Motor control, habits, complex motor stereotypies, and Tourette syndrome

Evidence for a dissociation between moral reasoning and moral decision-making in Tourette syndrome

Despite the growing interest on how Tourette syndrome (TS) affects social cognition skills, this field remains to date relatively under-explored. Here, we aim to advance knowledge on the topic by studying moral decision-making and moral reasoning in a group of adolescents with TS and a group of healthy controls. Overall, we found higher endorsement (i.e. a greater 'yes' response rate) for utilitarian solutions of incidental and instrumental moral dilemmas in TS compared to controls. By contrast, we reported an overall higher tendency of TS individuals to apply principles described in the moral foundation questionnaire to establish whether something is morally right or wrong. Our results document intact moral reasoning in TS and suggest that a deficit in suppressing inappropriate behaviours and/or altered sense of agency might be responsible for their higher utilitarian moral decision-making.

Development and Validation of an Assessment-Driven Behavioral Intervention for Primary Complex Motor Stereotypies in Young Children

Complex motor stereotypies are rhythmic, repetitive, fixed, and non-goal directed movements (e.g., bilateral flapping/waving movements of the hands/arms). Movements typically begin in early childhood and can occur in otherwise normally developing ("primary") or autistic ("secondary") children. Stereotypies persist, occur multiple times a day, have prolonged durations, can be socially stigmatizing, and may lead to bullying and isolation. Prior behavioral treatment studies have focused on older children (ages 6-12) and report modest reductions in stereotypy (i.e., between 14% and 33%). The current study involves the functional assessment and treatment of five children with Primary Complex Motor Stereotypy using a modified awareness training procedure, differential reinforcement of other behavior, and schedule thinning in a nonconcurrent multiple baseline design. Results suggest a 99% reduction of motor stereotypy from baseline across all participants.

Co-morbid tics and stereotypies: a systematic literature review

BACKGROUND

Tics and stereotypies are childhood-onset repetitive behaviours that can pose significant diagnostic challenges in clinical practice. Both tics and stereotypies are characterised by a complex co-morbidity profile, however little is known about the co-occurrence of these hyperkinetic disorders in the same patient population.

OBJECTIVE

This review aimed to assess the relationship between tics and stereotypies when these conditions present in co-morbidity.

METHODS

We conducted a systematic literature review of original studies on co-morbid tics and stereotypies, according to the standards outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Our literature search identified six studies of suitable sample size (n ≥ 40) presenting data on the association between tics and stereotypies in otherwise typically developing patients. A considerable proportion (23%) of patients diagnosed with stereotypic movement disorder present with co-morbid tics (range 18-43%). Likewise, the prevalence of primary stereotypies is increased in patients with tic disorders such as Tourette syndrome (8%, range 6-12%).

DISCUSSION

Tics and stereotypies can often develop in co-morbidity. The association of tics and stereotypies in the same patient has practical implications, in consideration of the different treatment approaches. Future research should focus on the assessment and management of both conditions, particularly in special populations (e.g. patients with pervasive developmental disorders).

Primary complex motor stereotypies are associated with de novo damaging DNA coding mutations that identify KDM5B as a risk gene

Motor stereotypies are common in children with autism spectrum disorder (ASD), intellectual disability, or sensory deprivation, as well as in typically developing children ("primary" stereotypies, pCMS). The precise pathophysiological mechanism for motor stereotypies is unknown, although genetic etiologies have been suggested. In this study, we perform whole-exome DNA sequencing in 129 parent-child trios with pCMS and 853 control trios (118 cases and 750 controls after quality control). We report an increased rate of de novo predicted-damaging DNA coding variants in pCMS versus controls, identifying KDM5B as a high-confidence risk gene and estimating 184 genes conferring risk. Genes harboring de novo damaging variants in pCMS probands show significant overlap with those in Tourette syndrome, ASD, and those in ASD probands with high versus low stereotypy scores. An exploratory analysis of these pCMS gene expression patterns finds clustering within the cortex and striatum during early mid-fetal development. Exploratory gene ontology and network analyses highlight functional convergence in calcium ion transport, demethylation, cell signaling, cell cycle and development. Continued sequencing of pCMS trios will identify additional risk genes and provide greater insights into biological mechanisms of stereotypies across diagnostic boundaries.

Immp2l knockdown in male mice increases stimulus-driven instrumental behaviour but does not alter goal-directed learning or neuron density in cortico-striatal circuits in a model of Tourette syndrome and autism spectrum disorder

Cortico-striatal neurocircuits mediate goal-directed and habitual actions which are necessary for adaptive behaviour. It has recently been proposed that some of the core symptoms of autism spectrum disorder (ASD) and Gilles de la Tourette syndrome (GTS), such as tics and other repetitive behaviours, may emerge because of imbalances in these neurocircuits. We have recently developed a model of ASD and GTS by knocking down Immp2l, a mitochondrial gene frequently associated with these disorders. The current study sought to determine whether Immp2l knockdown (KD) in male mice alters flexible, goal- or cue- driven behaviour using procedures specifically designed to examine response-outcome and stimulus-response associations, which underlie goal-directed and habitual behaviour, respectively. Whether Immp2l KD alters neuron density in cortico-striatal neurocircuits known to regulate these behaviours was also examined. Immp2l KD mice and wild type-like mice (WT) were trained on Pavlovian and instrumental learning procedures where auditory cues predicted food delivery and lever-press responses earned a food outcome. It was demonstrated that goal-directed learning was not changed for Immp2l KD mice compared to WT mice, as lever-press responses were sensitive to changes in the value of the food outcome, and to contingency reversal and degradation. There was also no difference in the capacity of KD mice to form habitual behaviours compared to WT mice following extending training of the instrumental action. However, Immp2l KD mice were more responsive to auditory stimuli paired with food as indicated by a non-specific increase in lever response rates during Pavlovian-to-instrumental transfer. Finally, there were no alterations to neuron density in striatum or any prefrontal cortex or limbic brain structures examined. Thus, the current study suggests that Immp2l is not necessary for learned maladaptive goal or stimulus driven behaviours in ASD or GTS, but that it may contribute to increased capacity for external stimuli to drive behaviour. Alterations to stimulus-driven behaviour could potentially influence the expression of tics and repetitive behaviours, suggesting that genetic alterations to Immp2l may contribute to these core symptoms in ASD and GTS. Given that this is the first application of this battery of instrumental learning procedures to a mouse model of ASD or GTS, it is an important initial step in determining the contribution of known risk-genes to goal-directed versus habitual behaviours, which should be more broadly applied to other rodent models of ASD and GTS in the future.

Creative thinking in Tourette's syndrome: A comparative study of patients and healthy controls

INTRODUCTION

Tourette's syndrome is a neurological disorder characterized by tics, that may interfere with patients' everyday life. Research suggested that creative thinking (namely, divergent and convergent thinking) could help patients cope with their symptoms, and therefore it can be a resource in non-pharmacological interventions. The present study aimed at investigating (i) possible differences in creative thinking between Tourette's syndrome patients and healthy controls and (ii) whether creative thinking can support patients in coping with their symptomatology.

METHODS

A group of 25 Tourette's syndrome patients and 25 matched healthy controls underwent an assessment of creative thinking, fluid intelligence, and depressive symptoms. Creative thinking was compared between patients and healthy controls after controlling for fluid intelligence and depressive symptoms. Moreover, the moderating role of divergent and convergent thinking on the subjective impact of tics was tested in a group of 30 patients.

RESULTS

Tourette's syndrome patients outperformed healthy controls in convergent thinking. Moreover, divergent thinking was found as a significant moderator of the relationship between tics severity and the subjective impact in Tourette's syndrome patients.

