Focused ultrasound excites cortical neurons via mechanosensitive calcium accumulation and ion channel amplification

Potential of ultrasound stimulation and sonogenetics in vision restoration: a narrative review

Vision restoration presents a considerable challenge in the realm of regenerative medicine, while recent progress in ultrasound stimulation has displayed potential as a non-invasive therapeutic approach. This narrative review offers a comprehensive overview of current research on ultrasound-stimulated neuromodulation, emphasizing its potential as a treatment modality for various nerve injuries. By examining of the efficacy of different types of ultrasound stimulation in modulating peripheral and optic nerves, we can delve into their underlying molecular mechanisms. Furthermore, the review underscores the potential of sonogenetics in vision restoration, which involves leveraging pharmacological and genetic manipulations to inhibit or enhance the expression of related mechanosensitive channels, thereby modulating the strength of the ultrasound response. We also address how methods such as viral transcription can be utilized to render specific neurons or organs highly responsive to ultrasound, leading to significantly improved therapeutic outcomes.

Comparison of neural responses to whisker and ultrasound stimulation using a novel dual-stimulation protocol

BACKGROUND

The sensory system allows organisms to perceive and respond to environmental stimuli. This study investigates neural response differences between whisker and ultrasound stimulation in rats to evaluate cortical specificity to sensory inputs.

NEW METHOD

A novel dual-stimulation protocol combining a step motor and ultrasound system was developed to alternately stimulate the C2 whisker and corresponding barrel column region. Experiments were conducted under varying stimulation sequences (whisker-ultrasound and ultrasound-whisker) and time intervals (10 ms, 25 ms, and 100 ms). Neural response signals were recorded, and statistical analyses (ANOVA and T-test) were performed to compare response amplitudes and peak latencies.

RESULTS

Whisker stimulation consistently elicited significantly stronger neural responses than ultrasound stimulation (*p < 0.05), regardless of sequence or interval. The efficiency of neural responses to ultrasound was closely tied to frequency, with higher frequencies producing greater amplitudes and faster latencies. Notably, at a 25 ms interval in the ultrasound-whisker sequence, whisker responses were significantly enhanced compared to whisker stimulation alone, suggesting a pre-activation effect of ultrasound.

COMPARISON WITH EXISTING METHODS

Unlike single-modal whisker or ultrasound stimulation, the dual-stimulation protocol can enhance sensory responses, highlighting its neuromodulatory potential.

CONCLUSION

This study reveals distinct cortical activation patterns induced by whisker and ultrasound stimulation. While whisker stimulation is more sensitive, ultrasound stimulation-when optimized for frequency and timing-can effectively modulate neural responses under dual-stimulation protocol. These findings provide insights into ultrasound-based neuromodulation and sensory processing.

Temporal dynamics of offline transcranial ultrasound stimulation

Transcranial ultrasound stimulation (TUS) is a promising non-invasive neuromodulation modality, characterized by deep-brain accuracy and the capability to induce longer-lasting effects. However, most TUS datasets are underpowered, hampering efforts to identify TUS longevity and temporal dynamics. This primate case was studied awake with over 50 fMRI datasets, with and without left anterior hippocampus TUS. We therefore amassed the highest-powered TUS dataset to date required to reveal TUS longevity and dynamics. Most of the effects were found in the TUS region itself and alongside the default mode and sensorimotor networks. Seed-based functional connectivity exhibited a time-constrained alteration which dissipated ∼60 min post-TUS. Intrinsic activity measure and regional homogeneity displayed extended diffusivity and longer durations. This high-powered dataset allowed predicting TUS using pre-stimulation features that can now extend to modeling of individuals scanned less extensively. This case report reveals the diversity of TUS temporal dynamics to help to advance long-lasting human applications.

Advanced Strategies for Ultrasound Control and Applications in Sonogenetics and Gas Vesicle-Based Technologies: A Review

Control systems play an important role in the diagnosis and treatment of medicine. In contrast to light and magnetic fields, ultrasound has received much attention due to its non-invasive, cost-effective, convenient, and high spatiotemporal precision and deep-penetration characteristics. Some studies have developed special nanomaterials for therapy by controlling the production of reactive oxygen species through ultrasound irradiation. However, the complex functionalities and toxicity issues associated with these nanomaterials limit the development of ultrasound control systems. To overcome these challenges, ultrasound control systems based on synthetic biology have been developed, especially for sonogenetics and gas vesicles. The tunable thermal and mechanical effects of ultrasound act as the main triggering source, enabling engineered cells to perform sono-thermal or sono-mechanical genetic modifications in the targeted tissue. Based on an in-depth understanding of the relationship between ultrasound effects and the design, composition, and applications of engineered cellular technologies, in this review, we focus on recent activation strategies of ultrasound for sonogenetics and gas vesicles, including sono-thermal promoter switch, sono-thermal transient receptor potential channel, sono-mechanical activation and gas vesicles. In addition, applications of these advanced ultrasound control systems for cancer therapy, neural activity, visual recovery and functional imaging are presented. Finally, we discuss the current challenges faced and provide an outlook on the future developments in this evolving field.

Low Intensity Pulsed Ultrasound Activates Excitatory Synaptic Networks in Cultured Hippocampal Neurons

OBJECTIVE

Ultrasound can noninvasively penetrate deep into the brain for neuromodulation, demonstrating good potential for clinical application. However, the underlying mechanisms are unclear. So far most in vitro studies have focused on the activation of individual neurons by ultrasound with calcium imaging. As the focal region of ultrasound is typically millimeter or submillimeter size, it is important to investigate yet so far unclear how the mechanical effects of ultrasound would influence the synaptic circuit activity of neurons.

METHODS

Low-intensity pulse ultrasound was used to stimulate cultured hippocampal neurons. Postsynaptic currents were recorded in individual cells with the whole-cell patch-clamp technique. We also simultaneously imaged intracellular calcium, along with neuronal electrical signals, to resolve neuronal network dynamics during ultrasound stimulation.

RESULTS

Excitatory postsynaptic currents (EPSCs) were evoked by ultrasound in high-density neuronal cultures with increased frequency and amplitude, indicating enhanced glutamatergic synaptic transmission. The probability of evoking responses and the total charge of EPSCs increased with ultrasound intensity. Mechanistic analysis reveals that extracellular calcium influx, action potential firing and synaptic transmission are necessary for the responses to ultrasound in high-density culture. In contrast, EPSCs were not enhanced in low-density culture. Simultaneous calcium imaging of neuronal network activity indicates that recurrent excitatory network activity is recruited during ultrasound stimulation in high-density cultures, which lasts over tens to hundreds of seconds.

CONCLUSION

Our study provides insights into the mechanisms involved in the response of the brain to ultrasound and illuminates the potential to use ultrasound to regulate synaptic function in neurological disorders.

Genetics-Based Targeting Strategies for Precise Neuromodulation

Genetics-based neuromodulation schemes are capable of selectively manipulating the activity of defined cell populations with high temporal-spatial resolution, providing unprecedented opportunities for probing cellular biological mechanisms, resolving neuronal projection pathways, mapping neural profiles, and precisely treating neurological and psychiatric disorders. Multimodal implementation schemes, which involve the use of exogenous stimuli such as light, heat, mechanical force, chemicals, electricity, and magnetic stimulation in combination with specific genetically engineered effectors, greatly expand their application space and scenarios. In particular, advanced wireless stimulation schemes have enabled low-invasive targeted neuromodulation through local delivery of navigable micro- and nanosized stimulators. In this review, the fundamental principles and implementation protocols of genetics-based precision neuromodulation are first introduced.The implementation schemes are systematically summarized, including optical, thermal, force, chemical, electrical, and magnetic stimulation, with an emphasis on those wireless and low-invasive strategies. Representative studies are dissected and analyzed for their advantages and disadvantages. Finally, the significance of genetics-based precision neuromodulation is emphasized and the open challenges and future perspectives are concluded.

