An Investigation of Medial Temporal Lobe Changes and Cognition Following Antidepressant Response: A Prospective rTMS Study

The effect of repetitive transcranial magnetic stimulation on the Hamilton Depression Rating Scale-17 criterion in patients with major depressive disorder without psychotic features: a systematic review and meta-analysis of intervention studies

AIM

In line with the publication of clinical information related to the therapeutic process of repetitive transcranial magnetic stimulation (rTMS) and the updating of relevant treatment guidelines, the present meta-analysis study was designed and conducted to determine the effect of repetitive transcranial magnetic stimulation (rTMS) on the Hamilton Depression Rating Scale-17 (HDRS-17) criterion in patients with major depressive disorder (MDD) without psychotic features.

METHODS

In this study, a systematic search was conducted in electronic databases such as PubMed [Medline], Scopus, Web of Science, Embase, Ovid, Cochrane Library, and ClinicalTrials. gov using relevant keywords. The search period in this study was from January 2000 to January 2022, which was updated until May 2023. Randomized controlled trials (RCTs) that determined the effect of repetitive transcranial magnetic stimulation (rTMS) on the Hamilton Depression Rating Scale-17 (HDRS-17) criterion in patients with major depressive disorder (MDD) without psychotic features were included in the analysis. The quality of the included RCTs was assessed using the Cochrane Risk of Bias checklist. Statistical analyses were performed using STATA (Version 16) and RevMan (Version 5).

RESULTS

Following the combination of results from 16 clinical trial studies in the present meta-analysis, it was found that the mean Hamilton Depression Rating Scale-17 (HDRS-17) in patients with major depressive disorder (MDD) decreases by an average of 1.46 units (SMD: -1.46; % 95 CI: -1.65, -1.27, I square: 45.74%; P heterogeneity: 0.56). Subgroup analysis results indicated that the standardized mean difference of Hamilton Depression Rating Scale-17 (HDRS-17) varied based on the number of treatment sessions: patients receiving 10 or fewer repetitive transcranial magnetic stimulation (rTMS) sessions showed a mean Hamilton Depression Rating Scale-17 (HDRS-17) reduction of 2.60 units (SMD: -2.60; % 95 CI: -2.86, -2.33, I square: 55.12%; P heterogeneity: 0.55), while those receiving 11 to 20 sessions showed a mean Hamilton Depression Rating Scale-17 (HDRS-17) reduction of 0.28 units (SMD: -0.28; % 95 CI: -0.65, -0.09, I square: 39.91%; P heterogeneity: 0.89).

CONCLUSION

In conclusion, our meta-analysis demonstrates the efficacy of repetitive transcranial magnetic stimulation (rTMS) in reducing depressive symptoms in major depressive disorder (MDD) patients. The complex results of subgroup analysis revealed insight on the possible benefits of a more focused strategy with fewer sessions, as well as the impact of treatment session frequency. These findings add to our understanding of repetitive transcranial magnetic stimulation (rTMS) as a therapeutic intervention for the treatment of major depressive illnesses.

Efficacy and safety of transcranial magnetic stimulation on cognition in mild cognitive impairment, Alzheimer's disease, Alzheimer's disease-related dementias, and other cognitive disorders: a systematic review and meta-analysis

OBJECTIVE

We aim to analyze the efficacy and safety of TMS on cognition in mild cognitive impairment (MCI), Alzheimer's disease (AD), AD-related dementias, and nondementia conditions with comorbid cognitive impairment.

DESIGN

Systematic review, Meta-Analysis.

SETTING

We searched MEDLINE, Embase, Cochrane database, APA PsycINFO, Web of Science, and Scopus from January 1, 2000, to February 9, 2023.

PARTICIPANTS AND INTERVENTIONS

RCTs, open-label, and case series studies reporting cognitive outcomes following TMS intervention were included.

MEASUREMENT

Cognitive and safety outcomes were measured. Cochrane Risk of Bias for RCTs and MINORS (Methodological Index for Non-Randomized Studies) criteria were used to evaluate study quality. This study was registered with PROSPERO (CRD42022326423).

RESULTS

The systematic review included 143 studies (n = 5,800 participants) worldwide, encompassing 94 RCTs, 43 open-label prospective, 3 open-label retrospective, and 3 case series. The meta-analysis included 25 RCTs in MCI and AD. Collectively, these studies provide evidence of improved global and specific cognitive measures with TMS across diagnostic groups. Only 2 studies (among 143) reported 4 adverse events of seizures: 3 were deemed TMS unrelated and another resolved with coil repositioning. Meta-analysis showed large effect sizes on global cognition (Mini-Mental State Examination (SMD = 0.80 [0.26, 1.33], p = 0.003), Montreal Cognitive Assessment (SMD = 0.85 [0.26, 1.44], p = 0.005), Alzheimer's Disease Assessment Scale-Cognitive Subscale (SMD = -0.96 [-1.32, -0.60], p < 0.001)) in MCI and AD, although with significant heterogeneity.

CONCLUSION

The reviewed studies provide favorable evidence of improved cognition with TMS across all groups with cognitive impairment. TMS was safe and well tolerated with infrequent serious adverse events.

Treatment-Resistant Depression in Real-World Clinical Practice: A Systematic Literature Review of Data from 2012 to 2022

OBJECTIVE

Real-world evidence in treatment-resistant depression (TRD; commonly defined as non-response to ≥ 2 consecutive treatments at adequate dosage and duration) is lacking. A systematic literature review was conducted to understand disease burden and treatment outcomes for patients with TRD, studied in a real-world setting over the last decade.

DATA SOURCES

A literature search was conducted in May 2022 in MEDLINE, Embase, The Cochrane Libraries and PsycINFO, comprising studies published from 2012 to 2022. Bibliographies of all relevant identified systematic reviews and relevant conference proceedings from 2020 to 2022 were manually hand-searched.

STUDY SELECTION

Real-world studies, including cohort, cross-sectional, case-control, chart review and registry studies, published in English and reporting outcomes in adults with TRD, were included.

DATA EXTRACTION

Extracted data included study and baseline disease characteristics, treatment type, treatment response, clinical outcomes and health-related quality of life.

RESULTS

Twenty studies were included. Criteria for TRD varied, but patients typically experienced long-lasting depression (range 1.4 to 16.5 years). Across studies, mean disease severity scores demonstrated moderate to severe depression, reflecting a high burden of disease at baseline. Remission rates were typically low but generally increased with longer follow-up durations. However, the heterogeneity of interventions, follow-up durations (range 2 weeks to 9.4 years) and assessment tools precluded their quantitative synthesis. Studies were frequently limited by low sample size (range 14 to 411 patients) and health-related quality of life was infrequently assessed.

CONCLUSIONS

There is a lack of clinical consensus regarding the definition, assessment and monitoring of TRD in real-world practice. Nevertheless, TRD carries a high burden of illness and there is an unmet need for faster and more effective treatments. To better understand the personal burden of affected patients, future studies would benefit from standardisation of severity assessment and measures of treatment effectiveness, as well as greater consideration of health-related quality of life.

Effects of intermittent theta-burst transcranial magnetic stimulation on cognition and hippocampal volumes in bipolar depression

INTRODUCTION

Repetitive transcranial magnetic stimulation (TMS) is increasingly used to treat neurocognitive symptoms in mood disorders. Intermittent theta burst stimulation (iTBS) is a brief version of TMS that may preferentially target cognitive functions. This study evaluated whether iTBS leads to cognitive improvements and associated increased hippocampal volumes in bipolar depression.

METHODS

In a two-site double-blind randomised sham controlled trial (NCT02749006), 16 patients received active iTBS to the Left Dorsolateral Prefrontal Cortex (DLPF) and 15 patients received sham stimulation across four weeks. A composite neuropsychological score and declarative memory scores served as the cognitive outcomes. Hippocampal volumes were derived from T1 weighted MRI scans using the longitudinal ComBat method to harmonise data across sites.

