Cortical-subcortical structural connections support transcranial magnetic stimulation engagement of the amygdala

Low-intensity transcranial focused ultrasound amygdala neuromodulation: a double-blind sham-controlled target engagement study and unblinded single-arm clinical trial

Mood, anxiety, and trauma-related disorders (MATRDs) are highly prevalent and comorbid. A sizable number of patients do not respond to first-line treatments. Non-invasive neuromodulation is a second-line treatment approach, but current methods rely on cortical targets to indirectly modulate subcortical structures, e.g., the amygdala, implicated in MATRDs. Low-intensity transcranial focused ultrasound (tFUS) is a non-invasive technique for direct subcortical neuromodulation, but its safety, feasibility, and promise as a potential treatment is largely unknown. In a target engagement study, magnetic resonance imaging (MRI)-guided tFUS to the left amygdala was administered during functional MRI (tFUS/fMRI) to test for acute modulation of blood oxygenation level dependent (BOLD) signal in a double-blind, within-subject, sham-controlled design in patients with MATRDs (N = 29) and healthy comparison subjects (N = 23). In an unblinded treatment trial, the same patients then underwent 3-week daily (15 sessions) MRI-guided repetitive tFUS (rtFUS) to the left amygdala to examine safety, feasibility, symptom change, and change in amygdala reactivity to emotional faces. Active vs. sham tFUS/fMRI reduced, on average, left amygdala BOLD signal and produced patient-related differences in hippocampal and insular responses. rtFUS was well-tolerated with no serious adverse events. There were significant reductions on the primary outcome (Mood and Anxiety Symptom Questionnaire General Distress subscale; p = 0.001, Cohen's d = 0.77), secondary outcomes (Cohen's d of 0.43-1.50), and amygdala activation to emotional stimuli. Findings provide initial evidence of tFUS capability to modulate amygdala function, rtFUS safety and feasibility in MATRDs, and motivate double-blind randomized controlled trials to examine efficacy.ClinicalTrials.gov registration: NCT05228964.

Transcranial Magnetic Stimulation-Induced Plasticity Improving Cognitive Control in Obsessive-Compulsive Disorder, Part II: Task-Based Neural Predictors of Treatment Response

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) has the potential to increase the clinical effect of exposure with response prevention psychotherapy for obsessive-compulsive disorder (OCD). We investigated the use of task-based functional magnetic resonance imaging for predicting clinical outcomes to different rTMS protocols combined with exposure with response prevention in OCD.

METHODS

Sixty-one adults with OCD underwent rTMS and exposure with response prevention and were randomized to different high-frequency rTMS conditions: left dorsolateral prefrontal cortex (n = 19), left presupplementary motor area (n = 23), and control stimulation at the vertex at low intensity (n = 19). The Tower of London task and stop signal task were used to assess pretreatment activation during planning and inhibitory control, respectively. We adopted a Bayesian region-based approach to test whether clinical improvement can be predicted by task-based functional magnetic resonance imaging-derived measures of task-related brain activation or functional connectivity between task-relevant regions and the bilateral amygdala.

RESULTS

For the vertex group, but not the dorsolateral prefrontal cortex/presupplementary motor area rTMS conditions, higher activation in several task-relevant regions during planning and response inhibition and lower error-related activation corresponded with better short-term clinical improvement. Lower precuneus activation with increased planning taskload was correlated with symptom reduction in the dorsolateral prefrontal cortex group. In the presupplementary motor area group, higher error-related activation and lower inhibition-related insular-amygdalar connectivity were associated with symptom reduction.

CONCLUSIONS

Pretreatment task-based functional magnetic resonance imaging-derived measures of activation and connectivity during planning and inhibition-related processes are associated with clinical response for specific rTMS conditions in OCD. Future placebo-controlled trials with larger sample sizes should combine clinical information and neural correlates to improve prediction of clinical outcome.

Connectional axis of individual functional variability: Patterns, structural correlates, and relevance for development and cognition

The human cerebral cortex exhibits intricate interareal functional synchronization at the macroscale, with substantial individual variability in these functional connections. However, the spatial organization of functional connectivity (FC) variability across the human connectome edges and its significance in cognitive development remain unclear. Here, we identified a connectional axis in the edge-level FC variability. The variability declined continuously along this axis from within-network to between-network connections and from the edges linking association networks to those linking the sensorimotor and association networks. This connectional axis of functional variability is associated with spatial pattern of structural connectivity variability. Moreover, the connectional variability axis evolves in youth with an flatter axis slope. We also observed that the slope of the connectional variability axis was positively related to the performance in the higher-order cognition. Together, our results reveal a connectional axis in functional variability that is linked with structural connectome variability, refines during development, and is relevant to cognition.

Quantifying and reporting the precision of transcranial magnetic stimulation targeting

The precise positioning of the transcranial magnetic stimulation (TMS) coil on a person's head is crucial for the efficacy and reliability of the delivered stimulation protocol. Sophisticated techniques have been developed to define subject-specific stimulation targets, and advancements in the use of MRI-guided neuronavigation allows for real-time monitoring of the coil location during the TMS session. However, there is a need for TMS users to objectively quantify and report the accuracy of their targeting. Here, we share our technique (open-source scripts) that extracts the location of each TMS pulse delivered in a session from an MRI-guided neuronavigation system and outputs measures of targeting precision. Such measures include the variance in coil location over the duration of a session, detection of 'off-target' pulses, and the distance error relative to the intended cortical target. Reporting these metrics in publications may aid in the replicability of methodology and reproducibility of results of TMS research and clinical treatments. Furthermore, these measures can be used in training TMS operators. We encourage others to adapt our technique to their system(s) and specific needs and to report their targeting precision.

Effect of intermittent theta burst stimulation combined with acoustic startle priming motor training on upper limb motor function and neural plasticity in stroke individuals: study protocol for a randomised controlled proof-of-concept trial

INTRODUCTION

Stroke is a major cause of acquired disability globally, yet the neural mechanisms driving motor recovery post-stroke remain elusive. Recent research has underscored the growing significance of subcortical pathways in neural plasticity and motor control. Among these, the cortico-reticulospinal tract (CRST) has gained attention in rehabilitation due to its unique ascending and descending structural features as well as its cellular properties which position it as an excellent candidate to compensate for inadequate motor control post-stroke. However, the optimal strategies to harness the CRST for motor recovery remain unknown. Non-invasive modulation of the CRST presents a promising though challenging, therapeutic opportunity. Acoustic startle priming (ASP) training and intermittent theta burst stimulation (iTBS) are emerging as potential methods to regulate CRST function. This study aims to investigate the feasibility of segmentally modulating the cortico-reticular and reticulospinal tracts through ASP and iTBS while evaluating the resulting therapeutic effects.