CONCLUSIONS

Findings highlighted the specific impact of convergent and divergent thinking on Tourette's syndrome patients. Considering the supportive role of creative thinking in Tourette's syndrome, our results confirm that higher levels of divergent thinking may reduce the tic-related discomfort. These findings suggest the potential positive implications of creative thinking in non-pharmacological interventions for Tourette's syndrome.

Former Training Relieves the Later Development of Behavioral Inflexibility in an Animal Model Overexpressing the Dopamine Transporter

A range of dopamine-dominating neuropsychiatric disorders present with cognitive deficits. In accordance, the dopamine transporter overexpressing rat model (DAT-tg rat) displays cognitive deficits by means of behavioral inflexibility and learning disabilities. It remains to be investigated when cognitive deficits emerge, due to the inherent DA irregularities, during the life course of the DAT-tg rat and what may relieve symptoms. The Morris water maze (MWM) was used to assess cognitive abilities in three cohorts of DAT-tg rats. In the first cohort, the development of cognitive deficits was assessed by repeatedly testing animals in the MWM at postnatal day (PND) 35, 60, and 90. In the second and third cohort, pharmacological interventions and transcranial direct current stimulation (tDCS) were tested in adult animals to understand what drives, and thus relieves, the deficits. Minor differences were observed between DAT-tg rats and control rats at PND 35 and 60, whereas cognitive deficits fully emerged at PND 90. A high dosage of methylphenidate diminished both behavioral inflexibility and improved learning abilities in adult rats. Interestingly, rats subjected early in life to the MWM also displayed improved behavioral flexibility as compared to rats naïve to the paradigm. Cognitive deficits gradually develop over time and fully emerge in adulthood. Pharmacological modulation of the ubiquitous DAT overexpression overall improves deficits in adult rats, whereas early training decreases later development of behavioral inflexibility. Thus, former training may constitute a preventive avenue that alters some aspects of cognitive deficits resulting from inherent DA abnormalities.

Descriptive Longitudinal Analysis of Stereotypy and Corresponding Changes in Psychotropic Medication

INTRODUCTION

Psychotropic medication is often prescribed to individuals with intellectual and developmental disabilities who engage in challenging and other behavior (e.g., aggression and stereotypy, respectively), but there is limited understanding of the effects of these medications on behavior.

OBJECTIVE

Within the context of a larger study that evaluated the effects of psychotropic medication regimen changes on the presentation of challenging behavior, this study describes the presentation of stereotypic behavior of three individuals diagnosed with autism spectrum disorder.

METHODS

Stereotypy was measured during weekly, one-hour, direct observations and during the control and ignore conditions of functional analyses of challenging behavior (which were conducted following changes in psychotropic medication regimens).

RESULTS

Patterns of stereotypy varied over time, but not significantly, and at times seemed to coincide with medication changes.

DISCUSSION

Our results suggest stereotypy persists throughout adulthood; however, additional research is needed.

Negative Urgency Exacerbates Relapse to Cocaine Seeking After Abstinence

BACKGROUND

The mechanisms through which drug-cue-induced negative affective states are involved in relapse have not been defined. We tested the hypothesis that in individuals having developed a dorsolateral striatum (DLS)-dependent cue-controlled cocaine-seeking habit, the loss of the opportunity to enact the drug-seeking response during abstinence results in an urge to act that exacerbates relapse severity mediated by negative urgency.

METHODS

Eighty-seven male Sprague Dawley rats were trained to seek cocaine under the influence of the conditioned reinforcing properties of drug-paired cues or not. We investigated whether the tendency to relapse depended on the aversive state of withdrawal or instead on the loss of opportunity to perform the ingrained drug-seeking response after periods of abstinence. The striatal locus of control over cocaine seeking at baseline and relapse was investigated using in situ hybridization of the cellular activity marker C-fos and assessment of the sensitivity of instrumental drug seeking to dopamine receptor blockade in the dorsomedial striatum-dependent goal-directed and DLS-dependent habit systems.

RESULTS

The development of a DLS-dependent cue-controlled cocaine-seeking habit prior to abstinence resulted in a marked increase in drug seeking at relapse, which was not motivated by a cocaine withdrawal state and was no longer dependent on the DLS habit system. Instead, it reflected the emergence of negative urgency caused by the prevention of the performance of the habit during abstinence and underpinned by transient engagement of the goal-directed system.

CONCLUSIONS

These results show that ingrained cue-controlled drug-seeking habits increase the pressure to relapse.

Genetic architecture of Tourette syndrome: our current understanding

Tourette syndrome (TS) is a severe neuropsychiatric disorder characterized by recurrent, involuntary physical and verbal tics. With a prevalence as high as 1% in children, a deeper understanding of the etiology of the disorder and contributions to risk is critical. Here, we cover the current body of knowledge in scientific literature regarding the genetics of TS. We first review the history and diagnostic criteria for TS cases. We then cover the prevalence, and begin to address the etiology of the disorder. We highlight long-standing evidence for a genetic contribution to TS risk from epidemiology studies focused on twins, families, and population-scale data. Finally, we summarize current large-scale genetic studies of TS along specific classes of genetic variation, including common variation, rare copy number variation, and de novo variation that impact protein-coding sequence. Although these variants do not account for the entirety of TS genetic risk, current evidence is clear that each class of variation is a factor in the overall risk architecture across TS cases.

Putative neural consequences of captivity for elephants and cetaceans

The present review assesses the potential neural impact of impoverished, captive environments on large-brained mammals, with a focus on elephants and cetaceans. These species share several characteristics, including being large, wide-ranging, long-lived, cognitively sophisticated, highly social, and large-brained mammals. Although the impact of the captive environment on physical and behavioral health has been well-documented, relatively little attention has been paid to the brain itself. Here, we explore the potential neural consequences of living in captive environments, with a focus on three levels: (1) The effects of environmental impoverishment/enrichment on the brain, emphasizing the negative neural consequences of the captive/impoverished environment; (2) the neural consequences of stress on the brain, with an emphasis on corticolimbic structures; and (3) the neural underpinnings of stereotypies, often observed in captive animals, underscoring dysregulation of the basal ganglia and associated circuitry. To this end, we provide a substantive hypothesis about the negative impact of captivity on the brains of large mammals (e.g., cetaceans and elephants) and how these neural consequences are related to documented evidence for compromised physical and psychological well-being.

The Role of the Cerebellum in Repetitive Behavior Across Species: Childhood Stereotypies and Deer Mice

Recent studies suggest that the cerebellum may have a significant role in repetitive behaviors. In primary complex motor stereotypies, typically developing children have repetitive movements usually involving rhythmic flapping/waving arm/hand movements. Similarly, the deer mouse animal model exhibits inherited repetitive behaviors, with increased frequencies of spontaneous jumping and rearing. In this study, data from both children with motor stereotypies and deer mice were used to investigate the role of the cerebellum in repetitive behaviors. The 3.0-T MRI volumetric imaging of the cerebellum was obtained in 20 children with primary complex motor stereotypies and 20 healthy controls. In deer mice, cerebellar volume (n = 7/group) and cell counts (n = 9/group) were compared between high- and low-activity animals. Levels of cerebellar neurotransmitters were also determined via HPLC (n = 10/group). In children with stereotypies, (a) there were a statistically significant reduction (compared to controls) in the white matter volume of the posterior cerebellar lobule VI-VII that negatively correlated with motor control and (b) an 8% increase in the anterior vermis gray matter that positively correlated with motor Stereotypy Severity Scores (SSS). In deer mice, (a) there was a significant increase in the volume of the anterior vermal granular cell layer that was associated with higher activity and (b) dentate nucleus cell counts were higher in high activity animals. Similar increases in volume were observed in anterior vermis in children with stereotypies and a deer mouse model of repetitive behaviors. These preliminary findings support the need for further investigation of the cerebellum in repetitive behaviors.

