Effects of electrical stimulation or lesion in nucleus accumbens on the behaviour of rats in a T-maze after administration of 8-OH-DPAT or vehicle

Role of deep brain stimulation in management of psychiatric disorders

Nowadays, most of patients affected by psychiatric disorders are successfully treated with conservative therapies. Still, a variable percentage of them demonstrate resistance to conventional treatments, and alternative methods can then be considered. During the last 20 years, there is a progressive interest in use of deep brain stimulation (DBS) in mental illnesses. It has become clear nowadays, that this modality may be effectively applied under specific indications in some patients with major depressive disorder, obsessive-compulsive disorder, anorexia nervosa and other eating disorders, Tourette syndrome, schizophrenia, substance use disorder, and even pathologically aggressive behavior. Despite the fact that the efficacy of neuromodulation with DBS, as well as of various lesional interventions, in cases of mental illnesses is still not fully established, there are several premises for wider applications of such "unclassical" psychiatric treatments in the future. Novel technologies of DBS, developments in non-invasive lesioning using stereotactic radiosurgery and transcranial magnetic resonance-guided focused ultrasound, and advances of neurophysiological and neuroimaging modalities may bolster further clinical applications of psychiatric neurosurgery, improve its results, and allow for individually selected treatment strategies tailored to specific needs of the patient.

Bidirectional Behavioral Selection in Mice: A Novel Pre-clinical Approach to Examining Compulsivity

Obsessive-compulsive disorder (OCD) and related disorders (OCRD) is one of the most prevalent neuropsychiatric disorders with no definitive etiology. The pathophysiological attributes of OCD are driven by a multitude of factors that involve polygenic mechanisms, gender, neurochemistry, physiological status, environmental exposures and complex interactions among these factors. Such complex intertwining of contributing factors imparts clinical heterogeneity to the disorder making it challenging for therapeutic intervention. Mouse strains selected for excessive levels of nest- building behavior exhibit a spontaneous, stable and predictable compulsive-like behavioral phenotype. These compulsive-like mice exhibit heterogeneity in expression of compulsive-like and other adjunct behaviors that might serve as a valuable animal equivalent for examining the interactions of genetics, sex and environmental factors in influencing the pathophysiology of OCD. The current review summarizes the existing findings on the compulsive-like mice that bolster their face, construct and predictive validity for studying various dimensions of compulsive and associated behaviors often reported in clinical OCD and OCRD.

Invasive and Non-invasive Neurostimulation for OCD

It becomes increasingly clear that (non-)invasive neurostimulation is an effective treatment for obsessive-compulsive disorder (OCD). In this chapter we review the available evidence on techniques and targets, clinical results including a meta-analysis, mechanisms of action, and animal research. We focus on deep brain stimulation (DBS), but also cover non-invasive neurostimulation including transcranial magnetic stimulation (TMS). Data shows that most DBS studies target the ventral capsule/ventral striatum (VC/VS), with an overall 76% response rate in treatment-refractory OCD. Also TMS holds clinical promise. Increased insight in the normalizing effects of neurostimulation on cortico-striatal-thalamic-cortical (CSTC) loops - through neuroimaging and animal research - provides novel opportunities to further optimize treatment strategies. Advancing clinical implementation of neurostimulation techniques is essential to ameliorate the lives of the many treatment-refractory OCD patients.

Animal Models and Animal Experimentation in the Development of Deep Brain Stimulation: From a Specific Controversy to a Multidimensional Debate

In this article, we explore a specific controversy about animal experimentation and animal models in the recent history of deep brain stimulation (DBS), and we question its ramifications. DBS development intertwines clinical practice with fundamental research and stands at the crossroads of multiple legacies. We take up the various issues and controversies embedded in this rarely addressed dispute, from a standpoint that combines socio-anthropological and legal aspects. Our starting point is a debate on the role of animal experimentation in the development of DBS between Jarrod Bailey, a researcher promoting the abolition of animal experimentation, and Alim Louis Benabid, Marwan Hariz, and Mahlon DeLong, three key figures in the area of DBS and neuroscience. By clarifying the positions of the different protagonists and retracing the issues raised in these discussions, our objective is to show how this specific debate has extended from its initial space and how it provides an object of study with heuristic scope. We first present this partially polemic discussion about the history of DBS, and its link with a more general debate on the validity and use of animal models and the need for animal experiments. Then, we raise the issue of the relations and interactions between experiments on animals and on humans in the logics of biomedical innovation. The third step is to situate the discussion within the wider framework of opposition towards animal experimentation and the promotion of animal' rights. Finally, combining these interweaved issues, possible implications emerge regarding the future of DBS. We show that behind these several controversies lie the question of translational research and the model of medicine upheld by DBS. We describe how the technology contributes to blurring the lines between research (fundamental, preclinical and clinical research) and care, as well as between humans and animals as substrates and objects of knowledge. The dynamics of DBS future development might then become a point of convergence for neuroscientists and animal rights defenders' interests.

