Mapping Gilles de la Tourette syndrome through the distress and relief associated with tic-related behaviors: an fMRI study.

Personal distress associated with tic urges or inhibition and relief associated with tic production are defining features of the personal experience in Gilles de la Tourette syndrome (GTS). These affective phenomena have not been studied using fMRI, hindering our understanding of GTS pathophysiology and possible treatments. Here, we present a novel cross-sectional fMRI study designed to map tic-related phenomenology using distress and relief as predicting variables. We adopted a mental imagery approach and dissected the brain activity associated with different phases of tic behaviors, premonitory urges, and the ensuing tic execution or inhibition: these were compared with the mental simulation of "relaxed situations" and pre-determined stereotyped motor behaviors. We then explored whether the ensuing brain patterns correlated with the distress or relief perceived for the different phases of the tasks. Patients experienced a higher level of distress during the imagery of tic-triggering scenarios and no relief during tic inhibition. On the other hand, patients experienced significant relief during tic imagery. Distress during tic-triggering scenarios and relief during tic imagery were significantly correlated. The distress perceived during urges correlated with increased activation in cortical sensorimotor areas, suggesting a motor alarm. Conversely, relief during tic execution was positively associated with the activity of a subcortical network. The activity of the putamen was associated with both distress during urges and relief during tic execution. These findings highlight the importance of assessing the affective component of tic-related phenomenology. Subcortical structures may be causally involved in the affective component of tic pathophysiology, with the putamen playing a central role in both tic urge and generation. We believe that our results can be readily translated into clinical practice for the development of personalized treatment plans tailored to each patient's unique needs.

Protocol description for a randomized controlled trial of fMRI neurofeedback for tics in adolescents with Tourette Syndrome.

This article describes the protocol for a randomized, controlled clinical trial of a neurofeedback (NF) intervention for Tourette Syndrome (TS) and chronic tic disorder. The intervention involves using functional magnetic resonance imaging (fMRI) to provide feedback regarding activity in the supplementary motor area: participants practice controlling this brain area while using the feedback as a training signal. The previous version of this NF protocol was tested in a small study (n = 21) training adolescents with TS that yielded clinically promising results. Therefore, we plan a larger trial. Here we describe the background literature that motivated this work, the design of our original neurofeedback study protocol, and adaptations of the research study protocol for the new trial. We focus on those ideas incorporated into our protocol that may be of interest to others designing and running NF studies. For example, we highlight our approach for defining an unrelated brain region to be trained in the control group that is based on identifying a region with low functional connectivity to the target area. Consistent with a desire for transparency and open science, the new protocol is described in detail here prior to conducting the trial.

Gastrodin - A potential drug used for the treatment of Tourette Syndrome.

Gastrodin (Gas) represents the major active component of Gastrodia elata, a Chinese herb. Clinically, Gas is widely used for its sedative, anticonvulsive and neuroprotective properties. This work aimed to assess Gas for its efficacy in Tourette Syndrome (TS) treatment. Twenty-four rats were randomized to the blank control (n = 6) and experimental (n = 18) groups. The experimental group was administered continuous injection of 3, 3'-iminodipropionitrile (IDPN) intraperitoneally for 7 days, and subdivided into the IDPN + NS, IDPN + Hal, and IDPN + Gas groups (n = 6). The control and IDPN + NS groups received saline intragastrically, while the IDPN + Hal and IDPN + Gas groups were administered Gas and Haloperidol, respectively, for 8 weeks. Then, micro-positron emission tomography (PET) was performed for measuring the density and brain distribution of dopamine D2 receptors (D2Rs), dopamine transporters (DATs), 5-HT2A receptors (5-HT2ARs) and 5-HT transporters (SERTs). According to stereotypical behavior experiments, IDPN significantly induced abnormal stereotypical behaviors in rats in comparison with control animals. In addition, micro-PET revealed that by reducing the amounts of D2Rs and increasing those of DATs, Gas could significantly reduce stereotypical TS-like behaviors in this rat model system. Furthermore, Gas treatment reduced the density of SERTs, which could indirectly decrease DA release. The current study demonstrated that Gas could be effective in treating TS.