Progress and potential of nanobubbles for ultrasound-mediated drug delivery

INTRODUCTION

Despite much progress, nanomedicine-based drug therapies in oncology remain limited by systemic toxicity and insufficient particle accumulation in the tumor. To address these barriers, formulations responsive to external physical stimuli have emerged. One most promising system is the ultrasound stimulation of drug-loaded, gas-core particles (bubbles). Ultrasound induces bubble cavitation for cell and tissue permeabilization, triggers on-demand drug release, and provides opportunities for real-time imaging of delivery.

AREAS COVERED

Here, we focus on shell-stabilized, gas-core nanoparticles (also termed nanobubbles or ultrafine bubbles) and their role in ultrasound-mediated therapeutic delivery to tumors. This review frames the advantages of nanobubbles within the ongoing deficits in nanomedicine, describes mechanisms of ultrasound-mediated therapy, and details formulation techniques for nanobubble delivery systems. It then highlights the past decade of research in nanobubble-facilitated drug delivery for cancer therapy and anticipates new directions in the field.

EXPERT OPINION

Nanobubble ultrasound contrast agents offer a spatiotemporally triggerable therapeutic coupled with a safe, accessible imaging modality. Nanobubbles can be loaded with diverse therapeutic cargoes to treat disease and overcome numerous barriers limiting delivery to solid tumors. Close attention to formulation, characterization methods, acoustic testing parameters, and the biological mechanisms of nanobubble delivery will facilitate preclinical research toward clinical adoption.

Transcranial ultrasound stimulation in neuromodulation: a bibliometric analysis from 2004 to 2024

Background

Transcranial ultrasound stimulation (TUS) is a non-invasive neuromodulation technique with promising clinical potential. Its therapeutic efficacy and safety are significantly influenced by stimulation parameters. However, the global research hotspots and future research trends of TUS application in the field of rehabilitation are unclear. This study analyzes the status of TUS research. Understand the annual publication trends, international and institutional cooperation pattern and influential authors and journals and keyword hotspot.

Methods

A comprehensive literature search was conducted on the Web of Science core database using TUS-related subject headings until 27 December 2024. Two researchers independently screened articles based on pre-determined inclusion and exclusion criteria. Software packages such as CiteSpace and VOSviewer were used to visualize the results.

Results

A total of 577 literatures were included. The results show that the annual publication volume shows an increasing trend, reaching a peak in 2024. The United States, China and Germany dominated the number of publications, with the largest number of institutions being Harvard University, the University of Toronto and Brigham and Women's Hospital. Brain stimulation is the journal with the most articles and citations. Research hotspots include transcranial magnetic stimulation, noninvasive brain stimulation, Parkinson's disease, and Alzheimer's disease.

Conclusion

A bibliometric analysis of the literature shows that research interest in transcranial ultrasound stimulation is growing rapidly, with annual publications growing exponentially since 2013 and receiving increasing attention from researchers. The findings suggest that TUS is currently used primarily in neurological diseases, particularly in the study of Parkinson's disease and Alzheimer's disease. At the same time, it is found that an emerging international cooperation model with the partnership between the United States, China and Germany as the core has gradually taken shape. Although preclinical studies have shown promising neuromodulator effects, the current study suggests that TUS needs to undergo further multicenter clinical validation. These findings provide evidence to guide future research priorities for non-invasive neuromodulation.

Biophysical effects and neuromodulatory dose of transcranial ultrasonic stimulation

Transcranial ultrasonic stimulation (TUS) has the potential to usher in a new era for human neuroscience by allowing spatially precise and high-resolution non-invasive targeting of both deep and superficial brain regions. Currently, fundamental research on the mechanisms of interaction between ultrasound and neural tissues is progressing in parallel with application-focused research. However, a major hurdle in the wider use of TUS is the selection of optimal parameters to enable safe and effective neuromodulation in humans. In this paper, we will discuss the major factors that determine the efficacy of TUS. We will discuss the thermal and mechanical biophysical effects of ultrasound, which underlie its biological effects, in the context of their relationships with tunable parameters. Based on this knowledge of biophysical effects, and drawing on concepts from radiotherapy, we propose a framework for conceptualising TUS dose.

Deep transcranial ultrasound stimulation using personalized acoustic metamaterials improves treatment-resistant depression in humans

BACKGROUND

Neuromodulation of deep brain regions has shown promise for treatment-resistant depression (TRD). However, it currently requires neurosurgical electrode implantation, posing significant risks and limiting widespread use while TRD affects around 100 million people worldwide. Low-intensity transcranial ultrasound stimulation (TUS) could allow precise and non-invasive deep neuromodulation, provided that the challenge of the defocusing effects of the skull is tackled.

OBJECTIVE/HYPOTHESIS

Here, we present the development of a portable and neuronavigated TUS prototype based on the use of patient-specific metamaterials (metalens) that correct for skull-induced aberrations. We then present the first application of metalens-based Transcranial Ultrasound Stimulation (mTUS) in TRD. The primary objective was to assess the safety and efficacy of mTUS targeting on individual level specific white matter tracts of the subcallosal cingulate involved in TRD.

METHODS

The safety and precision of this device was addressed through a series of numerical simulations and experimental measurements on ex vivo human skulls. Five participants with TRD were included in this open-label study (ClinicalTrials.gov identifier: NCT06085950) and underwent an intensive 5-day course of mTUS with a total of 25 sessions of 5 min each.

RESULTS

No serious adverse events occurred during the study. By day 5 of treatment, depression severity was reduced by an average of 60.9 % (range: [30 %-83.9 %]), and four out of five patients qualified as responders, with two of them in remission.

CONCLUSIONS

This study provides first-in-human evidence of the potential of mTUS as a precise, safe and effective non-invasive neuromodulation technique for neuropsychiatric disorders involving deep brain regions, offering a safer and more accessible alternative to invasive approaches.

Acoustic-pressure-driven ultrasonic activation of the mechanosensitive receptor RET and of cell proliferation in colonic tissue

Ultrasound generates both compressive and shear mechanical forces in soft tissues. However, the specific mechanisms by which these forces activate cellular processes remain unclear. Here we show that low-intensity focused ultrasound can activate the mechanosensitive RET signalling pathway. Specifically, in mouse colon tissues ex vivo and in vivo, focused ultrasound induced RET phosphorylation in colonic crypts cells, which correlated with markers of proliferation and stemness when using hours-long insonication. The activation of the RET pathway is non-thermal, is linearly related to acoustic pressure and is independent of radiation-force-induced shear strain in tissue. Our findings suggest that ultrasound could be used to regulate cell proliferation, particularly in the context of regenerative medicine, and highlight the importance of adhering to current ultrasound-safety regulations for medical imaging.

