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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 (VEP) 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 spatial-peak pulse-average acoustic intensity of 3 W/cm2; 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 of 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 also can enhance the excitability depending on the acoustic intensity and 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.

BackgroundAn ovine model can cast great insight in translational neuroscientific research due to its large brain volume and distinct regional neuroanatomical structures. The present study examined the applicability of brain functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to sheep using a clinical MR scanner (3 tesla) with a head coil. The blood-oxygenation-level-dependent (BOLD) fMRI was performed on anesthetized sheep during the block-based presentation of external tactile and visual stimuli using gradient echo-planar-imaging (EPI) sequence.ResultsThe individual as well as group-based data processing subsequently showed activation in the eloquent sensorimotor and visual areas. DTI was acquired using 26 differential magnetic gradient directions to derive directional fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values from the brain. White matter tractography was also applied to reveal the macrostructure of the corticospinal tracts and optic radiations.ConclusionsUtilization of fMRI and DTI along with anatomical MRI in the sheep brain could shed light on a broader use of an ovine model in the field of translational neuroscientific research targeting the brain.