Neuropsychological impact of Cg25 deep brain stimulation for treatment-resistant depression: preliminary results over 12 months

Lack of neuropsychological effects following short-term subcallosal cingulate gyrus deep brain stimulation in treatment-resistant depression: a randomised crossover study

BACKGROUND

The subcallosal cingulate gyrus (SCG) is integral to cognitive function and mood regulation. Open-label SCG deep brain stimulation (DBS) studies demonstrate improvement or stabilisation of cognitive function in treatment-resistant depression (TRD).

OBJECTIVE

This randomised controlled study aims to evaluate the neuropsychological effects of SCG-DBS.

METHODS

35 participants with TRD received active or sham stimulation over two 3-month periods. A neuropsychological battery was administered to assess processing speed, learning and memory, and cognitive flexibility. Composite measures were derived for each domain after Period I. A mixed model for repeated measures analysis was performed for each test, with further analysis of significant measures to determine sustainability after Period II.

FINDINGS

No significant differences in changes in depression scores were observed between groups. There were no significant deteriorations in cognitive performance following active SCG-DBS. Category Fluency Test performance improved after 3 months of active SCG-DBS (p=0.002); however, this was non-significant after correcting for multiple comparisons and was not observed after Period II (p=0.615).

CONCLUSION AND IMPLICATIONS

While no cognitive deterioration was observed following SCG-DBS, significant improvements in cognitive function were not evident. There may be a transient enhancement in processing speed; however, this effect is not fully understood. Future studies should include larger cohorts and extended stimulation periods to explore the long-term effects of SCG-DBS in TRD and the sustainability of improvements in cognitive domains.

DeepFocus: a transnasal approach for optimized deep brain stimulation of reward circuit nodes

Objective.Transcranial electrical stimulation (TES) is an effective technique to modulate brain activity and treat diseases. However, TES is primarily used to stimulate superficial brain regions and is unable to reach deeper targets. The spread of injected currents in the head is affected by volume conduction and the additional spreading of currents as they move through head layers with different conductivities, as is discussed in Forssellet al(2021J. Neural Eng.18046042). In this paper, we introduce DeepFocus, a technique aimed at stimulating deep brain structures in the brain's 'reward circuit' (e.g. the orbitofrontal cortex, Brodmann area 25, amygdala, etc).Approach.To accomplish this, DeepFocus utilizes transnasal electrode placement (under the cribriform plate and within the sphenoid sinus) in addition to electrodes placed on the scalp, and optimizes current injection patterns across these electrodes. To quantify the benefit of DeepFocus, we develop the DeepROAST simulation and optimization platform. DeepROAST simulates the effect of complex skull-base bones' geometries on the electric fields generated by DeepFocus configurations using realistic head models. It also uses optimization methods to search for focal and efficient current injection patterns, which we use in our simulation and cadaver studies.Main results.In simulations, optimized DeepFocus patterns created larger and more focal fields in several regions of interest than scalp-only electrodes. In cadaver studies, DeepFocus patterns created large fields at the medial orbitofrontal cortex (OFC) with magnitudes comparable to stimulation studies, and, in conjunction with established cortical stimulation thresholds, suggest that the field intensity is sufficient to create neural response, e.g. at the OFC.Significance.This minimally invasive stimulation technique can enable more efficient and less risky targeting of deep brain structures to treat multiple neural conditions.

Emerging Outlook on Personalized Neuromodulation for Depression: Insights From Tractography-Based Targeting

BACKGROUND

Deep brain stimulation has shown promise in treating individual patients with treatment-resistant depression, but larger-scale trials have been less successful. Here, we created what is, to our knowledge, the largest meta-analysis with individual patient data to date to explore whether the use of tractography enhances the efficacy of deep brain stimulation for treatment-resistant depression.

METHODS

We systematically reviewed 1823 articles, selecting 32 that contributed data from 366 patients. We stratified the individual patient data based on stimulation target and use of tractography. Using 2-way type III analysis of variance, Welch's 2-sample t tests, and mixed-effects linear regression models, we evaluated changes in depression severity 1 year (9-15 months) postoperatively and at last follow-up (4 weeks to 8 years) as assessed by depression scales.

RESULTS

Tractography was used for medial forebrain bundle (MFB) (n = 17 tractography/32 total), subcallosal cingulate (SCC) (n = 39 tractography/241 total), and ventral capsule/ventral striatum (n = 3 tractography/41 total) targets; it was not used for bed nucleus of stria terminalis (n = 11), lateral habenula (n = 10), and inferior thalamic peduncle (n = 1). Across all patients, tractography significantly improved mean depression scores at 1 year (p < .001) and last follow-up (p = .009). Within the target cohorts, tractography improved depression scores at 1 year for both MFB and SCC, though significance was met only at the α = 0.1 level (SCC: β = 15.8%, p = .09; MFB: β = 52.4%, p = .10). Within the tractography cohort, patients with MFB tractography showed greater improvement than patients with SCC tractography (72.42 ± 7.17% vs. 54.78 ± 4.08%) at 1 year (p = .044).

CONCLUSIONS

Our findings underscore the promise of tractography in deep brain stimulation for treatment-resistant depression as a method for personalization of therapy, supporting its inclusion in future trials.

Outcome differences between males and females undergoing deep brain stimulation for treatment-resistant depression: systematic review and individual patient data meta-analysis

BACKGROUND

Treatment-resistant depression (TRD) occurs more commonly in women. Deep brain stimulation (DBS) is an emerging treatment for TRD, and its efficacy continues to be explored. However, differences in treatment outcomes between males and females have yet to be explored in formal analysis.

METHODS

A PRISMA-compliant systematic review of DBS for TRD studies was conducted. Patient-level data were independently extracted by two authors. Treatment response was defined as a 50 % or greater reduction in depression score. Percent change in depression scores by gender were evaluated using random-effects analyses.

RESULTS

Of 737 records, 19 studies (129 patients) met inclusion criteria. The mean reduction in depression score for females was 57.7 % (95 % CI, 64.33 %-51.13 %), whereas for males it was 35.2 % (95 % CI, 45.12 %-25.23 %) (p < 0.0001). Females were more likely to respond to DBS for TRD when compared to males (OR = 2.44, 95 % CI 1.06, 1.95). These differences varied in significance when stratified by DBS anatomical target, age, and timeframe for responder classification.

LIMITATIONS

Studies included were open-label trials with small sample sizes.

CONCLUSIONS

Our findings suggest that females with TRD respond at higher rates to DBS treatment than males. Further research is needed to elucidate the implications of these results, which may include connectomic sexual dimorphism, depression phenotype variations, or unrecognized symptom reporting differences. Methodological standardization of outcome scales, granular demographic data, and individual subject outcomes would allow for more robust comparisons between trials.

Effects of deep brain stimulation on cognitive functioning in treatment-resistant depression: a systematic review and meta-analysis

Deep brain stimulation (DBS) is a promising intervention for treatment-resistant depression (TRD). Effects on cognitive functioning are unclear since they have been studied in small samples. We aim to estimate the impact of DBS on cognitive functioning in TRD with a systematic review and meta-analyses. After systematically searching PubMed we included 10 studies which compared standardized neuropsychological tests before and after DBS or between active and sham DBS in TRD. Different random-effects meta-analyses were done for different cognitive (sub-)domains and for different follow-up time windows (<6 months, 6-18 months, and >18 months). We found no significant differences in cognitive functioning up to 6 months of DBS. After 6-18 months of DBS small to moderate improvements were found in verbal memory (Hedge's g = 0.22, 95% CI = [0.01-0.43], p = 0.04), visual memory (Hedge's g = 0.37, 95% CI = [0.03-0.71], p = 0.04), attention/psychomotor speed (Hedge's g = 0.26, 95% CI = [0.02-0.50], p = 0.04) and executive functioning (Hedge's g = 0.37, 95% CI = [0.15-0.59], p = 0.001). Not enough studies could be retrieved for a meta-analysis of effects after >18 months of DBS or for the comparison of active and sham DBS. Qualitatively, generally no differences in cognitive functioning between active and sham DBS were found. No cognitive decline was found in this meta-analysis up to 18 months of DBS in patients with TRD. Results even suggest small positive effects of DBS on cognitive functioning in TRD, although this should be interpreted with caution due to lack of controlled data.

