The Cerebellum

Spinocerebellar ataxia type 7 (SCA7) is a rare neurodegenerative disorder characterized by progressive cerebellar ataxia and visual impairment. We investigated longitudinal changes in resting-state functional connectivity and their clinical associations. Resting-state functional MRI was acquired from 16 individuals with SCA7 and 16 age- and sex-matched healthy controls across three visits over 24 months. Network-to-network functional connectivity was quantified, and machine-learning models were trained using functional connectivity features. SCA7 showed lower MoCA (p = 0.045) and MMSE (p = 0.025) scores and progressive worsening of ataxia (SARA, p < 0.001). Significant Group x Visit interactions were observed for Visual-Default Mode (p = 0.012) and Somatomotor-Cerebellar Dorsal Attention connectivity (p = 0.038). Functional connectivity abnormalities involved cortical, cortico-cerebellar, and cerebellar networks that became more widespread at the final follow-up assessment, with the visual network emerging as the most consistently affected system across analyses. Functional connectivity abnormalities were associated with cognitive performance (MMSE: r = -0.62, p = 0.01) and disease severity (SARA: r = 0.589, p = 0.016). Functional connectivity features accurately classified SCA7 and healthy controls (accuracy = 96.4%, F1 = 0.969). These findings support resting-state functional connectivity as a candidate biomarker warranting further validation in larger, independent cohorts.

Background: Infants with extremely low birth weight (ELBW) are at high risk for neurodevelopmental impairment, but the relationship between cerebellar structure and later developmental outcome remains incompletely defined. Methods: In this retrospective single-center study, we examined total cerebellar volume on clinically acquired brain magnetic resonance imaging (MRI) in ELBW infants while accounting for postmenstrual age (PMA) at imaging. Results: Of 65 infants screened, 42 were included. Mean gestational age at birth was 25.54 {+/-} 1.68 weeks, mean birth weight was 733.2 {+/-} 118.7 g, and mean PMA at MRI was 43.02 {+/-} 6.53 weeks (range, 31.57--68.00). Mean cerebellar volume was 22.17 {+/-} 9.63 cm. Independently adjudicated developmental outcomes comprised normal development in 16 infants, isolated or specific impairment in 12, and moderate/severe impairment in 14. Unadjusted cerebellar volumes did not differ across developmental groups (P = 0.490) or qualitative MRI categories (P = 0.875). However, the PMA-by-developmental-category interaction was significant (P = 0.002), with estimated cross-sectional slopes of 1.72, 1.56, and 0.39 cm per week, respectively. The interaction remained significant within 36--46 weeks PMA (n = 29; P = 0.011) and after adjustment for small-for-gestational-age (SGA) status. Sensitivity analyses indicated uncertainty in the stability of the interaction. Conclusions: These findings suggest that age-informed cerebellar volumetric patterns may provide developmental information not evident from average volumes alone and support prospective validation with standardized imaging and developmental assessments. As a result, cerebellar volumes obtained early in life may hold prognostic information for ELBW infants.

Background: Transcranial direct current stimulation (tDCS) is increasingly used as an adjunct to rehabilitation for young people with cerebral palsy (CP), yet considerable variability exists in clinical response. Individualised electric field modelling provides an opportunity to estimate the distribution of electrical fields generated by the stimulation delivered to the brain and explore potential relationships with functional outcomes. Methods: Structural MRI scans from nineteen participants (10-16 years) from a previously published randomised controlled trial (ISRCTN74235136) investigating the effects of tDCS combined with motor training, underwent participant-specific finite element modelling using SimNIBS. Electric field strength was quantified within anatomically defined motor regions of interest, including the primary motor cortex (M1), dorsal premotor cortex (PMd), supplementary motor area (SMA), and a combined motor network. Global grey matter electric field metrics and stimulation focality were also extracted. Results: Estimated electric field strength differed significantly across motor regions (p<0.001), with PMd receiving significantly greater stimulation than both M1 and SMA. Electric field strength within a control region (primary visual cortex) was significantly lower than within M1 (p<0.001). Despite inter-individual variability in regional and global electric field metrics, no significant associations were observed between estimated electric field strength or focality and changes in function following intervention. Conclusion: Individualised electric field modelling demonstrated that an M1-targeted tDCS montage preferentially stimulated PMd rather than M1 in young people with CP. These findings highlight the importance of subject-specific modelling when characterising current distribution and suggest that variability in electric field strength alone does not explain variability in behavioural response.

