Transcranial Pulse Stimulation with Ultrasound in Alzheimer's Disease-A New Navigated Focal Brain Therapy

Repetitive transcranial magnetic stimulation in Alzheimer's disease: effects on neural and synaptic rehabilitation

Alzheimer's disease is a neurodegenerative disease resulting from deficits in synaptic transmission and homeostasis. The Alzheimer's disease brain tends to be hyperexcitable and hypersynchronized, thereby causing neurodegeneration and ultimately disrupting the operational abilities in daily life, leaving patients incapacitated. Repetitive transcranial magnetic stimulation is a cost-effective, neuro-modulatory technique used for multiple neurological conditions. Over the past two decades, it has been widely used to predict cognitive decline; identify pathophysiological markers; promote neuroplasticity; and assess brain excitability, plasticity, and connectivity. It has also been applied to patients with dementia, because it can yield facilitatory effects on cognition and promote brain recovery after a neurological insult. However, its therapeutic effectiveness at the molecular and synaptic levels has not been elucidated because of a limited number of studies. This study aimed to characterize the neurobiological changes following repetitive transcranial magnetic stimulation treatment, evaluate its effects on synaptic plasticity, and identify the associated mechanisms. This review essentially focuses on changes in the pathology, amyloidogenesis, and clearance pathways, given that amyloid deposition is a major hypothesis in the pathogenesis of Alzheimer's disease. Apoptotic mechanisms associated with repetitive transcranial magnetic stimulation procedures and different pathways mediating gene transcription, which are closely related to the neural regeneration process, are also highlighted. Finally, we discuss the outcomes of animal studies in which neuroplasticity is modulated and assessed at the structural and functional levels by using repetitive transcranial magnetic stimulation, with the aim to highlight future directions for better clinical translations.

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

A Biocompatible Hydrogen-Bonded Organic Framework (HOF) as Sonosensitizer and Artificial Enzyme for In-Depth Treatment of Alzheimer's Disease

Current phototherapeutic approaches for Alzheimer's disease (AD) exhibit restricted clinical outcomes due to the limited physical penetration and comprised brain microenvironment of noninvasive nanomedicine. Herein, a hydrogen-bonded organic framework (HOF) based sonosensitizer is designed and synthesized. Mn-TCPP, a planar molecule where Mn2+ ion is chelated in the core with a large p-conjugated system and 4 carboxylate acid groups, has been successfully used as building blocks to construct an ultrasound-sensitive HOF (USI-MHOF), which can go deep in the brain of AD animal models. The both in vitro and in vivo studies indicate that USI-MHOF can generate singlet oxygen (1O2) and oxidize β-amyloid (Aβ) to inhibit aggregation, consequently attenuating Aβ neurotoxicity. More intriguingly, USI-MHOF exhibits catalase (CAT)- and superoxide dismutase (SOD)-like activities, mitigating neuron oxidative stress and reprograming the brain microenvironment. For better crossing the blood-brain barrier (BBB), the peptide KLVFFAED (KD8) has been covalently grafted to USI-MHOF for improving BBB permeability and Aβ selectivity. Further, in vivo experiments demonstrate a significant reduction of the craniocerebral Aβ plaques and improvement of the cognition deficits in triple-transgenic AD (3×Tg-AD) mice models following deep-penetration ultrasound treatment. The work provides the first example of an ultrasound-responsive biocompatible HOF as non-invasive nanomedicine for in-depth treatment of AD.

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.

Current state of clinical ultrasound neuromodulation

Unmatched by other non-invasive brain stimulation techniques, transcranial ultrasound (TUS) offers highly focal stimulation not only on the cortical surface but also in deep brain structures. These unique attributes are invaluable in both basic and clinical research and might open new avenues for treating neurological and psychiatric diseases. Here, we provide a concise overview of the expanding volume of clinical investigations in recent years and upcoming research initiatives concerning focused ultrasound neuromodulation. Currently, clinical TUS research addresses a variety of neuropsychiatric conditions, such as pain, dementia, movement disorders, psychiatric conditions, epilepsy, disorders of consciousness, and developmental disorders. As demonstrated in sham-controlled randomized studies, TUS neuromodulation improved cognitive functions and mood, and alleviated symptoms in schizophrenia and autism. Further, preliminary uncontrolled evidence suggests relieved anxiety, enhanced motor functions in movement disorders, reduced epileptic seizure frequency, improved responsiveness in patients with minimally conscious state, as well as pain reduction after neuromodulatory TUS. While constrained by the relatively modest number of investigations, primarily consisting of uncontrolled feasibility trials with small sample sizes, TUS holds encouraging prospects for treating neuropsychiatric disorders. Larger sham-controlled randomized trials, alongside further basic research into the mechanisms of action and optimal sonication parameters, are inevitably needed to unfold the full potential of TUS neuromodulation.

Efficacy and safety of transcranial pulse stimulation in young adolescents with attention-deficit/hyperactivity disorder: a pilot, randomized, double-blind, sham-controlled trial

Background

This is the first study to evaluate the efficacy and safety of transcranial pulse stimulation (TPS) for the treatment of attention-deficit/hyperactivity disorder (ADHD) among young adolescents in Hong Kong.

Methods

This double-blind, randomized, sham-controlled trial included a TPS group and a sham TPS group, encompassing a total of 30 subjects aged 12-17 years who were diagnosed with ADHD. Baseline measurements SNAP-IV, ADHD RS-IV, CGI and executive functions (Stroop tests, Digit Span) and post-TPS evaluation were collected. Both groups were assessed at baseline, immediately after intervention, and at 1-month and 3-month follow-ups. Repeated-measures ANOVAs were used to analyze data.

Results

The TPS group exhibited a 30% reduction in the mean SNAP-IV score at postintervention that was maintained at 1- and 3-month follow-ups.

Conclusion

TPS is an effective and safe adjunct treatment for the clinical management of ADHD.

Clinical trial registration

ClinicalTrials.Gov, identifier NCT05422274.

Miniaturized therapeutic systems for ultrasound-modulated drug delivery to the central and peripheral nervous system

Ultrasound is a promising technology to address challenges in drug delivery, including limited drug penetration across physiological barriers and ineffective targeting. Here we provide an overview of the significant advances made in recent years in overcoming technical and pharmacological barriers using ultrasound-assisted drug delivery to the central and peripheral nervous system. We commence by exploring the fundamental principles of ultrasound physics and its interaction with tissue. The mechanisms of ultrasonic-enhanced drug delivery are examined, as well as the relevant tissue barriers. We highlight drug transport through such tissue barriers utilizing insonation alone, in combination with ultrasound contrast agents (e.g., microbubbles), and through innovative particulate drug delivery systems. Furthermore, we review advances in systems and devices for providing therapeutic ultrasound, as their practicality and accessibility are crucial for clinical application.

Ultrasound-Sensitive Intelligent Nanosystems: A Promising Strategy for the Treatment of Neurological Diseases

Neurological diseases are a major global health challenge, affecting hundreds of millions of people worldwide. Ultrasound therapy plays an irreplaceable role in the treatment of neurological diseases due to its noninvasive, highly focused, and strong tissue penetration capabilities. However, the complexity of brain and nervous system and the safety risks associated with prolonged exposure to ultrasound therapy severely limit the applicability of ultrasound therapy. Ultrasound-sensitive intelligent nanosystems (USINs) are a novel therapeutic strategy for neurological diseases that bring greater spatiotemporal controllability and improve safety to overcome these challenges. This review provides a detailed overview of therapeutic strategies and clinical advances of ultrasound in neurological diseases, focusing on the potential of USINs-based ultrasound in the treatment of neurological diseases. Based on the physical and chemical effects induced by ultrasound, rational design of USINs is a prerequisite for improving the efficacy of ultrasound therapy. Recent developments of ultrasound-sensitive nanocarriers and nanoagents are systemically reviewed. Finally, the challenges and developing prospects of USINs are discussed in depth, with a view to providing useful insights and guidance for efficient ultrasound treatment of neurological diseases.

