Ultrasound modulates neuronal potassium currents via ionotropic glutamate receptors

Low-intensity transcranial ultrasound stimulation and its regulatory effect on pain

Transcranial ultrasound stimulation is an emerging non-invasive neuromodulation technology with the advantages of deep tissue penetration, high spatial resolution, and minimal side effects. Low intensity transcranial ultrasound stimulation (LITUS) has been shownto bea promising neuromodulation treatment for psychiatric and neurological disorders. Notably, significant progress has been made recently in both the application of LITUS in pain disorders and the elucidation of its analgesic mechanisms. This review provides an overview of LITUS and its state-of-the-art mechanisms, including cavitation, mechanical, and thermal effects. We summarize studies spanning from animal models to human trials, highlighting the analgesic effects of transcranial ultrasound stimulation on pain-related neural pathways. Furthermore, we explore potential analgesic mechanisms, such as the suppression of neural activity in the ascending pain pathway and other associated processes.Lastly, we discuss the potential of LITUS for future integrative treatments of chronic pain and psychomotor disorders, as well as its broader therapeutic applications.

Ultrasound-Induced Synchronized Neural Activities at 40 Hz and 200 Hz Entrained Corresponded Oscillations and Improve Alzheimer's Disease Memory

AIMS

Neurological diseases like Alzheimer's disease (AD) with cognitive deficits show impaired theta, gamma, and ripple bands. Restoring these oscillations may be crucial for rescuing cognitive functions. Low-intensity transcranial ultrasound stimulation (TUS), a noninvasive neuromodulation method, offers high spatial resolution and deep penetration. However, it remains unclear how 40 Hz and 200 Hz TUS may improve memory in AD by regulating hippocampal oscillations.

METHODS

We applied 40 Hz and 200 Hz TUS to the CA1 region of AD mice, performing memory assessments and CA1 electrophysiology recordings simultaneously.

RESULTS

Our results showed that both 40 Hz and 200 Hz TUS significantly improved memory performance in AD mice by targeting the dorsal hippocampus and increasing power in corresponding frequency bands. Specifically, 40 Hz TUS enhanced gamma and ripple bands, while 200 Hz TUS strongly affected both. This enhancement increased during stimulation and persisted 5 days poststimulation. Improved coupling between theta and gamma oscillations indicated better hippocampal coordination with other brain regions. Additionally, 40 Hz TUS raised sharp wave ripple (SPW-Rs) incidence, and 200 Hz TUS increased both SPW-R incidence and duration, contributing to memory improvement. Behavioral performance significantly improved with TUS at both frequencies.

CONCLUSION

Ultrasound-induced synchronized neural activities at 40 Hz and 200 Hz entrained corresponding oscillations and improved memory in Alzheimer's disease.

Mechanistic insights into the neuroprotective effects of low-intensity transcranial ultrasound stimulation in post-cardiac arrest brain injury: Modulation of the Piezo1-Dkk3/PI3K-Akt pathway

Post-cardiac arrest brain injury (PCABI) remains a significant challenge, marked by high mortality and disability rates due to persistent neuroinflammation. This study explored the neuroprotective potential of low-intensity transcranial ultrasound stimulation (LITUS) in mitigating brain damage after cardiopulmonary resuscitation (CPR) using a murine model and in vitro assays. LITUS treatment improved 24-h survival rates and neurological recovery in cardiac arrest (CA) mice, as evidenced by behavioral assessments and reduced neurological deficit scores. Proteomic analyses revealed modulation of Piezo1-Dkk3/PI3K-Akt signaling pathway, characterized by decreased pro-inflammatory cytokines (IL-1β, IL-6, TNF-α). Mechanistic studies demonstrated that LITUS enhanced Piezo1 and Dkk3 activation, promoting calcium influx and anti-inflammatory responses. The Piezo1 antagonist GsMTx4 abrogated these effects, underscoring Piezo1's specific role. Additionally, in vitro experiments using oxygen/glucose deprivation and reoxygenation (OGD/R)-treated BV2 microglial cells confirmed that LITUS reduced inflammatory responses and enhanced cellular recovery via the Piezo1-Dkk3 axis. These findings highlight LITUS as a promising non-invasive therapeutic strategy to ameliorate PCABI by modulating neuroinflammation through the Piezo1-Dkk3/PI3K-Akt pathway. This work provides a basis for translational research and potential clinical applications in improving outcomes for CPR survivors.

