Universal Transform or Multiple Functionality? Understanding the Contribution of the Human Cerebellum across Task Domains

Beta-band oscillations and spike-local field potential synchronization in the motor cortex are correlated with movement deficits in an exercise-induced fatigue mouse model

Fatigue, a complex and multifaceted symptom, profoundly influences quality of life, particularly among individuals suffering from chronic medical conditions or neurological disorders. This symptom not only exacerbates existing conditions but also hinders daily functioning, thereby perpetuating a vicious cycle of worsening symptoms and reduced physical activity. Given the pivotal role of the motor cortex (M1) in coordinating and executing voluntary movements, understanding how the cortex regulates fatigue is crucial. Despite its importance, the neural mechanisms underlying fatigue remain inadequately explored. In this study, we employed electrophysiological recordings in the M1 region of mice to investigate how excitation-inhibition dynamics and neural oscillations are regulated during exercise-induced fatigue. We observed that fatigue led to decreased voluntary physical activity and cognitive performance, manifesting as reduced running wheel distance, mean speed, exercise intensity, and exploratory behaviour. At the neural level, we detected increased firing frequencies for M1 neurons, including both pyramidal neurons and interneurons, along with heightened beta-band oscillatory activity and stronger coupling between beta-band oscillations and interneurons. These findings enhance our understanding of the mechanisms underlying fatigue, offering insights into behavioural, excitability, and oscillatory changes. The results of this study could pave the way for the development of novel intervention strategies to combat fatigue.

Cerebellar contribution to multisensory integration: A computational modeling exploration

The remarkable ability of the human brain to create a coherent perception of reality relies heavily on multisensory integration-the complex process of combining inputs from different senses. While this mechanism is fundamental to our understanding of the world, its underlying neural architecture remains partially unknown. This study investigates the role of the cerebellum in multisensory integration through a novel computational approach inspired by clinical observations of a patient with cerebellar agenesis. With reference to the clinical data comparing an acerebellar patient with age-matched control subjects, we exploited biologically realistic spiking neural networks to model both conditions. Our computational framework enables testing multiple network configurations and parameters, effectively replicating and extending the clinical experiments in silico. To enhance accessibility and promote broader adoption among researchers, we complemented this framework with a user-friendly web-based interface, eliminating the need for programming expertise. The computational results closely mirror the clinical findings, providing support for the critical contribution of the cerebellum in multisensory integration. Beyond being a consistent proof of concept for the previous clinical observations, this study introduces a versatile platform for testing brain models through our newly developed framework and interface. Thus, this work not only advances our understanding of the cerebellar role in sensory processing but also establishes a robust methodology for future computational investigations of neural mechanisms.

A different finding on the role of cerebro-cerebellar RSFC in reading skills among Chinese children with developmental dyslexia

BACKGROUND

It's still unclear on the effect of the cerebellum on developmental dyslexia (DD). To narrow the gap, we compared the cerebro-cerebellar resting-state functional connectivity (RSFC) between children with and without DD, and analyzed the relationship of cerebro-cerebellar RSFC with reading skills.

METHODS

43 children with DD (32 males, mean age = 9.21 years) and 82 typical development (TD) children (47 males, mean age = 8.96 years) were recruited from China. All participants completed rs-fMRI scan and reading tasks including phonological awareness, rapid automatized naming, and orthography awareness. Cerebro-cerebellar RSFC were compared between children with and without DD. And the correlations between cerebro-cerebellar RSFC and reading skills were analyzed in all subjects.

RESULTS

Compared to the TD group, Chinese children with DD showed significantly increased RSFC between cerebellar vermis IX and right superior frontal gyrus, and between cerebellar vermis IX and left middle frontal gyrus. The RSFC between vermis IX and right superior frontal gyrus was correlated with response time of rapid automatized naming (r = 0.198, p = 0.028) and phonological awareness score (r = -0.288, p = 0.002). And the RSFC between vermis IX and left middle frontal gyrus was also correlated with response time of rapid automatized naming (r = 0.223, p = 0.013) and phonological awareness score (r = -0.182, p = 0.048).