A review of functional neuromodulation in humans using low-intensity transcranial focused ultrasound

Transcranial ultrasonic neuromodulation is a rapidly burgeoning field where low-intensity transcranial focused ultrasound (tFUS), with exquisite spatial resolution and deep tissue penetration, is used to non-invasively activate or suppress neural activity in specific brain regions. Over the past decade, there has been a rapid increase of tFUS neuromodulation studies in healthy humans and subjects with central nervous system (CNS) disease conditions, including a recent surge of clinical investigations in patients. This narrative review summarized the findings of human neuromodulation studies using either tFUS or unfocused transcranial ultrasound (TUS) reported from 2013 to 2023. The studies were categorized into two separate sections: healthy human research and clinical studies. A total of 42 healthy human investigations were reviewed as grouped by targeted brain regions, including various cortical, subcortical, and deep brain areas including the thalamus. For clinical research, a total of 22 articles were reviewed for each studied CNS disease condition, including chronic pain, disorder of consciousness, Alzheimer's disease, Parkinson's disease, depression, schizophrenia, anxiety disorders, substance use disorder, drug-resistant epilepsy, and stroke. Detailed information on subjects/cohorts, target brain regions, sonication parameters, outcome readouts, and stimulatory efficacies were tabulated for each study. In later sections, considerations for planning tFUS neuromodulation in humans were also concisely discussed. With an excellent safety profile to date, the rapid growth of human tFUS research underscores the increasing interest and recognition of its significant potential in the field of non-invasive brain stimulation (NIBS), offering theranostic potential for neurological and psychiatric disease conditions and neuroscientific tools for functional brain mapping.

Scanning ultrasound-mediated memory and functional improvements do not require amyloid-β reduction

A prevalent view in treating age-dependent disorders including Alzheimer's disease (AD) is that the underlying amyloid plaque pathology must be targeted for cognitive improvements. In contrast, we report here that repeated scanning ultrasound (SUS) treatment at 1 MHz frequency can ameliorate memory deficits in the APP23 mouse model of AD without reducing amyloid-β (Aβ) burden. Different from previous studies that had shown Aβ clearance as a consequence of blood-brain barrier (BBB) opening, here, the BBB was not opened as no microbubbles were used. Quantitative SWATH proteomics and functional magnetic resonance imaging revealed that ultrasound induced long-lasting functional changes that correlate with the improvement in memory. Intriguingly, the treatment was more effective at a higher frequency (1 MHz) than at a frequency within the range currently explored in clinical trials in AD patients (286 kHz). Together, our data suggest frequency-dependent bio-effects of ultrasound and a dissociation of cognitive improvement and Aβ clearance, with important implications for the design of trials for AD therapies.

Opportunities and obstacles in non-invasive brain stimulation

Non-invasive brain stimulation (NIBS) is a complex and multifaceted approach to modulating brain activity and holds the potential for broad accessibility. This work discusses the mechanisms of the four distinct approaches to modulating brain activity non-invasively: electrical currents, magnetic fields, light, and ultrasound. We examine the dual stochastic and deterministic nature of brain activity and its implications for NIBS, highlighting the challenges posed by inter-individual variability, nebulous dose-response relationships, potential biases and neuroanatomical heterogeneity. Looking forward, we propose five areas of opportunity for future research: closed-loop stimulation, consistent stimulation of the intended target region, reducing bias, multimodal approaches, and strategies to address low sample sizes.

Ultrasound-Responsive Nanodroplet-Based Targeted Therapy via Conversion to Microbubbles

Ultrasound-based therapy is appealing as it can be used via a wireless approach at remote parts of the body including the brain. Microbubbles are commonly used in such therapy due to their highly sound-responsive property. However, the larger size of microbubbles limits selective targeting in vitro/in vivo. Here, we report the design of nanodroplets of 70-130 nm in size that can be easily converted to microbubbles via ultrasound exposure. The advantage of this approach is that smaller nanodroplets can be used for cell/subcellular targeting, and next, they can be used for therapy by converting to microbubbles. More specifically, folate/dopamine-terminated perfluorohexane nanodroplets are designed that are loaded with a molecular drug. These nanodroplets are used for selective cell targeting, followed by ultrasound-induced microbubble conversion that is associated with drug release and intracellular reactive oxygen species generation. This approach has been used for selective cell therapy applications. The designed nanodroplet and approach can be used for the enhanced therapeutic performance of existing drugs.

Nanobubble-actuated ultrasound neuromodulation for selectively shaping behavior in mice

Ultrasound is an acoustic wave which can noninvasively penetrate the skull to deep brain regions, enabling neuromodulation. However, conventional ultrasound's spatial resolution is diffraction-limited and low-precision. Here, we report acoustic nanobubble-mediated ultrasound stimulation capable of localizing ultrasound's effects to only the desired brain region in male mice. By varying the delivery site of nanobubbles, ultrasound could activate specific regions of the mouse motor cortex, evoking EMG signaling and limb movement, and could also, separately, activate one of two nearby deep brain regions to elicit distinct behaviors (freezing or rotation). Sonicated neurons displayed reversible, low-latency calcium responses and increased c-Fos expression in the sub-millimeter-scale region with nanobubbles present. Ultrasound stimulation of the relevant region also modified depression-like behavior in a mouse model. We also provide evidence of a role for mechanosensitive ion channels. Altogether, our treatment scheme allows spatially-targetable, repeatable and temporally-precise activation of deep brain circuits for neuromodulation without needing genetic modification.

Novel ultrasound neuromodulation therapy with transcranial pulse stimulation (TPS) in Parkinson's disease: a first retrospective analysis

BACKGROUND

Transcranial Pulse Stimulation (TPS) has been recently introduced as a novel ultrasound neuromodulation therapy with the potential to stimulate the human brain in a focal and targeted manner. Here, we present a first retrospective analysis of TPS as an add-on therapy for Parkinson's disease (PD), focusing on feasibility, safety, and clinical effects. We also discuss the placebo response in non-invasive brain stimulation studies as an important context.

METHODS

This retrospective clinical data analysis included 20 PD patients who received ten sessions of TPS intervention focused on the individual motor network. Safety evaluations were conducted throughout the intervention period. We analyzed changes in motor symptoms before and after TPS treatment using Unified Parkinson's Disease Rating Scale part III (UPDRS-III).

RESULTS

We found significant improvement in UPDRS-III scores after treatment compared to baseline (pre-TPS: 16.70 ± 8.85, post-TPS: 12.95 ± 8.55; p < 0.001; Cohen's d = 1.38). Adverse events monitoring revealed no major side effects.

CONCLUSION

These preliminary findings suggest that TPS can further improve motor symptoms in PD patients already on optimized standard therapy. Findings have to be evaluated in context with the current literature on placebo effects.

Influence of the skull bone and brain tissue on the sound field in transcranial extracorporeal shock wave therapy: an ex vivo study

OBJECTIVES

Focused ultrasound is mainly known for focal ablation and localized hyperthermia of tissue. During the last decade new treatment options were developed for neurological indications based on blood-brain-barrier opening or neuromodulation. Recently, the transcranial application of shock waves has been a subject of research. However, the mechanisms of action are not yet understood. Hence, it is necessary to know the energy that reaches the brain during the treatment and the focusing characteristics within the tissue.

