Deep brain stimulation for treatment-resistant depression

Functional grouping and cortical-subcortical interactions in emotion: a meta-analysis of neuroimaging studies

We performed an updated quantitative meta-analysis of 162 neuroimaging studies of emotion using a novel multi-level kernel-based approach, focusing on locating brain regions consistently activated in emotional tasks and their functional organization into distributed functional groups, independent of semantically defined emotion category labels (e.g., "anger," "fear"). Such brain-based analyses are critical if our ways of labeling emotions are to be evaluated and revised based on consistency with brain data. Consistent activations were limited to specific cortical sub-regions, including multiple functional areas within medial, orbital, and inferior lateral frontal cortices. Consistent with a wealth of animal literature, multiple subcortical activations were identified, including amygdala, ventral striatum, thalamus, hypothalamus, and periaqueductal gray. We used multivariate parcellation and clustering techniques to identify groups of co-activated brain regions across studies. These analyses identified six distributed functional groups, including medial and lateral frontal groups, two posterior cortical groups, and paralimbic and core limbic/brainstem groups. These functional groups provide information on potential organization of brain regions into large-scale networks. Specific follow-up analyses focused on amygdala, periaqueductal gray (PAG), and hypothalamic (Hy) activations, and identified frontal cortical areas co-activated with these core limbic structures. While multiple areas of frontal cortex co-activated with amygdala sub-regions, a specific region of dorsomedial prefrontal cortex (dmPFC, Brodmann's Area 9/32) was the only area co-activated with both PAG and Hy. Subsequent mediation analyses were consistent with a pathway from dmPFC through PAG to Hy. These results suggest that medial frontal areas are more closely associated with core limbic activation than their lateral counterparts, and that dmPFC may play a particularly important role in the cognitive generation of emotional states.

The subgenual anterior cingulate cortex in mood disorders

The anterior cingulate cortex (ACC) ventral to the genu of the corpus callosum has been implicated in the modulation of emotional behavior on the basis of neuroimaging studies in humans and lesion analyses in experimental animals. In a combined positron emission tomography/magnetic resonance imaging study of mood disorders, we demonstrated that the mean gray matter volume of this "subgenual" ACC (sgACC) cortex is abnormally reduced in subjects with major depressive disorder (MDD) and bipolar disorder, irrespective of mood state. Neuropathological assessments of sgACC tissue acquired postmortem from subjects with MDD or bipolar disorder confirmed the decrement in gray matter volume, and revealed that this abnormality was associated with a reduction in glia, with no equivalent loss of neurons. In positron emission tomography studies, the metabolic activity was elevated in this region in the depressed relative to the remitted phases of the same MDD subjects, and effective antidepressant treatment was associated with a reduction in sgACC activity. Other laboratories replicated and extended these findings, and the clinical importance of this treatment effect was underscored by a study showing that deep brain stimulation of the sgACC ameliorates depressive symptoms in treatment-resistant MDD. This article discusses the functional significance of these findings within the context of the preclinical literature that implicates the putative homologue of this region in the regulation of emotional behavior and stress response. In experimental animals, this region participates in an extended "visceromotor network" of structures that modulates autonomic/neuroendocrine responses and neurotransmitter transmission during the neural processing of reward, fear, and stress. These data thus hold important implications for the development of neural models of depression that can account for the abnormal motivational, neuroendocrine, autonomic, and emotional manifestations evident in human mood disorders.

Abnormal anterior cingulum integrity in bipolar disorder determined through diffusion tensor imaging

BACKGROUND

Convergent evidence implicates white matter abnormalities in bipolar disorder. The cingulum is an important candidate structure for study in bipolar disorder as it provides substantial white matter connections within the corticolimbic neural system that subserves emotional regulation involved in the disorder.

AIMS

To test the hypothesis that bipolar disorder is associated with abnormal white matter integrity in the cingulum.

METHOD

Fractional anisotropy in the anterior and posterior cingulum was compared between 42 participants with bipolar disorder and 42 healthy participants using diffusion tensor imaging.

RESULTS

Fractional anisotropy was significantly decreased in the anterior cingulum in the bipolar disorder group compared with the healthy group (P=0.003); however, fractional anisotropy in the posterior cingulum did not differ significantly between groups.

CONCLUSIONS

Our findings demonstrate abnormalities in the structural integrity of the anterior cingulum in bipolar disorder. They extend evidence that supports involvement of the neural system comprising the anterior cingulate cortex and its corticolimbic gray matter connection sites in bipolar disorder to implicate abnormalities in the white matter connections within the system provided by the cingulum.

Overlapping and distinct brain regions associated with the anxiolytic effects of chlordiazepoxide and chronic fluoxetine

Little is known about the sites of action for the behavioral effects of chronic antidepressants. The novelty-induced hypophagia (NIH) test is one of few animal behavioral tests sensitive to acute benzodiazepines and chronic antidepressants. The goals of these experiments were to examine patterns of brain activation associated with the behavioral response to novelty and identify regions that could regulate the anxiolytic effects of acute benzodiazepine and chronic antidepressant treatments, measured using the NIH test. In the first experiment, rats were treated acutely with the anxiolytic, chlordiazepoxide (2.5 or 5 mg/kg, i.p.). In separate experiments, animals were implanted with osmotic minipumps delivering vehicle or fluoxetine (5 or 20 mg/kg per day s.c.) for 3 or 28 days. NIH was assessed by giving animals access to a familiar palatable food in a novel environment. Associated brain areas were identified using c-fos immunohistochemistry. NIH was mitigated by acute chlordiazepoxide and chronic fluoxetine. Both drugs reversed novelty-induced changes in c-fos expression in the lateral division of the posterolateral part of the bed nucleus of the stria terminalis (STLP), cingulate cortex (Cg), and dorsal field CA2 of the hippocampus (dCA2). Chronic fluoxetine additionally increased c-fos expression in the anterior nucleus accumbens (aAcb) and the piriform cortex (Pir). The effects of the drugs on c-fos expression in many regions correlated with anxiolytic efficacy. These findings identified brain regions where the effects of chronic antidepressants and benzodiazepines may converge to produce anxiolytic activity, as well as distinct sites of action for the two classes of drugs.