Beyond tics: movement disorders in patients with Tourette syndrome

BACKGROUND

Tics are the hallmark of Tourette syndrome (TS). However, TS patients may have a particular vulnerability to develop other movement disorders (MDs), such as dystonia, chorea, stereotypy, and other hyperkinetic disorders that may be wrongly attributed to tics.

MATERIALS AND METHODS

We studied a cohort of 201 patients with motor and phonic tics associated with TS to determine if they have additional, co-existent, MDs.

RESULTS

There were 67 (33.3%) patients with comorbid non-tic MDs. Phenomenology-wise, piano-playing movements resembling chorea or myoclonus, were the most common non-tic movement, observed in 11% of cases, followed by stereotypies (8.0%), tremor, dystonia and parkinsonism, 5.0% each. Drug-induced was the most common etiology (6.0%), followed by functional movement disorders (5.0%) and tardive phenomena (5.0%). No clear etiology was identified in most patients. Piano-playing movements, were associated with a younger age at onset (P = 0.004) and younger age at presentation (P < 0.001). Patients with drug-induced movements and tardive phenomena had a lower frequency of craniofacial tics. FMDs, and idiopathic MDS showed no specific associations with TS. Tic severity was not a predictor of any co-existent MD.

CONCLUSION

About a third of patients with TS present with comorbid MDs which should be differentiated and distinguished from tics as their etiopathogenesis and treatment may be different.

Aberrant prefrontal cortical-striatal functional connectivity in children with primary complex motor stereotypies

Motor stereotypies are rhythmic, repetitive, prolonged, predictable, and purposeless movements that stop with distraction. Although once believed to occur only in children with neurodevelopmental disorders such as autism, the presence and persistence of complex motor stereotypies (CMS) in otherwise typically developing children (primary CMS) has been well-established. Little, however, is known about the underlying pathophysiology of these unwanted actions. The aim of the present study was to use resting-state functional magnetic resonance imaging to evaluate functional connectivity within frontal-striatal circuits that are essential for goal-directed and habitual activity in children with primary complex motor stereotypies. Functional connectivity between prefrontal cortical and striatal regions, considered essential for developing goal-directed behaviors, was reduced in children with primary CMS compared to their typically developing peers. In contrast, functional connectivity between motor/premotor and striatal regions, critical for developing and regulating habitual behaviors, did not differ between groups. This documented alteration of prefrontal to striatal connectivity could provide the underlying mechanism for the presence and persistence of complex motor stereotypies in otherwise developmentally normal children.

A road map for identifying autism spectrum disorder: recognizing and evaluating characteristics that should raise red or "pink" flags to guide accurate differential diagnosis

Objective: Given the high population prevalence of Autism Spectrum Disorder (ASD) and overlapping symptoms with medically complex groups, ASD is a common rule out diagnosis for neuropsychologists even when not identified in the referral or initial presenting concerns. This paper presents practical guidance to support neuropsychologists in their ability to accurately assess, diagnose, and/or rule out ASD, especially in patients with more subtle presentations. Method: This paper combines clinical experience and empirical literature to highlight important assessment measures and related considerations, differential diagnostic considerations, common misconceptions about ASD and person/family characteristics, as well as variability in presentation and comorbidities that can obscure the diagnosis. Characteristics that may be considered "red flags" (clearly diagnostic, classic symptoms) and "pink flags" (associated features and symptoms that are suggestive of ASD but not quite definitive and that may overlap with symptoms seen in other neurodevelopmental or psychiatric diagnoses) will be discussed. Conclusions: Neuropsychologists in all clinical settings should be able to effectively screen for and/or diagnose ASD, even when its presentation is more subtle and/or when symptoms are masked by patient strengths in a way that makes their clinical presentation less obvious. Practical strategies for communicating the diagnosis and next steps/recommendations for interventions are reviewed.

The why behind the high: determinants of neurocognition during acute cannabis exposure

Acute cannabis intoxication may induce neurocognitive impairment and is a possible cause of human error, injury and psychological distress. One of the major concerns raised about increasing cannabis legalization and the therapeutic use of cannabis is that it will increase cannabis-related harm. However, the impairing effect of cannabis during intoxication varies among individuals and may not occur in all users. There is evidence that the neurocognitive response to acute cannabis exposure is driven by changes in the activity of the mesocorticolimbic and salience networks, can be exacerbated or mitigated by biological and pharmacological factors, varies with product formulations and frequency of use and can differ between recreational and therapeutic use. It is argued that these determinants of the cannabis-induced neurocognitive state should be taken into account when defining and evaluating levels of cannabis impairment in the legal arena, when prescribing cannabis in therapeutic settings and when informing society about the safe and responsible use of cannabis.

Reduced Glutamate Turnover in the Putamen Is Linked With Automatic Habits in Human Cocaine Addiction

BACKGROUND

The balance between goal-directed behavior and habits has been hypothesized to be biased toward the latter in individuals with cocaine use disorder (CUD), suggesting possible neurochemical changes in the putamen, which may contribute to their compulsive behavior.

METHODS

We assessed habitual behavior in 48 patients with CUD and 42 healthy control participants using a contingency degradation paradigm and the Creature of Habit Scale. In a subgroup of this sample (CUD: n = 21; control participants: n = 22), we also measured glutamate and glutamine concentrations in the left putamen using ultra-high-field (7T) magnetic resonance spectroscopy. We hypothesized that increased habitual tendencies in patients with CUD would be associated with abnormal glutamatergic metabolites in the putamen.

RESULTS

Compared with their non-drug-using peers, patients with CUD exhibited greater habitual tendencies during contingency degradation, which correlated with increased levels of self-reported daily habits. We further identified a significant reduction in glutamate concentration and glutamate turnover (glutamate-to-glutamine ratio) in the putamen in patients with CUD, which was significantly related to the level of self-reported daily habits.

CONCLUSIONS

Patients with CUD exhibit enhanced habitual behavior, as assessed both by questionnaire and by a laboratory paradigm of contingency degradation. This automatic habitual tendency is related to a reduced glutamate turnover in the putamen, suggesting a dysregulation of habits caused by chronic cocaine use.

Gray matter abnormalities in Tourette Syndrome: a meta-analysis of voxel-based morphometry studies

Tourette syndrome (TS) is a neurobehavioral disorder for which the neurological mechanism has not been elucidated. Voxel-based morphometry (VBM) studies have revealed abnormalities in gray matter volume (GMV) in patients with TS; however, consistent results have not been obtained. The current study attempted to provide a voxel wise meta-analysis of gray matter changes using seed-based d mapping (SDM). We identified ten relevant studies that investigated gray matter alterations in TS patients and performed a meta-analysis using the SDM method to quantitatively estimate regional gray matter abnormalities. Next, we examined the relationships between GMV abnormalities and demographic and clinical characteristics. Our results demonstrated that TS patients had smaller GMV in the bilateral inferior frontal gyri and greater GMV in the cerebellum, right striatum (putamen), and bilateral thalami (pulvinar nucleus) than healthy controls. A meta-regression analysis did not identify correlations between GMV changes and demographic or clinical variables. This meta-analysis confirmed significant and consistent GMV changes in several brain regions of TS patients, primarily in the cortico-striato-thalamo-cortical network.