RESULTS

No significant improvements were observed in any cognitive variables in the active relative to the sham group; however, there was a trend for increased left hippocampal volume in the former. Left hippocampal volume increases were associated with improvements in nonverbal memory in the active group.

CONCLUSIONS

Although cognitive improvements were not associated with iTBS, the finding that hippocampal volume increases were associated with memory improvement suggests there may be some level of prefrontal-temporal neuroplasticity that could support cognitive change in future studies of iTBS in bipolar disorder.

Traumatic brain injury and rTMS-ERPs: Case report and literature review

Currently, there are no cases of targeted, individualized repeated transcranial magnetic stimulation (rTMS) treatment based on event-related potential (ERPs) results showing the activation of functional brain regions. The identification and treatment of mild cognitive impairment after traumatic brain injury are challenging. rTMS has shown unique advantages in previous studies, with positive effects on noninvasive modulation and neuroplasticity after brain injury. The selection of the rTMS parameters and targets remains controversial. ERPs indicate the cortical activity involved in cognitive processing in patients. Therefore, this study proposes that ERPs can be used as biomarkers of cognitive recovery. The results of this study will guide the development of rTMS protocols for patient treatment. To help clinicians better apply rTMS and ERPs in combination, we conducted a relevant literature review and discussion, detailing the therapeutic mechanisms of the combination of ERPs and rTMS. This will facilitate the precise assessment and personalized treatment of such patients, improve the abnormal processing patterns of patients, and promote their return to life and society.

Brain volumetric correlates of electroconvulsive therapy versus transcranial magnetic stimulation for treatment-resistant depression

BACKGROUND

Electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS) are effective neuromodulation therapies for treatment-resistant depression (TRD). While ECT is generally considered the most effective antidepressant, rTMS is less invasive, better tolerated and leads to more durable therapeutic benefits. Both interventions are established device antidepressants, but it remains unknown if they share a common mechanism of action. Here we aimed to compare the brain volumetric changes in patients with TRD after right unilateral (RUL) ECT versus left dorsolateral prefrontal cortex (lDLPFC) rTMS.

METHODS

We assessed 32 patients with TRD before the first treatment session and after treatment completion using structural magnetic resonance imaging. Fifteen patients were treated with RUL ECT and seventeen patients received lDLPFC rTMS.

RESULTS

Patients receiving RUL ECT, in comparison with patients treated with lDLPFC rTMS, showed a greater volumetric increase in the right striatum, pallidum, medial temporal lobe, anterior insular cortex, anterior midbrain, and subgenual anterior cingulate cortex. However, ECT- or rTMS-induced brain volumetric changes were not associated with the clinical improvement.

LIMITATIONS

We evaluated a modest sample size with concurrent pharmacological treatment and without neuromodulation therapies randomization.

CONCLUSIONS

Our findings suggest that despite comparable clinical outcomes, only RUL ECT is associated with structural change, while rTMS is not. We hypothesize that structural neuroplasticity and/or neuroinflammation may explain the larger structural changes observed after ECT, whereas neurophysiological plasticity may underlie the rTMS effects. More broadly, our results support the notion that there are multiple therapeutic strategies to move patients from depression to euthymia.

Increased thalamic gray matter volume induced by repetitive transcranial magnetic stimulation treatment in patients with major depressive disorder

Purpose

Repetitive transcranial magnetic stimulation (rTMS) is an effective therapy in improving depressive symptoms in MDD patients, but the intrinsic mechanism is still unclear. In this study, we investigated the influence of rTMS on brain gray matter volume for alleviating depressive symptoms in MDD patients using structural magnetic resonance imaging (sMRI) data.

Methods

Patients with first episode, unmedicated patients with MDD (n = 26), and healthy controls (n = 31) were selected for this study. Depressive symptoms were assessed before and after treatment by using the HAMD-17 score. High-frequency rTMS treatment was conducted in patients with MDD over 15 days. The rTMS treatment target is located at the F3 point of the left dorsolateral prefrontal cortex. Structural magnetic resonance imaging (sMRI) data were collected before and after treatment to compare the changes in brain gray matter volume.

Results

Before treatment, patients with MDD had significantly reduced gray matter volumes in the right fusiform gyrus, left and right inferior frontal gyrus (triangular part), left inferior frontal gyrus (orbital part), left parahippocampal gyrus, left thalamus, right precuneus, right calcarine fissure, and right median cingulate gyrus compared with healthy controls (P < 0.05). After rTMS treatment, significant growth in gray matter volume of the bilateral thalamus was observed in depressed patients (P < 0.05).

Conclusion

Bilateral thalamic gray matter volumes were enlarged in the thalamus of MDD patients after rTMS treatment and may be the underlying neural mechanism for the treatment of rTMS on depression.

Relationship between nuclei-specific amygdala connectivity and mental health dimensions in humans

There has been increasing interest in using neuroimaging measures to predict psychiatric disorders. However, predictions usually rely on large brain networks and large disorder heterogeneity. Thus, they lack both anatomical and behavioural specificity, preventing the advancement of targeted interventions. Here we address both challenges. First, using resting-state functional magnetic resonance imaging, we parcellated the amygdala, a region implicated in mood disorders, into seven nuclei. Next, a questionnaire factor analysis provided subclinical mental health dimensions frequently altered in anxious-depressive individuals, such as negative emotions and sleep problems. Finally, for each behavioural dimension, we identified the most predictive resting-state functional connectivity between individual amygdala nuclei and highly specific regions of interest, such as the dorsal raphe nucleus in the brainstem or medial frontal cortical regions. Connectivity in circumscribed amygdala networks predicted behaviours in an independent dataset. Our results reveal specific relations between mental health dimensions and connectivity in precise subcortical networks.

Cognitive functioning as predictor and marker of response to repetitive transcranial magnetic stimulation in depressive disorders: A systematic review

OBJECTIVE

Cognitive performance in Major Depressive Disorder (MDD) is frequently impaired and related to functional outcomes. Repetitive Transcranial Magnetic Stimulation (rTMS) may exert its effects on MDD acting both on depressive symptoms and neurocognition. Furthermore, cognitive status could predict the therapeutic response of depressive symptoms to rTMS. However, cognitive performances as a predictor of rTMS response in MDD has not been thoroughly investigated. This review aims to evaluate the role of pre-treatment cognitive performance as a predictor of clinical response to rTMS, and the effects of rTMS on neurocognition in MDD.

METHOD

A systematic review of studies evaluating neurocognition in MDD as an outcome and/or predictor of response to rTMS was conducted using PubMed/Medline and Embase.

RESULTS

Fifty-eight articles were identified: 25 studies included neurocognition as a predictor of response to rTMS; 56 used cognitive evaluation as an outcome of rTMS. Baseline cognitive performance and cognitive improvements after rTMS predicted clinical response to rTMS. Moreover, rTMS improved cognition in MDD.

CONCLUSIONS

Cognitive assessment could predict improvement of depression in MDD patients undergoing rTMS and help selecting patients that could have beneficial effects from rTMS. A routine cognitive assessment might stratify MDD patients and track rTMS related cognitive improvement.

