Neural circuit repair by low-intensity magnetic stimulation requires cellular magnetoreceptors and specific stimulation patterns

Biological effects of electromagnetic fields on insects: a systematic review and meta-analysis

Worldwide, insects are declining at an alarming rate. Among other causes, the use of pesticides and modern agricultural practices play a major role in this. Cumulative effects of multiple low-dose toxins and the distribution of toxicants in nature have only started to be investigated in a methodical way. Existing research indicates another factor of anthropogenic origin that could have subtle harmful effects: the increasingly frequent use of electromagnetic fields (EMF) from man-made technologies. This systematic review summarizes the results of studies investigating the toxicity of electromagnetic fields in insects. The main objective of this review is to weigh the evidence regarding detrimental effects on insects from the increasing technological infrastructure, with a particular focus on power lines and the cellular network. The next generation of mobile communication technologies, 5G, is being deployed - without having been tested in respect of potential toxic effects. With humanity's quest for pervasiveness of technology, even modest effects of electromagnetic fields on organisms could eventually reach a saturation level that can no longer be ignored. An overview of reported effects and biological mechanisms of exposure to electromagnetic fields, which addresses new findings in cell biology, is included. Biological effects of non-thermal EMF on insects are clearly proven in the laboratory, but only partly in the field, thus the wider ecological implications are still unknown. There is a need for more field studies, but extrapolating from the laboratory, as is common practice in ecotoxicology, already warrants increasing the threat level of environmental EMF impact on insects.

Early intervention using long-term rhythmic pulsed magnetic stimulation alleviates cognitive decline in a 5xFAD mouse model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most prevalent form of dementia, but no effective therapeutic strategy is available to date. Rhythmic magnetic stimulation is an attractive means of neuron modulation that could be beneficial for restoring learning and memory abilities.

OBJECTIVE

To assess the effect of a compound pulsed rhythmic magnetic field (cPMF) on cognition during AD progression and to explore the appropriate cPMF intervention period.

METHODS

Female 5xFAD mice aged 10 weeks and 18 weeks were exposed to cPMF with a carrier frequency of 40 Hz, repeated at 5 Hz for 1 h/d for 8 consecutive weeks. The Morris water maze (MWM) test was used for cognitive behavioral assessment. Furthermore, changes in molecular pathology within the brain were detected using immunofluorescence staining and real-time PCR.

RESULTS

10-week-old AD mice treated with cPMF explored the target quadrant more frequently than sham-exposed AD mice in MWM test, exhibiting improved learning and memory abilities. Additionally, cPMF exposure alleviated Aβ plaque deposition and astrogliosis in the AD brain. Moreover, neurotrophic factor fibroblast growth factor 1 (FGF1) in the AD brain was upregulated by cPMF treatment. However, in 18-week-old AD mice treated with cPMF, cognitive performance and Fgf1 gene expression were not significantly improved, although Aβ plaque deposition and astrogliosis were alleviated.

CONCLUSION

Early intervention via long-term rhythmic cPMF stimulation may alleviate the histopathological features and enhance neuroprotective gene Fgf1 expression, thereby improving the cognitive performance of 5xFAD mice, which should provide promising insight for the clinical treatment of patients with AD.

Electric Field Characteristics of Rotating Permanent Magnet Stimulation

Neurostimulation devices that use rotating permanent magnets are being explored for their potential therapeutic benefits in patients with psychiatric and neurological disorders. This study aims to characterize the electric field (E-field) for ten configurations of rotating magnets using finite element analysis and phantom measurements. Various configurations were modeled, including single or multiple magnets, and bipolar or multipolar magnets, rotated at 10, 13.3, and 350 revolutions per second (rps). E-field strengths were also measured using a hollow sphere (r=9.2 cm) filled with a 0.9% sodium chloride solution and with a dipole probe. The E-field spatial distribution is determined by the magnets' dimensions, number of poles, direction of the magnetization, and axis of rotation, while the E-field strength is determined by the magnets' rotational frequency and magnetic field strength. The induced E-field strength on the surface of the head ranged between 0.0092 and 0.52 V/m. In the range of rotational frequencies applied, the induced E-field strengths were approximately an order or two of magnitude lower than those delivered by conventional transcranial magnetic stimulation. The impact of rotational frequency on E-field strength represents a confound in clinical trials that seek to tailor rotational frequency to individual neural oscillations. This factor could explain some of the variability observed in clinical trial outcomes.

Neuroprotective effects of repetitive transcranial magnetic stimulation on Alzheimer's disease: Undetermined therapeutic protocols and mechanisms

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by gradual deterioration of cognitive functions, for which an effective treatment is currently unavailable. Repetitive transcranial magnetic stimulation (rTMS), a well‐established noninvasive brain stimulation method, is utilized in clinical settings to address various neuropsychiatric conditions, such as depression, neuropathic pain, and poststroke dysfunction. Increasing evidence suggests that rTMS may enhance cognitive abilities in individuals with AD. However, its optimal therapeutic protocols and precise mechanisms are currently unknown, impeding its clinical implementation. In the present review, we aimed to summarize and discuss the efficacy‐related parameters in rTMS treatment, encompassing stimulus frequency, stimulus pattern, stimulus intensity, and the configuration of the stimulus coil. Furthermore, we reviewed promising rTMS therapeutic protocols involving various combinations of these factors, that were examined in clinical studies. Based on our analysis, we propose that a multisite high‐frequency rTMS (HF‐rTMS) regimen has value in AD therapy, and that promising single‐site protocols, such as HF‐rTMS, applied over the left dorsolateral prefrontal cortex, precuneus, or cerebellum are required to be validated in larger clinical studies. Lastly, we provide a comprehensive review of the potential mechanisms underlying the neuroprotective effects of rTMS on cognition in AD in terms of brain network modulation as well as cellular and molecular reactions. In conclusion, the interaction of diverse mechanisms may be responsible for the total therapeutic effect of rTMS on AD. This review provides theoretical and practical evidence for the future clinical application and scientific research of rTMS in AD.