Evidence for the role of the dorsal ventral lateral posterior thalamic nucleus connectivity in deep brain stimulation for Gilles de la Tourette syndrome.

Gilles de la Tourette syndrome (GTS) can manifest as debilitating, medically-refractory tics for which deep brain stimulation (DBS) of the centromedian-parafascicular complex (CM) can provide effective treatment. However, patients have reported benefit with activation of contacts dorsal to the CM and likely in the ventro-lateral thalamus (VL). At our institution, a case of a robust and durable response in a GTS patient required stimulation in the CM and more dorsally. We explore the structural connectivity of thalamic subregions associated with GTS using diffusion MRI tractography. Diffusion weighted images from 40 healthy Human Connectome Project (HCP) subjects and our GTS patient were analyzed. The VL posterior nucleus (VLp) and the CM were used as seeds for whole-brain probabilistic tractography. Leads were localized via linear registration of pre-/post-operative imaging and cross-referenced with the DBS Intrinsic Template Atlas. Tractography revealed high streamline probability from the CM and VLp to the superior frontal gyrus, rostral middle frontal gyrus, brainstem, and ventral diencephalon. Given reported variable responses to DBS along the thalamus, we segmented the VLp based on its connectivity profile. Ventral and dorsal subdivisions emerged, with streamline probability patterns differing between the dorsal VLp and CM. The CM, the most reported DBS target for GTS, and the dorsal VLp have different but seemingly complimentary connectivity profiles as evidenced by our patient who, at 1-year post-operatively, had significant therapeutic benefit. Stimulation of both regions may better target reward and motor circuits, resulting in enhanced symptom control for GTS.

Randomized, Sham-Controlled Trial of Real-Time Functional Magnetic Resonance Imaging Neurofeedback for Tics in Adolescents With Tourette Syndrome.

BACKGROUND: Activity in the supplementary motor area (SMA) has been associated with tics in Tourette syndrome (TS). The aim of this study was to test a novel intervention-real-time functional magnetic resonance imaging neurofeedback from the SMA-for reduction of tics in adolescents with TS. METHODS: Twenty-one adolescents with TS were enrolled in a double-blind, randomized, sham-controlled, crossover study involving two sessions of neurofeedback from their SMA. The primary outcome measure of tic severity was the Yale Global Tic Severity Scale administered by an independent evaluator before and after each arm. The secondary outcome was control over the SMA assessed in neuroimaging scans, in which subjects were cued to increase/decrease activity in SMA without receiving feedback. RESULTS: All 21 subjects completed both arms of the study and all assessments. Participants had significantly greater reduction of tics on the Yale Global Tic Severity Scale after real neurofeedback as compared with the sham control (p < .05). Mean Yale Global Tic Severity Scale Total Tic score decreased from 25.2 ± 4.6 at baseline to 19.9 ± 5.7 at end point in the neurofeedback condition and from 24.8 ± 8.1 to 23.3 ± 8.5 in the sham control condition. The 3.8-point difference is clinically meaningful and corresponds to an effect size of 0.59. However, there were no differences in changes on the secondary measure of control over the SMA. CONCLUSIONS: This first randomized controlled trial of real-time functional magnetic resonance imaging neurofeedback in adolescents with TS suggests that this neurofeedback intervention may be helpful for improving tic symptoms. However, no effects were found in terms of change in control over the SMA, the hypothesized mechanism of action.

Alterations in basal ganglia-cerebello-thalamo-cortical connectivity and whole brain functional network topology in Tourette's syndrome.

