Cerebellar Volumes and Sensorimotor Behavior in Autism Spectrum Disorder

New Perspectives on Non-Invasive Cerebellar Stimulation for Social and Affective Functions in Children and Adolescents

Cerebellar dysfunction affects socio-affective abilities beyond motor control. Recent studies suggest that non-invasive cerebellar neurostimulation can modulate social cognition networks, offering potential therapeutic benefits for children with autism, ADHD, and mood disorders. However, its application in pediatrics remains largely unexplored. This review summarizes emerging pediatric research on cerebellar transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). We discuss their mechanisms, potential benefits, and safety considerations, highlighting preliminary findings that suggest feasibility and effectiveness. Ethical concerns and technical challenges related to pediatric neuroanatomy and stimulation parameters are also addressed. While early results are promising, further clinical trials and neurophysiological studies are essential to optimize protocols and confirm long-term efficacy. Advancing our understanding of cerebellar involvement in socio-affective functions could lead to innovative rehabilitation strategies for neurodevelopmental disorders.

Sensory-movement underpinnings of lifelong neurodivergence: getting a grip on autism

While the autism diagnosis emphasizes "deficits" in social communication, the article advances that sensory-movement differences underpin autism through a review of the following sources of evidence. This account critically challenges "autistic regression", with evidence that sensory-movement features appear by birth as the earliest signs of autism and underlie the behavioral differences used for diagnosis, which may reflect adaptations to inherent differences and misunderstandings from others. Sensory and motor differences are salient to autistic people, but they often go underrecognized by others. They cause cascading effects in infancy on behavior and communication through differences in sensorimotor learning, automatic imitation, eye contact, sensory perception, and interests. The article then explains how sensory processing differences may influence reduced perceptual narrowing, which involves a bottom-up information processing style grounded in the surrounding environment. Furthermore, this bottom-up processing may grow from reduced sensory integration in feedback loops potentially involving the cerebellum of the brain. The article then moves into implications for the widespread consequences of these inherent differences on quality of life. The article closes with implications for autism as a construct (including underestimated empathy and pain), testing the theory, providing sensory-sensitive support and acceptance of autistic people, and applications to diverse autistic people. The theory may apply particularly well to autistic women and girls, autistic people with speech divergence, autistic people with ADHD, and autistic people with co-occurring sensory and motor-related neurodivergences. Throughout the article, the theory also provides clinical, neurological, and experiential evidence for sensory and motor differences as lifelong, challenging the notion of "losing" (an) autism (diagnosis) as instead reflecting (risky and not necessarily "successful") camouflaging.

Oculomotor Function in Children and Adolescents with Autism, ADHD or Co-occurring Autism and ADHD

Oculomotor characteristics, including accuracy, timing, and sensorimotor processing, are considered sensitive intermediate phenotypes for understanding the etiology of neurodevelopmental conditions, such as autism and ADHD. Oculomotor characteristics have predominantly been studied separately in autism and ADHD. Despite the high rates of co-occurrence between these conditions, only one study has investigated oculomotor processes among those with co-occurring autism + ADHD. Four hundred and five (n = 405; 226 males) Australian children and adolescents aged 4 to 18 years (M = 9.64 years; SD = 3.20 years) with ADHD (n = 64), autism (n = 66), autism + ADHD (n = 146), or neurotypical individuals (n = 129) were compared across four different oculomotor tasks: visually guided saccade, anti-saccade, sinusoidal pursuit and step-ramp pursuit. Confirmatory analyses were conducted using separate datasets acquired from the University of Nottingham UK (n = 17 autism, n = 22 ADHD, n = 32 autism + ADHD, n = 30 neurotypical) and University of Kansas USA (n = 29 autism, n = 41 neurotypical). Linear mixed effect models controlling for sex, age and family revealed that children and adolescents with autism + ADHD exhibited increased variability in the accuracy of the final saccadic eye position compared to neurotypical children and adolescents. Autistic children and adolescents demonstrated a greater number of catch-up saccades during step-ramp pursuit compared to neurotypical children and adolescents. These findings suggest that select differences in saccadic precision are unique to autistic individuals with co-occurring ADHD, indicating that measuring basic sensorimotor processes may be useful for parsing neurodevelopment and clinical heterogeneity in autism.

