Neurobiology of tourette syndrome: current status and need for further investigation

Activation of RHO-1 in cholinergic motor neurons competes with dopamine signalling to control locomotion

The small GTPase RhoA plays a crucial role in the regulation of neuronal signalling to generate behaviour. In the developing nervous system RhoA is known to regulate the actin cytoskeleton, however the effectors of RhoA-signalling in adult neurons remain largely unidentified. We have previously shown that activation of the RhoA ortholog (RHO-1) in C. elegans cholinergic motor neurons triggers hyperactivity of these neurons and loopy locomotion with exaggerated body bends. This is achieved in part through increased diacylglycerol (DAG) levels and the recruitment of the synaptic vesicle protein UNC-13 to synaptic release sites, however other pathways remain to be identified. Dopamine, which is negatively regulated by the dopamine re-uptake transporter (DAT), has a central role in modulating locomotion in both humans and C. elegans. In this study we identify a new pathway in which RHO-1 regulates locomotory behaviour by repressing dopamine signalling, via DAT-1, linking these two pathways together. We observed an upregulation of dat-1 expression when RHO-1 is activated and show that loss of DAT-1 inhibits the loopy locomotion phenotype caused by RHO-1 activation. Reducing dopamine signalling in dat-1 mutants through mutations in genes involved in dopamine synthesis or in the dopamine receptor DOP-1 restores the ability of RHO-1 to trigger loopy locomotion in dat-1 mutants. Taken together, we show that negative regulation of dopamine signalling via DAT-1 is necessary for the neuronal RHO-1 pathway to regulate locomotion.

The Role of Nerve Growth Factor (NGF) and Glial Cell Line-Derived Neurotrophic Factor (GDNF) in Tic Disorders

Objectives:

Tic disorders are associated with neurodevelopmental origin, changes in dopaminergic neurons, and the formation of immunoreactivity, it is thought that neurotrophic factors may be crucial in the emergence of tic disorders. In this study, we targeted to explore role of neurotrophic factors in tic disorders. The aim of this study was to investigate serum Glial Cell Line-Derived Neurotrophic Factor (GDNF) and Nerve Growth Factor (NGF) levels in patients with tic disorder and healthy controls.

Methods:

Thirty-four children, constituted the case group, were diagnosed with tic disorder. The control group included 34 healthy children. Development and Well-Being Assessment (DAWBA) (structured interview) and Yale Global Tic Severity Rating Scale (YGTSRS) was applied to the patients. NGF and GDNF levels were measured with ELISA kit.

Results:

In case group, serum NGF and GDNF levels were found to be significantly higher in females than males (p = 0.042, p = 0.031). It was determined that serum NGF and GDNF levels were correlated with each other (r = 0.803, p <0.001) and there were no correlations between other parameters. There was no significant difference in NGF and GDNF in patients with tic disorder, compared to healthy controls.

Conclusions:

The absence of this relationship does not exclude the hypothesis that neurotrophic factors may play a role in the etiopathogenesis of tic disorders.

Optogenetic Stimulation of GABAergic Neurons in the Globus Pallidus Produces Hyperkinesia

The globus pallidus (GP) is emerging as a critical locus of basal ganglia control of motor activity, but the exact role of GABAergic GP neurons remain to be defined. By targeted expression of channelrhodopsin 2 (ChR2) in GABAergic neurons using the VGAT-ChR2-EYFP transgenic mice, we showed that optogenetic stimulation of GABAergic neurons in the right GP produced hyperkinesia. Optogenetic stimulation of GABAergic GP neurons increased c-Fos-positive cells in GP, M1 cortex, and caudate-putamen (CPu), and decreased c-Fos-positive cells in entopeduncular nucleus (EPN), compared to the contralateral hemisphere. In agreement with the canonical basal ganglia model. Furthermore, we delivered AAV-CaMKIIα-ChR2-mCherry virus to the excitatory neurons of the subthalamic nucleus (STN) and selectively stimulated glutamatergic afferent fibers from the STN onto the GP. This optogenetic stimulation produced abnormal movements, similar to the behaviors that observed in the VGAT-ChR2-EYFP transgenic mice. Meanwhile, we found that the c-Fos expression pattern in the GP, M1, STN, EPN, and CPu produced by optogenetic activation of glutamatergic afferent fibers from the STN in GP was similar to the c-Fos expression pattern in the VGAT-ChR2-EYFP transgenic mice. Taken together, our results suggest that excess GP GABAergic neurons activity could be the neural substrate of abnormal involuntary movements in hyperkinetic movement disorders. The neural circuitry underlying the abnormal involuntary movements is associated with excessive GP, M1, CPu activity, and reduced EPN activity. Inhibition of GP GABAergic neurons represents new treatment targets for hyperkinetic movement disorder.

Olfactory functioning in adults with Tourette syndrome

Tourette syndrome is a chronic tic disorder characterized by motor and vocal tics. Comorbidities such as attention deficit hyperactivity disorder and obsessive compulsive disorder can be found. The overlap between neuroanatomical regions and neurotransmitter systems in the olfactory system and the pathophysiology of Tourette syndrome let us hypothesize altered olfactory performance in Tourette syndrome. The main objective of this study was to systematically assess olfactory functioning in subjects with Tourette syndrome and to compare it to healthy controls. We assessed 28 adults with Tourette syndrome (age 33.1±9.4 years, disease duration 23.7±9.7 years) and 28 healthy controls (age 32.9±9.0 years) matched in regard to age, sex, education and smoking habits. The “Sniffin Sticks” test battery was applied to assess odor threshold, discrimination, and identification. Additionally, the combined score of the odor threshold test, the odor discrimination test and the odor identification test of the “Sniffin Sticks” test battery was calculated. Although it was not the primary aim of this study, we assessed whether tics and comorbidity could contribute to olfactory alterations in adults with Tourette syndrome. Therefore, clinical scores were used to assess severity of tics and co-morbidity such as attention deficit hyperactivity disorder, obsessive compulsive disorder, anxiety and depression in subjects with Tourette syndrome. Pathology of the nasal cavities was excluded with rhinoendoscopy. Independent sample t-tests were applied to compare performance in olfactory tests. In the case of statistically significant differences (critical p-value: 0.05), multiple linear regression analysis was carried out to explore whether tic severity, social impairment, co-morbidity or medical treatment had an impact on the differences found. Descriptive values are reported as mean ± standard deviation. Tourette syndrome subjects showed lower combined scores (Tourette syndrome subjects 31.9 ± 5.1 versus healthy controls 35.0 ± 3.1; p = 0.007), odor identification scores (Tourette syndrome subjects 12.4 ± 2.0 versus healthy controls 13.7 ± 1.4; p = 0.008) and odor discrimination scores (Tourette syndrome subjects 12.1 ± 2.1 versus healthy controls 13.2 ± 1.6; p = 0.041) in comparison to healthy subjects, while there was no difference in odor threshold (Tourette syndrome subjects 7.3 ± 2.7 versus healthy controls 8.1 ± 2.2; p = 0.22). Seven out of 28 Tourette syndrome subjects (25%) scored in the range of the age- and sex-dependent combined score for hyposmia, while two of 28 healthy controls (7%) had a similar low combined score. None of the participants were found to have functional anosmia. Multiple linear regression analyses suggest that social impairment may a predictor for low combined score and odor identification score in Tourette syndrome subjects (p = 0.003). Compared to healthy controls, altered olfaction in adults with Tourette syndrome was found in this study. Normal odor threshold level but lower scores at tasks involving supra-threshold odor concentrations point towards a central-nervous alteration in the processing of olfactory information in Tourette syndrome.