Tourette Syndrome (TS) is a neuropsychiatric disorder characterized by the presence of motor and vocal tics. Major pathophysiological theories posit a dysfunction of the cortico-striato-thalamo-cortical circuits as being a representative hallmark of the disease. Recent evidence suggests a more widespread dysfunction of brain networks in TS including the cerebellum and going even beyond classic motor pathways. In order to characterize brain network dysfunction in TS, in this study we investigated functional and effective-like connectivity as well as topological changes of basal ganglia-thalamo-cortical and cortico-cerebellar brain networks. We collected resting-state fMRI data from 28 TS patients (age: 32 ±â€¯11 years) and 28 age-matched, healthy controls (age: 31 ±â€¯9 years). Region of interest based (ROI-ROI) bivariate correlation and ROI-ROI bivariate regression were employed as measures of functional and effective-like connectivity, respectively. Graph theoretical measures of centrality (degree, cost, betweenness centrality), functional segregation (clustering coefficient, local efficiency) and functional integration (average path length, global efficiency) were used to assess topological brain network changes. In this study, TS patients exhibited increased basal ganglia-cortical and thalamo-cortical connectivity, reduced cortico-cerebellar connectivity, and an increase in parallel communication through the basal ganglia, thalamus and cerebellum (increased global efficiency). Additionally, we observed a reduction in serial information transfer (reduction in average path length) within the default mode and the salience network. In summary, our findings show that TS is characterized by increased connectivity and functional integration of multiple basal ganglia-thalamo-cortical circuits, suggesting a predominance of excitatory neurotransmission and a lack of brain maturation. Moreover, topological changes of cortico-cerebellar and brain networks involved in interoception may be underestimated neural correlates of tics and the crucial premonitory urge feeling.

Image-based analysis and long-term clinical outcomes of deep brain stimulation for Tourette syndrome: a multisite study.

BACKGROUND: Deep brain stimulation (DBS) can be an effective therapy for tics and comorbidities in select cases of severe, treatment-refractory Tourette syndrome (TS). Clinical responses remain variable across patients, which may be attributed to differences in the location of the neuroanatomical regions being stimulated. We evaluated active contact locations and regions of stimulation across a large cohort of patients with TS in an effort to guide future targeting. METHODS: We collected retrospective clinical data and imaging from 13 international sites on 123 patients. We assessed the effects of DBS over time in 110 patients who were implanted in the centromedial (CM) thalamus (n=51), globus pallidus internus (GPi) (n=47), nucleus accumbens/anterior limb of the internal capsule (n=4) or a combination of targets (n=8). Contact locations (n=70 patients) and volumes of tissue activated (n=63 patients) were coregistered to create probabilistic stimulation atlases. RESULTS: Tics and obsessive-compulsive behaviour (OCB) significantly improved over time (p<0.01), and there were no significant differences across brain targets (p>0.05). The median time was 13 months to reach a 40% improvement in tics, and there were no significant differences across targets (p=0.84), presence of OCB (p=0.09) or age at implantation (p=0.08). Active contacts were generally clustered near the target nuclei, with some variability that may reflect differences in targeting protocols, lead models and contact configurations. There were regions within and surrounding GPi and CM thalamus that improved tics for some patients but were ineffective for others. Regions within, superior or medial to GPi were associated with a greater improvement in OCB than regions inferior to GPi. CONCLUSION: The results collectively indicate that DBS may improve tics and OCB, the effects may develop over several months, and stimulation locations relative to structural anatomy alone may not predict response. This study was the first to visualise and evaluate the regions of stimulation across a large cohort of patients with TS to generate new hypotheses about potential targets for improving tics and comorbidities.

Global network modulation during thalamic stimulation for Tourette syndrome.