Network targets for therapeutic brain stimulation: towards personalized therapy for pain

Precision neuromodulation of central brain circuits is a promising emerging therapeutic modality for a variety of neuropsychiatric disorders. Reliably identifying in whom, where, and in what context to provide brain stimulation for optimal pain relief are fundamental challenges limiting the widespread implementation of central neuromodulation treatments for chronic pain. Current approaches to brain stimulation target empirically derived regions of interest to the disorder or targets with strong connections to these regions. However, complex, multidimensional experiences like chronic pain are more closely linked to patterns of coordinated activity across distributed large-scale functional networks. Recent advances in precision network neuroscience indicate that these networks are highly variable in their neuroanatomical organization across individuals. Here we review accumulating evidence that variable central representations of pain will likely pose a major barrier to implementation of population-derived analgesic brain stimulation targets. We propose network-level estimates as a more valid, robust, and reliable way to stratify personalized candidate regions. Finally, we review key background, methods, and implications for developing network topology-informed brain stimulation targets for chronic pain.

Modern neurosurgical techniques for psychiatric disorders

Psychosurgery refers to an ensemble of more or less invasive techniques designed to reduce the burden caused by psychiatric diseases in patients who have failed to respond to conventional therapy. While most surgeries are designed to correct apparent anatomical abnormalities, no discrete cerebral anatomical lesion is evident in most psychiatric diseases amenable to invasive interventions. Finding the optimal surgical targets in mental illness is troublesome. In general, contemporary psychosurgical procedures can be classified into one of two primary modalities: lesioning and stimulation procedures. The first group is divided into (a) thermocoagulation and (b) stereotactic radiosurgery or recently introduced transcranial magnetic resonance-guided focused ultrasound, whereas stimulation techniques mainly include deep brain stimulation (DBS), cortical stimulation, and the vagus nerve stimulation. The most studied psychiatric diseases amenable to psychosurgical interventions are severe treatment-resistant major depressive disorder, obsessive-compulsive disorder, Tourette syndrome, anorexia nervosa, schizophrenia, and substance use disorder. Furthermore, modern neuroimaging techniques spurred the interest of clinicians to identify cerebral regions amenable to be manipulated to control psychiatric symptoms. On this way, the concept of a multi-nodal network need to be embraced, enticing the collaboration of psychiatrists, psychologists, neurologists and neurosurgeons participating in multidisciplinary groups, conducting well-designed clinical trials.

Cognitive and quality-of-life related factors of body mass index (BMI) improvement after deep brain stimulation in the subcallosal cingulate and nucleus accumbens in treatment-refractory chronic anorexia nervosa

BACKGROUND

Up to 20% of the cases of anorexia nervosa (AN) are chronic and treatment-resistant. Recently, the efficacy of deep brain stimulation (DBS) for severe cases of AN has been explored, with studies showing an improvement in body mass index and other psychiatric outcomes. While the effects of DBS on cognitive domains have been studied in patients with other neurological and psychiatric conditions so far, no evidence has been gathered in AN.

METHODS

Eight patients with severe, chronic, treatment-resistant AN received DBS either to the nucleus accumbens (NAcc) or subcallosal cingulate (SCC; four subjects on each target). A comprehensive battery of neuropsychological and clinical outcomes was used before and 6-month after surgery.

FINDINGS

Although Body Mass Index (BMI) did not normalise, statistically significant improvements in BMI, quality of life, and performance on cognitive flexibility were observed after 6 months of DBS. Changes in BMI were related to a decrease in depressive symptoms and an improvement in memory functioning.

INTERPRETATION

These findings, although preliminary, support the use of DBS in AN, pointing to its safety, even for cognitive functioning; improvements of cognitive flexibility are reported. DBS seems to exert changes on cognition and mood that accompany BMI increments. Further studies are needed better to determine the impact of DBS on cognitive functions.

Deep brain stimulation improved depressive-like behaviors and hippocampal synapse deficits by activating the BDNF/mTOR signaling pathway

Our previous study demonstrated that acute deep brain stimulation (DBS) in the ventromedial prefrontal cortex (vmPFC) remarkably improved the depressive-like behaviors in a rat model of chronic unpredictable mild stress (CUS rats). However, the mechanisms by which chronic DBS altered depressive-like behaviors and reversed cognitive impairment have not been clarified. Recent work has shown that deficits in brain-derived neurotrophic factor (BDNF) and its downstream proteins, including mammalian target of rapamycin (mTOR), might be involved in the pathogenesis of depression. Therefore, we hypothesized that the antidepressant-like and cognitive improvement effects of DBS were achieved by activating the BDNF/mTOR pathway. CUS rats received vmPFC DBS at 20 Hz for 1 h once a day for 28 days. After four weeks of stimulation, the rats were assessed for the presence of depressive-like behaviors and euthanized to detect BDNF/mTOR signaling using immunoblots. DBS at the vmPFC significantly ameliorated depressive-like behaviors and spatial learning and memory deficits in the CUS rats. Furthermore, DBS restored the reduced synaptic density in the hippocampus induced by CUS and increased the expression or activity of BDNF, Akt, and mTOR in the hippocampus. Thus, the antidepressant-like effects and cognitive improvement produced by vmPFC DBS might be mediated through increased activity of the BDNF/mTOR signaling pathway.

Engineering in vitro human neural tissue analogs by 3D bioprinting and electrostimulation

There is a fundamental need for clinically relevant, reproducible, and standardized in vitro human neural tissue models, not least of all to study heterogenic and complex human-specific neurological (such as neuropsychiatric) disorders. Construction of three-dimensional (3D) bioprinted neural tissues from native human-derived stem cells (e.g., neural stem cells) and human pluripotent stem cells (e.g., induced pluripotent) in particular is appreciably impacting research and conceivably clinical translation. Given the ability to artificially and favorably regulate a cell's survival and behavior by manipulating its biophysical environment, careful consideration of the printing technique, supporting biomaterial and specific exogenously delivered stimuli, is both required and advantageous. By doing so, there exists an opportunity, more than ever before, to engineer advanced and precise tissue analogs that closely recapitulate the morphological and functional elements of natural tissues (healthy or diseased). Importantly, the application of electrical stimulation as a method of enhancing printed tissue development in vitro, including neuritogenesis, synaptogenesis, and cellular maturation, has the added advantage of modeling both traditional and new stimulation platforms, toward improved understanding of efficacy and innovative electroceutical development and application.

The neuroscience of positive emotions and affect: Implications for cultivating happiness and wellbeing

This review paper provides an integrative account regarding neurophysiological correlates of positive emotions and affect that cumulatively contribute to the scaffolding for happiness and wellbeing in humans and other animals. This paper reviews the associations among neurotransmitters, hormones, brain networks, and cognitive functions in the context of positive emotions and affect. Consideration of lifespan developmental perspectives are incorporated, and we also examine the impact of healthy social relationships and environmental contexts on the modulation of positive emotions and affect. The neurophysiological processes that implement positive emotions are dynamic and modifiable, and meditative practices as well as flow states that change patterns of brain function and ultimately support wellbeing are also discussed. This review is part of "The Human Affectome Project" (http://neuroqualia.org/background.php), and in order to advance a primary aim of the Human Affectome Project, we also reviewed relevant linguistic dimensions and terminology that characterizes positive emotions and wellbeing. These linguistic dimensions are discussed within the context of the neuroscience literature with the overarching goal of generating novel recommendations for advancing neuroscience research on positive emotions and wellbeing.