Seroprevalance Anti-Toxoplasma gondii antibodies in children and adolescents with tourette syndrome/chronic motor or vocal tic disorder: A case-control study

Toxoplasma gondii infection may be associated with psychiatric disorders due to its neurological effects. The purpose of this study was to investigate the relation between tic disorders in children and adolescents and Anti-Toxoplasma IgG. 43 children diagnosed with Tourette's syndrome(TS) and 87 with chronic motor or vocal tic disorder(CMVTD), and 130 healthy volunteers, all aged 7-18, were enrolled. Anti-Toxoplasma IgG antibody levels obtained from blood specimens were investigated. Toxoplasma IgG positivity was determined in 16(37.2%) of the patients with TS, in 27(31%) of those with CMVTD and in 12(9.2%) members of the control group. Anti-Toxoplasma gondii antibody positivity was 5.827-fold higher in subjects with TS and 4.425-fold higher in subjects with CMVTD compared to the control group. Correlation was determined between a diagnosis of TS or CMVTD and Anti-Toxoplasma gondii antibodies. We think that it will be useful for the neuropsychiatric process associated with Anti-Toxoplasma gondii antibodies to be clarified.

GABA and glutamate in children with Tourette syndrome: A 1H MR spectroscopy study at 7T

Tourette syndrome (TS) is characterized by presence of chronic, fluctuating motor and phonic tics. The underlying neurobiological basis for these movements is hypothesized to involve cortical-striatal-thalamo-cortical (CSTC) pathways. Two major neurotransmitters within these circuits are γ-aminobutyric acid (GABA) and glutamate. Seventy-five participants (32 with TS, 43 controls) ages 5-12 years completed ¹H MRS at 7T. GABA and glutamate were measured in dorsolateral prefrontal cortex (DLPFC), ventromedial prefrontal cortex (VMPFC), premotor cortex (PMC), and striatum, and metabolites quantified using LCModel. Participants also completed neuropsychological assessment emphasizing inhibitory control. Scans were well tolerated by participants. Across ROIs combined, glutamate was significantly higher in the TS group, compared to controls, with no significant group differences in GABA observed. ROI analyses revealed significantly increased PMC glutamate in the TS group. Among children with TS, increased PMC glutamate was associated with improved selective motor inhibition; however, no significant associations were identified between levels of glutamate or GABA and tic severity. The dopaminergic system has long been considered to have a dominant role in TS. Accumulating evidence, however, suggests involvement of other neurotransmitter systems. Data obtained using ¹H MRS at 7T supports alteration of glutamate within habitual behavior-related CSTC pathways of children with TS.

Tourette syndrome: a disorder of the social decision-making network

Tourette syndrome is a common neurodevelopmental disorder defined by characteristic involuntary movements, tics, with both motor and phonic components. Tourette syndrome is usually conceptualized as a basal ganglia disorder, with an emphasis on striatal dysfunction. While considerable evidence is consistent with these concepts, imaging data suggest diffuse functional and structural abnormalities in Tourette syndrome brain. Tourette syndrome exhibits features that are difficult to explain solely based on basal ganglia circuit dysfunctions. These features include the natural history of tic expression, with typical onset of tics around ages 5 to 7 years and exacerbation during the peri-pubertal years, marked sex disparity with higher male prevalence, and the characteristic distribution of tics. The latter are usually repetitive, somewhat stereotyped involuntary eye, facial and head movements, and phonations. A major functional role of eye, face, and head movements is social signalling. Prior work in social neuroscience identified a phylogenetically conserved network of sexually dimorphic subcortical nuclei, the Social Behaviour Network, mediating many social behaviours. Social behaviour network function is modulated developmentally by gonadal steroids and social behaviour network outputs are stereotyped sex and species specific behaviours. In 2011 O'Connell and Hofmann proposed that the social behaviour network interdigitates with the basal ganglia to form a greater network, the social decision-making network. The social decision-making network may have two functionally complementary limbs: the basal ganglia component responsible for evaluation of socially relevant stimuli and actions with the social behaviour network component responsible for the performance of social acts. Social decision-making network dysfunction can explain major features of the neurobiology of Tourette syndrome. Tourette syndrome may be a disorder of social communication resulting from developmental abnormalities at several levels of the social decision-making network. The social decision-making network dysfunction hypothesis suggests new avenues for research in Tourette syndrome and new potential therapeutic targets.

Non-invasive modulation reduces repetitive behavior in a rat model through the sensorimotor cortico-striatal circuit

Involuntary movements as seen in repetitive disorders such as Tourette Syndrome (TS) results from cortical hyperexcitability that arise due to striato-thalamo-cortical circuit (STC) imbalance. Transcranial direct current stimulation (tDCS) is a stimulation procedure that changes cortical excitability, yet its relevance in repetitive disorders such as TS remains largely unexplored. Here, we employed the dopamine transporter-overexpressing (DAT-tg) rat model to investigate behavioral and neurobiological effects of frontal tDCS. The outcome of tDCS was pathology dependent, as anodal tDCS decreased repetitive behavior in the DAT-tg rats yet increased it in wild-type (wt) rats. Extensive deep brain stimulation (DBS) application and computational modeling assigned the response in DAT-tg rats to the sensorimotor pathway. Neurobiological assessment revealed cortical activity changes and increase in striatal inhibitory properties in the DAT-tg rats. Our findings show that tDCS reduces repetitive behavior in the DAT-tg rat through modulation of the sensorimotor STC circuit. This sets the stage for further investigating the usage of tDCS in repetitive disorders such as TS.

Investigation of previously implicated genetic variants in chronic tic disorders: a transmission disequilibrium test approach

Genetic studies in Tourette syndrome (TS) are characterized by scattered and poorly replicated findings. We aimed to replicate findings from candidate gene and genome-wide association studies (GWAS). Our cohort included 465 probands with chronic tic disorder (93% TS) and both parents from 412 families (some probands were siblings). We assessed 75 single nucleotide polymorphisms (SNPs) in 465 parent-child trios; 117 additional SNPs in 211 trios; and 4 additional SNPs in 254 trios. We performed SNP and gene-based transmission disequilibrium tests and compared nominally significant SNP results with those from a large independent case-control cohort. After quality control 71 SNPs were available in 371 trios; 112 SNPs in 179 trios; and 3 SNPs in 192 trios. 17 were candidate SNPs implicated in TS and 2 were implicated in obsessive-compulsive disorder (OCD) or autism spectrum disorder (ASD); 142 were tagging SNPs from eight monoamine neurotransmitter-related genes (including dopamine and serotonin); 10 were top SNPs from TS GWAS; and 13 top SNPs from attention-deficit/hyperactivity disorder, OCD, or ASD GWAS. None of the SNPs or genes reached significance after adjustment for multiple testing. We observed nominal significance for the candidate SNPs rs3744161 (TBCD) and rs4565946 (TPH2) and for five tagging SNPs; none of these showed significance in the independent cohort. Also, SLC1A1 in our gene-based analysis and two TS GWAS SNPs showed nominal significance, rs11603305 (intergenic) and rs621942 (PICALM). We found no convincing support for previously implicated genetic polymorphisms. Targeted re-sequencing should fully appreciate the relevance of candidate genes.