Background and objectives: Deep brain stimulation (DBS) of the thalamus is a promising therapeutic alternative for treating medically refractory Tourette syndrome (TS). However, few human studies have examined its mechanism of action. Therefore, the networks that mediate the therapeutic effects of thalamic DBS remain poorly understood. Methods: Five participants diagnosed with severe medically refractory TS underwent bilateral thalamic DBS stereotactic surgery. Intraoperative fMRI characterized the blood oxygen level-dependent (BOLD) response evoked by thalamic DBS and determined whether the therapeutic effectiveness of thalamic DBS, as assessed using the Modified Rush Video Rating Scale test, would correlate with evoked BOLD responses in motor and limbic cortical and subcortical regions. Results: Our results reveal that thalamic stimulation in TS participants has wide-ranging effects that impact the frontostriatal, limbic, and motor networks. Thalamic stimulation induced suppression of motor and insula networks correlated with motor tic reduction, while suppression of frontal and parietal networks correlated with vocal tic reduction. These regions mapped closely to major regions of interest (ROI) identified in a nonhuman primate model of TS. Conclusions: Overall, these findings suggest that a critical factor in TS treatment should involve modulation of both frontostriatal and motor networks, rather than be treated as a focal disorder of the brain. Using the novel combination of DBS-evoked tic reduction and fMRI in human subjects, we provide new insights into the basal ganglia-cerebellar-thalamo-cortical network-level mechanisms that influence the effects of thalamic DBS. Future translational research should identify whether these network changes are cause or effect of TS symptoms.

Deep brain stimulation for Tourette syndrome: a single-center series.

OBJECTIVE Tourette syndrome (TS) is a complex neuropsychiatric disorder characterized by multiple motor and phonic tics. While pharmacological and behavioral therapy can be effective in most patients, a subset of patients remains refractory to treatment. Increasing clinical evidence from multiple centers suggests that deep brain stimulation (DBS) of the medial thalamus can be effective in many cases of refractory TS. METHODS The authors retrospectively reviewed outcomes in 13 patients with refractory TS who underwent medial thalamic DBS performed by their team over a 7-year period. Patients were evaluated by a multidisciplinary team, and preoperative objective assessments were performed using the Yale Global Tic Severity Scale (YGTSS) and Yale-Brown Obsessive Compulsive Scale. YGTSS scores were calculated at visits immediately postoperatively and at the most recent follow-up in patients with a minimum of 6 months of postoperative follow-up. Coordinates of the active DBS contacts were calculated and projected onto each patient's pre- and postoperative images. RESULTS Patients showed an average decrease of 37% (p = 0.0063) in the total tic severity at their first postoperative visit. At their latest visit, their scores achieved significance, decreasing from preoperative scores by an average of 50% (p = 0.0014). The average position of the active contact was noted to be at the junction of the posterior ventralis oralis internus/centromedian-parafascicular nuclei. Device-related complications occurred in 2 patients, necessitating additional surgeries. All patients continued to use the system at last follow-up. CONCLUSIONS The authors' data are consistent with the small but growing body of literature supporting DBS of the ventralis oralis internus/centromedian-parafascicular thalamus as an effective and relatively safe treatment for severe, refractory TS.

Abnormalities in metabolite concentrations in tourette's disorder and obsessive-compulsive disorder-A proton magnetic resonance spectroscopy study.

INTRODUCTION: Abnormal glutamatergic transmission in cortico-striato-thalamo-cortical (CSTC) circuits is thought to be involved in the pathophysiology of Tourette's disorder (TD) and obsessive-compulsive disorder (OCD). Using proton magnetic resonance spectroscopy, the current study aimed to investigate regional concentrations of glutamatergic compounds in TD and OCD patients in comparison to healthy control subjects (HC). MATERIAL AND METHODS: Twenty-three TD patients, 20 OCD patients and 22 HC were included. Short echo-time single-voxel 3T MRS was obtained from dorsal anterior cingulate cortex (dACC) and midline bilateral thalamus. RESULTS: The 3-group comparison showed a significant difference in choline concentration in the thalamus. Thalamic choline was highest in OCD patients, showing a significant difference with TD, and a trend compared to HC (post-hoc analyses). Glutamine in dACC correlated negatively with tic severity scores in TD patients, while glutamate in thalamus correlated positively with anxiety severity scores in OCD patients. CONCLUSIONS: These findings suggest subtle differences in metabolites in CSTC areas between TD and OCD. Alterations of choline concentrations seem to be both regional (only in thalamus, not in dACC) and disease specific in OCD pathology. The findings need replication in larger groups, but encourage further research into glutamatergic metabolites in TD and OCD.

Pathological glutamatergic neurotransmission in Gilles de la Tourette syndrome.