Abnormalities in cerebellar subregions' volume and cerebellocerebral structural covariance in autism spectrum disorder

The cerebellum plays a crucial role in functions, including sensory-motor coordination, cognition, and emotional processing. Compared to the neocortex, the human cerebellum exhibits a protracted developmental trajectory. This delayed developmental timeline may lead to increased sensitivity of the cerebellum to external influences, potentially extending the vulnerability period for neurological disorders. Abnormal cerebellar development in individuals with autism has been confirmed, and these atypical cerebellar changes may affect the development of the neocortex. However, due to the heterogeneity of autism spectrum disorder (ASD), the regional changes in the cerebellum and cerebellocerebral structural relationship remain unknown. To address these issues, we utilized imaging methods optimized for the cerebellum and cerebrum on 817 individuals aged 5-18 years in the ABIDE II dataset. After FDR correction, significant differences between groups were found in the right crus II/VIIB and vermis VI-VII. Structural covariance analysis revealed enhanced structural covariance in individuals with autism between the cerebellum and parahippocampal gyrus, pars opercularis, and transverse temporal gyrus in the right hemisphere after FDR correction. Furthermore, the structural covariance between the cerebellum and some regions of the cerebrum varied across sexes. A significant increase in structural covariance between the cerebellum and specific subcortical structures was also observed in individuals with ASD. Our study found atypical patterns in the structural covariance between the cerebellum and cerebrum in individuals with autism, which suggested that the underlying pathological processes of ASD might concurrently affect these brain regions. This study provided insight into the potential of cerebellocerebral pathways as therapeutic targets for ASD.

Motor Signature Differences Between Autism Spectrum Disorder and Developmental Coordination Disorder, and Their Neural Mechanisms

Autism spectrum disorder (ASD) and Developmental Coordination Disorder (DCD) are distinct clinical groups with overlapping motor features. We attempted to (1) differentiate children with ASD from those with DCD, and from those typically developing (TD) (ages 8-17; 18 ASD, 16 DCD, 20 TD) using a 5-min coloring game on a smart tablet and (2) identify neural correlates of these differences. We utilized standardized behavioral motor assessments (e.g. fine motor, gross motor, and balance skills) and video recordings of a smart tablet task to capture any visible motor, behavioral, posture, or engagement differences. We employed machine learning analytics of motor kinematics during a 5-min coloring game on a smart tablet. Imaging data was captured using functional magnetic resonance imaging (fMRI) during action production tasks. While subject-rated motor assessments could not differentiate the two clinical groups, machine learning computational analysis provided good predictive discrimination: between TD and ASD (76% accuracy), TD and DCD (78% accuracy), and ASD and DCD (71% accuracy). Two kinematic markers which strongly drove categorization were significantly correlated with cerebellar activity. Findings demonstrate unique neuromotor patterns between ASD and DCD relate to cerebellar function and present a promising route for computational techniques in early identification. These are promising preliminary results that warrant replication with larger samples.

The Cerebellum-Ventral Tegmental Area Microcircuit and Its Implications for Autism Spectrum Disorder: A Narrative Review

The cerebellum has long been implicated in the etiopathogenesis of autism spectrum disorder (ASD), and emerging evidence suggests a significant contribution by reciprocal neural circuits between the cerebellum and ventral tegmental area (VTA) in symptom expression. This review provides a concise overview of morphological and functional alterations in the cerebellum and VTA associated with ASD symptoms, primarily focusing on human studies while also integrating mechanistic insights from animal models. We propose that cerebello-VTA circuit dysfunctional is a major contributor to ASD symptoms and that these circuits are promising targets for drugs and therapeutic brain stimulation methods.