Repeated neuromodulation with low-intensity focused ultrasound in patients with Alzheimer's disease

BackgroundLow-intensity focused ultrasound (LIFU), a non-invasive targeted brain stimulation technology, has shown promise for therapeutic applications in Alzheimer's disease (AD) patients. Despite its potential, the implications of repeated LIFU neuromodulation in AD patients remain to be investigated.ObjectiveThis pilot study evaluated the safety and potential to improve cognition and functional connectivity following repeated LIFU treatment in AD patients.MethodsTen early-stage AD patients underwent six sessions of neuronavigation-guided LIFU targeting the left dorsolateral prefrontal cortex (DLPFC) within 2-3 weeks, alongside ongoing standard pharmacotherapy. Neuropsychological assessments and resting-state functional magnetic resonance imaging were performed at baseline and eight weeks post-treatment.ResultsMemory performance (p = 0.02) and functional connectivity between the left DLPFC and both the left perirhinal cortex and left dorsomedial prefrontal cortex (corrected p < 0.05) significantly improved from baseline. Additionally, enhancements in memory performance were positively correlated with increases in functional connectivity of the left DLPFC with the left perirhinal cortex (Kendall's tau = 0.56, p = 0.03). No adverse events were reported during the LIFU treatments or at the subsequent follow-up.ConclusionsLIFU may have the therapeutic potential to enhance both brain network connectivity and memory functions in AD patients. Our results provide a basis for further research, including randomized sham-controlled trials and optimization of stimulation protocols, on LIFU as a supplementary or alternative treatment option for AD.Trial registrationClinical Research Information Service, KCT0008169, Registered on 10 February 2023.

Magnetite Nanodiscs Activate Mechanotransductive Calcium Signaling in Diverse Cell Types

Remote magnetomechanical stimulation using magnetic nanomaterials has emerged as a robust and minimally invasive technique for modulating neuronal activity. However, despite the presence of machinery to convert mechanical force into biochemical signals in many types of cells, magnetomechanical stimulation of non-neuronal tissue remains largely unexplored. Here, we demonstrate that in the presence of weak magnetic fields (12-56 mT) with frequencies 5-125 Hz, magnetite nanodiscs (MNDs) activate ubiquitous mechano-sensitive calcium signaling pathways, including transmembrane calcium entry, the release of intracellular calcium reserves, and store-operated calcium signaling. MNDs mediate calcium transients in cells with disparate calcium signaling machinery, such as cardiomyocytes and hippocampal astrocytes. The characteristics of these calcium responses depend on the protein machinery available in each cell type. These findings expand the reach of cellular modulation strategies using magnetic nanoparticles to non-neuronal cells and thereby open new applications probing endocrine, immune, and circulatory functions and related disorders with remote magnetic approaches.

Transcranial Functional Ultrasound Imaging Detects Focused Ultrasound Neuromodulation Induced Hemodynamic Changes In Vivo

Background

Focused ultrasound (FUS) is an emerging non-invasive technique for neuromodulation in the central nervous system (CNS). Functional ultrasound imaging (fUSI) leverages ultrafast Power Doppler Imaging (PDI) to detect changes in cerebral blood volume (CBV), which correlate well with neuronal activity and thus hold promise to monitor brain responses to FUS.

Objective

Investigate the immediate and short-term effects of transcranial FUS neuromodulation in the brain with fUSI by characterizing hemodynamic responses.

Methods

We designed a setup that aligns a FUS transducer with a linear array to allow immediate subsequent monitoring of the hemodynamic response with fUSI during and after FUS neuromodulation (FUS-fUSI) in lightly anesthetized mice. We investigated the effects of varying pressures and transducer positions on the hemodynamic responses.

Results

We found that higher FUS pressures increase the size of the activated brain area, as well as the magnitude of change in CBV and could show that sham sonications did not produce hemodynamic responses. Unilateral sonications resulted in bilateral hemodynamic changes with a significantly stronger response on the ipsilateral side. FUS neuromodulation in mice with a cranial window showed distinct activation patterns that were frequency-dependent and different from the activation patterns observed in the transcranial model.

Conclusion

fUSI is hereby shown capable of transcranially monitoring online and short-term hemodynamic effects in the brain during and following FUS neuromodulation.

Effects of skull properties on continuous-wave transcranial focused ultrasound transmission

Transcranial low-intensity focused ultrasound can deliver energy to the brain in a minimally invasive manner for neuromodulation applications. However, continuous sonication through the skull introduces significant wave interactions, complicating precise energy delivery to the target. This study presents a comprehensive examination of intracranial acoustic fields generated by focused ultrasound transducers and assesses the characteristics of cranial bone that affect acoustic transmission. Acoustic field maps were generated at 88 regions of interest across 10 historical and 2 Thiel-embalmed human skull specimens with sonication at frequencies of 220, 650, and 1000 kHz. The average peak pressure insertion losses for historical skulls were 3.6 ± 3.4, 9.3 ± 3.3, and 14.8 ± 5.8 dB, respectively, and for Thiel skulls, the respective losses were 2.9 ± 1.8, 9.4 ± 2.6, and 17.0 ± 5.5 dB. The effects of skull thickness, skull density ratio, and skull curvature on intracranial peak pressure, power, and focal area were investigated and linear fits produced. Several unfavorable focusing performances were observed in regions with excessive thickness variation. The effects of angulation and spacing between the transducer and the skull were also investigated. Preliminary findings indicate that wave superposition resulting from skull and transducer spacing could lead to a 30%-40% uncertainty in peak recorded intracranial pressure.

Applying Ultrasound to Mechanically and Noninvasively Sensitize Prostate Tumors to TRAIL-Mediated Apoptosis

Non-surgical and safe prostate cancer (PCa) therapies are in demand. Soluble tumor necrosis factor (TNF-α) related apoptosis inducing ligand (TRAIL), a cancer-specific drug, shows preclinical efficacy but has a short circulation half-life. This research has shown that physiological fluid shear stress activates mechanosensitive ion channels (MSCs), such as Piezo1, enhancing TRAIL-mediated apoptosis in cancer cells. Herein, noninvasive, focal ultrasound (FUS) is implemented to augment the pro-apoptotic effects of TRAIL. Using thermally safe FUS parameters, it is observed that TRAIL sensitivity increases with higher FUS pressure in PCa cells, mediated by Piezo1. This is confirmed by examining the effects of calcium chelation, MSC inhibitors, and PIEZO knockdown. In vivo, a multi-dose study with 10 min FUS exposure shows that 0 and 4-h intervals between TRAIL and FUS significantly reduce tumor burden, with an increase in apoptosis evident by enhanced cleaved-caspase 3 expression. This mechanotherapy offers a clinically translatable approach by utilizing widely available FUS technology, applicable to treat additional cancer types.

A mediator-free sonogenetic switch for therapeutic protein expression in mammalian cells

An ultrasound-responsive transgene circuit can provide non-invasive, spatiotemporally precise remote control of gene expression and cellular behavior in synthetic biology applications. However, current ultrasound-based systems often rely on nanoparticles or harness ultrasound's thermal effects, posing risks of tissue damage and cellular stress that limit their therapeutic potential. Here, we present Spatiotemporal Ultrasound-induced Protein Expression Regulator (SUPER), a novel gene switch enabling mediator-free, non-invasive and direct regulation of protein expression via ultrasound in mammalian cells. SUPER leverages the mammalian reactive oxygen species (ROS) sensing system, featuring KEAP1 (Kelch-like ECH-associated protein 1), NRF2 (nuclear factor erythroid 2-related factor 2), and antioxidant response element (ARE) as its core components. We demonstrate that low-intensity (1.5 W/cm2, ∼45 kHz), brief (40 s) ultrasound exposure generates non-toxic levels of ROS, activating the KEAP1/NRF2 pathway in engineered cells and leading to the controlled expression of target gene(s) via a synthetic ARE promoter. The system exhibits robust expression dynamics, excellent reversibility, and functionality in various cell types, including human mesenchymal stem cell-derived lines (hMSC-TERT). In a proof-of-concept study, ultrasound stimulation of subcutaneously implanted microencapsulated engineered cells stably expressing the sonogenetic circuit in a type 1 diabetic mouse model triggered sufficient insulin production to restore normoglycemia. Our work highlights ultrasound's potential as a precise and non-invasive tool for advancing cell and gene therapies in personalized medicine.

