Concurrent TMS-fMRI: Technical Challenges, Developments, and Overview of Previous Studies

rTMS-induced neuroimaging changes measured with structural and functional MRI in autism

Introduction

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by deficits in social communication, repetitive behaviors, and restricted interests. Despite increasing prevalence, effective therapeutic interventions remain limited. Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising non-invasive neuromodulation technique; however, its neural mechanisms and clinical efficacy in children with ASD require further investigation.

Methods

This study enrolled 14 children diagnosed with ASD to undergo a structured rTMS intervention. Neuroimaging data-including voxel-based morphometry (VBM) and resting-state functional connectivity (FC)-as well as behavioral assessments were collected before and after the intervention to evaluate changes in brain structure, function, and symptomatology.

Results

Post-intervention analyses revealed significant increases in gray matter volume (GMV) in the cerebellar Vermis, Caudate nucleus, and Postcentral gyrus. Additionally, enhanced functional connectivity was observed between the Fusiform gyrus, Temporal cortex, Frontal cortex, and Precuneus. Correlation analyses indicated that these neuroimaging changes were significantly associated with improvements in behavioral scores.

Discussion

These findings suggest that rTMS may exert therapeutic effects in children with ASD by modulating cerebellar development and cognitive control networks. The observed structural and functional brain changes support the potential utility of rTMS as a neuromodulatory intervention for ASD. Further studies with larger cohorts are needed to confirm these preliminary results and elucidate the mechanisms underlying rTMS-induced symptom improvement.

Precision neuroregulation combining liquid metal and magnetic stimulation

BACKGROUND

Electromagnetic field-based neuroregulation technology is a crucial technique for treating central nervous system and peripheral nervous system disorders. However, the use of invasive electrodes has unavoidable problems such as the risk of inflammation due to high hardness, electrical connections and the need for batteries. On the other hand, non-invasive magnetic stimulation has limitations such as centimeter-level focal areas and shallow stimulation depth.

METHODS

To enhance the precision and effectiveness of wireless magnetic stimulation, we employed a figure-8 magnetic stimulation coil (8-coil) to generate a magnetic field, combined with an injectable, highly conductive, and flexible liquid metal (LM) to produce a millimeter-scale focused electric field. A coaxial electric field measurement electrode was used to establish an agar phantom-based electric field measurement platform. The sciatic nerve of C57 mice was stimulated under acute anesthesia conditions, and electromyography (EMG) signals were collected to evaluate the enhancement of stimulation effects. Long-term safety was assessed through four weeks of implantation.

RESULTS

Theoretical analysis and finite element simulations demonstrated that the combination of LM and the 8-coil generated a millimeter-scale enhanced vector electric field within the tissue. Measured electric field distributions closely aligned with theoretical and simulation results. In the sciatic nerve experiments on mice, 1 µL of LM under a 0.45 T magnetic field significantly increased EMG signals and leg movement amplitude by approximately 500%. Long-term implantation under magnetic stimulation revealed no adverse effects.

CONCLUSIONS

This method utilizes focused electric fields to improve the precision and effectiveness of neuro-magnetic stimulation. It holds promise as a novel approach for precise stimulation. Preliminary evidence was provided for the safety of in vivo LM implantation under external magnetic fields.

Identification of Cortical Targets for Modulating Function Supported by the Human Hippocampal Network

Individualized transcranial magnetic stimulation (TMS) targeting using functional connectivity analysis of functional magnetic resonance imaging (fMRI) has been demonstrated to be advantageous in inducing neuroplasticity. However, how this approach can benefit modulating the episodic memory function supported by the hippocampal network remains elusive. We use the resting-state fMRI data from a large cohort to reveal tentative TMS targets at cortical regions within the hippocampal network. Functional MRI from 1,133 individuals in the Human Connectome Project was used to analyze the hippocampal network using seed-based functional connectivity. Using a weighted sum of time series at the cortex, we identified the average centroids of individualized targets at the medial prefrontal cortex (mPFC) and posterior parietal cortices (PPCs) at (-10, 49, 7) and (-40, -67, 30) in the left hemisphere, respectively. The mPFC and PPC coordinate at the right hemispheres are (11, 51, 6) and (48, -59, 24) in the right hemisphere, respectively. Centroids of the individualized functional connectivity at the mPFC and PPC were reproducible between sessions with separations in average about 2 and 4 mm, respectively. These separations were significantly smaller than the distance to average functional connectivity centroids (~10 mm) and atlas coordinate (~20 mm). These coordinates can be reliably identified (> 90% of individuals) using cortical "seedmaps." Our results suggest candidate TMS target coordinates to modulate the hippocampal function.