Image-based in vivo assessment of targeting accuracy of stereotactic brain surgery in experimental rodent models

Stereotactic neurosurgery is used in pre-clinical research of neurological and psychiatric disorders in experimental rat and mouse models to engraft a needle or electrode at a pre-defined location in the brain. However, inaccurate targeting may confound the results of such experiments. In contrast to the clinical practice, inaccurate targeting in rodents remains usually unnoticed until assessed by ex vivo end-point histology. We here propose a workflow for in vivo assessment of stereotactic targeting accuracy in small animal studies based on multi-modal post-operative imaging. The surgical trajectory in each individual animal is reconstructed in 3D from the physical implant imaged in post-operative CT and/or its trace as visible in post-operative MRI. By co-registering post-operative images of individual animals to a common stereotaxic template, targeting accuracy is quantified. Two commonly used neuromodulation regions were used as targets. Target localization errors showed not only variability, but also inaccuracy in targeting. Only about 30% of electrodes were within the subnucleus structure that was targeted and a-specific adverse effects were also noted. Shifting from invasive/subjective 2D histology towards objective in vivo 3D imaging-based assessment of targeting accuracy may benefit a more effective use of the experimental data by excluding off-target cases early in the study.

Obesity and deep brain stimulation: an overview

Deep brain stimulation (DBS) has been employed to treat a variety of disorders such as Parkinson disease, dystonia, and essential tremor. Newer indications such as epilepsy and obsessive-compulsive disorder have been added to the armamentarium. In this review, we present an initial summary of current methods in the management of obesity and then explore efforts in neuromodulation and DBS as a novel modality in the treatment of obesity disorders.

Performance of compulsive behavior in rats is not a unitary phenomenon - validation of separate functional components in compulsive checking behavior

A previous analysis of the quinpirole sensitisation rat model of obsessive-compulsive disorder revealed that the behavioral phenotype of compulsive checking consists of three constitutive components – vigor of checking performance, focus on the task of checking, and satiety following a bout of checking. As confirmation of this analysis, the aim of the present study was to reconstitute, without quinpirole treatment, each of the putative components, with the expectation that these would self-assemble into compulsive checking. To reconstitute vigor and satiety, the employed treatment was a bilateral lesion of the nucleus accumbens core (NAc), as this treatment was shown previously to exaggerate these components. To reconstitute focus, the employed treatment was a low dose of the serotonin-1A receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin hydrochloride (DPAT) (0.0625 mg/kg), as high doses of this drug induce compulsive behavior and exacerbate focus. Results showed that injection of DPAT to NAc lesion rats did yield compulsive checking. Neither the drug alone nor the NAc lesion by itself produced compulsive checking. The demonstrated synthesis of compulsive checking by the combined treatment of low-dose DPAT and NAc lesion strengthened the previous fractionation of the model obsessive-compulsive disorder phenotype into three constitutive components, and suggested a role for serotonin-1A receptors outside the NAc in enhanced focus on the task of checking.

Nucleus accumbens high-frequency stimulation selectively impacts nigrostriatal dopaminergic neurons

High-frequency stimulation of the nucleus accumbens, also known as deep brain stimulation (DBS), is currently used to alleviate obsessive compulsive symptoms when pharmacotherapy is ineffective. However, the mechanism by which DBS achieves its therapeutic actions is not understood. Imaging studies and the actions of dopaminergic drugs in untreated patients suggest that the dopamine (DA) system likely plays a role in the pathophysiology of obsessive compulsive disorder. Therefore, we examined whether DBS would impact the DA system as a potential component of its therapeutic actions. The activity of DA neurons in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) were recorded in anesthetized rats under high-frequency stimulation. DA neuron activity was measured in terms of number of neurons firing, average firing rate and firing pattern. DBS of the nucleus accumbens core did not significantly affect VTA activity or discharge pattern. On the other hand, DBS caused a potent decrease in the number of SNc DA neurons firing spontaneously. Such an effect could contribute to the disruption of pathological habit formation in the SNc-dorsal striatal projection system that may have therapeutic implications for the treatment of obsessive compulsive disorder.

