A Near Infra-Red Study of Blood Oxygenation Changes Resulting From High and Low Frequency Repetitive Transcranial Magnetic Stimulation

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.

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.

The Comparison of Early Hemodynamic Response to Single-Pulse Transcranial Magnetic Stimulation following Inhibitory or Excitatory Theta Burst Stimulation on Motor Cortex

We present a new study design aiming to enhance the understanding of the mechanism by which continuous theta burst stimulation (cTBS) or intermittent theta burst stimulation (iTBS) paradigms elicit cortical modulation. Using near-infrared spectroscopy (NIRS), we compared the cortical hemodynamics of the previously inhibited (after cTBS) or excited (after iTBS) left primary motor cortex (M1) as elicited by single-pulse TMS (spTMS) in a cross-over design. Mean relative changes in hemodynamics within 6 s of the stimulus were compared using a two-sample t-test (p < 0.05) and linear mixed model between real and sham stimuli and between stimuli after cTBS and iTBS. Only spTMS after cTBS resulted in a significant increase (p = 0.04) in blood volume (BV) compared to baseline. There were no significant changes in other hemodynamic parameters (oxygenated/deoxygenated hemoglobin). spTMS after cTBS induced a larger increase in BV than spTMS after iTBS (p = 0.021) and sham stimulus after cTBS (p = 0.009). BV showed no significant difference between real and sham stimuli after iTBS (p = 0.37). The greater hemodynamic changes suggest increased vasomotor reactivity after cTBS compared to iTBS. In addition, cTBS could decrease lateral inhibition, allowing activation of surrounding areas after cTBS.

Impact of combination of intermittent theta burst stimulation and methadone maintenance treatment in individuals with opioid use disorder: A comparative study

Prior studies indicate that subjects undergoing methadone maintenance therapy (MMT) may experience anxiety, depression and cravings. This study aimed to explore the impact of intermittent theta burst stimulation (iTBS)-MMT combination on craving and emotional symptoms of opioid use disorder. This comparative study included subjects with opioid use disorder at the Methadone Maintenance Clinic of Pudong New Area between September 2019 and March 2020. The subjects were divided into two groups: those who received iTBS-MMT combination treatment (iTBS-MMT) and those who received MMT treatment and sham stimulation treatment (MMT). Outcomes were reduction rate of anxiety, depression and craving. Anxiety was measured by Hamilton Anxiety (HAMA) scale, depression was determined by Hamilton Depression (HAMD) scale and craving was analyzed using visual analog scale. A total of 76 subjects completed the treatment, with 38 subjects in each group. Twenty days after treatment, subjects in the iTBS-MMT group had significant improvement of anxiety (HAMA reduction rate), depression (HAMD reduction rate) and craving (Craving reduction rate) reduction rate compared with MMT group. iTBS-MMT combination treatment may produce better drug craving reduction and emotional improvement than MMT alone.

Associations between frontal lobe activity and depressive symptoms in patients with major depressive disorder receiving rTMS treatment: a near-infrared spectroscopy study

Introduction

The effects of repetitive transcranial magnetic stimulation (rTMS) on the left dorsolateral prefrontal cortex (DLPFC) in patients with major depressive disorder (MDD) have been proved to have antidepressant effects. However, the absence of biomarkers to assess treatment response remains a challenge. This research aims to explore the relationship between frontal lobe activity, measured using near infrared spectroscopy (NIRS), and changes in symptoms among MDD patients following rTMS treatment.

Methods

A total of 26 MDD patients underwent 20 sessions of 10  Hz rTMS targeting the left DLPFC. NIRS was used to measure frontal lobe activity during a verbal fluency test at baseline, after 10 rTMS sessions, and after 20 rTMS sessions. Responders were defined as individuals with more than a 50% reduction in symptoms based on the 21-item Hamilton Depression Rating Scale after 20 rTMS sessions.

