Application of subject-specific helmets for the study of human visuomotor behavior using transcranial focused ultrasound: a pilot study
Tae Young Park, Ji Hyeok Jeong, Yong An Chung, Sang Hoon Yeo, Hyungmin Kim
Computer Methods and Programs in Biomedicine 2022 · 10.1016/j.cmpb.2022.107127
Abstract
Background and objective As a novel non-invasive human brain stimulation method, transcranial focused ultrasound (tFUS) is receiving growing attention due to its superior spatial specificity and depth penetrability. Since the focal point of tFUS needs to be fixated precisely to the target brain region during stimulation, a critical issue is to identify and maintain the accurate position and orientation of the tFUS transducer relative to the subject's head. This study aims to propose the entire framework of tFUS stimulation integrating the methods previously proposed by the authors for tFUS transducer configuration optimization and a subject-specific 3D-printed helmet, and to validate this complete setup in a human behavioral neuromodulation study. Methods To find the optimal configuration of the tFUS transducer, a numerical method based on subject-specific tFUS beamlines simulation was used. Then, the subject-specific 3D-printed helmet has been applied to effectively secure the transducer at the estimated optimal configuration. To validate this tFUS framework, a common behavioral neuromodulation paradigm was chosen; the effect of the dorsolateral prefrontal cortex (DLPFC) stimulation on anti-saccade (AS) behavior. While human participants (n=2) were performing AS tasks, tFUS stimulations were randomly applied to the left DLPFC right after the fixation target disappeared. Results The neuromodulation result strongly suggests that the cortical stimulation using the proposed tFUS setup is effective in significantly reducing the error rates of anti-saccades (about -10 %p for S1 and -16 %p for S2), whereas no significant effect was observed on their latencies. These observed behavioral effects are consistent with the previous results based on conventional brain stimulation or lesion studies. Conclusions The proposed subject-specific tFUS framework has been effectively used in human neuromodulation study. The result suggests that the tFUS stimulation targeted to the DLPFC can generate a neuromodulatory effect on AS behavior.
Abstract via europepmc.
Exposures
Exposure 1: Left DLPFC tFUS
Target: dorsolateral prefrontal cortex — “left DLPFC”
Device: Ultran · Ultran Group, USA · GPS 200 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 200 | ✓✓✓ |
| Pulse duration (ms) | 1 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 360 | ✓✓✓ |
| Duty cycle (%) | 36pulse duration × PRF gives 36% | ✓✓✓ |
| Sonication duration (s) | 0.5 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | simulationmean or range across subjects | |
| In-situ pressure (kPa) | 445, 452swept | ✓✓✓⚑ |
| In-situ Isppa (W/cm²) | 6.69, 6.91swept | ✓✓✓⚑ |
| In-situ Ispta (W/cm²) | 2.41, 2.49swept | ✓✓✓⚑ |
| Isppa, domain unspecified (W/cm²) | 13.7, 17.1swept | ✓✓✓ |
tFUS to the left DLPFC was randomly applied once in every set of four anti-saccade trials, starting 200 ms before saccade target onset and lasting 500 ms; no consecutive stimulation trials.
Flags from extraction
exposures[0].in_situ.isppa_w_cm2— Text (Section 2.4) gives Isppa 13.7 and 17.1 W/cm2 and in-situ Ispta 4.9 and 6.2 W/cm2, whereas Table II simulation results give Isppa 6.912/6.686 and Ispta 2.488/2.407; Table II values recorded.exposures[0].in_situ.ispta_w_cm2— Text and Table II disagree on Ispta (see Isppa flag).exposures[0].in_situ.pressure_kpa— Table II gives 0.452 and 0.445 MPa for S1 and S2; recorded as the range [445, 452] kPa across the two subjects.auditory_control— Subjects were instructed to report any audible or tactile sensation during the trials; none did. Not one of the listed vocabulary terms.sham_type— Control trials were interleaved trials without stimulation; no sham sonication was described.n_subjects— Abstract states n 2 (symbol lost in conversion); methods say two male subjects.