Repetitive Motor Research Articles

Motion Analysis of Grip during a Repetitive Motor Task: Differences in Hand Movements When Gripping T-Grip and Cylindrical Poles

Motion Analysis of Grip during a Repetitive Motor Task: Differences in Hand Movements When Gripping T-Grip and Cylindrical Poles

Dopamine receptor D4 (DRD4) polymorphisms with reduced functional potency intensify atrophy in syndrome-specific sites of frontotemporal dementia.

ObjectiveWe aimed to understand the impact of dopamine receptor D4 (DRD4) polymorphisms on neurodegeneration in patients with dementia. We hypothesized that DRD4dampened-variants with reduced functional potency would be associated with greater atrophy in regions with higher receptor density. Given that DRD4 is concentrated in anterior regions of the limbic and cortical forebrain we anticipated genotype effects in patients with a more rostral pattern of neurodegeneration.Methods337 subjects, including healthy controls, patients with Alzheimer's disease (AD) and frontotemporal dementia (FTD) underwent genotyping, structural MRI, and cognitive/behavioral testing. We conducted whole-brain voxel-based morphometry to examine the relationship between DRD4 genotypes and brain atrophy patterns within and across groups. General linear modeling was used to evaluate relationships between genotype and cognitive/behavioral measures.ResultsDRD4 dampened-variants predicted gray matter atrophy in disease-specific regions of FTD in anterior cingulate, ventromedial prefrontal, orbitofrontal and insular cortices on the right greater than the left. Genotype predicted greater apathy and repetitive motor disturbance in patients with FTD. These results covaried with frontoinsular cortical atrophy. Peak atrophy patterned along regions of neuroanatomic vulnerability in FTD-spectrum disorders. In AD subjects and controls, genotype did not impact gray matter intensity.ConclusionsWe conclude that DRD4 polymorphisms with reduced functional potency exacerbate neuronal injury in sites of higher receptor density, which intersect with syndrome-specific regions undergoing neurodegeneration in FTD.

Rhythmic auditory cues shape neural network recruitment in Parkinson's disease during repetitive motor behavior.

It is well established clinically that rhythmic auditory cues can improve gait and other motor behaviors in Parkinson's disease (PD) and other disorders. However, the neural systems underlying this therapeutic effect are largely unknown. To investigate this question we scanned people with PD and age-matched healthy controls using functional magnetic resonance imaging (fMRI). All subjects performed a rhythmic motor behavior (right hand finger tapping) with and without simultaneous auditory rhythmic cues at two different speeds (1 and 4Hz). We used spatial independent component analysis (ICA) and regression to identify task-related functional connectivity networks and assessed differences between groups in intra- and inter-network connectivity. Overall, the control group showed greater intra-network connectivity in perceptual and motor related networks during motor tapping both with and without rhythmic cues. The PD group showed greater inter-network connectivity between the auditory network and the executive control network, and between the executive control network and the motor/cerebellar network associated with the motor task performance. We interpret our results as indicating that the temporal rhythmic auditory information may assist compensatory mechanisms through network-level effects, reflected in increased interaction between auditory and executive networks that in turn modulate activity in cortico-cerebellar networks.

Assessing subtypes of restricted and repetitive behaviour using the Adult Repetitive Behaviour Questionnaire-2 in autistic adults

