In one macaque, off-target insula FUS evoked a larger VPL LFP response than on-target VPL FUS

We used public 32-contact LFP from the right VPL thalamus of one macaque (OpenNeuro ds008610 v1.0.0, sub-02). We compared the response to VPL-targeted FUS (120 trials, 4 runs), insula-targeted FUS (85 trials, 3 runs) and tactile stimulation of the hand (60 trials, 2 runs, positive control). Both FUS conditions evoked a significant LFP (sign-flip max-statistic test, FWE p<0.05 on 32/32 and 28/32 contacts). But the off-target insula sonication gave a larger VPL response than the on-target sonication: peak mean ERP 64 vs 31 uV, latency 97 vs 151 ms, leave-one-run-out single-trial detection AUC 0.85 vs 0.66. The direct contrast had permutation p=0.001. The VPL-FUS response was almost the same on all contacts (common-mode; global field power ratio 3.2). Neither FUS condition increased 70-200 Hz power. Tactile stimulation evoked a 17 ms local response with a 70-200 Hz increase. Thus, in this animal, the FUS-evoked VPL LFP does not show the signature of a local response to the sonication target. FUS write-channel studies need off-target sonication controls. Limits: one animal, and the conditions come from different sessions with FUS parameters not given in the files. Code, figures, statistics and data provenance are included.

focused ultrasound · local field potential · thalamus · brain-computer interface · target specificity