Parameter-dependent cell-type specific effects of transcranial focused ultrasound stimulation in an awake head-fixed rodent model

Objective.Transcranial focused ultrasound (tFUS) is a promising neuromodulation technique able to target shallow and deep brain structures with high precision. Previous studies have demonstrated that tFUS stimulation responses are cell-type specific, and specifically tFUS can elicit time-locked neural activity in regular spiking units (RSUs) that is sensitive to increases in pulse repetition frequency (PRF), while time-locked responses are not seen in fast spiking units (FSUs). These findings suggest a unique capability of tFUS to alter circuit network dynamics with cell-type specificity; however, these results could be biased by the use of anesthesia, which significantly modulates neural activities.Approach.In this study, we developed an awake head-fixed rat model specifically designed for simultaneous tFUS stimulation using a customized 128-element ultrasound array transducer, and recording of spiking data. Using this novel animal model, we examined a series of PRFs and burst duty cycles (DCs) to determine their effects on neuronal subpopulations without anesthesia.Main results.We observed cell type specific responses to varying PRF and DC in the awake setting as well as the anesthetized setting, with time locked responses observed in RSU and delayed responses in FSU. Anesthesia broadly was found to dampen responses to tFUS, and affected the latency of delayed responses. Preferred parameters for inducing time-locked responses appear to be 1500 Hz PRF and 60% DC.Significance.We conclude that despite some differences in response, isoflurane anesthesia is not a major confound in studying the cell-type specificity of ultrasound neuromodulation, but may affect studies of circuit dynamics and FSU. Our developed awake model will allow for future investigations without this confound.

Parameter optimisation for mitigating somatosensory confounds during transcranial ultrasonic stimulation

Transcranial ultrasonic stimulation (TUS) redefines what is possible with non-invasive neuromodulation by oaering unparalleled spatial precision and flexible targeting capabilities. However, peripheral confounds pose a significant challenge to reliably implementing this technology. While auditory confounds during TUS have been studied extensively, the somatosensory confound has been overlooked thus far. It will become increasingly vital to quantify and manage this confound as the field shifts towards higher doses, more compact stimulation devices, and more frequent stimulation through the temple where co-stimulation is more pronounced. Here, we provide a systematic characterisation of somatosensory co-stimulation during TUS. We also identify the conditions under which this confound can be mitigated most eaectively by mapping the confound-parameter space. Specifically, we investigate dose-response eaects, pulse shaping characteristics, and transducer-specific parameters. We demonstrate that somatosensory confounds can be mitigated by avoiding near-field intensity peaks in the scalp, spreading energy across a greater area of the scalp, ramping the pulse envelope, and delivering equivalent doses via longer, lower-intensity pulses rather than shorter, higher-intensity pulses. Additionally, higher pulse repetition frequencies and fundamental frequencies reduce somatosensory eaects. Through our systematic mapping of the parameter space, we also find preliminary evidence that particle displacement (strain) may be a primary biophysical driving force behind peripheral somatosensory co-stimulation. This study provides actionable strategies to minimise somatosensory confounds, which will support the thorough experimental control required to unlock the full potential of TUS for scientific research and clinical interventions.

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.

Individualized non-invasive deep brain stimulation of the basal ganglia using transcranial ultrasound stimulation

Transcranial ultrasound stimulation (TUS) offers precise, non-invasive neuromodulation, though its impact on human deep brain structures remains underexplored. Here we examined TUS-induced changes in the basal ganglia of 10 individuals with movement disorders (Parkinson's disease and dystonia) and 15 healthy participants. Local field potentials were recorded using deep brain stimulation (DBS) leads in the globus pallidus internus (GPi). Compared to sham, theta burst TUS (tbTUS) increased theta power during stimulation, while 10 Hz TUS enhanced beta power, with effects lasting up to 40 min. In healthy participants, a stop-signal task assessed tbTUS effects on the GPi, with pulvinar stimulation serving as an active sham. GPi TUS prolonged stop-signal reaction times, indicating impaired response inhibition, whereas pulvinar TUS had no effect. These findings provide direct electrophysiological evidence of TUS target engagement and specificity in deep brain structures, suggesting its potential as a noninvasive DBS strategy for neurological and psychiatric disorders.

The promise of transcranial focused ultrasound in disorders of consciousness: a narrative review

Transcranial focused ultrasound (tFUS) has emerged as a promising non-invasive neuromodulation technique for disorders of consciousness (DOC). This work critically evaluates tFUS's potential, highlighting its unique ability to precisely modulate deep brain structures, particularly the thalamus, while maintaining non-invasiveness. The mechanisms of action span multiple levels, from membrane-level ion channel modulation to network-wide changes in neural connectivity. Preclinical and early clinical studies have demonstrated tFUS's potential to improve DOC outcomes. Preliminary clinical trials in both acute and chronic DOC patients have shown encouraging results, including diagnostic category shifts, improvements in behavioral responsiveness, and alterations in thalamo-cortical connectivity. However, significant challenges remain. These include optimizing stimulation parameters, addressing variability in patient responses, and ensuring long-term safety. The current evidence base is limited, necessitating larger, more rigorous investigations. Future research should focus on multicenter randomized controlled trials to comprehensively evaluate tFUS across different DOC etiologies and chronicity. Key priorities include identifying predictive biomarkers, exploring combination therapies, and addressing ethical considerations. While tFUS shows significant promise in DOC management, further investigation is crucial to refine its application and establish its definitive clinical role.

Overview of Therapeutic Ultrasound Applications and Safety Considerations: 2024 Update

A 2012 review of therapeutic ultrasound was published to educate researchers and physicians on potential applications and concerns for unintended bioeffects (doi: 10.7863/jum.2012.31.4.623). This review serves as an update to the parent article, highlighting advances in therapeutic ultrasound over the past 12 years. In addition to general mechanisms for bioeffects produced by therapeutic ultrasound, current applications, and the pre-clinical and clinical stages are outlined. An overview is provided for image guidance methods to monitor and assess treatment progress. Finally, other topics relevant for the translation of therapeutic ultrasound are discussed, including computational modeling, tissue-mimicking phantoms, and quality assurance protocols.

Low-Intensity Pulsed Ultrasound Dynamically Modulates the Migration of BV2 Microglia

OBJECTIVE

Low-intensity pulsed ultrasound (LIPUS) is a promising modality for neuromodulation. Microglia are the resident immune cells in the brain and their mobility is critical for maintaining brain homeostasis and alleviating neuroimmune pathologies. However, it is unclear whether and how LIPUS modulates microglial migration in physiological conditions.

METHODS

Here we examined the in vitro effects of LIPUS on the mobility of BV2 microglia by live cell imaging. Single-cell tracing of BV2 microglia migration was analyzed using ImageJ and Chemotaxis and Migration Tool software. Pharmacological manipulation was performed to determine the key molecular players involved in regulating ultrasound-dependent microglia migration.

RESULTS

We found that the distance of microglial migration was enhanced by LIPUS with increasing acoustic pressure. Removing the extracellular Ca2+ influx or depletion of intracellular Ca2+ stores suppressed ultrasound-enhanced BV2 migration. Furthermore, we found that blocking the reorganization of actin, or suppressing purinergic signaling by application of apyrase or hemi-channel inhibitors, both diminished ultrasound-induced BV2 migration. LIPUS stimulation also enhanced microglial migration in a lipopolysaccharide (LPS)-induced inflammatory environment.

