Obsessive-compulsive and other behavioural changes with bilateral basal ganglia lesions. A neuropsychological, magnetic resonance imaging and positron tomography study

Tourette syndrome and obsessive-compulsive disorder: A comprehensive review of structural alterations and neurological mechanisms

Currently, it is possible to study the pathogenesis of Tourette's syndrome (TS) in more detail, due to more advanced methods of neuroimaging. However, medical and surgical treatment options are limited by a lack of understanding of the nature of the disorder and its relationship to some psychiatric disorders, the most common of which is obsessive-compulsive disorder (OCD). It is believed that the origin of chronic tic disorders is based on an imbalance of excitatory and inhibitory influences in the Cortico-Striato-Thalamo-Cortical circuits (CSTC). The main CSTCs involved in the pathological process have been identified by studying structural and neurotransmitter disturbances in the interaction between the cortex and the basal ganglia. A neurotransmitter deficiency in CSTC has been demonstrated by immunohistochemical and genetic methods, but it is still not known whether it arises as a consequence of genetically determined disturbances of neuronal migration during ontogenesis or as a consequence of altered production of proteins involved in neurotransmitter production. The aim of this review is to describe current ideas about the comorbidity of TS with OCD, the involvement of CSTC in the pathogenesis of both disorders and the background of structural and neurotransmitter changes in CSTC that may serve as targets for drug and neuromodulatory treatments.

Resting-state functional connectivity disruption between the left and right pallidum as a biomarker for subthreshold depression

Although the identification of late adolescents with subthreshold depression (StD) may provide a basis for developing effective interventions that could lead to a reduction in the prevalence of StD and prevent the development of major depressive disorder, knowledge about the neural basis of StD remains limited. The purpose of this study was to develop a generalizable classifier for StD and to shed light on the underlying neural mechanisms of StD in late adolescents. Resting-state functional magnetic resonance imaging data of 91 individuals (30 StD subjects, 61 healthy controls) were included to build an StD classifier, and eight functional connections were selected by using the combination of two machine learning algorithms. We applied this biomarker to an independent cohort (n = 43) and confirmed that it showed generalization performance (area under the curve = 0.84/0.75 for the training/test datasets). Moreover, the most important functional connection was between the left and right pallidum, which may be related to clinically important dysfunctions in subjects with StD such as anhedonia and hyposensitivity to rewards. Investigation of whether modulation of the identified functional connections can be an effective treatment for StD may be an important topic of future research.

The Possible Role of Apathy on Conflict Monitoring: Preliminary Findings of a Behavioral Study on Severe Acquired Brain Injury Patients Using Flanker Tasks

The diagnosis of apathy, one of the most common behavioral changes after acquired brain injury (ABI), is important for improving clinical understanding and treatment of persons with ABI. The main aim of this study was to determine the possible role of apathy in conflict monitoring, by using choice reaction time tasks. Methods: We examined behavioral responses of conflict monitoring during three different flanker tasks in 10 severe ABI patients with or without diagnosis of apathy (3 M, mean age = 56.60; 3 M, mean age ± SD = 58.60, respectively), and 15 healthy controls (9 M, mean age = 54.46) Reaction times (RTs), accuracy, and global index of performance (GIP) were analyzed for each task. Results: Only apathetic ABI patients showed a significant difference from healthy subjects (p-value ≤ 0.001), while the performance of patients without apathy was not significantly different from that of healthy controls (p-value = 0.351). Healthy participants had higher accuracy in comparison to both ABI patients with (p < 0.001) and without (p-value = 0.038) apathy, whilst slower RTs were shown by ABI patients without apathy in comparison to both healthy subjects (p-value = 0.045) and apathetic ABI patients (p-value = 0.022). Only patients with apathy exhibited a significantly higher number of missing trials (p-value = 0.001). Conclusions: Our results may suggest a potential link between apathy following severe ABI and conflict monitoring processes, even though further investigations with larger sample size are needed.

Arousal Regulation by the External Globus Pallidus: A New Node for the Mesocircuit Hypothesis

In the decade since its debut, the Mesocircuit Hypothesis (MH) has provided researchers a scaffolding for interpreting their findings by associating subcortical-cortical dysfunction with the loss and recovery of consciousness following severe brain injury. Here, we leverage new findings from human and rodent lesions, as well as chemo/optogenetic, tractography, and stimulation studies to propose the external segment of the globus pallidus (GPe) as an additional node in the MH, in hopes of increasing its explanatory power. Specifically, we discuss the anatomical and molecular mechanisms involving the GPe in sleep-wake control and propose a plausible mechanistic model explaining how the GPe can modulate cortical activity through its direct connections with the prefrontal cortex and thalamic reticular nucleus to initiate and maintain sleep. The inclusion of the GPe in the arousal circuitry has implications for understanding a range of phenomena, such as the effects of the adenosine (A2A) and dopamine (D2) receptors on sleep-wake cycles, the paradoxical effects of zolpidem in disorders of consciousness, and sleep disturbances in conditions such as Parkinson's Disease.

Back to the Future: The Role of Infections in Psychopathology. Focus on OCD

OBJECTIVE

Recently, there has been a resurgence of interest in the relationship between infections and psychopathology, given the increasing data on the neurotropism and neurological/psychiatric morbidity of the SARS-COV2 virus, responsible for the current worldwide pandemic. Although the majority of observations were those obtained in mood and schizophrenic disorders, a few data are also available on the presence of bacterial or viral infections in patients suffering from obsessive-compulsive disorder (OCD). Therefore, given the limited information, the present paper aimed at reviewing the most updated evidence of infections in neuropsychiatric disorders and their possible mechanisms of actions, with a narrow focus on microbes in OCD.

METHOD

This paper is a narrative review. The databases of PubMed, Scopus, Embase, PsycINFO and Google Scholar were accessed to research and collect English language papers published between 1 January 1980 and 31 December 2021. The data on PANDAS/PANS and those observed during severe brain infections were excluded.

RESULTS

Several pathogens have been associated with an increased risk to develop a broad spectrum of neuropsychiatric conditions, such as schizophrenia, mood disorders, autism, attention-deficit/hyperactivity disorder, anorexia nervosa, and post-traumatic stress disorder. Some evidence supported a possible role of infections also in the pathophysiology of OCD. Infections from Herpes simplex virus 1, Borna disease virus, Group A-Beta Hemolytic Streptococcus, Borrelia spp., and Toxoplasma gondii were actually found in patients with OCD. Although different mechanisms have been hypothesized, all would converge to trigger functional/structural alterations of specific circuits or immune processes, with cascade dysfunctions of several other systems.

CONCLUSIONS

Based on the current evidence, a possible contribution of different types of microbes has been proposed for different neuropsychiatric disorders including OCD. However, the currently available literature is meager and heterogeneous in terms of sample characteristics and methods used. Therefore, further studies are needed to better understand the impact of infectious agents in neuropsychiatric disorders. Our opinion is that deeper insights in this field might contribute to a better definition of biological underpinnings of specific clinical pictures, as well as to promote psychiatric precision medicine, with treatments based on altered pathological pathways of single patients. This might be particularly relevant in OCD, a disorder with a high proportion of patients who are resistant or do not respond to conventional therapeutic strategies.