A pilot study of accelerated deep transcranial magnetic stimulation effects on cognitive functioning in patients diagnosed with treatment resistant major depressive disorder

The purpose of this study was to assess cognitive functioning in patients diagnosed with major depressive disorder (MDD) treated with two different accelerated deep transcranial magnetic stimulation (dTMS) modalities as an add-on to stable pharmacotherapy.A total of 32 adult psychiatric inpatients diagnosed with treatment resistant MDD were allocated by stratified randomization into two groups: a group treated with dTMS twice a day during 2 weeks, and a group treated with dTMS twice a day during 3 weeks. Clinical psychologists assessed participants´ cognitive functions (memory, visuospatial functioning, executive functions, psychomotor speed, verbal fluency) via a battery of instruments, after the inclusion, and by the end of treatment.Our findings showed mild to moderate improvements in the majority of administered tests measuring different cognitive functions, meaning that patients achieved significantly better results by the end of the treatment compared to baseline, regardless of the duration of the treatment (2 or 3 weeks). No adverse effects on cognition were observed. The results seem promising in the context of treating the cognitive symptoms associated with functional recovery of patients suffering from depression.

The therapeutic efficacy of transcranial magnetic stimulation in managing Alzheimer’s disease: A systemic review and meta-analysis

Background

Repetitive Transcranial Magnetic Stimulation (rTMS) is widely used to treat Alzheimer’s Disease. However, the effect of rTMS is still controversial. The purpose of the present study is to evaluate the effectiveness of rTMS on cognitive performance of AD patients.

Methods

We systematically searched relevant literatures in four major databases - PubMed, EMBASE, Web of Science, and the Cochrane Central Register of Controlled Trials [Central] before 28th April 2022. Both randomized controlled trials and cross-section studies that compared the therapeutic effect of rTMS with blank control or sham stimuli were included.

Results

A total of 14 studies involving 513 AD patients were finally included for meta-analysis. It was found that rTMS significantly improved global cognitive function (SMD = 0.24, 95%CI, 0.12 to 0.36, P = 0.0001) and daily living ability (IADL: SMD = 0.64, 95%CI, 0.21to 1.08, P = 0.004) in patients with AD, but did not show improvement in language, memory, executive ability, and mood. In further analyses, rTMS at 10 Hz, on a single target with 20 sessions of treatment was shown to produce a positive effect. In addition, improvement in cognitive functions lasted for at least 6 weeks (SMD = 0.67, 95%CI, 0.05 to 1.30,P = 0.04).

Conclusion

rTMS can improve the global cognition and daily living ability of AD patients. In addition, attention should be paid to the safety of rTMS in AD patients with seizures. Given the relatively small sample size, our results should be interpreted with caution.

Neurostructural Differences in Adolescents With Treatment-Resistant Depression and Treatment Effects of Transcranial Magnetic Stimulation

BACKGROUND

Despite its morbidity and mortality, the neurobiology of treatment-resistant depression (TRD) in adolescents and the impact of treatment on this neurobiology is poorly understood.

METHODS

Using automatic segmentation in FreeSurfer, we examined brain magnetic resonance imaging baseline volumetric differences among healthy adolescents (n = 30), adolescents with major depressive disorder (MDD) (n = 19), and adolescents with TRD (n = 34) based on objective antidepressant treatment rating criteria. A pooled subsample of adolescents with TRD were treated with 6 weeks of active (n = 18) or sham (n = 7) 10-Hz transcranial magnetic stimulation (TMS) applied to the left dorsolateral prefrontal cortex. Ten of the adolescents treated with active TMS were part of an open-label trial. The other adolescents treated with active (n = 8) or sham (n = 7) were participants from a randomized controlled trial.

RESULTS

Adolescents with TRD and adolescents with MDD had decreased total amygdala (TRD and MDD: -5%, P = .032) and caudal anterior cingulate cortex volumes (TRD: -3%, P = .030; MDD: -.03%, P = .041) compared with healthy adolescents. Six weeks of active TMS increased total amygdala volumes (+4%, P < .001) and the volume of the stimulated left dorsolateral prefrontal cortex (+.4%, P = .026) in adolescents with TRD.

CONCLUSIONS

Amygdala volumes were reduced in this sample of adolescents with MDD and TRD. TMS may normalize this volumetric finding, raising the possibility that TMS has neurostructural frontolimbic effects in adolescents with TRD. TMS also appears to have positive effects proximal to the site of stimulation.

Association of cognitive impairment and reduced cortical thickness in prefrontal cortex and anterior cingulate cortex with treatment-resistant depression

Accumulating evidence suggests the critical role of cortical thinning in the pathophysiology of major depressive disorder. However, the association of cortical thickness and cognitive impairment with treatment-resistant depression (TRD) has rarely been investigated. In total, 48 adult patients with TRD and 48 healthy controls were recruited and administered a series of neurocognitive and neuroimaging examinations, including 1-back and 2-back working memory tasks and brain magnetic resonance imaging (MRI). Whole-brain cortical thickness analysis was performed to investigate the differences in the cortical thickness between patients with TRD and controls. The patients had reduced cortical thickness in the frontal cortex, particularly at the left frontal pole, left inferior frontal cortex, and left anterior cingulate cortex, and left middle temporal cortex compared with the healthy controls. Moreover, in the 2-back working memory task, the cortical thickness in the left frontal pole and left anterior cingulate cortex was positively associated with mean error in the patients, but not in the controls. Reduced cortical thickness in the frontal pole and anterior cingulate cortex is associated with TRD and related cognitive impairment. Our study indicated the crucial effects of the frontal and temporal cortical thickness on the pathophysiology of TRD and cognitive impairment in patients with TRD.

Structural and functional biomarkers of efficacy of navigated repetitive transcranial magnetic stimulation in therapy for trigeminal neuralgia

Repetitive transcranial magnetic stimulation (rTMS) is an alternative treatment option for patients with drug-resistant trigeminal neuralgia (TN). However, the effect of rTMS is variable. The aim of this study was to find neuroimaging biomarkers of clinical efficacy of navigated rTMS. Seventeen patients with TN (14 women and 3 men, median age 56 years) received 10 sessions of high-frequency rTMS of the motor cortex contralateral to pain side. The data were analyzed for correlations between functional connectivity (FC), the grey matter (GM) volume and the reduction in pain intensity. Positive correlations were established between the reduction in average pain intensity and GM volume in caudate nuclei in both hemispheres (p(unc) = 0.03), both cerebellar hemispheres (p(unc) = 0.002) and the postcentral gyrus contralateral to pain side (p(unc) = 0.005); between the reduction in peak pain intensity and GM volume in the caudate nucleus contralateral to pain side (p(unc) = 0.04) and the cerebellar hemisphere ipsilateral to pain (p(unc) = 0.03). Significant positive correlations were discovered between the reduction in average pain intensity and FC between the thalamus contralateral to pain side, the postcentral gyrus and the insular operculum (both ipsilateral to pain side; (p(FWE) = 0.018), as well as between the cingulate cortex and the anterior cingulate cortex ipsilateral to pain (p(FWE) = 0.017), between the contralateral subcallosal gyrus and the cerebellar hemisphere ipsilateral to pain (p(FWE) = 0.018). A negative correlation was established for FC between the contralateral putamen and the occipital lobes in both hemispheres (p(FWE) = 0.001). Our findings may spur the development of individual predictors of rTMS efficacy in patients with chronic pain.

The intervention, the patient and the illness - Personalizing non-invasive brain stimulation in psychiatry

Current hypotheses on the therapeutic action of non-invasive brain stimulation (NIBS) in psychiatric disorders build on the abundant data from neuroimaging studies. This makes NIBS a very promising tool for developing personalized interventions within a precision medicine framework. NIBS methods fundamentally vary in their neurophysiological properties. They comprise repetitive transcranial magnetic stimulation (rTMS) and its variants (e.g. theta burst stimulation - TBS) as well as different types of transcranial electrical stimulation (tES), with the largest body of evidence for transcranial direct current stimulation (tDCS). In the last two decades, significant conceptual progress has been made in terms of NIBS targets, i.e. from single brain regions to neural circuits and to functional connectivity as well as their states, recently leading to brain state modulating closed-loop approaches. Regarding structural and functional brain anatomy, NIBS meets an individually unique constellation, which varies across normal and pathophysiological states. Thus, individual constitutions and signatures of disorders may be indistinguishable at a given time point, but can theoretically be parsed along course- and treatment-related trajectories. We address precision interventions on three levels: 1) the NIBS intervention, 2) the constitutional factors of a single patient, and 3) the phenotypes and pathophysiology of illness. With examples from research on depressive disorders, we propose solutions and discuss future perspectives, e.g. individual MRI-based electrical field strength as a proxy for NIBS dosage, and also symptoms, their clusters, or biotypes instead of disorder focused NIBS. In conclusion, we propose interleaved research on these three levels along a general track of reverse and forward translation including both clinically directed research in preclinical model systems, and biomarker guided controlled clinical trials. Besides driving the development of safe and efficacious interventions, this framework could also deepen our understanding of psychiatric disorders at their neurophysiological underpinnings.