Altered prefrontal and cerebellar parvalbumin neuron counts are associated with cognitive changes in male rats

Exposure to valproic acid (VPA), a common anti-seizure medication, in utero is a risk factor for autism spectrum disorder (ASD). People with ASD often display changes in the cerebellum, including volume changes, altered circuitry, and changes in Purkinje cell populations. ASD is also characterized by changes in the medial prefrontal cortex (mPFC), where excitatory/inhibitory balance is often altered. This study exposed rats to a high dose of VPA during gestation and assessed cognition and anxiety-like behaviors during young adulthood using a set-shifting task and the elevated plus maze. Inhibitory parvalbumin-expressing (PV +) neuron counts were assessed in the mPFC and cerebellar lobules VI and VII (Purkinje cell layers), which are known to modulate cognition. VPA males had increased PV + counts in crus I and II of lobule VII. VPA males also had decreased parvalbumin-expressing neuron counts in the mPFC. It was also found that VPA-exposed rats, regardless of sex, had increased parvalbumin-expressing Purkinje cell counts in lobule VI. In males, this was associated with impaired intra-dimensional shifting on a set-shifting task. Purkinje cell over proliferation may be contributing to the previously observed increase in volume of Lobule VI. These findings suggest that altered inhibitory signaling in cerebellar-frontal circuits may contribute to the cognitive deficits that occur within ASD.

Visual feedback and motor memory contributions to sustained motor control deficits in autism spectrum disorder across childhood and into adulthood

Background

Autistic individuals show deficits in sustained fine motor control which are associated with an over-reliance on visual feedback. Motor memory deficits also have been reported during sustained fine motor control in autism spectrum disorders (ASD). The development of motor memory and visuomotor feedback processes contributing to sustained motor control issues in ASD are not known. The present study aimed to characterize age-related changes in visual feedback and motor memory processes contributing to sustained fine motor control issues in ASD.

Methods

Fifty-four autistic participants and 31 neurotypical (NT) controls ages 10-25 years completed visually guided and memory guided sustained precision gripping tests by pressing on force sensors with their dominant hand index finger and thumb. For visually guided trials, participants viewed a stationary target bar and a force bar that moved upwards with increased force for 15s. During memory guided trials, the force bar was visible for 3s, after which participants attempted to maintain their force output without visual feedback for another 12s. To assess visual feedback processing, force accuracy, variability (standard deviation), and regularity (sample entropy) were examined. To assess motor memory, force decay latency, slope, and magnitude were examined during epochs without visual feedback.

Results

Relative to NT controls, autistic individuals showed a greater magnitude and steeper slope of force decay during memory guided trials. Across conditions, the ASD group showed reduced force accuracy (β = .41, R2 = 0.043, t79.3=2.36, p = 0.021) and greater force variability (β=-2.16, R2 = .143, t77.1=-4.04, p = 0.0001) and regularity (β=-.52, R2 = .021, t77.4=-2.21, p = 0.030) relative to controls at younger ages, but these differences normalized by adolescence (age × group interactions). Lower force accuracy and greater force variability during visually guided trials and steeper decay slope during memory guided trials were associated with overall autism severity.

Conclusions

Our findings that autistic individuals show a greater rate and magnitude of force decay than NT individuals following the removal of visual feedback indicate that motor memory deficits contribute to fine motor control issues in ASD. Findings that sensorimotor differences in ASD were specific to younger ages suggest delayed development across multiple motor control processes.