Aberrant cortico-striatal white matter connectivity and associated subregional microstructure of the striatum in obsessive-compulsive disorder

The striatum and its cortical circuits play central roles in the pathophysiology of obsessive-compulsive disorder (OCD). The striatum is subdivided by cortical connections and functions; however, the anatomical aberrations in different cortico-striatal connections and coexisting microstructural anomalies in striatal subregions of OCD patients are poorly understood. Thus, we aimed to elucidate the aberrations in cortico-striatal white matter (WM) connectivity and the associated subregional microstructure of the striatum in patients with OCD. From diffusion tensor/kurtosis imaging of 107 unmedicated OCD patients and 110 matched healthy controls (HCs), we calculated the cortico-striatal WM connectivity and segmented the striatum using probabilistic tractography. For the segmented striatal subregions, we measured average diffusion kurtosis values, which represent microstructural complexity. Connectivity and mean kurtosis values in each cortical target and associated striatal subregions were compared between groups. We identified significantly reduced orbitofrontal WM connectivity with its associated striatal subregion in patients with OCD compared to that in HCs. However, OCD patients exhibited significantly increased caudal-motor and parietal connectivity with the associated striatal subregions. The mean kurtosis values of the striatal subregions connected to the caudal-motor and parietal cortex were significantly decreased in OCD patients. Our results highlighted contrasting patterns of striatal WM connections with the orbitofrontal and caudal-motor/parietal cortices, thus supporting the cortico-striatal circuitry imbalance model of OCD. We suggest that aberrations in WM connections and the microstructure of their downstream regions in the caudal-motor-/parietal-striatal circuits may underlie OCD pathophysiology and further provide potential neuromodulation targets for the treatment of OCD.

An overview of the first 5 years of the ENIGMA obsessive-compulsive disorder working group: The power of worldwide collaboration

Neuroimaging has played an important part in advancing our understanding of the neurobiology of obsessive-compulsive disorder (OCD). At the same time, neuroimaging studies of OCD have had notable limitations, including reliance on relatively small samples. International collaborative efforts to increase statistical power by combining samples from across sites have been bolstered by the ENIGMA consortium; this provides specific technical expertise for conducting multi-site analyses, as well as access to a collaborative community of neuroimaging scientists. In this article, we outline the background to, development of, and initial findings from ENIGMA's OCD working group, which currently consists of 47 samples from 34 institutes in 15 countries on 5 continents, with a total sample of 2,323 OCD patients and 2,325 healthy controls. Initial work has focused on studies of cortical thickness and subcortical volumes, structural connectivity, and brain lateralization in children, adolescents and adults with OCD, also including the study on the commonalities and distinctions across different neurodevelopment disorders. Additional work is ongoing, employing machine learning techniques. Findings to date have contributed to the development of neurobiological models of OCD, have provided an important model of global scientific collaboration, and have had a number of clinical implications. Importantly, our work has shed new light on questions about whether structural and functional alterations found in OCD reflect neurodevelopmental changes, effects of the disease process, or medication impacts. We conclude with a summary of ongoing work by ENIGMA-OCD, and a consideration of future directions for neuroimaging research on OCD within and beyond ENIGMA.

Compulsions without obsession following stroke

BACKGROUND

Obsessive-compulsive disorder (OCD) is characterized by intrusive and irrational thoughts as well as repetitive behaviours. OCD-like behaviours have been described in a wide range of neurological disorders. In cerebrovascular accidents, the semiology arises mostly from lesions to the basal ganglia - though cortical regions may also be involved. In the past few years, the mechanisms underlying OCD in psychiatric patients have been re-examined, in particular the functional relationship between anxiety, obsessions and compulsions. Traditionally, obsessions are viewed as a trigger for compulsive behaviour that represents an attempt to reduce anxiety. By contrast, other models place compulsions - as a manifestation of an imbalance between goal-directed action and automatic habits that leads to maladaptive habit learning - at the core of OCD.

CASE

We show neurological evidence of pure compulsions without obsession in a patient following stroke in the left subcortical regions. Furthermore, we present comprehensive neuropsychological findings that identify specific alterations across executive and emotional domains. Finally, MRI analyses reveal that the subcortical stroke had resulted in a strong decrease of connectivity suggestive of large network alterations.

CONCLUSIONS

Our case provides direct information on how brain structure and function relate in an OCD patient, highlighting the central role of compulsions in the pathology.

Further characterisation of psychosis-like behaviours induced by L-DOPA in the MPTP-lesioned marmoset

Parkinson's disease (PD) psychosis afflicts over half of patients and poses a significant burden on quality of life. The aetiology of PD psychosis is multifactorial and likely arises from the complex interaction between dopamine replacement therapy and disease state. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned common marmoset is a validated model to predict the efficacy of therapeutic compounds for treatment-related complications, including PD psychosis. In this model, psychosis-like behaviours (PLBs) encompass stereotypies that are idiosyncratic in nature and reproducible with each L-3,4-dihydroxyphenylanaline (L-DOPA) administration. In the present study, we sought to expand upon the existing repertoire of PLBs through the characterisation of novel stereotypical behaviours that appear dependent on the environment. We then discuss our findings in the context of clinical reports on stereotypical behaviours termed "punding" in subjects with PD, which consists of stereotypical repetitive and senseless behaviours. The poor understanding of the pathophysiology governing punding and consequent lack of effective therapies stand to benefit from enhanced characterisation of these stereotypical behaviours in a validated pre-clinical model. We hope that further characterisation of PLBs in the MPTP-lesioned marmoset will be helpful in the evaluation of interventions that seek to alleviate PD psychosis symptoms.

Chronic severe methanol intoxication after repeated mask cleansing due to fear of COVID-19: A new risk of coronaphobia

Background

Disproportionate fear of contracting COVID‐19 (coronaphobia) may result in inappropriate use of preventive measures that could, in turn, result in severe harm to the patient.

Objective

To describe a patient with subacute parkinsonism and cognitive dysfunction and magnetic resonance imaging (MRI) evidence of bilateral deep white matter and basal ganglia damage.

Case presentation

A 56‐year‐old female presented with a 4‐week history of insomnia, cognitive decline, and parkinsonism. Brain MRI revealed a bilateral lesion of both globus pallidus, deep white matter, and cerebellar hemispheres. Her son reported that, for the previous month, she had been cleaning her facial mask three times a day with a pure methanol solution as a disinfectant due to an intense fear of acquiring COVID‐19. Previously, she had used 97% isopropyl alcohol and had inadvertently switched to methanol. After the exposure ended, she slowly improved but 4 months later she remains severely disabled.

Conclusions

The repeated exposure to methanol vapor, the MRI findings, and the absence of other etiologies for her cognitive and parkinsonian features led to the diagnosis of chronic methanol intoxication with severe central nervous system damage. Misinformation is a likely contributory factor to such scenario. Efforts should be made by the scientific community to educate the general public on avoiding self‐damaging behaviors as a result of coronaphobia.

A new "sudden fright paradigm" to explore the role of (epi)genetic modulations of the DAT gene in fear-induced avoidance behavior

Alterations in dopamine (DA) reuptake are involved in several psychiatric disorders whose symptoms can be investigated in knock out rats for the DA transporter (DAT-KO). Recent studies evidenced the role of epigenetic DAT modulation in depressive-like behavior. Accordingly, we used heterozygous (HET) rats born from both HET parents (termed MIX-HET), compared to HET rats born from WT-mother and KO-father (MAT-HET), implementing the role of maternal care on DAT modulation. We developed a "sudden fright" paradigm (based on dark-light test) to study reaction to fearful inputs in the DAT-KO, MAT-HET, MIX-HET, and WT groups. Rats could freely explore the whole 3-chambers apparatus; then, they were gently confined in one room where they experienced the fright; finally, they could freely move again. As expected, after the fearful stimulus only MAT-HET rats showed a different behavior consisting of avoidance towards the fear-associated chamber, compared to WT rats. Furthermore, ex-vivo immuno-fluorescence reveals higher prefrontal DAT levels in MAT-HET compared to MIX-HET and WT rats. Immuno-fluorescence shows also a different histone deacetylase (HDAC) enzymes concentration. Since HDAC concentration could modulate gene expression, within MAT-HET fore brain, the enhanced expression of DAT could well impair the corticostriatal-thalamic circuit, thus causing aberrant avoidance behavior (observed only in MAT-HET rats). DAT expression seems to be linked to a simply different breeding condition, which points to a reduced care by HET dams for epigenetic regulation. This could imply significant prefronto-cortical influences onto the emotional processes: hence an excessively frightful response, even to mild stressful agents, may draw developmental trajectories toward anxious and depressed-like behavior.