METHODS

The sound field of a therapeutic extracorporeal shock wave transducer was investigated after passing human skull bone (n=5) or skull bone with brain tissue (n=2) in this ex vivo study. The maximum and minimum pressure distribution and the focal pressure curves were measured at different intensity levels and penetration depths, and compared to measurements in water.

RESULTS

Mean peak negative pressures of up to -4.97 MPa were reached behind the brain tissue. The positive peak pressure was attenuated by between 20.85 and 25.38 dB/cm by the skull bone. Additional damping by the brain tissue corresponded to between 0.29 and 0.83 dB/cm. Compared to the measurements in water, the pulse intensity integral in the focal spot was reduced by 84 % by the skull bone and by additional 2 % due to the brain tissue, resulting in a total damping of up to 86 %. The focal position was shifted up to 8 mm, whereas the basic shape of the pressure curves was preserved.

CONCLUSIONS

Positive effects may be stimulated by transcranial shock wave therapy but damage cannot be excluded.

Nonmedication Devices in Development for the Treatment of Alzheimer's Disease

 Huge investments continue to be made in treatment for Alzheimer's disease (AD), with more than one hundred drugs currently in development. Pharmacological approaches and drug development, particularly those targeting amyloid-β, have dominated the therapeutic landscape. At the same time, there is also a growing interest in devices for treating AD. This review aimed to identify and describe devices under development for AD treatment. In this review, we queried the devices that are in development for the treatment of AD. PubMed was searched through the end of 2021 using the terms "device," "therapeutics," and "Alzheimer's" for articles that report on devices to treat AD. Ten devices with 31 references were identified as actively being developed for the treatment of AD. Many of these devices are far along in development. Device-based therapies are often overlooked when evaluating treatment approaches to AD. However, many devices for treating AD are in development and some show promising results.

Bioinformatics to analyze the differentially expressed genes in different degrees of Alzheimer's disease and their roles in progress of the disease

Employing bioinformatics approaches, this investigation pinpointed pivotal differentially expressed genes (DEGs) across the spectrum of Alzheimer's disease (AD), from incipient to severe stages, using the GSE28146 dataset from the GEO repository. Analytical methods included DEG identification via the limma package in R, coupled with GO and KEGG pathway analyses through clusterProfiler, to discern biological processes and pathway involvements. Key findings spotlighted the roles of proteasome subunits PSMB4, PSMB8, PSMC4, and PSMD6 in the early stage, ribosomal proteins RPS3 and RPL11 during moderate AD, and mitochondrial components COX5B, COX6B2, and COX7A2 in severe AD, underscoring their importance in the disease's pathogenesis. Conclusively, these results not only delineate the dynamic genetic shifts accompanying AD progression but also propose critical biomarkers for potential therapeutic targeting, offering a consolidated basis for future AD research and treatment development. This offered a novel idea for analyzing the pathogenesis and development of AD and investigation of targeted drugs.

Transcranial pulse stimulation in Alzheimer's disease

BACKGROUND

Transcranial pulse stimulation (TPS) is a novel noninvasive ultrasonic brain stimulation that can increase cortical and corticospinal excitability, induce neuroplasticity, and increase functional connectivity within the brain. Several trials have confirmed its potential in treating Alzheimer's disease (AD).

OBJECTIVE

To investigate the effect and safety of TPS on AD.

DESIGN

A systematic review.

METHODS

PubMed, Embase via Ovid, Web of Science, Cochrane Library, CNKI (China National Knowledge Infrastructure), VIP (China Science and Technology Journal Database), and WanFang were searched from inception to April 1, 2023. Study selection, data extraction, and quality evaluation of the studies were conducted by two reviewers independently, with any controversy resolved by consensus. The Methodological Index for Nonrandomized Studies was used to assess the risk of bias.

RESULTS

Five studies were included in this review, with a total of 99 patients with AD. For cognitive performance, TPS significantly improved the scores of the CERAD (Consortium to Establish a Registry for Alzheimer's Disease) test battery, Alzheimer's Disease Assessment Scale (cognitive), Montreal Cognitive Assessment, and Mini-Mental Status Examination. For depressive symptoms, TPS significantly reduced the scores of the Alzheimer's Disease Assessment Scale (affective), Geriatric Depression Score, and Beck Depression Inventory. By functional magnetic resonance imaging, studies have shown that TPS improved cognitive performance in AD patients by increasing functional connectivity in the hippocampus, parahippocampal cortex, precuneus, and parietal cortex, and activating cortical activity in the bilateral hippocampus. TPS alleviated depressive symptoms in AD patients by decreasing functional connectivity between the ventromedial network (left frontal orbital cortex) and the salience network (right anterior insula). Adverse events in this review, including headache, worsening mood, jaw pain, nausea, and drowsiness, were reversible and lasted no longer than 1 day. No serious adverse events or complications were observed.

CONCLUSIONS

TPS is promising in improving cognitive performance and reducing depressive symptoms in patients with AD. TPS may be a safe adjunct therapy in the treatment of AD. However, these findings lacked a sham control and were limited by the small sample size of the included studies. Further research may be needed to better explore the potential of TPS.

PATIENT AND PUBLIC INVOLVEMENT

Patients and the public were not involved in this study.

Shedding light on ultrasound in action: Optical and optoacoustic monitoring of ultrasound brain interventions

Monitoring brain responses to ultrasonic interventions is becoming an important pillar of a growing number of applications employing acoustic waves to actuate and cure the brain. Optical interrogation of living tissues provides a unique means for retrieving functional and molecular information related to brain activity and disease-specific biomarkers. The hybrid optoacoustic imaging methods have further enabled deep-tissue imaging with optical contrast at high spatial and temporal resolution. The marriage between light and sound thus brings together the highly complementary advantages of both modalities toward high precision interrogation, stimulation, and therapy of the brain with strong impact in the fields of ultrasound neuromodulation, gene and drug delivery, or noninvasive treatments of neurological and neurodegenerative disorders. In this review, we elaborate on current advances in optical and optoacoustic monitoring of ultrasound interventions. We describe the main principles and mechanisms underlying each method before diving into the corresponding biomedical applications. We identify areas of improvement as well as promising approaches with clinical translation potential.

Artificial sharp-wave-ripples to support memory and counter neurodegeneration

Information processed in our sensory neocortical areas is transported to the hippocampus during memory encoding, and between hippocampus and neocortex during memory consolidation, and retrieval. Short bursts of high-frequency oscillations, so called sharp-wave-ripples, have been proposed as a potential mechanism for this information transfer: They can synchronize neural activity to support the formation of local neural networks to store information, and between distant cortical sites to act as a bridge to transfer information between sensory cortical areas and hippocampus. In neurodegenerative diseases like Alzheimer's Disease, different neuropathological processes impair normal neural functioning and neural synchronization as well as sharp-wave-ripples, which impairs consolidation and retrieval of information, and compromises memory. Here, we formulate a new hypothesis, that artificially inducing sharp-wave-ripples with noninvasive high-frequency visual stimulation could potentially support memory functioning, as well as target the neuropathological processes underlying neurodegenerative diseases. We also outline key challenges for empirical tests of the hypothesis.