Association of polygenic scores for autism with volumetric MRI phenotypes in cerebellum and brainstem in adults

Previous research on autism spectrum disorders (ASD) have showed important volumetric alterations in the cerebellum and brainstem. Most of these studies are however limited to case-control studies with small clinical samples and including mainly children or adolescents. Herein, we aimed to explore the association between the cumulative genetic load (polygenic risk score, PRS) for ASD and volumetric alterations in the cerebellum and brainstem, as well as global brain tissue volumes of the brain among adults at the population level. We utilized the latest genome-wide association study of ASD by the Psychiatric Genetics Consortium (18,381 cases, 27,969 controls) and constructed the ASD PRS in an independent cohort, the UK Biobank. Regression analyses controlled for multiple comparisons with the false-discovery rate (FDR) at 5% were performed to investigate the association between ASD PRS and forty-four brain magnetic resonance imaging (MRI) phenotypes among ~ 31,000 participants. Primary analyses included sixteen MRI phenotypes: total volumes of the brain, cerebrospinal fluid (CSF), grey matter (GM), white matter (WM), GM of whole cerebellum, brainstem, and ten regions of the cerebellum (I_IV, V, VI, VIIb, VIIIa, VIIIb, IX, X, CrusI and CrusII). Secondary analyses included twenty-eight MRI phenotypes: the sub-regional volumes of cerebellum including the GM of the vermis and both left and right lobules of each cerebellar region. ASD PRS were significantly associated with the volumes of seven brain areas, whereby higher PRS were associated to reduced volumes of the whole brain, WM, brainstem, and cerebellar regions I-IV, IX, and X, and an increased volume of the CSF. Three sub-regional volumes including the left cerebellar lobule I-IV, cerebellar vermes VIIIb, and X were significantly and negatively associated with ASD PRS. The study highlights a substantial connection between susceptibility to ASD, its underlying genetic etiology, and neuroanatomical alterations of the adult brain.

Microstructural neural correlates of maximal grip strength in autistic children: the role of the cortico-cerebellar network and attention-deficit/hyperactivity disorder features

Introduction

Maximal grip strength, a measure of how much force a person's hand can generate when squeezing an object, may be an effective method for understanding potential neurobiological differences during motor tasks. Grip strength in autistic individuals may be of particular interest due to its unique developmental trajectory. While autism-specific differences in grip-brain relationships have been found in adult populations, it is possible that such differences in grip-brain relationships may be present at earlier ages when grip strength is behaviorally similar in autistic and non-autistic groups. Further, such neural differences may lead to the later emergence of diagnostic-group grip differences in adolescence. The present study sought to examine this possibility, while also examining if grip strength could elucidate the neuro-motor sources of phenotypic heterogeneity commonly observed within autism.

Methods

Using high resolution, multi-shell diffusion, and quantitative R1 relaxometry imaging, this study examined how variations in key sensorimotor-related white matter pathways of the proprioception input, lateral grasping, cortico-cerebellar, and corticospinal networks were associated with individual variations in grip strength in 68 autistic children and 70 non-autistic (neurotypical) children (6-11 years-old).

Results

In both groups, results indicated that stronger grip strength was associated with higher proprioceptive input, lateral grasping, and corticospinal (but not cortico-cerebellar modification) fractional anisotropy and R1, indirect measures concordant with stronger microstructural coherence and increased myelination. Diagnostic group differences in these grip-brain relationships were not observed, but the autistic group exhibited more variability particularly in the cortico-cerebellar modification indices. An examination into the variability within the autistic group revealed that attention-deficit/hyperactivity disorder (ADHD) features moderated the relationships between grip strength and both fractional anisotropy and R1 relaxometry in the premotor-primary motor tract of the lateral grasping network and the cortico-cerebellar network tracts. Specifically, in autistic children with elevated ADHD features (60% of the autistic group) stronger grip strength was related to higher fractional anisotropy and R1 of the cerebellar modification network (stronger microstructural coherence and more myelin), whereas the opposite relationship was observed in autistic children with reduced ADHD features.

