Revisiting the effectiveness of repetitive transcranial magnetic stimulation treatment in depression, again.

Following on from the publication of the Royal Australian and New Zealand Journal of Psychiatry Mood Disorder Clinical Practice Guidelines (2020) and criticisms of how these aberrantly addressed repetitive transcranial magnetic stimulation treatment of depression, questions have continued to be raised in the journal about this treatment by a small group of authors, whose views we contend do not reflect the broad acceptance of this treatment nationally and internationally. In fact, the evidence supporting the use of repetitive transcranial magnetic stimulation treatment in depression is unambiguous and substantial, consisting of an extensive series of clinical trials supported by multiple meta-analyses, network meta-analysis and umbrella reviews. Importantly, the use of repetitive transcranial magnetic stimulation treatment in depression has also been subject to a series of health economic analyses. These indicate that repetitive transcranial magnetic stimulation is a cost-effective therapy and have been used in some jurisdictions, including Australia, in support of public funding. An argument has been made that offering repetitive transcranial magnetic stimulation treatment may delay potentially effective pharmacotherapy. In fact, there is considerably greater danger of the opposite happening. Repetitive transcranial magnetic stimulation is as, if not more effective, than antidepressant medication after two unsuccessful medication trials and should be a consideration for all patients under these circumstances where available. There is no meaningful ongoing debate about the use of repetitive transcranial magnetic stimulation treatment in depression - it is a safe, effective and cost-effective treatment.

The effects of individualised intermittent theta burst stimulation in the prefrontal cortex: A TMS-EEG study.

Recent studies have highlighted variability in response to theta burst stimulation (TBS) in humans. TBS paradigm was originally developed in rodents to mimic gamma bursts coupled with theta rhythms, and was shown to elicit long-term potentiation. The protocol was subsequently adapted for humans using standardised frequencies of stimulation. However, each individual has different rhythmic firing pattern. The present study sought to explore whether individualised intermittent TBS (Ind iTBS) could outperform the effects of two other iTBS variants. Twenty healthy volunteers received iTBS over left prefrontal cortex using 30 Hz at 6 Hz, 50 Hz at 5 Hz, or individualised frequency in separate sessions. Ind iTBS was determined using theta-gamma coupling during the 3-back task. Concurrent use of transcranial magnetic stimulation and electroencephalography (TMS-EEG) was used to track changes in cortical plasticity. We also utilised mood ratings using a visual analogue scale and assessed working memory via the 3-back task before and after stimulation. No group-level effect was observed following either 30 or 50 Hz iTBS in TMS-EEG. Ind iTBS significantly increased the amplitude of the TMS-evoked P60, and decreased N100 and P200 amplitudes. A significant positive correlation between neurophysiological change and change in mood rating was also observed. Improved accuracy in the 3-back task was observed following both 50 Hz and Ind iTBS conditions. These findings highlight the critical importance of frequency in the parameter space of iTBS. Tailored stimulation parameters appear more efficacious than standard paradigms in neurophysiological and mood changes. This novel approach presents a promising option and benefits may extend to clinical applications.

Is rTMS effective for anxiety symptoms in major depressive disorder? An efficacy analysis comparing left-sided high-frequency, right-sided low-frequency, and sequential bilateral rTMS protocols.

BACKGROUND: Anxiety symptoms are common in major depressive disorder. Whilst therapeutic efficacy of repetitive transcranial magnetic stimulation (rTMS) in depression is well-established, minimal research has investigated rTMS's efficacy in treating anxiety symptoms in depression. METHODS: This study investigates the effectiveness of rTMS in treating anxiety symptoms in depression, specifically the relative efficacy of the three rTMS protocols commonly used in clinical practice: left-sided high-frequency, right-sided low-frequency and sequential bilateral rTMS. Antidepressant efficacy of each rTMS protocol is also investigated. Treatment data for 697 patients were pooled from three studies across five sites. Changes in Beck's Anxiety Inventory (BAI) and the Hamilton Depression Rating Scale over 4-week rTMS courses were analysed using latent growth curve modelling. RESULTS: All rTMS protocols were effective in treating anxiety symptoms (mean BAI reduction, 8.13 points; p < 0.001) and depressive symptoms. Near therapeutic equivalence was seen across the three protocols. Improvement in depressive severity positively correlated with improvement in anxiety. Both high- and low-baseline anxiety scores showed overall symptom reduction. CONCLUSIONS: This study addresses the clinical knowledge gap pertaining to rTMS's therapeutic efficacy in treating anxiety symptoms in depression and the relative efficacy of three commonly used stimulation protocols. Our findings suggest therapeutic equivalence across left-sided high-frequency, right-sided low-frequency, and sequential bilateral rTMS approaches.