Results

Among the 14 responders, an increase in frontal lobe activity was significantly correlated with improvements in depressive symptoms following 10 (p = 0.0001) and 20 rTMS sessions (p = 0.007). Additionally, frontal lobe activity after 10 rTMS sessions was significantly associated with symptom improvement after 20 sessions (p = 0.001). These associations were not observed among non-responders.

Conclusion

The findings from this study indicate distinct patterns of frontal lobe activity between responders and non-responders to rTMS treatment, suggesting that NIRS has the potential to serve as a biomarker for monitoring treatment response in MDD patients undergoing rTMS.

Low-intensity ultrasound stimulation modulates time-frequency patterns of cerebral blood oxygenation and neurovascular coupling of mouse under peripheral sensory stimulation state

Previous studies have demonstrated that transcranial ultrasound stimulation (TUS) not only modulates cerebral hemodynamics, neural activity, and neurovascular coupling characteristics in resting samples but also exerts a significant inhibitory effect on the neural activity in task samples. However, the effect of TUS on cerebral blood oxygenation and neurovascular coupling in task samples remains to be elucidated. To answer this question, we first used forepaw electrical stimulation of the mice to elicit the corresponding cortical excitation, and then stimulated this cortical region using different modes of TUS, and simultaneously recorded the local field potential using electrophysiological acquisition and hemodynamics using optical intrinsic signal imaging. The results indicate that for the mice under peripheral sensory stimulation state, TUS with a duty cycle of 50% can (1) enhance the amplitude of cerebral blood oxygenation signal, (2) reduce the time-frequency characteristics of evoked potential, (3) reduce the strength of neurovascular coupling in time domain, (4) enhance the strength of neurovascular coupling in frequency domain, and (5) reduce the time-frequency cross-coupling of neurovasculature. The results of this study indicate that TUS can modulate the cerebral blood oxygenation and neurovascular coupling in peripheral sensory stimulation state mice under specific parameters. This study opens up a new area of investigation for potential applicability of TUS in brain diseases related to cerebral blood oxygenation and neurovascular coupling.

Protocol for a prospective open-label clinical trial to investigate the utility of concurrent TBS/fNIRS for antidepressant treatment optimisation

INTRODUCTION

Repetitive transcranial magnetic stimulation (rTMS) with theta burst stimulation (i.e. TBS) of the dorsolateral prefrontal cortex (DLPFC) is an innovative treatment for major depressive disorder (MDD). However, fewer than 50% of patients show sufficient response to this treatment; markers for response prediction are urgently needed. Research shows considerable individual variability in the brain responses to rTMS. However, whether differences in individual DLPFC modulation by rTMS can be used as a predictive marker for treatment response remains to be investigated. Here, we present a research programme that will exploit the combination of functional near-infrared spectroscopy (fNIRS) with brain stimulation. Concurrent TBS/fNIRS will allow us to systematically investigate TBS-induced modulation of blood oxygenation as a proxy for induced brain activity changes. The findings from this study will (1) elucidate the immediate effects of excitatory and inhibitory TBS on prefrontal activity in TBS treatment-naïve patients with MDD and (2) validate the potential utility of TBS-induced brain modulation at baseline for the prediction of antidepressant response to 4 weeks of daily TBS treatment.

METHODS AND ANALYSIS

Open-label, parallel-group experiment consisting of two parts. In part 1, 70 patients and 37 healthy controls will be subjected to concurrent TBS/fNIRS. Intermittent TBS (iTBS) and continuous TBS (cTBS) will be applied on the left and right DLPFC, respectively. fNIRS data will be acquired before, during and several minutes after stimulation. In part 2, patients who participated in part 1 will receive a 4 week iTBS treatment of the left DLPFC, performed daily for 5 days per week. Psychometric evaluation will be performed periodically and at 1 month treatment follow-up. Statistical analysis will include a conventional, as well as a machine learning approach.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the Institutional Review Board. Findings will be disseminated through scientific journals, conferences and university courses.