METHODS AND ANALYSIS

This is a randomised, blinded interventional trial with three parallel groups. A total of 36 eligible participants will be randomly assigned to one of three groups: (1) iTBS+ASP group, (2) iTBS+non-ASP group, (3) sham iTBS+ASP group. The trial comprises four phases: baseline assessment, post-first intervention assessment, assessment after 3 weeks of intervention and a 4-week follow-up. The primary outcomes are the changes in the Fugl-Meyer Assessment-Upper Extremity and Modified Ashworth Scale after the 3-week intervention. Secondary outcomes include neurophysiological metrics and neuroimaging results from diffusion tensor imaging and resting-state functional MRI.

ETHICS AND DISSEMINATION

The trial is registered with the Chinese Clinical Trial Registry (Registration No. ChiCTR2400085220) and Medical Ethics Committee of Tongji Hospital, affiliated with Tongji Medical College, Huazhong University of Science and Technology (Registration No.TJ-IRB20231109). It will be conducted in the Departments of Rehabilitation Medicine and Radiology at Tongji Hospital in Wuhan, China. The findings will be disseminated through peer-reviewed journal publications and presentations at scientific conferences.

TRIAL REGISTRATION NUMBER

ChiCTR2400085220.

Connectional axis of individual functional variability: Patterns, structural correlates, and relevance for development and cognition

The human cerebral cortex exhibits intricate interareal functional synchronization at the macroscale, with substantial individual variability in these functional connections. However, the spatial organization of functional connectivity (FC) variability across the human connectome edges and its significance in cognitive development remain unclear. Here, we identified a connectional axis in the edge-level FC variability. The variability declined continuously along this axis from within-network to between-network connections, and from the edges linking association networks to those linking the sensorimotor and association networks. This connectional axis of functional variability is associated with spatial pattern of structural connectivity variability. Moreover, the connectional variability axis evolves in youth with an increasing flatter axis slope. We also observed that the slope of connectional variability axis was positively related to the performance in the higher-order cognition. Together, our results reveal a connectional axis in functional variability that is linked with structural connectome variability, refines during development, and is relevant to cognition.

Transcranial Direct Current Stimulation Improves Paranoia and Social Functioning in Schizophrenia: A Randomized Clinical Trial

BACKGROUND

Innovative treatments for paranoia, which significantly impairs social functioning in schizophrenia spectrum disorders (SSDs), are urgently needed. The pathophysiology of paranoia implicates the amygdala-prefrontal cortex (PFC) circuits; thus, in this study, we systematically investigated whether transcranial direct current stimulation (tDCS) to the ventrolateral PFC can attenuate paranoia and improve social functioning in SSDs.

METHODS

A double-blind, within-subjects, crossover design was used to compare active versus sham tDCS effects in 50 participants with SSDs (ClinicalTrials.gov identifier: NCT05746494). Participants completed 2 stimulation visits, each including 2 tDCS sessions about 1 week apart, with active (2 mA for 20 minutes) and sham conditions counterbalanced across the 2 visits. Alongside laboratory-based measurements of state paranoia and its associated social cognitive biases, ecological momentary assessment (EMA) was used. This involved daily evaluations of paranoia and social functioning administered 3 times per day for 7 days during each EMA period (EMA-baseline, EMA-active, EMA-sham).

RESULTS

For laboratory-based assessments, participants showed greater reductions in state paranoia and improvements in paranoia-related social cognitive biases after active stimulation compared with sham, including lower self-reported hostility and hostile attributions in ambiguous situations post active versus post sham. Similarly, in the EMA-active period, participants had lower daily paranoia than in the EMA-sham period and higher social interaction motivation with better attitudes compared with baseline and the EMA-sham period.

CONCLUSIONS

Extending our pilot study, the current findings further supported the efficacy of tDCS in mitigating paranoia and enhancing social functioning in patients with SSDs. This work sheds light on the neuropathology of paranoia and identifies a promising avenue for future large-scale interventions.

Intermittent theta burst stimulation of the left dorsolateral prefrontal cortex has no additional effect on the efficacy of virtual reality exposure therapy for acrophobia. A randomized double-blind placebo-controlled study

Anxiety disorders are among the most common mental disorders. Treatment guidelines recommend pharmacotherapy and cognitive behavioral therapy as standard treatment. Although cognitive behavioral therapy is an effective therapeutic approach, not all patients benefit sufficiently from it. In recent years, non-invasive brain stimulation techniques, such as transcranial magnetic stimulation, have been investigated as promising adjuncts in the treatment of affective disorders. The aim of this study is to investigate whether a combination of intermittent theta burst stimulation (iTBS) and virtual reality exposure therapy leads to a significantly greater reduction in acrophobia than virtual reality exposure with sham stimulation. In this randomized double-blind placebo-controlled study, 43 participants with acrophobia received verum or sham iTBS over the left dorsolateral prefrontal cortex prior to two sessions of virtual reality exposure therapy. Stimulation of the left dorsolateral prefrontal cortex with iTBS was motivated by an experimental study showing a positive effect on extinction memory retention. Acrophobic symptoms were assessed using questionnaires and two behavioral approach tasks one week before, after treatment and six months after the second diagnostic session. The results showed that two sessions of virtual reality exposure therapy led to a significant reduction in acrophobic symptoms, with an overall remission rate of 79 %. However, there was no additional effect of iTBS of the left dorsolateral prefrontal cortex on the therapeutic effects. Further research is needed to determine how exactly a combination of transcranial magnetic stimulation and exposure therapy should be designed to enhance efficacy.