Autism spectrum disorder is a neurodevelopmental disorder with both genetic and environmental contributors. SCN2A, the gene which encodes the alpha subunit of the voltage-gated sodium channel Nav1.2, is a known monogenetic risk factor for autism spectrum disorder. The cerebellum is frequently implicated in autism spectrum disorder and other neurodevelopmental disorders but has largely been unexplored in relation to SCN2A variants, especially from a developmental perspective. Nav1.2 is highly expressed within the cerebellum, specifically within cerebellar granule neurons, where it helps to drive action potential generation and propagation. Cerebellar granule neuron activity and maturation is crucial for shaping the development and morphology of the rest of the cerebellar cortex. Here we investigated early-postnatal cerebellar development in two mouse models carrying patient-derived SCN2A premature termination codon variants, Scn2a-p.Y84X and -p.R1627X. Overall, both Scn2a premature termination codon variant mouse lines displayed largely normal physical development and unaffected non-cerebellar developmental milestones. Scn2aY84X/+ mice, but not Scn2aR1627X/+ mice, demonstrated alterations in cerebellar-driven motor behaviors, specifically faster performance in the surface righting reflex and cliff avoidance compared to wildtype littermates. Coinciding with the behavioral findings, Scn2a variants had divergent and age-dependent effects on cerebellar glutamatergic presynaptic marker expression, indicating that some, but not all, Scn2a premature termination codons impair glutamatergic synapse development. Both Scn2a variants exhibited changes to cerebellar cytoarchitecture, such as reductions in Purkinje cell density and soma size, which was more prominent in Scn2aY84X/+ mice, and faster migration of cerebellar granule neurons from the external granule layer to the internal, indicating a possible shift in the timing of cerebellar maturation. Our results situate the cerebellum as an early site for SCN2A pathophysiology and establish that cerebellar consequences of SCN2A premature termination codon variants may be position- and age-dependent, suggesting that influences beyond simple heterozygous loss of Nav1.2 drive phenotypes. Our characterization of how Scn2a premature termination codon variants differentially impair cerebellar development may help explain the heterogeneity of clinical presentations of SCN2A loss of function variants and potentially inform upon the timing of therapeutic intervention.

The cerebellar nuclei (CN) has demonstrated its influence on cognitive behavior via the cerebello-cortico circuit, yet the role of CN critical period mechanisms and how they may influence cognitive behavior, such as parvalbumin (PV) expressing interneurons enwrapped by perineuronal nets (PNNs), is still unclear. Therefore, we investigated the role of the lateral CN (LCN) PV cell calcium activity while animals performed a visual discrimination touchscreen cognitive task. All animals received the PV cell calcium indicator GCaMP6f at postnatal day 21 (P21). We targeted the LCN critical period by manipulating neural activity in male mice using the inhibitory Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) from postnatal day 21 to 35 or by injecting an Hapln1-AAV vector to selectively target LCN PNN development. After animals completed the visual discrimination task, cerebellar tissue was collected for viral recovery and antibody staining for PNN components, Hapln1 and aggrecan. Results revealed DREADD animals showed improved reversal learning, an increase in calcium response to learning-related activity and altered PNN expression (Hapln1 and aggrecan). Hapln1 treated animals displayed a decrease in final day acquisition performance, lower reversal performance compared to DREADD groups, a decrease in reversal calcium learning-related activity, and an increase in PNN expression (Hapln1). Together, these data provide further evidence of LCN mechanisms associated with learning as well as the importance of understanding region-specific critical periods of plasticity.