BackgroundThe majority of previous research into restricted and repetitive behaviours (RRBs) has focussed on children, partly due to a lack of suitable measures for RRBs in adults. This study aimed to explore the psychometric properties of the Adult Repetitive Behaviour Questionnaire-2 (RBQ-2A) in a large sample of autistic adults using a self-report questionnaire method.MethodsThe RBQ-2A and Autism-Spectrum Quotient (AQ) were administered online. Data from 275 autistic adults aged 18–66 (M = 36.56, SD = 12.24; 100 men and 171 women) were analysed using polychoric principal components analysis (PCA). Reliability and validity were assessed using Cronbach’s alpha and correlation analyses.ResultsPCA resulted in two components of the RBQ-2A, interpretable as repetitive sensory and motor behaviours (RSMB) and insistence on sameness (IS). Both components showed acceptable internal consistency (α = .70 and .81 respectively) and were significantly moderately correlated with scores on the AQ (rs = .25 and .42). Participants’ scores on IS were higher than their scores on RSMB. RSMB, but not IS, was negatively associated with age, particularly in older adults (≥ 50 years). There were no gender differences.ConclusionsThe RBQ-2A is a reliable and valid self-report measure of RRBs in the present sample of autistic adults. As one of the few measures of RRBs aimed at adults, it is suitable for adults with the ability to read and complete a self-report questionnaire. Results build on previous work with children using the Repetitive Behaviour Questionnaire-2 (RBQ-2).

Sensory hypersensitivity predicts repetitive behaviours in autistic and typically-developing children

The objective of this study was to examine the relationship between sensory hypersensitivity and restricted interests and repetitive behaviours associated with autism spectrum disorder and their typically-developing peers. Furthermore, the aims included the examination of the relationship across sensory modalities and various types of restricted interests and repetitive behaviours. Data were collected from the parents of 114 children: 49 of whom were diagnosed with autism spectrum disorder and 65 typically-developing children. Parents completed the Sensory Profile 2 - Child Version and the Repetitive Behaviours Questionnaire, Second Edition. The results suggested that sensory hypersensitivity is strongly related to the core autism spectrum disorder symptom of repetitive behaviours. This relationship was not specific to autism spectrum disorder; repetitive behaviours significantly increased with sensory hypersensitivity in typically-developing individuals as well. This effect was consistent across all modalities in both autism spectrum disorder and typically developing groups; group differences were observed in the oral and tactile modalities. Furthermore, sensory hypersensitivity was significantly predictive of repetitive behaviours in all participants, autism spectrum disorder and typically-developing, and importantly, autism spectrum disorder diagnosis did not add any predictive influence above and beyond sensory hypersensitivity. Finally, sensory hypersensitivity was significantly predictive of all subdomains of repetitive behaviours, including repetitive motor movements, rigidity and adherence to routine, preoccupation with restricted patterns of interest and unusual sensory interests, and diagnosis added no predictive ability beyond sensory hypersensitivity.

Home-based transcranial direct current stimulation plus tracking training therapy in people with stroke: an open-label feasibility study

BackgroundTranscranial direct current stimulation (tDCS) is an effective neuromodulation adjunct to repetitive motor training in promoting motor recovery post-stroke. Finger tracking training is motor training whereby people with stroke use the impaired index finger to trace waveform-shaped lines on a monitor. Our aims were to assess the feasibility and safety of a telerehabilitation program consisting of tDCS and finger tracking training through questionnaires on ease of use, adverse symptoms, and quantitative assessments of motor function and cognition. We believe this telerehabilitation program will be safe and feasible, and may reduce patient and clinic costs.MethodsSix participants with hemiplegia post-stroke [mean (SD) age was 61 (10) years; 3 women; mean (SD) time post-stroke was 5.5 (6.5) years] received five 20-min tDCS sessions and finger tracking training provided through telecommunication. Safety measurements included the Digit Span Forward Test for memory, a survey of symptoms, and the Box and Block test for motor function. We assessed feasibility by adherence to treatment and by a questionnaire on ease of equipment use. We reported descriptive statistics on all outcome measures.ResultsParticipants completed all treatment sessions with no adverse events. Also, 83.33% of participants found the set-up easy, and all were comfortable with the devices. There was 100% adherence to the sessions and all recommended telerehabilitation.ConclusionstDCS with finger tracking training delivered through telerehabilitation was safe, feasible, and has the potential to be a cost-effective home-based therapy for post-stroke motor rehabilitation.Trial registrationNCT02460809 (ClinicalTrials.gov).