Polysaccharides as a promising platform for the treatment of spinal cord injury: A review

Spinal cord injury is incurable and often results in irreversible damage to motor function and autonomic sensory abilities. To enhance the effectiveness of therapeutic substances such as cells, growth factors, drugs, and nucleic acids for treating spinal cord injuries, as well as to reduce the toxic side effects of chemical reagents, polysaccharides have been gained attention due to their immunomodulatory properties and the biocompatibility and biodegradability of polysaccharide scaffolds. Polysaccharides hold potential as drug delivery systems in treating spinal cord injuries. This article aims to present an extensive evaluation of the potential applications of polysaccharide materials in scaffold construction, drug delivery, and immunomodulation over the past five years so that offering new directions and opportunities for the treatment of spinal cord injuries.

Electric field characteristics of rotating permanent magnet stimulation

Neurostimulation devices that use rotating permanent magnets are being explored for their potential therapeutic benefits in patients with psychiatric and neurological disorders. This study aims to characterize the electric field (E-field) for ten configurations of rotating magnets using finite element analysis and phantom measurements. Various configurations were modeled, including single or multiple magnets, bipolar or multipolar magnets, rotated at 10, 13.3, and 400 Hz. E-field strengths were also measured using a hollow sphere ( r = 9.2 cm) filled with a 0.9% sodium chloride solution and with a dipole probe. The E-field spatial distribution is determined by the magnets' dimensions, number of poles, direction of the magnetization, and axis of rotation, while the E-field strength is determined by the magnets' rotational frequency and magnetic field strength. The induced E-field strength on the surface of the head ranged between 0.0092 and 0.59 V/m. At the range of rotational frequencies applied, the induced E-field strengths were approximately an order or two of magnitude lower than those delivered by conventional transcranial magnetic stimulation. The impact of rotational frequency on E-field strength represents a previously unrecognized confound in clinical trials that seek to personalize stimulation frequency to individual neural oscillations and may represent a mechanism to explain some clinical trial results.

Intermittent Theta Burst Stimulation Attenuates Cognitive Deficits and Alzheimer's Disease-Type Pathologies via ISCA1-Mediated Mitochondrial Modulation in APP/PS1 Mice

Intermittent theta burst stimulation (iTBS), a time-saving and cost-effective repetitive transcranial magnetic stimulation regime, has been shown to improve cognition in patients with Alzheimer's disease (AD). However, the specific mechanism underlying iTBS-induced cognitive enhancement remains unknown. Previous studies suggested that mitochondrial functions are modulated by magnetic stimulation. Here, we showed that iTBS upregulates the expression of iron-sulfur cluster assembly 1 (ISCA1, an essential regulatory factor for mitochondrial respiration) in the brain of APP/PS1 mice. In vivo and in vitro studies revealed that iTBS modulates mitochondrial iron-sulfur cluster assembly to facilitate mitochondrial respiration and function, which is required for ISCA1. Moreover, iTBS rescues cognitive decline and attenuates AD-type pathologies in APP/PS1 mice. The present study uncovers a novel mechanism by which iTBS modulates mitochondrial respiration and function via ISCA1-mediated iron-sulfur cluster assembly to alleviate cognitive impairments and pathologies in AD. We provide the mechanistic target of iTBS that warrants its therapeutic potential for AD patients.

Engineering the Physical Microenvironment into Neural Organoids for Neurogenesis and Neurodevelopment

Understanding the signals from the physical microenvironment is critical for deciphering the processes of neurogenesis and neurodevelopment. The discovery of how surrounding physical signals shape human developing neurons is hindered by the bottleneck of conventional cell culture and animal models. Notwithstanding neural organoids provide a promising platform for recapitulating human neurogenesis and neurodevelopment, building neuronal physical microenvironment that accurately mimics the native neurophysical features is largely ignored in current organoid technologies. Here, it is discussed how the physical microenvironment modulates critical events during the periods of neurogenesis and neurodevelopment, such as neural stem cell fates, neural tube closure, neuronal migration, axonal guidance, optic cup formation, and cortical folding. Although animal models are widely used to investigate the impacts of physical factors on neurodevelopment and neuropathy, the important roles of human stem cell-derived neural organoids in this field are particularly highlighted. Considering the great promise of human organoids, building neural organoid microenvironments with mechanical forces, electrophysiological microsystems, and light manipulation will help to fully understand the physical cues in neurodevelopmental processes. Neural organoids combined with cutting-edge techniques, such as advanced atomic force microscopes, microrobots, and structural color biomaterials might promote the development of neural organoid-based research and neuroscience.

Pax3 induces target-specific reinnervation through axon collateral expression of PSA-NCAM

Damaged or dysfunctional neural circuits can be replaced after a lesion by axon sprouting and collateral growth from undamaged neurons. Unfortunately, these new connections are often disorganized and rarely produce clinical improvement. Here we investigate how to promote post-lesion axonal collateral growth, while retaining correct cellular targeting. In the mouse olivocerebellar path, brain-derived neurotrophic factor (BDNF) induces correctly-targeted post-lesion cerebellar reinnervation by remaining intact inferior olivary axons (climbing fibers). In this study we identified cellular processes through which BDNF induces this repair. BDNF injection into the denervated cerebellum upregulates the transcription factor Pax3 in inferior olivary neurons and induces rapid climbing fiber sprouting. Pax3 in turn increases polysialic acid-neural cell adhesion molecule (PSA-NCAM) in the sprouting climbing fiber path, facilitating collateral outgrowth and pathfinding to reinnervate the correct targets, cerebellar Purkinje cells. BDNF-induced reinnervation can be reproduced by olivary Pax3 overexpression, and abolished by olivary Pax3 knockdown, suggesting that Pax3 promotes axon growth and guidance through upregulating PSA-NCAM, probably on the axon's growth cone. These data indicate that restricting growth-promotion to potential reinnervating afferent neurons, as opposed to stimulating the whole circuit or the injury site, allows axon growth and appropriate guidance, thus accurately rebuilding a neural circuit.