Neural circuits and therapeutic mechanisms of empathic pain

Empathy is the capacity to understand and share the experiences of others. This ability fosters connections between individuals, enriching the fabric of our shared world. One notable example is empathy for the pain of others. Such experiences facilitate the identification of potential dangers, both for oneself and for others. Neuroimaging studies have helped to pinpoint brain regions that modulate empathic pain. Recently, there has also been a surge in studies exploring the neural mechanisms of empathic pain in rodent models. Neuropsychiatric disorders such as autism, psychosis, and schizophrenia often exhibit empathy deficits. Targeting the modulation of empathic pain holds potential for alleviating core symptoms in these patients. Interestingly, empathy research may also benefit pain management, leading to new approaches for understanding the negative emotions associated with pain. This review summarizes recent advances in neuroimaging for the study of empathic pain, outlines the underlying neurocircuit mechanisms, describes therapeutic strategies, and explores promising avenues for future research. This article is part of the Special Issue on "Empathic Pain".

Field switching of microfabricated metamagnetic FeRh MRI contrast agents

In a step towards generating switchable MRI cellular labels, we demonstrate in-situ field switching of micron scale metamagnetic Iron-Rhodium (FeRh) thin film particles. A thin-film (200 nm) FeRh sample was fabricated and patterned into an array of progressively smaller squares with sizes ranging from 500 μm down to 1 μm. The large first order phase change from antiferromagnetic to ferromagnetic state was characterized using vibrating sample magnetometry, magnetic force microscopy, and MRI. Room temperature MRI experiments sensitive to the local magnetic field surrounding the particles demonstrated the low moment state (OFF MRI contrast) at 4.7T and high moment state (ON MRI contrast) at 11.7T for the array where sizes down to 2-3 μm were observed in MRI at 50 μm resolution. The expected temperature dependent MRI contrast change was seen at 4.7T, where 10 μm particles could be observed at 150 μm resolution in the ON state. A shielded MRI insert, used to temporarily increase or decrease the magnetic field up to 0.77T amplitude, was used to reversibly switch the particle array at constant temperature and blink the particles ON and OFF at 4.7T. This work demonstrates the MRI contrast switching potential for FeRh particles with biological cell dimensions, and the use of magnetic field pulses for reversible MRI label contrast control.

The potential of interleaved TMS-fMRI for linking stimulation-induced changes in task-related activity with behavioral modulations

The simultaneous combination of TMS with fMRI has emerged as a promising means to investigate the direct interaction between stimulation-induced changes at the behavioral and neural activity level. This enables the investigation of whole brain neurobehavioral interactions underlying cognitive disruption or facilitation. Yet to date, the literature on interleaved TMS-fMRI in cognitive neuroscience is sparse and neuromodulatory patterns of different TMS protocols are still poorly understood. Here, we synthesize interleaved TMS-fMRI studies on the relationship between direct stimulation-induced changes on task related neural activity and behavior. The following main findings are discussed. First, approximately half of the studies report a relationship between neural activity and behavioral changes as a marker for network excitation or inhibition. Secondly, task difficulty and stimulation timing are crucial factors that impact the interaction between neural activity changes and behavior. Third, stimulation-induced changes in remote, connected areas seem to be stronger associated with facilitation effects at the behavioral level. A better understanding of the relationship between stimulation-induced changes at the neural and behavioral level will increase the current understanding of the neuromodulatory potential of TMS at different levels and may help to develop more efficient stimulation protocols for basic and applied research.

Multimodal neuroimaging of hierarchical cognitive control

Cognitive control enables us to translate our knowledge into actions, allowing us to flexibly adjust our behavior, according to environmental contexts, our internal goals, and future plans. Multimodal neuroimaging and neurostimulation techniques have proven essential for advancing our understanding of how cognitive control emerges from the coordination of distributed neuronal activities in the brain. In this review, we examine the literature on multimodal studies of cognitive control. We explore how these studies provide converging evidence for a novel, multiplexed model of cognitive control, in which neural oscillations support different levels of control processing along a functionally hierarchical organization of distinct frontoparietal networks.