TRIAL REGISTRATION NUMBER

NCT04526002.

Increased Prefrontal Activation During Verbal Fluency Task After Repetitive Transcranial Magnetic Stimulation Treatment in Depression: A Functional Near-Infrared Spectroscopy Study

BACKGROUND

Previous studies have shown the clinical effect of 2 Hz repetitive transcranial magnetic stimulation (rTMS) for depression; however, its underlying neural mechanisms are poorly understood. The aim of this study was to examine the effects of rTMS on the activity of the prefrontal cortex in patients with depression, using functional near-infrared spectroscopy (fNIRS).

METHODS

Forty patients with major depressive disorder (MDD) and 40 healthy controls were enrolled in this study. Patients underwent 4 weeks of 2 Hz TMS delivered to the right dorsolateral prefrontal cortex (DLPFC). fNIRS was used to measure the changes in the concentration of oxygenated hemoglobin ([oxy-Hb]) in the prefrontal cortex during a verbal fluency task (VFT) in depressed patients before and after rTMS treatment. The severity of depression was assessed using the Hamilton Rating Scale for Depression-24 item (HAMD-24).

RESULTS

Prior to rTMS, depressed patients exhibited significantly smaller [oxy-Hb] values in the bilateral prefrontal cortex during the VFT compared with the healthy controls. After 4 weeks of 2 Hz right DLPFC rTMS treatment, increased [oxy-Hb] values in the bilateral frontopolar prefrontal cortex (FPPFC), ventrolateral prefrontal cortex (VLPFC) and left DLPFC during the VFT were observed in depressed patients. The increased [oxy-Hb] values from baseline to post-treatment in the right VLPFC in depressed patients were positively related to the reduction of HAMD score following rTMS.

CONCLUSION

These findings suggest that the function of the prefrontal cortex in depressed patients was impaired and could be recovered by 2 Hz rTMS. The fNIRS-measured prefrontal activation during a cognitive task is a potential biomarker for monitoring depressed patients' treatment response to rTMS.

A 50 Hz magnetic field affects hemodynamics, ECG and vascular endothelial function in healthy adults: A pilot randomized controlled trial

Application of exposure to 50/60 Hz magnetic fields (MFs) has been conducted in the treatment of muscle pain and fatigue mainly in Japan. However, whether MFs could increase blood flow leading to muscle fatigue recovery has not been sufficiently tested. We investigated the acute effects of a 50 Hz sinusoidal MF at Bmax 180 mT on hemodynamics, electrocardiogram, and vascular endothelial function in healthy young men. Three types of regional exposures to a 50 Hz MF, i.e., forearm, upper arm, or neck exposure to MF were performed. Participants who received three types of real MF exposures had significantly increased ulnar arterial blood flow velocity compared to the sham exposures. Furthermore, after muscle loading exercise, MF exposure recovered hemoglobin oxygenation index values faster and higher than sham exposure from the loading condition. Moreover, participants who received real MF exposure in the neck region had significantly increased parasympathetic high-frequency activity relative to the sham exposure. The MF exposure in the upper arm region significantly increased the brachial artery flow-mediated dilation compared to the sham exposure. Computer simulations of induced in situ electric fields indicated that the order-of-magnitude estimates of the peak values were 100-500 mV/m, depending on the exposure conditions. This study provides the first evidence that a 50 Hz MF can activate parasympathetic activity and thereby lead to increase vasodilation and blood flow via a nitric oxide-dependent mechanism. Trial registration: UMIN Clinical Trial Registry (CTR) UMIN000038834. The authors confirm that all ongoing and related trials for this drug/intervention are registered.