Mourning and melancholia revisited: correspondences between principles of Freudian metapsychology and empirical findings in neuropsychiatry

Freud began his career as a neurologist studying the anatomy and physiology of the nervous system, but it was his later work in psychology that would secure his place in history. This paper draws attention to consistencies between physiological processes identified by modern clinical research and psychological processes described by Freud, with a special emphasis on his famous paper on depression entitled 'Mourning and melancholia'. Inspired by neuroimaging findings in depression and deep brain stimulation for treatment resistant depression, some preliminary physiological correlates are proposed for a number of key psychoanalytic processes. Specifically, activation of the subgenual cingulate is discussed in relation to repression and the default mode network is discussed in relation to the ego. If these correlates are found to be reliable, this may have implications for the manner in which psychoanalysis is viewed by the wider psychological and psychiatric communities.

Pharmacologic mechanisms of crystal meth

Crystal meth is a form of the stimulant drug methamphetamine that, when smoked, can rapidly achieve high concentrations in the brain. Methamphetamine causes the release of the neurotransmitters dopamine, norepinephrine and serotonin and activates the cardiovascular and central nervous systems. The levels of dopamine are low in the brain of some drug users, but whether this represents neuronal loss is uncertain. The areas of the brain involved in methamphetamine addiction are unknown but probably include the dopamine-rich striatum and regions that interact with the striatum. There is no medication approved for the treatment of relapses of methamphetamine addiction; however, potential therapeutic agents targeted to dopamine and nondopamine (e.g., opioid) systems are in clinical testing.

Electrical stimulation in the lateral hypothalamus in rats in the activity-based anorexia model

Object

One quarter of patients with anorexia nervosa have a poor outcome and continue to suffer chronically or die. Electrical brain stimulation may be of therapeutic benefit in some of these patients; however, the brain target for inducing symptom relief is unknown. In this study, the authors evaluated the effects of acute and chronic electrical stimulation in the lateral hypothalamus on food intake, locomotor activity, and survival time in rats in an activity-based anorexia model.

Methods

In an acute experiment, the authors electrically stimulated at 100 Hz and 0, 25, 50 and 75% of the maximal stimulation amplitude (that is, the amplitude leading to severe side effects) in the lateral hypothalamus on consecutive days during 4 test sessions in 10 rats and evaluated food intake and locomotor activity. In a chronic experiment, they compared food intake, wheel revolutions, and survival time between 6 rats that underwent electrical stimulation in the lateral hypothalamus (50% of maximal stimulation amplitude) and 8 rats that did not undergo stimulation.

Results

In the acute experiment, overall electrical stimulation (25, 50, and 75% combined) and stimulation at 75% of the maximal stimulation amplitude significantly decreased the locomotor activity. However, if the authors omitted results of 1 rat, in which the electrode tip was not located in the lateral hypothalamus on one side but rather in the supraoptic chiasm, the remaining results did not yield significance. No other differences were observed.

Conclusions

When the findings of the current study are extrapolated to patients with anorexia nervosa, the authors do not expect major effects on symptoms with electrical stimulation at high frequency in the lateral hypothalamus.

Evidence of biologic epistasis between BDNF and SLC6A4 and implications for depression

Complex genetic disorders such as depression likely exhibit epistasis, but neural mechanisms of such gene-gene interactions are incompletely understood. 5-HTTLPR and BDNF VAL66MET, functional polymorphisms of the serotonin (5-HT) transporter (SLC6A4) and brain-derived neurotrophic factor (BDNF) gene, impact on two distinct, but interacting signaling systems, which have been related to depression and to the modulation of neurogenesis and plasticity of circuitries of emotion processing. Recent clinical studies suggest that the BDNF MET allele, which shows abnormal intracellular trafficking and regulated secretion, has a protective effect regarding the development of depression and in mice of social defeat stress. Here we show, using anatomical neuroimaging techniques in a sample of healthy subjects (n=111), that the BDNF MET allele, which is predicted to have reduced responsivity to 5-HT signaling, protects against 5-HTTLPR S allele-induced effects on a brain circuitry encompassing the amygdala and the subgenual portion of the anterior cingulate (rAC). Our analyses revealed no effect of the 5-HTTLPR S allele on rAC volume in the presence of BDNF MET alleles, whereas a significant volume reduction (P<0.001) was seen on BDNF VAL/VAL background. Interacting genotype effects were also found in structural connectivity between amygdala and rAC (P=0.002). These data provide in vivo evidence of biologic epistasis between SLC6A4 and BDNF in the human brain by identifying a neural mechanism linking serotonergic and neurotrophic signaling on the neural systems level, and have implications for personalized treatment planning in depression.

Lennart Heimer: concepts of the ventral striatum and extended amygdala

Dr. Lennart Heimer, the famous neuroanatomist of Swedish descent, died last year but left a legacy that will impact the neurosciences and potentially psychosurgery for years to come. He developed an anatomical technique for demonstrating the terminal boutons that helped to delineate basal forebrain anatomy. During these studies, he realized the relationship of basal forebrain structures to the limbic system, thus initiating the concept of the ventral striatum and parallel basal ganglia circuitry.