The Psychopharmacology of Obsessive-Compulsive Disorder: A Preclinical Roadmap

This review evaluates current knowledge about obsessive-compulsive disorder (OCD), with the goal of providing a roadmap for future directions in research on the psychopharmacology of the disorder. It first addresses issues in the description and diagnosis of OCD, including the structure, measurement, and appropriate description of the disorder and issues of differential diagnosis. Current pharmacotherapies for OCD are then reviewed, including monotherapy with serotonin reuptake inhibitors and augmentation with antipsychotic medication and with psychologic treatment. Neuromodulatory therapies for OCD are also described, including psychosurgery, deep brain stimulation, and noninvasive brain stimulation. Psychotherapies for OCD are then reviewed, focusing on behavior therapy, including exposure and response prevention and cognitive therapy, and the efficacy of these interventions is discussed, touching on issues such as the timing of sessions, the adjunctive role of pharmacotherapy, and the underlying mechanisms. Next, current research on the neurobiology of OCD is examined, including work probing the role of various neurotransmitters and other endogenous processes and etiology as clues to the neurobiological fault that may underlie OCD. A new perspective on preclinical research is advanced, using the Research Domain Criteria to propose an adaptationist viewpoint that regards OCD as the dysfunction of a normal motivational system. A systems-design approach introduces the security motivation system (SMS) theory of OCD as a framework for research. Finally, a new perspective on psychopharmacological research for OCD is advanced, exploring three approaches: boosting infrastructure facilities of the brain, facilitating psychotherapeutic relearning, and targeting specific pathways of the SMS network to fix deficient SMS shut-down processes. SIGNIFICANCE STATEMENT: A significant proportion of patients with obsessive-compulsive disorder (OCD) do not achieve remission with current treatments, indicating the need for innovations in psychopharmacology for the disorder. OCD may be conceptualized as the dysfunction of a normal, special motivation system that evolved to manage the prospect of potential danger. This perspective, together with a wide-ranging review of the literature, suggests novel directions for psychopharmacological research, including boosting support systems of the brain, facilitating relearning that occurs in psychotherapy, and targeting specific pathways in the brain that provide deficient stopping processes in OCD.

Value of the Frontal Assessment Battery Tool for Assessing the Frontal Lobe Function in Stroke Patients

OBJECTIVE

To examine the correlation between the Frontal Assessment Battery (FAB) test, which is used to assess the frontal lobe function, and anatomical lesions as well as the ability of the test to detect frontal lobe dysfunction.

METHODS

Records of stroke patients undergoing a FAB test and Mini-Mental State Examination (MMSE) were retrospectively reviewed. The patients were divided into three groups according to the lesions determined by an imaging study: frontal lobe cortex lesions, frontal subcortical circuit lesions, and other lesions. The FAB scores of the three groups were compared using the Kruskal-Wallis test. The validity of the FAB test to detect frontal lobe dysfunction was assessed by a comparison with the Computerized Neuropsychological Function Test (CNT) using the Spearman correlation coefficient. The correlation coefficients between the FAB test and MMSE were analyzed further based on the MMSE cutoff score.

RESULTS

Patients with frontal cortex lesions had significantly lower total and subtest scores according to the FAB test than the other patients. The FAB test correlated better with the CNT than the MMSE, particularly in the executive function and memory domains. A high MMSE score (r=0.435) indicated a lower correlation with the FAB test score than a low MMSE score (r=0.714).

CONCLUSION

The FAB test could differentiate frontal lobe lesions from others in stroke patients and showed a good correlation with the CNT. Moreover, the FAB test can be used in patients with high MMSE scores to detect frontal lobe dysfunction and determine the treatment strategies for stroke patients.

Functional Disruption of Cerebello-thalamo-cortical Networks in Obsessive-Compulsive Disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is characterized by intrusive thoughts and repetitive, compulsive behaviors. Neuroimaging studies have implicated altered connectivity among the functional networks of the cerebral cortex in the pathophysiology of OCD. However, there has been no comprehensive investigation of the cross-talk between the cerebellum and functional networks in the cerebral cortex.

METHODS

This functional neuroimaging study was completed by 44 adult participants with OCD and 43 healthy control participants. We performed large-scale data-driven brain network analysis to identify functional connectivity patterns using resting-state functional magnetic resonance imaging data.

RESULTS

Participants with OCD showed lower functional connectivity within the somatomotor network and greater functional connectivity among the somatomotor network, cerebellum, and subcortical network (e.g., thalamus and pallidum; all p < .005). Network-based statistics analyses demonstrated one component comprising connectivity within the somatomotor network that showed lower connectivity and a second component comprising connectivity among the somatomotor network, and motor regions in particular, and the cerebellum that showed greater connectivity in participants with OCD relative to healthy control participants. In participants with OCD, abnormal connectivity across both network-based statistics-derived components positively correlated with OCD symptom severity (p = .006).

CONCLUSIONS

To our knowledge, this study is the first comprehensive investigation of large-scale network alteration across the cerebral cortex, subcortical regions, and cerebellum in OCD. Our findings highlight a critical role of the cerebellum in the pathophysiology of OCD.

The anterior limb of the internal capsule: Anatomy, function, and dysfunction

The last two decades have seen a re-emergence of neurosurgery for severe, refractory psychiatric diseases, largely due to the advent of more precise and safe operative techniques. Nevertheless, the optimal targets for these surgeries remain a matter of debate, and are often grandfathered from experiences in the late 20th century. To better explore the rationale for one target in particular - the anterior limb of the internal capsule (ALIC) - we comprehensively reviewed all available literature on its role in the pathophysiology and treatment of mental illness. We first provide an overview of its functional anatomy, followed by a discussion on its role in several prevalent psychiatric diseases. Given its structural integration into the limbic system and involvement in a number of cognitive and emotional processes, the ALIC is a robust target for surgical treatment of refractory psychiatric diseases. The advent of novel neuroimaging techniques, coupled with image-guided therapeutics and neuromodulatory treatments, will continue to enable study on the ALIC in mental illness.

On the pathophysiology and treatment of akinetic mutism

Akinetic mutism (AM) is a rare neurological disorder characterized by the presence of an intact level of consciousness and sensorimotor capacity, but with a simultaneous decrease in goal-directed behavior and emotions. Patients are in a wakeful state of profound apathy, seemingly indifferent to pain, thirst, or hunger. It represents the far end within the spectrum of disorders of diminished motivation. In recent years, more has become known about the functional roles of neurocircuits and neurotransmitters associated with human motivational behavior. More specific, there is an increasing body of behavioral evidence that links specific damage of functional frontal-subcortical organization to the occurrence of distinct neurological deficits. In this review, we combine evidence from lesion studies and neurophysiological evidence in animals, imaging studies in humans, and clinical investigations in patients with AM to form an integrative theory of its pathophysiology. Moreover, the specific pharmacological interventions that have been used to treat AM and their rationales are reviewed, providing a comprehensive overview for use in clinical practice.