Mapping brain regions in which deep brain stimulation affects schizophrenia-like behavior in two rat models of schizophrenia

BACKGROUND AND OBJECTIVES

The development of more efficient treatment remains a major unmet need in the realm of schizophrenia disease. Using the maternal immune stimulation and the pubertal cannabinoid administration rat model of schizophrenia, the present study aimed at testing the hypothesis that deep brain stimulation (DBS) serves as a novel therapeutic technique for this disorder.

METHODS

Adult offspring of dams, treated with the immune activating agent poly I:C (4 mg/kg, n = 50) or saline (n = 50), underwent bilateral stereotactic electrode implantation into one of the following brain regions: subthalamic nucleus (STN, n = 12/10), entopeduncularis nucleus (EP, n = 10/11), globus pallidus (GP, n = 10/10), medial prefrontal cortex (mPFC, n = 8/8), or dorsomedial thalamus (DM, n = 10/11). Adult rats treated with the CB1 receptor agonist WIN 55,212-2 (WIN, n = 16) or saline (n = 12) during puberty were bilaterally implanted with electrodes into either the mPFC (n = 8/6) or the DM (n = 8/6). After a post-operative recovery period of one week, all rats were tested on a well-established cross-species phenomenon that is disrupted in schizophrenia, the pre-pulse inhibition (PPI) of the acoustic startle reflex (ASR) under different DBS conditions.

RESULTS

Poly I:C induced deficits in PPI of the ASR were normalized upon DBS. DBS effects depended on both stimulation target and stimulation parameters. Most prominent effects were found under DBS at high frequencies in the mPFC and DM. These effects were replicated in the pubertal WIN administration rat model of schizophrenia.

CONCLUSIONS

Brain regions, in which DBS normalized PPI deficits, might be of therapeutic relevance to the treatment of schizophrenia. Results imply that DBS could be considered a plausible therapeutic technique in the realm of schizophrenia disease.

Long-term high frequency deep brain stimulation of the nucleus accumbens drives time-dependent changes in functional connectivity in the rodent limbic system

Deep brain stimulation of the ventral striatum is an effective treatment for a variety of treatment refractory psychiatric disorders yet the mechanism of action remains elusive. We examined how five days of stimulation affected rhythmic brain activity in freely moving rats in terms of oscillatory power within, and coherence between, selected limbic regions bilaterally. Custom made bipolar stimulating/recording electrodes were implanted, bilaterally, in the nucleus accumbens core. Local field potential (LFP) recording electrodes were implanted, bilaterally in the prelimbic and orbitofrontal cortices and mediodorsal thalamic nucleus. Stimulation was delivered bilaterally with 100 μs duration constant current pulses at a frequency of 130 Hz delivered at an amplitude of 100 μA using a custom-made stimulation device. Synchronized video and LFP data were collected from animals in their home cages before, during and after stimulation. Signals were processed to remove movement and stimulation artifacts, and analyzed to determine changes in spectral power within, and coherence between regions. Five days stimulation of the nucleus accumbens core yielded temporally dynamic modulation of LFP power in multiple bandwidths across multiple brain regions. Coherence was seen to decrease in the alpha band between the mediodorsal thalamic nucleus and core of the nucleus accumbens. Coherence between each core of the nucleus accumbens bilaterally showed rich temporal dynamics throughout the five day stimulation period. Stimulation cessation revealed significant "rebound" effects in both power and coherence in multiple brain regions. Overall, the initial changes in power observed with short-term stimulation are replaced by altered coherence, which may reflect the functional action of DBS.

Electrical stimulation of the inferior thalamic peduncle in the treatment of major depression and obsessive compulsive disorders

OBJECTIVE

Stimulation of the inferior thalamic peduncle (ITP) is emerging as a promising new therapeutic target in certain psychiatric disorders. The circuitry that includes the nonspecific thalamic system (NSTS), which projects via the ITP to the orbitofrontal cortex (OFC), is involved in the physiopathology of major depression disorder (MDD) and obsessive compulsive disorder (OCD). The safety and efficacy of chronic ITP stimulation in cases of MDD and OCD refractory to medical treatment is presented.