Targeting VMPFC-amygdala circuit with TMS in substance use disorder: A mechanistic framework

The ventromedial prefrontal cortex (VMPFC), located along the medial aspect of the frontal area, plays a critical role in regulating arousal/emotions. Its intricate connections with subcortical structures, including the striatum and amygdala, highlight the VMPFC's importance in the neurocircuitry of addiction. Due to these features, the VMPFC is considered a promising target for transcranial magnetic stimulation (TMS) in substance use disorders (SUD). By the end of 2023, all 21 studies targeting VMPFC for SUD used anatomical landmarks (e.g., Fp1/Fp2 in the EEG system) to define coil location with a fixed orientation. Nevertheless, one-size-fits-all TMS over VMPFC has yielded variable outcomes. Here, we suggested a pipeline based on a tailored TMS targeting framework aimed at optimally modulating the VMPFC-amygdala circuit on an individual basis. We collected MRI data from 60 participants with methamphetamine use disorders (MUDs). We examined the variability in TMS target location based on task-based functional connectivity between VMPFC and amygdala using psychophysiological interaction (PPI) analysis. Electric fields (EF) were calculated for fixed vs. optimized location (Fp1/Fp2 vs. individualized maximal PPI), orientation (AF7/AF8 vs. optimized algorithm) and intensity (constant vs. adjusted) to maximize target engagement. In our pipeline, the left medial amygdala, identified as the brain region with the highest (0.31 ± 0.29) fMRI drug cue reactivity, was selected as the subcortical seed region. The voxel with the most positive amygdala-VMPFC PPI connectivity in each participant was considered the individualized TMS target (MNI-coordinates: [12.6, 64.23, -0.8] ± [13.64, 3.50, 11.01]). This individualized VMPFC-amygdala connectivity significantly correlated with VAS craving after cue exposure (R = 0.27, p = 0.03). Coil orientation was optimized to increase EF strength over the targeted circuit (0.99 ± 0.21 V/m vs. the fixed approach: Fp1: 0.56 ± 0.22 and Fp2: 0.78 ± 0.25 V/m) and TMS intensity was harmonized across the population. This study highlights the potential of an individualized VMPFC targeting framework to enhance treatment outcomes for addiction, specifically modulating the personalized VMPFC-amygdala circuit.

Effects of non-invasive brain stimulation on emotion regulation in patients with attention deficit hyperactivity disorder: a systematic review

Background and objective

A growing body of research evidence suggests that many patients with attention deficit hyperactivity disorder (ADHD) have difficulties with emotion regulation. Non-invasive brain stimulation (NIBS), which mainly includes transcranial electrical stimulation (tES) and repetitive transcranial magnetic stimulation (rTMS), has been considered a potential new direction in the treatment of emotion dysregulation in ADHD patients. The key components of tES are transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS). However, there is no systematic evaluation exploring the effects of non-invasive brain stimulation on emotion regulation in ADHD patients. Therefore, this systematic review aimed to summarize the effects of NIBS on emotion regulation in ADHD patients.

Methods

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched PubMed, Embase, Web of Science, and the Cochrane Library electronic databases up to 1 July 2024. We also hand-searched the reference lists of retrieved articles and reviews. Assessing risk of bias using the Cochrane Assessment Tool.

Results

Through database search, we obtained a total of 1134 studies, of which 5 met the inclusion criteria. Statistically significant improvements in emotion regulation in children with ADHD were observed in 1 study after treatment with tDCS. In the remaining 4 studies (2 with tDCS and 2 with rTMS), there were no statistically significant changes in emotion regulation in ADHD patients after treatment with either tDCS or rTMS.

Conclusions

The data from our preliminary study do not allow us to draw definitive conclusions that non-invasive brain stimulation improves emotion regulation in ADHD patients. This is because there is a paucity of literature on the effects of tES or rTMS on emotion regulation in ADHD patients and a limited number of randomized controlled trials. More high-quality multicenter randomized controlled trials exploring the efficacy of non-invasive brain stimulation on emotion regulation in ADHD patients are needed in the future to provide strong evidence for definitive conclusions before it can be considered as a potential treatment option.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024569041.

Lateral prefrontal theta oscillations causally drive a computational mechanism underlying conflict expectation and adaptation

Adapting our behavior to environmental demands relies on our capacity to perceive and manage potential conflicts within our surroundings. While evidence implicates the involvement of the lateral prefrontal cortex and theta oscillations in detecting conflict stimuli, their causal role in conflict expectation remains elusive. Consequently, the exact computations and neural mechanisms underlying these cognitive processes still need to be determined. We employed an integrative approach involving cognitive computational modeling, fMRI, TMS, and EEG to establish a causal link between oscillatory brain function, its neurocomputational role, and the resulting conflict processing and adaptation behavior. Our results reveal a computational process underlying conflict expectation, which correlates with BOLD-fMRI and theta activity in the superior frontal gyrus (SFG). Modulation of theta activity via rhythmic TMS applied over the SFG induces endogenous theta activity, which in turn enhances computations associated with conflict expectation. These findings provide evidence for the causal involvement of SFG theta activity in learning and allocating cognitive resources to address forthcoming conflict stimuli.

Reproducible routes: reliably navigating the connectome to enrich personalized brain stimulation strategies

Non-invasive brain stimulation (NIBS) technologies, such as repetitive transcranial magnetic stimulation (rTMS), offer significant therapeutic potential for a growing number of neuropsychiatric conditions. Concurrent with the expansion of this field is the swift evolution of rTMS methodologies, including approaches to optimize stimulation site planning. Traditional targeting methods, foundational to early successes in the field and still widely employed today, include using scalp-based heuristics or integrating structural MRI co-registration to align the transcranial magnetic stimulation (TMS) coil with anatomical landmarks. Recent evidence, however, supports refining and personalizing stimulation sites based on the target's structural and/or functional connectivity profile. These connectomic approaches harness the network-wide neuromodulatory effects of rTMS to reach deeper brain structures while also enabling a greater degree of personalization by accounting for heterogenous network topology. In this study, we acquired baseline multimodal magnetic resonance (MRI) at two time points to evaluate the reliability and reproducibility of distinct connectome-based strategies for stimulation site planning. Specifically, we compared the intra-individual difference between the optimal stimulation sites generated at each time point for (1) functional connectivity (FC) guided targets derived from resting-state functional MRI and (2) structural connectivity (SC) guided targets derived from diffusion tensor imaging. Our findings suggest superior reproducibility of SC-guided targets. We emphasize the necessity for further research to validate these findings across diverse patient populations, thereby advancing the personalization of rTMS treatments.