The Neurophysiological Effects of Theta Burst Stimulation as Measured by Electroencephalography: A Systematic Review

Theta burst stimulation (TBS) is a noninvasive brain stimulation technique that can modulate neural activity. The effect of TBS on regions beyond the motor cortex remains unclear. With increased interest in applying TBS to nonmotor regions for research and clinical purposes, these effects must be understood and characterized. We synthesized the electrophysiological effects of a single session of TBS, as indexed by electroencephalography (EEG) and concurrent transcranial magnetic stimulation and EEG, in nonclinical participants. We reviewed 79 studies that administered either continuous TBS or intermittent TBS protocols. Broadly, continuous TBS suppressed and intermittent TBS facilitated evoked response component amplitudes. Response to TBS as measured by spectral power and connectivity was much more variable. Variability increased in the presence of task stimuli. There was a large degree of heterogeneity in the research methodology across studies. Additionally, the effect of individual differences on TBS response has been insufficiently investigated. Future research investigating the effects of TBS as measured by EEG must consider methodological and individual factors that may affect TBS outcomes.

Transcranial Magnetic Stimulation Applications in the Study of Executive Functions: A Review

PURPOSE

Executive functions (EFs) are a set of advanced cognitive functions essential for human survival and behavioral regulation. Understanding neurophysiological mechanisms of EFs as well as exploring methods to enhance them are still challenging problems in cognitive neuroscience. In recent years, transcranial magnetic stimulation (TMS) has been widely used in the field of EF research and has made notable progress. This article aimed to discuss the impact of TMS technology on EF research from both basic and applied research perspectives.

METHODS

We searched for literature on TMS and EFs published in the last decade (2013-2023) and reviewed how TMS has been applied in the field of EF.

FINDINGS

We found that the combination of TMS with neuroimaging techniques was helpful in exploring the brain mechanisms of EFs and investigating the executive dysfunctions caused by other neuropsychiatric disorders. Moreover, TMS could be considered as one of the most important techniques to enhance EFs among patient populations, even healthy people, with high safety and credibility. Meanwhile, we discussed the application of TMS in the research of EFs and made suggestions for future research directions. We suggested that a multidisciplinary structure of methods such as epigenetics and endocrinology could be integrated with TMS for investigating deeper in EF domains, and a substantial number of high-quality clinical studies are required to further elucidate the effects of TMS on EFs.

CONCLUSIONS

TMS holds great promise for gaining insight into investigating the neural mechanisms of EFs and improving executive functions among different populations.

Engineering and Technological Advancements in Repetitive Transcranial Magnetic Stimulation (rTMS): A Five-Year Review

In the past five years, repetitive transcranial magnetic stimulation (rTMS) has evolved significantly, driven by advancements in device design, treatment protocols, software integration, and brain-computer interfaces (BCIs). This review evaluates how these innovations enhance the safety, efficacy, and accessibility of rTMS while identifying key challenges such as protocol standardization and ethical considerations. A structured review of peer-reviewed studies from 2019 to 2024 focused on technological and clinical advancements in rTMS, including AI-driven personalized treatments, portable devices, and integrated BCIs. AI algorithms have optimized patient-specific protocols, while portable devices have expanded access. Enhanced coil designs and BCI integration offer more precise and adaptive neuromodulation. However, challenges remain in standardizing protocols, addressing device complexity, and ensuring equitable access. While recent innovations improve rTMS's clinical utility, gaps in long-term efficacy and ethical concerns persist. Future research must prioritize standardization, accessibility, and robust ethical frameworks to ensure rTMS's sustainable impact.

Chronometric TMS-fMRI of personalized left dorsolateral prefrontal target reveals state-dependency of subgenual anterior cingulate cortex effects

Transcranial magnetic stimulation (TMS) applied to a left dorsolateral prefrontal cortex (DLPFC) area with a specific connectivity profile to the subgenual anterior cingulate cortex (sgACC) has emerged as a highly effective non-invasive treatment option for depression. However, antidepressant outcomes demonstrate significant variability among therapy plans and individuals. One overlooked contributing factor is the individual brain state at the time of treatment. In this study we used interleaved TMS-fMRI to investigate the influence of brain state on acute TMS effects, both locally and remotely. TMS was performed during rest and during different phases of cognitive task processing. Twenty healthy participants were included in this study. In the first session, imaging data for TMS targeting were acquired, allowing for identification of individualized targets in the left DLPFC based on highest anti-correlation with the sgACC. The second session involved chronometric interleaved TMS-fMRI measurements, with 10 Hz triplets of TMS administered during rest and at distinct timings during an N-back task. Consistent with prior findings, interleaved TMS-fMRI revealed significant BOLD activation changes in the targeted network. The precise timing of TMS relative to the cognitive states during the task demonstrated distinct BOLD response in clinically relevant brain regions, including the sgACC. Employing a standardized timing approach for TMS using a task revealed more consistent modulation of the sgACC at the group level compared to stimulation during rest. In conclusion, our findings strongly suggest that acute local and remote effects of TMS are influenced by brain state during stimulation. This study establishes a basis for considering brain state as a significant factor in designing treatment protocols, possibly improving TMS treatment outcomes.