Marinesco-Sjogren syndrome is a rare early-onset multisystem disorder characterized primarily by cerebellar ataxia and myopathy and caused by loss-of-function mutations in SIL1. No disease-modifying therapy is available. We investigated whether adeno-associated virus (AAV)-mediated gene therapy could prevent neurological and muscular disease in the woozy mouse model of SIL1 deficiency. Neonatal mice received intracerebroventricular injections of AAV-PHP.eB vectors expressing SIL1 under the control of either a ubiquitous or a Purkinje cell-specific promoter. Vehicle-treated woozy mice developed progressive motor impairment accompanied by extensive Purkinje cell degeneration, thinning of the cerebellar molecular layer, marked astrogliosis and activation of endoplasmic reticulum stress pathways. In contrast, AAV-SIL1 treatment prevented the onset of ataxia and substantially preserved cerebellar architecture, including Purkinje cells and molecular-layer thickness, while reducing astrogliosis and endoplasmic reticulum stress. Selective restoration of SIL1 expression in Purkinje cells was sufficient to rescue motor performance, supporting a major cell-autonomous contribution of Purkinje cell dysfunction to cerebellar disease. Therapeutic benefit was maintained throughout the 26-week observation period, the longest time point examined, with treated mice remaining behaviorally indistinguishable from heterozygous controls. AAV-SIL1 treatment also improved muscle function and markedly attenuated skeletal muscle pathology, with transgenic SIL1 expression in muscle reaching levels comparable to those in heterozygous controls. These findings provide proof-of-principle that AAV-mediated SIL1 gene therapy can prevent the neurological and muscular manifestations of Marinesco-Sjogren syndrome and identify Purkinje cells as a critical cellular target for preventing cerebellar dysfunction.

Background: Response to Comprehensive Behavioral Intervention for Tics (CBIT), the first-line treatment for tic disorders, is suboptimal. We conducted Phase 1 of a two-phase, milestone-driven trial to determine if augmenting CBIT with repetitive transcranial magnetic stimulation (TMS) to supplementary motor area (SMA) could safely engage targeted sensorimotor circuitry and improve tic controllability. Methods: In a 3-arm, double-blind, sham-controlled randomized trial (NCT04578912), 50 youth (ages 12-21) with moderate-to-severe tics received 10 sessions of either 1Hz rTMS, continuous theta burst stimulation (cTBS), or sham stimulation to the SMA, immediately followed by CBIT. Primary outcomes were safety, feasibility, and neural target engagement (fMRI SMA activation and resting-state functional connectivity [RSFC]). Secondary outcomes included change in tic controllability, tic frequency at rest, and urges. Results: The CBIT+TMS intervention was safe and feasible (96% completion). Treatment-related adverse events were mild-to-moderate and occurred more frequently in the 1Hz rTMS group (27% of sessions) vs. cTBS (14.7%) and sham (11.3%). While task-based SMA activation remained unchanged, cTBS demonstrated robust neural target engagement, reducing SMA-primary motor cortex (M1) RSFC and putamen-M1 RSFC. Conversely, 1Hz rTMS blunted the cortico-striatal connectivity reductions observed in the sham group. All groups exhibited significant reductions in tic frequency and improved controllability. Premonitory urges increased in the 1Hz rTMS group but decreased in sham and cTBS. Conclusions: SMA-directed cTBS is a safe, feasible augmentation that may amplify the neural effects of CBIT on sensorimotor circuitry. Findings identify cTBS as the preferred stimulation regimen for future efficacy testing. Clinical Trial Registration: ClinicalTrials.gov; Identifier: NCT04578912.

Background: Infant muscle tone reflects early central nervous system integrity and has been associated with later motor and cognitive development, including autism traits. The cerebellum regulates both motor control and higher-order socio-cognitive functions and has been repeatedly implicated in autism, but its role in linking infant muscle tone to adolescent autistic traits has not previously been studied in a large, prospective population cohort. Methods: We used data from the prospective Generation R Study. Infant muscle tone (hypotonia and hypertonia) was assessed via Prechtl examination, and third-trimester fetal transcerebellar diameter was measured using ultrasound n=6,842). Cerebellar morphology at ages 6, 10, and 14 years (n=4,861) was measured using structural MRI. Linear mixed-effects models tested associations between infant muscle tone and 35 anatomical and 10 functional cerebellar regions. Causal mediation models tested whether cerebellar volume mediated associations between infant muscle tone and adolescent autistic traits at age 14 (Social Responsiveness Scale). Results: Hypotonia predicted larger vermis IX volumes across childhood (beta=0.037, pFDR =0.043). Hypertonia showed an age-dependent association with left lateral lobule IX (beta=-0.0027, pFDR =0.041), with differences diminishing with age. Third-trimester transcerebellar diameter did not predict postnatal muscle tone. Given its significant main effect, vermis IX volume was tested as a mediator, but did not mediate the pathway to adolescent autistic traits. However, infant hypotonia showed a small direct association with elevated autistic traits at age 14, specific to girls (beta=0.0255, p=0.020). Conclusions: Infant muscle tone is associated with localized differences in cerebellar volumes. These associations are specific to vermal and left hemispheric lobule IX, a region commonly implicated in spinocerebellar postural control, axial stability, and higher-order sensorimotor integration. Furthermore, infant muscle tone was not predicted by prenatal cerebellar diameter, and cerebellar volumes did not mediate the association between infant hypotonia and adolescent autistic traits in our study. Future research should further investigate these findings in clinical populations, integrating longitudinal whole-brain, multi-modal imaging to clarify the association between infant muscle tone, the cerebellar functioning, and autistic traits.