Neuroimaging of depression with diffuse optical tomography during repetitive transcranial magnetic stimulation

Repetitive transcranial magnetic stimulation (rTMS) is an effective and safe treatment for depression; however, its potential has likely been hindered due to non-optimized targeting, unclear ideal stimulation parameters, and lack of information regarding how the brain is physiologically responding during and after stimulation. While neuroimaging is ideal for obtaining such critical information, existing modalities have been limited due to poor resolutions, along with significant noise interference from the electromagnetic spectrum. In this study, we used a novel diffuse optical tomography (DOT) device in order to advance our understanding of the neurophysiological effects of rTMS in depression. Healthy and depressed subjects aged 18–70 were recruited. Treatment parameters were standardized with targeting of the left dorsolateral prefrontal cortex with a magnetic field intensity of 100% of motor threshold, pulse frequency of 10 per second, a 4 s stimulation time and a 26 s rest time. DOT imaging was simultaneously acquired from the contralateral dorsolateral prefrontal cortex. Six healthy and seven depressed subjects were included for final analysis. Hemoglobin changes and volumetric three-dimensional activation patterns were successfully captured. Depressed subjects were observed to have a delayed and less robust response to rTMS with a decreased volume of activation compared to healthy subjects. In this first-in-human study, we demonstrated the ability of DOT to safely and reliably capture and compare cortical response patterns to rTMS in depressed and healthy subjects. We introduced this emerging optical functional imaging modality as a novel approach to investigating targeting, new treatment parameters, and physiological effects of rTMS in depression.

Modulation of the prefrontal blood oxygenation response to intermittent theta-burst stimulation in depression: A sham-controlled study with functional near-infrared spectroscopy

OBJECTIVE

To better understand the neural mechanisms behind the effect of intermittent theta-burst stimulation (iTBS), we investigated how the prefrontal blood oxygenation response measured by changes in oxygenated haemoglobin (oxy-Hb) was modulated during a sham-controlled iTBS treatment course, and whether this was related to depressive symptom change.

METHODS

In this randomised, double-blind study, patients with ongoing treatment-resistant depression received either active (n = 18) or sham (n = 21) iTBS over the dorsomedial prefrontal cortex for ten to fifteen days with two sessions daily. Event-related functional near-infrared spectroscopy (fNIRS) was measured during each iTBS train, and resting-state oxy-Hb was compared before and after each iTBS session at the first, fifth, and last treatment day.

RESULTS

Patients receiving active iTBS had an increase of the event-related oxy-Hb response compared to the sham group on the fifth (bilateral prefrontal cortices p < .001) and last (left prefrontal p = .007, right prefrontal p = .025) treatment day. Resting-state analysis showed suppressed oxy-Hb change in active iTBS compared to sham iTBS on the last treatment day (p = .024). Oxy-Hb change was unrelated to depressive symptom change (p = .474).

CONCLUSIONS

This study describes a modulation of the blood oxygenation response over the prefrontal cortex that was built up during the course of active iTBS treatment in depression.

Effects of rTMS on the brain: is there value in variability?

The ability of repetitive transcranial magnetic stimulation (rTMS) to non-invasively induce neuroplasticity in the human cortex has opened exciting possibilities for its application in both basic and clinical research. Changes in the amplitude of motor evoked potentials (MEPs) elicited by single-pulse transcranial magnetic stimulation has so far provided a convenient model for exploring the neurophysiology of rTMS effects on the brain, influencing the ways in which these stimulation protocols have been applied therapeutically. However, a growing number of studies have reported large inter-individual variability in the mean MEP response to rTMS, raising legitimate questions about the usefulness of this model for guiding therapy. Although the increasing application of different neuroimaging approaches has made it possible to probe rTMS-induced neuroplasticity outside the motor cortex to measure changes in neural activity that impact other aspects of human behaviour, the high variability of rTMS effects on these measurements remains an important issue for the field to address. In this review, we seek to move away from the conventional facilitation/inhibition dichotomy that permeates much of the rTMS literature, presenting a non-standard approach for measuring rTMS-induced neuroplasticity. We consider the evidence that rTMS is able to modulate an individual's moment-to-moment variability of neural activity, and whether this could have implications for guiding the therapeutic application of rTMS.