Heimer excelled as a teacher as well and honed his brain dissection technique to one of the most effective tools for understanding neuroanatomy. His legendary sessions with neurosurgical residents resulted in his recognition as one of the world’s leading fiber tract dissectors. His gentle, engaging manner has been documented in several media formats.

From prefrontal leukotomy to deep brain stimulation: the historical transformation of psychosurgery and the emergence of neuroethics

The history of psychosurgery is described and analyzed. This historical perspective largely begins with analysis of the work of Egas Moniz in the development of the leukotomy, and follows the rise and fall of its popularity in the 1900s. The reemergence of psychosurgical procedures and the development of new therapeutic technologies such as vagus nerve stimulation and deep brain stimulation are discussed. In addition, an introduction to the field of neuroethics is provided, given its importance in any discussion about surgical therapy for psychiatric patients.

Neurostimulation and the minimally conscious state

Neurostimulation to restore cognitive and physical functions is an innovative and promising technique for treating patients with severe brain injury that has resulted in a minimally conscious state (MCS). The technique may involve electrical stimulation of the central thalamus, which has extensive projections to the cerebral cortex. Yet it is unclear whether an improvement in neurological functions would result in a net benefit for these patients. Quality-of-life measurements would be necessary to determine whether any benefit of neurostimulation outweighed any harm in their response to different degrees of cognitive and physical disability. These measures could also indicate whether the technique could be ethically justified and whether surrogates could give proxy consent to its use on brain-injured patients.

Gray matter reduction associated with psychopathology and cognitive dysfunction in unipolar depression: a voxel-based morphometry study

BACKGROUND

Functional neuroimaging studies on both cognitive processing and psychopathology in patients with major depression have reported several functionally aberrant brain areas within limbic-cortical circuits. However, less is known about the relationship between psychopathology, cognitive deficits and regional volume alterations in this patient population.

METHODS

By means of voxel-based morphometry (VBM) and a standardized neuropsychological test battery, we examined 15 patients meeting DSM-IV criteria for major depression disorder and 14 healthy controls in order to investigate the relationship between affective symptoms, cognitive deficits and structural abnormalities.

RESULTS

Patients with depression showed reduced gray matter concentration (GMC) in the left inferior temporal cortex (BA 20), the right orbitofrontal (BA 11) and the dorsolateral prefrontal cortex (BA 46). Reduced gray matter volume (GMV) was found in the left hippocampal gyrus, the cingulate gyrus (BA 24/32) and the thalamus. Structure-cognition correlation analyses revealed that decreased GMC of the right medial and inferior frontal gyrus was associated with both depressive psychopathology and worse executive performance as measured by the Wisconsin Card Sorting Test (WCST). Furthermore, depressive psychopathology and worse performance during the WCST were associated with decreased GMV of the hippocampus. Decreased GMV of the cingulate cortex was associated with worse executive performance.

LIMITATIONS

Moderate illness severity, medication effects, and the relatively small patient sample size should be taken into consideration when reviewing the implications of these results.

CONCLUSIONS

The volumetric results indicate that regional abnormalities in gray matter volume and concentration may be associated with both psychopathological changes and cognitive deficits in depression.

The neurosurgical treatment of addiction

Addiction or substance dependence is a psychiatric disorder that affects many individuals in the general population. Different theories concerning the neurobiological aspects of addiction have been proposed. Special attention has been paid to models concerning dysregulation of the reward circuit and the inhibitory control system within the cortico-basal ganglia-thalamocortical pathways. In the past, attempts have been made to treat patients suffering from addiction by performing psychosurgery. Lesions were created in specific brain regions that were believed to be dysfunctional in addiction. Procedures such as cingulotomy, hypothalamotomy, and resection of the substantia innominata and the nucleus accumbens have been described as a treatment for severe addictive disorders. Deep brain stimulation, a neurosurgical treatment that has been proven to be a safe alternative for lesions in the treatment of movement disorders, has more recently been proposed as treatments for severe psychiatric conditions such as treatment-refractory obsessive-compulsive disorder and depression. With the expanding knowledge of the neurobiology of addiction, deep brain stimulation could be a future option in the treatment arsenal of addiction.

Ablative neurosurgery for mental disorders: is there still a role in the 21st century? A personal perspective

Object

The author presents his personal perspective on ablative neurosurgical techniques used to perform bilateral anterior cingulotomy (BACI) and bilateral anterior capsulotomy (BACA) for ameliorating the symptoms of refractory obsessive-compulsive disorder (OCD) and treatment refractory depression (TRD). With depression predicted to be the second most common cause of disability in the world by the year 2020 and the birth of electric neurostimulation representing an attractive alternative treatment option for TRD and OCD, it is desirable to revisit the pros and cons of these treatment options.

Methods

The author reviewed the surgical methods and outcome (including neuroimaging findings) in all cases in which ablative neurosurgery was performed at Ninewells Hospital and Medical School over the last 2 decades.

Results

The advantages of ablative procedures (BACI and BACA) from patients’ and psychiatrists’ perspectives are that the ablative procedures are one-off procedures that do not require lifelong commitment to program the stimulation devices, fix hardware failures, or change exhausted batteries. From the perspective of healthcare funding bodies, the relatively low cost of these treatments is an advantage. The main disadvantages of BACI and BACA are the perceived higher complication rates, the irreversibility of the surgical lesions, and the stigma associated with brain destruction in psychiatric patients that are still unpalatable in the community at large. However, some patients still choose a one-off procedure in preference to any other options presented to them.

Conclusions

There is still place for BACI and BACA in modern neurosurgery for mental disorders, at least in the short term for those who do not want to commit to lifelong device programming and maintenance.