Predicting Response to Brain Stimulation in Depression: a Roadmap for Biomarker Discovery

PURPOSE OF REVIEW

Clinical response to brain stimulation treatments for depression is highly variable. A major challenge for the field is predicting an individual patient's likelihood of response. This review synthesises recent developments in neural predictors of response to targeted brain stimulation in depression. It then proposes a framework to evaluate the clinical potential of putative 'biomarkers'.

RECENT FINDINGS

Largely, developments in identifying putative predictors emerge from two approaches: data-driven, including machine learning algorithms applied to resting state or structural neuroimaging data, and theory-driven, including task-based neuroimaging. Theory-driven approaches can also yield mechanistic insight into the cognitive processes altered by the intervention.

SUMMARY

A pragmatic framework for discovery and testing of biomarkers of brain stimulation response in depression is proposed, involving (1) identification of a cognitive-neural phenotype; (2) confirming its validity as putative biomarker, including out-of-sample replicability and within-subject reliability; (3) establishing the association between this phenotype and treatment response and/or its modifiability with particular brain stimulation interventions via an early-phase randomised controlled trial RCT; and (4) multi-site RCTs of one or more treatment types measuring the generalisability of the biomarker and confirming the superiority of biomarker-selected patients over randomly allocated groups.

Development of Neuroimaging-Based Biomarkers in Major Depression

A leading goal in the field of biological psychiatry for depression is to find a promising diagnostic biomarker and selection of specific psychiatric treatment mode that is most likely to benefit patients with depression. Recent neuroimaging studies have characterized the pathophysiology of major depressive disorder (MDD) with functional and structural alterations in the neural circuitry involved in emotion or reward processing. Particularly, structural and functional magnetic resonance imaging (MRI) studies have reported that the brain structures deeply involved in emotion regulation or reward processing including the amygdala, prefrontal cortex (PFC), anterior cingulate cortex (ACC), ventral striatum, and hippocampus are key regions that provide useful information about diagnosis and treatment outcome prediction in MDD. For example, it has been consistently reported that elevated activity of the ACC is associated with better antidepressant response in patients with MDD. This chapter will discuss a growing body of evidence that suggests that diagnosis or prediction of outcome for specific treatment can be assisted by a neuroimaging-based biomarker in MDD.

Longitudinal effects of rTMS on neuroplasticity in chronic treatment-resistant depression

Major depressive disorder (MDD) is amongst the most prevalent of psychiatric disorders. Unfortunately, a third of patients will not respond to conventional treatments and suffer from treatment-resistant depression (TRD). Repetitive transcranial magnetic stimulation (rTMS) has been proven effective in treating TRD. The research suggests that rTMS acts via neuroplastic effects on the brain, which can be measured by changes in hippocampal and amygdala volume as well as cortical thickness. This sham-controlled study investigates longitudinal effects of rTMS on the volumes of the hippocampus and amygdala and cortical thickness in patients with chronic TRD. 31 patients received 20 sessions of high-frequency rTMS (N = 15) or sham treatment (N = 16) over the left dorsolateral prefrontal cortex during 4 consecutive weeks. Using structural magnetic resonance imaging, we investigated longitudinal treatment effects on hippocampus and amygdala volume as well as thickness of the paralimbic cortex. We found no clinical differences between the active and sham rTMS group. Longitudinal changes in hippocampal and amygdala volume did not differ significantly, although males showed a significant decrease in left amygdala volume, irrespective of treatment group. Changes in cortical thickness of the paralimbic cortex differed significantly between the active and sham groups. Most notably, the increase in cortical thickness of the isthmus of the left cingulate gyrus was greater in the active as compared to the sham rTMS group. Our data suggest that rTMS can induce neuroplastic changes, particularly in cortical thickness, independent of treatment response. We also found longitudinal changes in amygdala volume in males. For clinical effects to follow these neuroplastic effects, more intensive rTMS treatment might be needed in chronically depressed patients.Trial registration number: ISRCTN 15535800, registered on 29-06-2017.

Precision non-implantable neuromodulation therapies: a perspective for the depressed brain

Current first-line treatments for major depressive disorder (MDD) include pharmacotherapy and cognitive-behavioral therapy. However, one-third of depressed patients do not achieve remission after multiple medication trials, and psychotherapy can be costly and time-consuming. Although non-implantable neuromodulation (NIN) techniques such as transcranial magnetic stimulation, transcranial direct current stimulation, electroconvulsive therapy, and magnetic seizure therapy are gaining momentum for treating MDD, the efficacy of non-convulsive techniques is still modest, whereas use of convulsive modalities is limited by their cognitive side effects. In this context, we propose that NIN techniques could benefit from a precision-oriented approach. In this review, we discuss the challenges and opportunities in implementing such a framework, focusing on enhancing NIN effects via a combination of individualized cognitive interventions, using closed-loop approaches, identifying multimodal biomarkers, using computer electric field modeling to guide targeting and quantify dosage, and using machine learning algorithms to integrate data collected at multiple biological levels and identify clinical responders. Though promising, this framework is currently limited, as previous studies have employed small samples and did not sufficiently explore pathophysiological mechanisms associated with NIN response and side effects. Moreover, cost-effectiveness analyses have not been performed. Nevertheless, further advancements in clinical trials of NIN could shift the field toward a more “precision-oriented” practice.

[Neuronal effects and biomarkers of antidepressant treatments : Current review from the perspective of neuroimaging]

Depression is one of the most frequent and disabling mental disorders worldwide and is accompanied by a severe impairment in the quality of life. There are numerous imaging studies showing differences in the volume of gray and white brain matter and function between patients suffering from depression and healthy controls. Neuroimaging studies show that pharmacotherapy and electroconvulsive therapy are accompanied by an increase of hippocampal gray matter volume while as a result of psychotherapy activity changes in the anterior cingulate cortex (ACC) have repeatedly been reported. By the identification of neuroanatomical markers, baseline volumes of the ACC have also been shown to be associated with therapy response to all treatments. The identification of such neuronal biomarkers in combination with machine learning techniques provide a promising step towards a neurobiologically based application for the prediction of treatment response.

Structural network integrity of the central executive network is associated with the therapeutic effect of rTMS in treatment resistant depression

Repetitive transcranial magnetic stimulation (rTMS) is a first-line option for treatment-resistant depression (TRD), but prediction of treatment outcome remains a clinical challenge. The present study aimed to compare structural and functional covariance networks (SCNs and FCNs) between remitters and nonremitters. We determined the predictive capacities of SCNs and FCNs to discriminate the two groups. Fifty TRD patients underwent a course of rTMS to the left dorsolateral prefrontal cortex. They were categorized into remitters (n = 22) and nonremitters (n = 28) based on HDRS≤7 at the end of treatment. Baseline structural and functional magnetic imaging (sMRI and fMRI) of the patients and 42 healthy controls were collected. SCNs and FCNs were defined based on structural and functional covariance of gray mater volume (GMV) and fractional amplitude of low-frequency fluctuations (fALFF) from sMRI and fMRI, respectively. Structural/functional network integrity of these networks (default mode network [DMN], central executive network [CEN] and salience network [SN]) were compared between the three groups. In patients, associations between SCNs and FCNs with clinical improvements were studied using linear correlation analysis. Receiver-operating characteristic (ROC) analysis was conducted to confirm the utility of the SCNs and FCNs in classifying clinical sub-groups. Nonremitters exhibited lower structural integrity in CEN than remitters and controls. Higher structural integrity of CEN was related to clinical improvement (r = 0.423, p = .002), and structural integrity distinguished remitters and nonremitters with a fairly high accuracy (AUC = 0.71, p = .008). No group differences or correlation with clinical changes were found in FCNs. Results suggest the CEN may play a role mediating clinical improvement in rTMS for depression. Structural covariance networks may be features to consider in prediction of clinical improvement.