The Cortico-Basal Ganglia-Cerebellar Network: Past, Present and Future Perspectives

Much of our present understanding of the function and operation of the basal ganglia rests on models of anatomical connectivity derived from tract-tracing approaches in rodents and primates. However, the last years have been characterized by promising step forwards in the in vivo investigation and comprehension of brain connectivity in humans. The aim of this review is to revise the current knowledge on basal ganglia circuits, highlighting similarities and differences across species, in order to widen the current perspective on the intricate model of the basal ganglia system. This will allow us to explore the implications of additional direct pathways running from cortex to basal ganglia and between basal ganglia and cerebellum recently described in animals and humans.

Exploration Deficits Under Ecological Conditions as a Marker of Apathy in Frontotemporal Dementia

Apathy is one of the six clinical criteria for the behavioral variant of frontotemporal dementia (bvFTD), and it is almost universal in this disease. Although its consequences in everyday life are debilitating, its underlying mechanisms are poorly known, its assessment is biased by subjectivity and its care management is very limited. In this context, we have developed "ECOCAPTURE," a method aimed at providing quantifiable and objective signature(s) of apathy in order to assess it and identify its precise underlying mechanisms. ECOCAPTURE consists of the observation and recording of the patient's behavior when the participant is being submitted to a multiple-phase scenario reproducing a brief real-life situation. It is performed in a functional exploration platform transformed into a fully furnished waiting room equipped with a video and sensor-based data acquisition system. This multimodal method allowed video-based behavior analyses according to predefined behavioral categories (exploration behavior, sustained activities or inactivity) and actigraphy analyses from a 3D accelerometer. The data obtained were also correlated with behavioral/cognitive tests and scales assessing global cognitive efficiency, apathy, cognitive disinhibition, frontal syndrome, depression and anxiety. Here, bvFTD patients (n = 14) were compared to healthy participants (n = 14) during the very first minutes of the scenario, when the participants discovered the room and were encouraged to explore it. We showed that, in the context of facing a new environment, healthy participants first explored it and then engaged in sustained activities. By contrast, bvFTD patients were mostly inactive and eventually explored this new place, but in a more irregular and less efficient mode than normal subjects. This exploration deficit was correlated with apathy, disinhibition and cognitive and behavioral dysexecutive syndromes. These findings led us to discuss the presumed underlying mechanisms responsible for the exploration deficit (an inability to self-initiate actions, to integrate reward valuation and to inhibit involuntary behavior). Altogether, these results pave the way for simple and objective assessment of behavioral changes that represents a critical step for the evaluation of disease progression and efficacy of treatment in bvFTD.

Why not try harder? Computational approach to motivation deficits in neuro-psychiatric diseases

Motivation deficits, such as apathy, are pervasive in both neurological and psychiatric diseases. Even when they are not the core symptom, they reduce quality of life, compromise functional outcome and increase the burden for caregivers. They are currently assessed with clinical scales that do not give any mechanistic insight susceptible to guide therapeutic intervention. Here, we present another approach that consists of phenotyping the behaviour of patients in motivation tests, using computational models. These formal models impose a precise and operational definition of motivation that is embedded in decision theory. Motivation can be defined as the function that orients and activates the behaviour according to two attributes: a content (the goal) and a quantity (the goal value). Decision theory offers a way to quantify motivation, as the cost that patients would accept to endure in order to get the benefit of achieving their goal. We then review basic and clinical studies that have investigated the trade-off between the expected cost entailed by potential actions and the expected benefit associated with potential rewards. These studies have shown that the trade-off between effort and reward involves specific cortical, subcortical and neuromodulatory systems, such that it may be shifted in particular clinical conditions, and reinstated by appropriate treatments. Finally, we emphasize the promises of computational phenotyping for clinical purposes. Ideally, there would be a one-to-one mapping between specific neural components and distinct computational variables and processes of the decision model. Thus, fitting computational models to patients' behaviour would allow inferring of the dysfunctional mechanism in both cognitive terms (e.g. hyposensitivity to reward) and neural terms (e.g. lack of dopamine). This computational approach may therefore not only give insight into the motivation deficit but also help personalize treatment.

Relationship between toxoplasmosis and obsessive compulsive disorder: A systematic review and meta-analysis

Background

A few studies investigated the relationship between toxoplasmosis and mental disorders, such as obsessive compulsive disorder (OCD). However, the specific nature of the association between Toxoplasma gondii (T. gondii) infection and OCD is not yet clear. The aim of this study was to collect information on the relationship between OCD and toxoplasmosis and assess whether patients with toxoplasmosis are prone to OCD.

Methods

For the purpose of this study, 6 major electronic databases and the Internet search engine Google Scholar were searched for the published articles up to July 30^th, 2018 with no restriction of language. The inverse variance method and the random effect model were used to combine the data. The values of odds ratio (OR) were estimated at 95% confidence interval (CI).

Results

A total of 9 case-control and 3 cross-sectional studies were included in our systematic review. However, 11 of these 12 articles were entered into the meta-analysis containing 9873 participants, out of whom 389 were with OCD (25.96% positive for toxoplasmosis) and 9484 were without OCD (17.12% positive for toxoplasmosis). The estimation of the random effect model indicated a significant common OR of 1.96 [95% CI: 1.32–2.90].

Conclusion

This systematic review and meta-analysis revealed that toxoplasmosis could be as an associated factor for OCD (OR = 1.96). However, further prospective investigations are highly recommended to illuminate the underlying pathophysiological mechanisms of T. gondii infection in OCD and to better investigate the relationship between OCD and T. gondii infection.

Toxoplasma gondii (T. gondii) is an obligate neurotropic parasite that infected about 25–30% of the total human population in the developed and developing countries. The obsessive compulsive disorder (OCD) is a psychiatric disease that affects the income and quality of life. Some studies confirmed an association between infectious agents as the associated or protective factors specifying the development of psychiatry diseases. Among various pathogens associated with psychological disorders, most of the attention is on T. gondii, which has a life-long asymptomatic latent phase after a short acute stage in healthy individuals. The detrimental effect of T. gondii on immunocompromised people and pregnant women is an important concern for public health. The correlation between toxoplasmosis and OCD is still relatively understudied with a paucity of documented findings. The previous meta-analysis reviewed only two studies and reported a 3.4-fold greater chance of OCD. The results of our study presented stronger evidence of a positive relationship between toxoplasmosis and OCD. Eventually, our research team hopes to present an overview of what is known and encourage more intensive research to determine the real impact of this parasite on the occurrence of OCD that may contribute to the prevention of OCD worldwide.

Fronto-Subcortical Circuits for Cognition and Motivation: Dissociated Recovery in a Case of Loss of Psychic Self-Activation

In humans and non-humans primates, extensive evidence supports the existence of subcortico-cortical circuits for cognition and behavior. Lesions studies are critical to understand the clinical significance of these functionally segregated circuits. Mapping these circuits from lesion studies is difficult given the heterogeneous etiology of the lesions, the lack of long-term and systematic testing of cognitive and behavioral disturbances, as well as the scarcity of neuroimaging data for identifying the precise location and extent of subcortical lesions. Here, we report the long-term follow-up study of a patient who developed a loss of psychic self-activation associated to a dysexecutive syndrome following resuscitation from cardiac arrest. Neuroimaging revealed extensive bilateral lesions in the putamen, with a relative spare of the caudate, and exhibiting a dorsoventral gradient that was predominantly rostrally to the anterior commissure and spared most of the ventral striatum. In comprehensive neuropsychological and neuropsychiatric assessments, we observed dissociation between the improvement of the self-activation deficits and the stability of the dysexecutive syndrome. The pattern of recovery after this lesion lends support to current models proposing the existence of two main subcortico-cortical circuits: a dorsal circuit, mostly mediating cognitive processes, and a ventral circuit, implicated in motivation.