Induction of c-Fos and DeltaFosB immunoreactivity in rat brain by Vagal nerve stimulation

Vagus nerve stimulation (VNS) is used as therapy for treatment-resistant depression or epilepsy. This study used immunohistochemistry for biomarkers of short-term (c-Fos) and long-term (DeltaFosB) neuronal activation to map regions in brain that are activated by acute (2 h) or chronic (3 weeks) VNS in conscious Sprague-Dawley rats. Electrodes (Cyberonics Inc.) were implanted on the left vagus nerve and 1 week after surgery, stimulation began using parameters employed clinically (one burst of 20 Hz, 250 micros pulse width, 0.25 mA stimulation for 30 s every 5 min). Radio telemetry transmitters were used for monitoring blood pressure, heart rate, activity, and respiratory rate during VNS; neither acute nor chronic VNS significantly affected these parameters. Acute VNS significantly increased c-Fos staining in the nucleus of the solitary tract, paraventricular nucleus of the hypothalamus, parabrachial nucleus, ventral bed nucleus of the stria terminalis, and locus coeruleus but not in the cingulate cortex or dorsal raphe nucleus (DRN). Acute VNS did not affect DeltaFosB staining in any region. Chronic VNS significantly increased DeltaFosB and c-Fos staining bilaterally in each region affected by acute VNS as well as in the cingulate cortex and DRN. Using these stimulation parameters, VNS was tested for antidepressant-like activity using the forced swim test (FST). Both VNS and desipramine significantly decreased immobility in the FST; whereas desipramine decreased immobility by increasing climbing behavior, VNS did so by increasing swimming behavior. This study, then, identified potential sites in brain where VNS may produce its clinical effects.

The anatomy of sorrow: a spiritual, phenomenological, and neurological perspective

There is considerable controversy, both within and outside the field of psychiatry, regarding the boundaries of normal sadness and clinical depression. Furthermore, while there are frequent calls for a "pluralistic", comprehensive approach to understanding depression, few writers have tried to integrate insights from the spiritual, philosophical, and neurobiological literature. The author proposes that such a synthesis is possible, and that our understanding of ordinary sorrow and clinical depression is enriched by drawing from these disparate sources. In particular, a phenomenological analysis of sorrow and depression reveals two overlapping but distinct "lifeworlds". These differ in the relational, temporal, dialectical, and intentional realms. Recent brain imaging studies are also beginning to reveal the neurobiological correlates of sorrow and depression. As we come to understand the neurobiology of these states, we may be able to correlate specific alterations in "neurocircuitry" with their phenomenological expressions.

Neural response to catecholamine depletion in unmedicated subjects with major depressive disorder in remission and healthy subjects

CONTEXT

The pathophysiologic mechanism of major depressive disorder (MDD) has been consistently associated with altered catecholaminergic function, especially with decreased dopamine neurotransmission, by various sources of largely indirect evidence. An instructive paradigm for more directly investigating the relationship between catecholaminergic function and depression has involved the mood response to experimental catecholamine depletion (CD).

OBJECTIVES

To determine whether catecholaminergic dysfunction represents a trait abnormality in MDD and to identify brain circuitry abnormalities involved in the pathophysiologic mechanism of MDD.

DESIGN

Randomized, double-blind, placebo-controlled, crossover, single-site experimental trial.

SETTING

Psychiatric outpatient clinic.

PARTICIPANTS

Fifteen unmedicated subjects with MDD in full remission (hereinafter referred to as RMDD subjects) and 13 healthy controls.

INTERVENTION

Induction of CD by oral administration of alpha-methylparatyrosine. Sham depletion used identical capsules containing hydrous lactose.

MAIN OUTCOME MEASURES

Quantitative positron emission tomography of regional cerebral glucose utilization to study the neural effects of CD and sham depletion. Behavioral assessments included the Montgomery-Asberg Depression Rating Scale and the Snaith-Hamilton Pleasure Scale (anhedonia).

RESULTS

Depressive and anhedonic symptoms increased during CD to a greater extent in RMDD subjects than in controls. In both groups, CD increased metabolism in the anteroventral striatum and decreased metabolism in the orbital gyri. In a limbic-cortical-striatal-pallidal-thalamic network previously implicated in MDD, composed of the ventromedial frontal polar cortex, midcingulate and subgenual anterior cingulate cortex, temporopolar cortex, ventral striatum, and thalamus, metabolism increased in RMDD subjects but decreased or remained unchanged in controls. Metabolic changes induced by CD in the left ventromedial frontal polar cortex correlated positively with depressive symptoms, whereas changes in the anteroventral striatum were correlated with anhedonic symptoms.

CONCLUSIONS

This study provides direct evidence for catecholaminergic dysfunction as a trait abnormality in MDD. It demonstrates that depressive and anhedonic symptoms as a result of decreased catecholaminergic neurotransmission are related to elevated activity within the limbic-cortical-striatal-pallidal-thalamic circuitry.

High-frequency stimulation of the dorsolateral periaqueductal gray and ventromedial hypothalamus fails to inhibit panic-like behaviour

Electrical stimulation of the dorsolateral periaqueductal gray (dlPAG) and one of its target structures, the ventromedial hypothalamus (VMH), produces a typical behaviour in rats consisting of vigorous running and jumping which is known as "escape behaviour". Escape behaviour in rodents closely mimics panic attacks in humans. Since electrical stimulation at higher frequencies generally inhibits the stimulated region, we tested in this study the hypothesis that deep brain stimulation (DBS) of the dlPAG and VMH at higher frequencies (> 100 Hz) would not induce escape behaviour. More specifically, we evaluated whether experimental DBS could be used to inhibit panic-like behaviour. Rats underwent implantation of DBS-electrodes at the level of the dlPAG and VMH and the effects of various stimulation parameters were assessed. In addition, we studied the neural activation pattern resulting from DBS of the dlPAG and VMH using c-Fos immunohistochemistry. We found that stimulation amplitude is the most important stimulation parameter in the induction of escape behaviour. Remarkably, stimulation frequency (1-300 Hz) had no effect on stimulation-induced escape behaviour and therefore it was not possible to prevent the induction of escape behaviour with higher frequencies. The neuronal activation pattern resulting from dlPAG and VMH DBS was similar. These findings suggest that DBS of the dlPAG and VMH induces panic-related behaviours even at higher frequencies.