Neuromodulation and meditation: A review and synthesis toward promoting well-being and understanding consciousness and brain

The neuroscience of meditation is providing insight into meditation's beneficial effects on well-being and informing understanding of consciousness. However, further research is needed to explicate mechanisms linking brain activity and meditation. Non-invasive brain stimulation (NIBS) presents a promising approach for causally investigating neural mechanisms of meditation. Prior NIBS-meditation research has predominantly targeted frontal and parietal cortices suggesting that it might be possible to boost the behavioral and neural effects of meditation with NIBS. Moreover, NIBS has revealed distinct neural signatures in long-term meditators. Nonetheless, methodological variations in NIBS-meditation research contributes to challenges for definitive interpretation of previous results. Future NIBS studies should further investigate core substrates of meditation, including specific brain networks and oscillations, and causal neural mechanisms of advanced meditation. Overall, NIBS-meditation research holds promise for enhancing meditation-based interventions in support of well-being and resilience in both non-clinical and clinical populations, and for uncovering the brain-mind mechanisms of meditation and consciousness.

Group-common and individual-specific effects of structure-function coupling in human brain networks with graph neural networks

The human cerebral cortex is organized into functionally segregated but synchronized regions bridged by the structural connectivity of white matter pathways. While structure-function coupling has been implicated in cognitive development and neuropsychiatric disorders, it remains unclear to what extent the structure-function coupling reflects a group-common characteristic or varies across individuals, at both the global and regional brain levels. By leveraging two independent, high-quality datasets, we found that the graph neural network accurately predicted unseen individuals' functional connectivity from structural connectivity, reflecting a strong structure-function coupling. This coupling was primarily driven by network topology and was substantially stronger than that of the correlation approaches. Moreover, we observed that structure-function coupling was dominated by group-common effects, with subtle yet significant individual-specific effects. The regional group and individual effects of coupling were hierarchically organized across the cortex along a sensorimotor-association axis, with lower group and higher individual effects in association cortices. These findings emphasize the importance of considering both group and individual effects in understanding cortical structure-function coupling, suggesting insights into interpreting individual differences of the coupling and informing connectivity-guided therapeutics.

Efficacy of MRI-guided rTMS for post-traumatic stress disorder by modulating amygdala activity: study protocol for a randomised controlled trial

INTRODUCTION

Post-traumatic stress disorder (PTSD) is a prevalent and severe psychiatric disorder. Repetitive transcranial magnetic stimulation (rTMS) targeting the dorsolateral prefrontal cortex provides limited relief for symptoms of PTSD. This study will be conducted to validate the efficacy of MRI-guided rTMS in targeting the sites most closely associated with the amygdala for patients with PTSD. We hypothesise that the intervention will improve clinical symptoms by decreasing amygdala activity in patients.

METHODS AND ANALYSIS

A randomised, double-blind, sham-controlled trial will be conducted. Forty-eight eligible patients with PTSD will be randomly assigned to receive either active or sham MRI-guided rTMS for 10 consecutive days after the initial MRI scans. MRI scans will be recollected at the end of the intervention. Clinical assessments will be performed at baseline, treatment day 5, treatment day 10, and 2 weeks, 4 weeks, 8 weeks after completion of the intervention to monitor changes in clinical symptoms. The primary assessment outcome is the change in PTSD symptoms between baseline and treatment day 10, as measured by the PTSD Checklist for DSM-5. Repeated measures analysis of variance will be performed using statistical software SPSS V.26.0. The significance level will be set at 0.05.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the Ethics Committee of Xijing Hospital in Xi'an, China (KY20222176-X-1), and the trial has been registered on ClinicalTrials.gov. The findings of this trial will be disseminated at academic conferences or published in peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT05544110.

Distinct glutamatergic projections of the posteroventral medial amygdala play different roles in arousal and anxiety

Sleep disturbance usually accompanies anxiety disorders and exacerbates their incidence rates. The precise circuit mechanisms remain poorly understood. Here, we found that glutamatergic neurons in the posteroventral medial amygdala (MePVGlu neurons) are involved in arousal and anxiety-like behaviors. Excitation of MePVGlu neurons not only promoted wakefulness but also increased anxiety-like behaviors. Different projections of MePVGlu neurons played various roles in regulating anxiety-like behaviors and sleep-wakefulness. MePVGlu neurons promoted wakefulness through the MePVGlu/posteromedial cortical amygdaloid area (PMCo) pathway and the MePVGlu/bed nucleus of the stria terminals (BNST) pathway. In contrast, MePVGlu neurons increased anxiety-like behaviors through the MePVGlu/ventromedial hypothalamus (VMH) pathway. Chronic sleep disturbance increased anxiety levels and reduced reparative sleep, accompanied by the enhanced excitability of MePVGlu/PMCo and MePVGlu/VMH circuits but suppressed responses of glutamatergic neurons in the BNST. Inhibition of the MePVGlu neurons could rescue chronic sleep deprivation-induced phenotypes. Our findings provide important circuit mechanisms for chronic sleep disturbance-induced hyperarousal response and obsessive anxiety-like behavior and are expected to provide a promising strategy for treating sleep-related psychiatric disorders and insomnia.

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.

Enhancing ventrolateral prefrontal cortex activation mitigates social pain and modifies subsequent social attitudes: Insights from TMS and fMRI

Social pain, a multifaceted emotional response triggered by interpersonal rejection or criticism, profoundly impacts mental well-being and social interactions. While prior research has implicated the right ventrolateral prefrontal cortex (rVLPFC) in mitigating social pain, the precise neural mechanisms and downstream effects on subsequent social attitudes remain elusive. This study employed transcranial magnetic stimulation (TMS) integrated with fMRI recordings during a social pain task to elucidate these aspects. Eighty participants underwent either active TMS targeting the rVLPFC (n = 41) or control stimulation at the vertex (n = 39). Our results revealed that TMS-induced rVLPFC facilitation significantly reduced self-reported social pain, confirming the causal role of the rVLPFC in social pain relief. Functional connectivity analyses demonstrated enhanced interactions between the rVLPFC and the dorsolateral prefrontal cortex, emphasizing the collaborative engagement of prefrontal regions in emotion regulation. Significantly, we observed that negative social feedback led to negative social attitudes, whereas rVLPFC activation countered this detrimental effect, showcasing the potential of the rVLPFC as a protective buffer against adverse social interactions. Moreover, our study uncovered the impact role of the hippocampus in subsequent social attitudes, a relationship particularly pronounced during excitatory TMS over the rVLPFC. These findings offer promising avenues for improving mental health within the intricate dynamics of social interactions. By advancing our comprehension of the neural mechanisms underlying social pain relief, this research introduces novel intervention strategies for individuals grappling with social distress. Empowering individuals to modulate rVLPFC activation may facilitate reshaping social attitudes and successful reintegration into communal life.