A Brief Introduction to the Measurement and Classification of Restricted and Repetitive Behaviors in Autism Spectrum Disorders

Restricted and repetitive behaviors (RRB) is one of the core features of autism spectrum disorder (ASD) which consists of a group of heterogeneous behaviors. Tools of the measurement of RRBs mainly include direct clinical observation of children (such as Autism Diagnostic Observation Scale, ADOS), parental development history interview (Autism Diagnostic Interview-Revised, ADI-R) and parental questionnaire (Repetitive Behavior Scale-Revised. RBS-R, etc.). Using these scales, a number of studies have classified RRBs into repetitive sensory motor (RSM) and insistence on sameness (IS), corresponding to lower level and higher level RRBs respectively. A third factor circumstanced interest (CI) may also exist. Factors influencing the severity of RRBs includes age and IQ. Further researches should focus on integrating phenotypic and pathological studies of RRBs.

Force Increase in a Repetitive Motor Task Inducing Motor Fatigue

To evaluate task induced motor fatigue in a well-established finger tapping task, we analyzed tapping parameters and included the time course of measures of force. We hypothesized that a decline in tapping force would reflect task induced motor fatigue, defined by a lengthening of inter-tap intervals (ITI). A secondary aim was to investigate the reliability of tapping data acquisition with the force sensor. Results show that, as expected, tapping speed decreased linearly over time, due to both an increase of ITI and tap duration. In contrast, tapping force increased non-linearly over time and was uncorrelated to changes in tapping speed. Force data could serve as a measure to characterize task induced motor fatigue. Force sensors can assess a decline in tapping speed as well as an independent increase of tapping force. We argue that the increase of force reflects central compensation, i.e. perception of fatigue, due to an increase in task effort and difficulty.

Auditory time perception in Huntington's disease

BackgroundHuntington's disease (HD) is characterized by early involvement of the striatum. It affects the pace of repetitive motor activity, as motor timing depends on basal ganglia activity. However, data are lacking on the impact of this process on auditory time perception in motor non-affected gene carriers. ObjectiveThis work aims to test the performance in time perception of a group of mutation carriers, either without motor symptoms or at an early stage of motor involvement. This should allow designing therapies targeting compensation strategies and possibly be used as a disease progression marker. MethodTime was assessed using two different tasks. An absolute, duration-based time perception was assessed in a first task and a relative, beat-based time perception was assessed in a second one. HD-mutation carriers with low-to-middle grades of motor involvement (HD-motor, n = 10) or without motor signs (HD-premotor n = 21), were compared with age- and sex-matched healthy controls (control (n = 27)). Thresholds of time difference perception where assessed. ResultsFor both tasks, poorer performances were found in HD-motor patients as compared with HD-premotor and controls. Thresholds of time difference perception correlated positively with the CAP score for the whole group of HD-gene carriers in both tasks. In a post-hoc exploratory analysis performed by a multiple regression, a negative correlation was found between the thresholds in both tasks and the Stroop interference test. Furthermore, in the first task, a positive correlation was found between thresholds and a trail making B test and a negative one with a total functional score. ConclusionOur data confirm that the impairment in time perception in persons affected by HD correlates with the advancing disease. They also suggest that time perception depends on similar cognitive mechanisms as the ones sub-serving the Stroop interference test.

A Phenotype of Childhood Autism Is Associated with Preexisting Maternal Anxiety and Depression.