Gilles de la Tourette syndrome is a hereditary, neuropsychiatric movement disorder with reported abnormalities in the neurotransmission of dopamine and γ-aminobutyric acid (GABA). Spatially focalized alterations in excitatory, inhibitory and modulatory neurochemical ratios within specific functional subdivisions of the basal ganglia, may lead to the expression of diverse motor and non-motor features as manifested in Gilles de la Tourette syndrome. Current treatment strategies are often unsatisfactory thus provoking the need for further elucidation of the underlying pathophysiology. In view of (i) the close spatio-temporal synergy exhibited between excitatory, inhibitory and modulatory neurotransmitter systems; (ii) the crucial role played by glutamate (Glu) in tonic/phasic dopaminergic signalling; and (iii) the interdependent metabolic relationship exhibited between Glu and GABA via glutamine (Gln); we postulated that glutamatergic signalling is related to the pathophysiology of Gilles de la Tourette syndrome. As such, we examined the neurochemical profile of three cortico-striato-thalamo-cortical regions in 37 well-characterized, drug-free adult patients and 36 age/gender-matched healthy control subjects via magnetic resonance spectroscopy at 3 T. To interrogate the influence of treatment on metabolite concentrations, spectral data were acquired from 15 patients undergoing a 4-week treatment with aripiprazole. Test-retest reliability measurements in 23 controls indicated high repeatability of voxel localization and metabolite quantitation. We report significant reductions in striatal concentrations of Gln, Glu + Gln (Glx) and the Gln:Glu ratio, and thalamic concentrations of Glx in Gilles de la Tourette syndrome in comparison to controls. ON-treatment patients exhibited no significant metabolite differences when compared to controls but significant increases in striatal Glu and Glx, and trends for increases in striatal Gln and thalamic Glx compared to baseline measurements. Multiple regression analysis revealed a significant negative correlation between (i) striatal Gln and actual tic severity; and (ii) thalamic Glu and premonitory urges. Our results indicate that patients with Gilles de la Tourette syndrome exhibit an abnormality in the flux of metabolites in the GABA-Glu-Gln cycle, thus implying perturbations in astrocytic-neuronal coupling systems that maintain the subtle balance between excitatory and inhibitory neurotransmission within subcortical nuclei.

Evaluation of basal ganglia and thalamic inflammation in children with pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection and tourette syndrome: a positron emission tomographic (PET) study using 11C-[R]-PK11195.

We applied PET scanning with (11)C-[R]-PK11195 (PK) to evaluate neuroinflammatory changes in basal ganglia and thalamus in children with clinically diagnosed pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS) and Tourette syndrome. Seventeen children with PANDAS (mean age: 11.4 ± 2.6 years; 13 males), 12 with Tourette syndrome (mean age: 11.0 ± 3.0 years; 10 males), and 15 normal adults (mean age: 28.7 ± 7.9 years; 8 males) underwent dynamic PK PET imaging and binding potential, a measure of ligand-TSPO receptor (expressed by activated microglia) binding, was calculated for basal ganglia and thalamus. Binding potential values, suggesting underlying activated microglia-mediated neuroinflammation, were found to be increased in bilateral caudate and bilateral lentiform nucleus in the PANDAS group and in bilateral caudate nuclei only in the Tourette syndrome group, compared to control group. These differences in the pattern and extent of neuroinflammation also signify a possible difference in pathophysiological etiology between PANDAS and Tourette syndrome patients.

New therapeutic approach to Tourette Syndrome in children based on a randomized placebo-controlled double-blind phase IV study of the effectiveness and safety of magnesium and vitamin B6.