CONCLUSION

LIPUS promoted microglia migration in both physiological and inflammatory environments. Calcium, cytoskeleton, and purinergic signaling were involved in regulating ultrasound-dependent microglial mobility. Our study reveals the biomechanical impact of ultrasound on microglial migration and highlights the potential of using ultrasound-based tools for modulation of microglial function.

A practical guide to transcranial ultrasonic stimulation from the IFCN-endorsed ITRUSST consortium

Low-intensity Transcranial Ultrasonic Stimulation (TUS) is a non-invasive brain stimulation technique enabling cortical and deep brain targeting with unprecedented spatial accuracy. Given the high rate of adoption by new users with varying levels of expertise and interdisciplinary backgrounds, practical guidelines are needed to ensure state-of-the-art TUS application and reproducible outcomes. Therefore, the International Transcranial Ultrasonic Stimulation Safety and Standards (ITRUSST) consortium has formed a subcommittee, endorsed by the International Federation of Clinical Neurophysiology (IFCN), to develop recommendations for best practices in human TUS applications. The practical guide presented here provides a brief introduction into ultrasound physics and sonication parameters. It explains the requirements of TUS lab equipment and transducer selection and discusses experimental design and procedures alongside potential confounds and control conditions. Finally, the guide elaborates on essential steps of application planning for stimulation safety and efficacy, as well as considerations when combining TUS with neuroimaging, electrophysiology, or other brain stimulation techniques. We hope that this practical guide to TUS will assist both novice and experienced users in planning and conducting high-quality studies and provide a solid foundation for further advancements in this promising field.

Neuromodulation with Ultrasound: Hypotheses on the Directionality of Effects and Community Resource

Low-intensity Transcranial Ultrasound Stimulation is a promising non-invasive technique for brain stimulation and focal neuromodulation. Research with humans and animal models has raised the possibility that TUS can be biased towards enhancing or suppressing neural function. Here, we first collate a set of hypotheses on the directionality of TUS effects and conduct an initial meta-analysis on the available healthy human participant TUS studies reporting stimulation parameters and outcomes (n = 47 studies, 52 experiments). In these initial exploratory analyses, we find that parameters such as the intensity and continuity of stimulation (duty cycle) with univariate tests show only statistical trends towards likely enhancement or suppressed of function with TUS. Multivariate machine learning analyses are currently limited by the small sample size. Given that human TUS sample sizes will continue to increase, predictability on the directionality of TUS effects could improve if this database can continue to grow as TUS studies more systematically explore the TUS stimulation parameter space and report outcomes. Therefore, we establish an inTUS database and resource for the systematic reporting of TUS parameters and outcomes to assist in greater precision in TUS use for brain stimulation and neuromodulation. The paper concludes with a selective review of human clinical TUS studies illustrating how hypotheses on the directionality of TUS effects could be developed for empirical testing in the intended clinical application, not limited to the examples provided.

Advancements and prospects of transcranial focused ultrasound in pain neuromodulation

ABSTRACT

Transcranial focused ultrasound (tFUS) is an emerging noninvasive neuromodulation technology that has shown great potential in pain modulation. This review systematically elucidates the multilevel biological mechanisms of tFUS neuromodulation, from network-wide effects to cellular and molecular processes, as well as broader systemic influences. Preliminary animal pain model studies have revealed tFUS's ability to improve pain behavioral indicators and modulate neural circuit activity under pathological conditions. A small number of clinical studies also suggest that tFUS may have certain benefits in improving symptom experience and emotional state in chronic pain patients. However, current research generally has limitations such as small sample sizes and short follow-up periods. More high-quality studies are needed to verify the long-term effects and safety of tFUS pain treatment. Overcoming these limitations and advancing large-scale clinical translational research will help fully exploit the application potential of tFUS in precision pain medicine and provide new treatment options for pain relief.

PIEZO channels as multimodal mechanotransducers

All living beings experience a wide range of endogenous and exogenous mechanical forces. The ability to detect these forces and rapidly convert them into specific biological signals is essential to a wide range of physiological processes. In vertebrates, these fundamental tasks are predominantly achieved by two related mechanosensitive ion channels called PIEZO1 and PIEZO2. PIEZO channels are thought to sense mechanical forces through flexible transmembrane blade-like domains. Structural studies indeed show that these mechanosensory domains adopt a curved conformation in a resting membrane but become flattened in a membrane under tension, promoting an open state. Yet, recent studies suggest the intriguing possibility that distinct mechanical stimuli activate PIEZO channels through discrete molecular rearrangements of these domains. In addition, biological signals downstream of PIEZO channel activation vary as a function of the mechanical stimulus and of the cellular context. These unique features could explain how PIEZOs confer cells the ability to differentially interpret a complex landscape of mechanical cues.

Magnetic activation of electrically active cells

Magnetic control of cell activity has applications ranging from non-invasive neurostimulation to remote activation of cell-based therapies. Unlike other methods of regulating cell activity like heat and light, which are based on known receptors or proteins, no magnetically gated channel has been identified to date. As a result, effective approaches for magnetic control of cell activity are based on strong alternating magnetic fields able to induce electric fields or materials that convert magnetic energy into electrical, thermal, or mechanical energy to stimulate cells. In our investigations of magnetic cell responses, we found that a spiking HEK cell line with no other co-factors responds to a magnetic field that reaches a maximum of 500 mT within 200 ms using a permanent magnet. The response is rare, approximately 1 in 50 cells, but is fast and reproducible, generating an action potential within 200 ms of magnetic field stimulation. The magnetic field stimulation is over 10,000 times slower than the magnetic fields used in transcranial magnetic stimulation (TMS) and the induced electric field is more than an order of magnitude lower than necessary for neuromodulation, suggesting that induced electric currents do not drive the cell response. Instead, our calculation suggests that this response depends on mechanoreception pathways activated by the magnetic torque of TRP-associated lipid rafts. Despite the relatively rare response to magnetic stimulation, when cells form gap junctions, the magnetic stimulation can propagate to nearby cells, causing tissue-level responses. As an example, we co-cultured spiking HEK cells with beta-pancreatic MIN6 cells and found that this co-culture responds to magnetic fields by increasing insulin production. Together, these results point toward a method for the magnetic control of biological activity without the need for a material co-factor such as synthetic nanoparticles. By better understanding this mechanism and enriching for magneto-sensitivity it may be possible to adapt this approach to the rapidly expanding tool kit for wireless cell activity regulation.

Focused Ultrasound Modulates Dopamine in a Mesolimbic Reward Circuit

Dopamine is a neurotransmitter that plays a significant role in reward and motivation. Dysfunction in the mesolimbic dopamine pathway has been linked to a variety of psychiatric disorders, including addiction. Low-intensity focused ultrasound (LIFU) has demonstrated effects on brain activity, but how LIFU affects dopamine neurotransmission is not known. Here, we applied three different intensities (6.5, 13, and 26 W/cm2 ISPPA) of 2-min LIFU to the prelimbic cortex (PLC) and measured dopamine in the nucleus accumbens (NAc) core using fast-scan cyclic voltammetry. Two minutes of LIFU sonication at 13 W/cm2 to the PLC significantly reduced dopamine release by ~50% for up to 2 h. However, double the intensity (26 W/cm2) resulted in less inhibition (~30%), and half the intensity (6.5 W/cm2) did not result in any inhibition of dopamine. Anatomical controls applying LIFU to the primary somatosensory cortex did not change NAc core dopamine, and applying LIFU to the PLC did not affect dopamine release in the caudate or NAc shell. Histological evaluations showed no evidence of cell damage or death. Modeling temperature rise demonstrates a maximum temperature change of 0.5°C with 13 W/cm2, suggesting that modulation is not due to thermal mechanisms. These studies show that LIFU at a moderate intensity provides a noninvasive, high spatial resolution means to modulate specific mesolimbic circuits that could be used in future studies to target and repair pathways that are dysfunctional in addiction and other psychiatric diseases.