Impact of different intensities of intermittent theta burst stimulation on the cortical properties during TMS-EEG and working memory performance.

Intermittent theta burst stimulation (iTBS) is a noninvasive brain stimulation technique capable of increasing cortical excitability beyond the stimulation period. Due to the rapid induction of modulatory effects, prefrontal application of iTBS is gaining popularity as a therapeutic tool for psychiatric disorders such as depression. In an attempt to increase efficacy, higher than conventional intensities are currently being applied. The assumption that this increases neuromodulatory may be mechanistically false for iTBS. This study examined the influence of intensity on the neurophysiological and behavioural effects of iTBS in the prefrontal cortex. Sixteen healthy participants received iTBS over prefrontal cortex at either 50, 75 or 100% resting motor threshold in separate sessions. Single-pulse TMS and concurrent electroencephalography (EEG) was used to assess changes in cortical reactivity measured as TMS-evoked potentials and oscillations. The n-back task was used to assess changes in working memory performance. The data can be summarised as an inverse U-shape relationship between intensity and iTBS plastic effects, where 75% iTBS yielded the largest neurophysiological changes. Improvement in reaction time in the 3-back task was supported by the change in alpha power, however, comparison between conditions revealed no significant differences. The assumption that higher intensity results in greater neuromodulatory effects may be false, at least in healthy individuals, and should be carefully considered for clinical populations. Neurophysiological changes associated with working memory following iTBS suggest functional relevance. However, the effects of different intensities on behavioural performance remain elusive in the present healthy sample.

A pilot study of the comparative efficacy of 100 Hz magnetic seizure therapy and electroconvulsive therapy in persistent depression.

BACKGROUND: Magnetic seizure therapy (MST) is a novel brain stimulation technique that uses a high-powered transcranial magnetic stimulation device to produce therapeutic seizures. Preliminary MST studies have found antidepressant effects in the absence of cognitive side effects but its efficacy compared to electroconvulsive therapy (ECT) remains unclear. The aim of this study was to investigate the therapeutic efficacy and cognitive profile of MST compared to standard right unilateral ECT treatment. METHODS: Thirty-seven patients completed a course of at least nine ECT or MST treatments in a randomized double-blind protocol. Assessments of depression severity and cognition were performed before and after treatment. RESULTS: No difference in the antidepressant effectiveness between the treatments was seen across any of the clinical outcome measures, although the overall response rates in both groups were quite low. In regards to cognition, following MST there were significant improvements in tests of psychomotor speed, verbal memory, and cognitive inhibition, with no reductions in cognitive performance. Following ECT there was significant improvement in only one of the cognitive inhibition tasks. With respect to the between-group comparisons, the MST group showed a significantly greater improvement on psychomotor speed than ECT. CONCLUSIONS: MST showed similar efficacy to right unilateral ECT in patients with treatment-resistant depression without cognitive side effects but in a sample that was only of sufficient size to demonstrate relatively large differences in response between the two groups. Future research should aim to optimize the methods of MST administration and compare its efficacy to ECT in large randomized controlled trials.

Effects of prefrontal bipolar and high-definition transcranial direct current stimulation on cortical reactivity and working memory in healthy adults.