BACKGROUND: Tourette Syndrome (TS) is a neurological condition presenting chronic motor and phonic tics, and important degree of comorbidity. Considered an uncommon illness, it first becomes apparent during childhood. Current standard treatment only achieves partial control of the condition, and provokes frequent, and sometimes severe, side effects. METHODS AND DESIGN: Main aim: To show that, with respect to placebo treatment, the combination of 0.5 mEq/Kg magnesium and 2 mg/Kg vitamin B6 reduces motor and phonic tics and incapacity in cases of exacerbated TS among children aged 7-14 years, as measured on the Yale Global Tic Severity Scale (YGTSS). Secondary aims: Assess the safety of the treatment. Describe metabolic changes revealed by PET. Measure the impact of the experimental treatment on family life. METHODOLOGY: Randomized, blinded clinical trials. Phase IV study (new proposal for treatment with magnesium and vitamin B6). SCOPE: children in the geographic area of the study group. Recruitment of subjects: to include patients diagnosed with TS, in accordance with DSM-IV criteria (307.23), during a period of exacerbation, and provided none of the exclusion criteria are met. INSTRUMENTATION: clinical data and the YGTSS score will be obtained at the outset of a period of exacerbation (t0). The examinations will be made after 15 (t1), 30 (t2), 60 (t3) and 90 days (t4). PET will be performed at the t0 and t4. We evaluated decrease in the overall score (t0, t1, t2, t3, t4), PET variations, and impact made by the treatment on the patient's life (Psychological General Well-Being Index). DISCUSSION: Few clinical trials have been carried out on children with TS, but they are necessary, as current treatment possibilities are insufficient and often provoke side effects. The difficulty of dealing with an uncommon illness makes designing such a study all the more complicated. The present study seeks to overcome possible methodological problems by implementing a prior, phase II study, in order to calculate the relevant statistical parameters and to determine the safety of the proposed treatment. Providing a collateral treatment with magnesium and vitamin B6 could improve control of the illness and help reduce side effects. This protocol was approved by the Andalusian Government Committee for Clinical Trials (Spain). This study was funded by the Health Department of the Andalusian Regional Government and by the Healthcare Research Fund of the Carlos III Healthcare Institute (Spanish Ministry of Health). TRIAL REGISTRATION: Current Controlled Trials ISRCTN41082378.

Tourette's syndrome.

Tourette's syndrome (TS) is a chronic disorder characterized by motor and vocal tics and a variety of associated behaviour disorders. Because current therapy is often unsatisfactory, there is expanding interest in new therapeutic strategies that are more effective, cause less side effects and ameliorate not only tics but also behavioural problems. From anecdotal reports and preliminary controlled studies it is suggested that - at least in a subgroup of patients - cannabinoids are effective in the treatment of TS. While most patients report beneficial effects when smoking marijuana (Cannabis sativa L.), available clinical trials have been performed using oral Δ9-tetrahydrocannabinol (THC). In otherwise treatment-resistant TS patients, therefore, therapy with THC should not be left unattempted. To date, it is unknown whether other drugs that interact with the endocannabinoid receptor system might be more effective in the treatment of TS than smoked marijuana or pure THC. Since it has been suggested that abnormalities within the endocannabinoid receptor system might underlie TS pathophysiology, it would be of interest to investigate the effect of substances that for example bind more selectively to the central cannabinoid receptor or inhibit the uptake or the degradation of different endocannabinoids.

Abnormal brain tryptophan metabolism and clinical correlates in Tourette syndrome.

Symptoms in Tourette syndrome (TS) are likely related to abnormalities involving multiple neurotransmitter systems in striatal-thalamo-cortical circuitry. Although prior studies have found abnormal levels of tryptophan, serotonin, and their metabolites in blood, cerebrospinal fluid and brain tissue of TS patients, understanding of focal brain disturbances and their relationship to clinical phenotype remains poor. We used alpha-[(11)C]methyl-L-tryptophan (AMT) positron emission tomography (PET) to assess global and focal brain abnormalities of tryptophan metabolism and their relationship to behavioral phenotype in 26 children with TS and nine controls. Group comparisons on regional cortical and subcortical AMT uptake revealed decreased AMT uptake in bilateral dorsolateral prefrontal cortical and bilaterally increased uptake in the thalamus (P = 0.001) in TS children. The ratio of AMT uptake in subcortical structures to dorsolateral prefrontal cortex was significantly increased bilaterally (P < 0.01) in TS patients also. Behaviorally defined subgroups within the TS sample revealed differences in the pattern of AMT uptake in the fronto-striatal-thalamic circuit. This study demonstrates cortical and subcortical abnormalities of tryptophan metabolism in TS and provides neuroimaging evidence for a role of serotonergic mechanisms in the pathophysiology of TS.

