Suppression of EEG visual-evoked potentials in rats through neuromodulatory focused ultrasound
Hyungmin Kim, Michael Y. Park, Stephanie D. Lee, Wonhye Lee, Alan Chiu, Seung-Schik Yoo
NeuroReport 2015, 26, 211-215 · 10.1097/wnr.0000000000000330
Abstract
We investigated the use of pulsed low-intensity focused ultrasound (FUS) to suppress the visual neural response induced by light stimulation in rodents. FUS was administered transcranially to the rat visual cortex using different acoustic intensities and pulsing duty cycles. The visual-evoked potentials (VEPs) generated by an external strobe light stimulation were measured three times before, once during, and five times after the sonication. The VEP magnitude was suppressed during the sonication using a 5% duty cycle (pulse-repetition frequency of 100 Hz) and a spatial-peak pulse-average acoustic intensity of 3 W/cm; however, this suppressive effect was not present when a lower acoustic intensity and duty cycle were used. The application of a higher intensity and duty cycle resulted in a slight elevation in VEP magnitude, which suggested excitatory neuromodulation. Our findings demonstrate that the application of pulsed FUS to the region-specific brain area not only suppresses its excitability, but can also enhance the excitability depending on the acoustic intensity and the rate of energy deposition. This bimodal feature of FUS-mediated neuromodulation, which has been predicted by numerical models on neural membrane capacitance change by the external acoustic pressure waves, suggests its versatility for neurotherapeutic applications.
Abstract via europepmc.
Exposures
Exposure 1: Pulsed FUS to visual cortex, varying acoustic intensity and duty cycle (350 kHz)
Target: visual cortex — “visual cortex”
Device: other named manufacturer · Channel Industries ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 350 | ✓✓✓ |
| Pulse duration (ms) | 0.5 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 100, 20, 166swept | ✓✓✓ |
| Duty cycle (%) | 5, 1, 8.3swept | ✓✓✓ |
| Sonication duration (s) | 150 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Isppa, domain unspecified (W/cm²) | 1, 3, 5swept | ✓✓✓⚑ |
| Ispta, domain unspecified (W/cm²) | 0.03, 0.05, 0.25swept | ✓✓✓⚑ |
VEPs (to strobe light) were sampled nine times every 150 s: three presonication baselines (B1-B3), one 150-s sonication period (S), and five recovery periods (R1-R5). A fixed 0.5-ms tone-burst duration was used throughout. Three ISPPA levels (1, 3, 5 W/cm2) were tested at a fixed 5% duty cycle (100 Hz PRF); two further duty cycles (1% at 20 Hz PRF, 8.3% at 166 Hz PRF) were tested at a fixed 3 W/cm2 ISPPA. A no-sonication control group (n=8) was also run. Repeated sonication sessions were conducted on the same 24 animals on different days, each with a different parameter set.
Flags from extraction
exposures[0].unspecified_domain.isppa_w_cm2— Domain of the reported intensities is unclear: the acoustic field was 'characterized in an ex-vivo setup' using a hydrophone, which does not clearly state whether this was a free-field (water tank) or through-tissue/through-skull measurement; recorded as unspecified domain rather than assumed free-field.exposures[0].unspecified_domain.ispta_w_cm2— Same domain ambiguity as ISPPA above. Values combine the 30 and 50 mW/cm2 ISPTA figures (from 3 W/cm2 x1% duty and 1 W/cm2 x5% duty) with the separately stated maximum of 250 mW/cm2 ISPTA (5 W/cm2 x5% duty).n_sessions_per_subject— The paper states 'repeated sonication sessions on the same animal ... each session ... performed on different days with different sonication parameter sets' but never gives a fixed number of sessions per animal; group sizes per parameter condition (n=10,9,9 for intensities; n=10,9 for duty cycles; n=8 control) suggest not every animal received every condition.sham_type— The paper describes only 'a control experiment ... under identical experimental conditions as the FUS experiment, but without any sonication (n=8)'; it does not explicitly state whether the transducer remained in place powered off. Classified as inactive_transducer as the closest vocabulary match.