Transcranial direct current stimulation (tDCS) is a well-recognised neuromodulatory technology which has been shown to induce short-lasting changes in motor-cortical excitability. The recent and rapid expansion of tDCS into the cognitive domain, however, necessitates deeper mechanistic understanding of its neurophysiological effects over non-motor brain regions. The present study utilised transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) to probe the immediate and longer-term effects of both a bipolar (BP-tDCS) and more focal 4×1 High-Definition tDCS (HD-tDCS) montage applied over the left DLPFC on TMS-evoked potentials (TEPs) and oscillations in 19 healthy adult participants. 2-back working memory (WM) performance was also assessed as a marker of cognitive function. Region of interest (ROI) analyses taken from the F1 electrode directly adjacent to the stimulation site revealed increased P60 TEP amplitudes at this location 5min following BP-tDCS and 30min following HD-tDCS. Further global cluster based analyses of all scalp electrodes revealed widespread neuromodulatory changes following HD-tDCS, but not BP-tDCS, both five and 30min after stimulation, with reductions also detected in both beta and gamma oscillatory power over parieto-occipital channels 30min after stimulation. No significant changes in WM performance were observed following either HD-tDCS or BP-tDCS. This study highlights the capacity for single-session prefrontal anodal tDCS montages to modulate neurophysiological processes, as assessed with TMS-EEG.

Enhancement of Working Memory and Task-Related Oscillatory Activity Following Intermittent Theta Burst Stimulation in Healthy Controls.

Noninvasive brain stimulation is increasingly being investigated for the enhancement of cognition, yet current approaches appear to be limited in their degree and duration of effects. The majority of studies to date have delivered stimulation in "standard" ways (i.e., anodal transcranial direct current stimulation or high-frequency transcranial magnetic stimulation). Specialized forms of stimulation, such as theta burst stimulation (TBS), which more closely mimic the brains natural firing patterns may have greater effects on cognitive performance. We report here the findings from the first-ever investigation into the persistent cognitive and electrophysiological effects of intermittent TBS (iTBS) delivered to the left dorsolateral prefrontal cortex. In 19 healthy controls, active iTBS significantly improved performance on an assessment of working memory when compared with sham stimulation across a period of 40 min post stimulation. The behavioral findings were accompanied by increases in task-related fronto-parietal theta sychronization and parietal gamma band power. These results have implications for the role of more specialized stimulation approaches in neuromodulation.

Increased gamma connectivity during working memory retention following traumatic brain injury.

PRIMARY OBJECTIVE: Alterations to functional connectivity following a traumatic brain injury (TBI) may lead to impaired cognitive performance and major depressive disorder (MDD). In particular, functional gamma band connectivity is thought to reflect information binding important for working memory. The objective of this study was to determine whether altered functional gamma connectivity may be a factor in MDD following TBI (TBI-MDD). RESEARCH DESIGN: This study assessed individuals with TBI-MDD, as well as individuals with TBI alone and MDD alone using electroencephalographic recordings while participants performed a working memory task to assess differences in functional connectivity between these groups. METHODS AND PROCEDURES: Functional connectivity was compared using the debiased weighted phase lag index (wPLI). wPLI was measured from a group of healthy controls (n = 31), participants with MDD (n = 17), participants with TBI (n = 20) and participants with TBI-MDD (n = 15). MAIN OUTCOMES AND RESULTS: Contrary to the predictions, this study found both the groups with TBI and TBI-MDD showed higher gamma connectivity from posterior regions during WM retention. CONCLUSIONS: This may reflect dysfunctional functional connectivity in these groups, as a result of maladaptive neuroplastic reorganization.

Preliminary investigation of the effects of γ-tACS on working memory in schizophrenia.

Working memory impairment in schizophrenia has been strongly associated with abnormalities in gamma oscillations within the dorsolateral prefrontal cortex (DLFPC). We recently published the first ever study showing that anodal transcranial direct current stimulation (tDCS) to the left DLPFC was able to significantly improve working memory in schizophrenia and did so seemingly via restoring normal gamma oscillatory function. Transcranial alternating current stimulation (tACS) is a form of electrical brain stimulation that delivers stimulation at a specific frequency and has been shown to entrain endogenous cortical oscillations. Therefore, gamma (γ) tACS may be even more effective than tDCS in improving working memory in schizophrenia. In a randomized repeated-measures study we compared the effects of γ-tACS, tDCS and sham stimulation on the performance of the two back working memory tasks in ten patients with schizophrenia. There was a significant time by stimulation interaction, with tDCS and sham showing trend-level improvements in working memory, while γ-tACS, contrary to our hypothesis, showed no change. The results are discussed in light of posited divergent effects of tACS and tDCS on the pathophysiology of working memory impairment in schizophrenia.

A STUDY OF THE PATTERN OF RESPONSE TO rTMS TREATMENT IN DEPRESSION.