Magnetic Stimulation as a Therapeutic Approach for Brain Modulation and Repair: Underlying Molecular and Cellular Mechanisms

Neurological and psychiatric diseases generally have no cure, so innovative non-pharmacological treatments, including non-invasive brain stimulation, are interesting therapeutic tools as they aim to trigger intrinsic neural repair mechanisms. A common brain stimulation technique involves the application of pulsed magnetic fields to affected brain regions. However, investigations of magnetic brain stimulation are complicated by the use of many different stimulation parameters. Magnetic brain stimulation is usually divided into two poorly connected approaches: (1) clinically used high-intensity stimulation (0.5-2 Tesla, T) and (2) experimental or epidemiologically studied low-intensity stimulation (μT-mT). Human tests of both approaches are reported to have beneficial outcomes, but the underlying biology is unclear, and thus optimal stimulation parameters remain ill defined. Here, we aim to bring together what is known about the biology of magnetic brain stimulation from human, animal, and in vitro studies. We identify the common effects of different stimulation protocols; show how different types of pulsed magnetic fields interact with nervous tissue; and describe cellular mechanisms underlying their effects-from intracellular signalling cascades, through synaptic plasticity and the modulation of network activity, to long-term structural changes in neural circuits. Recent advances in magneto-biology show clear mechanisms that may explain low-intensity stimulation effects in the brain. With its large breadth of stimulation parameters, not available to high-intensity stimulation, low-intensity focal magnetic stimulation becomes a potentially powerful treatment tool for human application.

Theta Frequency Electromagnetic Stimulation Enhances Functional Recovery After Stroke

Extremely low-frequency, low-intensity electromagnetic field (ELF-EMF) therapy is a non-invasive brain stimulation method that can modulate neuroprotection and neuroplasticity. ELF-EMF was recently shown to enhance recovery in human stroke in a small pilot clinical trial (NCT04039178). ELF-EMFs encompass a wide range of frequencies, typically ranging from 1 to 100 Hz, and their effects can vary depending on the specific frequency employed. However, whether and to what extent the effectiveness of ELF-EMFs depends on the frequency remains unclear. In the present study, we aimed to assess the efficacy of different frequency-intensity protocols of ELF-EMF in promoting functional recovery in a mouse cortical stroke model with treatment initiated 4 days after the stroke, employing a series of motor behavior tests. Our findings demonstrate that a theta-frequency ELF-EMF (5 Hz) effectively enhances functional recovery in a reach-to-grasp task, whereas neither gamma-frequency (40 Hz) nor combination frequency (5-16-40 Hz) ELF-EMFs induce a significant effect. Importantly, our histological analysis reveals that none of the ELF-EMF protocols employed in our study affect infarct volume, inflammatory, or glial activation, suggesting that the observed beneficial effects may be mediated through non-neuroprotective mechanisms. Our data indicate that ELF-EMFs have an influence on functional recovery after stroke, and this effect is contingent upon the specific frequency used. These findings underscore the critical importance of optimizing the protocol parameters to maximize the beneficial effects of ELF-EMF. Further research is warranted to elucidate the underlying mechanisms and refine the protocol parameters for optimal therapeutic outcomes in stroke rehabilitation.

Hindbrain Stimulation Modulates Object Recognition Discrimination Efficiency and Hippocampal Synaptic Connections

(1) Background: The cerebellum is well known to have functionalities beyond the control of motor function. However, brain stimulation studies have not explored the potential of this region to impact downstream processes which are imperative to multiple neurological conditions. Our study aimed to look at preliminary evidence that hindbrain-targeted repetitive transcranial magnetic stimulation (rTMS) in mice could alter motor, cognitive and anxiety measures; (2) Methods: Male B6129SF2/J mice (n = 16) were given rTMS (n = 9) over lambda at 10 Hz for 10 min or Sham (n = 7) for 14 consecutive days. Mice then underwent a battery of behavioral measures. (3) Results: In the object recognition test, only rTMS-treated mice distinguished between the novel object at 5 min, whereas those that received Sham treatment continued to improve discrimination from 5 to 10 min. Additionally, over the 10 min test phase, rTMS-stimulated mice explored the objects less than the Sham mice. This was accompanied by increased colocalization of presynaptic and postsynaptic markers in the hippocampus in the rTMS mice (4) Conclusions: Hindbrain rTMS stimulation elicits improved processing speed in the object recognition test via structural plasticity mechanisms in the hippocampus and could provide additional ways of targeting these important substructures of the brain.

Functional material-mediated wireless physical stimulation for neuro-modulation and regeneration

Nerve injuries and neurological diseases remain intractable clinical challenges. Despite the advantages of stem cell therapy in treating neurological disorders, uncontrollable cell fates and loss of cell function in vivo are still challenging. Recently, increasing attention has been given to the roles of external physical signals, such as electricity and ultrasound, in regulating stem cell fate as well as activating or inhibiting neuronal activity, which provides new insights for the treatment of neurological disorders. However, direct physical stimulations in vivo are short in accuracy and safety. Functional materials that can absorb energy from a specific physical field exerted in a wireless way and then release another localized physical signal hold great advantages in mediating noninvasive or minimally invasive accurate indirect physical stimulations to promote the therapeutic effect on neurological disorders. In this review, the mechanism by which various physical signals regulate stem cell fate and neuronal activity is summarized. Based on these concepts, the approaches of using functional materials to mediate indirect wireless physical stimulation for neuro-modulation and regeneration are systematically reviewed. We expect that this review will contribute to developing wireless platforms for neural stimulation as an assistance for the treatment of neurological diseases and injuries.

A new synthesis method for complex electric field patterning using a multichannel dense array system with applications in low-intensity noninvasive neuromodulation

Multichannel coil array systems offer precise spatiotemporal electronic steering and patterning of electric and magnetic fields without the physical movement of coils or magnets. This capability could potentially benefit a wide range of biomagnetic applications such as low-intensity noninvasive neuromodulation or magnetic drug delivery. In this regard, the objective of this work is to develop a unique synthesis method, that enabled by a multichannel dense array system, generates complex current pattern distributions not previously reported in the literature. Simulations and experimental results verify that highly curved or irregular (e.g., zig-zag) patterns at singular and multiple sites can be efficiently formed using this method. The synthesis method is composed of three primary components; a pixel cell (basic unit of pattern formation), a template array ("virtual array": code that disseminates the coil current weights to the "physical" dense array), and a hexagonal coordinate system. Low-intensity or low-field magnetic stimulation is identified as a potential application that could benefit from this work in the future and as such is used as an example to frame the research.