Cortical Hemodynamic Response and Connectivity Modulated by Sub-threshold High-Frequency Repetitive Transcranial Magnetic Stimulation

Repetitive transcranial magnetic stimulation (rTMS) at sub-threshold intensity is a viable clinical strategy to enhance the sensory and motor functions of extremities by increasing or decreasing motor cortical excitability. Despite this, it remains unclear how sub-threshold rTMS modulates brain cortical excitability and connectivity. In this study, we applied functional near-infrared spectroscopy (fNIRS) to investigate the alterations in hemodynamic responses and cortical connectivity patterns that are induced by high-frequency rTMS at a sub-threshold intensity. Forty high-frequency (10 Hz) trains of rTMS at 90% resting motor threshold (RMT) were delivered through a TMS coil placed over 1–2 cm lateral from the vertex. fNIRS signals were acquired from the frontal and bilateral motor areas in healthy volunteers (n = 20) during rTMS administration and at rest. A significant reduction in oxygenated hemoglobin (HbO) concentration was observed in most defined regions of interest (ROIs) during the stimulation period (p < 0.05). Decreased functional connectivity within prefrontal areas as well as between symmetrical ROI-pairs was also observed in most participants during the stimulation (p < 0.05). Results suggest that fNIRS imaging is able to provide a reliable measure of regional cortical brain activation that advances our understanding of the manner in which sub-threshold rTMS affects cortical excitability and brain connectivity.

A Systematic Review of Integrated Functional Near-Infrared Spectroscopy (fNIRS) and Transcranial Magnetic Stimulation (TMS) Studies

Background: The capacity for TMS to elicit neural activity and manipulate cortical excitability has created significant expectation regarding its use in both cognitive and clinical neuroscience. However, the absence of an ability to quantify stimulation effects, particularly outside of the motor cortex, has led clinicians and researchers to pair noninvasive brain stimulation with noninvasive neuroimaging techniques. fNIRS, as an optical and wearable neuroimaging technique, is an ideal candidate for integrated use with TMS. Together, TMS+fNIRS may offer a hybrid alternative to "blind" stimulation to assess NIBS in therapy and research. Objective: In this systematic review, the current body of research into the transient and prolonged effects of TMS on fNIRS-based cortical hemodynamic measures while at rest and during tasks are discussed. Additionally, studies investigating the relation of fNIRS to measures of cortical excitability as produced by TMS-evoked Motor-Evoked-Potential (MEP) are evaluated. The aim of this review is to outline the integrated use of TMS+fNIRS and consolidate findings related to use of fNIRS to monitor changes attributed to TMS and the relationship of fNIRS to cortical excitability itself. Methods: Key terms were searched in PubMed and Web-of-Science to identify studies investigating the use of both fNIRS and TMS. Works from Google-Scholar and referenced works in identified papers were also assessed for relevance. All published experimental studies using both fNIRS and TMS techniques in the study methodology were included. Results: A combined literature search of neuroimaging and neurostimulation studies identified 53 papers detailing the joint use of fNIRS and TMS. 22/53 investigated the immediate effects of TMS at rest in the DLPFC and M1 as measured by fNIRS. 21/22 studies reported a significant effect in [HbO] for 40/54 stimulation conditions with 14 resulting an increase and 26 in a decrease. While 15/22 studies also reported [HbR], only 5/37 conditions were significant. Task effects of fNIRS+TMS were detailed in 16 studies, including 10 with clinical populations. Most studies only reported significant changes in [HbO] related measures. Studies comparing fNIRS to changes in MEP-measured cortical excitability suggest that fNIRS measures may be spatially more diffuse but share similar traits. Conclusion: This review summarizes the progress in the development of this emerging hybrid neuroimaging & neurostimulation methodology and its applications. Despite encouraging progress and novel applications, a lack of replicated works, along with highly disparate methodological approaches, highlight the need for further controlled studies. Interpretation of current research directions, technical challenges of TMS+fNIRS, and recommendations regarding future works are discussed.

