Figure 6. Illustration of indirect auditory effects of ultrasonic neuromodulation.
(1) Ultrasound application leads to mechanical waves stimulating the inner ear structures of the cochlea. (2) The activation of the cochlea leads to excitation of auditory pathways, including the contralateral auditory cortex. (3) Cross-modal projections from these auditory regions lead to modulation of neural activity across the cortex, including the neurons that are within the focal zone of ultrasound. The timing and sign of this modulation is nearly identical to that caused by air-coupled sound. (4) The auditory percept can also lead to startle-like motor responses.