This study explored whether ASD phenotypes in the child were associated with a history of anxiety or depression in the mother. We hypothesized that an ASD profile in children characterized by mild delays and increased rates of dysregulation would be associated with preexisting maternal anxiety or depression. Participants were 672 preschool children with ASD and their mothers. Children were classified as ASD after a comprehensive developmental evaluation. Mothers reported whether a healthcare provider ever diagnosed them with anxiety or depression before the birth of their child. Four child ASD phenotypes were derived from latent class analysis: Mild Language Delay with Cognitive Rigidity (Type 1), Significant Developmental Delay with Repetitive Motor Behaviors (Type 2), General Developmental Delay (Type 3), and Mild Language and Motor Delay with Dysregulation (i.e., aggression, anxiety, depression, emotional reactivity, inattention, somatic complaints, and sleep problems) (Type 4). Type 2 ASD served as the referent category in statistical analyses. Results showed that 22.6% of mothers reported a diagnosis of anxiety or depression before the birth of their child. Maternal anxiety or depression was associated with 2.7 times the odds (95% confidence interval: 1.4, 5.3) of Type 4 or Dysregulated ASD in the child; maternal anxiety and depression was associated with 4.4 times the odds (95% confidence interval: 1.4, 14.0) of Type 4 or Dysregulated ASD in the child. Our findings suggest an association between Dysregulated ASD in the child and anxiety and depression in the mother. These findings can enhance screening methods and inform future research efforts.

The autism spectrum phenotype in ADNP syndrome.

Pathogenic disruptions to the activity-dependent neuroprotector homeobox (ADNP) gene are among the most common heterozygous genetic mutations associated with autism spectrum disorders (ASDs). Individuals with ADNP disruptions share a constellation of medical and psychiatric features, including ASD, intellectual disability (ID), dysmorphic features, and hypotonia. However, the profile of ASD symptoms associated with ADNP may differ from that of individuals with another ASD-associated single gene disruption or with ASD without a known genetic cause. The current study examined the ASD phenotype in a sample of representative youth with ADNP disruptions. Participants (N = 116, ages 4-22 years) included a cohort with ADNP mutations (n = 11) and three comparison groups with either a mutation to CHD8 (n = 11), a mutation to another ASD-associated gene (other mutation; n = 53), or ASD with no known genetic etiology (idiopathic ASD; n = 41). As expected, individuals with ADNP disruptions had higher rates of ID but less severe social affect symptoms compared to the CHD8 and Idiopathic ASD groups. In addition, verbal intelligence explained more variance in social impairment in the ADNP group compared to CHD8, other mutation, and idiopathic ASD comparison groups. Restricted and repetitive behaviors in the ADNP group were characterized by high levels of stereotyped motor behaviors, whereas the idiopathic ASD group showed high levels of restricted interests. Taken together, these results underscore the role of ADNP in cognitive functioning and suggest that social impairments in ADNP syndrome are consistent with severity of verbal deficits. Autism Res 2018, 11: 1300-1310. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Disruptions to the ADNP gene (i.e., ADNP syndrome) have been associated with autism spectrum disorder (ASD). This article describes intellectual disability, mild social difficulties, and severe repetitive motor movements in a group of 11 youth with ADNP Syndrome. We found lower rates of ASD than previously reported. Verbal skills explained individual variability in social impairment. This pattern suggests that the ADNP gene is primarily associated with learning and memory, and level of social difficulties is consistent with level of verbal impairment.

Efferent Vision Therapy.

Traditional orthoptic therapy used by ophthalmologists, orthoptists, and optometrists is directed at improving visual acuity, ocular alignment, or both. For example, convergence exercises are used to treat convergence insufficiency (CI). However, other forms of "vision therapy" are directed at improving "visual processing and efficiency." The therapeutic regimen often entails repetitive ocular motor tasks performed during multiple office visits with a behavioral optometrist. These ocular motor tasks are used to treat diverse conditions such as learning disabilities, poor reading ability, dyslexia, and attention-deficit hyperactivity disorder (ADHD). Evidence regarding the efficacy of therapy directed at ocular motility for the treatment of multiple conditions is reviewed. Review of literature. Randomized, controlled, double-masked studies show that convergence exercises reduce symptoms and improve signs of CI in otherwise healthy patients. However, the most efficacious convergence tasks, and the optimal duration and frequency of these tasks, remain unknown. Patients with learning disabilities, poor reading ability, dyslexia, or ADHD do not consistently have unique ocular motor deficits. Patients who acquire ocular motor deficits do not develop these conditions. There are no randomized, controlled studies that show treatment consisting of repetitive ocular motor tasks improves learning disabilities, reading, dyslexia, or ADHD. Convergence exercises effectively treat CI in healthy patients. The optimal treatment regimen is unknown. There is insufficient evidence to recommend "vision therapy" for the treatment of learning disabilities, impaired reading, dyslexia, or ADHD.