Dose-Dependent Target Engagement of a Clinical Intermittent Theta Burst Stimulation Protocol: An Interleaved Transcranial Magnetic Stimulation-Functional Magnetic Resonance Imaging Study in Healthy People

BACKGROUND

Intermittent theta burst stimulation (iTBS) of the dorsolateral prefrontal cortex (DLPFC) is widely applied as a therapeutic intervention in mental health; however, the understanding of its mechanisms is still incomplete. Prior magnetic resonance imaging (MRI) studies have mainly used offline iTBS or short sequences in concurrent transcranial magnetic stimulation (TMS)-functional MRI (fMRI). This study investigated a full 600-stimuli iTBS protocol using interleaved TMS-fMRI in comparison with 2 control conditions in healthy subjects.

METHODS

In a crossover design, 18 participants underwent 3 sessions of interleaved iTBS-fMRI: 1) the left DLPFC at 40% resting motor threshold (rMT) intensity, 2) the left DLPFC at 80% rMT intensity, and 3) the left primary motor cortex (M1) at 80% rMT intensity. We compared immediate blood oxygen level-dependent (BOLD) responses during interleaved iTBS-fMRI across these conditions including correlations between individual fMRI BOLD activation and iTBS-induced electric field strength at the target sites.

RESULTS

Whole-brain analysis showed increased activation in several regions following iTBS. Specifically, the left DLPFC, as well as the bilateral M1, anterior cingulate cortex, and insula, showed increased activation during 80% rMT left DLPFC stimulation. Increased BOLD activity in the left DLPFC was observed with neither 40% rMT left DLPFC stimulation nor left M1 80% rMT iTBS, whereas activation in other regions was found to overlap between conditions. Of note, BOLD activation and electric field intensities were only correlated for M1 stimulation and not for the DLPFC conditions.

CONCLUSIONS

This interleaved TMS-fMRI study showed dosage- and target-specific BOLD activation during a 600-stimuli iTBS protocol in healthy individuals. Future studies may use our approach for investigating target engagement in clinical samples.

Modeling the stress and forces on multi-channel TMS coil arrays in high-field MRI scanners

Transcranial magnetic stimulation (TMS) is a non-invasive method for stimulating the cortex. Concurrent functional magnetic resonance imaging can show changes in TMS-induced activity in the whole brain, with the potential to inform brain function research and to guide the development of TMS therapy. However, the interaction of the strong current pulses in the TMS coil in the static main magnetic field of the MRI produces high Lorentz forces, which may damage the coil enclosure and compromise the patient's safety. We studied the time-dependent mechanical behavior and durability of two multi-locus TMS (mTMS) coil arrays inside a high-field MRI bore with finite element modeling. In addition, coil arrays were built and tested based on the simulation results. We found that the current pulses produce shock waves and time-dependent stress distribution in the coil plates. The intensity and location of the maximum stress depend on the current waveform, the coil combination, and the transducer orientation relative to the MRI magnetic field. We found that 30% glass-fiber-filled polyamide is the most durable material out of the six options studied. In addition, novel insights for more durable TMS coil designs were obtained. Our study contributes to a comprehensive understanding of the underlying mechanisms responsible for the structural failure of mTMS coil arrays during stimulation within high static magnetic fields. This knowledge is essential for developing mechanically stable and safe mTMS-MRI transducers.