BACKGROUND: Considerable research has demonstrated the efficacy of repetitive transcranial magnetic stimulation (rTMS) treatment in patients with depression. However, limited research has described the pattern of response to rTMS treatment or explored possible predictors of the likelihood of treatment response. METHODS: Data from 11 clinical trials (n = 1,132) was pooled and we described the pattern of response to rTMS, rate of response, and remission as well as potential clinical and demographic predictors of response. RESULTS: There was a bimodal pattern of response to rTMS with the response-associated peak at 57% reduction in depression rating scale scores. About 46% of patients achieved response criteria, with 31% completing rTMS treatment in remission. A greater likelihood of response was seen for patients who had less severe depression at baseline, a shorter duration of the current episode, and recurrent rather than single episode of depression. Greater response was also seen in patients treated at higher stimulation intensity. CONCLUSIONS: A meaningful percentage (>40%) of patients respond to a course of rTMS treatment. Response does vary with a number of clinical and demographic variables but none of these variables exert a sufficiently strong influence on response rates to warrant using these criteria to exclude patients from treatment.

Theta-burst stimulation: a new form of TMS treatment for depression?

Major depressive disorder (MDD) is a common debilitating condition where only one third of patients achieve remission after the first antidepressant treatment. Inadequate efficacy and adverse effects of current treatment strategies call for more effective and tolerable treatment options. Transcranial magnetic stimulation (TMS) is a noninvasive approach to manipulate brain activity and alter cortical excitability. There has been more than 15 years of research on the use of repetitive form of TMS (rTMS) for the treatment of patients with depression, which has shown it to be an effective antidepressant treatment. Even though rTMS treatment has shown efficacy in treating depression, there is a high degree of interindividual variability in response. A newer form of rTMS protocol, known as theta-burst stimulation (TBS), has been shown to produce similar if not greater effects on brain activity than standard rTMS. TBS protocols have a major advantage over standard rTMS approaches in their reduced administration duration. Conventional rTMS procedures last between 20 and 45 min, as compared to TBS paradigms that require 1 to 3 min of stimulation. Recently, a small number of studies have suggested that TBS has similar or better efficacy in treating depression compared to rTMS. Optimization, identification of response predictors, and clarification of neurobiological mechanisms of TBS is required if it is to be further developed as a less time intensive, safe, and effective treatment for MDD.

The effect of γ-tACS on working memory performance in healthy controls.

Transcranial Direct Current Stimulation (tDCS) has been widely investigated for its potential to enhance cognition, and in particular working memory, however to date standard approaches to stimulation have shown only modest effects. Alternative, more specialised, forms of current delivery may be better suited to cognitive enhancement. One such method is transcranial Alternating Current Stimulation (tACS) which delivers stimulation at a specific frequency and has been shown to entrain endogenous cortical oscillations which underlie cognitive functioning. To date there has been no comparison of the effects of tACS to those of tDCS on cognitive enhancement. In a randomised repeated-measures study design we assessed the effect of gamma (γ)-tACS, tDCS and sham tDCS on working memory in 18 healthy participants who attended three sessions held at least 72h apart. Pre- and post-stimulation working memory performance was assessed using the 2 and 3-back. Our findings indicated the presence of a selective improvement in performance on the 3-back task following γ-tACS compared with tDCS and sham stimulation. The current findings provide support for further and more detailed investigation of the role of γ-tACS as a more specialised approach to neuromodulation.

Equivalent beneficial effects of unilateral and bilateral prefrontal cortex transcranial magnetic stimulation in a large randomized trial in treatment-resistant major depression.

Repetitive transcranial magnetic stimulation treatment (rTMS) is an effective treatment for depression but the optimal methods of administration have yet to be determined. Recent studies have produced conflicting results as to whether unilateral rTMS is more or less effective than sequentially applied bilateral rTMS. To address this we conducted a trial comparing sequential bilateral rTMS to right-sided unilateral rTMS using a priming protocol. Patients with treatment-resistant depression (n = 179) were enrolled in a two-arm randomized controlled trial across a 4-wk time period. The primary outcome assessment was the Hamilton Depression Rating Scale. Overall, there was a substantial response rate of >50% (and a 40% remission rate); however, there were no significant differences in clinical response between the two treatment groups. rTMS was well tolerated with a very low discontinuation rate. There was no relationship between response in the current trial and previous response, or non-response, to electroconvulsive therapy. We found no significant differences in clinical response between sequential bilateral rTMS and right-sided unilateral rTMS applied with a priming protocol. The results of this study do not support superior efficacy of bilateral rTMS and instead suggest that other approaches should be explored to increase treatment efficacy.

