PMC

Pseudo-colored visualization showing the T values (P < 0.005, uncorrected) associated with the FUS stimulation is overlaid on a 3D-rendered high-resolution MR image volume from the responsive subjects (N = 11). The maximum T value is shown for each individual (T_max) while T_min = 2.65. A white crosshair shows the location of the sonication target. The hollow cylindrical shape behind the head is the contour of the acoustic coupling hydrogel.

(a) The acoustic intensity profile (30 by 30 mm²) of the sonication focus overlaid on a 3D rendering of the volumetric head MRI data. The shape of the acoustic coupling hydrogel is visible (surrounded by white arrows) while the sonication focus was formed in the targeted visual area (inset, colored acoustic intensity map with maximum I_sppa value within the simulated region-of-interest; in W/cm²). See also . (b) The acoustic intensity profile projected on 3D-rendered brain sections from the same individual (from left to right, coronal section, rotated to show the mid-sagittal region of the brain). The white dotted lines indicate the boundaries of the simulated ROIs.

The grand average (N = 10; 50 trials per stimulation condition) EEG evoked potentials elicited by transcranial FUS to the primary visual cortex (red line) and VEP separately elicited by photic stimulation (black line). The FUS was given for a period of 300 ms (thick solid black bar labeled as ‘FUS’) while the 50 ms-long photic stimulation was given (not shown on the plot). Positive (noted with prefix P) and negative (noted with prefix N) peaks of the evoked potentials are annotated. Gray vertical bars indicate the time-segments that showed significant differences in amplitudes between the VEP and the FUS-mediated evoked potentials (P < 10⁻³). A spike of stimulation triggering signal is labeled as ‘Stim trig.’ The inset shows the EEG signals measured at the same electrode site from the resting-state (i.e., no stimulation, black line) and the sham FUS conditions (red line).

Brain coordinates in the coronal direction (according to MNI coordinates) are shown next to each slice. A voxel-wise threshold of P < 10⁻⁴, with a cluster-level correction (see Methods), was used for visualization. See also . L, left; R, right; IFG, inferior frontal gyrus; MFG, middle frontal gyrus; mSFG, medial superior frontal gyrus; ACC, anterior cingulate cortex; PCC, posterior cingulate cortex; AN, anterior nucleus of thalamus; VL, ventral lateral nucleus of thalamus; MD, mediodorsal nucleus of thalamus; LGN, lateral geniculate nucleus of thalamus; PHG, parahippocampal gyrus; STG, superior temporal gyrus; MTG, middle temporal gyrus; ITG, inferior temporal gyrus; IPL, inferior parietal lobule; Post CB, posterior lobe of cerebellum; V1, primary visual cortex.

(a) The FUS apparatus positioned inside of the MR head coil, with the illustration of the sonication path (dotted yellow lines). A picture of the corresponding implementation is also shown with a mannequin head (without an MR head coil). (b) Upper panel: acoustic intensity profile (longitudinal and transversal, inset) of the FUS focus generated by the transducer. The longitudinal profile was measured with a 20 mm gap from the exit plane of the transducer. A cigar-shaped (3 mm in diameter and 17 mm in length) acoustic focus based on the full-width at half-maximum (FWHM) of the acoustic intensity is depicted by the dashed red line. Scale bar, 5 mm. Lower panel: illustration of the acoustic parameters. ISI, inter-stimulation-interval = 13 s in fMRI sessions. 2.5 s in EEG sessions; TBD, tone-burst-duration; PRF, pulse-repetition-frequency; Incident spatial-peak pulse-average acoustic intensity = 16.6 W/cm² I_sppa. (c) Exemplar anatomical MR images overlaid with the functional MRI (P < 0.005, uncorrected; t-value map in pseudo color) and cranial CT (marked in yellow/orange), which were used to plan the sonication path (green line) and the entry point (green dot on the scalp surface) to reach the target (red dot within a white circle). The right lower panel shows the corresponding information on the sectional MRI. (d) A snapshot of MRI (T1-weighted) taken during the MR-guided sonication session, whereby the profile of the acoustic coupling hydrogel, being compressed to ~1 cm thickness, is visible (white arrows). The geometric location of the sonication path with respect to the focal point (red dot) is illustrated with dotted yellow lines. The contour of the FUS transducer is demarcated in purple profile.