Cognitive improvement via a modulated rhythmic pulsed magnetic field in D-galactose-induced accelerated aging mice

Rhythmic physical stimulations have emerged as effective noninvasive intervention strategies in the treatment of pathological cognitive deficits. Transcranial magnetic stimulation (TMS) can regulate neural firing and improve the learning and memory abilities of rodents or patients with cognitive deterioration. However, the effects of elaborate magnetic stimulation with low intensity during aging or other neurological disordering processes on cognitive decline remain unclear. In this study, we developed an elaborate modulated pulsed magnetic field (PMF) stimulation with a complex pattern in the theta repeated frequency and gamma carrier frequency and then determined the effects of this rhythmic PMF on the cognitive function of accelerated aging mice established by chronic subcutaneous injection of D-galactose (D-gal). The results of the Morris water maze (MWM) test showed that mice treated with modulated PMF displayed shorter swimming distance and latency time in the spatial exploration acquisition trial and exhibited a significant preference in the target presumptive platform area in the probe trial, all of which indicated the enhancement in spatial learning and memory abilities upon PMF stimulation of the accelerated aging mice. The novel object recognition (NOR) test results showed a similar tendency as the MWM results although without statistical significance. Further determination of histological structures demonstrated that the cognitive function-related hippocampal CA3 neurons degenerated upon D-gal injection, which could also be partially rescued by PMF application. In comparison with the high-intensity TMS approach, low-intensity magnetic stimulation could be much safer and allow deeper penetration without adverse effects such as seizure. In summary, modulated PMF, even with low intensity, could effectively improve rodent cognitive functions impaired by D-gal-induced accelerated aging, which might provide a new safe therapeutic strategy for cognitive deficits as well as other neurological disorders.

Effects of Low-Frequency (0.5 Hz) and High-Frequency (10 Hz) Repetitive Transcranial Magnetic Stimulation on Neurological Function, Motor Function, and Excitability of Cortex in Ischemic Stroke Patients

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulation technique. The purpose of our study is to explore the effects of low-frequency (0.5 Hz) and high-frequency (10 Hz) rTMS on neurological function, motor function, and excitability of cortex in Chinese ischemic stroke patients.

MATERIALS AND METHODS

A total of 240 ischemic stroke patients were collected. The National Institutes of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS), motor-evoked potential (MEP) cortical latency, central motor conduction time (CMCT), Fugel-Meyer assessment (FMA), Berg balance scale (BBS), and modified Barthel index (MBI) scores were recorded.

RESULTS

After treatment, the NIHSS, mRS, MEP cortical latency, CMCT, FMA, BBS, and MBI scores of the high-frequency group and low-frequency group were significantly improved than the sham stimulation group, and the changes in the low-frequency group were more significant (adjusted P <0.05). Compared with the sham stimulation group, high-frequency stimulation reduced the NIHSS score by 9.5%, mRS score by 12.6%, MEP latency by 2.5%, and CMCT by 5.8%, and increased the upper limb FMA scale by 16.4%, lower limb FMA scale by 8.8%, BBS by 26.3%, and MBI by 9.3%, while low-frequency stimulation reduced the NIHSS score by 23.8%, mRS score by 25.3%, MEP Latency by 11.7%, and CMCT by 9.1%, and increased the upper limb FMA scale by 24.1%, lower limb FMA scale by 18.4%, BBS by 27.4%, and MBI by 23.7% in our cohort.

CONCLUSIONS

Low-frequency rTMS is better than high-frequency rTMS stimulation in improving neurological function, motor function, and excitability of cortex in ischemic stroke.

EMAGINE-Study protocol of a randomized controlled trial for determining the efficacy of a frequency tuned electromagnetic field treatment in facilitating recovery within the subacute phase following ischemic stroke

Stroke is a leading cause of disability with limited effective interventions that improve recovery in the subacute phase. This protocol aims to evaluate the safety and efficacy of a non-invasive, extremely low-frequency, low-intensity, frequency-tuned electromagnetic field treatment [Electromagnetic Network Targeting Field (ENTF) therapy] in reducing disability and promoting recovery in people with subacute ischemic stroke (IS) with moderate-severe disability and upper extremity (UE) motor impairment. Following a sample-size adaptive design with a single interim analysis, at least 150 and up to 344 participants will be recruited to detect a 0.5-point (with a minimum of 0.33 points) difference on the modified Rankin Scale (mRS) between groups with 80% power at a 5% significance level. This ElectroMAGnetic field Ischemic stroke-Novel subacutE treatment (EMAGINE) trial is a multicenter, double-blind, randomized, sham-controlled, parallel two-arm study to be conducted at approximately 20 United States sites, and enroll participants with subacute IS and moderate-severe disability with UE motor impairment. Participants will be assigned to active (ENTF) or sham treatment, initiated 4-21 days after stroke onset. The intervention, applied to the central nervous system, is designed for suitability in multiple clinical settings and at home. Primary endpoint is change in mRS score from baseline to 90 days post-stroke. Secondary endpoints: change from baseline to 90 days post-stroke on the Fugl-Meyer Assessment - UE (lead secondary endpoint), Box and Block Test, 10-Meter Walk, and others, to be analyzed in a hierarchical manner. EMAGINE will evaluate whether ENTF therapy is safe and effective at reducing disability following subacute IS.

Trial registration

www.ClinicalTrials.gov, NCT05044507 (14 September 2021).

Frequency-tuned electromagnetic field therapy improves post-stroke motor function: A pilot randomized controlled trial

BACKGROUND AND PURPOSE

Impaired upper extremity (UE) motor function is a common disability after ischemic stroke. Exposure to extremely low frequency and low intensity electromagnetic fields (ELF-EMF) in a frequency-specific manner (Electromagnetic Network Targeting Field therapy; ENTF therapy) is a non-invasive method available to a wide range of patients that may enhance neuroplasticity, potentially facilitating motor recovery. This study seeks to quantify the benefit of the ENTF therapy on UE motor function in a subacute ischemic stroke population.

METHODS

In a randomized, sham-controlled, double-blind trial, ischemic stroke patients in the subacute phase with moderately to severely impaired UE function were randomly allocated to active or sham treatment with a novel, non-invasive, brain computer interface-based, extremely low frequency and low intensity ENTF therapy (1-100 Hz, < 1 G). Participants received 40 min of active ENTF or sham treatment 5 days/week for 8 weeks; ~three out of the five treatments were accompanied by 10 min of concurrent physical/occupational therapy. Primary efficacy outcome was improvement on the Fugl-Meyer Assessment - Upper Extremity (FMA-UE) from baseline to end of treatment (8 weeks).

