Transcranial focused ultrasound to the thalamus alters anesthesia time in rats
Seung-Schik Yoo, Hyungmin Kim, Byoung-Kyong Min, Eric Franck, Shinsuk Park
NeuroReport 2011, 22, 783-787 · 10.1097/wnr.0b013e32834b2957
Abstract
A pulsed application of focused ultrasound (FUS) to the regional brain tissue alters the state of tissue excitability and thus provides the means for noninvasive functional neuromodulation. We report that the application of transcranial FUS to the thalamus of anesthetized rats reduced the time to emergence of voluntary movement from intraperitoneal ketamine/xylazine anesthesia. Low-intensity FUS was applied to the thalamus of anesthetized animals. The times required for the animals to show distinct physiological/behavioral changes were measured and compared with those times required in a control session without sonication. The sonication significantly reduced the time to show pinch response and voluntary movement. The modulatory effects of FUS on anesthesia suggest potential therapeutic applications for disorders of consciousness such as minimally consciousness states.
Abstract via europepmc.
Exposures
Exposure 1: Pulsed FUS to thalamus (anesthesia emergence experiment)
Target: thalamus — “thalamus”
Device: custom-built · Sonomo, Korea ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 650 | ✓✓✓ |
| Pulse duration (ms) | 0.5 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 100 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 5% | |
| Sonication duration (s) | 1,200 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | deratingsingle value | |
| In-situ pressure (kPa) | 490 | ✓✓✓ |
| In-situ Isppa (W/cm²) | 6 | ✓✓✓⚑ |
| In-situ Ispta (W/cm²) | 0.3 | ✓✓✓ |
For sonication parameters, tone burst duration of 0.5 ms and pulse repetition frequency of 100 Hz were used. Sonication began 40 min after the onset of anesthesia and was maintained for 20 min.
Flags from extraction
n_subjects— 17 rats were enrolled total (2 used only for a pilot timing survey); of the remaining 15, 2 were excluded (atypical hyperventilation n=1, incomplete anesthetic induction n=1). Statistical tests report df=12, consistent with n=13 analysed; n_subjects set to 13 (the analysed cohort) rather than 17 (total enrolled).exposures[0].in_situ.isppa_w_cm2— The text describes 6 W/cm2 Isppa (490 kPa, MI 0.61) as the parameters of an earlier 'preliminary test on three animals'; it is not stated in an entirely unambiguous single sentence that this is exactly the same protocol used for the main n=13 anesthesia-emergence cohort, though the surrounding text and use of the same tone-burst duration/PRF strongly implies it.direction_of_effect— Classified as 'excitatory' because sonication accelerated emergence/arousal from anesthesia, but the paper explicitly discusses that a lower intensity with identical pulse timing previously produced a suppressive effect on cortical excitability in other studies -- direction is parameter (intensity) dependent.blinding— Set to 'none' based on the Discussion statement about 'the use of less subjective and nonblinded assessment of the anesthetic states', implying the physiological/behavioural scoring was not blinded.
Notes: Study design is a within-animal crossover (FUS vs. no-sonication control session, order randomised and counter-balanced). The higher-intensity protocol (Isppa=6 W/cm2) used in the reported main comparison was first identified in an unreported preliminary 3-animal test; a previously published lower-intensity protocol (Isppa=3.3 W/cm2, same 0.5 ms/100 Hz timing) is mentioned for context but was not itself tested in this paper's main dataset.