Examining cognitive change in magnetic resonance-guided focused ultrasound capsulotomy for psychiatric illness

Magnetic resonance-guided focused ultrasound (MRgFUS) anterior capsulotomy is a novel treatment option for patients with refractory obsessive compulsive disorder (OCD) or major depressive disorder (MDD). However, there is concern that lesional psychiatric surgery procedures may have adverse effects on cognition. In this study, we examined whether MRgFUS capsulotomy causes cognitive decline in patients with psychiatric illness. Ten patients with refractory OCD (n = 5) or MDD (n = 5) underwent MRgFUS capsulotomy. Cognitive functioning was measured at baseline as well as 6 months and 12 months postoperatively, with a battery of neuropsychological tests assessing domains of executive function, memory, and processing speed. Scores were analyzed at the individual-level, and changes ≥2 standard deviations were considered clinically significant. We also examined whether changes in clinical symptoms were associated with changes in cognitive performance. At baseline intellectual functioning was in the average to high-average range for the group. Following MRgFUS capsulotomy, there were no deteriorations in cognition that reached ≥2 standard deviations at 6 or 12 months. Eight out of ten patients demonstrated a ≥2 standard deviation improvement in at least one cognitive score at 6 or 12 months postoperatively. Improvements in clinical symptoms correlated significantly with self-reported improvements in frontal lobe function (p < 0.05), but not with objective measures of cognitive functioning. To summarize, MRgFUS capsulotomy did not result in cognitive decline in this cohort of patients with refractory OCD or MDD, suggesting that this procedure can be offered to patients with a very low risk of cognitive side effects.

A Decade of Progress in Deep Brain Stimulation of the Subcallosal Cingulate for the Treatment of Depression

Major depression contributes significantly to the global disability burden. Since the first clinical study of deep brain stimulation (DBS), over 446 patients with depression have now undergone this neuromodulation therapy, and 29 animal studies have investigated the efficacy of subgenual cingulate DBS for depression. In this review, we aim to provide a comprehensive overview of the progress of DBS of the subcallosal cingulate in humans and the medial prefrontal cortex, its rodent homolog. For preclinical animal studies, we discuss the various antidepressant-like behaviors induced by medial prefrontal cortex DBS and examine the possible mechanisms including neuroplasticity-dependent/independent cellular and molecular changes. Interestingly, the response rate of subcallosal cingulate Deep brain stimulation marks a milestone in the treatment of depression. DBS achieved response and remission rates of 64–76% and 37–63%, respectively, from clinical studies monitoring patients from 6–24 months. Although some studies showed its stimulation efficacy was limited, it still holds great promise as a therapy for patients with treatment-resistant depression. Overall, further research is still needed, including more credible clinical research, preclinical mechanistic studies, precise selection of patients, and customized electrical stimulation paradigms.

Using Deep Brain Stimulation to Unravel the Mysteries of Cardiorespiratory Control

This article charts the history of deep brain stimulation (DBS) as applied to alleviate a number of neurological disorders, while in parallel mapping the electrophysiological circuits involved in generating and integrating neural signals driving the cardiorespiratory system during exercise. With the advent of improved neuroimaging techniques, neurosurgeons can place small electrodes into deep brain structures with a high degree accuracy to treat a number of neurological disorders, such as movement impairment associated with Parkinson's disease and neuropathic pain. As well as stimulating discrete nuclei and monitoring autonomic outflow, local field potentials can also assess how the neurocircuitry responds to exercise. This technique has provided an opportunity to validate in humans putative circuits previously identified in animal models. The central autonomic network consists of multiple sites from the spinal cord to the cortex involved in autonomic control. Important areas exist at multiple evolutionary levels, which include the anterior cingulate cortex (telencephalon), hypothalamus (diencephalon), periaqueductal grey (midbrain), parabrachial nucleus and nucleus of the tractus solitaries (brainstem), and the intermediolateral column of the spinal cord. These areas receive afferent input from all over the body and provide a site for integration, resulting in a coordinated efferent autonomic (sympathetic and parasympathetic) response. In particular, emerging evidence from DBS studies have identified the basal ganglia as a major sub-cortical cognitive integrator of both higher center and peripheral afferent feedback. These circuits in the basal ganglia appear to be central in coupling movement to the cardiorespiratory motor program. © 2020 American Physiological Society. Compr Physiol 10:1085-1104, 2020.

Effects of magnetic seizure therapy on anterograde and retrograde amnesia in treatment-resistant depression

BACKGROUND

Electroconvulsive therapy (ECT) is the gold standard for treatment-resistant depression (TRD). However, cognitive side effects, mainly anterograde and retrograde amnesia, frequently occur. Magnetic seizure therapy (MST) is tested using more focal seizure induction. However, the suggestion MST may be more beneficial than ECT because it causes fewer amnesia have not yet been comprehensively investigated using common neuropsychological testing specifically for ECT. We aimed to examine whether MST causes anterograde and retrograde amnesia.

METHODS

Ten patients with TRD were treated with MST (8.9 [2] treatments) at 100% machine output, a frequency of 100 Hz and 657.4 (62) pulses per train. The short form of the Autobiographical Memory Inventory was administered to test retrograde amnesia. Furthermore, an extended neuropsychological test battery, including verbal and nonverbal recall as well as recognition tasks, was used.

RESULTS

We observed changes in retrograde amnesia, although they were not clinically relevant (mean: -0.42 ± 0.14). Furthermore, no anterograde amnesia as well as no effects on global cognitive status, attention, language, and executive functions after MST were measured.

CONCLUSIONS

The cognitive safety and efficacy of MST in patients with TRD were indicated. However, the main limitations of the present study were the small sample and as a consequence, the low statistical power to detect changes after treatment. Therefore, our findings require replication in further studies. In addition, a direct comparison between MST and ECT in a larger sample should be performed before MST can be discussed as an alternative treatment approach to ECT in clinical practice.

Long-term Sustained Cognitive Benefits of Vagus Nerve Stimulation in Refractory Depression

BACKGROUND

Treatment-resistant depression (TRD) is a serious chronic condition disabling patients functionally and cognitively. Chronic vagus nerve stimulation (VNS) is recognized for the management of TRD, but few studies have examined its long-term effects on cognitive dysfunction in unipolar and bipolar resistant depression.

OBJECTIVE

The purpose of this study was to assess the course of cognitive functions and clinical symptoms in a cohort of patients treated with VNS for TRD.

METHODS

In 14 TRD patients with VNS, standardized clinical and neuropsychological measures covering memory, attention/executive functions, and psychomotor speed were analyzed prestimulation and up to 2 years poststimulation.

RESULTS

Vagus nerve stimulation patients significantly improved on cognitive and clinical measures. Learning and memory improved rapidly after 1 month of stimulation, and other cognitive functions improved gradually over time. Cognitive improvements were sustained up to 2 years of treatment. At 1 month, improvement in Montgomery-Åsberg Depression Rating Scale scores was not correlated with changes in any of the cognitive scores, whereas at 12 months, the change in Montgomery-Åsberg Depression Rating Scale score was significantly correlated with several measures (Stroop interference, verbal fluency, and Rey-Osterrieth Complex Figure delayed recall).

CONCLUSIONS

In recent years, a growing interest in cognitive dysfunction in depression has emerged. Our results suggest that chronic VNS produces sustained clinical and cognitive improvements in TRD patients, with some mental functions improving as soon as 1 month after the initiation of the VNS therapy. Vagus nerve stimulation seems a very promising adjunctive therapy for TRD patients with cognitive impairment.

Deep brain stimulation targets for treating depression

Deep brain stimulation (DBS) is a new therapeutic approach for treatment-resistant depression (TRD). There is a preliminary evidence of the efficacy and safety of DBS for TRD in the subgenual anterior cingulate cortex, the ventral capsule/ventral striatum, the nucleus accumbens, the lateral habenula, the inferior thalamic peduncle, the medial forebrain bundle, and the bed nucleus of the stria terminalis. Optimal stimulation targets, however, have not yet been determined. Here we provide updated knowledge substantiating the suitability of each of the current and potential future DBS targets for treating depression. In this review, we discuss the future outlook for DBS treatment of depression in light of the fact that antidepressant effects of DBS can be achieved using different targets.