Jian-Pi-Zhi-Dong-Decoction regulates the expression of glutamate transporters to attenuate glutamate excitotoxicity and exerts anti-tics effects in Tourette syndrome model rats

PURPOSE

This study explored whether Jian-Pi-Zhi-Dong-Decoction (JPZDD) could regulate the metabolism of glutamate (GLU) and its transporters in the striatum to exert anti-tics effects in Tourette syndrome (TS) rats.

MATERIALS AND METHODS

We randomly assigned 56 Sprague Dawley rats into four groups, each with 14 rats: control, model, tiapride (Tia), and JPZDD. TS groups (model, Tia, and JPZDD) received intraperitoneal injection of 3,3'-iminodipropionitrile for 7 days to establish TS model. Thereafter, rats in the four groups were treated differently once a day for 6 weeks. Behavioral evaluation was performed each week by using stereotypy recording and autonomic activity test. The level of GLU in the striatum was examined by high-performance liquid chromatography. Expression of EAAT1 and VGLUT1 were measured by quantitative real-time PCR (qRT-PCR) and laser scanning confocal microscope.

RESULTS

Compared with the model group, the stereotypy score and autonomic activity were decreased in Tia and JPZDD groups. Notably, the model group had increased concentration of GLU, which decreased after JPZDD and Tia treatments. In the model group, EAAT1 and glial cells were highly co-expressed and the relative fluorescence intensity (FI) of EAAT1 was significantly lower than that in the control group. Treatment with JPZDD and Tia increased the relative FI of EAAT1. The mRNA level of EAAT1 decreased in the model group compared to that in the control group, although it was significantly elevated following JPZDD or Tia treatment. In the model group, there was low co-expression of VGLUT1 and axon cells and the FI of VGLUT1 was remarkably increased relative to that in the control group and reduced following treatment with JPZDD and Tia. A similar trend was observed in the mRNA and protein expression of VGLUT1, although it was not statistically significant.

CONCLUSION

The mechanism by which JPZDD alleviated behavioral dysfunction of TS rats may be associated with maintaining normal GLU transport by upregulating EAAT1 and down-regulating VGLUT1 in the striatum.

The Roles of Phasic and Tonic Dopamine in Tic Learning and Expression

Tourette syndrome (TS) prominently involves dopaminergic disturbances, but the precise nature of those disturbances has remained elusive. A substantial body of empirical work and recent computational models have characterized the specific roles of phasic and tonic dopamine (DA) in action learning and selection, respectively. Using insights from this work and models, we suggest that TS involves increases in both phasic and tonic DA, which produce increased propensities for tic learning and expression, respectively. We review the evidence from reinforcement-learning and habit-learning studies in TS, which supports the idea that TS involves increased phasic DA responses; we also review the evidence that tics engage the habit-learning circuitry. On the basis of these findings, we suggest that tics are exaggerated, maladaptive, and persistent motor habits reinforced by aberrant, increased phasic DA responses. Increased tonic DA amplifies the tendency to execute learned tics and also provides a fertile ground of motor hyperactivity for tic learning. We review evidence suggesting that antipsychotics may counter both the increased propensity for tic expression, by increasing excitability in the indirect pathway, and the increased propensity for tic learning, by shifting plasticity in the indirect pathway toward long-term potentiation (and possibly also through more complex mechanisms). Finally, we review evidence suggesting that low doses of DA agonists that effectively treat TS decrease both phasic and tonic DA, thereby also reducing the propensity for both tic learning and tic expression, respectively.

Altered topology of structural brain networks in patients with Gilles de la Tourette syndrome

Gilles de la Tourette syndrome is a neurodevelopmental disorder characterized by tics. Abnormal neuronal circuits in a wide-spread structural and functional network involved in planning, execution and control of motor functions are thought to represent the underlying pathology. We therefore studied changes of structural brain networks in 13 adult GTS patients reconstructed by diffusion tensor imaging and probabilistic tractography. Structural connectivity and network topology were characterized by graph theoretical measures and compared to 13 age-matched controls. In GTS patients, significantly reduced connectivity was detected in right hemispheric networks. These were furthermore characterized by significantly reduced local graph parameters (local clustering, efficiency and strength) indicating decreased structural segregation of local subnetworks. Contrasting these results, whole brain and right hemispheric networks of GTS patients showed significantly increased normalized global efficiency indicating an overall increase of structural integration among distributed areas. Higher global efficiency was associated with tic severity (R = 0.63, p = 0.022) suggesting the clinical relevance of altered network topology. Our findings reflect an imbalance between structural integration and segregation in right hemispheric structural connectome of patients with GTS. These changes might be related to an underlying pathology of impaired neuronal development, but could also indicate potential adaptive plasticity.

The colorful spectrum of Tourette syndrome and its medical, surgical and behavioral therapies

Tourette syndrome (TS) is a common neuropsychiatric disorder, more common in males than females, with onset before age 18. TS is characterized by multiple motor tics and one or more vocal/phonic tics, persisting for more than a year. Tics are unvoluntary, abrupt, rapid, repetitive, but non-rhythmic movements or sounds (vocalizations). They are preceded by an inner urge. Tics can be temporarily suppressed, but this leads to a powerful re-emergence. The performance of tics results in immediate but transient relief. Motor and vocal tics are classified as simple or complex. Tics emerge many times during the day and display spontaneous fluctuations in frequency, type, severity and complexity. Tics improve during concentration, worsen during relaxation or when under stress and occasionally are persistent in sleep. Psychiatric comorbidities such as attention deficit hyperactivity disorder (ADHD), obsessive compulsive disorder (OCD) and others frequently are present. Patients, families and teachers benefit from receiving instruction regarding the character of TS and its specific symptoms and from receiving counseling. Pharmacological treatment is not always necessary. Atypical antipsychotics (e.g. risperidone, ziprasidone, olanzapine, aripiprazole) are often the first-line treatment; typical antipsychotics (e.g. haloperidol, pimozide, fluphenazine), benzodiazepines (clonazepam) and tetrabenazine are employed less frequently. Alpha adrenergic agonists (clonidine, guanfacine), the selective noradrenaline re-uptake inhibitor, atomoxetine, and the amphetamine-like stimulant, methylphenidate, are useful in patients with tics and ADHD; selective serotonin re-uptake inhibitors can be useful in individuals with tics and OCD. Botulinum toxin can be effective in focal tics. In severe, treatment-resistant TS, deep brain stimulation may be beneficial.

Behavioral and stereological characterization of Hdc KO mice: Relation to Tourette syndrome

A premature termination codon in the human histidine decarboxylase (Hdc) gene has been identified in a family suffering from Guilles de la Tourette syndrome (GTS). In the current study we investigated if mice lacking the histamine producing enzyme HDC share the morphological and cytological phenotype with GTS patients by using magnetic resonance (MRI) and diffusion tensor imaging (DTI), unbiased stereology and immunohistochemistry. Behavior of Hdc knock-out (Hdc KO) mice was assessed in an open field test. The results of stereological, volumetric and DTI analysis measurements showed no significant differences between control and Hdc KO mice. The numbers and distribution of GABAergic parvalbumin or nitric oxide-expressing and cholinergic interneurons were normal in Hdc KO mice. Cortical morphology and layering in adult Hdc KO mice were also preserved. In open field test Hdc KO mice showed impaired exploratory activity and habituation when introduced to novel environment. Our results indicate that Hdc deficiency in mice does not disturb the development of striatal and cortical interneurons and does not lead to the morphological and cytological phenotypes characterized by humans with GTS. Nevertheless, histamine deficiency leads to behavioral alterations probably due to neurotransmitter dysbalance on the level of the striatum.