MATERIALS AND METHODS

Six patients with OCD and one with MDD were implanted with tetrapolar deep brain stimulation electrodes in the ITP (x = 3.5 mm lateral to the ventricular wall, y = 5 mm behind the anterior commissure, and z = at the intercommissural plane, i.e., anterior commissure-posterior commissure [AC-PC] level). The effect of chronic stimulation at 130 Hz, 450 μs, and 5.0 V on OCD was evaluated before and 3, 6, and 12 months after initiation of electrical stimulation through the Yale-Brown Obsessive Compulsive Scale, Hamilton Depression Rating Scale, and Global Assessment of Function scale.

RESULTS

Chronic ITP electrical stimulation in OCD patients decreased the mean Yale-Brown Obsessive Compulsive Scale score to around 51% for the group at the 12-month follow-up, and increased the mean Global Assessment of Function scale score to 68% for a significant improvement (P = 0.026). Three of 6 patients returned to work. The Hamilton Depression Rating Scale score of the only patient with MDD treated to date went from 42 to 6. This condition of the patient, who had been incapacitated for 5 years prior to surgery, has not relapsed for 9 years. Three OCD patients with drug addiction continued to consume drugs in spite of their improvement in OCD.

CONCLUSION

Deep brain stimulation in the ITP is safe and may be effective in the treatment of OCD. A multicenter evaluation of the safety and efficacy of ITP in OCD is currently in process.

Mechanisms of deep brain stimulation for obsessive compulsive disorder: effects upon cells and circuits

Deep brain stimulation (DBS) has emerged as a safe, effective, and reversible treatment for a number of movement disorders. This has prompted investigation of its use for other applications including psychiatric disorders. In recent years, DBS has been introduced for the treatment of obsessive compulsive disorder (OCD), which is characterized by recurrent unwanted thoughts or ideas (obsessions) and repetitive behaviors or mental acts performed in order to relieve these obsessions (compulsions). Abnormal activity in cortico-striato-thalamo-cortical (CSTC) circuits including the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), ventral striatum, and mediodorsal (MD) thalamus has been implicated in OCD. To this end a number of DBS targets including the anterior limb of the internal capsule (ALIC), ventral capsule/ventral striatum (VC/VS), ventral caudate nucleus, subthalamic nucleus (STN), and nucleus accumbens (NAc) have been investigated for the treatment of OCD. Despite its efficacy and widespread use in movement disorders, the mechanism of DBS is not fully understood, especially as it relates to psychiatric disorders. While initially thought to create a functional lesion akin to ablative procedures, it is increasingly clear that DBS may induce clinical benefit through activation of axonal fibers spanning the CSTC circuits, alteration of oscillatory activity within this network, and/or release of critical neurotransmitters. In this article we review how the use of DBS for OCD informs our understanding of both the mechanisms of DBS and the circuitry of OCD. We review the literature on DBS for OCD and discuss potential mechanisms of action at the neuronal level as well as the broader circuit level.

Neuromodulation in psychiatric disorders

Psychiatric disorders are worldwide a common cause of severe and long-term disability and socioeconomic burden. The management of patients with psychiatric disorders consists of drug therapy and/or psychotherapy. However, in some patients, these treatment modalities do not produce sufficient therapeutic effects or induce intolerable side effects. For these patients, neuromodulation has been suggested as a potential treatment modality. Neuromodulation includes deep brain stimulation, vagal nerve stimulation, and transcranial magnetic and electrical stimulation. The rationale for neuromodulation is derived from the research identifying neurobiologically localized substrates for refractory psychiatric symptoms. Here, we review the clinical data on neuromodulation in the major psychiatric disorders. Relevant data from animal models will also be discussed to explain the neurobiological basis of the therapy.

Unilateral deep brain stimulation in the nucleus accumbens core does not affect local monoamine release

Recent publications have shown promising results of deep brain stimulation (DBS) in the nucleus accumbens for patients with obsessive compulsive disorder and major depressive disorder. Despite its increasing application in the clinical setting, the neurobiological mechanism of action of DBS is still uncertain. One of the possible effects of DBS might be phasic or tonic changes in monoamine release either locally in the target area or in a distant, connected region. In the present study we investigate whether unilateral DBS of the Nucleus Accumbens Core (NAc core) has a local effect on in vivo monoamine release. Freely moving animals were unilaterally stimulated with 300 μA or 400 μA (120 Hz, pulse width 80 μs) in the NAc core for 5 h. 1h before and during stimulation we measured dopamine, serotonin, their metabolites and noradrenaline using in vivo microdialysis. We found no significant effect of stimulation on extracellular concentrations of monoaminergic neurotransmitters or their metabolites in the NAc core during stimulation. Our results suggest that the rapid effects of DBS in the NAc are not a result of changes in local monoamine release in the NAc core. For future directions it is interesting to note that several microdialysis and electrophysiology studies have shown effects of DBS in areas distant from the stimulation target.