Advances in transcranial focused ultrasound neuromodulation for mental disorders

Mental disorders are a major public health concern, affecting millions worldwide. Current treatments have limitations, highlighting the need for novel, effective, and safe interventions. Transcranial focused ultrasound (tFUS), a non-invasive neuromodulation technology, has emerged as a promising tool for treating mental disorders due to its high controllability, precision, and safety. This review summarizes the research progress of tFUS in several major mental disorders, including depression, anxiety, schizophrenia, and substance use disorders (SUDs). Animal studies have demonstrated the efficacy of tFUS in improving psychiatric symptoms and modulating neural circuits through various mechanisms, such as enhancing neuronal activity, synaptic plasticity, and neurotransmitter release. Preliminary clinical trials have also shown the potential of tFUS in alleviating symptoms in patients with treatment-resistant mental disorders. Safety evaluation studies across in vitro, animal, and human levels have supported the overall safety of tFUS under commonly used parameters. tFUS has shown broad application prospects in treating mental disorders, supported by its efficacy in animal models and preliminary clinical trials. By modulating neuronal activity, synaptic plasticity, neurotransmitters, and brain networks, tFUS could improve psychiatric symptoms and regulate neural circuits. However, current research on tFUS in mental disorders is still in its early stages, and further studies are needed to elucidate its mechanisms of action, expand its applications, and conduct large-sample, long-term clinical trials to systematically evaluate its efficacy, protocol optimization, and safety. As an innovative neuromodulation technology, tFUS has the potential to complement conventional therapies and provide new hope for addressing the global challenge of mental disorders.

Label free, capillary-scale blood flow mapping in vivo reveals that low-intensity focused ultrasound evokes persistent dilation in cortical microvasculature

Non-invasive, low intensity focused ultrasound is an emerging neuromodulation technique that offers the potential for precision, personalized therapy. An increasing body of research has identified mechanosensitive ion channels that can be modulated by FUS and support acute electrical activity in neurons. However, neuromodulatory effects that persist from hours to days have also been reported. The brain's ability to provide blood flow to electrically active regions involves a multitude of non-neuronal cell types and signaling pathways in the cerebral vasculature; an open question is whether persistent effects can be attributed, at least partly, to vascular mechanisms. Using an in vivo optical approach, we found that microvasculature, and not larger vessels, exhibit significant persistent dilation following sonication without the use of microbubbles. This finding reveals a heretofore unseen aspect of the effects of FUS in vivo and indicates that concurrent changes in neurovascular function may partially underly persistent neuromodulatory effects.

L-Type Calcium Channel Modulates Low-Intensity Pulsed Ultrasound-Induced Excitation in Cultured Hippocampal Neurons

As a noninvasive technique, ultrasound stimulation is known to modulate neuronal activity both in vitro and in vivo. The latest explanation of this phenomenon is that the acoustic wave can activate the ion channels and further impact the electrophysiological properties of targeted neurons. However, the underlying mechanism of low-intensity pulsed ultrasound (LIPUS)-induced neuro-modulation effects is still unclear. Here, we characterize the excitatory effects of LIPUS on spontaneous activity and the intracellular Ca2+ homeostasis in cultured hippocampal neurons. By whole-cell patch clamp recording, we found that 15 min of 1-MHz LIPUS boosts the frequency of both spontaneous action potentials and spontaneous excitatory synaptic currents (sEPSCs) and also increases the amplitude of sEPSCs in hippocampal neurons. This phenomenon lasts for > 10 min after LIPUS exposure. Together with Ca2+ imaging, we clarified that LIPUS increases the [Ca2+]cyto level by facilitating L-type Ca2+ channels (LTCCs). In addition, due to the [Ca2+]cyto elevation by LIPUS exposure, the Ca2+-dependent CaMKII-CREB pathway can be activated within 30 min to further regulate the gene transcription and protein expression. Our work suggests that LIPUS regulates neuronal activity in a Ca2+-dependent manner via LTCCs. This may also explain the multi-activation effects of LIPUS beyond neurons. LIPUS stimulation potentiates spontaneous neuronal activity by increasing Ca2+ influx.

Advances in using ultrasound to regulate the nervous system

Ultrasound is a mechanical vibration with a frequency greater than 20 kHz. Due to its high spatial resolution, good directionality, and convenient operation in neural regulation, it has recently received increasing attention from scientists. However, the mechanism by which ultrasound regulates the nervous system is still unclear. This article mainly explores the possible mechanisms of ultrasound's mechanical effects, cavitation effects, thermal effects, and the rise of sonogenetics. In addition, the essence of action potential and its relationship with ultrasound were also discussed. Traditional theory treats nerve impulses as pure electrical signals, similar to cable theory. However, this theory cannot explain the phenomenon of inductance and cell membrane bulging out during the propagation of action potential. Therefore, the flexoelectric effect of cell membrane and soliton model reveal that action potential may also be a mechanical wave. Finally, we also elaborated the therapeutic effect of ultrasound on nervous system disease such as epilepsy, Parkinson's disease, and Alzheimer's disease.