Longitudinal neuropsychological outcomes in treatment-resistant depression following bed nucleus of the stria terminalis-area deep brain stimulation: a case review

Studies have demonstrated the effectiveness of deep brain stimulation (DBS) as a treatment modality for psychiatric conditions. We present a case reviewing the longitudinal neuropsychological performance outcomes following bed nucleus of the stria terminalis-area (BNST) DBS in a patient with treatment-resistant depression (TRD). The cognitive safety of DBS is well documented for various targets, however cognitive outcomes of BNST-area DBS have not been extensively reported for patients with TRD. Neuropsychological assessment was conducted pre- and post-DBS. Twelve months following DBS, augmented general cognitive performance was observed with significant changes in specific domains.

Diffusion Tensor Imaging Investigation of Uncinate Fasciculus Anatomy in Healthy Controls: Description of a Subgenual Stem

The uncinate fasciculus is the largest white matter association tract connecting the prefrontal cortex and the anteromedial temporal lobe. The traditional anatomical description outlines a temporal stem that hooks around the posterior insula, a subinsular body, and 2 prefrontal stems extending to the lateral orbital gyri and the frontopolar cortex. Recent imaging studies of the white matter tracts deep to the subgenual cingulate gyrus (Brodmann area 25: BA25) suggest the presence of white matter fibers extending from BA25 to the amygdala, via a route that would run in close proximity to the uncinate fasciculus, that are of functional importance in mood disorders. We hypothesized that these fibers represent a third, medial prefrontal stem of the uncinate fasciculus. Using diffusion tensor imaging in 74 healthy volunteer humans, we seeded the uncinate fasciculus using 2 regions of interest centered over the temporal stem and the caudal body of the uncinate fasciculus in the coronal plane at the level of the anterior commissure. A medial prefrontal stem extending to the subgenual cingulate gyrus was demonstrated in 65/74 left and 70/74 right cerebral hemispheres, and had a mean fractional anisotropy value of 0.43 (95% CI 0.40-0.47). The medial subgenual stem fibers were inseparable from the caudal body and temporal stem of the main uncinate fasciculus and followed the same hook-shaped morphology. A probable medial subgenual prefrontal stem of the uncinate fasciculus was demonstrated in a cohort of healthy volunteers and is of potential significance in our understanding of neuropsychiatry and mood disorders.

Deep brain stimulation for treatment-resistant depression: an integrative review of preclinical and clinical findings and translational implications

Although deep brain stimulation (DBS) is an established treatment choice for Parkinson's disease (PD), essential tremor and movement disorders, its effectiveness for the management of treatment-resistant depression (TRD) remains unclear. Herein, we conducted an integrative review on major neuroanatomical targets of DBS pursued for the treatment of intractable TRD. The aim of this review article is to provide a critical discussion of possible underlying mechanisms for DBS-generated antidepressant effects identified in preclinical studies and clinical trials, and to determine which brain target(s) elicited the most promising outcomes considering acute and maintenance treatment of TRD. Major electronic databases were searched to identify preclinical and clinical studies that have investigated the effects of DBS on depression-related outcomes. Overall, 92 references met inclusion criteria, and have evaluated six unique DBS targets namely the subcallosal cingulate gyrus (SCG), nucleus accumbens (NAc), ventral capsule/ventral striatum or anterior limb of internal capsule (ALIC), medial forebrain bundle (MFB), lateral habenula (LHb) and inferior thalamic peduncle for the treatment of unrelenting TRD. Electrical stimulation of these pertinent brain regions displayed differential effects on mood transition in patients with TRD. In addition, 47 unique references provided preclinical evidence for putative neurobiological mechanisms underlying antidepressant effects of DBS applied to the ventromedial prefrontal cortex, NAc, MFB, LHb and subthalamic nucleus. Preclinical studies suggest that stimulation parameters and neuroanatomical locations could influence DBS-related antidepressant effects, and also pointed that modulatory effects on monoamine neurotransmitters in target regions or interconnected brain networks following DBS could have a role in the antidepressant effects of DBS. Among several neuromodulatory targets that have been investigated, DBS in the neuroanatomical framework of the SCG, ALIC and MFB yielded more consistent antidepressant response rates in samples with TRD. Nevertheless, more well-designed randomized double-blind, controlled trials are warranted to further assess the efficacy, safety and tolerability of these more promising DBS targets for the management of TRD as therapeutic effects have been inconsistent across some controlled studies.

Deep brain stimulation of the subcallosal cingulate gyrus in patients with treatment-resistant depression: A double-blinded randomized controlled study and long-term follow-up in eight patients

BACKGROUND

Deep brain stimulation (DBS) of the subcallosal cingulate gyrus (SCG) is an experimental approach in treatment-resistant depression (TRD). Short-term results of efficacy in DBS are incongruent and studies investigating long-term effects are warranted.

METHODS

We assessed efficacy of SCG-DBS in eight patients randomized into a delayed-onset group (sham-DBS four weeks) and a non-delayed-onset group. The primary outcome measure was improvement on the Hamilton Depression Rating-Scale (HAMD-24-item-version). Response was defined as HAMD-24 reduction of at least 50% compared to baseline. Assessment was double-blind for a period of eight weeks and after 6,- 12,- 24,- and 28,- months open-label.

RESULTS

The average improvement in HAMD-24 scores after 6,- 12,- and 24-months were 34%, 25%, and 37%. After 6 months, HAMD-24 revealed a significant difference (P = .022) and 37.5% of the patients were responders. After 12 months, HAMD-24 scores dropped, but no significant difference was observed. After 24 months, a significant improvement was found (P = .041). After the four weeks lasting sham vs. DBS-ON period, there was no group difference (P = .376) in HAMD-24 and patients did not improve during sham stimulation. Patients were followed until 28 months and two up to 4 years under SCG-DBS and average response rate was 51%, whereas two patients were remitters (33,3%).

LIMITATIONS

The small sample size limited the statistical power and external validity.

CONCLUSIONS

Long-term improvement after SCG-DBS revealed a stable effect. There was no significant difference in response rates between the delayed and non-delayed-onset group. DBS for TRD remains experimental and longitudinal investigations of large samples are needed.

Impact of deep brain stimulation of the ventral anterior limb of the internal capsule on cognition in depression

BACKGROUND

Preliminary studies report no negative and a possible positive impact of deep brain stimulation (DBS) on cognition of patients with treatment-resistant depression (TRD). However, these studies neither controlled for practice effects nor compared active with sham stimulation.

METHOD

To address these limitations, we compared 25 TRD patients, who underwent DBS of the ventral anterior limb of the internal capsule (vALIC), with 21 healthy controls (HCs) matched on gender, age and education level. Both groups did subtests of the Cambridge Neuropsychological Test Automated Battery assessing verbal and visuospatial memory, attention, cognitive flexibility, psychomotor functioning, planning and object naming. TRD patients were tested 3 weeks prior to DBS surgery (baseline), 3 weeks following surgery (T1) and following 52 weeks of DBS optimization (T2). HCs were tested at baseline, 6 weeks following baseline (T1) and 20-24 weeks following baseline (T2). Subsequently, TRD patients entered a randomized, double-blind crossover phase, in which they were tested in an active and a sham stimulation phase.

RESULTS

TRD patients did not improve on a test of immediate verbal recognition from baseline to T1, whereas HCs did (group x time: p = 0.001). Both TRD patients and HCs improved over sessions on tests measuring delayed verbal recall, visuospatial memory, planning and object naming (all p < 0.01). Active and sham stimulation did not have an impact on any of the tests differentially.

CONCLUSIONS

vALIC DBS neither has a lasting positive nor negative impact on cognition in TRD patients. DBS surgery might have a temporary negative effect on verbal memory.