Deep brain stimulation for obsessive-compulsive disorder: past, present, and future

Obsessive-compulsive disorder (OCD) is a psychiatric illness that can lead to chronic functional impairment. Some patients with severe, chronic OCD have been treated with ablative neurosurgical techniques over the past 4 decades. More recently, deep brain stimulation (DBS) has been investigated as a therapy for refractory OCD, and the procedure was granted a limited humanitarian device exemption by the FDA in 2009. In this article, the authors review the development of DBS for OCD, describe the current understanding of the pathophysiological mechanisms of the disorder and how the underlying neural circuits might be modulated by DBS, and discuss the clinical studies that provide evidence for the use of this evolving therapy. The authors conclude with suggestions for how a combined basic science and translational research approach could drive the understanding of the neural mechanisms underlying OCD as well as the clinical effectiveness of DBS in the setting of recalcitrant disease.

Deep-brain stimulation of the nucleus accumbens in obsessive compulsive disorder: clinical, surgical and electrophysiological considerations in two consecutive patients

Obsessive compulsive disorder is a highly disabling pathological condition which in the most severe and drug-resistant form can severely impair social, cognitive and interpersonal functioning. Deep-brain stimulation has been demonstrated to be an effective and safe interventional procedure in such refractory forms in selected cases. We here report the first Italian experience in the treatment of this pathology by means of nucleus accumbens stimulation, pointing out to some technical data which could be of help in localization of the target.

Deep brain stimulation of the ventral internal capsule/ventral striatum for obsessive-compulsive disorder: worldwide experience

Psychiatric neurosurgery teams in the United States and Europe have studied deep brain stimulation (DBS) of the ventral anterior limb of the internal capsule and adjacent ventral striatum (VC/VS) for severe and highly treatment-resistant obsessive-compulsive disorder. Four groups have collaborated most closely, in small-scale studies, over the past 8 years. First to begin was Leuven/Antwerp, followed by Butler Hospital/Brown Medical School, the Cleveland Clinic and most recently the University of Florida. These centers used comparable patient selection criteria and surgical targeting. Targeting, but not selection, evolved during this period. Here, we present combined long-term results of those studies, which reveal clinically significant symptom reductions and functional improvement in about two-thirds of patients. DBS was well tolerated overall and adverse effects were overwhelmingly transient. Results generally improved for patients implanted more recently, suggesting a 'learning curve' both within and across centers. This is well known from the development of DBS for movement disorders. The main factor accounting for these gains appears to be the refinement of the implantation site. Initially, an anterior-posterior location based on anterior capsulotomy lesions was used. In an attempt to improve results, more posterior sites were investigated resulting in the current target, at the junction of the anterior capsule, anterior commissure and posterior ventral striatum. Clinical results suggest that neural networks relevant to therapeutic improvement might be modulated more effectively at a more posterior target. Taken together, these data show that the procedure can be successfully implemented by dedicated interdisciplinary teams, and support its therapeutic promise.

Invasive circuitry-based neurotherapeutics: stereotactic ablation and deep brain stimulation for OCD