PlexinA1 deficiency in BALB/cAJ mice leads to excessive self-grooming and reduced prepulse inhibition

PlexinA1 (PlxnA1) is a transmembrane receptor for semaphorins, a large family of proteins that act as axonal guidance cues during nervous system development. However, there are limited studies on PlxnA1 function in neurobehavior. The present study examined if PlxnA1 deficiency leads to behavioral abnormalities in BALB/cAJ mice. PlxnA1 knockout (KO) mice were generated by homologous recombination and compared to wild type (WT) littermates on a comprehensive battery of behavioral tests, including open field assessment of spontaneous ambulation, state anxiety, and grooming, home cage grooming, the wire hang test of muscle strength, motor coordination on the rotarod task, working memory on the Y maze alternation task, cued and contextual fear conditioning, anxiety on the elevated plus maze, sociability to intruders, and sensory processing as measured by prepulse inhibition (PPI). Measures of motor performance, working memory, fear memory, and sociability did not differ significantly between genotypes, while PlxnA1 KO mice displayed excessive self-grooming, impaired PPI, and slightly lower anxiety. These results suggest a crucial role for PlxnA1 in the development and function of brain regions controlling self-grooming and sensory gating. PlxnA1 KO mice may be a valuable model to investigate the repetitive behaviors and information processing deficits characteristic of many neurodevelopmental and psychiatric disorders.

Pharmacological targeting of striatal indirect pathway neurons improves subthalamic nucleus dysfunction and reduces repetitive behaviors in C58 mice

Repetitive behaviors (e.g., stereotypic movements, compulsions, rituals) are common features of a number of neurodevelopmental disorders. Clinical and animal model studies point to the importance of cortical-basal ganglia circuitry in the mediation of repetitive behaviors. In the current study, we tested whether a drug cocktail (dopamine D2 receptor antagonist + adenosine A2A receptor agonist + glutamate mGlu5 positive allosteric modulator) designed to activate the indirect basal ganglia pathway would reduce repetitive behavior in C58 mice after both acute and sub-chronic administration. In addition, we hypothesized that sub-chronic administration (i.e. 7 days of twice-daily injections) would increase the functional activation of the subthalamic nucleus (STN), a key node of the indirect pathway. Functional activation of STN was indexed by dendritic spine density, analysis of GABA, glutamate, and synaptic plasticity genes, and cytochrome oxidase activity. The drug cocktail used significantly reduced repetitive motor behavior in C58 mice after one night as well as seven nights of twice-nightly injections. These effects did not reflect generalized motor behavior suppression as non-repetitive motor behaviors such as grooming, digging and eating were not reduced relative to vehicle. Sub-chronic drug treatment targeting striatopallidal neurons resulted in significant changes in the STN, including a four-fold increase in brain-derived neurotrophic factor (BDNF) mRNA expression as well as a significant increase in dendritic spine density. The present findings are consistent with, and extend, our prior work linking decreased functioning of the indirect basal ganglia pathway to expression of repetitive motor behavior in C58 mice and suggest novel therapeutic targets.

Motor stereotypies in adult patients with Tourette syndrome

Aim: Correctly diagnosing repetitive behaviors in patients with Tourette syndrome (TS) can be challenging. The differential diagnosis between tics and stereotypies is of particular importance, because of treatment implications. Methods: We assessed the prevalence and clinical characteristics of stereotypies in a large sample of adult patients with TS attending a specialist clinic. Results: Mild stereotypies were reported by 21/148 patients (14.2%). Patients with stereotypies were significantly more likely to have a comorbid diagnosis of Asperger syndrome, attention-deficit and hyperactivity disorder, and obsessive-compulsive disorder, compared with patients without stereotypies. Multiple linear regression analysis revealed that the presence of Asperger syndrome significantly predicted stereotypy severity. Conclusion: Stereotypies are not rare in adults with TS and other neurodevelopmental conditions, especially Asperger syndrome.

Cortical endogenous opioids and their role in facilitating repetitive behaviors in deer mice

Deer mice provide a non-pharmacologically induced model for the study of repetitive behaviors. In captivity, these animals develop frequent jumping and rearing that resemble clinical symptoms of obsessive-compulsive behavior (OCB), autism spectrum disorder (ASD), complex motor stereotypies (CMS), and Tourette's syndrome (TS). In this study, we pursue the mechanism of repetitive behaviors by performing stereological analyses and liquid chromatography/ mass spectrometry (LC-MS/MS) measurements of glutamate (Glut), GABA, 3,4-dihydroxyphenylacetic acid (DOPAC), dopamine (DA), leu-enkephalin (leu-enk), and dynorphin-A (dyn-A) in frontal cortex (FC), prefrontal cortex (PFC), and basal ganglia. The only significant stereological alteration was a negative correlation between repetitive behaviors and the cell count in the ventromedial striatum (VMS). Neurochemical analyses demonstrated a significant negative correlation between repetitive behaviors and endogenous opioids (leu-enk and dyn-A) in the FC - the site of origin of habitual behaviors and cortical projections to striatal MSNs participating in direct and indirect pathways. The precise neurochemical process by which endogenous opioids influence synaptic neurotransmission is unknown. One postulated cortical mechanism, supported by our findings, is an opioid effect on cortical interneuron GABA release and a consequent effect on glutamatergic cortical pyramidal cells. Anatomical changes in the VMS could have a role in repetitive behaviors, recognizing that this region influences goal-directed and habitual behaviors.

Effects of Acupuncture on Behavioral Stereotypies and Brain Dopamine System in Mice as a Model of Tourette Syndrome

Tourette syndrome (TS), a developmental neurobehavioral disorder, is characterized by involuntary behavioral stereotypies. Clinical studies have confirmed the positive effect of acupuncture on treating TS, but the underlying mechanisms are not fully understood. In the present study, we used behavioral tests, Western blotting, double-immunofluorescence labeling, and fluorescence spectrophotometry to investigate whether acupuncture performed at acupoints "Baihui" (GV20) and "Yintang" (GV29) affected behavioral stereotypies and regulated the dopamine (DA) system in three different brain regions in Balb/c mice injected with 3,3'-iminodipropionitrile (IDPN) as a model for TS. We found that acupuncture alleviated behavioral stereotypies, down-regulated the expression of D1R and D2R in the striatum (STR) and substantia nigra pars compacta (SNpc), and decreased the concentration of DA in the STR, SNpc, and prefrontal cortex (PFC) as well. Moreover, acupuncture reduced the expression of tyrosine hydroxylase (TH) in the SNpc. Conclusively, acupuncture ameliorated behavioral stereotypies by regulating the DA system in the STR, SNpc, and PFC. Our findings provide novel evidence for the therapeutic effect of acupuncture on TS.

Reduction of repetitive behavior by co-administration of adenosine receptor agonists in C58 mice

Repetitive behaviors are diagnostic for autism spectrum disorder (ASD) and commonly observed in other neurodevelopmental disorders. Currently, there are no effective pharmacological treatments for repetitive behavior in these clinical conditions. This is due to the lack of information about the specific neural circuitry that mediates the development and expression of repetitive behavior. Our previous work in mouse models has linked repetitive behavior to decreased activation of the subthalamic nucleus, a brain region in the indirect and hyperdirect pathways in the basal ganglia circuitry. The present experiments were designed to further test our hypothesis that pharmacological activation of the indirect pathway would reduce repetitive behavior. We used a combination of adenosine A1 and A2A receptor agonists that have been shown to alter the firing frequency of dorsal striatal neurons within the indirect pathway of the basal ganglia. This drug combination markedly and selectively reduced repetitive behavior in both male and female C58 mice over a six-hour period, an effect that required both A1 and A2A agonists as neither alone reduced repetitive behavior. The adenosine A1 and A2A receptor agonist combination also significantly increased the number of Fos transcripts and Fos positive cells in dorsal striatum. Fos induction was found in both direct and indirect pathway neurons suggesting that the drug combination restored the balance of activation across these complementary basal ganglia pathways. The adenosine A1 and A2A receptor agonist combination also maintained its effectiveness in reducing repetitive behavior over a 7-day period. These findings point to novel potential therapeutic targets for development of drug therapies for repetitive behavior in clinical disorders.