Non-invasive brain stimulation in the modulation of cerebral blood flow after stroke: A systematic review of Transcranial Doppler studies

OBJECTIVE

Non-invasive brain stimulation (NIBS), such as repetitive TMS (rTMS) and transcranial direct current stimulation (tDCS), are promising neuromodulatory priming techniques to promote task-specific functional recovery after stroke. Despite promising results, clinical application of NIBS has been limited by high inter-individual variability. We propose that there is a possible influence of neuromodulation on cerebral blood flow (CBF), as neurons are spatially and temporally related to blood vessels. Transcranial Doppler (TCD), a clinically available non-invasive diagnostic tool, allows for evaluation of CBF velocity (CBFv). However, little is known about the role of neuromodulation on CBFv.

METHODS

A systematic review of literature to understand the effects of NIBS on CBFv using TCD in stroke was conducted.

RESULTS

Twelve studies fit our inclusion criteria and are included in this review. Our review suggested that CBFv and/or vasomotor reactivity maybe influenced by rTMS dosage (intensity and frequency) and the type of tDCS electrode montage.

CONCLUSION

There is limited evidence regarding the effects of NIBS on cerebral hemodynamics using TCD and the usefulness of TCD to capture changes in CBFv after NIBS is not evident from this review. We highlight the variability in the experimental protocols, differences in the applied neurostimulation protocols and discuss open questions that remain regarding CBF and neuromodulation.

SIGNIFICANCE

TCD, a clinically accessible tool, may potentially be useful to understand the interaction between cortical neuromodulation and CBFv.

Blood oxygenation changes resulting from subthreshold high frequency repetitive transcranial magnetic stimulation

Effects of high frequency repetitive transcranial magnetic stimulation (rTMS) with a subthreshold intensity on hemodynamic response in brain cortices (both motor and prefrontal cortices) was investigated using the functional near infrared spectroscopy (fNIRS) technique. FNIRS signals of the motor and prefrontal cortices were acquired in healthy volunteers (n=7) at rest and during rTMS intervention. A significant reduction in oxygenated hemoglobin (HbO) concentration during the entire stimulation process was observed from both motor and prefrontal cortices. Results showed that the fNIRS technique can provide a reliable measure of regional cortical brain activation that could be valuable in studying cortical excitability connectivity in combination with rTMS.

Neuroimaging Mechanisms of Therapeutic Transcranial Magnetic Stimulation for Major Depressive Disorder

Research into therapeutic transcranial magnetic stimulation (TMS) for major depression has dramatically increased in the last decade. Understanding the mechanism of action of TMS is crucial to improve efficacy and develop the next generation of therapeutic stimulation. Early imaging research provided initial data supportive of widely held assumptions about hypothesized inhibitory or excitatory consequences of stimulation. Early work also indicated that while TMS modulated brain activity under the stimulation site, effects at deeper regions, in particular, the subgenual anterior cingulate cortex, were associated with clinical improvement. Concordant with earlier findings, functional connectivity studies also demonstrated that clinical improvements were related to changes distal, rather than proximal, to the site of stimulation. Moreover, recent work suggests that TMS modulates and potentially normalizes functional relationships between neural networks. An important observation that emerged from this review is that similar patterns of connectivity changes are observed across studies regardless of TMS parameters. Though promising, we stress that these imaging findings must be evaluated cautiously given the widespread reliance on modest sample sizes and little implementation of statistical validation. Additional limitations included use of imaging before and after a course of TMS, which provided little insight into changes that might occur during the weeks of stimulation. Furthermore, as studies to date have focused on depression, it is unclear whether our observations were related to mechanisms of action of TMS for depression or represented broader patterns of functional brain changes associated with clinical improvement.