The bird dancer and the warrior king: Divergent lived experiences of Tourette syndrome in Bali

In the past two decades, ethnographic, epidemiological and interdisciplinary research has robustly established that culture is significant in determining the long-term outcomes of people with neurodevelopmental, neuropsychiatric and mood disorders. Yet these cultural factors are certainly not uniform across discrete individual experiences. Thus, in addition to illustrating meaningful differences for people with neuropsychiatric disorder between different cultures, ethnography should also help detail the variations within a culture. Different subjective experiences or outcomes are not solely due to biographical idiosyncrasies-rather, influential factors arising from the same culture can have different impacts on different people. When taking a holistic and intersectional perspective on lived experience, it is crucial to understand the interaction of these factors for people with neuropsychiatric disorders. This paper teases apart such interactions, utilizing comparative case studies of the disparate subjective experiences and illness trajectories of two Balinese people with Tourette syndrome who exhibit similar symptoms. Based on longitudinal person-centered ethnography integrating clinical, psychological, and visual anthropology, this intersectional approach goes beyond symptom interpretation and treatment modalities to identify gendered embodiment and marital practices as influenced by caste to be significant determinants in subjective experience and long-term outcome.

Disrupted topological organization of structural networks revealed by probabilistic diffusion tractography in Tourette syndrome children

Tourette syndrome (TS) is a childhood-onset neurobehavioral disorder. Although previous TS studies revealed structural abnormalities in distinct corticobasal ganglia circuits, the topological alterations of the whole-brain white matter (WM) structural networks remain poorly understood. Here, we used diffusion MRI probabilistic tractography and graph theoretical analysis to investigate the topological organization of WM networks in 44 drug-naive TS children and 41 age- and gender-matched healthy children. The WM networks were constructed by estimating inter-regional connectivity probability and the topological properties were characterized using graph theory. We found that both TS and control groups showed an efficient small-world organization in WM networks. However, compared to controls, TS children exhibited decreased global and local efficiency, increased shortest path length and small worldness, indicating a disrupted balance between local specialization and global integration in structural networks. Although both TS and control groups showed highly similar hub distributions, TS children exhibited significant decreased nodal efficiency, mainly distributed in the default mode, language, visual, and sensorimotor systems. Furthermore, two separate networks showing significantly decreased connectivity in TS group were identified using network-based statistical (NBS) analysis, primarily composed of the parieto-occipital cortex, precuneus, and paracentral lobule. Importantly, we combined support vector machine and multiple kernel learning frameworks to fuse multiple levels of network topological features for classification of individuals, achieving high accuracy of 86.47%. Together, our study revealed the disrupted topological organization of structural networks related to pathophysiology of TS, and the discriminative topological features for classification are potential quantitative neuroimaging biomarkers for clinical TS diagnosis. Hum Brain Mapp 38:3988-4008, 2017. © 2017 Wiley Periodicals, Inc.

Habituation is altered in neuropsychiatric disorders-A comprehensive review with recommendations for experimental design and analysis

Abnormalities in the simplest form of learning, habituation, have been reported in a variety of neuropsychiatric disorders as etiologically diverse as Autism Spectrum Disorder, Fragile X syndrome, Schizophrenia, Parkinson's Disease, Huntington's Disease, Attention Deficit Hyperactivity Disorder, Tourette's Syndrome, and Migraine. Here we provide the first comprehensive review of what is known about alterations in this form of non-associative learning in each disorder. Across several disorders, abnormal habituation is predictive of symptom severity, highlighting the clinical significance of habituation and its importance to normal cognitive function. Abnormal habituation is discussed within the greater framework of learning theory and how it may relate to disease phenotype either as a cause, symptom, or therapy. Important considerations for the design and interpretation of habituation experiments are outlined with the hope that these will aid both clinicians and basic researchers investigating how this simple form of learning is altered in disease.

The What, the When, and the Whether of Intentional Action in the Brain: A Meta-Analytical Review

In their attempt to define discrete subcomponents of intentionality, Brass and Haggard (2008) proposed their What, When, and Whether model (www-model) which postulates that the content, the timing and the possibility of generating an action can be partially independent both at the cognitive level and at the level of their neural implementation. The original proposal was based on a limited number of studies, which were reviewed with a discursive approach. To assess whether the model stands in front of the more recently published data, we performed a systematic review of the literature with a meta-analytic method based on a hierarchical clustering (HC) algorithm. We identified 15 PET/fMRI studies well-suited for this quest. HC revealed the existence of a rostro-caudal gradient within the medial prefrontal cortex, with the more anterior regions (the anterior cingulum) involved in more abstract decisions of whether to execute an action and the more posterior ones (the middle cingulum or the SMA) recruited in specifying the content and the timing components of actions. However, in contrast with the original www-model, this dissociation involves also brain regions well outside the median wall of the frontal lobe, in a component specific manner: the supramarginal gyrus for the what component, the pallidum and the thalamus for the when component, the putamen and the insula for the whether component. We then calculated co-activation maps on the three component-specific www clusters of the medial wall of the frontal/limbic lobe: to this end, we used the activation likelihood approach that we applied on the imaging studies on action contained in the BrainMap.org database. This analysis confirmed the main findings of the HC analyses. However, the BrainMap.org data analyses also showed that the aforementioned segregations are generated by paradigms in which subjects act in response to conditional stimuli rather than while driven by their own intentions. We conclude that the available data confirm that the neural underpinnings of intentionality can be fractionated in discrete components that are partially independent. We also suggest that intentionality manifests itself in discrete components through the boosting of general purpose action-related regions specialized for different aspects of action selection and inhibition.

Combining Disrupted and Discriminative Topological Properties of Functional Connectivity Networks as Neuroimaging Biomarkers for Accurate Diagnosis of Early Tourette Syndrome Children

Tourette syndrome (TS) is a childhood-onset neurological disorder. To date, accurate TS diagnosis remains challenging due to its varied clinical expressions and dependency on qualitative description of symptoms. Therefore, identifying accurate and objective neuroimaging biomarkers may help improve early TS diagnosis. As resting-state functional MRI (rs-fMRI) has been demonstrated as a promising neuroimaging tool for TS diagnosis, previous rs-fMRI studies on TS revealed functional connectivity (FC) changes in a few local brain networks or circuits. However, no study explored the disrupted topological organization of whole-brain FC networks in TS children. Meanwhile, very few studies have examined brain functional networks using machine-learning methods for diagnostics. In this study, we construct individual whole-brain, ROI-level FC networks for 29 drug-naive TS children and 37 healthy children. Then, we use graph theory analysis to investigate the topological disruptions between groups. The identified disrupted regions in FC networks not only involved the sensorimotor association regions but also the visual, default-mode and language areas, all highly related to TS. Furthermore, we propose a novel classification framework based on similarity network fusion (SNF) algorithm, to both diagnose an individual subject and explore the discriminative power of FC network topological properties in distinguishing between TS children and controls. We achieved a high accuracy of 88.79%, and the involved discriminative regions for classification were also highly related to TS. Together, both the disrupted topological properties between groups and the discriminative topological features for classification may be considered as comprehensive and helpful neuroimaging biomarkers for assisting the clinical TS diagnosis.