HABIT DISORDERS

Introduction: Childhood habit behaviors appear in numerous different forms.Many people engage in some degree of habit like behavior in their lifetime. For example,habits can range from seemingly benign behaviors, such as nail biting or foot tapping, to morenoticeable physically damaging behaviors, such as teeth grinding (bruxism) and hair pulling.Habit disorders, now subsumed under the diagnostic term stereotypic movement disorder,consist of repetitive, seemingly driven, and nonfunctional motor behaviors that interfere withnormal activities or that result in bodily injury. Objectives: To determine the frequency ofdifferent habit disorders in children coming to outpatient department of Pediatrics unit of AlliedHospital Faisalabad. Study design: Cross sectional study. Setting: Pediatric department ofAllied Hospital Faisalabad. Duration of study: 1 year 06 months. (From 01-03-2015 to 01-09-2016). Results: We determined that majority of the patients i.e. 40.68%(n=72) were between49-72 months, mean and sd was 54.23+21.45 months of age, 54.80%(n=97) male and45.20%(n=80) females, frequency of different habit disorders in children coming to outpatientdepartment of pediatrics unit of Allied Hospital, Faisalabad revealed 19.31%(n=34), nail biting,22.03%(n=39) had thumb sucking, 41.81%(n=74) had bruxism, 11.86%(n=21) had hair pullingand 10.17%(n=18) subjects had other habits. Conclusion: We concluded that the frequency ofdifferent habit disorders i.e. nail biting, thumb sucking, bruxism, hair pulling and other is higheramong children coming to outpatient department of Pediatrics unit of Allied Hospital Faisalabadand comparable with other studies.

The measurements and mechanisms of restricted and repetitive behaviors in autism spectrum disorders

Restricted and repetitive behaviors (RRBs) are one of the core features of autism spectrum disorders (ASD). RRBs encompass a broad range of heterogeneous behaviors, such as repetitive and stereotyped motor behavior or speech, atypical sensory behavior, inflexible interest and rituals, and insistence on the sameness of environment. While a large amount of previous research has focused on social deficits in ASD, little attention has been paid to their RRBs. The definition, classification, and underlying mechanism of RRBs have remained to be clarified. Recently, Diagnostic and Statistical Manual of Mental Disorders (5th ed, DSM-V) has classified RRBs into several subcategories and renewed the diagnostic criteria of RRBs. New theories and evidence from neurobiological, cognitive psychological, and developmental psychological research are also emerging about the etiology of RRBs. The first aim of this review is to introduce the newest definition and subcategories of RRBs based on DSM-V. We also discuss and compare different structural models of RRBs derived from several factor analysis studies. The second aim is to summarize the current assessment tools of RRBs in autism. Besides the “golden standard” -- the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview-Revised (ADI-R), and several common used questionnaires such as Repetitive Behavior Scale-Revised (RBS-R) and Repetitive Behavior Questionnaire-2 (RBQ-2), new techniques including eye-tracking, accelerometry, and electrodermal activity (EDA) have been applied into the studies of RRBs. The third aim of this review is to discuss the potential causal origins underlying the RRBs. The neurobiological and cognitive mechanism of RRBs, as well as other factors that directly related to the onset of RRBs have been summarized. The neurobiological evidence indicates that the atypical activity of neurotransmitters, the imbalanced activity among the corticostriatal circuits, and the neuroanatomical alterations play important roles on the RRBs. From the perspective of cognitive psychology, classical theories such as executive functions, weak central coherence, extreme male brain theory, and operational conditioning all offer their own explanations for the onset of RRBs. Besides, the hyper- or hypo-arousal theory indicates that RRBs may function as coping strategies for the individuals with ASD to regulate levels of arousal or anxiety, with the intolerance of uncertainty as the mediator. The evidence from developmental psychology focus on the developmental trajectory of RRBs across age. Results from longitudinal studies identify the significant influence of age and intelligence on the developmental trajectory of RRBs. Severe impacts of environmental deprivation and social isolation on the RRBs have also been shown in animal and human studies and provide implication for early intervention. Finally, several future directions for the research on RRBs in ASD have also been proposed based on the current literature. We recommend future research that focuses on the united standard for classification and the direct connection between neurobiology and behavior. Also, a clear understanding of the developmental trajectories of RRBs in typical developing children and children with ASD is of importance for effective early interventions. Last but not least, the characteristics of parents and the prenatal maternal stress are worthy of future investigations.