Low-intensity pulsed ultrasound reduces oxidative and endoplasmic reticulum stress in motor neuron cells

Endoplasmic reticulum (ER) stress is associated with oxidative stress, which is integral to the development of various pathological conditions, including neurodegenerative disorders. In this study, using NSC-34-a hybrid cell line established by fusing motor neuron-rich embryonic spinal cord cells with mouse neuroblastoma cells-we investigated the effects of low-intensity pulsed ultrasound (LIPUS) stimulation on oxidative (reactive oxygen species)/ER stress-induced neurodegeneration. An ultrasound transducer with a center frequency of 1.15 MHz and a spatial peak temporal average intensity of 357 mW/cm2 was used for delivering ultrasound (for 8 min, via a water-filled tube) to motor neuron cells seeded in a plastic culture dish. LIPUS stimulation significantly increased the level of the antiapoptotic protein B-cell lymphoma 2 (BCL-2) and inhibited the expression of apoptosis-associated proteins such as BCL-2-associated X protein (BAX), CCAAT/enhancer-binding protein-homologous protein (CHOP), and caspase-12, thus extending the survival of motor neurons. LIPUS stimulation also enhanced Ca2+ signaling and activated the Ca2+-dependent transcription factors as nuclear factor of activated T cells (NFAT) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Furthermore, LIPUS stimulation induced the activation of the serine/threonine kinase protein kinase B (AKT). Thus, LIPUS stimulation prevented oxidative/ER stress-mediated mitochondrial dysfunction. In conclusion, as a safe and noninvasive method, LIPUS stimulation can facilitate further development of ultrasound neuromodulation as a tool for neuroscience research.

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.

Exploring Cortical Interneurons in Substance Use Disorder: From Mechanisms to Therapeutic Perspectives

Interneurons (INs) play a crucial role in the regulation of neural activity within the medial prefrontal cortex (mPFC), a brain region critically involved in executive functions and behavioral control. In recent preclinical studies, dysregulation of INs in the mPFC has been implicated in the pathophysiology of substance use disorder, characterized by vulnerability to chronic drug use. Here, we explore the diversity of mPFC INs and their connectivity and roles in vulnerability to addiction. We also discuss how these INs change over time with drug exposure. Finally, we focus on noninvasive brain stimulation as a therapeutic approach for targeting INs in substance use disorder, highlighting its potential to restore neural circuits.

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.

Low-Intensity Ultrasound Tibial Nerve Stimulation Suppresses Bladder Activity in Rats

BACKGROUND AND OBJECTIVE

Noninvasive neuromodulation, particularly through low-intensity ultrasound, holds promise in the fields of neuroscience and neuro-engineering. Ultrasound can stimulate the central nervous system to treat neurologic disorders of the brain and activate peripheral nerve activity. The aim of this study is to investigate the inhibitory effect of low-intensity ultrasonic tibial nerve stimulation on both the physiological state and the overactive bladder (OAB) model in rats.

MATERIALS AND METHODS

A total of 28 female Sprague-Dawley rats were used in this study. Continuous transurethral instillation of 0.9% normal saline into the bladder was initially performed to stimulate physiological bladder activity. Subsequently, a solution containing 0.3% acetic acid dissolved in saline was instilled to induce rat models of OAB. The study comprised two phases: initial observation of bladder response to low-intensity ultrasound (1 MHz, 1 W/cm2, 50% duty cycle) in seven rats; subsequent exploration of ultrasound frequency (3 MHz) and intensity (2 W/cm2 and 3 W/cm2) effects in 21 rats. The intercontraction intervals (ICIs) were the primary outcome measure. Histologic analysis of tibial nerves and surrounding muscle tissues determined safe ultrasound parameters.

RESULTS

Low-intensity ultrasound tibial nerve stimulation significantly inhibited normal and OAB activity. Ultrasound stimulation at 1 MHz, 1 W/cm2, with a 50% duty cycle significantly prolonged the ICI in both normal (p < 0.0001) and OAB rats (p < 0.01), as did transitioning to a 3 MHz frequency (p = 0.001 for normal rats; p < 0.01 for OAB rats). Similarly, at an intensity of 2 W/cm2 and 1 MHz frequency with a 50% duty cycle, ultrasound stimulation significantly prolonged the ICI in both normal (p < 0.01) and OAB rats (p < 0.005). Furthermore, switching to a 3 W/cm2 ultrasound intensity also significantly extended the ICI in both normal (p < 0.05) and OAB rats (p = 0.01). However, after different ultrasound intensities and frequencies, there was no statistical difference in ICI ratios (preultrasound stimulation vs postultrasound stimulation/preultrasound stimulation ∗ 100%) in all rats (p > 0.05). Low-intensity ultrasound tibial nerve stimulation did not influence baseline pressure, threshold pressure, or maximum pressure. In addition, a latency period in bladder reflex inhibition was induced by low-intensity ultrasound tibial nerve stimulation in some rats. Histologic analysis indicated no evident nerve or muscle tissue damage or abnormalities.

CONCLUSIONS

This study confirmed the potential of transcutaneous ultrasound tibial nerve stimulation to improve bladder function. According to the findings, the ultrasonic intensities ranging from 1 to 3 W/cm2 and frequencies of 1 MHz and 3 MHz are both feasible and safe treatment parameters. This study portended the promise of low-intensity ultrasound tibial nerve stimulation as a treatment for OAB and provides a basis and reference for future clinical applications.

Programming mammalian cell behaviors by physical cues

In recent decades, the field of synthetic biology has witnessed remarkable progress, driving advances in both research and practical applications. One pivotal area of development involves the design of transgene switches capable of precisely regulating specified outputs and controlling cell behaviors in response to physical cues, which encompass light, magnetic fields, temperature, mechanical forces, ultrasound, and electricity. In this review, we delve into the cutting-edge progress made in the field of physically controlled protein expression in engineered mammalian cells, exploring the diverse genetic tools and synthetic strategies available for engineering targeting cells to sense these physical cues and generate the desired outputs accordingly. We discuss the precision and efficiency limitations inherent in these tools, while also highlighting their immense potential for therapeutic applications.

A Comprehensive Review of Low-Intensity Focused Ultrasound Parameters and Applications in Neurologic and Psychiatric Disorders

OBJECTIVES

Low-intensity focused ultrasound (LIFU) is gaining increased interest as a potential therapeutic modality for a range of neuropsychiatric diseases. Current neuromodulation modalities often require a choice between high spatial fidelity or invasiveness. LIFU is unique in this regard because it provides high spatial acuity of both superficial and deep neural structures while remaining noninvasive. This new form of noninvasive brain stimulation may provide exciting potential treatment options for a variety of neuropsychiatric disorders involving aberrant neurocircuitry within deep brain structures, including pain and substance use disorders. Furthermore, LIFU is compatible with noninvasive neuroimaging techniques, such as functional magnetic resonance imaging and electroencephalography, making it a useful tool for more precise clinical neuroscience research to further understand the central nervous system.

MATERIALS AND METHODS

In this study, we provide a review of the most recent LIFU literature covering three key domains: 1) the history of focused ultrasound technology, comparing it with other forms of neuromodulation, 2) the parameters and most up-to-date proposed mechanisms of LIFU, and finally, 3) a consolidation of the current literature to date surrounding the clinical research that has used LIFU for the modification or amelioration of several neuropsychiatric conditions.

