To treat brain dysfunction and enhance plasticity in healthy adults, there is a need for new methods of noninvasively modulating neuronal activity. Since the 1950's US has been known capable of modulating electrically-evoked or sensory driven activity in brain circuits. These early observations implemented high-intensity US in a continuous wave mode for long durations and depended on the ability of US to focally heat tissue. The thermal effects of US (for example, HIFU) have been used to therapeutically ablate deep-brain circuits at intensities typically > 200 W/cm2. The peripheral and central nervous systems including the brain are mechanically sensitive. For example, voltage-gated ion channels and neurotransmitter receptors can be activated and inactivated (opened/closed) by mechanical pressures. Because of this we initiated investigations aimed at addressing the possibility of directly stimulating neurons with pulsed US via mechanical actions about a decade ago. This paper describes general information related to the use of US for neuromodulation and it non thermal actions on brain circuits.