Heritability of tic disorders: a twin-family study

BACKGROUND

Genetic-epidemiological studies that estimate the contributions of genetic factors to variation in tic symptoms are scarce. We estimated the extent to which genetic and environmental influences contribute to tics, employing various phenotypic definitions ranging between mild and severe symptomatology, in a large population-based adult twin-family sample.

METHOD

In an extended twin-family design, we analysed lifetime tic data reported by adult mono- and dizygotic twins (n = 8323) and their family members (n = 7164; parents and siblings) from 7311 families in the Netherlands Twin Register. We measured tics by the abbreviated version of the Schedule for Tourette and Other Behavioral Syndromes. Heritability was estimated by genetic structural equation modeling for four tic disorder definitions: three dichotomous and one trichotomous phenotype, characterized by increasingly strictly defined criteria.

RESULTS

Prevalence rates of the different tic disorders in our sample varied between 0.3 and 4.5% depending on tic disorder definition. Tic frequencies decreased with increasing age. Heritability estimates varied between 0.25 and 0.37, depending on phenotypic definitions. None of the phenotypes showed evidence of assortative mating, effects of shared environment or non-additive genetic effects.

CONCLUSIONS

Heritabilities of mild and severe tic phenotypes were estimated to be moderate. Overlapping confidence intervals of the heritability estimates suggest overlapping genetic liabilities between the various tic phenotypes. The most lenient phenotype (defined only by tic characteristics, excluding criteria B, C and D of DSM-IV) rendered sufficiently reliable heritability estimates. These findings have implications in phenotypic definitions for future genetic studies.

Dysfunctions of the basal ganglia-cerebellar-thalamo-cortical system produce motor tics in Tourette syndrome

Motor tics are a cardinal feature of Tourette syndrome and are traditionally associated with an excess of striatal dopamine in the basal ganglia. Recent evidence increasingly supports a more articulated view where cerebellum and cortex, working closely in concert with basal ganglia, are also involved in tic production. Building on such evidence, this article proposes a computational model of the basal ganglia-cerebellar-thalamo-cortical system to study how motor tics are generated in Tourette syndrome. In particular, the model: (i) reproduces the main results of recent experiments about the involvement of the basal ganglia-cerebellar-thalamo-cortical system in tic generation; (ii) suggests an explanation of the system-level mechanisms underlying motor tic production: in this respect, the model predicts that the interplay between dopaminergic signal and cortical activity contributes to triggering the tic event and that the recently discovered basal ganglia-cerebellar anatomical pathway may support the involvement of the cerebellum in tic production; (iii) furnishes predictions on the amount of tics generated when striatal dopamine increases and when the cortex is externally stimulated. These predictions could be important in identifying new brain target areas for future therapies. Finally, the model represents the first computational attempt to study the role of the recently discovered basal ganglia-cerebellar anatomical links. Studying this non-cortex-mediated basal ganglia-cerebellar interaction could radically change our perspective about how these areas interact with each other and with the cortex. Overall, the model also shows the utility of casting Tourette syndrome within a system-level perspective rather than viewing it as related to the dysfunction of a single brain area.

Tourette syndrome is a neuropsychiatric disorder characterized by vocal and motor tics. Tics represent a cardinal symptom traditionally associated with a dysfunction of the basal ganglia leading to an excess of the dopamine neurotransmitter. This view gives a restricted clinical picture and limits therapeutic approaches because it ignores the influence of altered interactions between the basal ganglia and other brain areas. In this respect, recent evidence supports a more articulated framework where cerebellum and cortex are also involved in tic production. Building on these data, we propose a computational model of the basal ganglia-cerebellar-thalamo-cortical network to investigate the specific mechanisms underlying motor tic production. The model reproduces the results of recent experiments and suggests an explanation of the system-level processes underlying tic production. Moreover, it furnishes predictions related to the amount of tics generated when there are dysfunctions in the basal ganglia-cerebellar-thalamo-cortical circuits. These predictions could be important in identifying new brain target areas for future therapies based on a system-level view of Tourette syndrome.

A Single Case of Tourette's Syndrome Treated with Traditional Chinese Medicine

The objective of this case study was to investigate the effectiveness of Chinese medicine in treating Tourette's syndrome. Tourette's syndrome is a childhood- onset disorder that is characterized by sudden, involuntary movements or tics. The participant in this study was a 33-year-old male who had been diagnosed with Tourette's syndrome at the age of 9 years. His major complaints included facial tics, shoulder shrugging, and clearing the throat. Using a combination of acupuncture, herbs, Gua-Sha, and lifestyle changes once a week for 35 treatments, all the symptoms were reduced by 70%, as reported by the patient. In this case, the results indicated that Chinese medicine was able to minimize the symptoms of Tourette's syndrome. Further investigation is needed to support this argument. Tourette's syndrome, which was first described in 1885 by a French physician named Gilles de la Tourette, is characterized by facial tics, involuntary body movements from the head to the extremities, or vocal tics, and it usually has its onset in childhood. It is a neuropsychiatric disorder. The treatment for Tourette's syndrome is based on pharmacological treatment, behavior treatment, and deep brain stimulation. Unfortunately, none of these could completely control the symptoms; furthermore, antipsychiatric drugs might cause additional side effects, such as Parkinson symptoms, tardive dyskinesia, and metabolic disturbances. Finding acupuncture and oriental medicine literature on treatment of Tourette's syndrome was difficult, especially that written in English. Some research papers that have been translated into English indicated that Chinese herbs and acupuncture could reduce the tics significantly. For example, a study by Dr Pao-Hua Lin reported the significant effects of using acupuncture and oriental medicine in treating 1000 Tourette's syndrome cases. This case was treated to further investigate the principles of Dr Lin's study.

Putting the Pieces Together in Gilles de la Tourette Syndrome: Exploring the Link Between Clinical Observations and the Biological Basis of Dysfunction

Gilles de la Tourette syndrome is a complex, idiopathic neuropsychiatric disorder whose pathophysiological mechanisms have yet to be elucidated. It is phenotypically heterogeneous and manifests more often than not with both motor and behavioral impairment, although tics are its clinical hallmark. Tics themselves present with a complex profile as they characteristically wax and wane and are often preceded by premonitory somatosensory sensations to which it is said a tic is the response. Highly comorbid with obsessive-compulsive disorder and attention deficit-hyperactivity disorder, it is purported to be an epigenetic, neurodevelopmental spectrum disorder with a complex genetic profile. It has a childhood onset, occurs disproportionately in males, and shows spontaneous symptomatic attenuation by adulthood in the majority of those afflicted. Although not fully understood, its neurobiological basis is linked to dysfunction in the cortico-basal ganglia-thalamo-cortical network. Treatment modalities for Tourette syndrome include behavioral, pharmacological and surgical interventions, but there is presently no cure for the disorder. For those severely affected, deep brain stimulation (DBS) has recently become a viable therapeutic option. A key factor to attaining optimal results from this surgery is target selection, a topic still under debate due to the complex clinical profile presented by GTS patients. Depending on its phenotypic expression and the most problematic aspect of the disorder for the individual, one of three brain regions is most commonly chosen for stimulation: the thalamus, globus pallidus, or nucleus accumbens. Neurophysiological analyses of intra- and post-operative human electrophysiological recordings from clinical DBS studies suggest a link between tic behavior and activity in both the thalamus and globus pallidus. In particular, chronic recordings from the thalamus have shown a correlation between symptomatology and (1) spectral activity in gamma band power and (2) theta/gamma cross frequency coherence. These results suggest gamma oscillations and theta/gamma cross correlation dynamics may serve as biomarkers for dysfunction. While acute and chronic recordings from human subjects undergoing DBS have provided better insight into tic genesis and the neuropathophysiological mechanisms underlying Tourette syndrome, these studies are still sparse and the field would greatly benefit from further investigations. This review reports data and discoveries of scientific and clinical relevance from a wide variety of methods and provides up-to-date information about our current understanding of the pathomechanisms underlying Tourette syndrome. It gives a comprehensive overview of the current state of knowledge and addresses open questions in the field.