Closed-loop neuromodulation systems: next-generation treatments for psychiatric illness

Despite deep brain stimulation's positive early results in psychiatric disorders, well-designed clinical trials have yielded inconsistent clinical outcomes. One path to more reliable benefit is closed-loop therapy: stimulation that is automatically adjusted by a device or algorithm in response to changes in the patient's electrical brain activity. These interventions may provide more precise and patient-specific treatments. This article first introduces the available closed-loop neuromodulation platforms, which have shown clinical efficacy in epilepsy and strong early results in movement disorders. It discusses the strengths and limitations of these devices in the context of psychiatric illness. It then describes emerging technologies to address these limitations, including pre-clinical developments such as wireless deep neurostimulation and genetically targeted neuromodulation. Finally, ongoing challenges and limitations for closed-loop psychiatric brain stimulation development, most notably the difficulty of identifying meaningful biomarkers for titration, are discussed. This is considered in the recently-released Research Domain Criteria (RDoC) framework, and how neuromodulation and RDoC are jointly very well suited to address the problem of treatment-resistant illness is described.

Neurocognitive Predictors of Response in Treatment Resistant Depression to Subcallosal Cingulate Gyrus Deep Brain Stimulation

Background: Deep brain stimulation (DBS) is a neurosurgical intervention with demonstrated effectiveness for treatment resistant depression (TRD), but longitudinal studies on the stability of cognitive parameters following treatment are limited. The objectives of this study are to (i) identify baseline cognitive predictors of treatment response to subcallosal cingulate gyrus (SCG) DBS for unipolar TRD and (ii) compare neurocognitive performance prior to and 12 months after DBS implantation.

Methods: Twenty unipolar TRD patients received SCG DBS for 12 months. A standardized neuropsychological battery was used to assess a range of neurocognitive abilities at baseline and after 12 months. Severity of depression was evaluated using the 17 item Hamilton Rating Scale for Depression.

Results: Finger Tap-Dominant Hand Test and total number of errors made on the Wisconsin Card Sorting Test predicted classification of patients as treatment responders or non-responders, and were independent of improvement in mood. Change in verbal fluency was the only neuropsychological test that correlated with change in mood from baseline to the follow up period. None of the neuropsychological measures displayed deterioration in cognitive functioning from baseline to repeat testing at 12 months.

Limitations: This was an open label study with a small sample size which limits predictive analysis. Practice effects of the neuropsychological testing could explain the improvement from baseline to follow up on some tasks. Replication using a larger sample of subjects who received neuropsychological testing before and at least 12 months after DBS surgery is required.

Conclusion: These preliminary results (i) suggest that psychomotor speed may be a useful baseline predictor of response to SCG DBS treatment and (ii) support previous suggestions that SCG DBS has no deleterious effects on cognition.

Deep brain stimulation to the medial forebrain bundle for depression- long-term outcomes and a novel data analysis strategy

BACKGROUND

Deep brain stimulation (DBS) of the supero-lateral branch of the medial forebrain bundle (slMFB) in treatment-resistant depression (TRD) is associated with acute antidepressant effects.

OBJECTIVE

Long-term clinical effects including changes in quality of life, side effects and cognition as well as long-term data covering four years are assessed.

METHODS

Eight TRD patients were treated with DBS bilateral to the slMFB. Primary outcome measure was a 50% reduction in Montgomery-Åsberg Depression Rating Scale (MADRS) (response) and remission (MADRS <10) at 12 months compared to baseline. Secondary measures were anxiety, general functioning, quality of life, safety and cognition assessed for 4 years. Data is reported as conventional endpoint-analysis and as area under the curve (AUC) timeline analysis.

RESULTS

Six of eight patients (75%) were responders at 12 months, four patients reached remission. Long-term results revealed a stable effect up to four years. Antidepressant efficacy was also reflected in the global assessment of functioning. Main side effect was strabismus at higher stimulation currents. No change in cognition was identified. AUC analysis revealed a significant reduction in depression for 7/8 patients in most months.

CONCLUSIONS

Long-term results of slMFB-DBS suggest acute and sustained antidepressant effect; timeline analysis may be an alternative method reflecting patient's overall gain throughout the study. Being able to induce a rapid and robust antidepressant effect even in a small, sample of TRD patients without significant psychiatric comorbidity, render the slMFB an attractive target for future studies.

Review on Factors Affecting Targeting Accuracy of Deep Brain Stimulation Electrode Implantation between 2001 and 2015

BACKGROUND

Accurate implantation of a depth electrode into the brain is of the greatest importance in deep brain stimulation (DBS), and various stereotactic systems have been developed for electrode implantation. However, an updated analysis of depth electrode implantation in the modern era of DBS is lacking.

OBJECTIVE

This study aims at providing an updated review on targeting accuracy of DBS electrode implantation by analyzing contemporary DBS electrode implantation operations from the perspective of precision engineering.

METHODS

Eligible articles with information on targeting accuracy of DBS electrode implantation were searched in the PubMed database.

RESULTS

An average targeting error of DBS electrode implantation is reported to decrease toward 1 mm; the standard deviation of targeting error is decreasing toward 0.5 mm. Targeting accuracy is not only found to be affected by individual surgical steps, but also systematically affected by the architecture of the implantation operation.

CONCLUSION

A systematic strategy should be adopted to further improve the targeting accuracy of depth electrode implantation. Attention should be paid to optimizing the whole electrode implantation operation, which can help minimize error accumulation or amplification throughout the serially connected procedures for DBS electrode implantation.

A systematic review of psychiatric indications for deep brain stimulation, with focus on major depressive and obsessive-compulsive disorder

BACKGROUND

Deep brain stimulation is a treatment under investigation for a range of psychiatric disorders. It has shown promising results for therapy-refractory obsessive-compulsive disorder (OCD) and major depressive disorder (MDD). Other indications under investigation include Tourette's syndrome, anorexia nervosa and substance use disorders.

AIMS

To review current studies on psychiatric indications for deep brain stimulation (DBS), with focus on OCD and MDD.

METHOD

A systematic search was carried out in MEDLINE, and the literature was searched to identify studies with DBS for psychiatric disorders. The identified studies were analysed based on patient characteristics, treatment results and adverse effects of DBS.

RESULTS

A total of 52 papers met the inclusion criteria and described a total of 286 unique patients treated with DBS for psychiatric indications; 18 studies described 112 patients treated with DBS for OCD in six different anatomical targets, while nine studies presented 100 patients with DBS for MDD in five different targets.

CONCLUSION

DBS may show promise for treatment-resistant OCD and MDD but the results are limited by small sample size and insufficient randomized controlled data. Deep brain stimulation for OCD has received United States Food and Drug Administration approval. Other psychiatric indications are currently of a purely experimental nature.

Cognitive safety of dorsomedial prefrontal repetitive transcranial magnetic stimulation in major depression

The most widely used target for repetitive transcranial magnetic stimulation (rTMS) in treatment-resistant depression (TRD) is the dorsolateral prefrontal cortex (DLPFC). Despite convergent evidence that the dorsomedial prefrontal cortex (DMPFC) may be a promising alternative target for rTMS in TRD, its cognitive safety profile has not previously been assessed. Here, we applied 20 sessions of rTMS to the DMPFC in 21 TRD patients. Before and after treatment, a battery of neuropsychological tasks was administered to evaluate changes in cognition across three general cognitive domains: learning and memory, attention and processing speed, and cognitive flexibility. Subjects also completed the 17-item Hamilton Rating Scale for Depression (HamD17) prior to and following treatment to measure changes in severity of depressive symptoms, and to assess the relationship between mood and cognitive performance over the course of treatment. No serious adverse effects or significant deterioration in cognitive performance were observed. Overall, subjects improved significantly on Stroop Inhibition/Switching and on Trails B, and this improvement was independent of the degree of improvement in depression symptoms. No domains or items significantly predicted clinical outcome, with the exception of baseline performance on Visual Elevator Accuracy. Clinical improvement correlated to improved performance in the overall domain of attention and processing speed, although this effect was not evident following covariate adjustment. DMPFC-rTMS did not produce any detectable cognitive adverse effects during treatment of TRD. Performance did not deteriorate significantly on any measures. Taken together, the present findings support the tolerability and cognitive safety of DMPFC-rTMS in refractory depression.