Altered mesolimbocortical and thalamic dopamine in Tourette syndrome.

We used [F-18]fallypride PET in six adults with Tourette syndrome and age-matched controls to assess extrastriatal dopamine 2 (D2) receptors. D2 receptor availability was significantly lower in the orbitofrontal cortex, primary motor cortex, anterior cingulate gyrus, mediodorsal nucleus of thalamus, and hippocampus, areas important for motivation and reward, sensory gating, movement, and attention. Altered dopaminergic function in mesolimbocortical systems and thalamus may contribute to increased motivational salience of tics.

Probing striato-thalamic function in obsessive-compulsive disorder and Tourette syndrome using neuroimaging methods.

In summary, contemporary pathophysiological models of OCD and related disorders implicate CSTC circuitry. In this chapter, we have reviewed relevant concepts related to implicit learning and more specifically, the use of an implicit sequence learning paradigm as a probe of striato-thalamic function. An initial PET investigation of patients with OCD confirmed a priori hypotheses of failure to recruit right striatum, despite the absence of a performance deficit (22). A modified version of the SRT was studied in conjunction with fMRI and yielded reliable right-lateralized striatal activation in a cohort of 10 male subjects, with clear spatial dissociation of caudate and putamen activation foci (119). Subsequent studies in our laboratory suggest that this paradigm also yields a reliable temporal window of thalamic deactivation, and hence a means for assessing thalamic gating in human subjects (120). Finally, as presented in this chapter, preliminary data from the fMRI-SRT in patients with OCD and TS as well as normal control subjects appear to replicate and extend the findings from our original PET-SRT study in OCD. Future investigations in our laboratory will seek to elaborate upon these preliminary results. In particular, we intend to study psychiatric comparison groups to establish the generalizability and/or specificity of these findings across disorders. Within OCD, we hope to explore the relationship between abnormal brain-activation patterns and symptom dimensions (34). Further, by studying subjects with remitted OCD who have been successfully treated, we hope to determine whether the observed brain-activation abnormalities represent state or trait markers. Finally, we have already begun to test a hypothesis of parallel processing deficiency in OCD by using a dual-task version of the SRT that makes simultaneous demands on implicit and explicit information processing systems (128). It is our hope that this program of research will yield new insights about OCD and related disorders, including TS. Most importantly, as other teams of investigators pursue complementary lines of inquiry, it is our wish that collective efforts in this field will lead to improved diagnosis and treatment, if not cure or prevention, for those who are afflicted with these illnesses.

Abnormal magnetic resonance imaging T2 relaxation time asymmetries in Tourette's syndrome.

Recent imaging studies in Tourette's syndrome (TS) have reported a loss of normal asymmetry in basal ganglia volumes. Our recent report of reduced midline sagittal cross-sectional area in TS suggests that altered lateralization may be widespread throughout the TS cerebrum. We report here our analyses of cerebral asymmetries of T2 (transverse or spin-spin) relaxation times derived from multi-echo/multi-planar/spin-echo magnetic resonance images in 14 adult TS subjects and 14 matched normal control subjects. T2 relaxation times were found to be asymmetric throughout the cerebrum of normal control subjects, with differences seen between T2 times of corresponding regions of both cerebral hemispheres that were small in magnitude (2-5%) but of a high degree of statistical significance in all regions examined. Our hypothesis of altered T2 relaxation time asymmetries in TS was confirmed in a multivariate analysis of variance, with post hoc analyses suggesting that group differences were attributable to specific asymmetry differences in the TS insular cortex and frontal white matter. Exploratory analyses revealed group differences in T2 times of the amygdala and red nucleus, as well as significantly lower ferritin levels in the TS group. These findings are discussed in relation to the previous TS volumetric studies, and the tissue characteristics that might produce normal and abnormal relaxation time asymmetries are considered.