Transcranial focused ultrasound activates feedforward and feedback cortico-thalamo-cortical pathways by selectively activating excitatory neurons

Transcranial focused ultrasound stimulation (tFUS) has been proven capable of altering focal neuronal activities and neural circuits non-invasively in both animals and humans. The abilities of tFUS for cell-type selection within the targeted area like somatosensory cortex have been shown to be parameter related. However, how neuronal subpopulations across neural pathways are affected, for example how tFUS affected neuronal connections between brain areas remains unclear. In this study, multi-site intracranial recordings were used to quantify the neuronal responses to tFUS stimulation at somatosensory cortex (S1), motor cortex (M1) and posterior medial thalamic nucleus (POm) of cortico-thalamo-cortical (CTC) pathway. We found that when targeting at S1 or POm, only regular spiking units (RSUs, putative excitatory neurons) responded to specific tFUS parameters (duty cycle: 6%-60% and pulse repetition frequency: 1500 and 3000 Hz ) during sonication. RSUs from the directly connected area (POm or S1) showed a synchronized response, which changed the directional correlation between RSUs from POm and S1. The tFUS induced excitation of RSUs activated the feedforward and feedback loops between cortex and thalamus, eliciting delayed neuronal responses of RSUs and delayed activities of fast spiking units (FSUs) by affecting local network. Our findings indicated that tFUS can modulate the CTC pathway through both feedforward and feedback loops, which could influence larger cortical areas including motor cortex.

Spatiotemporal Distributions of Acoustic Propagation in Skull During Ultrasound Neuromodulation

There is widespread interest and concern about the evidence and hypothesis that the auditory system is involved in ultrasound neuromodulation. We have addressed this problem by performing acoustic shear wave simulations in mouse skull and behavioral experiments in deaf mice. The simulation results showed that shear waves propagating along the skull did not reach sufficient acoustic pressure in the auditory cortex to modulate neurons. Behavioral experiments were subsequently performed to awaken anesthetized mice with ultrasound targeting the motor cortex or ventral tegmental area (VTA). The experimental results showed that ultrasound stimulation (US) of the target areas significantly increased arousal scores even in deaf mice, whereas the loss of ultrasound gel abolished the effect. Immunofluorescence staining also showed that ultrasound can modulate neurons in the target area, whereas neurons in the auditory cortex required the involvement of the normal auditory system for activation. In summary, the shear waves propagating along the skull cannot reach the auditory cortex and induce neuronal activation. Ultrasound neuromodulation-induced arousal behavior needs direct action on functionally relevant stimulation targets in the absence of auditory system participation.

A Miniature Ultrasound Source for Neural Modulation

This work describes a unique ultrasound (US) exposure system designed to create very localized ( [Formula: see text]) sound fields at operating frequencies that are currently being used for preclinical US neuromodulation. This system can expose small clusters of neuronal tissue, such as cell cultures or intact brain structures in target animal models, opening up opportunities to examine possible mechanisms of action. We modified a dental descaler and drove it at a resonance frequency of 96 kHz, well above its nominal operating point of 28 kHz. A ceramic microtip from an ultrasonic wire bonder was attached to the end of the applicator, creating a 100- [Formula: see text] point source. The device was calibrated with a polyvinylidene difluoride (PVDF) membrane hydrophone, in a novel, air-backed, configuration. The experimental results were confirmed by simulation using a monopole model. The results show a consistent decaying sound field from the tip, well-suited to neural stimulation. The system was tested on an existing neurological model, Drosophila melanogaster, which has not previously been used for US neuromodulation experiments. The results show brain-directed US stimulation induces or suppresses motor actions, demonstrated through synchronized tracking of fly limb movements. These results provide the basis for ongoing and future studies of US interaction with neuronal tissue, both at the level of single neurons and intact organisms.

Modulation effects of low-intensity transcranial ultrasound stimulation on the neuronal firing activity and synaptic plasticity of mice

Low-intensity transcranial ultrasound stimulation (TUS) has been effective in modulating several neurological and psychiatric disorders. However, how TUS modulates neuronal firing activity and synaptic plasticity remains unclear. Thus, we behaviorally tested the whisker-dependent novel object discrimination ability in mice after ultrasound stimulation and examined the cortical neuronal firing activity and synaptic plasticity in awake mice after ultrasound stimulation by two-photon fluorescence imaging. The current study presented the following results: (1) TUS could significantly improve the whisker-dependent new object discrimination ability of mice, suggesting that their learning and memory abilities were significantly enhanced; (2) TUS significantly enhanced neuronal firing activity; and (3) TUS increased the growth rate of dendritic spines in the barrel cortex, but did not promote the extinction of dendritic spines, resulting in enhanced synaptic plasticity. The above results indicate that TUS can improve the learning and memory ability of mice and enhance the neuronal firing activity and synaptic plasticity that are closely related to it. This study provides a research basis for the application of ultrasound stimulation in the treatment of learning- and memory-related diseases.