Bidirectional Neuronal Control of Epileptiform Activity by Repetitive Transcranial Focused Ultrasound Stimulations

Repetitive stimulation procedures are used in neuromodulation techniques to induce persistent excitatory or inhibitory brain activity. The directivity of modulation is empirically regulated by modifying the stimulation length, interval, and strength. However, bidirectional neuronal modulations using ultrasound stimulations are rarely reported. This study presents bidirectional control of epileptiform activities with repetitive transcranial-focused ultrasound stimulations in a rat model of drug-induced acute epilepsy. It is found that repeated transmission of elongated (40 s), ultra-low pressure (0.25 MPa) ultrasound can fully suppress epileptic activities in electro-encephalography and cerebral blood volume measurements, while the change in bursting intervals from 40 to 20 s worsens epileptic activities even with the same burst length. Furthermore, the suppression induced by 40 s long bursts is transformed to excitatory states by a subsequent transmission. Bidirectional modulation of epileptic seizures with repeated ultrasound stimulation is achieved by regulating the changes in glutamate and γ-Aminobutyric acid levels, as confirmed by measurements of expressed c-Fos and GAD65 and multitemporal analysis of neurotransmitters in the interstitial fluid obtained via microdialysis.

Perspective for Molecular Dynamics Simulation Studies of Amyloid-β Aggregates

The cause of Alzheimer's disease is related to aggregates such as oligomers and amyloid fibrils consisting of amyloid-β (Aβ) peptides. Molecular dynamics (MD) simulation studies have been conducted to understand the molecular mechanism of the formation and disruption of Aβ aggregates. In this Perspective, the MD simulation studies are classified into four categories, focusing on the target systems: aggregation of Aβ peptides in bulk solution, Aβ aggregation at the interface, aggregation inhibitor against Aβ peptides, and nonequilibrium MD simulation of Aβ aggregates. MD simulation studies in these categories are first reviewed. Future perspectives in each category are then presented. Finally, the overall perspective is presented on how MD simulations of Aβ aggregates can be utilized for developing Alzheimer's disease treatment.

Enhanced and spatially controllable neuronal activity induced by transcranial focused ultrasound stimulation combined with phase-change nanodroplets

Non-invasive ultrasound neuromodulation (USNM) is a powerful tool to explore neural circuits and treat neurological disorders. Due to the heterogeneity of the skull and regional variations in modulation and treatment objectives, it is necessary to develop an efficient and spatially controllable neuromodulation approach. Recently, transcranial focused ultrasound (tFUS) combined with external biomicro/nanomaterials for brain stimulation has garnered significant attention. This study focused on tFUS combined with perfluoropentane (PFP) nanodroplets (NDs) to improve the efficacy and spatial controllability of USNM. The developed two-stage variable pulse tFUS sequence that include the acoustic droplet vaporization (ADV) pulse for vaporizing PFP NDs into microbubbles (MBs) and the USNM sequence for inducing mechanical oscillations of the formed MBs to enhance neuronal activity. Further, adjusting the acoustic pressure of the ADV pulse generated the controllable vaporization regions, thereby achieving spatially controllable neuromodulation. The results showed that the mean densities of c-fos+ cells expression in the group of PFP NDs with ADV (109 ± 19 cells/mm2) were significantly higher compared to the group without ADV (37.34 ± 8.24 cells/mm2). The acoustic pressure of the ADV pulse with 1.98 MPa and 2.81 MPa in vitro generated the vaporization regions of 0.146 ± 0.032 cm2 and 0.349 ± 0.056 cm2, respectively. Under the same stimulation conditions, a larger vaporization region was also obtained with higher acoustic pressure in vivo, inducing a broader region of neuronal activation. Therefore, this study will serve as a valuable reference for developing the efficient and spatially controllable tFUS neuromodulation strategy.

Excitatory-inhibitory modulation of transcranial focus ultrasound stimulation on human motor cortex

AIMS

Transcranial focus ultrasound stimulation (tFUS) is a promising non-invasive neuromodulation technology. This study aimed to evaluate the modulatory effects of tFUS on human motor cortex (M1) excitability and explore the mechanism of neurotransmitter-related intracortical circuitry and plasticity.

METHODS

Single pulse transcranial magnetic stimulation (TMS)-eliciting motor-evoked potentials (MEPs) were used to assessed M1 excitability in 10 subjects. Paired-pulse TMS was used to measure the effects of tFUS on GABA- and glutamate-related intracortical excitability and 1 H-MRS was used to assess the effects of repetitive tFUS on GABA and Glx (glutamine + glutamate) neurometabolic concentrations in the targeting region in nine subjects.

RESULTS

The etFUS significantly increased M1 excitability, decreased short interval intracortical inhibition (SICI) and long interval intracortical inhibition (LICI). The itFUS significantly suppressed M1 excitability, increased SICI, LICI, and decreased intracortical facilitation (ICF). Seven times of etFUS decreased the GABA concentration (6.32%), increased the Glx concentration (12.40%), and decreased the GABA/Glx ratio measured by MRS, while itFUS increased the GABA concentration (18.59%), decreased Glx concentration (0.35%), and significantly increased GABA/Glx ratio.

CONCLUSION

The findings support that tFUS with different parameters can exert excitatory and inhibitory neuromodulatory effects on the human motor cortex. We provide novel insights that tFUS change cortical excitability and plasticity by regulating excitatory-inhibition balance related to the GABAergic and glutamatergic receptor function and neurotransmitter metabolic level.

A transducer positioning method for transcranial focused ultrasound treatment of brain tumors

Purpose

As a non-invasive method for brain diseases, transcranial focused ultrasound (tFUS) offers higher spatial precision and regulation depth. Due to the altered path and intensity of sonication penetrating the skull, the focus and intensity in the skull are difficult to determine, making the use of ultrasound therapy for cancer treatment experimental and not widely available. The deficiency can be effectively addressed by numerical simulation methods, which enable the optimization of sonication modulation parameters and the determination of precise transducer positioning.

Methods

A 3D skull model was established using binarized brain CT images. The selection of the transducer matrix was performed using the radius positioning (RP) method after identifying the intracranial target region. Simulations were performed, encompassing acoustic pressure (AP), acoustic field, and temperature field, in order to provide compelling evidence of the safety of tFUS in sonication-induced thermal effects.

Results

It was found that the angle of sonication path to the coronal plane obtained at all precision and frequency models did not exceed 10° and 15° to the transverse plane. The results of thermal effects illustrated that the peak temperatures of tFUS were 43.73°C, which did not reach the point of tissue degeneration. Once positioned, tFUS effectively delivers a Full Width at Half Maximum (FWHM) stimulation that targets tumors with diameters of up to 3.72 mm in a one-off. The original precision model showed an attenuation of 24.47 ± 6.13 mm in length and 2.40 ± 1.42 mm in width for the FWHM of sonication after penetrating the skull.

Conclusion

The vector angles of the sonication path in each direction were determined based on the transducer positioning results. It has been suggested that when time is limited for precise transducer positioning, fixing the transducer on the horizontal surface of the target region can also yield positive results for stimulation. This framework used a new transducer localization method to offer a reliable basis for further research and offered new methods for the use of tFUS in brain tumor-related research.

Transcranial pulse stimulation in the treatment of mild neurocognitive disorders

OBJECTIVE

There are limited effectiveness and potential side effects of existing pharmacological approach in treating mild neurocognitive disorder (NCD). Transcranial pulse stimulation (TPS) applies repetitive single high-pressure ultrashort shockwave pulses to stimulate the brain, which has been shown to effectively improve cognition in major NCD. However, the effectiveness of TPS in mild NCD patients remained unknown. This study aims to assess the effectiveness and tolerability of TPS with neuro-navigation in old-age adults with mild NCD by both clinical and biochemical assessments.