Electrical stimulation of the vmPFC serves as a remote control to affect VTA activity and improve depressive-like behavior

Despite progress in elucidating mechanisms of depression, the efficacy of different treatments remains inadequate. Recent small-scale clinical studies suggested anti-depressant treatment using deep brain stimulation (DBS) of the ventral capsule/ventral striatum or subgenual cingulate cortex (SCC), yet controlled, multi-center trials were unsuccessful. We recently suggested the ventral tegmental area (VTA) as an important intersection for treating depression. We also found that stimulation of the VTA of a genetic rat model of depression (Flinders Sensitive Line (FSL) rats) with a programmed pattern designed to mimic the burst firing of normal rats decreases depressive-like behavior. Herein, we examined the possibility of reaching the VTA - located deep in the brain stem - through its direct connection to the ventro-medial prefrontal cortex (vmPFC), which parallels the human SCC. Thus, we compared treatment of FSLs with modified versions of DBS - either chronic-intermittent low-frequency electrical stimulation of the vmPFC, or patterned acute electrical stimulation (pAES), which integrates transcranial magnetic stimulation properties, namely, bursts of pulse trains and low frequency stimulation, applied to the VTA. We found that stimulation of the vmPFC (20Hz, 15min/day, 10days) improved depressive-like behavior and VTA local field potential (LFP) activity of FSLs, yet it had only a partial long-term effect on behavior. In particular, vmPFC stimulation decreased theta band activity, which correlated with the improvement in depressive-like behavior of all treated FSLs at day 1, and in ~50% of treated FSLs at day 28 post treatment. pAES of the VTA (10Hz, 20min) caused significant, long-term improvement of depressive-like behavior of FSLs, concurrently with normalizing intra-VTA LFP activity, and increasing VTA LFP synchronicity and hippocampal BDNF mRNA levels. Thus, although low-frequency electrical stimulation of the PFC alters VTA activity, leading to attenuation of depressive-like manifestations, a specific stimulation pattern affecting VTA cell programming is important for long-term efficacy.

Update on Neuromodulation for Treatment-Resistant Depression

About 30% of patients suffering from a major depressive disorder do not respond sufficiently to established pharmacological, psychotherapeutic, or somatic treatments. Advances in technology and emerging knowledge about the dysfunctional brain circuits underlying depression have led to the development of different neuromodulation techniques. The aim of the present review is to give an update on noninvasive techniques, such as electroconvulsive therapy (ECT), magnetic seizure therapy (MST), transcranial magnetic stimulation (TMS), and invasive techniques requiring brain surgery, such as vagus nerve stimulation (VNS) and deep brain stimulation (DBS). First, the clinical relevance for therapy-resistant depression, including the current level of evidence, are presented. Neuroethics is concerned with the ethical, legal and social policy implications of neuroscience. A second focus of the review is the application of fundamental ethical principles, such as patient autonomy, patient well-being and justice to neuromodulation therapies. Due to reduced availability and lacking long-term efficacy data, most patients with treatment-resistant depression face a trial-and-error approach to therapeutics. This contravenes the ethical criteria of patient autonomy and justice. In order to raise the level of evidence, financial support of long-term studies, including large samples and randomized control trials, are necessary.

Deep brain stimulation in mental health: Review of evidence for clinical efficacy

OBJECTIVE

There is increasing interest in the use of deep brain stimulation as a treatment for psychiatric disorders. In this review, we consider the evidence for the effectiveness of deep brain stimulation for psychiatric indications, with a primary focus on obsessive compulsive disorder and major depressive disorder.

METHODS

Case reports, case series and clinical trials where deep brain stimulation was primarily utilised in the treatment of a psychiatric disorder, including obsessive compulsive disorder, major depressive disorder, anorexia nervosa or an addictive disorder were identified. The evidence for the effectiveness of deep brain stimulation in the treatment of obsessive compulsive disorder and major depressive disorder was reviewed with studies clustered by the site of implantation.

RESULTS

The majority of identified manuscripts report small case series or single cases. A limited number of studies have reported some form of randomised or blinded stimulation comparison. All of these comparative reports have included small samples of subjects (less than 20 per study in total) compromising the feasibility of making statistical comparison between outcomes in the comparison phases. The two exceptions to this have been industry-sponsored studies conducted in the treatment of major depressive disorder. However, both were stopped prematurely due to concerns about poor efficacy.

CONCLUSIONS

There is insufficient evidence at this point in time to support the use of deep brain stimulation as a clinical treatment for any psychiatric disorder outside of research and programmes where formal outcome data are being systematically collated. While some promising initial data exist to support its potential efficacy for a number of psychiatric conditions, further research is required to establish optimal implantation targets, patient characteristics associated with positive therapeutic outcomes and optimal deep brain stimulation parameters and parameter-programming methods.

Deep brain stimulation for psychiatric disorders: where we are now

Fossil records showing trephination in the Stone Age provide evidence that humans have sought to influence the mind through physical means since before the historical record. Attempts to treat psychiatric disease via neurosurgical means in the 20th century provided some intriguing initial results. However, the indiscriminate application of these treatments, lack of rigorous evaluation of the results, and the side effects of ablative, irreversible procedures resulted in a backlash against brain surgery for psychiatric disorders that continues to this day. With the advent of psychotropic medications, interest in invasive procedures for organic brain disease waned.

Diagnosis and classification of psychiatric diseases has improved, due to a better understanding of psychiatric patho-physiology and the development of disease and treatment biomarkers. Meanwhile, a significant percentage of patients remain refractory to multiple modes of treatment, and psychiatric disease remains the number one cause of disability in the world. These data, along with the safe and efficacious application of deep brain stimulation (DBS) for movement disorders, in principle a reversible process, is rekindling interest in the surgical treatment of psychiatric disorders with stimulation of deep brain sites involved in emotional and behavioral circuitry.

This review presents a brief history of psychosurgery and summarizes the development of DBS for psychiatric disease, reviewing the available evidence for the current application of DBS for disorders of the mind.

Reinforcement learning in depression: A review of computational research

Despite being considered primarily a mood disorder, major depressive disorder (MDD) is characterized by cognitive and decision making deficits. Recent research has employed computational models of reinforcement learning (RL) to address these deficits. The computational approach has the advantage in making explicit predictions about learning and behavior, specifying the process parameters of RL, differentiating between model-free and model-based RL, and the computational model-based functional magnetic resonance imaging and electroencephalography. With these merits there has been an emerging field of computational psychiatry and here we review specific studies that focused on MDD. Considerable evidence suggests that MDD is associated with impaired brain signals of reward prediction error and expected value ('wanting'), decreased reward sensitivity ('liking') and/or learning (be it model-free or model-based), etc., although the causality remains unclear. These parameters may serve as valuable intermediate phenotypes of MDD, linking general clinical symptoms to underlying molecular dysfunctions. We believe future computational research at clinical, systems, and cellular/molecular/genetic levels will propel us toward a better understanding of the disease.

Feasibility and safety of continuous and chronic bilateral deep brain stimulation of the medial forebrain bundle in the naïve Sprague-Dawley rat

OBJECTIVE

Deep brain stimulation (DBS) of the superolateral branch of the medial forebrain bundle (MFB) has provided rapid and dramatic reduction of depressive symptoms in a clinical trial. Early intracranial self-stimulation experiments of the MFB suggested detrimental side effects on the animals' health; therefore, the current study looked at the viability of chronic and continuous MFB-DBS in rodents, with particular attention given to welfare issues and identification of stimulated pathways.

METHODS

Sprague-Dawley female rats were submitted to stereotactic microelectrode implantation into the MFB. Chronic continuous DBS was applied for 3-6 weeks. Welfare monitoring and behavior changes were assessed. Postmortem histological analysis of c-fos protein expression was carried out.

RESULTS

MFB-DBS resulted in mild and temporary weight loss in the animals, which was regained even with continuing stimulation. MFB-DBS led to increased and long-lasting c-fos expression in target regions of the mesolimbic/mesocortical system.

CONCLUSIONS

Bilateral continuous chronic MFB-DBS is feasible, safe, and without impact on the rodent's health. MFB-DBS results in temporary increase in exploration, which could explain the initial weight loss, and does not produce any apparent behavioral abnormalities. This platform represents a powerful tool for further preclinical investigation of the MFB stimulation in the treatment of depression.