Discussion

Together, this work suggests that while the foundational elements of grip strength are similar across school-aged autistic and non-autistic children, neural mechanisms of grip strength within autistic children may additionally depend on the presence of ADHD features. Specifically, stronger, more coherent connections of the cerebellar modification network, which is thought to play a role in refining and optimizing motor commands, may lead to stronger grip in children with more ADHD features, weaker grip in children with fewer ADHD features, and no difference in grip in non-autistic children. While future research is needed to understand if these findings extend to other motor tasks beyond grip strength, these results have implications for understanding the biological basis of neuromotor control in autistic children and emphasize the importance of assessing co-occurring conditions when evaluating brain-behavior relationships in autism.

Population-wide cerebellar growth models of children and adolescents

In the past, the cerebellum has been best known for its crucial role in motor function. However, increasingly more findings highlight the importance of cerebellar contributions in cognitive functions and neurodevelopment. Using a total of 7240 neuroimaging scans from 4862 individuals, we describe and provide detailed, openly available models of cerebellar development in childhood and adolescence (age range: 6-17 years), an important time period for brain development and onset of neuropsychiatric disorders. Next to a traditionally used anatomical parcellation of the cerebellum, we generated growth models based on a recently proposed functional parcellation. In both, we find an anterior-posterior growth gradient mirroring the age-related improvements of underlying behavior and function, which is analogous to cerebral maturation patterns and offers evidence for directly related cerebello-cortical developmental trajectories. Finally, we illustrate how the current approach can be used to detect cerebellar abnormalities in clinical samples.

Inhibition functions can be improved in children with autism spectrum disorders: An eye-tracking study

Cognitive remediation therapy interventions could improve cognitive functioning in subjects with autism. To investigate the benefit of a short cognitive training rehabilitation in children with autism spectrum disorder (ASD) on pursuit and fixation performances. We recruited two groups (G1 and G2) of 30 children with ASD, sex-, IQ- and age-matched (mean 11.6 ± 0.5 years), and pursuit and fixation eye movements were recorded twice at T1 and T2. Between T1 and T2, a 10-min cognitive training was performed by the G1 group only, whereas the G2 group had a 10-min of rest. For all children with ASD enrolled in the study, there was a positive correlation between restricted and repetitive behaviour scores of both Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) and the number of saccades recorded during the fixation task at T1. At T1, oculomotor performances were similar for both groups of ASD children (G1 and G2). At T2, we observed a significant reduction in the number of saccades made during both pursuit and fixation tasks. Our findings underlined the importance to promote cognitive training rehabilitation for children with ASD, leading to a better performance in inhibitory and attention functioning responsible for pursuit and fixation eye movement's performance.

Functional connectivity of cortical-cerebellar networks in relation to sensorimotor behavior and clinical features in autism spectrum disorder

Sensorimotor issues are present in the majority of individuals with autism spectrum disorder (ASD) and are associated with core symptoms. The neural systems associated with these impairments remain unclear. Using a visually guided precision gripping task during functional magnetic resonance imaging, we characterized task-based connectivity and activation of cortical, subcortical, and cerebellar visuomotor networks. Participants with ASD (n = 19; ages 10-33) and age- and sex-matched neurotypical controls (n = 18) completed a visuomotor task at low and high force levels. Relative to controls, individuals with ASD showed reduced functional connectivity of right primary motor-anterior cingulate cortex and left anterior intraparietal lobule (aIPL)-right Crus I at high force only. At low force, increased caudate, and cerebellar activation each were associated with sensorimotor behavior in controls, but not in ASD. Reduced left aIPL-right Crus I connectivity was associated with more severe clinically rated ASD symptoms. These findings suggest that sensorimotor problems in ASD, particularly at high force levels, involve deficits in the integration of multimodal sensory feedback and reduced reliance on error-monitoring processes. Adding to literature positing that cerebellar dysfunction contributes to multiple developmental issues in ASD, our data implicate parietal-cerebellar connectivity as a key neural marker underlying both core and comorbid features of ASD.