RESULTS

In the per protocol set (13 ENTF and 8 sham participants), mean age was 54.7 years (±15.0), 19% were female, baseline FMA-UE score was 23.7 (±11.0), and median time from stroke onset to first stimulation was 11 days (interquartile range (IQR) 8-15). Greater improvement on the FMA-UE from baseline to week 4 was seen with ENTF compared to sham stimulation, 23.2 ± 14.1 vs. 9.6 ± 9.0, p = 0.007; baseline to week 8 improvement was 31.5 ± 10.7 vs. 23.1 ± 14.1. Similar favorable effects at week 8 were observed for other UE and global disability assessments, including the Action Research Arm Test (Pinch, 13.4 ± 5.6 vs. 5.3 ± 6.5, p = 0.008), Box and Blocks Test (affected hand, 22.5 ± 12.4 vs. 8.5 ± 8.6, p < 0.0001), and modified Rankin Scale (-2.5 ± 0.7 vs. -1.3 ± 0.7, p = 0.0005). No treatment-related adverse events were reported.

CONCLUSIONS

ENTF stimulation in subacute ischemic stroke patients was associated with improved UE motor function and reduced overall disability, and results support its safe use in the indicated population. These results should be confirmed in larger multicenter studies.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT04039178, identifier: NCT04039178.

Neural Circuit Repair by Low-Intensity rTMS

Electromagnetic brain stimulation is a promising treatment in neurology and psychiatry. However, clinical outcomes are variable and underlying mechanisms remain ill-defined, impeding the development of new effective stimulation protocols. There is increasing application of repetitive transcranial magnetic stimulation (rTMS) to the cerebellum to induce forebrain plasticity through its long-distance cerebello-cerebral circuits. To better understand what magnetic stimulation does within the cerebellum, we have developed tools to generate defined low-intensity (LI) magnetic fields and deliver them in vivo, in 3D organotypic culture and in primary cultures, over a range of stimulation parameters. Here we show that low-intensity rTMS (LI-rTMS) to the cerebellum induces axon growth and synapse formation providing olivocerebellar reinnervation. This repair depends on stimulation pattern, with complex biomimetic patterns being most effective, and this requires the presence of a cellular magnetoreceptor, cryptochrome. To explain these reparative changes, we found that repair-promoting LI-rTMS patterns, but not ineffective ones, increased c-fos expression in Purkinje neurons, consistent with the production of reactive oxygen species by activated cryptochrome. Rather than activating neurons via induced electric currents, we propose that weak magnetic fields act through cryptochrome, activating intracellular signals that induce climbing fibre-Purkinje cell reinnervation. This information opens new routes to optimize cerebellar magnetic stimulation and its potential role as an effective treatment for neurological diseases.

Accelerated low-intensity rTMS does not rescue anxiety behaviour or abnormal connectivity in young adult rats following chronic restraint stress

Currently approved repetitive transcranial magnetic stimulation (rTMS) protocols for the treatment of major depressive disorder (MDD) involve once-daily (weekday) stimulation sessions, with 10 Hz or intermittent theta burst stimulation (iTBS) frequencies, over 4-6 weeks. Recently, accelerated treatment protocols (multiple daily stimulation sessions for 1-2 weeks) have been increasingly studied to optimize rTMS treatments. Accelerated protocols might confer unique advantages for adolescents and young adults but there are many knowledge gaps related to dosing in this age group. Off-label, clinical practice frequently outpaces solid evidence as rigorous clinical trials require substantial time and resources. Murine models present an opportunity for high throughput dose finding studies to focus subsequent clinical trials in humans. This project investigated the brain and behavioural effects of an accelerated low-intensity rTMS (LI-rTMS) protocol in a young adult rodent model of chronic restraint stress (CRS). Depression and anxiety-related behaviours were induced in young adult male Sprague Dawley rats using the CRS model, followed by the 3-times-daily delivery of 10 Hz LI-rTMS, for two weeks. Behaviour was assessed using the Elevated Plus Maze and Forced Swim Test, and functional, chemical, and structural brain changes measured using magnetic resonance imaging techniques. CRS induced an agitated depression-like phenotype but therapeutic effects from the accelerated protocol were not detected. Our findings suggest that the age of rodents may impact response to CRS and LI-rTMS. Future studies should also examine higher intensities of rTMS and accelerated theta burst protocols.

Exposure to static magnetic field facilitates selective attention and neuroplasticity in rats

Static magnetic fields (SMF) have neuroprotective and behavioral effects in rats, however, little is known about the effects of SMF on cognition, motor function and the underlying neurochemical mechanisms. In this study, we focused on the effects of short-term (5~10d) and long-term (13~38d) SMF exposure on selective attention and motor coordination of rats, as well as associated alterations in expression level of neuroplasticity-related structural proteins and cryptochrome (CRY1) protein in the cortex, striatum and ventral midbrain. The results showed that 6 d SMF exposure significantly enhanced selective attention without affecting locomotor activity in open field. All SMF exposures non-significantly enhanced motor coordination (Rotarod test). Neurochemical analysis demonstrated that 5d SMF exposure increased the expression of cortical and striatal CRY1 and synapsin-1 (SYN1), striatal total synapsins (SYN), and synaptophysin (SYP), growth associated protein-43 (GAP43) and post-synaptic density protein-95 (PSD95) in the ventral midbrain. Exposure to SMF for 14d increased PSD95 level in the ventral midbrain while longer SMF exposure elevated the levels of PSD95 in the cortex, SYN and SYN1 in all the examined brain areas. The increased expression of cortical and striatal CRY1and SYN1 correlated with the short-lasting effect of SMF on improving selective attention. Collectively, SMF's effect on selective attention attenuated following longer exposure to SMF whereas its effects on neuroplasticity-related structural biomarkers were time- and brain area-dependent, with some protein levels increasing with longer time exposure. These findings suggest a potential use of SMF for treatment of neurological diseases in which selective attention or neuroplasticity is impaired.