The medial forebrain bundle as a deep brain stimulation target for treatment resistant depression: A review of published data

INTRODUCTION

Despite a wide variety of therapeutic interventions for major depressive disorder (MDD), treatment resistant depression (TRD) remains to be prevalent and troublesome in clinical practice. In recent years, deep brain stimulation (DBS) has emerged as an alternative for individuals suffering from TRD not responding to combining antidepressants, multiple adjunctive strategies and electroconvulsive therapy (ECT). Although the best site for TRD-DBS is still unclear, pilot data suggests that the medial forebrain bundle (MFB) might be a key target to accomplish therapeutic efficacy in TRD patients.

OBJECTIVE

To explore the anatomic, electrophysiologic, neurocognitive and treatment data supporting the MFB as a target for TRD-DBS.

RESULTS

The MFB connects multiple targets involved in motivated behavior, mood regulation and antidepressant response. Specific phenomenology associated with TRD can be linked specifically to the superolateral branch (sl) of the MFB (slMFB). TRD patients who received DBS-slMFB reported high response/remission rates with an improvement in functioning and no significant adverse outcomes in their physical health or neurocognitive performance.

DISCUSSION

The slMFB is an essential component of a network of structural and functional pathways connecting different areas possibly involved in the pathogenesis of mood disorders. Therefore, the slMFB should be considered as an exciting therapeutic target for DBS therapy to achieve a sustained relief in TRD patients.

CONCLUSION

There is an urgent need for clinical trials exploring DBS-slMFB in TRD. Further efforts should pursue measuring baseline pro-inflammatory cytokines, oxidative stress, and cognition as possible biomarkers of DBS-slMFB response in order to aid clinicians in better patient selection.

Magnetic seizure therapy in treatment-resistant depression: clinical, neuropsychological and metabolic effects

BACKGROUND

Magnetic seizure therapy (MST), despite being in an early phase of clinical research, has been demonstrated to be associated with antidepressant efficacy. However, safety, tolerability and efficacy data in connection with functional brain activity from larger samples are lacking. The aim of this study was to determine clinical and cognitive effects of MST and the influence of MST on regional brain glucose metabolism.

METHOD

Twenty-six patients suffering from treatment-resistant depression (TRD) underwent MST. Ten patients underwent a randomized trial and 16 patients an open-label study design. The primary outcome criterion was the severity of depressive symptoms assessed with the Hamilton Depression Rating Scale (HAMD). Depressive symptoms, tolerability and cognitive safety, along with social functioning and quality of life parameters, were assessed using various rating scales. A clinical follow-up visit 6 months following the completion of a course of MST and [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) scans of 12 patients were analysed.

RESULTS

A significant response to MST was demonstrated by 69% of the patient sample, with 46% meeting remission criteria. Anxiety ratings were significantly reduced in responders and their quality of life was improved. Half of the responders relapsed within 6 months. No cognitive side-effects were observed. FDG-PET scans showed a metabolic increase in the frontal cortex bilaterally and a decrease in the left striatum.

CONCLUSIONS

Robust antidepressant and anti-anxiety efficacy of MST was demonstrated, and found to be associated with localized metabolic changes in brain areas that are strongly implicated in depression. Thus, MST presents an effective, well-tolerated and safe treatment option for patients unable to respond to other forms of therapy for depression.

A novel combinational approach of microstimulation and bioluminescence imaging to study the mechanisms of action of cerebral electrical stimulation in mice

Deep brain stimulation (DBS) is used to treat a number of neurological conditions and is currently being tested to intervene in neuropsychiatric conditions. However, a better understanding of how it works would ensure that side effects could be minimized and benefits optimized. We have thus developed a unique device to perform brain stimulation (BS) in mice and to address fundamental issues related to this methodology in the pre-clinical setting. This new microstimulator prototype was specifically designed to allow simultaneous live bioluminescence imaging of the mouse brain, allowing real time assessment of the impact of stimulation on cerebral tissue. We validated the authenticity of this tool in vivo by analysing the expression of toll-like receptor 2 (TLR2), corresponding to the microglial response, in the stimulated brain regions of TLR2-fluc-GFP transgenic mice, which we further corroborated with post-mortem analyses in these animals as well as in human brains of patients who underwent DBS to treat their Parkinson's disease. In the present study, we report on the development of the first BS device that allows for simultaneous live in vivo imaging in mice. This tool opens up a whole new range of possibilities that allow a better understanding of BS and how to optimize its effects through its use in murine models of disease.

Cognitive functioning after deep brain stimulation in subcallosal cingulate gyrus for treatment-resistant depression: an exploratory study

Deep brain stimulation (DBS) is being investigated as a therapeutic alternative for patients with treatment-resistant depression (TRD), but its cognitive safety has been scarcely explored. The aim of this exploratory study is to evaluate cognitive function of patients before and after deep brain stimulation of the subgenual cingulate gyrus (SCG). Eight treatment-resistant depressed patients were implanted in subgenual cingulate gyrus. A neuropsychological battery was used to evaluate patients before surgery and 1-year after. A matched group of eight first-episode patients was also assessed. A MANOVA was performed for each cognitive domain and those tests showing main time effects were then correlated with depressive symptoms and with medication load. There were significant group and time effects for memory and a group effect for language. No significant interactions between groups or cognitive domains were observed. Medication load was negatively correlated with memory at time 1, and clinical change negatively correlated with memory improvement. These findings support the cognitive safety of DBS of subgenual cingulate gyrus, as cognitive function did not worsen after chronic stimulation and memory performance even improved. The results, though, should be interpreted cautiously given the small sample size and the fact that some treatment-resistant patients received electroconvulsive therapy (ECT) before implantation.

Programmed deep brain stimulation synchronizes VTA gamma band field potential and alleviates depressive-like behavior in rats

Deep brain stimulation (DBS) significantly alleviates symptoms in various neurological disorders. Current research focuses on developing programmed stimulation protocols for customization to individual symptoms. However, the therapeutic mechanism of action of programmed DBS (pDBS) is poorly understood. We previously demonstrated that pDBS in the ventral tegmental area (VTA) normalizes molecular and behavioral abnormalities in the Flinders Sensitive Line (FSL) rat model for depression. Herein, we examined the effect of a short-duration, low-frequency DBS template on local field potential (LFP) synchronization patterns along the anterior-posterior axis of the VTA of FSL rats, and correlation of this effect with depressive-like behavior, as compared with non-programmed, continuous low-frequency DBS (npDBS). We used the wavelet phase coherence (WPC) measure for effective representation of time and frequency of LFP patterns, and the forced swim test to measure immobility (despair). Baseline WPC values were lower in FSLs as compared with SD controls, at the low and high gamma frequency range (above 30 Hz). Baseline immobility scores for FSL rats were higher than those of SD rats, while pDBS, and not npDBS, significantly reduced FSL immobility scores to control SD levels, up to day 14. pDBS also significantly increased the change (between baseline and day 14) in WPC values, in beta, low gamma and high gamma frequency ranges. The change in high gamma (60-100 Hz) WPC values correlated with improvement in depressive-like behavior. Our results suggest that programmed DBS of the VTA increases interaction among local neuronal populations, an effect that may underlie the normalization of depressive-like behavior.

Deep brain stimulation in the treatment of depression

Major depressive disorder is a worldwide disease with debilitating effects on a patient's life. Common treatments include pharmacotherapy, psychotherapy, and electroconvulsive therapy. Many patients do not respond to these treatments; this has led to the investigation of alternative therapeutic modalities. Deep brain stimulation (DBS) is one of these modalities. It was first used with success for treating movement disorders and has since been extended to the treatment of psychiatric disorders. Although DBS is still an emerging treatment, promising efficacy and safety have been demonstrated in preliminary trials in patients with treatment-resistant depression (TRD). Further, neuroimaging has played a pivotal role in identifying some DBS targets and remains an important tool for evaluating the mechanism of action of this novel intervention. Preclinical animal studies have broadened knowledge about the possible mechanisms of action of DBS for TRD, Given that DBS involves neurosurgery in patients with severe psychiatric impairment, ethical questions concerning capacity to consent arise; these issues must continue to be carefully considered.