Major Depressive Disorder in Neuroimaging: What is Beyond Fronto-limbic Model?

Background:

The major depressive disorder (MDD) is a chronic illness with major manifestations in cognitive, social and occupational functions. The pathophysiological model is an intrigue issue for scientists to understand the origin of MDD.

Objective:

In the beginning, the cortico-limbic-striato-pallidal-thalamic model has been proposed to link the clinical symptoms with the abnormalities in brain structure and function. However, the model is still evolving due to recent advances in the neuroimaging techniques, especially for functional magnetic resonance imaging (fMRI). The recent findings in the fMRI studies in MDD showed the importance of fronto-limbic model for the modulations between cognitive function and primitive and negative emotions.

Method:

This review will focus on the literature of fMRI studies in MDD with findings not in the fronto-limbic structures.

Results:

Additional regions beyond the fronto-limbic model have been observed in some literature of MDD. Some regions in the parietal, temporal and occipital lobes have been shown with the alterations in gray matter, white matter and brain function. The importance of sensory detection, visuospatial function, language reception, motor response and emotional memories in these regions might provide the clues to understand the cognitive misinterpretations related to altered reception of outside information, behavioral responses related to biased cognition and emotional memories and clinical symptoms related to the significant alterations of interactions between different brain regions.

Conclusion:

Future studies to establish a more comprehensive model for MDD will be warranted, especially for the model beyond the fronto-limbic structures.

Depression related cerebral pathology and its relationship with cognitive functioning: A systematic review

BACKGROUND

Depression's relationship with cerebral abnormalities and cognitive decline is temporally dynamic. Despite clear clinical utility, understanding depression's effect on cerebral structures, cognitive impairment and the interaction between these symptoms has had limited consideration.

METHODS

This review summarised studies examining a clinical depression diagnosis or validated scales measuring depressive symptoms, data concerning amyloid-beta (Aβ) levels, brain structure and function focusing on hippocampal alterations, or white matter hyperintensities (WMH), and at least one validated neuropsychological test. Online database searches of: PsycINFO, EMBASE, MEDLINE, and Scopus were conducted to identify potential articles.

RESULTS

While depression was consistently associated with cross-sectionally cognitive decline across multiple domains, the neuropathological basis of this dysfunction remained unclear. Hippocampal, frontal, and limbic dysfunction as well as cortical thinning, WMH, and Aβ burden all provide inconsistent findings, likely due to depression subtypes. The consistency of these findings additionally decreases when examining this relationship longitudinally, as these results are further confounded by pre-dementia states. The therapeutic interventions examined were more efficacious in the younger compared with the older samples, who were characterised by greater WMH and Aβ burden.

LIMITATIONS

The limited number of longitudinal and interventional studies in addition to the heterogeneity of the samples restricts their generalisability.

CONCLUSIONS

Symptomatological differences between early-onset and late-onset depression (EOD and LOD) appear crucial in understanding whether late-life depression is the primary or secondary source of cerebral pathology. Though severe cognitive impairments and clearer neuropathological underpinnings are more characteristic of LOD than EOD, the inconsistency of valid biomarkers remains problematic.

Structural changes in the hippocampus as a biomarker for cognitive improvements in neuropsychiatric disorders: A systematic review

Cognitive impairments are a core feature of several neuropsychiatric disorders. A common biomarker for pro-cognitive effects may provide a much-needed tool to select amongst candidate treatments targeting cognition. The hippocampus is a promising biomarker for target-engagement due to the illness-associated morphological hippocampal changes across unipolar disorder (UD), bipolar disorder (BD) and schizophrenia (SCZ). Following the PRISMA guidelines, we searched PubMed and Embase, for clinical trials targeting cognition across neuropsychiatric disorders, with longitudinal structural magnetic resonance imaging (MRI) measures of the hippocampus. Five randomized and three open-label trials were included. Hippocampal volume increases were associated with treatment-related cognitive improvement following treatment with erythropoietin across UD, BD and SCZ, lithium treatment in BD and aerobic exercise in SCZ. Conversely, an exercise intervention in UD showed no effect on hippocampal volume or cognition. Together, these observations point to hippocampal volume change as a putative biomarker-model for cognitive improvement. Future cognition trials are encouraged to include MRI assessments pre- and post-treatment to assess the validity of hippocampal changes as a biomarker for pro-cognitive effects.

rTMS ameliorated depressive-like behaviors by restoring HPA axis balance and prohibiting hippocampal neuron apoptosis in a rat model of depression

Repetitive transcranial magnetic stimulation (rTMS) has been widely used to treat depression. The mechanistic basis for the effects of rTMS is not well understood, although previous studies have suggested that it involves the regulation of hypothalamic-pituitary-adrenocortical (HPA) axis and protection of hippocampal neurons. We investigated this in the present study using a chronic unpredictable mild stress (CUMS) paradigm in Sprague-Dawley rats. The rats were subjected to rTMS for 15 consecutive days, and body weight, sucrose consumption, and locomotor activity were evaluated. B cell lymphoma-2-associated X protein (Bax) expression was assessed by immunohistochemistry; cell morphology was examined by Nissl staining; and adrenocorticotropic hormone (ACTH) and cortisol (CORT) levels in the hippocampus were measured by enzyme-linked immunosorbent assay. CUMS decreased body weight and sucrose consumption in rats along with horizontal/vertical distance traveled in the open field test. Rats subjected to CUMS also showed increased levels of Bax as well as ACTH and CORT; the hippocampal neurons in these animals had abnormal morphology and were reduced in number. rTMS reversed these changes and improved depression-like behaviors. Thus, rTMS abrogates the loss of hippocampal neurons and restores the balance of the HPA axis in the treatment of depression.

How Does Repetitive Transcranial Magnetic Stimulation Influence the Brain in Depressive Disorders?: A Review of Neuroimaging Magnetic Resonance Imaging Studies

OBJECTIVE

Repetitive transcranial magnetic stimulation (rTMS) is a nonpharmacological technique used to stimulate the brain. It is a safe and proven alternative tool to treat resistant major depressive disorders (MDDs). Neuroimaging studies suggest a wide corticolimbic network is involved in MDDs. We researched observable changes in magnetic resonance imaging induced by rTMS to clarify the operational mechanism.

METHODS

A systematic search of the international literature was performed using PubMed and Embase, using papers published up to January 1, 2017. The following MESH terms were used: (depression or major depressive disorder) and (neuroimaging or MRI) and (rTMS or repetitive transcranial magnetic stimulation). We searched the databases using a previously defined strategy to identify potentially eligible studies.

RESULTS

Both structural and functional changes were observed on magnetic resonance imagings performed before and after rTMS. Various areas of the brain were impacted when rTMS was used. Although the results were very heterogeneous, a pattern that involved the anterior cingulate cortex and the prefrontal cortex emerged. These are known to be regions of interest in MDDs. However, the various parameters used in rTMS make any generalization difficult.