Magnetic field effects in biology from the perspective of the radical pair mechanism

Hundreds of studies have found that weak magnetic fields can significantly influence various biological systems. However, the underlying mechanisms behind these phenomena remain elusive. Remarkably, the magnetic energies implicated in these effects are much smaller than thermal energies. Here, we review these observations, and we suggest an explanation based on the radical pair mechanism, which involves the quantum dynamics of the electron and nuclear spins of transient radical molecules. While the radical pair mechanism has been studied in detail in the context of avian magnetoreception, the studies reviewed here show that magnetosensitivity is widespread throughout biology. We review magnetic field effects on various physiological functions, discussing static, hypomagnetic and oscillating magnetic fields, as well as isotope effects. We then review the radical pair mechanism as a potential unifying model for the described magnetic field effects, and we discuss plausible candidate molecules for the radical pairs. We review recent studies proposing that the radical pair mechanism provides explanations for isotope effects in xenon anaesthesia and lithium treatment of hyperactivity, magnetic field effects on the circadian clock, and hypomagnetic field effects on neurogenesis and microtubule assembly. We conclude by discussing future lines of investigation in this exciting new area of quantum biology.

In vivo low-intensity magnetic pulses durably alter neocortical neuron excitability and spontaneous activity

KEY POINTS

Repetitive transcranial magnetic stimulation (rTMS) is a promising technique to alleviate neurological and psychiatric disorders caused by alterations in cortical activity. Our knowledge of the cellular mechanisms underlying rTMS-based therapies remains limited. We combined in vivo focal application of low-intensity rTMS (LI-rTMS) to the rat somatosensory cortex with intracellular recordings of subjacent pyramidal neurons to characterize the effects of weak magnetic fields at single cell level. Ten minutes of LI-rTMS delivered at 10 Hz reliably evoked action potentials in cortical neurons during the stimulation period, and induced durable attenuation of their intrinsic excitability, synaptic activity, and spontaneous firing. These results help us better understand the mechanisms of weak magnetic stimulation and should allow optimizing the effectiveness of stimulation protocols for clinical use.

ABSTRACT

Magnetic brain stimulation is a promising treatment for neurological and psychiatric disorders. However, a better understanding of its effects at the individual neuron level is essential to improve its clinical application. We combined focal low-intensity repetitive transcranial magnetic stimulation (LI-rTMS) to the rat somatosensory cortex with intracellular recordings of subjacent pyramidal neurons in vivo. Continuous 10 Hz LI-rTMS reliably evoked firing at ∼4-5 Hz during the stimulation period and induced durable attenuation of synaptic activity and spontaneous firing in cortical neurons, through membrane hyperpolarization and a reduced intrinsic excitability. However, inducing firing in individual neurons by repeated intracellular current injection did not reproduce LI-rTMS effects on neuronal properties. These data provide novel understanding of mechanisms underlying magnetic brain stimulation showing that, in addition to inducing biochemical plasticity, even weak magnetic fields can activate neurons and enduringly modulate their excitability. Abstract figure legend We examined by means of in vivo intracellular recordings in the rodent the effects of low-intensity (10 mT) repetitive transcranial magnetic stimulation (LI-rTMS) on the functional properties of primary somatosensory cortex pyramidal neurons. After a baseline period, during which cortical spontaneous activity and excitability were measured (Pre), LI-rTMS was applied at 10 Hz for 10 minutes. Despite their low intensity, magnetic pulses reliably evoked action potentials in cortical neurons. Ten minutes of LI-rTMS induced a progressive and long-lasting hyperpolarization of the neuronal membrane and a marked decrease in cell firing rate (Post). This was associated with an altered intrinsic neuronal excitability, characterized by reduced membrane input resistance and increased minimal current required to induce neuronal firing. A portion of this figure was created with biorender.com. This article is protected by copyright. All rights reserved.

Cerebellar stimulation prevents Levodopa-induced dyskinesia in mice and normalizes activity in a motor network

Chronic Levodopa therapy, the gold-standard treatment for Parkinson's Disease (PD), leads to the emergence of involuntary movements, called levodopa-induced dyskinesia (LID). Cerebellar stimulation has been shown to decrease LID severity in PD patients. Here, in order to determine how cerebellar stimulation induces LID alleviation, we performed daily short trains of optogenetic stimulations of Purkinje cells (PC) in freely moving LID mice. We demonstrated that these stimulations are sufficient to suppress LID or even prevent their development. This symptomatic relief is accompanied by the normalization of aberrant neuronal discharge in the cerebellar nuclei, the motor cortex and the parafascicular thalamus. Inhibition of the cerebello-parafascicular pathway counteracted the beneficial effects of cerebellar stimulation. Moreover, cerebellar stimulation reversed plasticity in D1 striatal neurons and normalized the overexpression of FosB, a transcription factor causally linked to LID. These findings demonstrate LID alleviation and prevention by daily PC stimulations, which restore the function of a wide motor network, and may be valuable for LID treatment.

Radical pairs may explain reactive oxygen species-mediated effects of hypomagnetic field on neurogenesis

Exposures to a hypomagnetic field can affect biological processes. Recently, it has been observed that hypomagnetic field exposure can adversely affect adult hippocampal neurogenesis and hippocampus-dependent cognition in mice. In the same study, the role of reactive oxygen species (ROS) in hypomagnetic field effects has been demonstrated. However, the mechanistic reasons behind this effect are not clear. This study proposes a radical pair mechanism based on a flavin-superoxide radical pair to explain the modulation of ROS production and the attenuation of adult hippocampal neurogenesis in a hypomagnetic field. The results of our calculations favor a singlet-born radical pair over a triplet-born radical pair. Our model predicts hypomagnetic field effects on the triplet/singlet yield of comparable strength as the effects observed in experimental studies on adult hippocampal neurogenesis. Our predictions are in qualitative agreement with experimental results on superoxide concentration and other observed ROS effects. We also predict the effects of applied magnetic fields and oxygen isotopic substitution on adult hippocampal neurogenesis.