The Visual Word Form Area (VWFA), located in ventral occipitotemporal cortex, plays a critical role in skilled reading. Researchers have theorized that the VWFA develops in its specific anatomical location due to the convergence of major white matter tracts and proximity to functionally similar regions. This suggests that precise anatomical positioning may be crucial for optimal VWFA function. Previous research has identified several functional differences in this region between typical and struggling readers (i.e. dyslexia): struggling readers show weaker text-selective responses and often exhibit a smaller or even absent VWFA. However, it remains unexplored whether the precise anatomical location of this region also differs between typical and struggling readers. We tested whether VWFA anatomy differs between children with and without dyslexia (N=87). Participants completed a functional localizer, which we used to manually define the VWFA in each individuals native anatomy. We examined whether: (1) VWFA anatomical location relates to reading ability, (2) children with dyslexia show greater variability in VWFA location compared to typical readers, and (3) VWFA location with respect to white matter tracts relates to reading ability. Results reveal that, despite being smaller in children with dyslexia, there is no relationship between VWFA location and reading ability. Specifically, individual VWFA location relative to anatomy, relative to others VWFAs, and relative to white matter tracts, is not related to reading ability. These findings suggest that while the VWFAs general anatomy may be facilitated by development, its precise location remains stable and unrelated to reading proficiency.

The cerebellum supports a wide range of motor and non-motor behaviors, yet the specific cerebellar regions and neuronal populations underlying this functional diversity remain poorly understood. Here, we mapped patterns of immediate early gene activation in the cerebellar cortex during the accelerating rotarod task, an established form of cerebellum-dependent motor learning. Using the immediate early gene c-Fos to identify cells active during the task, we found significantly greater activation throughout the vermis and in crus I of the hemispheres, specifically within the molecular and granule cell layers, compared to naive controls. However, a second control group, which was exposed to the rotarod apparatus but not placed on the rotating rod, revealed similar patterns of c-Fos expression, suggesting that novelty contributed substantially to the observed activation. To separate this potential novelty signal from the motor component of the task, mice were habituated to the apparatus prior to testing. This habituation resulted in an overall decrease in c-Fos expression across cerebellar lobules, with significant motor activity-related differences found in the anterior vermis. Finally, to determine how learning influences c-Fos expression patterns, mice were subjected to a multi-day motor learning paradigm in which genetic tagging of c-Fos-expressing neurons was performed on day 1, followed by c-Fos immunostaining on day 5. We found that, in mice that had learned the task, there was no significant increase in c-Fos signal above naive controls, indicating that rotarod task performance no longer recruited the same level of cerebellar cortical activity, consistent with a potentially reduced role for the cerebellar cortex once the task is well learned. Overall, these findings reveal distinct patterns of activation associated with novelty, motor behaviour, and learning, providing a framework for linking behavior to regional cerebellar function.

