Transcranial ultrasound axicon-driven activation of the motor cortex in anaesthetised mice

FABIÁN ACQUATICCI; JUAN F. GUARRACINO; ADRIANA LOSAVIO; SERGIO N. GWIRC; SERGIO E. LEW

Mar del Plata

Congreso; XXX Congreso Anual Sociedad Argentina de Investigación en Neurociencias; 2015

Sociedad Argentina de Investigación en Neurociencias

In this work we study the acoustic characteristics of ultrasonic transducers for transcranial transmission of focused ultrasound with the addition of axicon lenses. We made a comparison between this combination and a standard transducer directly coupled for transmitting pulsed ultrasound through the skin and skull into the intact brains. We implemented an ultrasonic propagating model based on a k-space pseudo-spectral scheme in 2D that takes in consideration the acoustic velocities and densities of the liquid in the transducer-lens interface, the lens material and the biological tissue. The setup used in this case was: 140° Axicon lens?Epoxy resin, 0.45MHz?Ø28mm transducer, vacuum oil, Stand-off: 30mm.The motor cortex of CF-1 mice (n=3) was then stimulated with pulsed ultrasound (160c/p, 1kHz PRF, 300 pulses) having an ISPTA = 87mW/cm2. Evoked motor responses in different body segments could be clearly observed, including whiskers, hindlimb, forelimb and tail.Axicon lens produce a narrow beam at the focus, compared with non-focused transducer. In this case we have a focus, with a -6dB drop, smaller than 2.0 mm in diameter which is approximately five times better than the lateral spatial resolution offered by other more conventional noninvasive brain stimulation methods. Out of the focus the sound pressure decreases with a very steep slope. Based on those observations, it is reasonable to expect that brain regions