A little goes a long way: Neurobiological effects of low intensity rTMS and implications for mechanisms of rTMS

Repetitive transcranial magnetic stimulation (rTMS) is a widespread technique in neuroscience and medicine, however its mechanisms are not well known. In this review, we consider intensity as a key therapeutic parameter of rTMS, and review the studies that have examined the biological effects of rTMS using magnetic fields that are orders of magnitude lower that those currently used in the clinic. We discuss how extensive characterisation of "low intensity" rTMS has set the stage for translation of new rTMS parameters from a mechanistic evidence base, with potential for innovative and effective therapeutic applications. Low-intensity rTMS demonstrates neurobiological effects across healthy and disease models, which include depression, injury and regeneration, abnormal circuit organisation, tinnitus etc. Various short and long-term changes to metabolism, neurotransmitter release, functional connectivity, genetic changes, cell survival and behaviour have been investigated and we summarise these key changes and the possible mechanisms behind them. Mechanisms at genetic, molecular, cellular and system levels have been identified with evidence that low-intensity rTMS and potentially rTMS in general acts through several key pathways to induce changes in the brain with modulation of internal calcium signalling identified as a major mechanism. We discuss the role that preclinical models can play to inform current clinical research as well as uncover new pathways for investigation.

Radical pairs can explain magnetic field and lithium effects on the circadian clock

Drosophila's circadian clock can be perturbed by magnetic fields, as well as by lithium administration. Cryptochromes are critical for the circadian clock. Further, the radical pairs in cryptochrome also can explain magnetoreception in animals. Based on a simple radical pair mechanism model of the animal magnetic compass, we show that both magnetic fields and lithium can influence the spin dynamics of the naturally occurring radical pairs and hence modulate the circadian clock's rhythms. Using a simple chemical oscillator model for the circadian clock, we show that the spin dynamics influence a rate in the chemical oscillator model, which translates into a change in the circadian period. Our model can reproduce the results of two independent experiments, magnetic field and lithium effects on the circadian clock. Our model predicts that stronger magnetic fields would shorten the clock's period. We also predict that lithium influences the clock in an isotope-dependent manner. Furthermore, our model also predicts that magnetic fields and hyperfine interactions modulate oxidative stress. The findings of this work suggest that the quantum nature of radical pairs might play roles in the brain, as another piece of evidence in addition to recent results on xenon anesthesia and lithium effects on hyperactivity.

Entangled radicals may explain lithium effects on hyperactivity

It is known that bipolar disorder and its lithium treatment involve the modulation of oxidative stress. Moreover, it has been observed that lithium's effects are isotope-dependent. Based on these findings, here we propose that lithium exerts its effects by influencing the recombination dynamics of a naturally occurring radical pair involving oxygen. We develop a simple model inspired by the radical-pair mechanism in cryptochrome in the context of avian magnetoreception and xenon-induced anesthesia. Our model reproduces the observed isotopic dependence in the lithium treatment of hyperactivity in rats. It predicts a magnetic-field dependence of the effectiveness of lithium, which provides one potential experimental test of our hypothesis. Our findings show that Nature might harness quantum entanglement for the brain's cognitive processes.

Comparison of the effects of two therapeutic strategies based on olfactory ensheathing cell transplantation and repetitive magnetic stimulation after spinal cord injury in female mice

Spinal cord injury (SCI) is a debilitating condition, which leads to a permanent loss of functions below the injury site. The events which take place after SCI are characterized by cellular death, release of inhibitory factors, and inflammation. Many therapies have been studied to cure SCI, among them magnetic stimulation aims to reduce the secondary damages in particular by decreasing apoptosis, while, cellular transplantation promotes neuroregeneration by enhancing axonal regrowth. In the present study, we compared individually primary olfactory ensheathing cell (OEC) transplantation and repetitive trans‐spinal magnetic stimulation (rTSMS) and then, we combined these two therapeutic approaches on tissue repair and functional recovery after SCI. To do so, SCIs were performed at Th10 level on female C57BL/6 mice, which were randomized into four groups: SCI, SCI + primary bOECs, SCI + STM, SCI + primary bulbar olfactory ensheathing cells (bOECs) + stimulation (STM). On these animals bioluminescence, immunohistological, and behavioral experiments were performed after SCI. Our results show that rTSMS has beneficial effect on the modulation of spinal scar by reducing fibrosis, demyelination, and microglial cell activation and by increasing the astroglial component of the scar, while, primary bOEC transplantation decreases microglial reactivity. At the opposite, locotronic experiments show that both treatments induce functional recovery. We did not observed any additional effect by combining the two therapeutic approaches. Taken together, the present study indicates that primary bOEC transplantation and rTSMS treatment act through different mechanisms after SCI to induce functional recovery. In our experimental paradigm, the combination of the two therapies does not induce any additional benefit.

Transcranial ultrasound pulse stimulation reduces cortical atrophy in Alzheimer's patients: A follow-up study

INTRODUCTION

Ultrasound for the brain is a revolutionary therapeutic concept. The first clinical data indicate that 2-4 weeks of therapy with transcranial pulse stimulation (TPS) improve functional networks and cognitive performance of Alzheimer's disease (AD) patients for up to 3 months. No data currently exist on possible benefits concerning brain morphology, namely the cortical atrophy characteristic of AD.

METHODS

We performed a pre-/post-therapy analysis of cortical thickness in a group of N = 17 AD patients.

RESULTS

We found a significant correlation between neuropsychological improvement and cortical thickness increase in AD-critical brain areas.

DISCUSSION

AD patients who benefit from TPS appear to manifest reduced cortical atrophy within the default mode network in particular, whose memory-related subsystems are believed to be disrupted in AD. TPS may therefore hold promise as a new add-on therapy for AD.

Rehabilitation effect of rTMS combined with cognitive training on cognitive impairment after traumatic brain injury

OBJECTIVE

To innvestigate the rehabilitation effects of repetitive transcranial magnetic stimulation (rTMS) combined with cognitive training on cognitive impairment in patients with traumatic brain injury (TBI) by using multimodal magnetic resonance imaging.

METHODS

Clinical data of 166 patients with cognitive impairment after TBI were retrospectively analyzed. The patients were assigned into an observation group and a control group according to different treatment methods, with 83 cases in each group. The observation group was given rTMS + cognitive training, and the control group was given cognitive training only. The changes in GCS score, the Cho/Cr, Cho/NAA and NAA/Cr ratios examined by MRSI, the score of cognitive impairment, the grading of cognitive impairment, and the changes in modified Barthel index were observed and compared between the two groups.