Psychiatric neurosurgery, specifically stereotactic ablation, has continued since the 1940s, mainly at a few centers in Europe and the US. Since the late 1990s, the resurgence of interest in this field has been remarkable; reports of both lesion procedures and the newer technique of deep brain stimulation (DBS) have increased rapidly. In early 2009, the US FDA granted limited humanitarian approval for DBS for otherwise intractable obsessive-compulsive disorder (OCD), the first such approval for a psychiatric illness. Several factors explain the emergence of DBS and continued small-scale use of refined lesion procedures. DBS and stereotactic ablation have been successful and widely used for movement disorders. There remains an unmet clinical need: current drug and behavioral treatments offer limited benefit to some seriously ill people. Understandings of the neurocircuitry underlying psychopathology and the response to treatment, while still works in progress, are much enhanced. Here, we review modern lesion procedures and DBS for OCD in the context of neurocircuitry. A key issue is that clinical benefit can be obtained after surgeries targeting different brain structures. This fits well with anatomical models, in which circuits connecting orbitofrontal cortex (OFC), medial prefrontal cortex (mPFC), basal ganglia, and thalamus are central to OCD pathophysiology and treatment response. As in movement disorders, dedicated interdisciplinary teams, here led by psychiatrists, are required to implement these procedures and maintain care for patients so treated. Available data, although limited, support the promise of stereotactic ablation or DBS in carefully selected patients. Benefit in such cases appears not to be confined to obsessions and compulsions, but includes changes in affective state. Caution is imperative, and key issues in long-term management of psychiatric neurosurgery patients deserve focused attention. DBS and contemporary ablation also present different patterns of potential benefits and burdens. Translational research to elucidate how targeting specific nodes in putative OCD circuitry might lead to therapeutic gains is accelerating in tandem with clinical use.

Scientific and ethical issues related to deep brain stimulation for disorders of mood, behavior, and thought

CONTEXT

A 2-day consensus conference was held to examine scientific and ethical issues in the application of deep brain stimulation for treating mood and behavioral disorders, such as major depression, obsessive-compulsive disorder, and Tourette syndrome.

OBJECTIVES

The primary objectives of the conference were to (1) establish consensus among participants about the design of future clinical trials of deep brain stimulation for disorders of mood, behavior, and thought and (2) develop standards for the protection of human subjects participating in such studies.

RESULTS

Conference participants identified 16 key points for guiding research in this growing field.

CONCLUSIONS

The adoption of the described guidelines would help to protect the safety and rights of research subjects who participate in clinical trials of deep brain stimulation for disorders of mood, behavior, and thought and have further potential to benefit other stakeholders in the research process, including clinical researchers and device manufactures. That said, the adoption of the guidelines will require broad and substantial commitment from many of these same stakeholders.

High-frequency stimulation of the nucleus accumbens core and shell reduces quinpirole-induced compulsive checking in rats

Electrical deep brain stimulation (DBS) is currently studied in the treatment of therapy-refractory obsessive compulsive disorders (OCDs). The variety of targeted brain areas and the inconsistency in demonstrating anti-compulsive effects, however, highlight the need for better mapping of brain regions in which stimulation may produce beneficial effects in OCD. Such a goal may be advanced by the assessment of DBS in appropriate animal models of OCD. Currently available data on DBS of the nucleus accumbens (NAc) on OCD-like behavior in rat models of OCD are contradictory and partly in contrast to clinical data and theoretical hypotheses about how the NAc might be pathophysiologically involved in the manifestation of OCD. Consequently, the present study investigates the effects of DBS of the NAc core and shell in a quinpirole rat model of OCD. The study demonstrates that electrical modulation of NAc core and shell activity via DBS reduces quinpirole-induced compulsive checking behavior in rats. We therefore conclude that both, the NAc core and shell constitute potential target structures in the treatment of OCD.

Nucleus accumbens deep brain stimulation produces region-specific alterations in local field potential oscillations and evoked responses in vivo

Deep brain stimulation of the nucleus accumbens (NAC) region is an effective therapeutic avenue for several psychiatric disorders that are not responsive to traditional treatment strategies. Nonetheless, the mechanisms by which DBS achieves therapeutic effects remain unclear. We showed previously that high-frequency (HF) NAC DBS suppressed pyramidal cell firing and enhanced slow local field potential (LFP) oscillations in the orbitofrontal cortex (OFC) via antidromic activation of corticostriatal recurrent inhibition. Using simultaneous multisite LFP recordings in urethane-anesthetized rats, we now show that NAC DBS delivered for 90 min at high or low frequency (LF) selectively affects spontaneous and evoked LFP oscillatory power and coherence within and between the medial prefrontal cortex (mPFC), lateral OFC, mediodorsal thalamus (MD), and NAC. Compared with LF or sham DBS, HF DBS enhanced spontaneous slow oscillations and potentiated evoked LFP responses only in OFC. HF DBS also produced widespread increases in spontaneous beta and gamma power and enhanced coherent beta activity between MD and all other regions. In contrast, LF DBS elevated theta power in MD and NAC. Analysis of acute NAC-induced oscillations showed that HF DBS increased and LF DBS decreased induced relative gamma coherence compared with sham DBS. These data suggest that HF (therapeutic) and LF (possibly deleterious) NAC DBS produce distinct region-specific and frequency band-specific changes in LFP oscillations. NAC DBS may achieve therapeutic effects by enhancing rhythmicity and synchronous inhibition within and between afferent structures, thereby normalizing function of a neural circuit that shows aberrant activity in obsessive-compulsive disorder and depression.