Instantaneous effects of prefrontal transcranial magnetic stimulation on brain oxygenation: A systematic review

This systematic review investigates how prefrontal transcranial magnetic stimulation (TMS) immediately influences neuronal excitability based on oxygenation changes measured by functional magnetic resonance imaging (fMRI) or functional near-infrared spectroscopy (fNIRS). A thorough understanding of TMS-induced excitability changes may enable clinicians to adjust TMS parameters and optimize treatment plans proactively. Five databases were searched for human studies evaluating brain excitability using concurrent TMS/fMRI or TMS/fNIRS. Thirty-seven studies (13 concurrent TMS/fNIRS studies, 24 concurrent TMS/fMRI studies) were included in a qualitative synthesis. Despite methodological inconsistencies, a distinct pattern of activated nodes in the frontoparietal central executive network, the cingulo-opercular salience network, and the default-mode network emerged. The activated nodes included the prefrontal cortex (particularly dorsolateral prefrontal cortex), insula cortex, striatal regions (especially caudate, putamen), anterior cingulate cortex, and thalamus. High-frequency repetitive TMS most consistently induced expected facilitatory effects in these brain regions. However, varied stimulation parameters (e.g., intensity, coil orientation, target sites) and the inter- and intra-individual variability of brain state contribute to the observed heterogeneity of target excitability and co-activated regions. Given the considerable methodological and individual variability across the limited evidence, conclusions should be drawn with caution.

Neural response during prefrontal theta burst stimulation: Interleaved TMS-fMRI of full iTBS protocols

BACKGROUND

Left prefrontal intermittent theta-burst stimulation (iTBS) has emerged as a safe and effective transcranial magnetic stimulation (TMS) treatment protocol in depression. Though network effects after iTBS have been widely studied, the deeper mechanistic understanding of target engagement is still at its beginning. Here, we investigate the feasibility of a novel integrated TMS-fMRI setup and accelerated echo planar imaging protocol to directly observe the immediate effects of full iTBS treatment sessions.

OBJECTIVE/HYPOTHESIS

In our effort to explore interleaved iTBS-fMRI feasibility, we hypothesize that TMS will induce acute BOLD signal changes in both the stimulated area and interconnected neural regions.

METHODS

Concurrent TMS-fMRI with full sessions of neuronavigated iTBS (i.e. 600 pulses) of the left dorsolateral prefrontal cortex (DLPFC) was investigated in 18 healthy participants. In addition, we conducted four TMS-fMRI sessions in a single patient on long-term maintenance iTBS for bipolar depression to test the transfer to clinical cases.

RESULTS

Concurrent TMS-fMRI was feasible for iTBS sequences with 600 pulses. During interleaved iTBS-fMRI, an increase of the BOLD signal was observed in a network including bilateral DLPFC regions. In the clinical case, a reduced BOLD response was found in the left DLPFC and the subgenual anterior cingulate cortex, with high variability across individual sessions.

CONCLUSIONS

Full iTBS sessions as applied for the treatment of depressive disorders can be established in the interleaved iTBS-fMRI paradigm. In the future, this experimental approach could be valuable in clinical samples, for demonstrating target engagement by iTBS protocols and investigating their mechanisms of therapeutic action.

One session of repetitive transcranial magnetic stimulation induces mild and transient analgesic effects among female individuals with painful temporomandibular disorders

OBJECTIVE

Temporomandibular disorders (TMD) are characterised by chronic pain and dysfunction in the jaw joint and masticatory muscles. Repetitive transcranial magnetic stimulation (rTMS) has emerged as a potential non-invasive treatment for chronic pain; however, its effectiveness in individuals with TMD has not been thoroughly investigated. This study aimed to evaluate the immediate and sustained (over seven consecutive days) effects of a single session of active rTMS compared to sham stimulation on pain intensity and pain unpleasantness in individuals with TMD.

METHODS

A randomised, double-blind, sham-controlled trial enrolled 41 female participants with chronic TMD. Pain intensity and pain unpleasantness were assessed immediately pre- and post-intervention, as well as twice daily for 21 days using electronic diaries. Secondary outcomes included pain interference, sleep quality, positive and negative affect and pain catastrophizing. Adverse effects were monitored. Repeated measures ANOVA and multilevel modelling regression analyses were employed for data analysis.

RESULT

Active rTMS demonstrated a significant immediate mild reduction in pain intensity and pain unpleasantness compared to sham stimulation. However, these effects were not sustained over the 7-day post-intervention period. No significant differences were observed between interventions for pain interference, sleep quality and negative affect. A minority of participants reported minor and transient side effects, including headaches and fatigue.

CONCLUSION

A single session of active rTMS was safe and led to immediate mild analgesic effects in individuals with TMD compared to sham stimulation. However, no significant differences were observed between interventions over the 7-day post-intervention period. Based on this study, rTMS stimulation appears to be a promising safe approach to be tested in TMD patients with longer stimulation protocols.