Immunoglobulin A Dysgammaglobulinemia Is Associated with Pediatric-Onset Obsessive-Compulsive Disorder

Background: Inflammation and immune dysregulation have been implicated in the pathogenesis of pediatric-onset obsessive-compulsive disorder (OCD) and tic disorders such as Tourette syndrome (TS). Though few replicated studies have identified markers of immune dysfunction in this population, preliminary studies suggest that serum immunoglobulin A (IgA) concentrations may be abnormal in these children with these disorders. Methods: This observational retrospective cohort study, conducted using electronic health records (EHRs), identified 206 children with pediatric-onset OCD and 1024 adults diagnosed with OCD who also had testing for serum levels of IgA. IgA deficiency and serum IgA levels in pediatric OCD were compared with IgA levels from children diagnosed with autism spectrum disorders (ASD; n = 524), tic disorders (n = 157), attention-deficit/hyperactivity disorder (ADHD; n = 534), anxiety disorders (n = 1206), and celiac disease, a condition associated with IgA deficiency (n = 624). Results: Compared with ASD and anxiety disorder cohorts, the pediatric OCD cohort displayed a significantly higher likelihood of IgA deficiency (OR = 1.93; 95% CI = 1.18-3.16, and OR = 1.98; 95% CI = 1.28-3.06, respectively), though no difference was observed between pediatric OCD and TS cohorts. Furthermore, the pediatric OCD cohort displayed similar rates of IgA deficiency and serum IgA levels when compared with the celiac disease cohort. The pediatric OCD cohort also displayed the highest percentage of IgA deficiency (15%,) when compared with TS (14%), celiac disease (14%), ADHD (13%), ASD (8%), and anxiety disorder (8%) cohorts. When segregated by sex, boys with OCD displayed a significantly higher likelihood of IgA deficiency when compared with all comparison cohorts except for celiac disease and tic disorders; no significant difference in IgA deficiency was observed between female cohorts. Pediatric OCD subjects also displayed significantly lower adjusted serum IgA levels than the ASD and anxiety disorder cohorts. Adults with OCD were also significantly less likely than children with OCD to display IgA deficiency (OR = 2.71; 95% CI = 1.71-4.28). When compared with children with celiac disease, no significant difference in IgA levels or rates of IgA deficiency were observed in the pediatric OCD cohort. Conclusions: We provide further evidence of IgA abnormalities in pediatric-onset OCD. These results require further investigation to determine if these abnormalities impact the clinical course of OCD in children.

VGLUT3 gates psychomotor effects induced by amphetamine

Several subtypes of modulatory neurons co-express vesicular glutamate transporters (VGLUTs) in addition to their cognate vesicular transporters. These neurons are believed to establish new forms of neuronal communication. The atypical VGLUT3 is of particular interest since in the striatum this subtype is found in tonically active cholinergic interneurons (TANs) and in a subset of 5-HT fibers. The striatum plays a major role in psychomotor effects induced by amphetamine. Whether and how VGLUT3-operated glutamate/ACh or glutamate/5HT co-transmissions modulates psychostimulants-induced maladaptive behaviors is still unknown. Here, we investigate the involvement of VGLUT3 and glutamate co-transmission in amphetamine-induced psychomotor effects and stereotypies. Taking advantage of constitutive and cell-type specific VGLUT3-deficient mouse lines, we tackled the hypothesis that VGLUT3 could gate psychomotor effects (locomotor activity and stereotypies) induced by acute or chronic administration of amphetamine. Interestingly, VGLUT3-null mice demonstrated blunted amphetamine-induced stereotypies as well as reduced striatal ∆FosB expression. VGLUT3-positive varicosities within the striatum arise in part from 5HT neurons. We tested the involvement of VGLUT3 deletion in serotoninergic neurons in amphetamine-induced stereotypies. Mice lacking VGLUT3 specifically in 5HT fibers showed no alteration to amphetamine sensitivity. In contrast, specific deletion of VGLUT3 in cholinergic neurons partially phenocopied the effects observed in the constitutive knock-out mice. Our results show that constitutive deletion of VGLUT3 modulates acute and chronic locomotor effects induced by amphetamine. They point to the fact that the expression of VGLUT3 in multiple brain areas is pivotal in gating amphetamine-induced psychomotor adaptations. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Home-Based, Therapist-Assisted, Therapy for Young Children With Primary Complex Motor Stereotypies

BACKGROUND

Complex motor stereotypies (CMS) typically begin before age three years and include rhythmic, repetitive, fixed movements that last for seconds to minutes and can be interrupted with distraction.

OBJECTIVE

We evaluated the effectiveness of a home-based, parent-provided therapy accompanied by scheduled telephone calls with a therapist, in five- to seven-year old children with primary CMS.

METHODS

Eligible families received an instructional digital versatile disk (DVD) written instructions, and scheduled telephone contacts with a therapist at baseline (DVD receipt), one, three, and eight weeks later. At each call, parents completed outcome measures and received feedback. Outcome scales Stereotypy Severity Scale (SSS) Motor and Impairment scales and a Stereotypy Linear Analogue Scale (SLAS) were also completed via the Iinternet (REDCap)-at screening, one and two months post-baseline call. At study conclusion, participants were divided into an intent-to-treat (ITT; had at least one call) or a lost-to-follow-up (LTF) group.

RESULTS

Thirty-eight children (mean =  6 years ± 11 months) were enrolled. The LTF group (n = 14) had significantly higher scores than the ITT (n = 24) group on all attention-deficit/hyperactivity disorder ratings (P < 0.01), but not stereotypy severity. Primary outcome scores, acquired by telephone and REDCap, showed a significant reduction in SSS Motor and Impairment scores between the initial and the last completed evaluation (P ≤ 0.001). Calculated change ratios were SSS Motor -0.23/-0.30 (cal/REDCap); SSS Impairment -0.31/-0.32; and SLAS -0.54 (REDCap). Clinical improvement was further supported by results from a parent improvement scale and end of study questionnaires.

CONCLUSIONS

Home-based, parent-administered behavioral therapy supplemented by telephone contact with a therapist is effective in reducing complex motor stereotypies in children.

Update on the Pharmacological Treatment of Tics with Dopamine-Modulating Agents

More than 40 years of research and clinical practice have proven the effectiveness of dopamine receptor antagonists in the pharmacological treatment of tics. A blockade of the striatal dopamine-D2 receptors is mainly responsible for their tic-reducing effect. A broad spectrum of dopamine-modulating agents, such as typical and atypical antipsychotics, but also dopamine receptor agonists are used with an immanent discord between experts about which of them should be considered as first choice. The present Review outlines the state of the art on pharmacological treatment of tics with dopamine-modulating agents by giving an systematic overview of studies on their effectiveness and a critical discussion of their specific adverse effects. It is considered as an update of a previous review of our research group published in 2013. The Review closes with a description of the current resulting treatment recommendations including the results of a first published revised survey on European expert's prescription preferences. Based on the enormously growing evidence on its effectiveness and safety, aripiprazole currently seems to be the most promising agent in the pharmacological treatment of tics. Furthermore, benzamides (especially tiapride), which are commonly used in Europe, have proven their excellent effectiveness-tolerability profile over decades in clinical practice and are therefore also highly recommended for the treatment of tics. Nevertheless, pharmacological treatment of tics remains an indiviual choice depending on each patient's own specific needs.