Pilot study of the clinical and cognitive effects of high-frequency magnetic seizure therapy in major depressive disorder.

BACKGROUND: Electroconvulsive therapy (ECT) is a very commonly used treatment for patients with severe and treatment-resistant depression. Although effective, this treatment is complicated by a number of side effects including cognitive impairment motivating attempts to develop treatment alternatives. Magnetic seizure therapy (MST) is a brain stimulation technique using a high-powered transcranial magnetic stimulation device to produce therapeutic seizures. Preliminary research suggests that MST has antidepressant activity in the absence of cognitive side effects. The aim of this study was therefore to investigate the therapeutic efficacy and cognitive profile of MST provided at high frequency (100 Hz) and potentially longer stimulation trains and longer treatment courses than have been previously investigated. METHODS: Thirteen patients participated in an open-label clinical trial of up to 18 treatment sessions with 100-Hz MST. Assessments of depression severity and cognitive functioning were performed before and after treatment. RESULTS: Of the 13 patients who completed the study, five met clinical response criteria at study end. There was an overall group reduction in depression severity and no evidence of any impairment of orientation, memory, or other elements of cognition after MST treatment. The major limitation of the study was its lack of sham control. CONCLUSIONS: In conclusion, MST shows antidepressant efficacy without apparent cognitive side effects. However, substantial research is required to understand the optimal conditions for stimulation and to compare MST to established treatments including ECT.

Investigation of neurobiological responses to theta burst stimulation during recovery from mild traumatic brain injury (mTBI).

OBJECTIVE: The ability of the brain to recover following neurological insult is of interest for mild traumatic brain injury (mTBI) populations. Investigating whether non-invasive brain stimulation (NIBS) can modulate neurophysiology and cognition may lead to the development of therapeutic interventions post injury. The purpose of this study was to investigate neurobiological effects of one session of intermittent theta burst stimulation (iTBS) to the dorsolateral prefrontal cortex (DLPFC) in participants recovering from mTBI. METHOD: Changes to neurophysiology were assessed with electroencephalography (EEG) and transcranial magnetic stimulation combined with EEG (TMS-EEG). Digit span working memory accuracy assessed cognitive performance. 30 patients were assessed within one-month of sustaining a mTBI and 26 demographically matched controls were assessed. Participants were also assessed at 3-months (mTBI: N = 21, control: N = 26) and 6-months (mTBI: N = 15, control: N = 24). RESULTS: Analyses demonstrated iTBS did not reliably modulate neurophysiological activity, and no differences in cognitive performance were produced by iTBS at any assessment time-point. CONCLUSIONS: Factors responsible for our null results are unclear. Possible limitations to our experimental design are discussed. SIGNIFICANCE: Our findings suggest additional research is required to establish the effects of iTBS on plasticity following mTBI, prior to therapeutic application. DATA AND CODE AVAILABILITY STATEMENT: We do not have ethical approval to make this data publicly available, as our approval predated our inclusion of such approvals (which we now do routinely).

Recovery of clinical, cognitive and cortical activity measures following mild traumatic brain injury (mTBI): A longitudinal investigation.

The mechanisms that underpin recovery following mild traumatic brain injury (mTBI) remain poorly understood. Identifying neurophysiological markers and their functional significance is necessary to develop diagnostic and prognostic indicators of recovery. The current study assessed 30 participants in the subacute phase of mTBI (10-31 days post-injury) and 28 demographically matched controls. Participants also completed 3 month (mTBI: N = 21, control: N = 25) and 6 month (mTBI: N = 15, control: N = 25) follow up sessions to track recovery. At each time point, a battery of clinical, cognitive, and neurophysiological assessments was completed. Neurophysiological measures included resting-state electroencephalography (EEG) and transcranial magnetic stimulation combined with EEG (TMS-EEG). Outcome measures were analysed using mixed linear models (MLM). Group differences in mood, post-concussion symptoms and resting-state EEG resolved by 3 months, and recovery was maintained at 6 months. On TMS-EEG derived neurophysiological measures of cortical reactivity, group differences ameliorated at 3 months but re-emerged at 6 months, while on measures of fatigue, group differences persisted across all time points. Persistent neurophysiological changes and greater fatigue in the absence of measurable cognitive impairment may suggest the impact of mTBI on neuronal communication may leads to increased neural effort to maintain efficient function. Neurophysiological measures to track recovery may help identify both temporally optimal windows and therapeutic targets for the development of new treatments in mTBI.