Acoustic noise generated by TMS in typical environment and inside an MRI scanner

BACKGROUND

The operation of a transcranial magnetic stimulation (TMS) coil produces high-intensity impulse sounds. In TMS, a magnetic field is generated by a short-duration pulse in the range of thousands of amperes in the TMS coil. When placed in a strong magnetic field, such as inside a magnetic resonance imaging (MRI) bore, the interaction of the magnetic field and the current in the TMS coil can cause strong forces on the coil casing. The strengths of these forces depend on the coil orientation in the main magnetic field (B0). Part of the energy in this process is dissipated in the form of acoustic noise.

OBJECTIVE

Our objective was to measure the sound pressure levels (SPL) of TMS "click" sounds created by commercial TMS stimulators and coils in a typical environment and inside a 3-T MRI scanner and advance the knowledge of the acoustic behaviour of TMS to safely conduct TMS alone as well as concurrently with functional MRI (fMRI).

METHODS

We report SPL measurements of two commercial MRI-compatible TMS systems in the 3-T B0 field of an MRI scanner and in the earth's magnetic field. Also, we present the acoustic noise measurements of four commercial TMS stimulators and three different TMS coils in a typical operational environment without the B0 field.

RESULTS

The maximum peak SPL measured was 158 dB(C) inside the 3-T MRI scanner. Outside the scanner, the maximum peak SPL was 117 dB(C). Inside the scanner, the peak SPL increased by 21-45 dB(C) depending on the stimulator and the orientation of the electric field relative to the B field.

CONCLUSIONS

Hearing protection is obligatory during concurrent TMS-fMRI experiments and highly recommended during any TMS experiment. The manufacturing of quieter TMS systems is encouraged to reduce the risk of hearing damage and other unwanted effects.

Assessing cortical excitability with electroencephalography: A pilot study with EEG-iTBS

BACKGROUND

Cortical excitability measures neural reactivity to stimuli, usually delivered via Transcranial Magnetic Stimulation (TMS). Excitation/inhibition balance (E/I) is the ongoing equilibrium between excitatory and inhibitory activity of neural circuits. According to some studies, E/I could be estimated in-vivo and non-invasively through the modeling of electroencephalography (EEG) signals and termed 'intrinsic excitability' measures. Several measures have been proposed (phase consistency in the gamma band, sample entropy, exponent of the power spectral density 1/f curve, E/I index extracted from detrend fluctuation analysis, and alpha power). Intermittent theta burst stimulation (iTBS) of the primary motor cortex (M1) is a non-invasive neuromodulation technique allowing controlled and focal enhancement of TMS cortical excitability and E/I of the stimulated hemisphere.

OBJECTIVE

Investigating to what extent E/I estimates scale with TMS excitability and how they relate to each other.

METHODS

M1 excitability (TMS) and several E/I estimates extracted from resting state EEG recordings were assessed before and after iTBS in a cohort of healthy subjects.

RESULTS

Enhancement of TMS M1 excitability, as measured through motor-evoked potentials (MEPs), and phase consistency of the cortex in high gamma band correlated with each other. Other measures of E/I showed some expected results, but no correlation with TMS excitability measures or strong consistency with each other.

CONCLUSIONS

EEG E/I estimates offer an intriguing opportunity to map cortical excitability non-invasively, with high spatio-temporal resolution and with a stimulus independent approach. While different EEG E/I estimates may reflect the activity of diverse excitatory-inhibitory circuits, spatial phase synchrony in the gamma band is the measure that best captures excitability changes in the primary motor cortex.

TMS disruption of the lateral prefrontal cortex increases neural activity in the default mode network when naming facial expressions

Recognizing facial expressions is dependent on multiple brain networks specialized for different cognitive functions. In the current study, participants (N = 20) were scanned using functional magnetic resonance imaging (fMRI), while they performed a covert facial expression naming task. Immediately prior to scanning thetaburst transcranial magnetic stimulation (TMS) was delivered over the right lateral prefrontal cortex (PFC), or the vertex control site. A group whole-brain analysis revealed that TMS induced opposite effects in the neural responses across different brain networks. Stimulation of the right PFC (compared to stimulation of the vertex) decreased neural activity in the left lateral PFC but increased neural activity in three nodes of the default mode network (DMN): the right superior frontal gyrus, right angular gyrus and the bilateral middle cingulate gyrus. A region of interest analysis showed that TMS delivered over the right PFC reduced neural activity across all functionally localised face areas (including in the PFC) compared to TMS delivered over the vertex. These results suggest that visually recognizing facial expressions is dependent on the dynamic interaction of the face-processing network and the DMN. Our study also demonstrates the utility of combined TMS/fMRI studies for revealing the dynamic interactions between different functional brain networks.