Computer mouse weight has been proposed to influence human motor performance, but existing evidence comes largely from small, short-duration controlled studies, leaving its relationship to performance during naturalistic gameplay unresolved. We analyzed one-week skill improvement in Aimlabs, a popular first-person shooter aim-training and assessment platform, among 9,067 players whose telemetry recorded a mouse-model change (switchers) during self-directed game use, using a 21-day baseline and 7-day follow-up; 4,991 players with a single mouse model (non-switchers) observed over matched pseudo-anchor intervals provided a secondary contextual comparison. Post-switch mouse weight was represented by eight bands spanning 35-124 g. The primary multivariable generalized additive regression model accounted for baseline skill, pre- and post-switch practice intensity, and pre- and post-switch mouse sensitivity, and allowed the association between weight band and improvement to vary with baseline skill, post-switch practice, and post-switch sensitivity. For each weight band, predicted mean one-week improvement was standardized to the observed distribution of these covariates among switchers and reported in percentile-rank points. Statistical significance was evaluated using 1,000 permutations in which observed mouse weights were randomly reassigned among switchers without replacement and the model was refitted to generate empirical null distributions for the weight-related test statistics. Predicted improvement differed significantly across the eight weight bands (p = 0.001). Pairwise comparisons identified significant differences between bands (p < 0.05), but no single band was associated with significantly greater predicted improvement than all seven others. In this large naturalistic cohort, predicted improvement was highest for players with 35-44 g mice, followed by 45-54 and 55-64 g, and several pairwise comparisons showed significantly greater improvement in lighter than in heavier weight bands. Across the examined baseline-skill profiles, the lowest predicted improvements occurred in either the 85-99 or 115-124 g band. Predicted improvement differed across weight bands at the 25th-percentile and median baseline-skill values (p = 0.002 and p = 0.003) but not at the 75th percentile (p = 0.153). However, the weight-band x baseline-skill interaction was not significant (p = 0.181), indicating that the analysis did not establish that weight-related differences varied by skill level.

ObjectiveRecovery from post-stroke aphasia is traditionally thought to plateau within a year after stroke. As such, no studies have characterized long-term recovery using comprehensive behavioral assessment and longitudinal functional MRI. We sought to characterize behavioral and neuroplastic changes over nearly six years in a patient with chronic post-stroke aphasia. MethodsA patient with chronic left hemisphere stroke underwent behavioral assessment and task-based fMRI at 9, 22, 33 and 71 months after stroke. Testing assessed auditory comprehension, semantic and phonological processing, naming, reading, spelling, motor speech, and executive function. Task-related activation during an adaptive semantic matching paradigm was quantified within language and semantic regions of interest. ResultsBehavior improved across multiple language domains. WAB-R Aphasia Quotient increased from 49.2 to 69.2, along with the large gains in word finding, connected speech, reading and spelling, whereas auditory comprehension remained relatively stable. fMRI demonstrated progressively increasing activation within left-hemisphere language regions, reaching normative range by the final assessment, along with increasing activation in semantic/executive regions. DiscussionRecovery of language production abilities can continue for years after stroke, supported by neuroplastic changes in the brain. Neurologists should inform stroke survivors that aphasia recovery can continue indefinitely after stroke.

Objectives: Transcranial magnetic stimulation (TMS) is widely used to probe corticospinal excitability by eliciting motor evoked potential (MEP)s in targeted muscles, with MEP characteristics such as magnitude and latency reflecting the physiological state of the pathways being stimulated. Although numerous studies have examined MEP reliability in upper extremity muscles, less is known about the reliability of this measurement across the lower extremity. We hypothesized that inter-session, test-retest reliability of MEPs recorded simultaneously from multiple lower-limb muscles, from a single TMS location, would differ by muscle, stimulation intensity, and quantification method. Materials and Methods: Ten healthy participants (5 males, 5 females) completed three TMS sessions separated by atleast one week. At each session, the stimulation hotspot was identified using a five-location virtual grid anchored at the vertex, with electromyography (EMG) recorded from all eight muscles of interest at each grid location; the grid location producing the largest and most consistent MEPs in the tibialis anterior (TA), the primary target muscle, was selected as the stimulation site and held constant across all three sessions. MEPs were then recorded bilaterally from the TA, soleus, rectus femoris, and biceps femoris muscles at two stimulation intensities (110% and 120% resting motor threshold (RMT)). MEP size was quantified using mean rectified magnitude and peak-to-peak amplitude, and inter-session reliability was assessed using intraclass correlation coefficients (ICC). Bland-Altman analysis was used to characterize the range of measurement variability across all eight muscles. Results: MEP size differed across sessions, and reliability varied by muscle, intensity, and quantification method. The highest reliability was observed in the right TA, the muscle used to establish the stimulation hotspot, using mean rectified magnitude at 120% RMT. Reliability was comparatively lower in the seven non-target muscles recorded from the same fixed stimulation site, indicating that MEP consistency was not uniform across the lower-limb musculature. Conclusions: MEP reliability in the lower extremity depends heavily on the muscle, stimulation intensity, and quantification method used, and is highest in the muscle for which the stimulation site was optimized. These findings support the interpretation that coil positioning targeted to a specific muscle yields more consistent responses in that muscle than in others recorded from the same fixed site, and underscore the importance of careful muscle selection and hotspot optimization when designing TMS protocols for longitudinal or clinical lower-limb research.