Enhancing cognitive control with transcranial magnetic stimulation in subject-specific frontoparietal networks

BACKGROUND

Cognitive control processes, including those involving frontoparietal networks, are highly variable between individuals, posing challenges to basic and clinical sciences. While distinct frontoparietal networks have been associated with specific cognitive control functions such as switching, inhibition, and working memory updating functions, there have been few basic tests of the role of these networks at the individual level.

METHODS

To examine the role of cognitive control at the individual level, we conducted a within-subject excitatory transcranial magnetic stimulation (TMS) study in 19 healthy individuals that targeted intrinsic ("resting") frontoparietal networks. Person-specific intrinsic networks were identified with resting state functional magnetic resonance imaging scans to determine TMS targets. The participants performed three cognitive control tasks: an adapted Navon figure-ground task (requiring set switching), n-back (working memory), and Stroop color-word (inhibition).

OBJECTIVE

Hypothesis: We predicted that stimulating a network associated with externally oriented control [the "FPCN-B" (fronto-parietal control network)] would improve performance on the set switching and working memory task relative to a network associated with attention (the Dorsal Attention Network, DAN) and cranial vertex in a full within-subjects crossover design.

RESULTS

We found that set switching performance was enhanced by FPCN-B stimulation along with some evidence of enhancement in the higher-demand n-back conditions.

CONCLUSION

Higher task demands or proactive control might be a distinguishing role of the FPCN-B, and personalized intrinsic network targeting is feasible in TMS designs.

Aerobic exercise promotes emotion regulation: a narrative review

Aerobic exercise improves the three stages of emotion regulation: perception, valuation and action. It reduces the perception of negative emotions, encourages individuals to reinterpret emotional situations in a positive or non-emotional manner, and enhances control over emotion expression behaviours. These effects are generated via increased prefrontal cortex activation, the strengthening of functional connections between the amygdala and several other brain regions, and the enhancement of the plasticity of key emotion regulation pathways and nodes, such as the uncinate fasciculus. The effect of aerobic exercise on emotion regulation is influenced by the exercise intensity and duration, and by individuals' exercise experience. Future research may explore the key neural basis of aerobic exercise's promotion of emotion regulation.

Elevating the field for applying neuroimaging to individual patients in psychiatry

Although neuroimaging has been widely applied in psychiatry, much of the exuberance in decades past has been tempered by failed replications and a lack of definitive evidence to support the utility of imaging to inform clinical decisions. There are multiple promising ways forward to demonstrate the relevance of neuroimaging for psychiatry at the individual patient level. Ultra-high field magnetic resonance imaging is developing as a sensitive measure of neurometabolic processes of particular relevance that holds promise as a new way to characterize patient abnormalities as well as variability in response to treatment. Neuroimaging may also be particularly suited to the science of brain stimulation interventions in psychiatry given that imaging can both inform brain targeting as well as measure changes in brain circuit communication as a function of how effectively interventions improve symptoms. We argue that a greater focus on individual patient imaging data will pave the way to stronger relevance to clinical care in psychiatry. We also stress the importance of using imaging in symptom-relevant experimental manipulations and how relevance will be best demonstrated by pairing imaging with differential treatment prediction and outcome measurement. The priorities for using brain imaging to inform psychiatry may be shifting, which compels the field to solidify clinical relevance for individual patients over exploratory associations and biomarkers that ultimately fail to replicate.

Cortical and subcortical microstructure integrity changes after repetitive transcranial magnetic stimulation therapy in cocaine use disorder and relates to clinical outcomes

Cocaine use disorder (CUD) is a worldwide public health condition that is suggested to induce pathological changes in macrostructure and microstructure. Repetitive transcranial magnetic stimulation (rTMS) has gained attention as a potential treatment for CUD symptoms. Here, we sought to elucidate whether rTMS induces changes in white matter (WM) microstructure in frontostriatal circuits after 2 weeks of therapy in patients with CUD and to test whether baseline WM microstructure of the same circuits affects clinical improvement. This study consisted of a 2-week, parallel-group, double-blind, randomized controlled clinical trial (acute phase) (sham [n = 23] and active [n = 27]), in which patients received two daily sessions of rTMS on the left dorsolateral prefrontal cortex (lDLPFC) as an add-on treatment. T1-weighted and high angular resolution diffusion-weighted imaging (DWI-HARDI) at baseline and 2 weeks after served to evaluate WM microstructure. After active rTMS, results showed a significant increase in neurite density compared with sham rTMS in WM tracts connecting lDLPFC with left and right ventromedial prefrontal cortex (vmPFC). Similarly, rTMS showed a reduction in orientation dispersion in WM tracts connecting lDLPFC with the left caudate nucleus, left thalamus, and left vmPFC. Results also showed a greater reduction in craving Visual Analogue Scale (VAS) after rTMS when baseline intra-cellular volume fraction (ICVF) was low in WM tracts connecting left caudate nucleus with substantia nigra and left pallidum, as well as left thalamus with substantia nigra and left pallidum. Our results evidence rTMS-induced WM microstructural changes in fronto-striato-thalamic circuits and support its efficacy as a therapeutic tool in treating CUD. Further, individual clinical improvement may rely on the patient's individual structural connectivity integrity.

Accelerated TMS - moving quickly into the future of depression treatment

Accelerated TMS is an emerging application of Transcranial Magnetic Stimulation (TMS) aimed to reduce treatment length and improve response time. Extant literature generally shows similar efficacy and safety profiles compared to the FDA-cleared protocols for TMS to treat major depressive disorder (MDD), yet accelerated TMS research remains at a very early stage in development. The few applied protocols have not been standardized and vary significantly across a set of core elements. In this review, we consider nine elements that include treatment parameters (i.e., frequency and inter-stimulation interval), cumulative exposure (i.e., number of treatment days, sessions per day, and pulses per session), individualized parameters (i.e., treatment target and dose), and brain state (i.e., context and concurrent treatments). Precisely which of these elements is critical and what parameters are most optimal for the treatment of MDD remains unclear. Other important considerations for accelerated TMS include durability of effect, safety profiles as doses increase over time, the possibility and advantage of individualized functional neuronavigation, use of biological readouts, and accessibility for patients most in need of the treatment. Overall, accelerated TMS appears to hold promise to reduce treatment time and achieve rapid reduction in depressive symptoms, but at this time significant work remains to be done. Rigorous clinical trials combining clinical outcomes and neuroscientific measures such as electroencephalogram, magnetic resonance imaging and e-field modeling are needed to define the future of accelerated TMS for MDD.