RESULTS

The impact of LIFU including poststroke motor changes, pain, mood disorders, disorders of consciousness, dementia, and substance abuse is discussed.

CONCLUSIONS

Although still in its infancy, LIFU is a promising tool that has the potential to change the way we approach and treat neuropsychiatric disorders. In this quickly evolving field, this review serves as a snapshot of the current understanding of LIFU in neuropsychiatric research.

Parallelized Mechanical Stimulation of Neuronal Calcium Through Cell-Internal Nanomagnetic Forces Provokes Lasting Shifts in the Network Activity State

Neurons differentiate mechanical stimuli force and rate to elicit unique functional responses, driving the need for further tools to generate various mechanical stimuli. Here, cell-internal nanomagnetic forces (iNMF) are introduced by manipulating internalized magnetic nanoparticles with an external magnetic field across cortical neuron networks in vitro. Under iNMF, cortical neurons exhibit calcium (Ca2+) influx, leading to modulation of activity observed through Ca2+ event rates. Inhibiting particle uptake or altering nanoparticle exposure time reduced the neuronal response to nanomagnetic forces, exposing the requirement of nanoparticle uptake to induce the Ca2+ response. In highly active cortical networks, iNMF robustly modulates synchronous network activity, which is lasting and repeatable. Using pharmacological blockers, it is shown that iNMF activates mechanosensitive ion channels to induce the Ca2+ influx. Then, in contrast to transient mechanically evoked neuronal activity, iNMF activates Ca2+-activated potassium (KCa) channels to stabilize the neuronal membrane potential and induce network activity shifts. The findings reveal the potential of magnetic nanoparticle-mediated mechanical stimulation to modulate neuronal circuit dynamics, providing insights into the biophysics of neuronal computation.

Sonogenetics is a novel antiarrhythmic mechanism

Arrhythmia of the heart is a dangerous and potentially fatal condition. The current widely used treatment is the implantable cardioverter defibrillator (ICD), but it is invasive and affects the patient's quality of life. The sonogenetic mechanism proposed here focuses ultrasound on a cardiac tissue, controls endogenous stretch-activated Piezo1 ion channels on the focal region's cardiomyocyte sarcolemma, and restores normal heart rhythm. In contrast to anchoring the implanted ICD lead at a fixed position in the myocardium, the size and position of the ultrasound focal region can be selected dynamically by adjusting the signals of every piezoelectric chip on the ultrasonic phased array, and it allows novel and efficient defibrillations. Based on the developed interdisciplinary electro-mechanical model of sonogenetic treatment, our analysis shows that the proposed ultrasound intensity and frequency will be safe and painless for humans and well below the limits established by the U.S. Food and Drug Administration.

Novel NIBS in psychiatry: Unveiling TUS and TI for research and treatment

Mental disorders pose a significant global burden and constitute a major cause of disability worldwide. Despite strides in treatment, a substantial number of patients do not respond adequately, underscoring the urgency for innovative approaches. Traditional non-invasive brain stimulation techniques show promise, yet grapple with challenges regarding efficacy and specificity. Variations in mechanistic understanding and reliability among non-invasive brain stimulation methods are common, with limited spatial precision and physical constraints hindering the ability to target subcortical areas often implicated in the disease aetiology. Novel techniques such as transcranial ultrasonic stimulation and temporal interference stimulation have gained notable momentum in recent years, possibly addressing these shortcomings. Transcranial ultrasonic stimulation (TUS) offers exceptional spatial precision and deeper penetration compared with conventional electrical and magnetic stimulation techniques. Studies targeting a diverse array of brain regions have shown its potential to affect neuronal excitability, functional connectivity and symptoms of psychiatric disorders such as major depressive disorder. Nevertheless, challenges such as target planning and addressing acoustic interactions with the skull must be tackled for its widespread adoption in research and potentially clinical settings. Similar to transcranial ultrasonic stimulation, temporal interference (TI) stimulation offers the potential to target deeper subcortical areas compared with traditional non-invasive brain stimulation, albeit requiring a comparatively higher current for equivalent neural effects. Promising yet still sparse research highlights TI's potential to selectively modulate neuronal activity, showing potential for its utility in psychiatry. Overall, recent strides in non-invasive brain stimulation methods like transcranial ultrasonic stimulation and temporal interference stimulation not only open new research avenues but also hold potential as effective treatments in psychiatry. However, realising their full potential necessitates addressing practical challenges and optimising their application effectively.

Multimodal Characterization of Cortical Neuron Response to Permanent Magnetic Field Induced Nanomagnetic Force Maps

Nanomagnetic forces deliver precise mechanical cues to biological systems through the remote pulling of magnetic nanoparticles under a permanent magnetic field. Cortical neurons respond to nanomagnetic forces with cytosolic calcium influx and event rate shifts. However, the underlying consequences of nanomagnetic force modulation on cortical neurons remain to be elucidated. Here, we integrate electrophysiological and optical recording modalities with nanomagnetic forces to characterize the in vitro functional response to mechanical cues. Neurons exposed to chitosan functionalized magnetic nanoparticles for 24 h and then exposed to magnetic fields capable of generating forces of 2-160 pN present elevated cytosolic calcium in neurons and a time-dynamic electrophysiological spike rate and magnitude response. Extracellular recordings with microelectrode arrays revealed a 2-8 pN force-specific increase in electrophysiological spiking with a trend in reduced activity following 2 min of continuous force exposure. Nanomagnetic forces in the 16-160 pN range produced increased electrophysiological activity and remained excited for up to 4 h under continuous stimulation before silencing. Furthermore, the neuronal response to nanomagnetic forces at 16-160 pN can be electrophysiologically mediated without calcium influx by altering the magnetic nanoparticle-neuron interactions. These results demonstrate that low pN nanomagnetic forces mediate neuronal function and suggest that magnetic nanoparticle interactions and force magnitudes can be harnessed to provoke different responses in cortical neurons.

Noninvasive brain stimulation to improve motor outcomes after stroke

PURPOSE OF REVIEW

This review highlights recent developments in noninvasive brain stimulation (NIBS) techniques and applications for improving motor outcomes after stroke. Two promising areas of development relate to deep brain neuromodulation and the use of single-pulse transcranial magnetic stimulation (TMS) within a prediction tool for predicting upper limb outcome for individual patients.

RECENT FINDINGS

Systematic reviews highlight the inconsistent effect sizes of interventional NIBS for motor outcome after stroke, as well as limited evidence supporting the interhemispheric competition model. To improve the therapeutic efficacy of NIBS, studies have leveraged metaplasticity and priming approaches. Transcranial temporal interference stimulation (tTIS) and low-intensity focused ultrasound stimulation (LIFUS) are emerging NIBS techniques with potential for modulating deeper brain structures, which may hold promise for stroke neurorehabilitation. Additionally, motor evoked potential (MEP) status obtained with single-pulse TMS is a prognostic biomarker that could be used to tailor NIBS for individual patients.

SUMMARY

Trials of interventional NIBS to improve stroke outcomes may be improved by applying NIBS in a more targeted manner. This could be achieved by taking advantage of NIBS techniques that can be targeted to deeper brain structures, using biomarkers of structural and functional reserve to stratify patients, and recruiting patients in more homogeneous time windows.