Corticopallidal Connectome of the Globus Pallidus Externus in Humans: An Exploratory Study of Structural Connectivity Using Probabilistic Diffusion Tractography

BACKGROUND AND PURPOSE

Electrophysiologic abnormalities of the globus pallidus externus have been shown in several disease processes including Parkinson disease, dystonia, and Huntington disease. However, the connectivity, nuclear structure, and function of the globus pallidus externus are still not well-understood. Increasing evidence for the existence of direct corticopallidal connections challenges traditional understanding of the connectivity of the globus pallidus externus; nevertheless, these corticopallidal connections have yet to be fully characterized in humans. The objective of this study was to assess the corticopallidal connections of the globus pallidus externus by means of probabilistic diffusion-weighted MR imaging tractography using high-resolution, multishell data.

MATERIALS AND METHODS

Imaging data from the open-access Human Connectome Project data base were used to perform probabilistic tractography between the globus pallidus externus and the cerebral cortex using 34 distinct cortical regions. Group averages were calculated for normalized percentages of tracts reaching each of the cortical targets, and side-to-side comparison was made.

RESULTS

Cortical connectivity was demonstrated between the globus pallidus externus and multiple cortical regions, including direct connection to putative sensorimotor, associative, and limbic areas. Connectivity patterns were not significantly different between the right and left hemispheres with the exception of the frontal pole, which showed a greater number of connections on the right (P = .004).

CONCLUSIONS

Our in vivo study of the human globus pallidus externus using probabilistic tractography supports the existence of extensive corticopallidal connections and a tripartite functional division, as found in animal studies. A better understanding of the connectivity of the globus pallidus externus may help to understand its function and elucidate the effects of programming the higher contacts in pallidal deep brain stimulation.

Neuroscience of apathy and anhedonia: a transdiagnostic approach

Apathy and anhedonia are common syndromes of motivation that are associated with a wide range of brain disorders and have no established therapies. Research using animal models suggests that a useful framework for understanding motivated behaviour lies in effort-based decision making for reward. The neurobiological mechanisms underpinning such decisions have now begun to be determined in individuals with apathy or anhedonia, providing an important foundation for developing new treatments. The findings suggest that there might be some shared mechanisms between both syndromes. A transdiagnostic approach that cuts across traditional disease boundaries provides a potentially useful means for understanding these conditions.

Corticosterone Signaling and a Lateral Habenula-Ventral Tegmental Area Circuit Modulate Compulsive Self-Injurious Behavior in a Rat Model

Self-injurious behavior (SIB) is commonly observed in patients with neuropsychiatric disorders, as well as in nonclinical populations with stress-related mental-health problems. However, the exact circuitry mechanisms underlying SIB have remained poorly understood. Here, with bilateral injection of muscimol into the entopeduncular nucleus (EP), we established a rat model of SIB. Following the muscimol injection, the male rats exhibited in a dose-dependent manner stereotypic self-biting behavior that lasted for hours and often resulted in wounds of various severities. The SIB was associated with an elevated level of serum corticosterone and could be exacerbated by enhancing the corticosterone signaling and, conversely, alleviated by inhibiting the corticosterone signaling. Activity mapping using c-fos immunostaining, combined with connectivity mapping using herpes simplex virus-based anterograde tracing from the EP and pseudorabies virus-based retrograde tracing from the masseter muscle, revealed the potential involvement of many brain areas in SIB. In particular, the lateral habenula (LHb) and the ventral tegmental area (VTA), the two connected brain areas involved in stress response and reward processing, showed a significant increase in neuronal activation during SIB. Furthermore, suppressing the LHb activity or modulating the GABAergic transmission in the VTA could significantly reduce the occurrence of SIB. These results demonstrate the importance of stress hormone signaling and the LHb-VTA circuit in modulating SIB resulting from EP malfunction, and suggest potential targets for therapeutic intervention of SIB and related disorders.SIGNIFICANCE STATEMENT Self-injurious behavior (SIB) occurs in ∼4% of the general population, with substantially higher occurrence among adolescents and patients of neuropsychiatric disorders. Stress has been linked to the occurrence of SIB, yet the underlying mechanisms have remained unclear. Using a rat model of SIB induced by disruption of activity in the entopeduncular nucleus (EP), we found that the behavior is regulated by stress and linked to corticosterone signaling. Viral tracing and c-fos immunostaining revealed the involvement of various subcortical areas, especially the EP-lateral habenula (LHb)-ventral tegmental area (VTA) circuit, in SIB. Furthermore, regulating activity in the LHb or the VTA alleviates SIB. These results may have implications in the development of new strategies for treating SIB.

Tourette Syndrome: A Mini-Review

The purpose of this mini-review is to provide the latest information on epidemiology, pathophysiology, diagnosis, and treatment of Tourette syndrome (TS). The authors conducted a literature search of available sources describing the issue of tic disorders with special focus on TS and made a comparison and evaluation of relevant findings. The results of this mini-review indicate that TS is a complex disorder, which has a significant impact on the quality of life of both the patients and his/her family. Therefore, early and proper diagnosis and treatment are necessary in order to reduce or even eliminate both symptoms and social burden of the patient. This requires a multidisciplinary management approach in order to meet the patients' special needs. Future research should focus on neuroimaging, new neurotransmitter targets, in functional neurosurgery, as well as the effect of non-pharmacological psychotherapies for these people.

The pathophysiological mechanisms of motivational deficits in Parkinson's disease

Parkinson's disease (PD) is a progressive degenerative disorder that leads to disabling motor symptoms and a wide variety of neuropsychiatric symptoms. Apathy is the most common psychiatric disorder in the early stages of untreated PD and can be defined as a hypodopaminergic syndrome, which also includes anxiety and depression. Apathy is also considered the core feature of the parkinsonian triad (apathy, anxiety and depression) of behavioural non-motor signs, including a motivational deficit. Moreover, apathy is recognised as a distinct chronic neuropsychiatric behavioural disorder based on specific diagnostic criteria. Given the prevalence of apathy in approximately 40% of the general Parkinson's disease population, this appears to be a contributing factor to dementia in PD; also, apathy symptoms are factors that potentially contribute to morbidity, leading to a major impairment of health-related quality of life, thus stressing the importance of understanding the pathophysiology of this disease. Several studies have clearly established a prominent role for DA-mediated signals in PD apathy. However, synergistic interaction between dopaminergic impairment resulting from the neurodegenerative process and deep brain stimulation of the subthalamic nucleus may cause or exacerbate apathy. Furthermore, serotoninergic mechanism signalling is also likely to be of importance in this pathophysiology.

EEG-arousal regulation as predictor of treatment response in patients suffering from obsessive compulsive disorder

OBJECTIVES

Aim of this study was to analyze whether electroencephalogram (EEG)-based CNS-arousal markers differ for patients suffering from obsessive compulsive disorder (OCD) that either respond or do not respond to cognitive behavioral therapy (CBT), selective serotonin reuptake inhibitors (SSRIs) or their combination. Further the study aimed to identify specific response-predictors for the different therapy approaches.

