Review of Neuromodulation Effects Due to Acoustic and Thermoacoustic Signals

Author(s):

Rebecca Laher and Robert Haupt

Abstract:

Recent efforts in the medical and defense fields aim to better understand how ultrasound modulates brain function. This report explores neuromodulation effects from acoustic signals in the brain originating from various sources, including a literature review of what is known from ultrasound applied transcranially via contact transducers. One way of applying ultrasound is with an RF source via the thermoacoustic effect. We explore the RF source parameters required to generate comparable levels of ultrasound in the brain as is generated via contact transducers for neuromodulation. Source carrier frequencies between 1 and 10 GHz are considered. Focusing effects of ultrasound at depth are also explored, suggesting the necessary peak RF powers could be of similar magnitude to the Institute of Electrical and Electronics Engineers safety standard given the right circumstances. This analysis assumes single pulses of RF that absorb in the neural tissue to generate ultrasound pressure waves. Further analysis is required to explore cumulative pulsing effects or generation of ultrasound in surface layers (e.g., the skull) and then traveling into the brain mass.