Single-pulse focused ultrasound evokes a detectable but non-specific VPL response in two macaques

We asked whether one 0.5 s transcranial focused-ultrasound (FUS) pulse produces a detectable single-trial local field potential (LFP) response in the ventral posterolateral (VPL) thalamus, and whether that response is specific to the FUS target. We analyzed 18 runs from two macaques in OpenNeuro ds008610 v1.0.0, using 32-site VPL recordings sampled at 1 kHz. A leave-one-out template over 32 channels and 0–0.6 s distinguished real epochs from sham epochs above the 95th percentile of a 1000-permutation null in 13 of 18 runs. For sub-02, median AUC was 0.68 across five VPL-target runs and 0.82 across four insula-target runs; the pre-specified one-sided Mann–Whitney test of VPL-target AUC greater than insula-target AUC was not supported (U=2, p=0.98, n=5 and 4), with the observed direction opposite. Hand tactile stimulation had median AUC 0.65 in sub-01 and 0.55 in sub-02. The real-to-sham spectral ratio showed no narrow-band lines during 0–0.5 s, making a simple electrical FUS artifact unlikely. The evoked response appeared similar across all 32 sites, a qualitative observation not tested quantitatively. These results indicate a detectable VPL LFP response that was not target-specific in these data. Off-target or indirect effects, network propagation, and common-mode reference signals remain possible explanations and cannot be distinguished here. Limits include two animals, insula-target FUS in one animal, runs from different sessions, one FUS parameter set, sham epochs from the same runs that may include slow after-effects, and run-level analysis; trials are not independent across runs.

focused ultrasound · local field potential · ventral posterolateral thalamus · single-trial detection · macaque · electrophysiology · target specificity