Evidence-based guidelines for treating depressive disorders with antidepressants: a revision of the 2000 British Association for Psychopharmacology guidelines

A revision of the 2000 British Association for Psychopharmacology evidence-based guidelines for treating depressive disorders with antidepressants was undertaken to incorporate new evidence and to update the recommendations where appropriate. A consensus meeting involving experts in depressive disorders and their management was held in May 2006. Key areas in treating depression were reviewed, and the strength of evidence and clinical implications were considered. The guidelines were drawn up after extensive feedback from participants and interested parties. A literature review is provided, which identifies the quality of evidence to inform the recommendations, the strength of which are based on the level of evidence. These guidelines cover the nature and detection of depressive disorders, acute treatment with antidepressant drugs, choice of drug versus alternative treatment, practical issues in prescribing and management, next-step treatment, relapse prevention, treatment of relapse, and stopping treatment.

Rapid onset of antidepressant action: a new paradigm in the research and treatment of major depressive disorder

OBJECTIVE

Current therapeutics of depression are similar in their time to antidepressant action and often take weeks to months to achieve response and remission, which commonly results in considerable morbidity and disruption in personal, professional, family, and social life, as well as risk for suicidal behavior. Thus, treatment strategies presenting a rapid improvement of depressive symptoms--within hours or even a few days--and whose effects are sustained would have an enormous impact on public health. This article reviews the published data related to different aspects of rapid improvement of depressive symptoms.

DATA SOURCES

Literature for this review was obtained through a search of the MEDLINE database (1966-2007) using the following keywords and phrases: rapid response, antidepressant, time to, glutamate, sleep, therapeutics, latency, and depression. The data obtained were organized according to the following topics: clinical relevance and time course of antidepressant action, interventions showing evidence of rapid response and its potential neurobiological basis, and new technologies for better understanding rapid anti-depressant actions.

DATA SYNTHESIS

A limited number of prospective studies evaluating rapid antidepressant actions have been conducted. Currently, only a few interventions have been shown to produce antidepressant response in hours or a few days. The neurobiological basis of these rapid antidepressant actions is only now being deciphered.

CONCLUSIONS

Certain experimental treatments can produce antidepressant response in a much shorter period of time than existing medications. Understanding the molecular basis of these experimental interventions is likely to lead to the development of improved therapeutics rather than simply furthering our knowledge of current standard antidepressants.

Brain stimulation techniques for the treatment of depression and other psychiatric disorders

OBJECTIVE

The aim of this paper was to review the development of repetitive transcranial magnetic stimulation (rTMS), magnetic seizure therapy (MST), vagal nerve stimulation (VNS), deep brain stimulation (DBS) and other recent brain stimulation techniques for their potential use in the treatment of a range of psychiatric disorders.

CONCLUSIONS

A considerable number of studies have been conducted to investigate the efficacy of rTMS. Although there are considerable problems with this research base, globally the studies suggest that rTMS has antidepressant efficacy. However, more research is required to define the most effective way of applying this technique. There is a much smaller research base supporting the use of VNS and to date the research suggests that only a minority of patients benefit from this procedure. Considerably more research is required in the use of the other techniques which at this stage have been tested only to a very small degree. It is likely that one, and possibly a number, of the new brain stimulation techniques will become available clinically in the psychiatric armamentarium in the coming years. However, considerable research is still required to establish efficacy and define the appropriate place in clinical practice for these treatment approaches.

Disconnection syndromes of basal ganglia, thalamus, and cerebrocerebellar systems

Disconnection syndromes were originally conceptualized as a disruption of communication between different cerebral cortical areas. Two developments mandate a re-evaluation of this notion. First, we present a synopsis of our anatomical studies in monkey elucidating principles of organization of cerebral cortex. Efferent fibers emanate from every cortical area, and are directed with topographic precision via association fibers to ipsilateral cortical areas, commissural fibers to contralateral cerebral regions, striatal fibers to basal ganglia, and projection subcortical bundles to thalamus, brainstem and/or pontocerebellar system. We note that cortical areas can be defined by their patterns of subcortical and cortical connections. Second, we consider motor, cognitive and neuropsychiatric disorders in patients with lesions restricted to basal ganglia, thalamus, or cerebellum, and recognize that these lesions mimic deficits resulting from cortical lesions, with qualitative differences between the manifestations of lesions in functionally related areas of cortical and subcortical nodes. We consider these findings on the basis of anatomical observations from tract tracing studies in monkey, viewing them as disconnection syndromes reflecting loss of the contribution of subcortical nodes to the distributed neural circuits. We introduce a new theoretical framework for the distributed neural circuits, based on general, and specific, principles of anatomical organization, and on the architecture of the nodes that comprise these systems. We propose that neural architecture determines function, i.e., each architectonically distinct cortical and subcortical area contributes a unique transform, or computation, to information processing; anatomically precise and segregated connections between nodes define behavior; and association fiber tracts that link cerebral cortical areas with each other enable the cross-modal integration required for evolved complex behaviors. This model enables the formulation and testing of future hypotheses in investigations using evolving magnetic resonance imaging techniques in humans, and in clinical studies in patients with cortical and subcortical lesions.