Noninvasive targeted modulation of pain circuits with focused ultrasonic waves

ABSTRACT

Direct interventions into deep brain circuits constitute promising treatment modalities for chronic pain. Cingulotomy and deep brain stimulation targeting the anterior cingulate cortex have shown notable improvements in the unpleasantness of pain, but these interventions require brain surgeries. In this study, we have developed an approach that can modulate this deep brain affective hub entirely noninvasively, using low-intensity transcranial-focused ultrasound. Twenty patients with chronic pain received two 40-minute active or sham stimulation protocols and were monitored for one week in a randomized crossover trial. Sixty percent of subjects experienced a clinically meaningful reduction of pain on day 1 and on day 7 following the active stimulation, while sham stimulation provided such benefits only to 15% and 20% of subjects, respectively. On average, active stimulation reduced pain by 60.0% immediately following the intervention and by 43.0% and 33.0% on days 1 and 7 following the intervention. The corresponding sham levels were 14.4%, 12.3%, and 6.6%. The stimulation was well tolerated, and no adverse events were detected. Side effects were generally mild and resolved within 24 hours. Together, the direct, ultrasonic stimulation of the anterior cingulate cortex offers rapid, clinically meaningful, and durable improvements in pain severity.

NMDA Receptor-Mediated Ca2+ Flux Attenuated by the NMDA Receptor/TRPM4 Interface Inhibitor Brophenexin

Transient receptor potential melastatin-4 (TRPM4) forms a complex with N-methyl-D-aspartate receptors (NMDARs) that facilitates NMDAR-mediated neurotoxicity. Here we used pharmacological tools to determine how TRPM4 regulates NMDAR signaling. Brophenexin, a compound that binds to TRPM4 at the NMDAR binding interface, protected hippocampal neurons in culture from NMDA-induced death, consistent with published work. Brophenexin (10 μM) reduced NMDA-evoked whole-cell currents recorded at 22°C by 87% ± 14% with intracellular Ca2+ chelated to prevent TRPM4 activation. Brophenexin inhibited NMDA-evoked currents recorded in Na+-free solution by 87% ± 13%, suggesting that brophenexin and TRPM4 modulate NMDAR function. Incubating cultures in Mg2+-free buffer containing tetrodotoxin, 6-cyano-7-nitroquinoxaline-2,3-dione, and bicuculline for 30 min inhibited NMDA-evoked increases in intracellular Ca2+ concentration ([Ca2+]i) recorded at 22°C by 50% ± 18% and prevented inhibition by brophenexin. In the absence of these inhibitors, brophenexin inhibited the NMDA-evoked response by 51% ± 16%. Treatment with the TRPM4 inhibitor 4-chloro-2-(1-naphthyloxyacetamido)benzoic acid (NBA; 10 μM) increased NMDA-evoked Ca2+ influx by 90% ± 15%. Increasing extracellular NaCl to 237 mM, a treatment that activates TRPM4, inhibited the NMDA-evoked increase in [Ca2+]i by a process that occluded the inhibition produced by brophenexin and was prevented by NBA. In recordings performed at 32°C-34°C, brophenexin inhibited the NMDA-evoked [Ca2+]i response by 42% ± 10% but NBA was without effect. These results are consistent with a model in which TRPM4 interacts with NMDARs to potentiate Ca2+ flux through the NMDAR ion channel and thus provides a potential mechanism for the neuroprotection afforded by NMDAR/TRPM4 interface inhibitors such as brophenexin.

Sonogenetics in the Treatment of Chronic Diseases: A New Method for Cell Regulation

Sonogenetics is an innovative technology that integrates ultrasound with genetic editing to precisely modulate cellular activities in a non-invasive manner. This method entails introducing and activating mechanosensitive channels on the cell membrane of specific cells using gene delivery vectors. When exposed to ultrasound, these channels can be manipulated to open or close, thereby impacting cellular functions. Sonogenetics is currently being used extensively in the treatment of various chronic diseases, including Parkinson's disease, vision restoration, and cancer therapy. This paper provides a comprehensive review of key components of sonogenetics and focuses on evaluating its prospects and potential challenges in the treatment of chronic disease.

Medical Ultrasound Application Beyond Diagnosis: Insights From Ultrasound Sensing and Biological Response

Ultrasound (US) can easily penetrate media with excellent spatial precision corresponding to its wavelength. Naturally, US plays a pivotal role in the echolocation abilities of certain mammals such as bats and dolphins. In addition, medical US generated by transducers interact with tissues via delivering ultrasonic energy in the modes of heat generation, exertion of acoustic radiation force (ARF), and acoustic cavitation. Based on the principle of echolocation, various assistive devices for visual impairment people have been developed. High-Intensity Focused Ultrasound (HIFU) are developed for targeted ablation and tissue destruction. Besides thermal ablation, histotripsy with US is designed to damage tissue purely via mechanical effect without thermal coagulation. Low-Intensity Focused Ultrasound (LIFU) has been proven to be an effective stimulation method for neuromodulation. Furthermore, US has been reported to transiently increase the permeability of biological membranes, enabling acoustic transfection and blood-brain barrier open. All of these advances in US are changing the clinic. This review mainly introduces the advances in these aspects, focusing on the physical and biological principles, challenges, and future direction.

Acoustic virtual 3D scaffold for direct-interacting tumor organoid-immune cell coculture systems

Three-dimensional (3D) cell culture has revolutionized life sciences, particularly in organoid technologies. Traditional bioscaffold materials, however, complicate the detachment of tumor organoids and hamper the routine use of organoid-immune cell cocultures. Here, we show an acoustic virtual 3D scaffold (AV-Scaf) method to achieve 3D tumor organoid culture, enabling a direct-interacting tumor organoid-immune cell coculture system. The self-organization process of tumor cells is facilitated by a vortex acoustic field, which enables the cell bioassembly and ion channel activation. This approach can significantly enhance the influx of calcium ions, thereby accelerating intercellular interactions of cellular assemblies. We established scaffold-free melanoma and breast cancer organoids using AV-Scaf and cocultured melanoma organoids with T cells. We found that our coculture system resulted in a high activation state of T cells, characterized by notable up-regulation of granzyme B (2.82 to 17.5%) and interferon-γ (1.36 to 16%). AV-Scaf offers an efficient method for tumor organoid-immune cell studies, advancing cancer research and immunotherapy development.

Focused ultrasound for treatment of epilepsy: a systematic review and meta-analysis of preclinical and clinical studies

Various preclinical and clinical studies have demonstrated the neuromodulatory and ablative effects of focused ultrasound (FUS). However, the safety and efficacy of FUS in clinical settings for treating epilepsy have not been well established. This study aims to provide a systematic review of all preclinical and clinical studies that have used FUS for the treatment of epilepsy. A systematic search was conducted using Scopus, Web of Science, PubMed, and Embase databases. All preclinical and clinical studies reporting outcomes of FUS in the treatment of epilepsy were included in the systematic review. Random-effect meta-analysis was performed to determine safety in clinical studies and seizure activity reduction in preclinical studies. A total of 24 articles were included in the study. Meta-analysis demonstrated that adverse events occurred in 13% (95% CI = 2-57%) of patients with epilepsy who underwent FUS. The frequency of adverse events was higher with the use of FUS for lesioning (36%, 95% CI = 4-88%) in comparison to neuromodulation (5%, 95% CI = 0-71%), although this difference was not significant (P = 0.31). Three-level meta-analysis in preclinical studies demonstrated a reduced spike rate in neuromodulating FUS compared to the control group (P = 0.02). According to this systematic review and meta-analysis, FUS can be considered a safe and feasible approach for treating epileptic seizures, especially in drug-resistant patients. While the efficacy of FUS has been demonstrated in several preclinical studies, further research is necessary to confirm its effectiveness in clinical practice and to determine the adverse events.