Spinal muscular atrophy (SMA) is caused by a deficiency in the survival motor neuron (SMN) protein, resulting in degeneration of spinal motor neurons (MNs). However, persistent neurological deficits despite postnatal SMN-restoring therapies suggest that recovery of sensorimotor and supraspinal circuits may be incomplete. The cerebellum has recently emerged as a supraspinal contributor to motor deficits in the severe SMN{Delta}7 mouse model, yet it remains unclear whether cerebellar pathology is a conserved and therapeutically reversible feature across severe SMA mouse models and clinical subtypes. Here, we identify cerebellar pathology in Taiwanese SMA mice, characterized by hypoplasia, disrupted organization and loss of Purkinje cells (PCs), altered synaptic circuitry, and impaired cerebellar cortical output. Unlike the previously described p53-dependent PC degeneration in SMN{Delta}7 mice, cerebellar pathology in Taiwanese SMA mice was associated with developmental disorganization and external granule layer (EGL)-restricted p53 activation. Human cerebellar tissue mirrored this distinction, with p53 activation found in PCs from SMA Type I and in the EGL from SMA Type 0 individuals, indicating that cerebellar pathology arises through distinct mechanisms across severe forms of SMA. Importantly, two SMN-restoring strategies produced divergent therapeutic outcomes. In SMN{Delta}7 mice, AAV9-SMN prevented PC degeneration yet incompletely restored cerebellar circuitry. AAV9-SMN-treated Taiwanese mice developed severe ataxia-like deficits, retained profound cerebellar pathology, and survived to approximately one month of age. In contrast, systemic risdiplam rescued cerebellar pathology, motor behavior, and survival in both models. Together, these findings identify cerebellar pathology as a conserved yet distinct feature across severe forms of SMA and reveal cell type-specific tropism as a critical determinant of therapeutic outcome. More broadly, these findings suggest that successful recovery requires restoration of distributed supraspinal circuit integrity in addition to rescue of spinal motor pathways.

Childhood cancer survivors (CS) treated with chemotherapy frequently experience long-term cognitive impairments, commonly referred to as CRCI. Whether these deficits reflect disrupted white matter microstructure, altered relationships between microstructure and cognition, or both remains unclear. Here, we applied the NODDI-Bingham model, which quantifies neurite density (NDI), isotropic free water (ISO), and orientation dispersion along primary (ODIp), secondary (ODIs), and total (ODIt) fiber axes, to characterize biophysically specific white matter microstructure in CS and examine its relationship to cognition. Twenty-one pediatric cancer survivors and 21 age-matched healthy controls (HC) underwent multi-shell diffusion MRI. Voxel-wise NODDI-Bingham analyses were performed within JHU atlas regions. Group differences were tested by ANCOVA, and associations between microstructure and cognition were examined with the NIH Toolbox Crystallized, Fluid, and Early Childhood composites using group-specific regressions. Confirmatory analyses were performed in an age-matched subsample of the HCP (n = 679). Notably, CS showed reduced NDI in the corona radiata, cerebral peduncles, and corpus callosum, with elevated ODIt and ODIp in the middle cerebellar peduncle, pathways that subserve processing speed and interhemispheric integration, cognitive domains among the most vulnerable in CRCI. Group-specific regressions revealed qualitatively different relationships between microstructure and cognition: HC exhibited mixed positive and negative relationships across four of five metrics (138 clusters spanning approximately 305,000 voxels; peak Cohen's d up to 3.00), whereas CS showed a predominantly uniformly negative pattern (67 clusters across 57,000 voxels), with no positive clusters for ISO, ODIt, ODIp, or ODIs, thus highlighting that reduced dispersion and extracellular free water are linked to better cognitive performance in CS. HCP analyses reproduced the HC pattern across all five metrics at proportionally smaller effect sizes, ruling out sample-size effects. NODDI-Bingham identifies two aspects of chemotherapy-related white matter pathology that standard diffusion metrics cannot resolve. First, pediatric cancer survivors show selective elevation of ODIp and ODIt in the cerebellar peduncles and reduced NDI in the corona radiata and corpus callosum, localizing group-level injury to specific fanning and neurite density signatures. Second, whereas in healthy controls white matter shows mixed positive and negative relationships between microstructure and cognition, survivors retain only negative relationships for ODIp and ODIt and a diminished mixed pattern for NDI, such that in the chemotherapy-exposed brain, only reduced neurite density and increased primary-axis fanning relate to cognitive impairment. These findings implicate a biophysically specific restructuring of the relationships between white matter and cognition as a candidate mechanism for CRCI and support NODDI-Bingham as a targeted biomarker panel for monitoring and intervention trials.