Evidence for Sequential Performance Effects in Professional Darts.

Objectives: The study of sequential effects in aiming tasks might shed light on the organization of repetitive motor performances over time. To date, investigations of such effects in sports have been limited and yielded mixed results. Given the relatively short time intervals between successive attempts, and the absence of defensive interventions, dart throwing provides a potentially fruitful testing ground for examining the presence of sequential performance effects in the motor domain.Methods and Results: A total of 80 competitive darts matches of 10 of the world’s best players were scored from publicly available video footage in terms of sequences of hits and misses of triple 20. In darts, throws are organized in legs, i.e., a rapid succession of three throws by the same player, allowing us to investigate various transitions in performance (throw 1 → 2, 2 → 3, and 3 → 1). The resulting binary sequences were analyzed statistically in terms of independence and stationarity. Across players significant statistical evidence was found for sequential dependence from the first throw in a leg to the second throw, but not for the other transitions. As regards to stationarity, a significant decline in performance was observed in the course of the match.Conclusions: In professional darts, evidence can be found for both sequential dependence as well as for non-stationarity, implying that performance does not, or at least not always, constitute a stationary random independent process. More research is needed on the motor control mechanisms underlying the observed carry-over effects within triplets as well as the possible causes of non-stationarity.

Alterations in the microstructure of white matter in children and adolescents with Tourette syndrome measured using tract-based spatial statistics and probabilistic tractography

Tourette syndrome (TS) is a neurodevelopmental disorder characterised by repetitive and intermittent motor and vocal tics. TS is thought to reflect fronto-striatal dysfunction and the aetiology of the disorder has been linked to widespread alterations in the functional and structural integrity of the brain. The aim of this study was to assess white matter (WM) abnormalities in a large sample of young patients with TS in comparison to a sample of matched typically developing control individuals (CS) using diffusion MRI. The study included 35 patients with TS (3 females; mean age: 14.0 ± 3.3) and 35 CS (3 females; mean age: 13.9 ± 3.3). Diffusion MRI data was analysed using tract-based spatial statistics (TBSS) and probabilistic tractography. Patients with TS demonstrated both marked and widespread decreases in axial diffusivity (AD) together with altered WM connectivity. Moreover, we showed that tic severity and the frequency of premonitory urges (PU) were associated with increased connectivity between primary motor cortex (M1) and the caudate nuclei, and increased information transfer between M1 and the insula, respectively. This is to our knowledge the first study to employ both TBSS and probabilistic tractography in a sample of young patients with TS. Our results contribute to the limited existing literature demonstrating altered connectivity in TS and confirm previous results suggesting in particular, that altered insular function contributes to increased frequency of PU.