The anarchic brain in action: the contribution of task-based fMRI studies to the understanding of Gilles de la Tourette syndrome

PURPOSE OF REVIEW

Gilles de la Tourette syndrome (GTS) is a frequent neurological disorder characterized by the production of tics, and frequently associated with obsessive-compulsive disorder or attention-deficit hyperactivity disorder. The aim of this article is to summarize the contribution of imaging activation techniques to the study of the syndrome.

RECENT FINDINGS

GTS has been studied with a variety of functional MRI (fMRI)/PET activation paradigms to characterize the origin of tics or their suppression, and how they compare physiologically with voluntary actions or response inhibitions. Current studies indicate overactivations of prefrontal and premotor cortices, including the supplementary motor area, and subcortical structures. Resting state functional connectivity studies complement activation studies in showing perturbed connectivity of cortico-subcortical networks. Several such findings correlate with the severity of the disease.

SUMMARY

fMRI activation techniques are contributing a system-level neurophysiological description of GTS and bridge the gap between animal models and clinical observations. fMRI clarifies brain networks involved in different aspects of GTS phenomenology with some good clinical face validity. A future generation of fMRI studies should have higher ambitions and contribute, for example, to treatment optimization including the identification of ideal targets for deep brain stimulation in drug-resistant cases; however, such goals will be achieved only through controlled large-scale cooperative studies.

Sleep, anxiety and psychiatric symptoms in children with Tourette syndrome and tic disorders

OBJECTIVE

The current study evaluated the relationship between tic, sleep disorders and specific psychiatric symptoms (anxiety, depression, obsessive compulsive symptoms).

METHODS

Assessment of 36 consecutive children and adolescents with tic disorders included: the Yale Global Tic Severity Scale (YGTSS) to assess the severity of tic symptoms; the Self-administered scale for children and adolescents (SAFA) to evaluate the psychopathological profile; a specific sleep questionnaire consisting of 45 items to assess the presence of sleep disorders. An age and sex-matched control group was used for comparisons.

RESULTS

Sleep was significantly more disturbed in patients with tic disorders than in controls. Difficulties in initiating sleep and increased motor activity during sleep were the most frequent sleep disturbances found in our sample. Patients showed also symptoms of anxiety (SAFA A), depressed mood (SAFA D) and doubt-indecision (SAFA O). Additionally, difficulties in initiating sleep resulted associated with other SAFA subscales relative to obsessive-compulsive symptoms and depression symptoms. Furthermore, anxiety symptoms (SAFA A) resulted associated with increased motor activity during sleep.

CONCLUSIONS

Findings confirm literature studies reporting high frequency of sleep problems, anxiety and other psychopathological symptoms in patients with tic disorders, and support the hypothesis that intrusive thoughts and other emotional disturbances might disrupt the sleep onset of these patients. These results suggest the importance of a thorough assessment of sleep and psychiatric disturbances in patients with tic disorders.

Investigation of a Possible Role for the Histidine Decarboxylase Gene in Tourette Syndrome in the Chinese Han Population: A Family-Based Study

Tourette syndrome (TS) is a polygenic neuropsychiatric disease. Previous studies have indicated that dysregulation in the histaminergic system may play a crucial role in disease onset. In this study, we investigated the role of the histidine decarboxylase gene (HDC) in TS susceptibility in the Chinese Han population. After genotyping 241 TS nuclear families trios, we analyzed three tag HDC single nucleotide polymorphisms (rs854150, rs854151, and rs854157) in a family-based study using the transmission disequilibrium test (TDT) and haplotype relative risk (HRR). TDT showed no over-transmission in these SNPs across the HDC region (for rs854150: χ² = 0.472, P = 0.537, OR = 1.097, 95%CI = 0.738–1.630; for rs854151: χ² = 0.043, P = 0.889, OR = 1.145, 95%CI = 0.767–1.709; for rs854157:χ² = 0.984, P = 0.367, OR = 1.020, 95%CI = 0.508–2.049). HRR also showed the same tendency (for rs854150: χ² = 0.211, P = 0.646, OR = 1.088, 95%CI = 0.759–1.559; for rs854151: χ² = 0.134, P = 0.714, OR = 0.935, 95%CI = 0.653–1.339; for rs854157:χ² = 0.841, P = 0.359, OR = 1.206, 95%CI = 0.808–1.799). Additionally, the haplotype-based haplotype relative risk showed a negative association. Although these findings indicate an unlikely association between HDC and TS in the Chinese Han population, a potential role for HDC cannot be ruled out in TS etiology. Future research should investigate this more thoroughly using different populations and larger samples.

Social disinhibition is a heritable subphenotype of tics in Tourette syndrome

OBJECTIVE

To identify heritable symptom-based subtypes of Tourette syndrome (TS).

METHODS

Forty-nine motor and phonic tics were examined in 3,494 individuals (1,191 TS probands and 2,303 first-degree relatives). Item-level exploratory factor and latent class analyses (LCA) were used to identify tic-based subtypes. Heritabilities of the subtypes were estimated, and associations with clinical characteristics were examined.

RESULTS

A 6-factor exploratory factor analysis model provided the best fit, which paralleled the somatotopic representation of the basal ganglia, distinguished simple from complex tics, and separated out socially disinhibited and compulsive tics. The 5-class LCA model best distinguished among the following groups: unaffected, simple tics, intermediate tics without social disinhibition, intermediate with social disinhibition, and high rates of all tic types. Across models, a phenotype characterized by high rates of social disinhibition emerged. This phenotype was associated with increased odds of comorbid psychiatric disorders, in particular, obsessive-compulsive disorder and attention-deficit/hyperactivity disorder, earlier age at TS onset, and increased tic severity. The heritability estimate for this phenotype based on the LCA was 0.53 (SE 0.08, p 1.7 × 10(-18)).

CONCLUSIONS

Expanding on previous modeling approaches, a series of TS-related phenotypes, including one characterized by high rates of social disinhibition, were identified. These phenotypes were highly heritable and may reflect underlying biological networks more accurately than traditional diagnoses, thus potentially aiding future genetic, imaging, and treatment studies.

All that glitters is not gold: When motor and vocal tics in a child do not match Tourette syndrome: A case report

The atypical form of Pantothenate Kinase-Associated Neurodegeneration (PKAN) tends to present at around the age of 14 years, has a heterogeneous presentation with extrapyramidal symptoms, and approximately one third of patients exhibit psychiatric problems. This paper reports the case of a patient with apparent typical symptoms of Tourette syndrome. However, the severity and poor response to treatment led to further investigation and the diagnosis of PKAN as a secondary cause of Tourettism was reached.