Subthalamic nucleus pathology contributes to repetitive behavior expression and is reversed by environmental enrichment

Repetitive motor behaviors are common in neurodevelopmental, psychiatric and neurological disorders. Despite their prevalence in certain clinical populations, our understanding of the neurobiological cause of repetitive behavior is lacking. Likewise, not knowing the pathophysiology has precluded efforts to find effective drug treatments. Our comparisons between mouse strains that differ in their expression of repetitive behavior showed an important role of the subthalamic nucleus (STN). In mice with high rates of repetitive behavior, we found significant differences in dendritic spine density, gene expression and neuronal activation in the STN. Taken together, these data show a hypoglutamatergic state. Furthermore, by using environmental enrichment to reduce repetitive behavior, we found evidence of increased glutamatergic tone in the STN with our measures of spine density and gene expression. These results suggest the STN is a major contributor to repetitive behavior expression and highlight the potential of drugs that increase STN function to reduce repetitive behavior in clinical populations.

What makes you tic? Translational approaches to study the role of stress and contextual triggers in Tourette syndrome

Tourette syndrome (TS) is a neurodevelopmental condition characterized by multiple, recurring motor and phonic tics. Rich empirical evidence shows that the severity of tics and associated manifestations is increased by several stressors and contextual triggers; however, the neurobiological mechanisms responsible for symptom exacerbation in TS remain poorly understood. This conceptual gap partially reflects the high phenotypic variability in tics, as well as the existing difficulties in operationalizing and standardizing stress and its effects in a clinical setting. Animal models of TS may be highly informative tools to overcome some of these limitations; these experimental preparations have already provided critical insights on key aspects of TS pathophysiology, and may prove useful to identify the neurochemical alterations induced by different stressful contingencies. In particular, emerging knowledge on the role of contextual triggers in animal models of TS may inform the development of novel pharmacological interventions to reduce tic fluctuations in this disorder.

Motor Stereotypies: A Pathophysiological Review

Motor stereotypies are common, repetitive, rhythmic movements with typical onset in early childhood. While most often described in children with autism spectrum disorder (ASD) and intellectual disability (ID), stereotypies can also present without developmental delay and persist into adulthood. Stereotypies are often disruptive and harmful, both physically and socially, and effective evidence-based treatments are lacking. This can be attributed, in part, to our incomplete knowledge of the underlying biological and environmental risk. Several studies implicate various neurotransmitters, brain circuits, anatomical loci, and pre- and post-natal environmental influences in stereotypy onset and symptom severity. However, there are few points of convergence among a relatively small number of studies, indicating that more research is needed to confirm the underlying bases of risk. Of particular note is the lack of published genetic studies of stereotypies, despite evidence for Mendelian inheritance patterns in some families. Focusing future studies on typically-developing children with primary motor stereotypies may be a useful approach to minimize potential biological, environmental, and genetic heterogeneity that could theoretically hinder consistent findings. Ultimately, a deeper understanding of the underlying biology and risk factors for motor stereotypies will lead us closer to more effective targeted therapies that will alleviate suffering in affected children.

Gilles de la Tourette syndrome

Gilles de la Tourette syndrome (GTS) is a childhood-onset neurodevelopmental disorder that is characterized by several motor and phonic tics. Tics usually develop before 10 years of age, exhibit a waxing and waning course and typically improve with increasing age. A prevalence of approximately 1% is estimated in children and adolescents. The condition can result in considerable social stigma and poor quality of life, especially when tics are severe (for example, with coprolalia (swearing tics) and self-injurious behaviours) or when GTS is accompanied by attention-deficit/hyperactivity disorder, obsessive-compulsive disorder or another neuropsychiatric disorder. The aetiology is complex and multifactorial. GTS is considered to be polygenic, involving multiple common risk variants combined with rare, inherited or de novo mutations. These as well as non-genetic factors (such as perinatal events and immunological factors) are likely to contribute to the heterogeneity of the clinical phenotype, the structural and functional brain anomalies and the neural circuitry involvement. Management usually includes psychoeducation and reassurance, behavioural methods, pharmacotherapy and, rarely, functional neurosurgery. Future research that integrates clinical and neurobiological data, including neuroimaging and genetics, is expected to reveal the pathogenesis of GTS at the neural circuit level, which may lead to targeted interventions.

Anomalous Putamen Volume in Children With Complex Motor Stereotypies

BACKGROUND

Complex motor stereotypies in children are repetitive rhythmic movements that have a predictable pattern and location, seem purposeful, but serve no obvious function, tend to be prolonged, and stop with distraction, e.g., arm or hand flapping, waving. They occur in both "primary" (otherwise typically developing) and secondary conditions. These movements are best defined as habitual behaviors and therefore pathophysiologically hypothesized to reside in premotor to posterior putamen circuits. This study sought to clarify the underlying neurobiologic abnormality in children with primary complex motor stereotypies using structural neuroimaging, emphasizing brain regions hypothesized to underlie these atypical behaviors.

METHODS

High-resolution anatomic magnetic resonance images, acquired at 3.0 T, were analyzed in children aged eight to twelve years (20 with primary complex motor stereotypies and 20 typically developing). Frontal lobe subregions and striatal structures were delineated for analysis.

RESULTS

Significant reductions (P = 0.045) in the stereotypies group were identified in total putamen volume but not in caudate, nucleus accumbens, or frontal subregions. There were no group differences in total cerebral volume.

CONCLUSIONS

Findings of a smaller putamen provide preliminary evidence suggesting the potential involvement of the habitual pathway as the underlying anatomic site in primary complex motor stereotypies.

A verbal strength in children with Tourette syndrome? Evidence from a non-word repetition task

Tourette syndrome (TS) is characterized by motor and vocal tics, and frontal/basal-ganglia abnormalities. Whereas cognitive strengths have been found in other neurodevelopmental disorders, less attention has been paid to strengths in TS, or to verbal strengths in any neurodevelopmental disorder. We examined whether the finding of speeded TS production of rule-governed morphological forms (e.g., "slipped") that involve composition (Walenski, Mostofsky, & Ullman, 2007) might extend to another language domain, phonology. Thirteen children with TS and 14 typically-developing (TD) children performed a non-word repetition task: they repeated legal phonological strings (e.g.,"naichovabe"), a task that taps rule-governed (de)composition. Parallel to the morphology findings, the children with TS showed speeded production, while the two groups had similar accuracy. The results were not explained by potentially confounding factors, including IQ. Overall, the findings suggest that rule-governed grammatical composition may be speeded in TS, perhaps due to frontal/basal-ganglia abnormalities.

