Ultrasound-mediated neuromodulation is emerging as a key technology for targeted noninvasive brain stimulation, but key insights into its effects and dose-response characteristics are still missing. The purpose of this study is to systematically evaluate the effect of low-intensity transcranial ultrasound stimulation (TUS) on complementary aspects of cerebral hemodynamic. We simultaneously record the EMG signal, local field potential (LFP) and cortical blood flow (CBF) using electrophysiological recording and laser speckle contrast imaging under ultrasound stimulation to simultaneously monitor motor responses, neural activities and hemodynamic changes during the application of low-intensity TUS in mouse motor cortex, using excitation pulses which caused whisker and tail movement. Our experimental results demonstrate interdependent TUS-induced motor, neural activity and hemodynamic responses that peak approximately 0.55s, 1.05s and 2.5s after TUS onset, respectively, and show a linear coupling relationship between their respective varying response amplitudes to repeated stimuli. We also found monotonic dose-response parametric relations of the CBF peak value increase as a function of stimulation intensity and duration, while stimulus duty-cycle had only a weak effect on peak responses. These findings demonstrate that TUS induces a change in cortical hemodynamics and LSCI provide a high temporal resolution view of these changes.

Objective: Although low-intensity transcranial ultrasound stimulation (TUS) enhances=suppresses the neural oscillations and causes electroencephalography changes in the motor cortex, researchers have not clearly determined the manner in which the relative power and entropy of neural oscillations in the motor cortex vary with ultrasonic parameters, such as ultrasound intensity, stimulation duration, and duty cycle. Methods: In this study, we use transcranial ultrasound of different parameters to stimulate the mouse motor cortex, cause tail muscle contraction and movement, and simultaneously record local field potentials (LFPs) in the mouse motor cortex. The relative power and entropy of LFPs under different ultrasonic parameters are analyzed. Results: The relative power of the theta [4-8 Hz] frequency bands decreases with an increase in spatial-peak and pulse-average intensity ( $I_{sppa}$ ) at 0-0.5 s and 0.5-1 s; the relative power of the gamma [30-45 Hz] frequency bands increases with an increase in $I_{sppa}$ at 0-0.5 s and 0.5-1 s; the relative power of the gamma [30-45 Hz] and high gamma [55-100 Hz] frequency bands increase with an increase in stimulation duration (SD) at 0-0.5 s and 0.5-1 s; and the entropy values decrease with increases in $I_{sppa}$ and SD at 0-0.5 s. Conclusion: The relative power and entropy of neural oscillations in the motor cortex can be modulated by TUS with different parameters, namely, ultrasound intensity and stimulation duration.

Transcranial magneto-acoustical stimulation (TMAS) uses ultrasonic waves and a static magnetic field to generate electric current in nerve tissues for the purpose of modulating neuronal activities. It has the advantage of high spatial resolution and penetration depth. Neuronal firing rhythms carry and transmit nerve information in neural systems. In this study, we investigated the phase-locking characteristics of neuronal firing rhythms with TMAS based on the Hodgkin-Huxley neuron model. The simulation results indicate that the modulation frequency of ultrasound can affect the phase-locking behaviors. The results of this study may help us to explain the potential firing mechanism of TMAS.

Transcranial magneto-acoustical stimulation (TMAS) is a novel stimulation technology in which an ultrasonic wave within a magnetostatic field generates an electric current in an area of interest in the brain to modulate neuronal activities. As a key part of the neural network, neurons transmit information in the nervous system. However, the effect of TMAS on the neuronal firing rhythm remains unknown. To address this problem, we investigated the stimulatory mechanism of TMAS on neurons with a Hodgkin-Huxley neuron model. The simulation results indicate that the magnetostatic field intensity and ultrasonic power can affect the amplitude and interspike interval of neuronal action potential under continuous wave ultrasound. The simulation results also show that the ultrasonic power, duty cycle and repetition frequency can alter the firing rhythm of neural action potential under pulsed ultrasound. This study can help to reveal and explain the biological mechanism of TMAS and to provide a theoretical basis for TMAS in the treatment or rehabilitation of neuropsychiatric disorders.