A comprehensive characterization of cognitive performance, clinical symptoms, and cortical activity following mild traumatic brain injury (mTBI).

OBJECTIVE: The objective of this study was to investigate clinical symptoms, cognitive performance and cortical activity following mild traumatic brain injury (mTBI). METHODS: We recruited 30 individuals in the sub-acute phase post mTBI and 28 healthy controls with no history of head injury and compared these groups on clinical, cognitive and cortical activity measures. Measures of cortical activity included; resting state electroencephalography (EEG), task related EEG and combined transcranial magnetic stimulation with electroencephalography (TMS-EEG). Primary analyses investigated clinical, cognitive and cortical activity differences between groups. Exploratory analyses investigated the relationships between these measures. RESULTS: At 4 weeks' post injury, mTBI participants exhibited significantly greater post concussive and clinical symptoms compared to controls; as well as reduced cognitive performance on verbal learning and working memory measures. mTBI participants demonstrated alterations in cortical activity while at rest and in response to stimulation with TMS. CONCLUSIONS: The present study comprehensively characterized the multidimensional effect of mTBI in the sub-acute phase post injury, showing a broad range of differences compared to non-mTBI participants. Further research is needed to explore the relationship between these pathophysiologies and clinical/cognitive symptoms in mTBI.

Neurophysiological correlates of non-motor symptoms in late premanifest and early-stage manifest huntington's disease.

OBJECTIVE: To find sensitive neurophysiological correlates of non-motor symptoms in Huntington's disease (HD), which are essential for the development and assessment of novel treatments. METHODS: We used resting state EEG to examine differences in oscillatory activity (analysing the isolated periodic as well as the complete EEG signal) and functional connectivity in 22 late premanifest and early stage people with HD and 20 neurotypical controls. We then assessed the correlations between these neurophysiological markers and clinical measures of apathy and processing speed. RESULTS: Significantly lower theta and greater delta resting state power was seen in the HD group, as well as significantly greater delta connectivity. There was a significant positive correlation between theta power and processing speed, however there were no associations between the neurophysiological and apathy measures. CONCLUSIONS: We speculate that these changes in oscillatory power and connectivity reflect ongoing, frontally concentrated degenerative and compensatory processes associated with HD. SIGNIFICANCE: Our findings support the potential utility of quantitative EEG as a proximate marker of processing speed, but not apathy in HD.

Effects of medial prefrontal transcranial alternating current stimulation on neural activity and connectivity in people with Huntington's disease and neurotypical controls.

We investigated the effects of transcranial alternating current stimulation (tACS) targeted to the medial prefrontal cortex (mPFC) on resting electroencephalographic (EEG) indices of oscillatory power, aperiodic exponent and offset, and functional connectivity in 22 late premanifest and early manifest stage individuals with HD and 20 neurotypical controls. Participants underwent three 20-minute sessions of tACS at least 72 hours apart; one session at alpha frequency (either each participant's Individualised Alpha Frequency (IAF), or 10 Hz when an IAF was not detected); one session at delta frequency (2 Hz); and a session of sham tACS. Session order was randomised and counterbalanced across participants. EEG recordings revealed a reduction of the spectral exponent ('flattening' of the 1/f slope) of the eyes-open aperiodic signal in participants with HD following alpha-tACS, suggestive of an enhancement in excitatory tone. Contrary to expectation, there were no changes in oscillatory power or functional connectivity in response to any of the tACS conditions in the participants with HD. By contrast, alpha-tACS increased delta power in neurotypical controls, who further demonstrated significant increases in theta power and theta functional connectivity in response to delta-tACS. This study contributes to the rapidly growing literature on the potential experimental and therapeutic applications of tACS by examining neurophysiological outcome measures in people with HD as well as neurotypical controls.