Generalization is a key cognitive process that allows humans to flexibly apply prior knowledge to guide new behaviors. Difficulties with generalization and flexibility are observed across neurodevelopmental disorders, especially autism, limiting adaptive function and quality of life. Cognitive-behavioral treatment benefits some but not all autistic individuals. As treatment requires application of learned skills to everyday life, variability in generalization ability may limit intervention success in autism. While cognitive substrates of learning and generalization are well established, their potential for explaining clinical outcomes is not known. Here, we combined a category learning task with computational modelling to distinguish two learning strategies underlying generalization -- prototype abstraction vs. exemplar memorization -- and tested whether individual differences in these learning strategies predicted real-world intervention outcomes in autistic youth. Fifty-four participants completed the category learning task at two pre-intervention timepoints, and then completed Unstuck and On Target:14-22 intervention targeting flexible problem solving, goal setting, and planning. We found that participants who consistently relied on prototype abstraction (N=26) were subsequently more likely to benefit from the intervention, showing improvement in parent- and self-reported flexibility. These findings identify prototype abstraction as a clinically relevant cognitive capacity that may help explain individual differences in intervention response and support the tailoring of interventions. More broadly, they demonstrate the value of linking basic cognitive mechanisms to clinical outcomes and may inform strategies to enhance the effectiveness of cognitive-behavioral interventions for youth with developmental disabilities.

AIM: To evaluate whether selective motor control quantified from spontaneous infant movement recordings provides diagnostic and prognostic information for cerebral palsy (CP) beyond established movement-based assessments. METHOD: This multicenter diagnostic and prognostic accuracy study included 302 infants (151 with CP) with spontaneous movement recordings obtained between 10 and 20 weeks corrected age from cohorts in Australia and the United States. All eligible infants with CP were included, and a comparison sample without CP was randomly selected. Recordings were scored using the Baby Observational Selective Control Appraisal (BabyOSCAR), Motor Optimality Score Revised (MOS-R), and General Movements Assessment (GMA). Outcomes at 2 years or older included CP diagnosis, Gross Motor Function Classification System (GMFCS) level, and motor distribution. RESULTS: BabyOSCAR discriminated CP diagnosis (area under the curve [AUC] 0.98), including children later classified in GMFCS level I. Among infants with CP, BabyOSCAR discriminated GMFCS levels I - II from III - V (AUC 0.89). BabyOSCAR absolute asymmetry also discriminated unilateral CP from all other infants (AUC 0.90). Diagnostic discrimination was also observed for MOS-R (AUC 0.94) and GMA (AUC 0.86). INTERPRETATION: Quantifying selective motor control from brief infant movement recordings may provide complementary early information about CP diagnosis, functional level, and motor distribution.

Pathogenic variants in MAPK8IP3 (JIP3) cause Neurodevelopmental Disorder with or without variable Brain Abnormalities (NEDBA), characterized by cognitive impairment, global developmental delay, motor dysfunction, abnormal muscle tone, behavioral dysregulation including autism and attention deficit hyperactivity disorder (ADHD), seizures, and structural brain abnormalities. While more than 30 largely de novo MAPK8IP3 variants have been reported, the functional impact of variants across JIP3 protein structural domains is poorly defined. To address this knowledge gap, we compare clinical features of individuals with a truncating (p.E27X) or one of two missense (p.R578C and p.R1146C) variants from distinct JIP3 functional protein domains to corresponding knock-in mouse models. Our findings showed that all individuals, regardless of variant type, exhibited delays in language and gross motor function, but individual variants were associated with distinct motor, cognitive, and psychiatric symptoms. Corresponding homozygous p.E27X and p.R1147C variant mice resulted in embryonic lethality, consistent with essential roles for JIP3 in early neurodevelopment. Behavioral characterization of viable heterozygous mice revealed variant-specific locomotor, motor coordination, and hindlimb clasping defects that closely recapitulate clinical observations. Heterozygous p.R579C mice exhibited reduced locomotion, impaired motor performance, and hypertonia-like clasping, mirroring human motor deficits. In contrast, p.R1147C mice displayed hyperactivity, hindlimb clasping, and decreased brain weight, paralleling human clinical features. Together, our findings demonstrate that while distinct MAPK8IP3 variants lead to some shared phenotypes, they are also associated with distinct phenotypes that could reveal domain-specific aspects of JIP3 function. This work establishes the first domain-resolved in vivo rodent models of NEDBA and provides a validated translational platform for mechanistic investigation and preclinical therapeutic testing.