METHODS

CNS-arousal from 51 unmedicated patients during fifteen-minute resting state was assessed using VIGALL (Vigilance Algorithm Leipzig). Clinical Global Impression (CGI) scores were used to assess response or non-response after three to six months following therapy (CBT, n=18; SSRI, n=11 or combination, n=22). Differences between Responders (R) and Non-Responders (NR) were identified using multivariate analysis of covariance (MANCOVA) models.

RESULTS

MANCOVA revealed that Responders spent significant less time at the highest CNS-arousal stage 0. Further, low amounts of the highest CNS-arousal stages were specifically predictive for a response to a combined treatment approach.

CONCLUSIONS

The fact that CNS-arousal markers allowed discrimination between Responders and Non-Responders and also between Responders of different treatment arms underlines a possible clinical value of EEG-based markers.

SIGNIFICANCE

These results encourage further research on EEG-arousal regulation for determining pathophysiological subgroups for treatment response.

Neuropsychiatric Burden in Huntington's Disease

Huntington's disease is a disorder that results in motor, cognitive, and psychiatric problems. The symptoms often take different forms and the presence of disturbances of the psychic sphere reduces patients' autonomy and quality of life, also impacting patients' social life. It is estimated that a prevalence between 33% and 76% of the main psychiatric syndromes may arise in different phases of the disease, often in atypical form, even 20 years before the onset of chorea and dementia. We present a narrative review of the literature describing the main psychopathological patterns that may be found in Huntington's disease, searching for a related article in the main database sources (Medline, ISI Web of Knowledge, Scopus, and Medscape). Psychiatric conditions were classified into two main categories: affective and nonaffective disorders/symptoms; and anxiety and neuropsychiatric features such as apathy and irritability. Though the literature is extensive, it is not always convergent, probably due to the high heterogeneity of methods used. We summarize main papers for pathology and sample size, in order to present a synoptic vision of the argument. Since the association between Huntington's disease and psychiatric symptoms was demonstrated, we argue that the prevalent and more invalidating psychiatric components should be recognized as early as possible during the disease course in order to best address psychopharmacological therapy, improve quality of life, and also reduce burden on caregivers.

Ventral Pallidum Encodes Contextual Information and Controls Aversive Behaviors

Successful avoidance of aversive outcomes is crucial for the survival of animals. Although accumulating evidence indicates that an indirect pathway in the basal ganglia is involved in aversive behavior, the ventral pallidum (VP), which is an important component of this pathway, has so far been implicated primarily in appetitive behavior. In this study, we used single-cell recordings and bicuculline (GABAA antagonist) injections to elucidate the role of VP both in the encoding of aversive context and in active avoidance. We found 2 populations of neurons that were preferentially activated by appetitive and aversive conditioned stimuli (CSs). In addition, VP showed appetitive and aversive outcome anticipatory activities. These activity patterns indicate that VP is involved in encoding and maintaining CS-induced aversive contextual information. Furthermore, the disturbance of VP activity by bicuculline injection increased the number of error trials in aversive trials. In particular, the subjects released the response bar prematurely, showed no response at all, or failed to avoid the aversive outcome. Overall, these results suggest that VP plays a central role in controlling CS-induced negative motivation to produce avoidance behavior.

Reward sensitivity deficits modulated by dopamine are associated with apathy in Parkinson's disease

Apathy is a debilitating and under-recognized condition that has a significant impact in many neurodegenerative disorders. In Parkinson's disease, it is now known to contribute to worse outcomes and a reduced quality of life for patients and carers, adding to health costs and extending disease burden. However, despite its clinical importance, there remains limited understanding of mechanisms underlying apathy. Here we investigated if insensitivity to reward might be a contributory factor and examined how this relates to severity of clinical symptoms. To do this we created novel ocular measures that indexed motivation level using pupillary and saccadic response to monetary incentives, allowing reward sensitivity to be evaluated objectively. This approach was tested in 40 patients with Parkinson's disease, 31 elderly age-matched control participants and 20 young healthy volunteers. Thirty patients were examined ON and OFF their dopaminergic medication in two counterbalanced sessions, so that the effect of dopamine on reward sensitivity could be assessed. Pupillary dilation to increasing levels of monetary reward on offer provided quantifiable metrics of motivation in healthy subjects as well as patients. Moreover, pupillary reward sensitivity declined with age. In Parkinson's disease, reduced pupillary modulation by incentives was predictive of apathy severity, and independent of motor impairment and autonomic dysfunction as assessed using overnight heart rate variability measures. Reward sensitivity was further modulated by dopaminergic state, with blunted sensitivity when patients were OFF dopaminergic drugs, both in pupillary response and saccadic peak velocity response to reward. These findings suggest that reward insensitivity may be a contributory mechanism to apathy and provide potential new clinical measures for improved diagnosis and monitoring of apathy.media-1vid110.1093/brain/aww188_video_abstractaww188_video_abstract.

Executive functions in obsessive-compulsive disorder: An activation likelihood estimate meta-analysis of fMRI studies

OBJECTIVES

To identify activation changes assessed in functional magnetic resonance imaging (fMRI) studies of obsessive-compulsive disorder (OCD) through Activation Likelihood Estimate meta-analysis.

METHODS

We included 28 peer-reviewed standard stereotactic space studies assessing adult OCD patients (OCDpts) vs. healthy controls (HCs) with fMRI during executive task performance.

RESULTS

In within-group analyses, HCs showed task-related activations in bilateral inferior frontal gyri, right middle frontal gyrus, right inferior parietal lobule, right claustrum, bilateral cingulate gyri, and left caudate body. OCDpts showed task-related left-sided activations in the superior, medial, and inferior frontal gyri, and thalamus, and bilateral activations in the middle frontal gyri, inferior parietal lobule, and insular cortices. Subtraction analysis showed increased left middle frontal gyrus activation in OCDpts. In between-groups analyses, OCDpts hypoactivated the right caudate body, left putamen, left ACC, and right medial and middle frontal gyri. Right caudate hypoactivation persisted also after applying Family-wise error algorithms.

CONCLUSIONS

This meta-analysis confirms that during executive functioning OCDpts show a functional deficit of the right caudate body, which could represent a major neural functional correlate of their illness.

Executive Dysfunction in Patients with Putaminal Hemorrhage

BACKGROUND

The frontal-subcortical circuits link the specific areas of the frontal cortex to the striatum, basal ganglia, and thalamus. Disruption of the frontal-subcortical circuits may lead to cognitive impairment with frontal lobe features. The putamen is a central component of frontal-subcortical circuits. Although putaminal lesions presumably lead to cognitive and behavioral changes, studies on frontal lobe dysfunctions after putaminal stroke are scarce. There are no previous studies that systematically examined frontal lobe functions with a focal putaminal lesion. The objective of this study is to demonstrate whether putaminal hemorrhage causes frontal lobe dysfunction.

METHODS

Cognitive functions, including various aspects of frontal lobe functions, were systematically assessed in 15 patients with left- or right-sided putaminal hemorrhage 2 months after the onset and compared with healthy controls.

RESULTS

Patients did not have signs of aphasia, apraxia, or spatial neglect. They performed significantly worse on tests of frontal lobe function, including Letter-Number Sequencing (U = 22, P < .001), lexical fluency (U = 30, P < .001), and motor series subtest (U = 45, P = .004) of the Frontal Assessment Battery. On the Wisconsin Card Sorting Test, patients performed significantly worse for "categories achieved" (U = 29.5, P < .001), "perseverative errors" (U = 25, P < .001), and "set loss" (U = 49, P = .008). None showed behavioral impairment.

CONCLUSIONS

Isolated putaminal hemorrhage causes modest frontal lobe dysfunction without behavioral symptoms. Our findings indicate that isolated putaminal hemorrhage disrupts the dorsolateral-striato-pallido-thalamic circuits and causes executive dysfunction.