CONCLUSIONS

Repetitive transcranial magnetic stimulation helps to treat MDDs with good efficacy. Its effect on the brain, as observed in several neuroimaging studies, seems to impact on the structural and functional features of several networks and structures involved in major depressive disorders.

Neuroimaging biomarkers as predictors of treatment outcome in Major Depressive Disorder

BACKGROUND

Current practice for selecting pharmacological and non-pharmacological antidepressant treatments has yielded low response and remission rates in Major Depressive Disorder (MDD). Neuroimaging biomarkers of brain structure and function may be useful in guiding treatment selection by predicting response vs. non-response outcomes.

METHODS

In this review, we summarize data from studies examining predictors of treatment response using structural and functional neuroimaging modalities, as they pertain to pharmacotherapy, psychotherapy, and stimulation treatment strategies. A literature search was conducted in OVID Medline, EMBASE, and PsycINFO databases with coverage from January 1990 to January 2017.

RESULTS

Several imaging biomarkers of therapeutic response in MDD emerged: frontolimbic regions, including the prefrontal cortex, anterior cingulate cortex, hippocampus, amygdala, and insula were regions of interest. Since these sub-regions are implicated in the etiology of MDD, their association with response outcomes may be the result of treatments having a normalizing effect on structural or activation abnormalities.

LIMITATIONS

The direction of findings is inconsistent in studies examining these biomarkers, and variation across 'biotypes' within MDD may account for this. Limitations in sample size and differences in methodology likely also contribute.

CONCLUSIONS

The identification of accurate, reliable neuroimaging biomarkers of treatment response holds promise toward improving treatment outcomes and reducing burden of illness for patients with MDD. However, before these biomarkers can be translated into clinical practice, they will need to be replicated and validated in large, independent samples, and integrated with data from other biological systems.

Rostral anterior cingulate cortex is a structural correlate of repetitive TMS treatment response in depression

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is an effective treatment for medication-refractory major depression, yet the mechanisms of action for this intervention are poorly understood. Here we investigate cerebral cortex thickness as a possible biomarker of rTMS treatment response.

METHODS

Longitudinal change in cortical thickness is evaluated relative to clinical outcomes across 48 participants in 2 cohorts undergoing left dorsolateral prefrontal cortex rTMS as a treatment for depression.

RESULTS

Our results reveal changes in thickness in a region of the left rostral anterior cingulate cortex that correlate with clinical response, with this region becoming thicker in patients who respond favorably to rTMS and thinner in patients with a less favorable response. Moreover, the baseline cortical thickness in this region correlates with rTMS treatment response - those patients with thinner cortex before treatment tended to have the most clinical improvement.

CONCLUSIONS

This study is the first analysis of longitudinal cortical thickness change with rTMS as a treatment for depression with similar results across two cohorts. These results support further investigation into the use of structural MRI as a possible biomarker of rTMS treatment response.

Thioredoxin is not a marker for treatment-resistance depression but associated with cognitive function: An rTMS study

Elevated oxidative stress is known to play an important role in development of depression and cognitive dysfunction. To date, thioredoxin (TRX), an antioxidant protein, has been investigated as a marker for psychiatric disorders such as schizophrenia, bipolar disorder and autism but its relationship with depression is yet to be unknown. The aim of this study is to detect the TRX levels in patients with treatment-resistant depression (TRD), analyse the effect of rTMS (repetitive transcranial magnetic stimulation) application on TRX levels and display the relationship of TRX with cognitive areas. This study included 27 treatment-resistant unipolar depression patients and 29 healthy subjects. Patients were evaluated by Hamilton Depression Scale (HDRS), Hamilton Anxiety Scale (HARS) and Montreal Cognitive Assessment (MoCA) before and after rTMS application. 23 of TRD patients were applied high-frequency rTMS over left DLPFC for 2 to 4weeks and plasma TRX levels of patients and healthy subjects were measured. No significant difference was determined between the TRX levels of patients and healthy subjects (p>0.05). After rTMS application there were significant decrease in severity of depression (p<0.001) and anxiety (p<0.001), and explicit improvement in cognitive areas (delayed memory, visual-spatial/executive abilities and language points) (all p<0.05). No difference was detected in TRX levels of the patients after rTMS application (p>0.005). High language scores of the patients were found to be associated with high TRX levels (p<0.005). Our study indicates that TRX levels cannot be used as a marker for TRD or rTMS treatment in TRD. In spite of this TRX levels have a positive correlation with language functions of the patients of TRD. More extensive studies are required to clarify the mechanism of action of TRX and the effect of TRX on cognitive functions.

Lateralized hippocampal volume increase following high-frequency left prefrontal repetitive transcranial magnetic stimulation in patients with major depression

AIM

Repetitive transcranial magnetic stimulation (rTMS) has been applied as a treatment for patients with treatment-resistant depression in recent years, and a large body of evidence has demonstrated its therapeutic efficacy through stimulating neuronal plasticity. The aim of this study was to investigate structural alterations in the hippocampus (HIPP) and amygdala (AM) following conventional rTMS in patients with depression.

METHODS

Twenty-eight patients with depression underwent 10 daily 20-Hz left prefrontal rTMS over 2 weeks. The left dorsolateral prefrontal cortex (DLPFC) was identified using magnetic resonance imaging-guided neuronavigation prior to stimulation. Magnetic resonance imaging scans were obtained at baseline and after the completion of rTMS sessions. The therapeutic effects of rTMS were evaluated with the 17-item Hamilton Depression Rating Scale (HAM-D₁₇ ), and the volumes of the HIPP and AM were measured by a manual tracing method.

RESULTS

Statistical analyses revealed a significant volume increase in the left HIPP (+3.4%) after rTMS but no significant volume change in the AM. No correlation was found between the left HIPP volume increase and clinical improvement, as measured by the HAM-D₁₇ .

CONCLUSION

The present study demonstrated that conventional left prefrontal rTMS increases the HIPP volume in the stimulated side, indicating a remote neuroplastic effect through the cingulum bundle.

Functional Recovery in Major Depressive Disorder: Providing Early Optimal Treatment for the Individual Patient

Major depressive disorder is an often chronic and recurring illness. Left untreated, major depressive disorder may result in progressive alterations in brain morphometry and circuit function. Recent findings, however, suggest that pharmacotherapy may halt and possibly reverse those effects. These findings, together with evidence that a delay in treatment is associated with poorer clinical outcomes, underscore the urgency of rapidly treating depression to full recovery. Early optimized treatment, using measurement-based care and customizing treatment to the individual patient, may afford the best possible outcomes for each patient. The aim of this article is to present recommendations for using a patient-centered approach to rapidly provide optimal pharmacological treatment to patients with major depressive disorder. Offering major depressive disorder treatment determined by individual patient characteristics (e.g., predominant symptoms, medical history, comorbidities), patient preferences and expectations, and, critically, their own definition of wellness provides the best opportunity for full functional recovery.

Microstructural brain abnormalities in medication-free patients with major depressive disorder: a systematic review and meta-analysis of diffusion tensor imaging

BACKGROUND

Multiple meta-analyses of diffusion tensor imaging (DTI) studies have reported impaired white matter integrity in patients with major depressive disorder (MDD). However, owing to inclusion of medicated patients in these studies, it is difficult to conclude whether these reported alterations are associated with MDD or confounded by medication effects. A meta-analysis of DTI studies on medication-free (medication-naive and medication washout) patients with MDD would therefore be necessary to disentangle MDD-specific effects.

METHODS

We analyzed white matter alterations between medication-free patients with MDD and healthy controls using anisotropic effect size-signed differential mapping (AES-SDM). We used DTI query software for fibre tracking.

