 13.56 MHz.
Outlook: So far, the WIMAGINE implants coupled proprietary decoding algorithms[1], [2] have demonstrated their interest for long-term recording and/or decoding of the ECoG signals. This system is compliant with the MDR 2017/745 regulation and is easy to implant. So far, we have demonstrated that it can be used in implantable BCI projects to drive external or implantable effectors.
References:
[1] A. Moly et al, An adaptive closed-loop ECoG decoder for long-term and stable bimanual control of an exoskeleton by a tetraplegic, DOI: 10.1088/1741-2552/ac59a0.
[2] A. L. Benabid et al., An exoskeleton controlled by an epidural wireless brain-machine interface in a tetraplegic patient: a proof-of-concept demonstration, DOI: 10.1016/S1474-4422(19)30321-7.