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Interested in learning about a novel way to target electrode implants for closed-loop BMIs? Check out our pre-print: https://www.medrxiv.org/content/10.1101/2020.07.10.20149021v1 'Novel intraoperative online functional mapping of somatosensory finger representations for targeted stimulating electrode placement' (1/n)
We utilized hd ECoG arrays + peripheral hand stimulation (A/B) to map finger/tip sensory area intraoperatively, leading to accurate placement of our sensory MEAs for ICMS (C/D) (2/n)
Here’s a subway map showing our process. First time I’ve gotten to ‘K’ in a figure. I’ll break it down: (3/n)
2 months before the surgery, we obtained an MRI and fMRI with peripheral finger stimulation (A). This helped us acquaint ourselves with the patient’s anatomy and develop tentative finger targets (4/n)
We then marked the high-resolution preop scan (B) and imported it into the neuronavigation system (C) to guide the craniotomy (E) over central sulcus (5/n)
We used traditional IONM SSEP phase reversals to confirm central sulcus (F). But we wanted to go further to functionally define finger regions (6/n)
S1 has great finger somatotopy, which we hoped to target for individual finger/tip region stimulation. Therefore, we brought our online functional mapping (OFM) system into the OR (7/n)
We placed hd ECoG strips over M1 and S1 (G) and mapped high gamma responses (H) to peripheral vibrotactile stimulation (D) (8/n)
We used some advanced algorithms (ok, it was @BrockWester) to map the OFM results (H) onto a picture of the craniotomy (I) which displayed our hoped for somatotopy. This guided our final targets (J) and implants (K) (9/n)
So, was all this awake intraop mapping worth it? We think so! (see Fig. 1 coverage maps above) In this figure, you can see the shift in brain target from preop to intraop/final implant locations, which span different receptive fields. Every mm counts! (10/n)
Big question going forward- how generalizable is this approach? Our participant has retained sensation yet many patients with clinically complete lesions may have sensory ‘discomplete’ lesions (h/t Ganzer et al. for the refs) which would still be amenable to this approach. (11/n)
Direct cortical stim is another approach in complete lesions. Non-invasive stim likely isn’t specific enough quite yet to target individual finger/tip regions. Non-invasive imaging can ballpark finger-specific regions, but may also lack finger/tip targeting (12/n)
If you’re interested in learning more about our ICMS results, check out @MattFiferNeuro ‘s preprint: https://www.medrxiv.org/content/10.1101/2020.05.29.20117374v3 (13/n)
And if you’re interested in learning about some of our bimanual motor control results, check out @TessyMThomas ‘s preprint: https://www.medrxiv.org/content/10.1101/2020.06.02.20116913v1 (14/n)
Thanks to all my co-authors! @TessyMThomas @BrockWester (thanks for the figures!) @MattFiferNeuro @FTenoreAPL @losborn1 @slimanjbensmaia amongst many, many others and thanks for reading my first #tweeprint (fin)