Evaluation of evoked responses to pulse-matched high frequency and intermittent theta burst transcranial magnetic stimulation using simultaneous functional near-infrared spectroscopy

Transcranial magnetic stimulation (TMS) is a noninvasive method used to excite or inhibit cortical activity for experimental, diagnostic, and therapeutic interventions. However, nonmotor regions of the brain targeted in TMS therapies, such as the dorsolateral prefrontal cortex (DLPFC), offer no extrinsic response to stimulation, resulting in a need for a practical method for the evaluation of treatment. We sought to determine the capability of a continuous-wave light emitting diodes (LED)-based functional near-infrared spectroscopy (fNIRS) system to measure evoked cortical hemoglobin changes in the DLPFC during the simultaneous application of TMS to the left-DLPFC under brief stimulation paradigms used in the clinic. Seventeen healthy participants received short TMS trains at F3 in four different stimulation conditions (single pulse, high frequency, intermittent theta burst, and sham) while adjacent fNIRS measurements were recorded. Ten 2-s trains of each stimulation type were delivered with an intertrial interval of 40 s. Results indicated that high-frequency stimulation produces a larger and more evident response than other measured conditions. These findings show that a continuous-wave LED-based fNIRS system can be used to measure TMS-evoked responses and that future TMS applications can benefit from concurrent assessment of localized cortical activation changes.

High frequency repetitive transcranial magnetic stimulation of the left dorsolateral prefrontal cortex for methamphetamine use disorders: A randomised clinical trial

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is a brain stimulation and modulation electrophysiological technique, it can change cortical excitability of target brain region, modulate neuron plasticity and brain connections. Previous researches indicated that rTMS could reduce cue-induced craving in drug addiction.

OBJECTIVE

In this study, we employed real and sham rTMS of the left dorsolateral prefrontal cortex (DLPFC) to test whether it could reduce cue-induced craving for methamphetamine (MA) and influence cognitive function in a randomised clinical trial.

METHODS

Thirty MA-addicted patients were randomized to receive 5 sessions of 8min sham or 10Hz rTMS to the left DLPFC. Subjects rated their craving at baseline, after exposed to MA-associated cues and after rTMS sessions.

RESULTS

Real rTMS over the left DLPFC reduced craving significantly after 5 sessions of rTMS as compared to sham stimulation. Furthermore, real rTMS improved verbal learning and memory and social cognition in MA-addicted patients.

CONCLUSIONS

The present study suggests that 10Hz rTMS of the left DLPFC may reduce craving and have no negative effects on cognitive function in MA-addicted patients, supporting the safety of rTMS in treating MA addiction.

5Hz Repetitive transcranial magnetic stimulation to left prefrontal cortex for major depression

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) to left prefrontal cortex at 10Hz is the most commonly utilized protocol for major depressive disorder (MDD). Published data suggests that left sided 5Hz rTMS may be efficacious and well tolerated.

OBJECTIVE

We analyzed outcomes in a naturalistic cohort of MDD patients who could not tolerate 10Hz rTMS and were routinely switched to 5Hz. We hypothesized that the efficacy of 5Hz rTMS would be equivalent to 10Hz.

METHODS

Records were reviewed for patients (n=98) who received 15 or more acute rTMS treatments. The sample was split based upon the frequency (10 or 5Hz) at which the majority of treatments were delivered. The Inventory of Depressive Symptoms (IDS-SR) and 9-Item Patient Health Questionnaire (PHQ-9) were used to evaluate outcomes.

RESULTS

Baseline IDS-SR was higher in the 5Hz (n=27) than in the 10Hz (n=71) group (p<.05), as was frequency of comorbid anxiety (p=.002). Depression outcomes did not differ between groups, and there were no differences in response or remission rates (all p>.1). Statistical power was sufficient to detect small group differences (d=.26).

LIMITATIONS

Open-label data in a naturalistic setting.

CONCLUSION

Outcomes associated with 5Hz rTMS did not differ from 10Hz, despite higher baseline depressive symptom severity and anxiety in 5Hz patients. 5Hz stimulation may be an alternative treatment option for patients unable to tolerate 10Hz rTMS.