[Neurological soft signs in pervasive developmental disorders]

Common vs. Distinct Visuomotor Control Deficits in Autism Spectrum Disorder and Schizophrenia

Autism spectrum disorder (ASD) and schizophrenia (SCZ) are neurodevelopmental disorders with partly overlapping clinical phenotypes including sensorimotor impairments. However, direct comparative studies on sensorimotor control across these two disorders are lacking. We set out to compare visuomotor upper limb impairment, quantitatively, in ASD and SCZ. Patients with ASD (N = 24) were compared to previously published data from healthy control participants (N = 24) and patients with SCZ (N = 24). All participants performed a visuomotor grip force-tracking task in single and dual-task conditions. The dual-task (high cognitive load) presented either visual distractors or required mental addition during grip force-tracking. Motor inhibition was measured by duration of force release and from principal component analysis (PCA) of the participant's force-trajectory. Common impairments in patients with ASD and SCZ included increased force-tracking error in single-task condition compared to controls, a further increase in error in dual-task conditions, and prolonged duration of force release. These three sensorimotor impairments were found in both patient groups. In contrast, distinct impairments in patients with ASD included greater error under high cognitive load and delayed onset of force release compared to SCZ. The PCA inhibition component was higher in ASD than SCZ and controls, correlated to duration of force release, and explained group differences in tracking error. In conclusion, sensorimotor impairments related to motor inhibition are common to ASD and SCZ, but more severe in ASD, consistent with enhanced neurodevelopmental load in ASD. Furthermore, impaired motor anticipation may represent a further specific impairment in ASD. Autism Res 2020, 13: 885-896. © 2020 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Autism spectrum disorder (ASD) and schizophrenia (SCZ) are neurodevelopmental disorders with partly overlapping and partly distinct clinical symptoms. Sensorimotor impairments rank among these symptoms, but it is less clear whether they are shared or distinct. In this study, we showed using a grip force task that sensorimotor impairments related to motor inhibition are common to ASD and SCZ, but more severe in ASD. Impaired motor anticipation may represent a further specific impairment in ASD.

Neurological soft signs, but not theory of mind and emotion recognition deficit distinguished children with ADHD from healthy control

Attention Deficit Hyperactivity Disorder (ADHD) is associated with social cognition impairment, executive dysfunction and motor abnormalities, consisting in the persistence of neurological soft signs (NSS). Theory of mind (ToM) and emotion recognition (ER) deficit of children with ADHD have been interpreted as a consequence of their executive dysfunction, particularly inhibitory control deficit. To our knowledge, there are not studies that evaluate the possible correlation between the ToM and ER deficit and NSS in the population with ADHD, while this association has been studied in other psychiatric disorders, such as schizophrenia. Therefore, the aim of this study was to evaluate ToM and ER and NSS in a sample of 23 drug-naïve children with ADHD and a sample of 20 healthy children and the possible correlation between social cognition dysfunction and NSS in ADHD. Our findings suggest that ToM and ER dysfunction is not a constant feature in the population with ADHD, while NSS confirmed as a markers of atypical neurodevelopment and predictors of the severity of functional impairment in children with ADHD.

Socioeconomic disadvantage and neural development from infancy through early childhood

BACKGROUND

Early social experiences are believed to shape neurodevelopment, with potentially lifelong consequences. Yet minimal evidence exists regarding the role of the social environment on children's neural functioning, a core domain of neurodevelopment.

METHODS

We analysed data from 36 443 participants in the United States Collaborative Perinatal Project, a socioeconomically diverse pregnancy cohort conducted between 1959 and 1974. Study outcomes included: physician (neurologist or paediatrician)-rated neurological abnormality neonatally and thereafter at 4 months and 1 and 7 years; indicators of neurological hard signs and soft signs; and indicators of autonomic nervous system function.

RESULTS

Children born to socioeconomically disadvantaged parents were more likely to exhibit neurological abnormalities at 4 months [odds ratio (OR) = 1.20; 95% confidence interval (CI) = 1.06, 1.37], 1 year (OR = 1.35; CI = 1.17, 1.56), and 7 years (OR = 1.67; CI = 1.48, 1.89), and more likely to exhibit neurological hard signs (OR = 1.39; CI = 1.10, 1.76), soft signs (OR = 1.26; CI = 1.09, 1.45) and autonomic nervous system dysfunctions at 7 years. Pregnancy and delivery complications, themselves associated with socioeconomic disadvantage, did not account for the higher risks of neurological abnormalities among disadvantaged children.

CONCLUSIONS

Parental socioeconomic disadvantage was, independently from pregnancy and delivery complications, associated with abnormal child neural development during the first 7 years of life. These findings reinforce the importance of the early environment for neurodevelopment generally, and expand knowledge regarding the domains of neurodevelopment affected by environmental conditions. Further work is needed to determine the mechanisms linking socioeconomic disadvantage with children's neural functioning, the timing of such mechanisms and their potential reversibility.