Deep brain stimulation in the treatment of obesity

Obesity is a growing global health problem frequently intractable to current treatment options. Recent evidence suggests that deep brain stimulation (DBS) may be effective and safe in the management of various, refractory neuropsychiatric disorders, including obesity. The authors review the literature implicating various neural regions in the pathophysiology of obesity, as well as the evidence supporting these regions as targets for DBS, in order to explore the therapeutic promise of DBS in obesity.

The lateral hypothalamus and ventromedial hypothalamus are the appetite and satiety centers in the brain, respectively. Substantial data support targeting these regions with DBS for the purpose of appetite suppression and weight loss. However, reward sensation associated with highly caloric food has been implicated in overconsumption as well as obesity, and may in part explain the failure rates of conservative management and bariatric surgery. Thus, regions of the brain's reward circuitry, such as the nucleus accumbens, are promising alternatives for DBS in obesity control.

The authors conclude that deep brain stimulation should be strongly considered as a promising therapeutic option for patients suffering from refractory obesity.

Deep brain stimulation of the nucleus accumbens core and shell: opposite effects on impulsive action

The nucleus accumbens is gaining interest as a target for deep brain stimulation in refractory neuropsychiatric disorders with impulsivity as core symptom. The nucleus accumbens is composed of two subterritories, core and shell, which have different anatomical connections. Here, we tested the hypothesis that stimulation of the nucleus accumbens core and shell would have different effects on impulsivity. Rats received bilateral stimulation at the level of the nucleus accumbens core or shell during a reaction time task. Stimulation of the nucleus accumbens core significantly decreased impulsivity, while stimulation of the shell increased it. Our results support the hypothesis that the nucleus accumbens is a potential target to treat neuropsychiatric disorders related to impulsivity by deep brain stimulation. However, different behavioral effects resulting from stimulation of the subterritories should be taken into account.

High frequency stimulation and temporary inactivation of the subthalamic nucleus reduce quinpirole-induced compulsive checking behavior in rats

Obsessive-compulsive disorder (OCD) represents a highly prevalent and impairing psychiatric disorder. Functional and structural imaging studies implicate the involvement of basal ganglia-thalamo-cortical circuits in the pathophysiology of this disorder. In patients remaining resistant to pharmaco- and behavioral therapy, modulation of these circuits may consequently reverse clinical symptoms. High frequency stimulation (HFS) of the subthalamic nucleus (STN), an important station of the basal ganglia-thalamo-cortical circuits, has been reported to reduce obsessive-compulsive symptoms in a few Parkinson's disease patients with comorbid OCD. The present study tested the effects of bilateral HFS of the STN and of bilateral pharmacological inactivation of the STN (via intracranial administration of the GABA agonist muscimol) on checking behavior in the quinpirole rat model of OCD. We demonstrate that both HFS and pharmacological inactivation of the STN reduce quinpirole-induced compulsive checking behavior. We conclude that functional inhibition of the STN can alleviate compulsive checking, and suggest the STN as a potential target structure for HFS in the treatment of OCD.

Behavioural and physiological effects of electrical stimulation in the nucleus accumbens: a review

Electrical stimulation (ES) in the brain is becoming a new treatment option in patients with treatment-resistant obsessive-compulsive disorder (OCD). A possible brain target might be the nucleus accumbens (NACC). This review aims to summarise the behavioural and physiological effects of ES in the NACC in humans and in animals and to discuss these findings with regard to neuroanatomical, electrophysiological and behavioural insights. The results clearly demonstrate that ES in the NACC has an effect on reward, activity, fight-or-flight, exploratory behaviour and food intake, with evidence for only moderate physiological effects. Seizures were rarely observed. Finally, the results of ES studies in patients with treatment-resistant OCD and in animal models for OCD are promising.

