Special Collection: Transcranial Ultrasound Neuromodulation
- Ultrasound (US) is known to non-invasively stimulate and modulate brain function; however, the mechanism of action is poorly understood. This study tested US stimulation of rat motor cortex (100 W/cm2, 200 kHz) in combination with epidural cortical stimulation. US directly evoked hindlimb movement. This response occurred even with short US bursts (3 ms) and had short latency (10 ms) and long refractory (3 s) periods. Unexpectedly, the epidural cortical stimulation hindlimb response was not altered during the 3-s refractory period of the US hindlimb response.
- Non-invasive brain stimulation using focused ultrasound has largely been carried out in small animals. In the present study, we applied stimulatory focused ultrasound transcranially to the primary sensorimotor (SM1) and visual (V1) brain areas in sheep (Dorset, all female, n = 8), under the guidance of magnetic resonance imaging, and examined the electrophysiologic responses. By use of a 250-kHz focused ultrasound transducer, the area was sonicated in pulsed mode (tone-burst duration of 1 ms, duty cycle of 50%) for 300 ms.
- Nonpharmacologic and nonsurgical transcranial modulation of the nerve function may provide new opportunities in evaluation and treatment of cranial nerve diseases. This study investigates the possibility of using low-intensity transcranial focused ultrasound (FUS) to selectively stimulate the rat abducens nerve located above the base of the skull. FUS (frequencies of 350 kHz and 650 kHz) operating in a pulsed mode was applied to the abducens nerve of Sprague-Dawley rats under stereotactic guidance.
- The application of focused, pulsed ultrasound was studied as a method of modifying the activity of a local neural circuit of the mammalian brain. An in vitro hippocampal preparation was used to facilitate delivery, dosimetry and assessment of mechanisms of ultrasound effects. Extracellular evoked potentials were recorded from cell and dendritic layers of the rat hippocampal dentate gyrus. Focused pulses of ultrasound with center frequency of 500 kHz and repetition rate of 200 kHz were studied and found both to enhance and to depress electrically evoked field potentials.