The neural basis of human social values: evidence from functional MRI

Social values are composed of social concepts (e.g., "generosity") and context-dependent moral sentiments (e.g., "pride"). The neural basis of this intricate cognitive architecture has not been investigated thus far. Here, we used functional magnetic resonance imaging while subjects imagined their own actions toward another person (self-agency) which either conformed or were counter to a social value and were associated with pride or guilt, respectively. Imagined actions of another person toward the subjects (other-agency) in accordance with or counter to a value were associated with gratitude or indignation/anger. As hypothesized, superior anterior temporal lobe (aTL) activity increased with conceptual detail in all conditions. During self-agency, activity in the anterior ventromedial prefrontal cortex correlated with pride and guilt, whereas activity in the subgenual cingulate solely correlated with guilt. In contrast, indignation/anger activated lateral orbitofrontal-insular cortices. Pride and gratitude additionally evoked mesolimbic and basal forebrain activations. Our results demonstrate that social values emerge from coactivation of stable abstract social conceptual representations in the superior aTL and context-dependent moral sentiments encoded in fronto-mesolimbic regions. This neural architecture may provide the basis of our ability to communicate about the meaning of social values across cultural contexts without limiting our flexibility to adapt their emotional interpretation.

Chronic vagus nerve stimulation for treatment-resistant depression decreases resting ventromedial prefrontal glucose metabolism

Vagus nerve stimulation (VNS) is used as an adjunctive therapy for treatment-resistant depression (TRD). Its mechanism of action is not fully understood. Longitudinal measurement of changes in brain metabolism associated with VNS can provide insights into this new treatment modality. Eight severely depressed outpatients who were highly treatment-resistant underwent electrical stimulation of the left vagus nerve for approximately one year. The main outcome measures were resting regional brain glucose uptake measured with positron emission tomography (PET) and the 24-item Hamilton Depression Scale. The most significant and extensive change over one year of chronic VNS localized to the ventromedial prefrontal cortex extending from the subgenual cingulate to the frontal pole. This region continued to decline in metabolism even toward the end of the study. Clinically, this cohort showed a trend for improvement. No correlations surfaced between change in glucose uptake and depression scores. However, the sample size was small; none remitted; and the range of depression scores was limited. Chronic VNS as adjunctive therapy in patients with severe TRD produces protracted and robust declines in resting brain activity within the ventromedial prefrontal cortex, a network with dense connectivity to the amygdala and structures monitoring the internal milieu.

[Neuromodulation for Parkinson's disease]

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a progressive loss of midbrain dopaminergic (DA) neurons and a subsequent reduction in striatal dopamine. As a treatment for advanced Parkinson's disease, deep brain stimulation (DBS) of the thalamus was introduced in 1987 to treat tremor, and was applied in 1993 to the subthalamic nucleus. Now high-frequency stimulation of the subthalamic nucleus has become a surgical therapy of choice. Another surgical treatment is a cell replacement therapy. Transplantation of fetal dopaminergic (DA) neurons can produce symptomatic relief, however, the technical and ethical difficulties in obtaining sufficient and appropriate donor fetal brain tissue have limited the application of this therapy. Then, neural precursor cells and embryonic stem (ES) cells are expected to be candidates of potential donor cells for transplantation. We induced DA neurons from monkey ES cells, and analyzed the effect of transplantation of the DA neurons into MPTP-treated monkeys as a primate model of Parkinson's disease. Behavioral studies and functional imaging revealed that the transplanted cells functioned as DA neurons, attenuating the MPTP-induced neurological symptoms. DA neurons have also been generated from several human ES cell lines. Furthermore, functional recovery of rat PD models after transplantation was observed. One of the major problems in ES cell transplantation is tumor formation, which is caused by a small fraction of undifferentiated ES cells in the graft. So, it is essential for undifferentiated ES cells to be eliminated from the graft in order for transplantation to be feasible. These efforts will lead to clinical application of ES cell transplantation to the patients with PD.

Tracking the mechanisms of deep brain stimulation for neuropsychiatric disorders

Deep brain stimulation (DBS) has recently emerged as a potential treatment for medically intractable neuropsychiatric disorders. Pilot clinical studies with encouraging results have been performed with DBS of the ventral anterior internal capsule (VAIC) and subgenual cingulate white matter (Cg25WM) for the treatment of obsessive-compulsive disorder and depression. However, little is known about the underlying response of individual neurons, or the networks they are connected to, when DBS is applied to the VAIC or Cg25WM. This review summarizes current understanding of the response of axons to DBS, and discusses the general brain network architectures thought to underlie neuropsychiatric disorders. We also employ diffusion tensor imaging tractography to better understand the axonal trajectories surrounding DBS electrodes implanted in the VAIC or Cg25WM. Finally, we attempt to reconcile various data sets by presenting generalized hypotheses on potential therapeutic mechanisms of DBS for neuropsychiatric disease.

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

The purpose of this study was to evaluate preservation of cognitive function after deep brain stimulation (DBS) of the subgenual cingulate (Cg25) for treatment-resistant depression (TRD). We have previously reported on the treatment methods, safety, and 6-month clinical outcome (Mayberg et al., Neuron. 2005;45:651-660). Comprehensive neuropsychological assessments tapping 4 domains of frontal lobe function, and general cognitive abilities, were completed before implantation and at 3, 6, and 12 months postonset of continuous DBS in 6 TRD patients. No adverse neuropsychological effects were noted following surgery, onset and maintenance of DBS with the exception of transient motor slowing noted at 3 and 6 months that improved to normative levels by 12 months. Several areas of cognition that were below average or impaired at baseline improved over follow-up, and these changes were not correlated with improvements in mood. Though the sample size is small, these results support cognitive safety of Cg25 DBS for TRD.