Neuropsychological function before and after subcallosal cingulate deep brain stimulation in patients with treatment-resistant depression

BACKGROUND

Treatment-resistant depression (TRD) is a pervasive and difficult to treat condition for which deep brain stimulation (DBS) of the subcallosal cingulate white matter (SCCwm) is an emerging therapeutic option. However, neuropsychological safety data for this novel treatment have only been published for a small number of subjects. Moreover, little is known regarding the neuropsychological profile present in TRD patients at baseline, prior to initiation of DBS therapy. This report describes the neuropsychological effects of TRD and acute and chronic DBS of the SCCwm in patients with unipolar and bipolar TRD.

METHODS

Patients with TRD (N = 17) were compared to a healthy control group (N = 15) on subtests from the Cambridge Neuropsychological Test Automated Battery and the Stroop Task. Patients were then tested again at subsequent time points of 1 and 6 months following the initiation of chronic DBS of the SCCwm.

RESULTS

Patients with TRD showed similar levels of performance to healthy controls on most neuropsychological measures, with the exception that the TRD group had slower processing speed. Patients with bipolar TRD, relative to those with unipolar TRD, obtained lower scores on measures of executive function and memory only at baseline. With acute and chronic SCCwm DBS, neuropsychological function improved in multiple domains including processing speed and executive function (planning, set shifting, response inhibition), and memory remained stable.

CONCLUSIONS

Patients with TRD show slowed processing speed but otherwise largely preserved neuropsychological functioning. DBS of the SCCwm does not result in worsening of any aspect of neuropsychological function and may improve certain domains. Future research is warranted to better understand the effects of TRD and DBS on neuropsychological function.

Deep brain stimulation for treatment-resistant depression: systematic review of clinical outcomes

Major depressive disorder (MDD) is a widespread, severe, debilitating disorder that markedly diminishes quality of life. Medication is commonly effective, but 20-30 % of patients are refractory to medical therapy. The surgical treatment of psychiatric disorders has a negative stigma associated with it owing to historical abuses. Various ablative surgeries for MDD have been attempted with marginal success, but these studies lacked standardized outcome measures. The recent development of neuromodulation therapy, especially deep brain stimulation (DBS), has enabled controlled studies with sham stimulation and presents a potential therapeutic option that is both reversible and adjustable. We performed a systematic review of the literature pertaining to DBS for treatment-resistant depression to evaluate the safety and efficacy of this procedure. We included only studies using validated outcome measures. Our review identified 22 clinical research papers with 5 unique DBS approaches using different targets, including nucleus accumbens, ventral striatum/ventral capsule, subgenual cingulate cortex, lateral habenula, inferior thalamic nucleus, and medial forebrain bundle. Among the 22 published studies, only 3 were controlled trials, and 2, as yet unpublished, multicenter, randomized, controlled trials evaluating the efficacy of subgenual cingulate cortex and ventral striatum/ventral capsule DBS were recently discontinued owing to inefficacy based on futility analyses. Overall, the published response rate to DBS therapy, defined as the percentage of patients with > 50 % improvement on the Hamilton Depression Rating Scale, is reported to be 40-70 %, and outcomes were comparable across studies. We conclude that DBS for MDD shows promise, but remains experimental and further accumulation of data is warranted.

Deep brain stimulation of the human reward system for major depression--rationale, outcomes and outlook

Deep brain stimulation (DBS) as a putative approach for treatment-resistant depression (TRD) has now been researched for about a decade. Several uncontrolled studies--all in relatively small patient populations and different target regions-have shown clinically relevant antidepressant effects in about half of the patients and very recently, DBS to a key structure of the reward system, the medial forebrain bundle, has yielded promising results within few days of stimulation and at much lower stimulation intensities. On the downside, DBS procedures in regions are associated with surgical risks (eg, hemorrhage) and psychiatric complications (suicidal attenuation, hypomania) as well as high costs. This overview summarizes research on the mechanisms of brain networks with respect to psychiatric diseases and--as a novelty--extrapolates to the role of the reward system in DBS for patients with treatment-resistant depression. It further evaluates relevant methodological aspects of today's research in DBS for TRD. On the scientific side, the reward system has an important yet clearly under-recognized role in both neurobiology and treatment of depression. On the methodological side of DBS research in TRD, better animal models are clearly needed to explain clinical effects of DBS in TRD. Larger sample sizes, long-term follow-up and designs including blinded sham control are required to draw final conclusions on efficacy and side effects. Practical research issues cover study design, patient tracking, and the discussion of meaningful secondary outcome measures.

Effectiveness and acceptability of deep brain stimulation (DBS) of the subgenual cingulate cortex for treatment-resistant depression: a systematic review and exploratory meta-analysis

BACKGROUND

Deep brain stimulation (DBS) applied to the subgenual cingulate cortex (SCC) has been recently investigated as a potential treatment for severe and chronic treatment-resistant depression (TRD). Given its invasive and experimental nature, a comprehensive evaluation of its effectiveness and acceptability is of paramount importance. Therefore, we conducted the present systematic review and exploratory meta-analysis.

METHODS

We searched the literature for English language prospective clinical trials on DBS of the SCC for TRD from 1999 through December 2012 using MEDLINE, EMBASE, PsycINFO, CENTRAL and SCOPUS, and performed a random effects exploratory meta-analysis using Event Rates and Hedges׳ g effect sizes.

RESULTS

Data from 4 observational studies were included, totaling 66 subjects with severe and chronic TRD. Twelve-month response and remission rates following DBS treatment were 39.9% (95% CI=28.4% to 52.8%) and 26.3% (95% CI=13% to 45.9%), respectively. Also, depression scores at 12 months post-DBS were significantly reduced (i.e., pooled Hedges׳ g effect size=-1.89 [95% CI=-2.64 to -1.15, p<0.0001]). Also, there was a significant decrease in depression scores between 3 and 6 months (Hedges׳ g=-0.27, p=0.003), but no significant changes from months 6 to 12. Finally, dropout rates at 12 months were 10.8% (95% CI=4.3% to 24.4%).

LIMITATIONS

Small number of included studies (most of which were open label), and limited long-term effectiveness data.

CONCLUSIONS

DBS applied to the SCC seems to be associated with relatively large response and remission rates in the short- and medium- to long-term in patients with severe TRD. Also, its maximal antidepressant effects are mostly observed within the first 6 months after device implantation. Nevertheless, these findings are clearly preliminary and future controlled trials should include larger and more representative samples, and focus on the identification of optimal neuroanatomical sites and stimulation parameters.

Computational modeling of an endovascular approach to deep brain stimulation

OBJECTIVE

Deep brain stimulation (DBS) therapy currently relies on a transcranial neurosurgical technique to implant one or more electrode leads into the brain parenchyma. In this study, we used computational modeling to investigate the feasibility of using an endovascular approach to target DBS therapy.

APPROACH

Image-based anatomical reconstructions of the human brain and vasculature were used to identify 17 established and hypothesized anatomical targets of DBS, of which five were found adjacent to a vein or artery with intraluminal diameter ≥1 mm. Two of these targets, the fornix and subgenual cingulate white matter (SgCwm) tracts, were further investigated using a computational modeling framework that combined segmented volumes of the vascularized brain, finite element models of the tissue voltage during DBS, and multi-compartment axon models to predict the direct electrophysiological effects of endovascular DBS.

MAIN RESULTS

The models showed that: (1) a ring-electrode conforming to the vessel wall was more efficient at neural activation than a guidewire design, (2) increasing the length of a ring-electrode had minimal effect on neural activation thresholds, (3) large variability in neural activation occurred with suboptimal placement of a ring-electrode along the targeted vessel, and (4) activation thresholds for the fornix and SgCwm tracts were comparable for endovascular and stereotactic DBS, though endovascular DBS was able to produce significantly larger contralateral activation for a unilateral implantation.

SIGNIFICANCE

Together, these results suggest that endovascular DBS can serve as a complementary approach to stereotactic DBS in select cases.