Gray Matter Volume Changes in the Apathetic Elderly

This study is to test the hypothesis that apathy in healthy participants is closely related to the prefrontal-basal-ganglia circuit and associated structural changes. We selected 36 healthy aged participants with (n = 18) or without apathy (n = 18) from our database. Participants underwent structural MRI scanning, providing data for voxel-based morphometric analysis to explore gray matter changes associated with apathy. Compared to the non-apathy group, the apathy group showed reduced gray matter volume of the right putamen, whereas volumes of the bilateral inferior frontal gyri and left inferior occipital gyrus showed increase. When depression scores were included in a regression model as a covariate, apathetic participants showed decreased gray matter volume in the right precentral gyrus compared to the non-apathetic participants. These findings suggest that apathy is associated with the gray matter volume in the prefrontal-basal-ganglia network, and may have a neuroanatomical basis distinct from depression in healthy elderly.

Cognitive severity-specific neuronal degenerative network in charcoal burning suicide-related carbon monoxide intoxication: a multimodality neuroimaging study in Taiwan

While carbon monoxide (CO) intoxication often triggers multiple intraneuronal immune- or inflammatory-related cascades, it is not known whether the pathological processes within the affected regions evolve equally in the long term. To understand the neurodegenerative networks, we examined 49 patients with a clinical diagnosis of CO intoxication related to charcoal burning suicide at the chronic stage and compared them with 15 age- and sex-matched controls. Reconstructions of degenerative networks were performed using T1 magnetic resonance imaging, diffusion-tensor imaging, and fluorodeoxyglucose positron emission tomography (PET). Tract-specific fractional anisotropy (FA) quantification of 11 association fibers was performed while the clinical significance of the reconstructed structural or functional networks was determined by correlating them with the cognitive parameters. Compared with the controls, the patients had frontotemporal gray matter (GM) atrophy, diffuse white matter (WM) FA decrement, and axial diffusivity (AD) increment. The patients were further stratified into 3 groups based on the cognitive severities. The spatial extents within the frontal-insular-caudate GM as well as the prefrontal WM AD increment regions determined the cognitive severities among 3 groups. Meanwhile, the prefrontal WM FA values and PET signals also correlated significantly with the patient's Mini-Mental State Examination score. Frontal hypometabolic patterns in PET analysis, even after adjusted for GM volume, were highly coherent to the GM atrophic regions, suggesting structural basis of functional alterations. Among the calculated major association bundles, only the anterior thalamic radiation FA values correlated significantly with all chosen cognitive scores. Our findings suggest that fronto-insular-caudate areas represent target degenerative network in CO intoxication. The topography that occurred at a cognitive severity-specific level at the chronic phase suggested the clinical roles of frontal areas. Although changes in FA are also diffusely distributed, different regional changes in AD suggested unequal long-term compensatory capacities among WM bundles. As such, the affected WM regions showing irreversible changes may exert adverse impacts to the interconnected GM structures.

A direct GABAergic output from the basal ganglia to frontal cortex

The basal ganglia (BG) are phylogenetically conserved subcortical nuclei necessary for coordinated motor action and reward learning¹. Current models postulate that the BG modulate cerebral cortex indirectly via an inhibitory output to thalamus, bidirectionally controlled by the BG via direct (dSPNs) and indirect (iSPNs) pathway striatal projection neurons^2–4. The BG thalamic output sculpts cortical activity by interacting with signals from sensory and motor systems⁵. Here we describe a direct projection from the globus pallidus externus (GP), a central nucleus of the BG, to frontal regions of the cerebral cortex (FC). Two cell types make up the GP-FC projection, distinguished by their electrophysiological properties, cortical projections and expression of choline acetyltransferase (ChAT), a synthetic enzyme for the neurotransmitter acetylcholine (ACh). Despite these differences, ChAT+ cells, which have been historically identified as an extension of the nucleus basalis (NB), as well as ChAT− cells, release the inhibitory neurotransmitter GABA (γ-aminobutyric acid) and are inhibited by iSPNs and dSPNs of dorsal striatum. Thus GP-FC cells comprise a direct GABAergic/cholinergic projection under the control of striatum that activates frontal cortex in vivo. Furthermore, iSPN inhibition of GP-FC cells is sensitive to dopamine 2 receptor signaling, revealing a pathway by which drugs that target dopamine receptors for the treatment of neuropsychiatric disorders can act in the BG to modulate frontal cortices.

¹⁸F-FP-(+)-DTBZ positron emission tomography detection of monoaminergic deficient network in patients with carbon monoxide related parkinsonism

BACKGROUND AND PURPOSE

Although parkinsonism after carbon monoxide (CO) intoxication is well known, neurotransmitter deficient networks that are responsible for the severity of parkinsonism have rarely been systemically evaluated.

METHODS

Eighteen patients with CO-related parkinsonism and nine age- and sex-matched controls were enrolled for detailed neurological examinations, three-dimensional T1-weighted images, diffusion tensor imaging and (18)F-9-fluoropropyl-(+)-dihydrotetrabenzazine ((18)F-FP-(+)-DTBZ) positron emission tomography (PET). The structural analysis included voxel-based morphometry to assess grey matter atrophy and tract-based spatial statistics related to white matter involvement. For presynaptic monoaminergic assessment, volume of interest analysis in six subcortical regions and non-parametric voxel-wise comparison were performed on PET images with estimation of registration parameters from magnetic resonance images. All the imaging modalities were compared between the patients and controls. For the patients, a regression model for correlation with cognitive behaviour and Unified Parkinson's Disease Rating Scale (UPDRS) score was used.

RESULTS

In the patients, monoaminergic deficit networks were found in the caudate, anterior putamen, anterior insular, thalamus and anterior cingulate cortex. The UPDRS revealed significant correlations with the prefrontal white matter fractional anisotropy values and with the (18)F-FP-(+)-DTBZ uptake values in the caudate nucleus, insular, medial prefrontal and dorsomedial thalamus. The neuropsychiatric inventory score correlated with the (18)F-FP-(+)-DTBZ uptake values in the anterior cingulate cortex and dorsolateral prefrontal cortex.

CONCLUSIONS

Our study demonstrated monoaminergic deficits and white matter damage networks in CO-related parkinsonism that determined the severity of parkinsonism or behaviour changes. As the substantia nigra was spared, the monoaminergic topography of involvement suggests a different pathophysiology in CO-related parkinsonism.

Pharmacologic MRI (phMRI) as a tool to differentiate Parkinson's disease-related from age-related changes in basal ganglia function

The prevalence of both parkinsonian signs and Parkinson's disease (PD) per se increases with age. Although the pathophysiology of PD has been studied extensively, less is known about the functional changes taking place in the basal ganglia circuitry with age. To specifically address this issue, 3 groups of rhesus macaques were studied: normal middle-aged animals (used as controls), middle-aged animals with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism, and aged animals (>20 years old) with declines in motor function. All animals underwent the same behavioral and pharmacologic magnetic resonance imaging (phMRI) procedures to measure changes in basal ganglia function in response to dopaminergic drug challenges consisting of apomorphine administration followed by either a D1 (SCH23390) or a D2 (raclopride) receptor antagonist. Significant functional changes were predominantly seen in the external segment of the globus pallidus (GPe) in aged animals and in the striatum (caudate nucleus and putamen) in MPTP-lesioned animals. Despite significant differences seen in the putamen and GPe between MPTP-lesioned versus aged animals, a similar response profile to dopaminergic stimulations was found between these 2 groups in the internal segment of the GP. In contrast, the pharmacologic responses seen in the control animals were much milder compared with the other 2 groups in all the examined areas. Our phMRI findings in MPTP-lesioned parkinsonian and aged animals suggest that changes in basal ganglia function in the elderly may differ from those seen in parkinsonian patients and that phMRI could be used to distinguish PD from other age-associated functional alterations in the brain.