Applicants for stereotactic neurosurgery for psychiatric disorders: role of the Flemish advisory board

OBJECTIVE

Research on stereotactic neurosurgery for psychiatric disorders (SNPD) is rapidly evolving. Knowledge on patients undergoing SNPD is of crucial importance. We describe applicants for SNPD and examine the necessity for a multidisciplinary advisory board.

METHOD

Summary of the current practice of the Flemish advisory board (SNPD committee) and analysis of a questionnaire investigating the attitude of clinicians on SNPD.

RESULTS

In 7 years, 91 applications were submitted, nine patients did not fulfill diagnostic criteria for OCD, 65 patients received a positive recommendation, 50 SNPD procedures were performed. The prevalence of SNPD in the current year in Belgium is 0.6/million inhabitants. Ninety-seven per cent of clinicians consider the expertise and advice of the SNPD committee essential for indication setting. Forty-four percent of clinicians consider referral of a patient for capsulotomy, 82% for electrical brain stimulation.

CONCLUSION

Neurosurgery is exclusively considered for severe, treatment-refractory psychiatric disorders. Clinicians consider the SNPD committee essential in the decision-making process prior to intervention.

[Somatic therapies for treatment-resistant psychiatric disorders]

OBJECTIVE

This paper reviews the current knowledge of somatic treatment in psychiatry, with a focus on treatment-resistant psychiatric disorders.

METHOD

A computerized search of the literature was conducted on Medline using the words "electroconvulsive therapy", "transcranial magnetic stimulation", "vagus nerve stimulation", "deep brain stimulation" and "magnetic seizure therapy". References from each paper were also screened.

RESULTS

The development of new non-pharmacological psychiatric interventions in the past decades has renewed the clinical and research interest in somatic therapies. Although electroconvulsive therapy remains the only somatic treatment with undisputed efficacy, transcranial magnetic stimulation, magnetic seizure therapy, vagus nerve stimulation and deep brain stimulation all offer potential as novel means of psychiatric treatment.

CONCLUSIONS

New treatment modalities still have an insufficient body of data. Notwithstanding, biological strategies continue to hold promise as a safer and more effective approach to psychiatric treatment.

Functional connectivity of human striatum: a resting state FMRI study

Classically regarded as motor structures, the basal ganglia subserve a wide range of functions, including motor, cognitive, motivational, and emotional processes. Consistent with this broad-reaching involvement in brain function, basal ganglia dysfunction has been implicated in numerous neurological and psychiatric disorders. Despite recent advances in human neuroimaging, models of basal ganglia circuitry continue to rely primarily upon inference from animal studies. Here, we provide a comprehensive functional connectivity analysis of basal ganglia circuitry in humans through a functional magnetic resonance imaging examination during rest. Voxelwise regression analyses substantiated the hypothesized motor, cognitive, and affective divisions among striatal subregions, and provided in vivo evidence of a functional organization consistent with parallel and integrative loop models described in animals. Our findings also revealed subtler distinctions within striatal subregions not previously appreciated by task-based imaging approaches. For instance, the inferior ventral striatum is functionally connected with medial portions of orbitofrontal cortex, whereas a more superior ventral striatal seed is associated with medial and lateral portions. The ability to map multiple distinct striatal circuits in a single study in humans, as opposed to relying on meta-analyses of multiple studies, is a principal strength of resting state functional magnetic resonance imaging. This approach holds promise for studying basal ganglia dysfunction in clinical disorders.

The changes of AgNOR parameters of anterior cingulate pyramidal neurons are region-specific in suicidal and non-suicidal depressive patients

The anterior cingulate cortex (AC) is consistently implicated in the pathophysiology of depression. While suicide has been shown in previous reports to be closely related to depression, it is still a distinct phenomenon. The aim to differentiate between depression and suicide was approached by the karyometric analysis of AC pyramidal neurons. The study was performed on paraffin-embedded brains from 20 depressive patients (10 of whom had committed suicide) and 24 matched controls. The karyometric parameters of the layer III and V pyramidal neurons of the dorsal and ventral AC were evaluated bilaterally by Argyrophilic Nucleolar Organiser (AgNOR) silver staining method. Control-specific was the increased nuclear area in ontogenetically younger pyramidal neurons layer III in the left dorsal compared with ventral AC (Wilcoxon test, P<0.01). The decreased AgNOR number per nucleus in these cells in the right ventral AC was depression-specific compared with controls (t-test, P=0.047). On the other hand, the diffuse decrease in AgNOR ratio throughout pyramidal neurons on the left side was specific for suicidal depressive patients compared with non-suicidal patients and controls (ANOVA, P=0.028). The results suggest that regionally differentiated depression- and suicide-specific disturbed function of the most important AC output cells exists in depressive patients.

Neuroimaging and Depression

Major depression is among the most debilitating, prevalent, and recurrent of all psychiatric disorders. Over the past decade, investigators have examined the neural mechanisms associated with this disorder. In this article we present an overview of neuroimaging research that has assessed the structure and functioning of the amygdala, subgenual anterior cingulate cortex, and dorsolateral prefrontal cortex in major depression. We then describe results of studies that have attempted to elucidate the nature of the relations among these brain structures. The picture that emerges from these investigations is one in which heightened activity in limbic structures that underlie the experience and expression of emotion dampens activation in dorsal cortical structures that are involved in affect regulation, reducing their ability to influence limbic activation. We conclude by highlighting unresolved issues concerning the roles of these structures in depression and their relation to specific symptoms of this disorder.

Major depression, 5HTTLPR genotype, suicide and antidepressant influences on thalamic volume

BACKGROUND

The 5HTTLPR genetic variant of the serotonin transporter gene (SERT or 5-HTT), which is comprised of a short (SERT-s) and a long (SERT-l) allele, is associated with major depressive disorder and post-traumatic brain disorder.