METHODS

An open-label study recruited older adults with mild NCD to receive neuro-navigated TPS intervention for two weeks with three sessions per week. Assessments included detailed cognitive assessments, APOE genotype, and brain-derived neurotrophic factor (BDNF).

RESULTS

Nineteen participants (12 females and 7 males) completed the whole TPS interventions with no serious adverse effects reported. Repeated measures ANOVA showed statistically significant effects of time on HK-MoCA (F (3, 54) = 4.99, P = 0.004), 30-sec interval of Verbal Fluency Test (F (3, 54) = 2.94, P = 0.041), Stroop interference (F (3, 54) = 3.46, P = 0.023), and Chinese IADL (F (3, 54) = 2.78, P = 0.050) after receiving the intervention. Bonferroni post hoc comparisons on HK-MoCA showed a significant improvement after intervention. There was no significant change in serum BDNF level.

INTERPRETATION

TPS has brought significant improvement in cognition of elderly with mild NCD. It has a great potential to delay the deterioration of cognition in older adults. The long-term effect of TPS in cognition would benefit from further large-scale, randomized, sham-controlled trials.

Application of transcranial brain stimulation in dementia

The number of patients with dementia grows rapidly as the global population ages, which posits tremendous health-care burden to the society. Only cholinesterase inhibitors and a N-methyl-D-aspartate receptor antagonist have been approved for treating patients with Alzheimer's disease (AD), and their clinical effects remained limited. Medical devices serve as an alternative therapeutic approach to modulating neural activities and enhancing cognitive function. Four major brain stimulation technologies including deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and transcranial ultrasound stimulation (TUS) have been applied to AD in a clinical trial setting. DBS allows electrical stimulation at the specified nucleus but remains resource-demanding, and after all, an invasive surgery; whereas TMS and tDCS are widely available and affordable but less ideal with respect to localization. The unique physical property of TUS, on the other hand, allows both thermal and mechanical energy to be transduced and focused for neuromodulation. In the context of dementia, using focused ultrasound to induce blood-brain barrier opening for delivering drugs and metabolizing amyloid protein has drawn great attention in recent years. Furthermore, low-intensity pulsed ultrasound has demonstrated its neuroprotective effects in both in vitro and in vivo studies, leading to ongoing clinical trials for AD. The potential and limitation of transcranial brain stimulation for treating patients with dementia would be discussed in this review.

The Emergence of Functional Ultrasound for Noninvasive Brain-Computer Interface

A noninvasive brain-computer interface is a central task in the comprehensive analysis and understanding of the brain and is an important challenge in international brain-science research. Current implanted brain-computer interfaces are cranial and invasive, which considerably limits their applications. The development of new noninvasive reading and writing technologies will advance substantial innovations and breakthroughs in the field of brain-computer interfaces. Here, we review the theory and development of the ultrasound brain functional imaging and its applications. Furthermore, we introduce latest advancements in ultrasound brain modulation and its applications in rodents, primates, and human; its mechanism and closed-loop ultrasound neuromodulation based on electroencephalograph are also presented. Finally, high-frequency acoustic noninvasive brain-computer interface is prospected based on ultrasound super-resolution imaging and acoustic tweezers.

Ultrasound Neuromodulation as a New Brain Therapy

Within the last decade, ultrasound has been "rediscovered" as a technique for brain therapies. Modern technologies allow focusing ultrasound through the human skull for highly focal tissue ablation, clinical neuromodulatory brain stimulation, and targeted focal blood-brain-barrier opening. This article gives an overview on the state-of-the-art of the most recent application: ultrasound neuromodulation as a new brain therapy. Although research centers have existed for decades, the first treatment centers were not established until 2020, and clinical applications are spreading rapidly.

Advanced Temporally-Spatially Precise Technologies for On-Demand Neurological Disorder Intervention

Temporal-spatial precision has attracted increasing attention for the clinical intervention of neurological disorders (NDs) to mitigate adverse effects of traditional treatments and achieve point-of-care medicine. Inspiring steps forward in this field have been witnessed in recent years, giving the credit to multi-discipline efforts from neurobiology, bioengineering, chemical materials, artificial intelligence, and so on, exhibiting valuable clinical translation potential. In this review, the latest progress in advanced temporally-spatially precise clinical intervention is highlighted, including localized parenchyma drug delivery, precise neuromodulation, as well as biological signal detection to trigger closed-loop control. Their clinical potential in both central and peripheral nervous systems is illustrated meticulously related to typical diseases. The challenges relative to biosafety and scaled production as well as their future perspectives are also discussed in detail. Notably, these intelligent temporally-spatially precision intervention systems could lead the frontier in the near future, demonstrating significant clinical value to support billions of patients plagued with NDs.

Low-Intensity Focused Ultrasound Neuromodulation for Stroke Recovery: A Novel Deep Brain Stimulation Approach for Neurorehabilitation?

Stroke as the leading cause of adult long-term disability and has a significant impact on patients, society and socio-economics. Non-invasive brain stimulation (NIBS) approaches such as transcranial magnetic stimulation (TMS) or transcranial electrical stimulation (tES) are considered as potential therapeutic options to enhance functional reorganization and augment the effects of neurorehabilitation. However, non-invasive electrical and magnetic stimulation paradigms are limited by their depth focality trade-off function that does not allow to target deep key brain structures critically important for recovery processes. Transcranial ultrasound stimulation (TUS) is an emerging approach for non-invasive deep brain neuromodulation. Using non-ionizing, ultrasonic waves with millimeter-accuracy spatial resolution, excellent steering capacity and long penetration depth, TUS has the potential to serve as a novel non-invasive deep brain stimulation method to establish unprecedented neuromodulation and novel neurorehabilitation protocols. The purpose of the present review is to provide an overview on the current knowledge about the neuromodulatory effects of TUS while discussing the potential of TUS in the field of stroke recovery, with respect to existing NIBS methods. We will address and discuss critically crucial open questions and remaining challenges that need to be addressed before establishing TUS as a new clinical neurorehabilitation approach for motor stroke recovery.

Evaluating the efficacy and safety of transcranial pulse stimulation on adolescents with attention deficit hyperactivity disorder: Study protocol of a pilot randomized, double-blind, sham-controlled trial

Background

Traditional treatment alone might not effectively control the severity of attention deficit hyperactivity disorder (ADHD) symptoms. Transcranial pulse stimulation (TPS) is a non-invasive brain stimulation (NIBS) technology used on older adults with mild neurocognitive disorders and adults with major depressive disorder. However, there has been no study conducted on young adolescents with ADHD. This will be the first nationwide study evaluating the efficacy and safety of TPS in the treatment of ADHD among young adolescents in Hong Kong.

Methods

This study proposes a double-blinded, randomized, sham-controlled trial including TPS as an intervention group and a sham TPS group. Both groups will be measured at baseline (T1), immediately after the intervention (T2), and at the 1-month (T3) and 3-month follow-ups (T4).

Recruitment

A total of 30 subjects aged between 12 and 17 years, diagnosed with attention deficit hyperactivity disorder (ADHD), will be recruited in this study. All subjects will be computer randomized into either the intervention group or the sham TPS group on a 1:1 ratio.

Intervention

All subjects in each group will have to undertake functional MRI (fMRI) before and after six 30-min TPS sessions, which will be completed in 2 weeks' time.

Outcomes

Baseline measurements and post-TPS evaluation of the ADHD symptoms and executive functions will also be conducted on all participants. The 1- and 3-month follow-up periods will be used to assess the long-term sustainability of the TPS intervention. For statistical analysis, ANOVA with repeated measures will be used to analyze data. Missing data were managed by multiple imputations. The level of significance will be set to p &lt; 0.05.