RESULTS

Both pooled and subgroup meta-analyses in medication washout patients showed robust fractional anisotropy (FA) reductions in white matter of the right cerebellum hemispheric lobule, body of the corpus callosum (CC) and bilateral superior longitudinal fasciculus III (SLF III), whereas FA reductions in the genu of the CC and right anterior thalamic projections were seen in only medication-naive patients. Fibre tracking showed that the main tracts with observed FA reductions included the right cerebellar tracts, body of the CC, bilateral SLF III and arcuate fascicle.

LIMITATIONS

The analytic techniques, patient characteristics and clinical variables of the included studies were heterogeneous; we could not exclude the effects of nondrug therapies owing to a lack of data.

CONCLUSION

By excluding the confounding influences of current medication status, findings from the present study may provide a better understanding of the underlying neuropathology of MDD.

New Treatment Strategies of Depression: Based on Mechanisms Related to Neuroplasticity

Major depressive disorder is a severe and complex mental disorder. Impaired neurotransmission and disrupted signalling pathways may influence neuroplasticity, which is involved in the brain dysfunction in depression. Traditional neurobiological theories of depression, such as monoamine hypothesis, cannot fully explain the whole picture of depressive disorders. In this review, we discussed new treatment directions of depression, including modulation of glutamatergic system and noninvasive brain stimulation. Dysfunction of glutamatergic neurotransmission plays an important role in the pathophysiology of depression. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has rapid and lasting antidepressive effects in previous studies. In addition to ketamine, other glutamatergic modulators, such as sarcosine, also show potential antidepressant effect in animal models or clinical trials. Noninvasive brain stimulation is another new treatment strategy beyond pharmacotherapy. Growing evidence has demonstrated that superficial brain stimulations, such as transcranial magnetic stimulation, transcranial direct current stimulation, cranial electrotherapy stimulation, and magnetic seizure therapy, can improve depressive symptoms. The antidepressive effect of these brain stimulations may be through modulating neuroplasticity. In conclusion, drugs that modulate neurotransmission via NMDA receptor and noninvasive brain stimulation may provide new directions of treatment for depression. Furthermore, exploring the underlying mechanisms will help in developing novel therapies for depression in the future.

Practical application of the neuroregenerative properties of ketamine: real world treatment experience

While controversial, ketamine has emerged as an effective treatment for refractory depression. Serial infusions have been performed 3 times per week, but our practical experience has challenged this precept concerning infusion frequency. Depression is associated with neuron loss, reduced synapse numbers, and dearborization of dendrites. Ketamine appears to potently induce mechanisms which reverse these neurodegenerative processes. Ketamine not only blocks the glutamate receptor, it activates eukaroyotic elongation factor 2 (eEF2). This, in turn, activates brain-derived neurotrophic factor (BDNF) protein synthesis. This is thought to underlie ketamine's enduring benefits. In addition, ketamine alters glycogen synthase kinase-3 (GSK-3) phosphorylation, probably responsible for its rapid antidepressant effect. Notably, inhibition of the BDNF receptor does not block the immediate benefits of ketamine, but does prevent the enduring effects. Neuro-Luminance Ketamine Infusion Centers have been treating patients with serial ketamine infusions for over three years. Our methods differ from what is often reported, as we perform infusions only once per week and generally do not perform more than five infusions. Data from 100 patients showed that 80% of the patients responded. The baseline Quick Inventory of Depressive Symptomatology-Self Report (QIDS-SR) score was 17.8 ± 2.8. Responders to ketamine showed a drop in QIDS-SR score of 10.8 ± 3.5, while non-responders showed a 0.8 ± 1.8 change. Moreover, they often had persistent benefits over several months. Recently, it was proposed that psychotomimetic effects are necessary during a ketamine infusion to yield effective antidepressant benefits. Yet, only one patient in our clinic has experienced hallucinations in three years. Nevertheless, 80% of our patients show clinical improvement. Further studies of clinical methods for ketamine infusion therapy are encouraged.

Transcranial Magnetic Stimulation of Left Dorsolateral Prefrontal Cortex Induces Brain Morphological Changes in Regions Associated with a Treatment Resistant Major Depressive Episode: An Exploratory Analysis

BACKGROUND

Repetitive transcranial magnetic stimulation (TMS) is an FDA-approved antidepressant treatment but little is known of its mechanism of action. Specifically, downstream effects of TMS remain to be elucidated.

OBJECTIVE/HYPOTHESIS

This study aims to identify brain structural changes from TMS treatment of a treatment resistant depressive episode through an exploratory analysis.

METHODS

Twenty-seven subjects in a DSM-IV current major depressive episode and on a stable medication regimen had a 3T magnetic resonance T1 structural scan before and after five weeks of standard TMS treatment to the left dorsolateral prefrontal cortex. Twenty-seven healthy volunteer (HVs) subjects had the same brain MRI acquisition. Voxel-based morphometry was performed using high dimensional non-linear diffusomorphic anatomical registration (DARTEL).

RESULTS

Six clusters of gray matter volume (GMV) that were lower in pre-treatment MRIs of depressed subjects than in HVs. GMV in four of these regions increased in MDD after TMS treatment by 3.5-11.2%. The four brain regions that changed with treatment were centered in the left anterior cingulate cortex, the left insula, the left superior temporal gyrus and the right angular gyrus. Increases in the anterior cingulate GMV with TMS correlated with improvement in depression severity.

CONCLUSIONS

To our knowledge, this is the first study of brain structural changes during TMS treatment of depression. The affected brain areas are involved in cognitive appraisal, decision-making and subjective experience of emotion. These effects may have potential relevance for the antidepressant action of TMS.

The effects of repetitive transcranial magnetic stimulation on cognitive performance in treatment-resistant depression. A systematic review

BACKGROUND

Major depressive disorder (MDD) is a disabling illness associated with significant functional and psychosocial impairment. Although many psychopharmacological agents are currently available for its treatment, many MDD patients suffer from treatment-resistant depression (TRD).

METHODS

A systematic review of the current literature (Pubmed/Medline, Scopus and ScienceDirect search) has been conducted with the primary aim to investigate the role of repetitive transcranial magnetic stimulation (rTMS) in improving neurocognition in patients with TRD. Studies were included according to the following criteria: (a) being an original paper in a peer-reviewed journal and (b) having analyzed the effect of rTMS on neurocognitive functioning in TRD.

RESULTS

The combined search strategy yielded a total of 91 articles, of which, after a complete analysis, 22 fulfilled our inclusion criteria. Based on the main findings, most of the selected studies suggested the existence of a trend towards improvements in the neurocognitive profile using rTMS. Negative findings have also been reported. However, most studies were limited by their small sample size or included mixed samples, or the adopted single-blind designs potentially biased the blinding of the study design.

CONCLUSION

rTMS is a noninvasive brain stimulation that may be considered a valuable and promising technique for cognitive enhancement in TRD.

Induction of Neurorestoration From Endogenous Stem Cells

Neural stem cells (NSCs) persist in the subventricular zone lining the ventricles of the adult brain. The resident stem/progenitor cells can be stimulated in vivo by neurotrophic factors, hematopoietic growth factors, magnetic stimulation, and/or physical exercise. In both animals and humans, the differentiation and survival of neurons arising from the subventricular zone may also be regulated by the trophic factors. Since stem/progenitor cells present in the adult brain and the production of new neurons occurs at specific sites, there is a possibility for the treatment of incurable neurological diseases. It might be feasible to induce neurogenesis, which would be particularly efficacious in the treatment of striatal neurodegenerative conditions such as Huntington's disease, as well as cerebrovascular diseases such as ischemic stroke and cerebral palsy, conditions that are widely seen in the clinics. Understanding of the molecular control of endogenous NSC activation and progenitor cell mobilization will likely provide many new opportunities as therapeutic strategies. In this review, we focus on endogenous stem/progenitor cell activation that occurs in response to exogenous factors including neurotrophic factors, hematopoietic growth factors, magnetic stimulation, and an enriched environment. Taken together, these findings suggest the possibility that functional brain repair through induced neurorestoration from endogenous stem cells may soon be a clinical reality.