CONCLUSION

Chinese children with DD showed increased RSFC between the vermal cerebellum and bilateral frontal gyrus. It may potentially compensate for their phonological awareness and rapid automatized naming deficits.

Characteristics of positive and negative networks in working memory task of basketball athletes

Working memory (WM) plays a vital role in athletic performance in open-skill sports like basketball. However, sport-induced WM adaptation is complex, and the underlying neural mechanisms remain poorly characterized. Using an N-back task with fMRI, this study investigated the brain function of 55 basketball athletes and 55 gender- and age-matched healthy controls during the WM tasks. The results revealed that basketball athletes showed increased activation in the task-positive network (TPN), reduced inhibitory activation in the default mode network (DMN), and cerebellar-mediated new dynamic between the two networks. These neural adaptations aligned with accelerated response speed at the cost of reduced 2-back accuracy, reflecting a speed-accuracy trade-off optimized for sport-specific demands. Future research should explore interventions targeting DMN regulation alongside TPN engagement to optimize cognitive performance in athletes. By bridging sports neuroscience and cognitive training paradigms, this study offers new insights into how sports training sculpts the brain's functional architecture.

Motor markers of congenital cerebellar hypoplasia

The Reach-to-Grasp (RtG) movement is a fundamental feature of human competence and a widely adopted model for the study of functional movements in both healthy and disease-affected individuals. In particular, 3-D kinematic analysis of RtG allows the study of fine hand movements and submovements, described as secondary fluctuations of the main movement. The aim of this study was to use a RtG movement to test upper limb motor performance in a patient with ataxic syndrome due to cerebellar hypoplasia. 3-D kinematical recording and MRI-based structural measures were combined to provide a comprehensive characterization of the movement and its neural underpinnings at the baseline and after a 2 years follow-up. In terms of kinematics, a dissociation between reaching and grasping performance was observed over time: while grasping appeared to be characterized by an improvement at the 2 years follow-up, reaching showed a significant increase of jerk submovements, suggesting a loss of functionality in feedback mechanisms allowing for smoothness of the movement. At the neural level, an increase of gray matter volume of the anterior right cerebellar hemisphere, alongside with an increased structural connectivity within the sensorimotor network were observed at the 2 years follow up, presumably mirroring the improvement observed for the grasping component. These results highlight the potential of the jerk submovements as a motor biomarker in contexts where feedback mechanisms may be compromised, such as in the case of cerebellar dysfunctions, contributing to the development of new methods for the motor assessment of patients in clinical settings.

How do big brains evolve?

In both birds and mammals, variation in brain size predominantly reflects variation in mass or volume of the pallium (neocortex) and, to a lesser extent, of the cerebellum, suggesting convergent coevolution of brains and cognition. When brain measures are based on neuron counts, however, a surprisingly different picture emerges: The number of neurons in the cerebellum surpasses those in the pallium of all mammals (including humans and other primates) and in many but not all birds studied to date. In particular, parrots and corvids, clades known for cognitive abilities that match those of primates, have brains that contain more pallial than cerebellar neurons. Birds and mammals may thus have followed different evolutionary routes of pallial-cerebellar coordination behind enhanced cognitive complexity.

Volumetric Changes in Cerebellar Transverse Zones: Age and Sex Effects in Health and Neurological Disorders