Characterization of Anxiety-Like Behaviors and Neural Circuitry following Chronic Moderate Noise Exposure in Mice

BACKGROUND

Commonly encountered nontraumatic, moderate noise is increasingly implicated in anxiety; however, the neural substrates underlying this process remain unclear.

OBJECTIVES

We investigated the neural circuit mechanism through which chronic exposure to moderate-level noise causes anxiety-like behaviors.

METHODS

Mice were exposed to chronic, moderate white noise [85 decibel (dB) sound pressure level (SPL)], 4 h/d for 4 wk to induce anxiety-like behaviors, which were assessed by open field, elevated plus maze, light-dark box, and social interaction tests. Viral tracing, immunofluorescence confocal imaging, and brain slice patch-clamp recordings were used to characterize projections from auditory brain regions to the lateral amygdala. Neuronal activities were characterized by in vivo multielectrode and fiber photometry recordings in awake mice. Optogenetics and chemogenetics were used to manipulate specific neural circuitry.

RESULTS

Mice chronically (4 wk) exposed to moderate noise (85 dB SPL, 4 h/d) demonstrated greater neuronal activity in the lateral amygdala (LA), and the LA played a critical role in noise-induced anxiety-like behavior in these model mice. Viral tracing showed that the LA received monosynaptic projections from the medial geniculate body (MG) and auditory cortex (ACx). Optogenetic excitation of the MG → LA or ACx → LA circuits acutely evoked anxiety-like behaviors, whereas their chemogenetic inactivation abolished noise-induced anxiety-like behavior. Moreover, mice chronically exposed to moderate noise were more susceptible to acute stress, with more neuronal firing in the LA, even after noise withdrawal.

DISCUSSION

Mice exposed to 4 wk of moderate noise (85 dB SPL, 4 h/d) demonstrated behavioral and physiological differences compared to controls. The neural circuit mechanisms involved greater excitation from glutamatergic neurons of the MG and ACx to LA neurons under chronic, moderate noise exposure, which ultimately promoted anxiety-like behaviors. Our findings support the hypothesis that nontraumatic noise pollution is a potentially serious but unrecognized public health concern. https://doi.org/10.1289/EHP12532.

Brain network communication: concepts, models and applications

Understanding communication and information processing in nervous systems is a central goal of neuroscience. Over the past two decades, advances in connectomics and network neuroscience have opened new avenues for investigating polysynaptic communication in complex brain networks. Recent work has brought into question the mainstay assumption that connectome signalling occurs exclusively via shortest paths, resulting in a sprawling constellation of alternative network communication models. This Review surveys the latest developments in models of brain network communication. We begin by drawing a conceptual link between the mathematics of graph theory and biological aspects of neural signalling such as transmission delays and metabolic cost. We organize key network communication models and measures into a taxonomy, aimed at helping researchers navigate the growing number of concepts and methods in the literature. The taxonomy highlights the pros, cons and interpretations of different conceptualizations of connectome signalling. We showcase the utility of network communication models as a flexible, interpretable and tractable framework to study brain function by reviewing prominent applications in basic, cognitive and clinical neurosciences. Finally, we provide recommendations to guide the future development, application and validation of network communication models.

The VLPFC-Engaged Voluntary Emotion Regulation: Combined TMS-fMRI Evidence for the Neural Circuit of Cognitive Reappraisal

A clear understanding of the neural circuit underlying emotion regulation (ER) is important for both basic and translational research. However, a lack of evidence based on combined neuroimaging and neuromodulation techniques calls into question (1) whether the change of prefrontal-subcortical activity intrinsically and causally contributes to the ER effect; and (2) whether the prefrontal control system directly modulates the subcortical affective system. Accordingly, we combined fMRI recordings with transcranial magnetic stimulation (TMS) to map the causal connections between the PFC and subcortical affective structures (amygdala and insula). A total of 117 human adult participants (57 males and 60 females) were included in the study. The results revealed that TMS-induced ventrolateral PFC (VLPFC) facilitation led to enhanced activity in the VLPFC and ventromedial PFC (VMPFC) as well as attenuated activity in the amygdala and insula during reappraisal but not during nonreappraisal (i.e., baseline). Moreover, the activated VLPFC intensified the prefrontal-subcortical couplings via the VMPFC during reappraisal only. This study provides combined TMS-fMRI evidence that downregulating negative emotion involves the prefrontal control system suppressing the subcortical affective system, with the VMPFC serving as a crucial hub within the VLPFC-subcortical network, suggesting an indirect pathway model of the ER circuit. Our findings outline potential protocols for improving ER ability by intensifying the VLPFC-VMPFC coupling in patients with mood and anxiety disorders.SIGNIFICANCE STATEMENT Using fMRI to examine the TMS effect, we uncovered that the opposite neural changes in prefrontal (enhanced) and subcortical (attenuated) regions are not a byproduct of emotion regulation (ER); instead, this prefrontal-subcortical activity per se causally contributes to the ER effect. Furthermore, using TMS to amplify the neural changes within the ER circuit, the "bridge" role of the VMPFC is highlighted under the reappraisal versus nonreappraisal contrast. This "perturb-and-measure" approach overcomes the correlational nature of fMRI data, helping us to identify brain regions that causally support reappraisal (the VLPFC and VMPFC) and those that are modulated by reappraisal (the amygdala and insula). The uncovered ER circuit is important for understanding the neural systems underlying reappraisal and valuable for translational research.

Electric field distribution predicts efficacy of accelerated intermittent theta burst stimulation for late-life depression

Introduction

Repetitive transcranial magnetic stimulation (rTMS) is a promising intervention for late-life depression (LLD) but may have lower rates of response and remission owing to age-related brain changes. In particular, rTMS induced electric field strength may be attenuated by cortical atrophy in the prefrontal cortex. To identify clinical characteristics and treatment parameters associated with response, we undertook a pilot study of accelerated fMRI-guided intermittent theta burst stimulation (iTBS) to the right dorsolateral prefrontal cortex in 25 adults aged 50 or greater diagnosed with LLD and qualifying to receive clinical rTMS.