Effects of a cognitive dual task on variability and local dynamic stability in sustained repetitive arm movements using principal component analysis: a pilot study

In many daily jobs, repetitive arm movements are performed for extended periods of time under continuous cognitive demands. Even highly monotonous tasks exhibit an inherent motor variability and subtle fluctuations in movement stability. Variability and stability are different aspects of system dynamics, whose magnitude may be further affected by a cognitive load. Thus, the aim of the study was to explore and compare the effects of a cognitive dual task on the variability and local dynamic stability in a repetitive bimanual task. Thirteen healthy volunteers performed the repetitive motor task with and without a concurrent cognitive task of counting aloud backwards in multiples of three. Upper-body 3D kinematics were collected and postural reconfigurations—the variability related to the volunteer’s postural change—were determined through a principal component analysis-based procedure. Subsequently, the most salient component was selected for the analysis of (1) cycle-to-cycle spatial and temporal variability, and (2) local dynamic stability as reflected by the largest Lyapunov exponent. Finally, end-point variability was evaluated as a control measure. The dual cognitive task proved to increase the temporal variability and reduce the local dynamic stability, marginally decrease endpoint variability, and substantially lower the incidence of postural reconfigurations. Particularly, the latter effect is considered to be relevant for the prevention of work-related musculoskeletal disorders since reduced variability in sustained repetitive tasks might increase the risk of overuse injuries.

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.

Neural Dynamics of Autistic Repetitive Behaviors and Fragile X Syndrome: Basal Ganglia Movement Gating and mGluR-Modulated Adaptively Timed Learning.

This article develops the iSTART neural model that proposes how specific imbalances in cognitive, emotional, timing, and motor processes that involve brain regions like prefrontal cortex, temporal cortex, amygdala, hypothalamus, hippocampus, and cerebellum may interact together to cause behavioral symptoms of autism. These imbalances include underaroused emotional depression in the amygdala/hypothalamus, learning of hyperspecific recognition categories that help to cause narrowly focused attention in temporal and prefrontal cortices, and breakdowns of adaptively timed motivated attention and motor circuits in the hippocampus and cerebellum. The article expands the model’s explanatory range by, first, explaining recent data about Fragile X syndrome (FXS), mGluR, and trace conditioning; and, second, by explaining distinct causes of stereotyped behaviors in individuals with autism. Some of these stereotyped behaviors, such as an insistence on sameness and circumscribed interests, may result from imbalances in the cognitive and emotional circuits that iSTART models. These behaviors may be ameliorated by operant conditioning methods. Other stereotyped behaviors, such as repetitive motor behaviors, may result from imbalances in how the direct and indirect pathways of the basal ganglia open or close movement gates, respectively. These repetitive behaviors may be ameliorated by drugs that augment D2 dopamine receptor responses or reduce D1 dopamine receptor responses. The article also notes the ubiquitous role of gating by basal ganglia loops in regulating all the functions that iSTART models.

Associations between parental broader autism phenotype and child autism spectrum disorder phenotype in the Study to Explore Early Development.

The autism spectrum disorder phenotype varies by social and communication ability and co-occurring developmental, behavioral, and medical conditions. Etiology is also diverse, with myriad potential genetic origins and environmental risk factors. Examining the influence of parental broader autism phenotype-a set of sub-clinical characteristics of autism spectrum disorder-on child autism spectrum disorder phenotypes may help reduce heterogeneity in potential genetic predisposition for autism spectrum disorder. We assessed the associations between parental broader autism phenotype and child phenotype among children of age 30-68 months enrolled in the Study to Explore Early Development (N = 707). Child autism spectrum disorder phenotype was defined by a replication of latent classes derived from multiple developmental and behavioral measures: Mild Language Delay with Cognitive Rigidity, Mild Language and Motor Delay with Dysregulation (e.g. anxiety/depression), General Developmental Delay, and Significant Developmental Delay with Repetitive Motor Behaviors. Scores on the Social Responsiveness Scale-Adult measured parent broader autism phenotype. Broader autism phenotype in at least one parent was associated with a child having increased odds of being classified as mild language and motor delay with dysregulation compared to significant developmental delay with repetitive motor behaviors (odds ratio: 2.44; 95% confidence interval: 1.16, 5.09). Children of parents with broader autism phenotype were more likely to have a phenotype qualitatively similar to broader autism phenotype presentation; this may have implications for etiologic research.