Significance of the study

Results emerging from this study will generate new knowledge to ascertain whether TPS can be used as a top-on treatment for ADHD.

Clinical trial registration

clinicaltrails.gov, identifier: NCT05422274.

CERAD (Consortium to Establish a Registry for Alzheimer's Disease) Neuropsychology Assessment Battery: 35 Years and Counting

BACKGROUND

In 1986, the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) was mandated to develop a brief neuropsychological assessment battery (CERAD-NAB) for AD, for uniform neuropsychological assessment, and information aggregation. Initially used across the National Institutes of Aging-funded Alzheimer's Disease Research Centers, it has become widely adopted wherever information is desired on cognitive status and change therein, particularly in older populations.

OBJECTIVE

Our purpose is to provide information on the multiple uses of the CERAD-NAB since its inception, and possible further developments.

METHODS

Since searching on "CERAD neuropsychological assessment battery" or similar terms missed important information, "CERAD" alone was entered into PubMed and SCOPUS, and CERAD-NAB use identified from the resulting studies. Use was sorted into major categories, e.g., psychometric information, norms, dementia/differential dementia diagnosis, epidemiology, intervention evaluation, genetics, etc., also translations, country of use, and alternative data gathering approaches.

RESULTS

CERAD-NAB is available in ∼20 languages. In addition to its initial purpose assessing AD severity, CERAD-NAB can identify mild cognitive impairment, facilitate differential dementia diagnosis, determine cognitive effects of naturally occurring and experimental interventions (e.g., air pollution, selenium in soil, exercise), has helped to clarify cognition/brain physiology-neuroanatomy, and assess cognitive status in dementia-risk conditions. Surveys of primary and tertiary care patients, and of population-based samples in multiple countries have provided information on prevalent and incident dementia, and cross-sectional and longitudinal norms for ages 35-100 years.

CONCLUSION

CERAD-NAB has fulfilled its original mandate, while its uses have expanded, keeping up with advances in the area of dementia.

Ultrasound as a versatile tool for short- and long-term improvement and monitoring of brain function

Treating the brain with focused ultrasound (FUS) at low intensities elicits diverse responses in neurons, astroglia, and the extracellular matrix. In combination with intravenously injected microbubbles, FUS also opens the blood-brain barrier (BBB) and facilitates focal drug delivery. However, an incompletely understood cellular specificity and a wide parameter space currently limit the optimal application of FUS in preclinical and human studies. In this perspective, we discuss how different FUS modalities can be utilized to achieve short- and long-term improvements, thereby potentially treating brain disorders. We review the ongoing efforts to determine which parameters induce neuronal inhibition versus activation and how mechanoreceptors and signaling cascades are activated to induce long-term changes, including memory improvements. We suggest that optimal FUS treatments may require different FUS modalities and devices, depending on the targeted brain area or local pathology, and will be greatly enhanced by new techniques for monitoring FUS efficacy.

A Residual Marker of Cognitive Reserve Is Associated with Resting-State Intrinsic Functional Connectivity Along the Alzheimer's Disease Continuum

BACKGROUND

Cognitive reserve (CR) explains inter-individual differences in the impact of the neurodegenerative burden on cognitive functioning. A residual model was proposed to estimate CR more accurately than previous measures. However, associations between residual CR markers (CRM) and functional connectivity (FC) remain unexplored.

OBJECTIVE

To explore the associations between the CRM and intrinsic network connectivity (INC) in resting-state networks along the neuropathological-continuum of Alzheimer's disease (ADN).

METHODS

Three hundred eighteen participants from the DELCODE cohort were stratified using cerebrospinal fluid biomarkers according to the A(myloid-β)/T(au)/N(eurodegeneration) classification. CRM was calculated utilizing residuals obtained from a multilinear regression model predicting cognition from markers of disease burden. Using an independent component analysis in resting-state fMRI data, we measured INC of resting-state networks, i.e., default mode network (DMN), frontoparietal network (FPN), salience network (SAL), and dorsal attention network. The associations of INC with a composite memory score and CRM and the associations of CRM with the seed-to-voxel functional connectivity of memory-related were tested in general linear models.

RESULTS

CRM was positively associated with INC in the DMN in the entire cohort. The A+T+N+ group revealed an anti-correlation between the SAL and the DMN. Furthermore, CRM was positively associated with anti-correlation between memory-related regions in FPN and DMN in ADN and A+T/N+.

CONCLUSION

Our results provide evidence that INC is associated with CRM in ADN defined as participants with amyloid pathology with or without cognitive symptoms, suggesting that the neural correlates of CR are mirrored in network FC in resting-state.

Effects of Transcranial Pulse Stimulation (TPS) on Adults with Symptoms of Depression-A Pilot Randomized Controlled Trial

Transcranial pulse stimulation (TPS) is a recent development in non-invasive brain stimulations (NIBS) that has been proven to be effective in terms of significantly improving Alzheimer patients' cognition, memory, and execution functions. Nonetheless, there is, currently, no trial evaluating the efficacy of TPS on adults with major depression disorder (MDD) nationwide. In this single-blinded, randomized controlled trial, a 2-week TPS treatment comprising six 30 min TPS sessions were administered to participants. Participants were randomized into either the TPS group or the Waitlist Control (WC) group, stratified by gender and age according to a 1:1 ratio. Our primary outcome was evaluated by the Hamilton depression rating scale-17 (HDRS-17). We recruited 30 participants that were aged between 18 and 54 years, predominantly female (73%), and ethnic Chinese from 1 August to 31 October 2021. Moreover, there was a significant group x time interaction (F(1, 28) = 18.8, p < 0.001). Further, when compared with the WC group, there was a significant reduction in the depressive symptom severity in the TPS group (mean difference = -6.60, p = 0.02, and Cohen's d = -0.93). The results showed a significant intervention effect; in addition, the effect was large and sustainable at the 3-month follow-up. In this trial, it was found that TPS is effective in reducing depressive symptoms among adults with MDD.

Modulation effect of non-invasive transcranial ultrasound stimulation in an ADHD rat model

Objective.Previous studies have demonstrated that transcranial ultrasound stimulation (TUS) with noninvasive high penetration and high spatial resolution has an effective neuromodulatory effect on neurological diseases. Attention deficit hyperactivity disorder (ADHD) is a persistent neurodevelopmental disorder that severely affects child health. However, the neuromodulatory effects of TUS on ADHD have not been reported to date. This study aimed to investigate the neuromodulatory effects of TUS on ADHD.Approach.TUS was performed in ADHD model rats for two consecutive weeks, and the behavioral improvement of ADHD, neural activity of ADHD from neurons and neural oscillation levels, and the plasma membrane dopamine transporter and brain-derived neurotrophic factor (BDNF) in the brains of ADHD rats were evaluated.Main results.TUS can improve cognitive behavior in ADHD rats, and TUS altered neuronal firing patterns and modulated the relative power and sample entropy of local field potentials in the ADHD rats. In addition, TUS can also enhance BDNF expression in the brain tissues.Significance. TUS has an effective neuromodulatory effect on ADHD and thus has the potential to clinically improve cognitive dysfunction in ADHD.