Inter-hemispheric Intrinsic Connectivity as a Neuromarker for the Diagnosis of Boys with Tourette Syndrome

Tourette syndrome (TS) is associated with gross morphological changes in the corpus callosum, suggesting deficits in inter-hemispheric coordination. The present study sought to identify changes in inter-hemispheric functional and anatomical connectivity in boys with "pure" TS as well as their potential value for clinical diagnosis. TS boys without comorbidity (pure TS, n = 24) were selected from a large dataset and compared to age- and education-matched controls (n = 32). Intrinsic functional connectivity (iFC) between bilateral homotopic voxels was computed and compared between groups. Abnormal iFC was found in the bilateral prefronto-striatum-midbrain networks as well as bilateral sensorimotor and temporal cortices. The iFC between the bilateral anterior cingulate cortex (ACC) was negatively correlated with symptom severity. Anatomical connectivity strengths between functionally abnormal regions were estimated by diffusion probabilistic tractography, but no significant between-group difference was found. To test the clinical applicability of these neuroimaging findings, multivariate pattern analysis was used to develop a classification model in half of the total sample. The classification model exhibited excellent classification power for discriminating TS patients from controls in the other half samples. In summary, our findings emphasize the role of inter-hemispheric communication deficits in the pathophysiology of TS and suggest that iFC is a potential quantitative neuromarker for clinical diagnosis.

Variants of Base Excision Repair Genes MUTYH , PARP1 and XRCC1 in Alzheimer's Disease Risk

BACKGROUND

Many clinical studies have shown that oxidative stress pathways and the efficiency of the oxidative DNA damage base excision repair (BER) system are associated with the pathogenesis of Alzheimer's disease (AD). Reduced BER efficiency may result from polymorphisms of BER-related genes. In the present study, we examine whether single nucleotide polymorphisms (SNPs) of BER genes are associated with increased risk of AD.

METHODS

SNP genotyping was carried out on DNA isolated from peripheral blood mononuclear cells obtained from 120 patients with AD and 110 healthy volunteers. Samples were genotyped for the presence of BER-related SNPs, i.e. XRCC1-rs1799782, rs25487; MUTYH-rs3219489, and PARP1-rs1136410.

RESULTS

We found a positive association between AD risk and the presence of G/A genotype variant of the XRCC1 rs25487 polymorphism [odds ratio (OR) = 3.762, 95% CI: 1.793-7.891]. The presence of the A/A genotype of this polymorphism reduced the risk of AD (OR = 0.485, 95% CI: 0.271-0.870). In cases of the PARP1 gene rs1136410 polymorphism, we observed that the T/C variant increases (OR = 4.159, 95% CI: 1.978-8.745) while the T/T variant reduces risk (OR = 0.240, 95% CI: 0.114-0.556) of AD.

CONCLUSIONS

We conclude that BER gene polymorphisms may play an important role in the etiology of AD. Diagnosing the presence or absence of particular genetic variants may be an important marker of AD. Further research on a larger population is needed. There is also a need to examine polymorphisms of other BER in the context of AD risk.

Effect of Jian-Pi-Zhi-Dong Decoction on striatal glutamate and γ-aminobutyric acid levels detected using microdialysis in a rat model of Tourette syndrome

BACKGROUND

Jian-Pi-Zhi-Dong Decoction (JPZDD) is a dedicated treatment of Tourette syndrome (TS). The balance of neurotransmitters in the cortico-striato-pallido-thalamo-cortical network is crucial to the occurrence of TS and related to its severity. This study evaluated the effect of JPZDD on glutamate (Glu) and γ-aminobutyric acid (GABA) and their receptors in a TS rat model.

MATERIALS AND METHODS

Rats were divided into four groups (n=12 each). TS was induced in three of the groups by injecting them with 3,3'-iminodipropionitrile for 7 consecutive days. Two model groups were treated with tiapride (Tia) or JPZDD, while the control and the remaining model group were gavaged with saline. Behavior was assessed by stereotypic score and autonomic activity. Striatal Glu and GABA contents were detected using microdialysis. Expressions of N-methyl-D-aspartate receptor 1 and GABAA receptor (GABAAR) were observed using Western blot and real-time polymerase chain reaction.

RESULTS

Tia and JPZDD groups had decreased stereotypy compared with model rats; however, the JPZDD group showed a larger decrease in stereotypy than the Tia group at a 4-week time point. In a spontaneous activity test, the total distance of the JPZDD and Tia groups was significantly decreased compared with the model group. The Glu levels of the model group were higher than the control group and decreased with Tia or JPZDD treatment. The GABA level was higher in the model group than the control group. Expressions of GABAAR protein in the model group were higher than in the control group. Treatment with Tia or JPZDD reduced the expression of GABAAR protein. In the case of the mRNA expression, only Tia reduced the expression of N-methyl-D-aspartate receptor 1, compared with the model group.

CONCLUSION

JPZDD could alleviate impairments in behavior and dysfunctional signaling by downregulating GABAAR in the striatum. We suggest that this acts to maintain the balance of Glu and GABA.

The Impact of a Cognitive-Behavioral Therapy on Event-Related Potentials in Patients with Tic Disorders or Body-Focused Repetitive Behaviors

CONTEXT

Tic disorders (TD) are characterized by the presence of non-voluntary contractions of functionally related groups of skeletal muscles in one or multiple body parts. Patients with body-focused repetitive behaviors (BFRB) present frequent and repetitive behaviors, such as nail biting or hair pulling. TD and BFRB can be treated with a cognitive-behavioral therapy (CBT) that regulates the excessive amount of sensorimotor activation and muscular tension. Our CBT, which is called the cognitive-psychophysiological (CoPs) model, targets motor execution and inhibition, and it was reported to modify brain activity in TD. However, psychophysiological effects of therapy are still poorly understood in TD and BFRB patients. Our goals were to compare the event-related potentials (ERP) of TD and BFRB patients to control participants and to investigate the effects of the CoPs therapy on the P200, N200, and P300 components during a motor and a non-motor oddball task.

METHOD

Event-related potential components were compared in 26 TD patients, 27 BFRB patients, and 27 control participants. ERP were obtained from 63 EEG electrodes during two oddball tasks. In the non-motor task, participants had to count rare stimuli. In the motor task, participants had to respond with a left and right button press for rare and frequent stimuli, respectively. ERP measures were recorded before and after therapy in both patient groups.

RESULTS

CoPs therapy improved symptoms similarly in both clinical groups. Before therapy, TD and BFRB patients had reduced P300 oddball effect during the non-motor task, in comparison with controls participants. An increase in the P300 oddball effect was observed posttherapy. This increase was distributed over the whole cortex in BFRB patients, but localized in the parietal area in TD patients.

DISCUSSION

These results suggest a modification of neural processes following CoPs therapy in TD and BFRB patients. CoPs therapy seems to impact patients' attentional processes and context updating capacities in working memory (i.e., P300 component). Our results are consistent with a possible role of the prefrontal cortex and corpus callosum in mediating interhemispheric interference in TD.