AIMS

The present study sought to determine whether the total thalamus and major subregions are altered in size in major depressive disorder and in relation to the 5HTTLPR genotype.

METHOD

We investigated the influence of 5HTTLPR genotype, psychiatric diagnosis, suicide and other clinical factors on the volume of the entire post-mortem thalamus.

RESULTS

Major depressive disorder, SERT-ss genotype and suicide emerged as independent factors contributing to an enlargement of the total thalamus. The majority of the volume enlargement associated with the SERT-ss genotype occurred in the pulvinar, whereas enlargement associated with major depressive disorder occurred in the limbic nuclei and in other regions of the thalamus. A history of antidepressant treatment was associated with reduced thalamic volume.

CONCLUSIONS

The 5HTTLPR genetic variation may affect behaviour and psychiatric conditions, in part, by altering the anatomy of the thalamus.

Neural responses to monetary incentives in major depression

BACKGROUND

Reduced responsiveness to positive incentives is a central feature of Major Depressive Disorder (MDD). In the present study, we compared neural correlates of monetary incentive processing in unmedicated depressed participants and never-depressed control subjects.

METHODS

Fourteen currently depressed and 12 never-depressed participants underwent functional magnetic resonance imaging while participating in a monetary incentive delay task. During the task, participants were cued to anticipate and respond to a rapidly presented target to gain or avoid losing varying amounts of money.

RESULTS

Depressed and never-depressed participants did not differ in nucleus accumbens (NAcc) activation or in affective or behavioral responses during gain anticipation. Depressed participants did, however, exhibit increasing anterior cingulate activation during anticipation of increasing gains, whereas never-depressed participants showed increasing anterior cingulate activation during anticipation of increasing loss. Depressed participants also showed reduced discrimination of gain versus nongain outcomes.

CONCLUSIONS

The present findings indicate that although unmedicated depressed individuals have the capacity to experience positive arousal and recruit NAcc activation during gain anticipation, they also exhibit increased anterior cingulate cortex activation, suggestive of increased conflict during anticipation of gains, in addition to showing reduced discrimination of gain versus nongain outcomes.

Colour vision: cortical circuitry for appearance

Directly stimulating certain cortical neurons can produce a color sensation; a case is reported in which the color perceived by stimulation is the same as the color that most effectively excites the cortical circuitry.

Complementary circuits connecting the orbital and medial prefrontal networks with the temporal, insular, and opercular cortex in the macaque monkey

The origin and termination of axonal connections between the orbital and medial prefrontal cortex (OMPFC) and the temporal, insular, and opercular cortex have been analyzed with anterograde and retrograde axonal tracers, injected in the OMPFC or temporal cortex. The results show that there are two distinct, complementary, and reciprocal neural systems, related to the previously defined "orbital" and "medial" prefrontal networks. The orbital prefrontal network, which includes areas in the central and lateral part of the orbital cortex, is connected with vision-related areas in the inferior temporal cortex (especially area TEav) and the fundus and ventral bank of the superior temporal sulcus (STSf/v), and with somatic sensory-related areas in the frontal operculum (OPf) and dysgranular insular area (Id). No connections were found between the orbital network and auditory areas. The orbital network is also connected with taste and olfactory cortical areas and the perirhinal cortex and appears to be involved in assessment of sensory objects, especially food. The medial prefrontal network includes areas on the medial surface of the frontal lobe, medial orbital areas, and two caudolateral orbital areas. It is connected with the rostral superior temporal gyrus (STGr) and the dorsal bank of the superior temporal sulcus (STSd). This region is rostral to the auditory parabelt areas, and there are only relatively light connections between the auditory areas and the medial network. This system, which is also connected with the entorhinal, parahippocampal, and cingulate/retrosplenial cortex, may be involved in emotion and other self-referential processes.

Memory enhancement induced by hypothalamic/fornix deep brain stimulation

Bilateral hypothalamic deep brain stimulation was performed to treat a patient with morbid obesity. We observed, quite unexpectedly, that stimulation evoked detailed autobiographical memories. Associative memory tasks conducted in a double-blinded "on" versus "off" manner demonstrated that stimulation increased recollection but not familiarity-based recognition, indicating a functional engagement of the hippocampus. Electroencephalographic source localization showed that hypothalamic deep brain stimulation drove activity in mesial temporal lobe structures. This shows that hypothalamic stimulation in this patient modulates limbic activity and improves certain memory functions.

A randomized, double-blind clinical trial on the efficacy of cortical direct current stimulation for the treatment of major depression

Preliminary findings suggest that transcranial direct current stimulation (tDCS) can have antidepressant effects. We sought to test this further in a parallel-group, double-blind clinical trial with 40 patients with major depression, medication-free randomized into three groups of treatment: anodal tDCS of the left dorsolateral prefrontal cortex (active group - 'DLPFC'); anodal tDCS of the occipital cortex (active control group - 'occipital') and sham tDCS (placebo control group - 'sham'). tDCS was applied for 10 sessions during a 2-wk period. Mood was evaluated by a blinded rater using the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). The treatment was well tolerated with minimal side-effects that were distributed equally across all treatment groups. We found significantly larger reductions in depression scores after DLPFC tDCS [HDRS reduction of 40.4% (+/-25.8%)] compared to occipital [HDRS reduction of 21.3% (+/-12.9%)] and sham tDCS [HDRS reduction of 10.4% (+/-36.6%)]. The beneficial effects of tDCS in the DLPFC group persisted for 1 month after the end of treatment. Our findings support further investigation on the effects of this novel potential therapeutic approach - tDCS - for the treatment of major depression.