Advancements in Transcranial Magnetic Stimulation Research and the Path to Precision

Transcranial magnetic stimulation (TMS) has become increasingly popular in clinical practice in recent years, and there have been significant advances in the principles and stimulation modes of TMS. With the development of multi-mode and precise stimulation technology, it is crucial to have a comprehensive understanding of TMS. The neuroregulatory effects of TMS can vary depending on the specific mode of stimulation, highlighting the importance of exploring these effects through multimodal application. Additionally, the use of precise TMS therapy can help enhance our understanding of the neural mechanisms underlying these effects, providing us with a more comprehensive perspective. This article aims to review the mechanism of action, stimulation mode, multimodal application, and precision of TMS.

A novel whole-head RF coil design tailored for concurrent multichannel brain stimulation and imaging at 3T

PURPOSE

Multichannel Transcranial Magnetic Stimulation (mTMS) [1] is a novel non-invasive brain stimulation technique allowing multiple sites to be stimulated simultaneously or sequentially under electronic control without movement of the coils. To enable simultaneous mTMS and MR imaging, we have designed and constructed a whole-head 28-channel receive-only RF coil at 3T.

METHODS

A helmet-shaped structure was designed considering a specific layout for a mTMS system with holes for positioning the TMS units next to the scalp. Diameter of the TMS units defined the diameter of RF loops. The placement of the preamplifiers was designed to minimize possible interactions and to allow straightforward positioning of the mTMS units around the RF coil. Interactions between TMS-MRI were analyzed for the whole-head system extending the results presented in previous publications [2]. Both SNR- and g-factors maps were obtained to compare the imaging performance of the coil with commercial head coils.

RESULTS

Sensitivity losses for the RF elements containing TMS units show a well-defined spatial pattern. Simulations indicate that the losses are predominantly caused by eddy currents on the coil wire windings. The average SNR performance of the TMSMR 28-channel coil is about 66% and 86% of the SNR of the 32/20-channel head coil respectively. The g-factor values of the TMSMR 28-channel coil are similar to the 32-channel coil and significantly better than the 20-channel coil.

CONCLUSION

We present the TMSMR 28-channel coil, a head RF coil array to be integrated with a multichannel 3-axisTMS coil system, a novel tool that will enable causal mapping of human brain function.

The multimodal Munich Clinical Deep Phenotyping study to bridge the translational gap in severe mental illness treatment research

Introduction

Treatment of severe mental illness (SMI) symptoms, especially negative symptoms and cognitive dysfunction in schizophrenia, remains a major unmet need. There is good evidence that SMIs have a strong genetic background and are characterized by multiple biological alterations, including disturbed brain circuits and connectivity, dysregulated neuronal excitation-inhibition, disturbed dopaminergic and glutamatergic pathways, and partially dysregulated inflammatory processes. The ways in which the dysregulated signaling pathways are interconnected remains largely unknown, in part because well-characterized clinical studies on comprehensive biomaterial are lacking. Furthermore, the development of drugs to treat SMIs such as schizophrenia is limited by the use of operationalized symptom-based clusters for diagnosis.

Methods

In line with the Research Domain Criteria initiative, the Clinical Deep Phenotyping (CDP) study is using a multimodal approach to reveal the neurobiological underpinnings of clinically relevant schizophrenia subgroups by performing broad transdiagnostic clinical characterization with standardized neurocognitive assessments, multimodal neuroimaging, electrophysiological assessments, retinal investigations, and omics-based analyzes of blood and cerebrospinal fluid. Moreover, to bridge the translational gap in biological psychiatry the study includes in vitro investigations on human-induced pluripotent stem cells, which are available from a subset of participants.

Results

Here, we report on the feasibility of this multimodal approach, which has been successfully initiated in the first participants in the CDP cohort; to date, the cohort comprises over 194 individuals with SMI and 187 age and gender matched healthy controls. In addition, we describe the applied research modalities and study objectives.

Discussion

The identification of cross-diagnostic and diagnosis-specific biotype-informed subgroups of patients and the translational dissection of those subgroups may help to pave the way toward precision medicine with artificial intelligence-supported tailored interventions and treatment. This aim is particularly important in psychiatry, a field where innovation is urgently needed because specific symptom domains, such as negative symptoms and cognitive dysfunction, and treatment-resistant symptoms in general are still difficult to treat.