NEUROBIOLOGICAL PREDICTORS OF RESPONSE TO DORSOLATERAL PREFRONTAL CORTEX REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION IN DEPRESSION: A SYSTEMATIC REVIEW

BACKGROUND

A significant proportion of patients with depression fail to respond to psychotherapy and standard pharmacotherapy, leading to treatment-resistant depression (TRD). Due to the significant prevalence of TRD, alternative therapies for depression have emerged as viable treatments in the armamentarium for this disorder. Repetitive transcranial magnetic stimulation (rTMS) is now being offered in clinical practice in broader numbers. Many studies have investigated various different neurobiological predictors of response of rTMS. However, a synthesis of this literature and an understanding of what biological targets predict response is lacking. This review aims to systematically synthesize the literature on the neurobiological predictors of rTMS in patients with depression.

METHODS

Medline (1996-2014), Embase (1980-2014), and PsycINFO (1806-2014) were searched under set terms. Two authors reviewed each article and came to consensus on the inclusion and exclusion criteria. All eligible studies were reviewed, duplicates were removed, and data were extracted individually.

RESULTS

The search identified 1,673 articles, 41 of which met both inclusion and exclusion criteria. Various biological factors at baseline appear to predict response to rTMS, including levels of certain molecular factors, blood flow in brain regions implicated in depression, electrophysiological findings, and specific genetic polymorphisms.

CONCLUSIONS

Significant methodological variability in rTMS treatment protocols limits the ability to generalize conclusions. However, response to treatment may be predicted by baseline frontal lobe blood flow, and presence of polymorphisms of the 5-hydroxytryptamine (5-HT) -1a gene, the LL genotype of the serotonin transporter linked polymorphic region (5-HTTLPR) gene, and Val/Val homozygotes of the brain-derived neurotrophic factor (BDNF) gene.

Neurobiological mechanisms of repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex in depression: a systematic review

Depression is one of the most prevalent mental illnesses worldwide and a leading cause of disability, especially in the setting of treatment resistance. In recent years, repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising alternative strategy for treatment-resistant depression and its clinical efficacy has been investigated intensively across the world. However, the underlying neurobiological mechanisms of the antidepressant effect of rTMS are still not fully understood. This review aims to systematically synthesize the literature on the neurobiological mechanisms of treatment response to rTMS in patients with depression. Medline (1996-2014), Embase (1980-2014) and PsycINFO (1806-2014) were searched under set terms. Three authors reviewed each article and came to consensus on the inclusion and exclusion criteria. All eligible studies were reviewed, duplicates were removed, and data were extracted individually. Of 1647 articles identified, 66 studies met both inclusion and exclusion criteria. rTMS affects various biological factors that can be measured by current biological techniques. Although a number of studies have explored the neurobiological mechanisms of rTMS, a large variety of rTMS protocols and parameters limits the ability to synthesize these findings into a coherent understanding. However, a convergence of findings suggest that rTMS exerts its therapeutic effects by altering levels of various neurochemicals, electrophysiology as well as blood flow and activity in the brain in a frequency-dependent manner. More research is needed to delineate the neurobiological mechanisms of the antidepressant effect of rTMS. The incorporation of biological assessments into future rTMS clinical trials will help in this regard.

Electrical Stimulation Elicits Neural Stem Cells Activation: New Perspectives in CNS Repair

Researchers are enthusiastically concerned about neural stem cell (NSC) therapy in a wide array of diseases, including stroke, neurodegenerative disease, spinal cord injury, and depression. Although enormous evidences have demonstrated that neurobehavioral improvement may benefit from NSC-supporting regeneration in animal models, approaches to endogenous and transplanted NSCs are blocked by hurdles of migration, proliferation, maturation, and integration of NSCs. Electrical stimulation (ES) may be a selective non-drug approach for mobilizing NSCs in the central nervous system. This technique is suitable for clinical application, because it is well established and its potential complications are manageable. Here, we provide a comprehensive review of the emerging positive role of different electrical cues in regulating NSC biology in vitro and in vivo, as well as biomaterial-based and chemical stimulation of NSCs. In the future, ES combined with stem cell therapy or other cues probably becomes an approach for promoting brain repair.

The neuroprotection of repetitive transcranial magnetic stimulation pre-treatment in vascular dementia rats

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique that could interfere cortical excitability though brief electric currents induced by alternating magnetic fields from the inductive coil. Currently, it has been applied in many fields of basic and clinical neuro-research. The aims of the present study are to investigate the effect of rTMS pre-treatment on cognitive function in vascular dementia (VaD) rats and further explore the molecular mechanism of rTMS neuroprotection on VaD. We found that rTMS pre-treated VaD rats showed significantly better memory and learning abilities in Morris water maze test compared to the untreated group. Moreover, the mRNA and protein expression levels of BDNF, TrkB, and SYN were significantly higher in the rTMS pre-treated group, indicating that rTMS pre-treatment has neuroprotective effect for VaD, which may have resulted from the increased level of BDNF, TrkB, and SYN in the hippocampal CA1 area.

Anti-depressive mechanism of repetitive transcranial magnetic stimulation in rat: the role of the endocannabinoid system

Repetitive transcranial magnetic stimulation (rTMS) to treat depression has been thoroughly investigated in recent years. However, the underlying mechanisms are not fully understood. In this study, a chronic unpredictable mild stress (CUMS) paradigm was applied to male Sprague Dawley rats. Then rTMS was performed for 7 consecutive days, and the anti-depressive effects were evaluated by the sucrose preference test (SPT), the forced swimming test (FST), and the open-field test (OFT). Hippocampal cannabinoid type I receptor (CB1) expression was measured, and the expression levels of brain-derived neurotrophic factor (BDNF), Bcl-2, and Bax and the number of bromodeoxyuridine (BrdU)-positive cells were also investigated. These parameters were also observed after the selective CB1 receptor antagonist AM251 was used as a blocking agent. The results showed that CUMS induced a significant decrease in sucrose preference, a significant increase in immobility time in the FST, and a significantly decreased horizontal distance in the OFT. In addition, reduced hippocampal CB1 receptor, BDNF, and Bcl-2/Bax protein expression levels in CUMS rats, as well as decreased cell proliferation were also observed in the dentate gyrus. Meanwhile, rTMS treatment up-regulated cell proliferation; elevated CB1 receptor, BDNF, and Bcl-2/Bax expression levels in the hippocampus; and ameliorated depressive-like behaviors. All of these beneficial effects were abolished by AM251. These results indicate that rTMS increases BDNF production and hippocampal cell proliferation to protect against CUMS-induced changes through its effect on CB1 receptors.

Electroconvulsive therapy increases hippocampal and amygdala volume in therapy refractory depression: a longitudinal pilot study

Electroconvulsive therapy (ECT) is the most potent biological therapy in depression. Animal studies suggest that ECT acts via neuroplasticity effects on limbic structures involved in the pathophysiology of depression but in vivo evidence at the human system level is scarce. Therefore, the aim of the present study was to investigate the effect of ECT on hippocampus and amygdala volume in 15 antidepressant-free patients with treatment refractory depression (seven males, range 42-63 years). ECT treatment was successful as indexed by a significant decrease in depressive symptoms (t14=13.6; p<0.001). Analysis of normalized volumetric data before and after ECT treatment revealed a significant volume increase of both hippocampus and amygdala (minimum p<0.005) with no evidence for a change in global brain volume. Though this change in volume cannot be clearly related to treatment effects, ECT is associated with broader neurotrophic effects other than mere adult neurogenesis in the hippocampus, which has been previously suggested as a core mechanism on the basis of animal data.