RESULTS

The GCS score, and the ratios of Cho/Cr, Cho/NAA and NAA/Cr after treatment were better than those before treatment in both groups and were lower in the observation group compared with the control group (all P<0.05). The score and grading of cognitive impairment as well as modified Barthel index after treatment were all significantly better in the observation group than in the control group (all P<0.05).

CONCLUSION

rTMS can improve the rehabilitation effect on cognitive impairment in patients after TBI and is recommended for clinical use.

Safety and recommendations for TMS use in healthy subjects and patient populations, with updates on training, ethical and regulatory issues: Expert Guidelines

This article is based on a consensus conference, promoted and supported by the International Federation of Clinical Neurophysiology (IFCN), which took place in Siena (Italy) in October 2018. The meeting intended to update the ten-year-old safety guidelines for the application of transcranial magnetic stimulation (TMS) in research and clinical settings (Rossi et al., 2009). Therefore, only emerging and new issues are covered in detail, leaving still valid the 2009 recommendations regarding the description of conventional or patterned TMS protocols, the screening of subjects/patients, the need of neurophysiological monitoring for new protocols, the utilization of reference thresholds of stimulation, the managing of seizures and the list of minor side effects. New issues discussed in detail from the meeting up to April 2020 are safety issues of recently developed stimulation devices and pulse configurations; duties and responsibility of device makers; novel scenarios of TMS applications such as in the neuroimaging context or imaging-guided and robot-guided TMS; TMS interleaved with transcranial electrical stimulation; safety during paired associative stimulation interventions; and risks of using TMS to induce therapeutic seizures (magnetic seizure therapy). An update on the possible induction of seizures, theoretically the most serious risk of TMS, is provided. It has become apparent that such a risk is low, even in patients taking drugs acting on the central nervous system, at least with the use of traditional stimulation parameters and focal coils for which large data sets are available. Finally, new operational guidelines are provided for safety in planning future trials based on traditional and patterned TMS protocols, as well as a summary of the minimal training requirements for operators, and a note on ethics of neuroenhancement.

Low intensity repetitive magnetic stimulation reduces expression of genes related to inflammation and calcium signalling in cultured mouse cortical astrocytes

Repetitive transcranial magnetic stimulation (rTMS) is a form of non-invasive brain stimulation frequently used to induce neuroplasticity in the brain. Even at low intensities, rTMS has been shown to modulate aspects of neuronal plasticity such as motor learning and structural reorganisation of neural tissue. However, the impact of low intensity rTMS on glial cells such as astrocytes remains largely unknown. This study investigated changes in RNA (qPCR array: 125 selected genes) and protein levels (immunofluorescence) in cultured mouse astrocytes following a single session of low intensity repetitive magnetic stimulation (LI-rMS - 18 mT). Purified neonatal cortical astrocyte cultures were stimulated with either 1Hz (600 pulses), 10Hz (600 or 6000 pulses) or sham (0 pulses) LI-rMS, followed by RNA extraction at 5 h post-stimulation, or fixation at either 5 or 24-h post-stimulation. LI-rMS resulted in a two-to-four-fold downregulation of mRNA transcripts related to calcium signalling (Stim1 and Orai3), inflammatory molecules (Icam1) and neural plasticity (Ncam1). 10Hz reduced expression of Stim1, Orai3, Kcnmb4, and Ncam1 mRNA, whereas 1Hz reduced expression of Icam1 mRNA and signalling-related genes. Protein levels followed a similar pattern for 10Hz rMS, with a significant reduction of STIM1, ORAI3, KCNMB4, and NCAM1 protein compared to sham, but 1Hz increased STIM1 and ORAI3 protein levels relative to sham. These findings demonstrate the ability of 1Hz and 10Hz LI-rMS to modulate specific aspects of astrocytic phenotype, potentially contributing to the known effects of low intensity rTMS on excitability and neuroplasticity.

HEK293 cell response to static magnetic fields via the radical pair mechanism may explain therapeutic effects of pulsed electromagnetic fields

PEMF (Pulsed Electromagnetic Field) stimulation has been used for therapeutic purposes for over 50 years including in the treatment of memory loss, depression, alleviation of pain, bone and wound healing, and treatment of certain cancers. However, the underlying cellular mechanisms mediating these effects have remained poorly understood. In particular, because magnetic field pulses will induce electric currents in the stimulated tissue, it is unclear whether the observed effects are due to the magnetic or electric component of the stimulation. Recently, it has been shown that PEMFs stimulate the formation of ROS (reactive oxygen species) in human cell cultures by a mechanism that requires cryptochrome, a putative magnetosensor. Here we show by qPCR analysis of ROS-regulated gene expression that simply removing cell cultures from the Earth’s geomagnetic field by placing them in a Low-Level Field condition induces similar effects on ROS signaling as does exposure of cells to PEMF. This effect can be explained by the so-called Radical Pair mechanism, which provides a quantum physical means by which the rates and product yields (e.g. ROS) of biochemical redox reactions may be modulated by magnetic fields. Since transient cancelling of the Earth’s magnetic field can in principle be achieved by PEMF exposure, we propose that the therapeutic effects of PEMFs may be explained by the ensuing modulation of ROS synthesis. Our results could lead to significant improvements in the design and therapeutic applications of PEMF devices.

The Regenerative Effect of Trans-spinal Magnetic Stimulation After Spinal Cord Injury: Mechanisms and Pathways Underlying the Effect

Spinal cord injury (SCI) leads to a loss of sensitive and motor functions. Currently, there is no therapeutic intervention offering a complete recovery. Here, we report that repetitive trans-spinal magnetic stimulation (rTSMS) can be a noninvasive SCI treatment that enhances tissue repair and functional recovery. Several techniques including immunohistochemical, behavioral, cells cultures, and proteomics have been performed. Moreover, different lesion paradigms, such as acute and chronic phase following SCI in wild-type and transgenic animals at different ages (juvenile, adult, and aged), have been used. We demonstrate that rTSMS modulates the lesion scar by decreasing fibrosis and inflammation and increases proliferation of spinal cord stem cells. Our results demonstrate also that rTSMS decreases demyelination, which contributes to axonal regrowth, neuronal survival, and locomotor recovery after SCI. This research provides evidence that rTSMS induces therapeutic effects in a preclinical rodent model and suggests possible translation to clinical application in humans.