[Formula: see text]Current knowledge on motor disorders in children with autism spectrum disorder (ASD)

Motor symptomatology in autism is currently poorly understood, and still not included in the autism spectrum disorder (ASD) diagnostic criteria, although some studies suggest the presence of motor disturbances in this syndrome. We provide here a literature review on early motor symptoms in autism, focusing on studies on psychomotor issues (tone, postural control, manual dexterity, handedness, praxis). The approach adopted in research to study altered motor behaviors is generally global and there is no detailed semiology of the motor or neuromotor disorders observed in people with ASD. This global approach does not enable understanding of the neuro-developmental mechanisms involved in ASD. Identification of clinical neuro-psychomotor profiles in reference to a standard would help to better understand the origin and the nature of the disorders encountered in ASD, and would thus give new directions for treatment.

Neurological soft signs in children with attention deficit hyperactivity disorder: Their relationship to executive function and parental neurological soft signs

The correlations between neurological soft signs (NSS) in children with attention deficit hyperactivity disorder (ADHD) and their executive function, symptoms of inattention, and hyperactivity-impulsivity and the NSS of their parents remain unclear. This study aimed to examine: (1) the prevalence of NSS in children with ADHD and their parents; (2) the correlation between the NSS of children with ADHD and the NSS of their parents; and (3) the correlation between the NSS of children with ADHD and their executive function and symptoms. NSS were assessed with the Cambridge Neurological Inventory (CNI) in 57 children with ADHD (and 80 parents) and 60 healthy children (and 75 parents). Executive function was measured with the Behavioral Rating Inventory of Executive Function (BRIEF). Children with ADHD and their parents had significantly higher NSS than normal children and their parents, respectively, and the NSS of children with ADHD were correlated more strongly with the NSS of their fathers than their mothers. No correlation was found between NSS and BRIEF executive function, but Disinhibition in children with ADHD was significantly correlated with hyperactivity-impulsivity symptoms. Paternal and maternal NSS provided different predictions for child NSS. It may be that NSS are more likely to be genetically transmitted by fathers.

An exploratory study of the relationship between neurological soft signs and theory of mind deficits in schizophrenia

Indirect evidence suggests partially common pathogenetic mechanisms for Neurological Soft Signs (NSS), neurocognition, and social cognition in schizophrenia. However, the possible association between NSS and mentalizing impairments has not yet been examined. In the present study, we assessed the ability to attribute mental states to others in patients with schizophrenia and predicted that the presence of theory of mind deficits would be significantly related to NSS. Participants were 90 clinically stable patients with a DSM-IV diagnosis of schizophrenia. NSS were assessed using the Neurological Evaluation Scale (NES). Theory of mind deficits were assessed using short verbal stories designed to measure false belief understanding. The findings of the study confirmed our hypothesis. Impaired sequencing of complex motor acts was the only neurological abnormality correlated with theory of mind deficits. By contrast, sensory integration, motor coordination and the NES Others subscale had no association with patients׳ ability to pass first- or second-order false belief tasks. If confirmed by future studies, the current findings provide the first preliminary evidence for the claim that specific NSS and theory of mind deficits may reflect overlapping neural substrates.

Examination of neurological subtle signs in ADHD as a clinical tool for the diagnosis and their relationship to spatial working memory

BACKGROUND

  Neurological subtle signs (NSS) are minor neurological abnormalities that have been shown to be increased in a number of neurodevelopmental conditions. For attention deficit/hyperactivity disorder (ADHD), it remains unclear whether NSS may aid the clinical diagnostic process.

METHODS

  This study explored the association of total and specific domains of NSS in 1,055 children and adolescents with ADHD compared to 130 age-matched typically developing participants; the relationship between NSS and Spatial Working Memory (SWM) as a cognitive process integrally involved in ADHD was also assessed. To determine the diagnostic and predictive efficiency of NSS, a receiver operating curve analysis was performed and the area under the curve (AUC) quantified. The best discriminant points for differentiating between ADHD and typically developing participants and the predictive power of NSS for SWM impairment in ADHD young people were also calculated.

RESULTS

  Area under the curves for total NSS, smoothness/accuracy, cerebellar signs and choreo-athetoid movements scores were considered good (.84, .79, .74 and .73 respectively), and the results remained after controlling for gender and IQ. A total score of 13 or over on the Scored Developmental Neurological Examination proved to be a good threshold point for differentiating between the ADHD and typically developing participants. For ADHD children, the AUC of total NSS to distinguish between those below 25th and above 75th percentile were .77 and .73 for Spatial Span and for Between Search Errors respectively (the two SWM-dependent measures examined).

CONCLUSIONS

  This study provides evidence suggesting that NSS may aid the clinical evaluation of a child or adolescent with ADHD. In children and adolescents with ADHD, NSS are associated with difficulties in SWM, specifically the Spatial Span and Between Search Error components.

Impaired social interactions and motor learning skills in tuberous sclerosis complex model mice expressing a dominant/negative form of tuberin

Tuberous sclerosis complex (TSC) is a genetic disorder characterized by the development of hamartomas in multiple organs. Neurological manifestation includes cortical dysplasia, epilepsy, and cognitive deficits such as mental impairment and autism. We measured the impact of TSC2-GAP mutations on cognitive processes and behavior in, ΔRG transgenic mice that express a dominant/negative TSC2 that binds to TSC1, but has mutations affecting its GAP domain and its rabaptin-5 binding motif, resulting in inactivation of the TSC1/2 complex. We performed a behavioral characterization of the ΔRG transgenic mice and found that they display mild, but significant impairments in social behavior and rotarod motor learning. These findings suggest that the ΔRG transgenic mice recapitulate some behavioral abnormalities observed in human TSC patients.