Methods

Participants underwent baseline behavioral assessment, cognitive testing, and structural and functional MRI to generate individualized targets and perform electric field modeling. Forty-five sessions of iTBS were delivered over 9 days (1800 pulses per session, 50-min inter-session interval). Assessments and testing were repeated after 15 sessions (Visit 2) and 45 sessions (Visit 3). Primary outcome measure was the change in depressive symptoms on the Inventory of Depressive Symptomatology-30-Clinician (IDS-C-30) from Visit 1 to Visit 3.

Results

Overall there was a significant improvement in IDS score with the treatment (Visit 1: 38.6; Visit 2: 31.0; Visit 3: 21.3; mean improvement 45.5%) with 13/25 (52%) achieving response and 5/25 (20%) achieving remission (IDS-C-30 < 12). Electric field strength and antidepressant effect were positively correlated in a subregion of the ventrolateral prefrontal cortex (VLPFC) (Brodmann area 47) and negatively correlated in the posterior dorsolateral prefrontal cortex (DLPFC).

Conclusion

Response and remission rates were lower than in recently published trials of accelerated fMRI-guided iTBS to the left DLPFC. These results suggest that sufficient electric field strength in VLPFC may be a contributor to effective rTMS, and that modeling to optimize electric field strength in this area may improve response and remission rates. Further studies are needed to clarify the relationship of induced electric field strength with antidepressant effects of rTMS for LLD.

Mechanisms underlying capsulotomy for refractory obsessive-compulsive disorder: neural correlates of negative affect processing overlap with deep brain stimulation targets

Ablative procedures such as anterior capsulotomy are potentially effective in refractory obsessive-compulsive disorder (OCD). Converging evidence suggests the ventral internal capsule white matter tracts traversing the rostral cingulate and ventrolateral prefrontal cortex and thalamus is the optimal target for clinical efficacy across multiple deep brain stimulation targets for OCD. Here we ask which prefrontal regions and underlying cognitive processes might be implicated in the effects of capsulotomy by using both task fMRI and neuropsychological tests assessing OCD-relevant cognitive mechanisms known to map across prefrontal regions connected to the tracts targeted in capsulotomy. We tested OCD patients at least 6 months post-capsulotomy (n = 27), OCD controls (n = 33) and healthy controls (n = 34). We used a modified aversive monetary incentive delay paradigm with negative imagery and a within session extinction trial. Post-capsulotomy OCD subjects showed improved OCD symptoms, disability and quality of life with no differences in mood or anxiety or cognitive task performance on executive, inhibition, memory and learning tasks. Task fMRI revealed post-capsulotomy decreases in the nucleus accumbens during negative anticipation, and in the left rostral cingulate and left inferior frontal cortex during negative feedback. Post-capsulotomy patients showed attenuated accumbens-rostral cingulate functional connectivity. Rostral cingulate activity mediated capsulotomy improvement on obsessions. These regions overlap with optimal white matter tracts observed across multiple stimulation targets for OCD and might provide insights into further optimizing neuromodulation approaches. Our findings also suggest that aversive processing theoretical mechanisms may link ablative, stimulation and psychological interventions.

Anatomical and Functional Connectivity of Critical Deep Brain Structures and Their Potential Clinical Application in Brain Stimulation

Subcortical structures, such as the hippocampus, amygdala, and nucleus accumbens (NAcc), play crucial roles in human cognitive, memory, and emotional processing, chronic pain pathophysiology, and are implicated in various psychiatric and neurological diseases. Interventions modulating the activities of these deep brain structures hold promise for improving clinical outcomes. Recently, non-invasive brain stimulation (NIBS) has been applied to modulate brain activity and has demonstrated its potential for treating psychiatric and neurological disorders. However, modulating the above deep brain structures using NIBS may be challenging due to the nature of these stimulations. This study attempts to identify brain surface regions as source targets for NIBS to reach these deep brain structures by integrating functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI). We used resting-state functional connectivity (rsFC) and probabilistic tractography (PTG) analysis to identify brain surface stimulation targets that are functionally and structurally connected to the hippocampus, amygdala, and NAcc in 119 healthy participants. Our results showed that the medial prefrontal cortex (mPFC) is functionally and anatomically connected to all three subcortical regions, while the precuneus is connected to the hippocampus and amygdala. The mPFC and precuneus, two key hubs of the default mode network (DMN), as well as other cortical areas distributed at the prefrontal cortex and the parietal, temporal, and occipital lobes, were identified as potential locations for NIBS to modulate the function of these deep structures. The findings may provide new insights into the NIBS target selections for treating psychiatric and neurological disorders and chronic pain.

Optimizing Individual Targeting of Fronto-Amygdala Network with Transcranial Magnetic Stimulation (TMS): Biophysical, Physiological and Behavioral Variations in People with Methamphetamine Use Disorder

Background

Previous studies in people with substance use disorders (SUDs) have implicated both the frontopolar cortex and amygdala in drug cue reactivity and craving, and amygdala-frontopolar coupling is considered a marker of early relapse risk. Accumulating data highlight that the frontopolar cortex can be considered a promising therapeutic target for transcranial magnetic stimulation (TMS) in SUDs. However, one-size-fits-all approaches to TMS targets resulted in substantial variation in both physiological and behavioral outcomes. Individualized TMS approaches to target cortico-subcortical circuits like amygdala-frontopolar have not yet been investigated in SUDs.

Objective

Here, we (1) defined individualized TMS target location based on functional connectivity of the amygdala-frontopolar circuit while people were exposed to drug-related cues, (2) optimized coil orientation based on maximizing electric field (EF) perpendicular to the individualized target, and (3) harmonized EF strength in targeted brain regions across a population.

Method

MRI data including structural, resting-state, and task-based fMRI data were collected from 60 participants with methamphetamine use disorders (MUDs). Craving scores based on a visual analog scale were collected immediately before and after the MRI session. We analyzed inter-subject variability in the location of TMS targets based on the maximum task-based connectivity between the left medial amygdala (with the highest functional activity among subcortical areas during drug cue exposure) and frontopolar cortex using psychophysiological interaction (PPI) analysis. Computational head models were generated for all participants and EF simulations were calculated for fixed vs. optimized coil location (Fp1/Fp2 vs. individualized maximal PPI location), orientation (AF7/AF8 vs. orientation optimization algorithm), and stimulation intensity (constant vs. adjusted intensity across the population).