Preventing incubation of drug craving to treat drug relapse: from bench to bedside

In 1986, Gawin and Kleber reported a progressive increase in cue-induced drug craving in individuals with cocaine use disorders during prolonged abstinence. After years of controversy, as of 2001, this phenomenon was confirmed in rodent studies using self-administration model, and defined as the incubation of drug craving. The intensification of cue-induced drug craving after withdrawal exposes abstinent individuals to a high risk of relapse, which urged us to develop effective interventions to prevent incubated craving. Substantial achievements have been made in deciphering the neural mechanisms, with potential implications for reducing drug craving and preventing the relapse. The present review discusses promising drug targets that have been well investigated in animal studies, including some neurotransmitters, neuropeptides, neurotrophic factors, and epigenetic markers. We also discuss translational exploitation and challenges in the field of the incubation of drug craving, providing insights into future investigations and highlighting the potential of pharmacological interventions, environment-based interventions, and neuromodulation techniques.

Numerical and experimental evaluation of low-intensity transcranial focused ultrasound wave propagation using human skulls for brain neuromodulation

BACKGROUND

Low-intensity transcranial focused ultrasound (tFUS) has gained considerable attention as a promising noninvasive neuromodulatory technique for human brains. However, the complex morphology of the skull hinders scholars from precisely predicting the acoustic energy transmitted and the region of the brain impacted during the sonication. This is due to the fact that different ultrasound frequencies and skull morphology variations greatly affect wave propagation through the skull.

PURPOSE

Although the acoustic properties of human skull have been studied for tFUS applications, such as tumor ablation using a multielement phased array, there is no consensus about how to choose a single-element focused ultrasound (FUS) transducer with a suitable frequency for neuromodulation. There are interests in exploring the magnitude and dimension of tFUS beam through human parietal bone for modulating specific brain lobes. Herein, we aim to investigate the wave propagation of tFUS on human skulls to understand and address the concerns above.

METHODS

Both experimental measurements and numerical modeling were conducted to investigate the transmission efficiency and beam pattern of tFUS on five human skulls (C3 and C4 regions) using single-element FUS transducers with six different frequencies (150-1500 kHz). The degassed skull was placed in a water tank, and a calibrated hydrophone was utilized to measure acoustic pressure past it. The cranial computed tomography scan data of each skull were obtained to derive a high-resolution acoustic model (grid point spacing: 0.25 mm) in simulations. Meanwhile, we modified the power-law exponent of acoustic attenuation coefficient to validate numerical modeling and enabled it to be served as a prediction tool, based on the experimental measurements.

RESULTS

The transmission efficiency and -6 dB beamwidth were evaluated and compared for various frequencies. An exponential decrease in transmission efficiency and a logarithmic decrease of -6 dB beamwidth with an increase in ultrasound frequency were observed. It is found that a >750 kHz ultrasound leads to a relatively lower tFUS transmission efficiency (<5%), whereas a <350 kHz ultrasound contributes to a relatively broader beamwidth (>5 mm). Based on these observations, we further analyzed the dependence of tFUS wave propagation on FUS transducer aperture size.

CONCLUSIONS

We successfully studied tFUS wave propagation through human skulls at different frequencies experimentally and numerically. The findings have important implications to predict tFUS wave propagation for ultrasound neuromodulation in clinical applications, and guide researchers to develop advanced ultrasound transducers as neural interfaces.

Toward Prevention and Reduction of Alzheimer's Disease

Different investigations lead to the urgent need to generate validated clinical protocols as a tool for medical doctors to orientate patients under risk for a preventive approach to control Alzheimer's disease. Moreover, there is consensus that the combined effects of risk factors for the disease can be modified according to lifestyle, thus controlling at least 40% of cases. The other fraction of cases are derived from candidate genes and epigenetic components as a relevant factor in AD pathogenesis. At this point, it appears to be of critical relevance the search for molecular biomarkers that may provide information on probable pathological events and alert about early detectable risks to prevent symptomatic events of the disease. These precocious detection markers will then allow early interventions of non-symptomatic subjects at risk. Here, we summarize the status and potential avenues of prevention and highlight the usefulness of biological and reliable markers for AD.

Transcranial low-intensity ultrasound stimulation for treating central nervous system disorders: A promising therapeutic application

Transcranial ultrasound stimulation is a neurostimulation technique that has gradually attracted the attention of researchers, especially as a potential therapy for neurological disorders, because of its high spatial resolution, its good penetration depth, and its non-invasiveness. Ultrasound can be categorized as high-intensity and low-intensity based on the intensity of its acoustic wave. High-intensity ultrasound can be used for thermal ablation by taking advantage of its high-energy characteristics. Low-intensity ultrasound, which produces low energy, can be used as a means to regulate the nervous system. The present review describes the current status of research on low-intensity transcranial ultrasound stimulation (LITUS) in the treatment of neurological disorders, such as epilepsy, essential tremor, depression, Parkinson's disease (PD), and Alzheimer's disease (AD). This review summarizes preclinical and clinical studies using LITUS to treat the aforementioned neurological disorders and discusses their underlying mechanisms.

General-Purpose Ultrasound Neuromodulation System for Chronic, Closed-Loop Preclinical Studies in Freely Behaving Rodents

Transcranial focused ultrasound stimulation (tFUS) is an effective noninvasive treatment modality for brain disorders with high clinical potential. However, the therapeutic effects of ultrasound neuromodulation are not widely explored due to limitations in preclinical systems. The current preclinical studies are head-fixed, anesthesia-dependent, and acute, limiting clinical translatability. Here, this work reports a general-purpose ultrasound neuromodulation system for chronic, closed-loop preclinical studies in freely behaving rodents. This work uses microelectromechanical systems (MEMS) technology to design and fabricate a small and lightweight transducer capable of artifact-free stimulation and simultaneous neural recording. Using the general-purpose system, it can be observed that state-dependent ultrasound neuromodulation of the prefrontal cortex increases rapid eye movement (REM) sleep and protects spatial working memory to REM sleep deprivation. The system will allow explorative studies in brain disease therapeutics and neuromodulation using ultrasound stimulation for widespread clinical adoption.

Evaluating the Safety and Efficacy of Transcranial Pulse Stimulation on Autism Spectrum Disorder: A Double-Blinded, Randomized, Sham-Controlled Trial Protocol

Autistic spectrum disorder (ASD) is a common developmental disorder in children. The latest non-intrusive brain stimulation (NIBS) technology-transcranial pulse stimulation (TPS)-has been proven effective in older adults with mild neurocognitive disorders and adults with major depressive disorder. Nonetheless, there is so far no robust randomized controlled trial (RCT) conducted on adolescents with ASD nationwide. This study proposes a two-armed (verum TPS group vs. sham TPS group), double-blinded, randomized, sham-controlled trial. Both groups will be measured at four timepoints, namely, baseline (T1), 2 weeks immediately after post-TPS intervention (T2), and at the 1-month (T3) and 3-month (T4) follow-ups. Thirty-four subjects, aged between 12 and 17, diagnosed with ASD will be recruited in this study. All subjects will be computerized randomised into the verum TPS group or the sham TPS group on a 1:1 ratio. All subjects will undertake functional MRI (fMRI) before and after the 2-weeks TPS interventions, which will be completed in 2 weeks' time. This will be the first RCT evaluating the efficacy of TPS adolescents with ASD in Hong Kong. Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT05408793.

Non-drug Therapies for Alzheimer's Disease: A Review

Alzheimer's disease (AD) is a debilitating disease leading to great social and economic burdens worldwide. During the past decades, increasing understanding of this disease enables dynamic trials for disease interventions. Unfortunately, at present, AD still remains uncurable, and therefore, developing intervention strategies for improving symptoms and slowing down the disease process becomes a practical focus in parallel with searching for a disease-modifying medication. The aim of this review is to summarize the outcomes of AD clinical trials of non-drug therapies published in the past decade, including cognitive-oriented interventions, physical exercise interventions, brain stimulation, as well as nutrition supplementations, to find out the most effective interventions in the category by looking through the primary and secondary outcomes. The outcomes of the trials could be varied with the interventional approaches, the tested cohorts, the settings of observing outcomes, and the duration of follow-ups, which are all discussed in this review. Hence, we hope to provide crucial information for application of these interventions in real-world settings and assist with optimization of clinical trial designs in this area.