BackgroundVisual training can improve residual vision in hemianopia, but there is significant variability in patient outcomes which may reflect differences in neural structures preserved after injury. Diffusion MRI tractography offers a means of assessing white-matter microstructure in vivo, however substantial overlap between neighbouring visual pathways complicates attribution of differences to specific tracts. We quantified tract overlap to identify relatively unique pathway segments to assess training-related microstructural change. MethodsDiffusion MRI data was acquired in six participants with homonymous hemianopia before and after 3-6 months of visual training. Tractography was used to reconstruct three pathways implicated in residual vision: lateral geniculate nucleus (LGN)-V1, LGN-V5 and pulvinar-V5, together with secondary superior colliculus-LGN and superior colliculus-pulvinar pathways. Streamline overlap was quantified along neighbouring tracts, and comparison of pre- to post-training fractional anisotropy was restricted to unique or pair-specific non-overlapping segments. Exploratory relationships with visual outcomes were also examined. ResultsFractional anisotropy increased after training in both early and late pair-specific segments of the LGN-V5 pathway in the lesioned hemisphere. In the late segment, this increase was significantly greater than in the corresponding unique LGN-V1 segment, whereas change in the early LGN-V5 segment did not differ significantly from the unique pulvinar-V5 segment. No significant training-related changes were observed in collicular pathways. Brain-behaviour analyses also preferentially implicated LGN-V5: baseline fractional anisotropy was strongly associated with post-training Gabor detection, and training-related fractional anisotropy change showed a positive association with improvement in Gabor detection, although the latter did not survive multiple comparison correction. ConclusionThese findings support a role for the LGN-V5 pathway in visual plasticity after hemianopia and demonstrate the importance of explicitly quantifying tract overlap when attributing microstructural change to small, neighbouring white-matter pathways.

Background: Detecting environmental regularities is a sophisticated cognitive skill, but its neural basis remains unclear. We tested whether corticospinal excitability tracks stimulus predictability, prediction errors, and task progression while the participants played the Goalkeeper Game. Methods: Sixteen right-handed males (24.4 +/- 6.8 years) saved penalty kicks using index, middle, or ring fingers (left, center, right). Kick sequences were generated by a context tree model, in which contexts represent the minimum recent history required to predict the next event. Participants completed 1,200 trials (6 blocks x 200 trials each). Transcranial magnetic stimulation (TMS) delivered 400 ms before the go signal elicited motor evoked potentials (MEPs) in the first dorsal interosseous (FDI) and flexor digitorum superficialis (FDS) muscles during blocks 2, 4, and 6. Contexts were classified as unpredictable (1, 10) or predictable (2, 20, 00); prediction errors were defined for non-deterministic transitions after context 1. Log-MEPs were analyzed using mixed-effects models. Results: In FDI, a Predictability x Previous-Error x Block interaction emerged (F(2,8997)=6.89, p=.001), confined to the final block. Predictability increased MEP amplitudes after successful transitions (+6.3%; p=0.006) but decreased MEP amplitudes after failed transitions (-7.0%; p=0.007). For FDS, unpredictable trials elicited larger MEPs (+7.2%; p=0.002), and MEPs increased from block 2 to 6 (+16.8%; p=0.003). Conclusions: FDS MEP responses were broadly associated with uncertainty and task progression, whereas FDI MEP responses showed context-specific, error-dependent modulation after extended exposure, suggesting fine-grained predictive coding in goal-executing effectors.