Design of coil holder for the improved maneuvering in concurrent TMS-MRI

BACKGROUND

Concurrent transcranial magnetic stimulation (TMS) and magnetic resonance imaging (MRI) is time-consuming because of the limited space in the MRI bore and the sophisticated placement and orientation of the TMS coil to elicit the desired brain activities and behaviors.

OBJECTIVE

We developed a TMS coil holder capable of quick adjustment of the TMS coil position and orientation. The holder can also hold an MRI receiver coil array.

METHODS

A holder with one controlling knob, two omni-direction rotation joints, and two in-plane rotation joints was developed.

RESULTS

Different TMS coil positions and orientations can be arranged and fixed in seconds. The holder can also accommodate two TMS coils to allow for multi-coil TMS-MRI.

CONCLUSION

Our development significantly improves the workflow of the concurrent TMS-MRI in new neuroscience studies and clinical applications.

A guide for concurrent TMS-fMRI to investigate functional brain networks

Transcranial Magnetic Stimulation (TMS) allows for the direct activation of neurons in the human neocortex and has proven to be fundamental for causal hypothesis testing in cognitive neuroscience. By administering TMS concurrently with functional Magnetic Resonance Imaging (fMRI), the effect of cortical TMS on activity in distant cortical and subcortical structures can be quantified by varying the levels of TMS output intensity. However, TMS generates significant fluctuations in the fMRI time series, and their complex interaction warrants caution before interpreting findings. We present the methodological challenges of concurrent TMS-fMRI and a guide to minimize induced artifacts in experimental design and post-processing. Our study targeted two frontal-striatal circuits: primary motor cortex (M1) projections to the putamen and lateral prefrontal cortex (PFC) projections to the caudate in healthy human participants. We found that TMS parametrically increased the BOLD signal in the targeted region and subcortical projections as a function of stimulation intensity. Together, this work provides practical steps to overcome common challenges with concurrent TMS-fMRI and demonstrates how TMS-fMRI can be used to investigate functional brain networks.

Advances in neuroimaging studies of alcohol use disorder (AUD)

Alcohol use disorder (AUD) is a worldwide problem and the most common substance use disorder. Chronic alcohol consumption may have negative effects on the body, the mind, the family, and even society. With the progress of current neuroimaging methods, an increasing number of imaging techniques are being used to objectively detect brain impairment induced by alcoholism and serve a vital role in the diagnosis, prognosis, and treatment assessment of AUD. This article organizes and analyzes the research on alcohol dependence concerning the main noninvasive neuroimaging methods, structural magnetic resonance imaging, functional magnetic resonance imaging, and electroencephalography, as well as the most common noninvasive brain stimulation - transcranial magnetic stimulation, and intersperses the article with joint intra- and intergroup studies, providing an outlook on future research directions.

Brain Perfusion Alterations Induced by Standalone and Combined Non-Invasive Brain Stimulation over the Dorsolateral Prefrontal Cortex

Non-invasive brain stimulation (NIBS) interventions are promising for the treatment of psychiatric disorders. Notwithstanding, the NIBS mechanisms of action over the dorsolateral prefrontal cortex (DLPFC), a hub that modulates affective and cognitive processes, have not been completely mapped. We aimed to investigate regional cerebral blood flow (rCBF) changes over the DLPFC and the subgenual anterior cingulate cortex (sgACC) of different NIBS protocols using Single-Photon Emission Computed Tomography (SPECT). A factorial, within-subjects, double-blinded study was performed. Twenty-three healthy subjects randomly underwent four sessions of NIBS applied once a week: transcranial direct current stimulation (tDCS), intermittent theta-burst stimulation (iTBS), combined tDCS + iTBS and placebo. The radiotracer 99m-Technetium-ethylene-cysteine-dimer was injected intravenously during the NIBS session, and SPECT neuroimages were acquired after the session. Results revealed that the combination of tDCS + iTBS increased right sgACC rCBF. Cathodal and anodal tDCS increased and decreased DLPFC rCBF, respectively, while iTBS showed no significant changes compared to the placebo. Our findings suggest that the combined protocol might optimize the activity in the right sgACC and encourage future trials with neuropsychiatric populations. Moreover, mechanistic studies to investigate the effects of tDCS and iTBS over the DLPFC are required.