High-precision neural stimulation by a highly efficient candle soot fiber optoacoustic emitter

Highly precise neuromodulation with a high efficacy poses great importance in neuroscience. Here we developed a candle soot fiber optoacoustic emitter (CSFOE), capable of generating a high pressure of over 10 MPa with a central frequency of 12.8 MHz, enabling highly efficient neuromodulation in vitro. The design of the fiber optoacoustic emitter, including the choice of the material and the thickness of the layered structure, was optimized in both simulations and experiments. The optoacoustic conversion efficiency of the optimized CSFOE was found to be 10 times higher than the other carbon-based fiber optoacoustic emitters. Driven by a single laser, the CSFOE can perform dual-site optoacoustic activation of neurons, confirmed by calcium (Ca2+) imaging. Our work opens potential avenues for more complex and programmed control in neural circuits using a simple design for multisite neuromodulation in vivo.

Optically-generated focused ultrasound for noninvasive brain stimulation with ultrahigh precision

High precision neuromodulation is a powerful tool to decipher neurocircuits and treat neurological diseases. Current non-invasive neuromodulation methods offer limited precision at the millimeter level. Here, we report optically-generated focused ultrasound (OFUS) for non-invasive brain stimulation with ultrahigh precision. OFUS is generated by a soft optoacoustic pad (SOAP) fabricated through embedding candle soot nanoparticles in a curved polydimethylsiloxane film. SOAP generates a transcranial ultrasound focus at 15 MHz with an ultrahigh lateral resolution of 83 µm, which is two orders of magnitude smaller than that of conventional transcranial-focused ultrasound (tFUS). Here, we show effective OFUS neurostimulation in vitro with a single ultrasound cycle. We demonstrate submillimeter transcranial stimulation of the mouse motor cortex in vivo. An acoustic energy of 0.6 mJ/cm², four orders of magnitude less than that of tFUS, is sufficient for successful OFUS neurostimulation. OFUS offers new capabilities for neuroscience studies and disease treatments by delivering a focus with ultrahigh precision non-invasively.

Harnessing Ultrasound for Targeting Drug Delivery to the Brain and Breaching the Blood–Brain Tumour Barrier

Despite significant advances in developing drugs to treat brain tumours, achieving therapeutic concentrations of the drug at the tumour site remains a major challenge due to the presence of the blood–brain barrier (BBB). Several strategies have evolved to enhance brain delivery of chemotherapeutic agents to treat tumours; however, most approaches have several limitations which hinder their clinical utility. Promising studies indicate that ultrasound can penetrate the skull to target specific brain regions and transiently open the BBB, safely and reversibly, with a high degree of spatial and temporal specificity. In this review, we initially describe the basics of therapeutic ultrasound, then detail ultrasound-based drug delivery strategies to the brain and the mechanisms by which ultrasound can improve brain tumour therapy. We review pre-clinical and clinical findings from ultrasound-mediated BBB opening and drug delivery studies and outline current therapeutic ultrasound devices and technologies designed for this purpose.

Safety of Clinical Ultrasound Neuromodulation

Transcranial ultrasound holds much potential as a safe, non-invasive modality for navigated neuromodulation, with low-intensity focused ultrasound (FUS) and transcranial pulse stimulation (TPS) representing the two main modalities. While neuroscientific and preclinical applications have received much interest, clinical applications are still relatively scarce. For safety considerations, the current literature is largely based on guidelines for ultrasound imaging that uses various physical parameters to describe the ultrasound pulse form and expected bioeffects. However, the safety situation for neuromodulation is inherently different. This article provides an overview of relevant ultrasound parameters with a focus on bioeffects relevant for safe clinical applications. Further, a retrospective analysis of safety data for clinical TPS applications in patients is presented.

Retrospective real-world pilot data on transcranial pulse stimulation in mild to severe Alzheimer's patients

Introduction

Transcranial pulse stimulation (TPS) is a non-invasive neuromodulation therapy that uses short, repetitive shockwaves through a neuro-navigated device. Current research suggests that these pulses lead to a wide range of vascular, metabolic, and neurotrophic changes. This relatively new CE-marked treatment provided first promising results in a clinical pilot study for improving cognition in mild-to-moderate Alzheimer's. Data from other centers is lacking, so here we analyzed safety and pilot real-world short-term results of TPS from the first center in Germany. To gain information about effects in different stages, patients with not only mild but also moderate-to-severe Alzheimer's were analyzed.

Methods

A total of 11 patients were retrospectively examined for cognitive and emotional function before and after the first stimulation series. The effect was assessed using several neuropsychological tests [Alzheimer's Disease Assessment Scale (ADAS), including the ADAS cognitive score (ADAS Cog) and ADAS affective scores, Mini-Mental Status Examination (MMSE), and Montreal Cognitive Assessment (MoCA)] including in comparison between the groups of mild-to-severe patients. Moreover, subjective improvement of symptom severity, potential effects on depressive symptoms, and side effects were analyzed using Numeric Rating Scales (NRS).

Results

Side effects were rare (in 4% of sessions) with moderate subjective severity and only transient. Patients significantly improved in the ADAS and ADAS Cog, while there was no significant effect in MMSE and MoCA. Patients' self-reported symptom severity improved significantly. The depressive symptoms measured in an ADAS subscale also improved significantly. Statistical data analyses revealed no significant correlation of clinical improvement with baseline symptom severity.

Conclusion

TPS might be a safe and promising add-on therapy for Alzheimer's, even for moderate-to-severe patients. More research on long-term effects in patients as well as studies with sham control groups is needed. Moreover, translational research on the mechanisms of action and effects on cerebral network physiology will be needed to understand this new neuromodulation technique.

Ultrasound Neuromodulation Reduces Demyelination in a Rat Model of Multiple Sclerosis

Microglia, astrocytes, and oligodendrocyte progenitor cells (OPCs) may serve as targets for remyelination-enhancing therapy. Low-intensity pulsed ultrasound (LIPUS) has been demonstrated to ameliorate myelin loss and inhibit neuroinflammation in animal models of brain disorders; however, the underlying mechanisms through which LIPUS stimulates remyelination and glial activation are not well-understood. This study explored the impacts of LIPUS on remyelination and resident cells following lysolecithin (LPC)-induced local demyelination in the hippocampus. Demyelination was induced by the micro-injection of 1.5 μL of 1% LPC into the rat hippocampus, and the treatment groups received daily LIPUS stimulation for 5 days. The therapeutic effects of LIPUS on LPC-induced demyelination were assessed through immunohistochemistry staining. The staining was performed to evaluate remyelination and Iba-1 staining as a microglia marker. Our data revealed that LIPUS significantly increased myelin basic protein (MBP) expression. Moreover, the IHC results showed that LIPUS significantly inhibited glial cell activation, enhanced mature oligodendrocyte density, and promoted brain-derived neurotrophic factor (BDNF) expression at the lesion site. In addition, a heterologous population of microglia with various morphologies can be found in the demyelination lesion after LIPUS treatment. These data show that LIPUS stimulation may serve as a potential treatment for accelerating remyelination through the attenuation of glial activation and the enhancement of mature oligodendrocyte density and BDNF production.