TS-EUROTRAIN: A European-Wide Investigation and Training Network on the Etiology and Pathophysiology of Gilles de la Tourette Syndrome

Gilles de la Tourette Syndrome (GTS) is characterized by the presence of multiple motor and phonic tics with a fluctuating course of intensity, frequency, and severity. Up to 90% of patients with GTS present with comorbid conditions, most commonly attention-deficit/hyperactivity disorder (ADHD), and obsessive-compulsive disorder (OCD), thus providing an excellent model for the exploration of shared etiology across disorders. TS-EUROTRAIN (FP7-PEOPLE-2012-ITN, Grant Agr.No. 316978) is a Marie Curie Initial Training Network (http://ts-eurotrain.eu) that aims to elucidate the complex etiology of the onset and clinical course of GTS, investigate the neurobiological underpinnings of GTS and related disorders, translate research findings into clinical applications, and establish a pan-European infrastructure for the study of GTS. This includes the challenges of (i) assembling a large genetic database for the evaluation of the genetic architecture with high statistical power; (ii) exploring the role of gene-environment interactions including the effects of epigenetic phenomena; (iii) employing endophenotype-based approaches to understand the shared etiology between GTS, OCD, and ADHD; (iv) establishing a developmental animal model for GTS; (v) gaining new insights into the neurobiological mechanisms of GTS via cross-sectional and longitudinal neuroimaging studies; and (vi) partaking in outreach activities including the dissemination of scientific knowledge about GTS to the public. Fifteen partners from academia and industry and 12 PhD candidates pursue the project. Here, we aim to share the design of an interdisciplinary project, showcasing the potential of large-scale collaborative efforts in the field of GTS. Our ultimate aims are to elucidate the complex etiology and neurobiological underpinnings of GTS, translate research findings into clinical applications, and establish Pan-European infrastructure for the study of GTS and associated disorders.

Increased corticolimbic connectivity in cocaine dependence versus pathological gambling is associated with drug severity and emotion-related impulsivity

Neural biomarkers for the active detrimental effects of cocaine dependence (CD) are lacking. Direct comparisons of brain connectivity in cocaine-targeted networks between CD and behavioural addictions (i.e. pathological gambling, PG) may be informative. This study therefore contrasted the resting-state functional connectivity networks of 20 individuals with CD, 19 individuals with PG and 21 healthy individuals (controls). Study groups were assessed to rule out psychiatric co-morbidities (except alcohol abuse and nicotine dependence) and current substance use or gambling (except PG). We first examined global connectivity differences in the corticolimbic reward network and then utilized seed-based analyses to characterize the connectivity of regions displaying between-group differences. We examined the relationships between seed-based connectivity and trait impulsivity and cocaine severity. CD compared with PG displayed increased global functional connectivity in a large-scale ventral corticostriatal network involving the orbitofrontal cortex, caudate, thalamus and amygdala. Seed-based analyses showed that CD compared with PG exhibited enhanced connectivity between the orbitofrontal and subgenual cingulate cortices and between caudate and lateral prefrontal cortex, which are involved in representing the value of decision-making feedback. CD and PG compared with controls showed overlapping connectivity changes between the orbitofrontal and dorsomedial prefrontal cortices and between amygdala and insula, which are involved in stimulus-outcome learning. Orbitofrontal-subgenual cingulate cortical connectivity correlated with impulsivity and caudate/amygdala connectivity correlated with cocaine severity. We conclude that CD is linked to enhanced connectivity in a large-scale ventral corticostriatal-amygdala network that is relevant to decision making and likely to reflect an active cocaine detrimental effect.

GABA and Glutamate in Children with Primary Complex Motor Stereotypies: An 1H-MRS Study at 7T

BACKGROUND AND PURPOSE

Complex motor stereotypies are rhythmic, repetitive, fixed, purposeful but purposeless movements that stop with distraction. They can occur in otherwise normal healthy children (primary stereotypies) as well in those with autism spectrum disorders (secondary stereotypies). The underlying neurobiologic basis for these movements is unknown but is thought to involve cortical-striatal-thalamo-cortical pathways. To further clarify potential neurochemical alterations, gamma-aminobutyric acid (GABA), glutamate, glutamine, N-acetylaspartate, and choline levels were measured in 4 frontostriatal regions by using (1)H MRS at 7T.

MATERIALS AND METHODS

A total of 18 children with primary complex motor stereotypies and 24 typically developing controls, ages 5-10 years, completed MR spectroscopy at 7T. Single voxel STEAM acquisitions from the anterior cingulate cortex, premotor cortex, dorsolateral prefrontal cortex, and striatum were obtained, and metabolites were quantified with respect to Cr by using LCModel.

RESULTS

The 7T scan was well tolerated by all the participants. Compared with the controls, children with complex motor stereotypies had lower levels of GABA in the anterior cingulate cortex (GABA/Cr, P = .049; GABA/Glu, P = .051) and striatum (GABA/Cr, P = .028; GABA/Glu, P = .0037) but not the dorsolateral prefrontal cortex or the premotor cortex. Glutamate, glutamine, NAA, and Cho levels did not differ between groups in any of the aforementioned regions. Within the complex motor stereotypies group, reduced GABA to Cr in the anterior cingulate cortex was significantly associated with greater severity of motor stereotypies (r = -0.59, P = .021).

CONCLUSIONS

These results indicate possible GABAergic dysfunction within corticostriatal pathways in children with primary complex motor stereotypies.

Enhanced habit formation in Gilles de la Tourette syndrome

Tics are sometimes described as voluntary movements performed in an automatic or habitual way. Here, we addressed the question of balance between goal-directed and habitual behavioural control in Gilles de la Tourette syndrome and formally tested the hypothesis of enhanced habit formation in these patients. To this aim, we administered a three-stage instrumental learning paradigm to 17 unmedicated and 17 antipsychotic-medicated patients with Gilles de la Tourette syndrome and matched controls. In the first stage of the task, participants learned stimulus-response-outcome associations. The subsequent outcome devaluation and ‘slip-of-action’ tests allowed evaluation of the participants’ capacity to flexibly adjust their behaviour to changes in action outcome value. In this task, unmedicated patients relied predominantly on habitual, outcome-insensitive behavioural control. Moreover, in these patients, the engagement in habitual responses correlated with more severe tics. Medicated patients performed at an intermediate level between unmedicated patients and controls. Using diffusion tensor imaging on a subset of patients, we also addressed whether the engagement in habitual responding was related to structural connectivity within cortico-striatal networks. We showed that engagement in habitual behaviour in patients with Gilles de la Tourette syndrome correlated with greater structural connectivity within the right motor cortico-striatal network. In unmedicated patients, stronger structural connectivity of the supplementary motor cortex with the sensorimotor putamen predicted more severe tics. Overall, our results indicate enhanced habit formation in unmedicated patients with Gilles de la Tourette syndrome. Aberrant reinforcement signals to the sensorimotor striatum may be fundamental for the formation of stimulus-response associations and may contribute to the habitual behaviour and tics of this syndrome.

Repetitive Behavior in Neurodevelopmental Disorders: Clinical and Translational Findings

Repetitive behavior refers to a highly heterogeneous set of responses associated with a wide range of conditions, including normative development. Treatment studies for aberrant repetitive behavior are limited although one promising approach involves conceptualizing such behavior as a generalized inflexibility or lack of variability in responding. Relatively little is known about the neurobiological mechanisms that mediate the development and expression of repetitive behavior, information critical to the design of effective pharmacotherapies, early interventions, and prevention strategies. We will review clinical findings in repetitive behavior as well as findings from animal models highlighting environmental factors and the role of cortical-basal ganglia circuitry in mediating the development and expression of these behaviors. Findings from animal models have included identification of a specific neural pathway important in mediating repetitive behavior. Moreover, pharmacological studies that support the importance of this pathway have led to the identification of novel potential therapeutic targets. Expanding the evidence base for environmental enrichment-derived interventions and focusing on generalized variability in responding will aid in addressing the broader problem of rigidity or inflexibility.

What do home videos tell us about early motor and socio-communicative behaviours in children with autistic features during the second year of life--An exploratory study

BACKGROUND

Little is known about the first half year of life of individuals later diagnosed with autism spectrum disorders (ASD). There is even a complete lack of observations on the first 6 months of life of individuals with transient autistic behaviours who improved in their socio-communicative functions in the pre-school age.