The cognitive spectrum in neurodegenerative Langerhans cell histiocytosis

Clinical spectrum of cognitive troubles complicating neurodegenerative Langerhans cell histiocytosis (ND-LCH) is poorly known. The aim of this study is to evaluate cognitive functions in ND-LCH. The cognitive functions of a series of eight adult patients (7 males and 1 female; mean age 26 years IQ 25-75; range 20-33) suffering from clinical and/or radiological ND-LCH were evaluated using the following tests: (1) forward/backward digit and spatial span tasks of the WAIS-R scale and the Corsi block task, (2) the French version of the free and cued selective reminding test, (3) verbal fluency tests, (4) the Frontal Assessment Battery (FAB), (5) backward measurement of the verbal and visuospatial memories of the WAIS-R scale, (6) the Rey complex figure test, (7) the trail making tests A and B, (8) digit symbol and symbol search of the WAIS-IV scale, and (9) the Stroop test. Episodic (i.e. autobiographical or personal) memory free recall, categorical verbal fluency, phonological verbal fluency, visuospatial processing skills, attention, speed of processing, and sensitivity to interference were impaired in ND-LCH patients. In contrast, verbal and visuospatial short-term memories (i.e. immediate memories or forward span tasks) were preserved in all patients. Adult ND-LCH patients suffer from a severe but dissociated dysexecutive syndrome, mostly affecting executive strategies and relatively sparing short-term memory. Our study supports the need of assessing executive functions using comprehensive cognitive evaluation in ND-LCH patients for early diagnosis.

Pathological generosity: an atypical impulse control disorder after a left subcortical stroke

Changes in socio-emotional behavior and conduct, which are characteristic symptoms of frontal lobe damage, have less often been described in patients with focal subcortical injuries. We report on a case of pathological generosity secondary to a left lenticulocapsular stroke with hypoperfusion of several anatomically intact cortical areas. A 49-year-old man developed excessive and persistent generosity as he recovered from a left lenticulocapsular hematoma. His symptoms resembled an impulse control disorder. (99m)Tc-HMPAO SPECT demonstrated hypoperfusion mostly in the ipsilateral striatum, dorsolateral, and orbitofrontal cortex. This case study adds pathological generosity to the range of behavioral changes that may result from discrete unilateral lesions of the lenticular nucleus and nearby pathways. In our particular case, post-stroke pathological generosity was not ascribable to disinhibition, apathy, mania, or depression. Because pathological generosity may lead to significant distress and financial burden upon patients and their families, it may warrant further consideration as a potential type of impulse control disorder.

Neurosurgical targets for compulsivity: what can we learn from acquired brain lesions?

Treatment efficacy of deep brain stimulation (DBS) and other neurosurgical techniques in refractory obsessive-compulsive disorder (OCD) is greatly dependent on the targeting of relevant brain regions. Over the years, several case reports have been published on either the emergence or resolution of obsessive-compulsive symptoms due to neurological lesions. These reports can potentially serve as an important source of insight into the neuroanatomy of compulsivity and have implications for targets of DBS. For this purpose, we have reviewed all published case reports of patients with acquired or resolved obsessive-compulsive symptoms after brain lesions. We found a total of 37 case reports describing 71 patients with acquired and 6 with resolved obsessive-compulsive symptoms as a result of hemorrhaging, infarctions or removal of tumors. Behavioral symptoms following brain lesions consisted of typical obsessive-compulsive symptoms, but also symptoms within the compulsivity spectrum. These data suggests that lesions in the cortico-striato-thalamic circuit, parietal and temporal cortex, cerebellum and brainstem may induce compulsivity. Moreover, the resolution of obsessive-compulsive symptoms has been reported following lesions in the putamen, internal capsule and fronto-parietal lobe. These case reports provide strong evidence supporting the rationale for DBS in the ventral striatum and internal capsule for treatment of compulsivity and reveal the putamen and fronto-parietal cortex as promising new targets.

Deep brain stimulation in obsessive-compulsive disorder: neurocircuitry and clinical experience

The last decade has seen a significant rise in interest in the use of deep brain stimulation (DBS) for the management of obsessive-compulsive disorder (OCD), one of psychiatry's most challenging conditions. The prominent role of both thought (obsessions) and motor (compulsions) dysfunction in OCD place the condition at the border between the neurological and the psychiatric. This is supported by a growing body of literature that implicates structures in decision-making, reward, and action-selection circuits in the disorder. Here, we provide an overview of the neurocircuitry of OCD while reviewing the DBS literature to date for the condition. Results of DBS trials in treatment- resistant OCD have been remarkably similar, with clinical response rates in the range of 40-60%, despite the use of a diverse range of targets. These results imply that a common underlying circuit is being modulated, and moreover that there is room for improvement, and debate, in the development of an evidence-driven DBS treatment for this chronic, debilitating illness.

Avoidance of swallowing saliva: a symptom related to aberrant basal ganglia functions?

We report two patients with avoidance of swallowing saliva despite intact swallowing functions. One, with mild, de novo Parkinson's disease, had a fear that his saliva was contaminated and would harm him. The other, with a history of CNS germinoma in remission for 3 years following chemotherapy, expectorated because his saliva was distasteful and disgusting. He had a lesion involving the left pallidum. Both appeared obsessed with the idea of saliva contamination and both expectorated compulsively, presenting obsessive-compulsive disorder (OCD) symptoms. OCD-like behavior may be induced in association with pathological conditions in which aberrant basal ganglia functions are present.

Reduction of N-acetylaspartate in the medial prefrontal cortex correlated with symptom severity in obsessive-compulsive disorder: meta-analyses of (1)H-MRS studies

Structural and functional neuroimaging findings suggest that disturbance of the cortico-striato-thalamo-cortical (CSTC) circuits may underlie obsessive-compulsive disorder (OCD). However, some studies with (1)H-magnetic resonance spectroscopy ((1)H-MRS) reported altered level of N-acetylaspartate (NAA), they yielded inconsistency in direction and location of abnormality within CSTC circuits. We conducted a comprehensive literature search and a meta-analysis of (1)H-MRS studies in OCD. Seventeen met the inclusion criteria for a meta-analysis. Data were separated by frontal cortex region: medial prefrontal cortex (mPFC), dorsolateral prefrontal cortex, orbitofrontal cortex, basal ganglia and thalamus. The mean and s.d. of the NAA measure were calculated for each region. A random effects model integrating 16 separate datasets with 225 OCD patients and 233 healthy comparison subjects demonstrated that OCD patients exhibit decreased NAA levels in the frontal cortex (P=0.025), but no significant changes in the basal ganglia (P=0.770) or thalamus (P=0.466). Sensitivity analysis in an anatomically specified subgroup consisting of datasets examining the mPFC demonstrated marginally significant reduction of NAA (P=0.061). Meta-regression revealed that NAA reduction in the mPFC was positively correlated with symptom severity measured by Yale-Brown Obsessive Compulsive Scale (P=0.011). The specific reduction of NAA in the mPFC and significant relationship between neurochemical alteration in the mPFC and symptom severity indicate that the mPFC is one of the brain regions that directly related to abnormal behavior in the pathophysiology of OCD. The current meta-analysis indicates that cortices and sub-cortices contribute in different ways to the etiology of OCD.