Anatomy and physiology of the basal ganglia: implications for DBS in psychiatry

The basal ganglia have been a target for neuromodulation surgery since Russell Meyers' pioneering works in the late 1930s. Contemporary movement disorder surgery on the brain has evolved from empiric observations on movement behavior after neurological lesions. So too has the development of psychiatric surgical procedures followed the observation of lesions in the brain on cognitive and affective behavior. Just as deep brain stimulation (DBS) has revolutionized the practice of movement disorder surgery, its application to psychiatric illness has become the cutting edge of functional and restorative neurosurgery. The fundamental concept of the cortico-striatal-pallido-thalamocortical loop will be explored in the context of psychiatric disorders. DBS targeting this circuitry appears from initial evidence in obsessive-compulsive disorder (OCD) to be a promising option for patients with neuropsychiatric illness resistant to conventional therapies. Further exploring the anatomic interconnectivity of the physiologically relevant cortical and subcortical areas will inevitably lead to better applications of DBS for the treatment of OCD, major depression (MD) and potentially for other psychiatric disorders. Implementing such therapies optimally will require the creation of treatment centers with specialized expertise in the psychiatric, neurosurgical, and ethical issues that arise with these populations.

Connections of the basal ganglia with the limbic system: implications for neuromodulation therapies of anxiety and affective disorders

The basal ganglia are best known for their role in motor planning and execution. However, it is currently widely accepted that they are also involved in cognitive and emotional behaviors. Parts of the basal ganglia play a key role in reward and reinforcement, addictive behaviors and habit formation. Pathophysiological processes underlying psychiatric disorders such as depression, obsessive compulsive disorder and even schizophrenia involve the basal ganglia and their connections to many other structures and particularly to the prefrontal cortex and the limbic system. In this article, we aim, on the basis of current research, to describe in a succinct manner the most important connections of the basal ganglia with the limbic system which are relevant to normal behaviors but also to psychiatric disorders. Currently, we possess sufficiently powerful tools that enable us to modulate brain networks such as cortex stimulation (CS) or deep brain stimulation (DBS). Notably, neuromodulation of basal ganglia function for the treatment of movement disorders has become a standard practice, which provides insights into the psychiatric problems that occur in patients with movement disorders. It is clear that a sound understanding of the currently available knowledge on the circuits connecting the basal ganglia with the limbic system will provide the theoretical platform that will allow precise, selective and beneficial neuromodulatory interventions for refractory psychiatric disorders.

Neotic preferences in laboratory rodents: Issues, assessment and substrates

Neotic preference refers to the extent to which animals prefer stimuli of differing novelty value. Degree of novelty is determined by within- and between-trials habituation and amount of temporal (novelty) and spatial change (complexity) in stimulation which in turn will determine the amount of curiosity-based approach (neophilia) or fear-based avoidance (neophobia) of novel stimuli. Tests of genuine neotic preferences enable direct assessments of responsiveness to temporal and spatial changes and include measurements of novel versus familiar locations (such as novelty-related location preferences), responsiveness to stimulus complexity (such as object exploration) and learning for exploratory rewards (such as light-contingent bar-pressing). Effects of brain lesions and peripherally administered drugs have implicated several brain areas and neurotransmitters that subserve memory, fear and reward in neotic preferences namely the hippocampus and ACh (memory), the amygdala, GABA and 5-HT (fear), and the mesolimbic DA reward system. However, more attention should be paid to the complexity of interactions between different brain and neurotransmitter systems and improvements in methodology before conclusions should be drawn about the neurobiological basis of neotic preferences.

Compulsive-like behaviour according to the sex and the reproductive stage of female rats

The aim of the present study was to explore putative differences in the responses assessed in an animal model of obsessive-compulsive disorder (OCD) according to the sex and the reproductive cycle of female rats. The model consists of the induction of perseveration (repetitive choices of the same arm in a T-maze) by 8-OH-DPAT (1.0mg/kg). Males and females (pooled in all stages of their oestrous cycle) persevered after 8-OH-DPAT administration and no differences were observed between groups. During the oestrous cycle, this 5-HT(1A) agonist induced perseveration in metoestrus, dioestrus and prooestrus and reduced levels of this behaviour in oestrus. 8-OH-DPAT provoked perseveration in mid-gestation, an effect that was reduced in late-gestation and blocked during lactation. Reproductive cycle changes in the induced perseveration are discussed from the standpoint of the ovarian steroids' action on the serotoninergic system and on the bases of the variations in stress responsiveness along the reproductive cycle of the female. Present results validate the use of females in this model of OCD and could be relevant for studying the role of reproductive hormones in the pathophysiology of this disorder.