AIM

To compare early development of individuals with transient autistic behaviours and those later diagnosed with ASD.

STUDY DESIGN

Exploratory study; retrospective home video analysis.

SUBJECTS

18 males, videoed between birth and the age of 6 months (ten individuals later diagnosed with ASD; eight individuals who lost their autistic behaviours after the age of 3 and achieved age-adequate communicative abilities, albeit often accompanied by tics and attention deficit).

METHOD

The detailed video analysis focused on general movements (GMs), the concurrent motor repertoire, eye contact, responsive smiling, and pre-speech vocalisations.

RESULTS

Abnormal GMs were observed more frequently in infants later diagnosed with ASD, whereas all but one infant with transient autistic behaviours had normal GMs (p<0.05). Eye contact and responsive smiling were inconspicuous for all individuals. Cooing was not observable in six individuals across both groups.

CONCLUSIONS

GMs might be one of the markers which could assist the earlier identification of ASD. We recommend implementing the GM assessment in prospective studies on ASD.

The D1CT-7 mouse model of Tourette syndrome displays sensorimotor gating deficits in response to spatial confinement

BACKGROUND AND PURPOSE

The D1CT-7 mouse is one of the best known animal models of Tourette syndrome (TS), featuring spontaneous tic-like behaviours sensitive to standard TS therapies; these characteristics ensure a high face and predictive validity of this model, yet its construct validity remains elusive. To address this issue, we studied the responses of D1CT-7 mice to two critical components of TS pathophysiology: the exacerbation of tic-like behaviours in response to stress and the presence of sensorimotor gating deficits, which are thought to reflect the perceptual alterations causing the tics.

EXPERIMENTAL APPROACH

D1CT-7 and wild-type (WT) littermates were subjected to a 20 min session of spatial confinement (SC) within an inescapable, 10 cm wide cylindrical enclosure. Changes in plasma corticosterone levels, tic-like behaviours and other spontaneous responses were measured. SC-exposed mice were also tested for the prepulse inhibition (PPI) of the startle response (a sensorimotor gating index) and other TS-related behaviours, including open-field locomotion, novel object exploration and social interaction and compared with non-confined counterparts.

KEY RESULTS

SC produced a marked increase in corticosterone concentrations in both D1CT-7 and WT mice. In D1CT-7, but not WT mice, SC exacerbated tic-like and digging behaviours, and triggered PPI deficits and aggressive responses. Conversely, SC did not modify locomotor activity or novel object exploration in D1CT-7 mice. Both tic-like behaviours and PPI impairments in SC-exposed D1CT-7 mice were inhibited by standard TS therapies and D1 dopamine receptor antagonism.

CONCLUSIONS AND IMPLICATIONS

These findings collectively support the translational and construct validity of D1CT-7 mice with respect to TS.

LINKED ARTICLES

This article is part of a themed section on Updating Neuropathology and Neuropharmacology of Monoaminergic Systems. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.13/issuetoc.

Primary complex motor stereotypies in older children and adolescents: clinical features and longitudinal follow-up

BACKGROUND

Complex motor stereotypies are rhythmic, repetitive, fixed, and purposeless movements that stop with distraction. Once believed to occur only in children with autism spectrum or other developmental disorders, their presence in otherwise typically developing children (primary) has been well-established. In primary complex motor stereotypies, little information is available about the long-term outcome of these movements or existing comorbidities.

METHODS

Forty-nine healthy participants (31 boys), ages 9 to 20 years with primary complex motor stereotypies who were previously diagnosed at a pediatric movements disorder clinic, were identified from medical records. Parents or the young adult (if older than age 18), completed a telephone interview evaluating family history, outcome, and comorbidities including attention-deficit hyperactivity disorder, obsessive compulsive disorder, anxiety, and tics/Tourette syndrome. Standardized questionnaires assessing attention-deficit hyperactivity, obsessive compulsive disorder, and anxiety were used to validate parent report of comorbidities.

RESULTS

Stereotypy onset occurred before age 3 years in 98%. In all but one individual, stereotypies persisted at the time of phone follow-up (follow-up range: 6.8-20.3 years). Positive family history of complex motor stereotypies was identified in 39%. Most participants (92%) had concern for at least one comorbid disorder, including parent-/patient-reported clinically elevated levels of anxiety (73%), attention-deficit hyperactivity (63%), obsessive compulsive disorder (35%), and tics/Tourette syndrome (22%).

CONCLUSION

Primary motor stereotypies typically begin in early childhood and, although reduced in frequency and duration, persist at least through the teenage years. Repetitive movements are associated with a variety of comorbidities that often have a greater functional impact than the stereotypic behavior.

Altered hippocampal-dependent memory and motor function in neuropilin 2-deficient mice

Semaphorins have an important role in synapse refinement in the mammalian nervous system. The class 3 semaphorin-3F (Sema3F) acting through neuropilin 2/plexin-A3 (Nrp2/PlexA3) holoreceptor complex signals in vivo to restrain apical dendritic spine morphogenesis of cortical pyramidal neurons and hippocampal neurons during postnatal development and mediates excitatory synaptic transmission. Semaphorin signaling has been implicated in the etiology of a number of neurodevelopmental disorders; however, the effects on behavior and mental function of dysregulated Sema3F-Nrp2 signaling have not been fully addressed. The present study is the first behavioral investigation of mice harboring a mutation of the nrp2 gene. Given that loss of Nrp2 signaling alters cortical and hippocampal synaptic organization, we investigated performance of nrp2-deficient mice on learning and sensorimotor function that are known to depend on cortical and hippocampal circuitry. When compared with age-matched controls, nrp2 null mice showed striking impairments in object recognition memory and preference for social novelty. In addition, nrp2(-/-) mice displayed impaired motor function in the rotarod test and in observations of grooming behavior. Exploration of novel olfactory sensory stimuli and nociception were unaffected by the loss of Nrp2. Overall, loss of Nrp2 may induce aberrant processing within hippocampal and corticostriatal networks that may contribute to neurodevelopmental disease mechanisms.

Neuropsychological function in children with primary complex motor stereotypies

AIM

Complex motor stereotypies (CMS) are patterned, repetitive, rhythmic, and involuntary movements that persist over time. They are divided into two subgroups dependent on the presence of other developmental problems: 'primary' (development is otherwise typical) or 'secondary' (associated with autism, intellectual disability, or sensory deficits). There are no currently published studies that examine neuropsychological function in children with primary CMS. This case-control study examines whether children with primary CMS manifest neurobehavioral deficits.

METHOD

Fifty-seven children with primary CMS (32 males, 25 females; mean age 6y 8mo, SD 2y 4mo, range 4-12y) with negative screens for autism and 57 comparison participants (32 males, 25 females; mean age 6y 6mo, SD 2y 1mo) completed neuropsychological assessments of IQ, reading ability, attention, language, and motor and executive functions. Parents completed ratings of their child's repetitive movement severity.

RESULTS

The CMS group performed significantly less well than comparison participants on motor skills and IQ tests (both p<0.01), although IQ was consistently in the average range. One-third of the CMS group showed signs of developmental motor coordination difficulties. Parent report of stereotypy severity was significantly associated with parent report of inattention and executive dysfunction.

INTERPRETATION

Children with primary CMS were found to have largely intact neuropsychological profiles. Stereotypy severity appears to be associated with executive dysfunction. Although motor difficulties were observed in children with CMS, these were not correlated with parent report of symptom severity.