Results

Left medial amygdala with the highest (mean ± SD: 0.31±0.29) functional activity during drug cue exposure was selected as the subcortical seed region. Amygdala-to-whole brain PPI analysis showed a significant cluster in the prefrontal cortex (cluster size: 2462 voxels, cluster peak in MNI space: [25 39 35]) that confirms cortico-subcortical connections. The location of the voxel with the most positive amygdala-frontopolar PPI connectivity in each participant was considered as the individualized TMS target (mean ± SD of the MNI coordinates: [12.6 64.23 -0.8] ± [13.64 3.50 11.01]). Individual amygdala-frontopolar PPI connectivity in each participant showed a significant correlation with VAS scores after cue exposure (R=0.27, p=0.03). Averaged EF strength in a sphere with r = 5mm around the individualized target location was significantly higher in the optimized (mean ± SD: 0.99 ± 0.21) compared to the fixed approach (Fp1: 0.56 ± 0.22, Fp2: 0.78 ± 0.25) with large effect sizes (Fp1: p = 1.1e-13, Hedges'g = 1.5, Fp2: p = 1.7e-5, Hedges'g = 1.26). Adjustment factor to have identical 1 V/m EF strength in a 5mm sphere around the individualized targets ranged from 0.72 to 2.3 (mean ± SD: 1.07 ± 0.29).

Conclusion

Our results show that optimizing coil orientation and stimulation intensity based on individualized TMS targets led to stronger electric fields in the targeted brain regions compared to a one-size-fits-all approach. These findings provide valuable insights for refining TMS therapy for SUDs by optimizing the modulation of cortico-subcortical circuits.

Interactions between Guidance Cues and Neuronal Activity: Therapeutic Insights from Mouse Models

Topographic mapping of neural circuits is fundamental in shaping the structural and functional organization of brain regions. This developmentally important process is crucial not only for the representation of different sensory inputs but also for their integration. Disruption of topographic organization has been associated with several neurodevelopmental disorders. The aim of this review is to highlight the mechanisms involved in creating and refining such well-defined maps in the brain with a focus on the Eph and ephrin families of axon guidance cues. We first describe the transgenic models where ephrin-A expression has been manipulated to understand the role of these guidance cues in defining topography in various sensory systems. We further describe the behavioral consequences of lacking ephrin-A guidance cues in these animal models. These studies have given us unexpected insight into how neuronal activity is equally important in refining neural circuits in different brain regions. We conclude the review by discussing studies that have used treatments such as repetitive transcranial magnetic stimulation (rTMS) to manipulate activity in the brain to compensate for the lack of guidance cues in ephrin-knockout animal models. We describe how rTMS could have therapeutic relevance in neurodevelopmental disorders with disrupted brain organization.

Communication dynamics in the human connectome shape the cortex-wide propagation of direct electrical stimulation

Communication between gray matter regions underpins all facets of brain function. We study inter-areal communication in the human brain using intracranial EEG recordings, acquired following 29,055 single-pulse direct electrical stimulations in a total of 550 individuals across 20 medical centers (average of 87 ± 37 electrode contacts per subject). We found that network communication models-computed on structural connectivity inferred from diffusion MRI-can explain the causal propagation of focal stimuli, measured at millisecond timescales. Building on this finding, we show that a parsimonious statistical model comprising structural, functional, and spatial factors can accurately and robustly predict cortex-wide effects of brain stimulation (R²=46% in data from held-out medical centers). Our work contributes toward the biological validation of concepts in network neuroscience and provides insight into how connectome topology shapes polysynaptic inter-areal signaling. We anticipate that our findings will have implications for research on neural communication and the design of brain stimulation paradigms.

Real-world data of non-invasive stimulation of the human insula-prefrontal cortices using deep TMS to treat anxiety for occupational stress and generalized anxiety disorder

Activation of the insula is found in all anxiety-related disorders and increased insular-prefrontal cortex (PFC) functional connectivity is associated with reduced anxiety. In this study, the combined stimulation of the insula and PFC using the dTMS H4 (insula+LPFC) and H2 (PFC) coils were used to reduce anxiety in 13 subjects experiencing occupational stress, and 55 participants suffering from generalized anxiety disorder (GAD). The combined HF stimulation of the insula and PFC significantly decreased anxiety scores according to the HARS, CAS, and STAI anxiety scales, leading to a reduction in anxiety according to HARS of 88.7% and 70.7% in participants with occupational stress and the clinical sample of participants diagnosed with GAD, respectively. The findings suggest that the prefrontal-insular axis is critical for the regulation of anxiety and its stimulation can be used for the treatment of anxiety in people suffering from occupational stress and GAD.

Causally mapping human threat extinction relevant circuits with depolarizing brain stimulation methods

Laboratory threat extinction paradigms and exposure-based therapy both involve repeated, safe confrontation with stimuli previously experienced as threatening. This fundamental procedural overlap supports laboratory threat extinction as a compelling analogue of exposure-based therapy. Threat extinction impairments have been detected in clinical anxiety and may contribute to exposure-based therapy non-response and relapse. However, efforts to improve exposure outcomes using techniques that boost extinction - primarily rodent extinction - have largely failed to date, potentially due to fundamental differences between rodent and human neurobiology. In this review, we articulate a comprehensive pre-clinical human research agenda designed to overcome these failures. We describe how connectivity guided depolarizing brain stimulation methods (i.e., TMS and DBS) can be applied concurrently with threat extinction and dual threat reconsolidation-extinction paradigms to causally map human extinction relevant circuits and inform the optimal integration of these methods with exposure-based therapy. We highlight candidate targets including the amygdala, hippocampus, ventromedial prefrontal cortex, dorsal anterior cingulate cortex, and mesolimbic structures, and propose hypotheses about how stimulation delivered at specific learning phases could strengthen threat extinction.

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.

Mapping a pathway to improved neuropsychiatric treatments with precision transcranial magnetic stimulation

Transcranial magnetic stimulation traces the functional and structural connections that modulate amygdala activity, enabling advanced brain stimulation treatments for numerous psychiatric disorders.