Functional Evaluations of Genes Disrupted in Patients with Tourette's Disorder

Tourette's disorder (TD) is a highly heritable neurodevelopmental disorder with complex genetic architecture and unclear neuropathology. Disruptions of particular genes have been identified in subsets of TD patients. However, none of the findings have been replicated, probably due to the complex and heterogeneous genetic architecture of TD that involves both common and rare variants. To understand the etiology of TD, functional analyses are required to characterize the molecular and cellular consequences caused by mutations in candidate genes. Such molecular and cellular alterations may converge into common biological pathways underlying the heterogeneous genetic etiology of TD patients. Herein, we review specific genes implicated in TD etiology, discuss the functions of these genes in the mammalian central nervous system and the corresponding behavioral anomalies exhibited in animal models, and importantly, review functional analyses that can be performed to evaluate the role(s) that the genetic disruptions might play in TD. Specifically, the functional assays include novel cell culture systems, genome editing techniques, bioinformatics approaches, transcriptomic analyses, and genetically modified animal models applied or developed to study genes associated with TD or with other neurodevelopmental and neuropsychiatric disorders. By describing methods used to study diseases with genetic architecture similar to TD, we hope to develop a systematic framework for investigating the etiology of TD and related disorders.

A proprietary herbal medicine (5-Ling Granule) for Tourette syndrome: a randomized controlled trial

BACKGROUND

Tourette syndrome (TS) is a common tic disorder in children and adolescents. There is preliminary evidence that herbal medicine may possess the potential to treat tics. The purpose of this study was to formally evaluate the efficacy and safety of 5-Ling Granule (5-LGr), a proprietary polyherbal product, for the treatment of patients with TS in comparison with tiapride and placebo.

METHODS

In this multisite, double-blind, double-dummy, randomized, placebo-controlled trial, 603 patients with TS aged 5-18 years were randomly assigned to treatment with placebo (n = 117), tiapride (n = 123, 200-400 mg/day) or 5-LGr (n = 363, 15-22.5 g/day) for 8 weeks. The primary outcome was measured using the Yale Global Tic Severity Scale (YGTSS) and its subscales, total tic Score (TTS) and tic-related impairment. Incidence of adverse events was compared among the three groups.

RESULTS

While tics of all patients were reduced over time, 5-LGr and tiapride treatment produced significantly greater improvement on the YGTSS overall scale and subscale for TTS and impairment at endpoint than the placebo. Seventy-four percentage of patients in the 5-LGr arm and 68.3% in the tiapride arm had clinical response and these rates of response were significantly higher than those on placebo (44.0%, p < .001). The incidence of overall adverse events was significantly fewer for patients on placebo and 5-LGr compared to tiapride (11.2% and 13.8% vs. 26.0%, p = .002); in particular physical tiredness, dizziness and sleep disturbance.

CONCLUSIONS

The clinical efficacy of 5-LGr is comparable to tiapride in reducing tics. Its safety profile is better than tiapride. 5-LGr can be considered a safe and effective therapy for TS (Trial registration: www.clinicaltrials.gov: NCT01501695).

Neurobiology of rodent self-grooming and its value for translational neuroscience

Self-grooming is a complex innate behaviour with an evolutionarily conserved sequencing pattern and is one of the most frequently performed behavioural activities in rodents. In this Review, we discuss the neurobiology of rodent self-grooming, and we highlight studies of rodent models of neuropsychiatric disorders--including models of autism spectrum disorder and obsessive compulsive disorder--that have assessed self-grooming phenotypes. We suggest that rodent self-grooming may be a useful measure of repetitive behaviour in such models, and therefore of value to translational psychiatry. Assessment of rodent self-grooming may also be useful for understanding the neural circuits that are involved in complex sequential patterns of action.

NMDA receptor agonists reverse impaired psychomotor and cognitive functions associated with hippocampal Hbegf-deficiency in mice

BACKGROUND

Structural and functional changes of the hippocampus are correlated with psychiatric disorders and cognitive dysfunctions. Genetic deletion of heparin-binding epidermal growth factor-like growth factor (HB-EGF), which is predominantly expressed in cortex and hippocampus, also causes similar psychiatric and cognitive dysfunctions, accompanying down-regulated NMDA receptor signaling. However, little is known of such dysfunctions in hippocampus-specific Hbegf cKO mice.

RESULTS

We successfully developed hippocampus-specific cKO mice by crossbreeding floxed Hbegf and Gng7-Cre knock-in mice, as Gng7 promoter-driven Cre is highly expressed in hippocampal neurons as well as striatal medium spiny neurons. In mice lacking hippocampus Hbegf gene, there was a decreased neurogenesis in the subgranular zone (SGZ) of the dentate gyrus as well as down-regulation of PSD-95/NMDA-receptor-NR1/NR2B subunits and related NMDA receptor signaling. Psychiatric, social-behavioral and cognitive abnormalities were also observed in hippocampal cKO mice. Interestingly, D-cycloserine and nefiracetam, positive allosteric modulators (PAMs) of NMDA receptor reversed the apparent reduction in NMDA receptor signaling and most behavioral abnormalities. Furthermore, decreased SGZ neurogenesis in hippocampal cKO mice was reversed by nefiracetam.

CONCLUSIONS

The present study demonstrates that PAMs of NMDA receptor have pharmacotherapeutic potentials to reverse down-regulated NMDA receptor signaling, neuro-socio-cognitive abnormalities and decreased neurogenesis in hippocampal cKO mice.

Behavior Therapy for Tic Disorders: An Evidenced-based Review and New Directions for Treatment Research

Behavior therapy is an evidenced-based intervention with moderate-to-large treatment effects in reducing tic symptom severity among individuals with Persistent Tic Disorders (PTDs) and Tourette's Disorder (TD). This review describes the behavioral treatment model for tics, delineates components of evidence-based behavior therapy for tics, and reviews the empirical support among randomized controlled trials for individuals with PTDs or TD. Additionally, this review discusses several challenges confronting the behavioral management of tics, highlights emerging solutions for these challenges, and outlines new directions for treatment research.

The role of GRIN2B in Tourette syndrome: Results from a transmission disequilibrium study

BACKGROUND

Previous studies have indicated that dopamine interacts with glutamatergic projection neurons and that N-methyl-d-aspartate (NMDA) receptors might be involved in the pathogenesis of Tourette syndrome (TS). In this study, we examined whether two functional polymorphisms (rs1805476 and rs1805502) in the 3'UTR of the NMDA receptor 2B subunit gene (GRIN2B) were associated with TS in Chinese Han trios.

METHODS

DNA samples collected from 261 TS nuclear families were genotyped by PCR and direct sequencing technology. Haplotype relative risk (HRR), transmission disequilibrium test (TDT) and Haplotype-based haplotype relative risk (HHRR) analyses were performed on the genotype data.

RESULTS

We found an over-transmission of the A allele in rs1805476 and the T allele in rs1805502 from parents to their affected children, using the HRR (rs1805476: HRR=0.696, χ(2)=4.161, P=0.041, 95% CI: 0.491-0.986; rs1805502: HRR=0.697, χ(2)=3.954, P=0.047, 95% CI: 0.488-0.995). There was also strong evidence for a linkage between polymorphisms and TS using the TDT (rs1805476: TDT=5.447, df=1, P=0.024; rs1805502: TDT=5.233, df=1, P=0.027).

LIMITATIONS

The sample is small and the current population is just limited to the Chinese Han population.

CONCLUSIONS

These data support the hypothesis that GRIN2B might play a major role in the pathogenesis of TS in Chinese Han trios. However, these results need to be replicated using larger datasets collected from different populations.