Cerebellar volumetric changes are intricately linked to aging, with distinct patterns across its transverse zones, the functional subdivisions characterized by unique cytoarchitectural and connectivity profiles. Despite research efforts, the cerebellar aging process in health and neurological disorders remains poorly understood. In this study, we investigated the effects of age and sex on total cerebellum, transverse zone, and lobule volumes using MRI data from over 45,000 participants compiled from six neuroimaging datasets. We also propose a framework for estimating cerebellum age as an indicator of cerebellar health. Significant age-dependent volume reductions were observed across transverse zones, with the central zone (CZ; lobules VI and VII) exhibiting the steepest decline in both health and neurological disorders. This finding highlights the CZ's vulnerability to aging and its critical role in cognitive and emotional processing. We also found prominent sex differences in age-dependent volumetric changes. Males exhibited smaller total intracranial volume (TIV)-adjusted cerebellum volume and faster age-dependent volume reduction than females in both health and mild cognitive impairment (MCI), Alzheimer disease (AD), and Parkinson disease (PD). In contrast, females with schizophrenia (SZ) and cocaine use disorder (CUD) revealed faster age-dependent cerebellar volume reduction than males. Patients with MCI, AD, and PD experienced more pronounced atrophy in the posterior (PZ) and nodular (NZ) zones compared to age-matched healthy controls, while SZ patients were characterized by a more prominent reduction in CZ. In CUD, a non-significant volume decline was observed in all zones compared to the controls. Moreover, our framework for estimating cerebellum age revealed a notable difference in cerebellar aging between healthy individuals and neurological patients. Finally, we charted age-dependent changes in cerebellar volume in healthy individuals, focusing on transverse zones capturing the functional subdivisions. These findings underscore the potential of cerebellar volumetric analysis as a biomarker for early detection and monitoring of neurodegenerative and neuropsychiatric disorders. Our novel approach complements and enhances MRI-based analyses, providing essential insights into the pathogenesis of aging, neurodegeneration, and chronic neuropsychiatric conditions.

Ignoring the cerebellum is hindering progress in neuroscience

Traditionally considered a motor structure, the cerebellum has been shown to play a key role in several cognitive functions. However, for decades, the cerebellum has been largely overlooked and even deliberately excluded from 'whole-brain' neuroimaging studies. Here, we propose that the continued exclusion of the cerebellum has limited our understanding of whole-brain function. We describe reasons - both warranted and unwarranted - behind its historical exclusion from the neuroimaging literature, review literature describing the importance of the cerebellum and its unique role in brain function, and outline the potential unintended negative consequences of exclusion of the cerebellum for our comprehensive understanding of brain function and clinical disorders.

The Growing Little Brain: Cerebellar Functional Development from Cradle to School

Despite the cerebellum's crucial role in brain functions, its early development, particularly in relation to the cerebrum, remains poorly understood. Here, we examine cerebellocortical connectivity using over 1,000 high-quality resting-state functional MRI scans of children from birth to 60 months. By mapping cerebellar topography with fine temporal detail for the first time, we show the hierarchical organization of cerebellocortical functional connectivity from infancy. We observe dynamic shifts in cerebellar network gradients, which become more focal with age while generally maintaining stable anchor points similar to adults, highlighting the cerebellum's evolving yet stable role in functional integration during early development. Our findings provide the first evidence of cerebellar connections to higher-order networks at birth, which generally strengthen with age, emphasizing the cerebellum's early role in cognitive processing beyond sensory and motor functions. Our study provides insights into early cerebellocortical interactions, reveals functional asymmetry and sex-specific patterns in cerebellar development, and lays the groundwork for future research on cerebellum-related disorders in children.

Contractions in human cerebellar-cortical manifold structure underlie motor reinforcement learning

How the brain learns new motor commands through reinforcement involves distributed neural circuits beyond known frontal-striatal pathways, yet a comprehensive understanding of this broader neural architecture remains elusive. Here, using human functional MRI (N = 46, 27 females) and manifold learning techniques, we identified a low-dimensional neural space that captured the dynamic changes in whole-brain functional organization during a reward-based trajectory learning task. By quantifying participants' learning rates through an Actor-Critic model, we discovered that periods of accelerated learning were characterized by significant manifold contractions across multiple brain regions, including areas of limbic and hippocampal cortex, as well as the cerebellum. This contraction reflected enhanced network integration, with notably stronger connectivity between several of these regions and the sensorimotor cerebellum correlating with higher learning rates. These findings challenge the traditional view of the cerebellum as solely involved in error-based learning, supporting the emerging view that it coordinates with other brain regions during reinforcement learning.Significance Statement This study reveals how distributed brain systems, including the cerebellum and hippocampus, alter their functional connectivity to support motor learning through reinforcement. Using advanced manifold learning techniques on functional MRI data, we examined changes in regional connectivity during reward-based learning and their relationship to learning rate. For several brain regions, we found that periods of heightened learning were associated with increased cerebellar connectivity, suggesting a key role for the cerebellum in reward-based motor learning. These findings challenge the traditional view of the cerebellum as solely involved in supervised (error-based) learning and add to a growing rodent literature supporting a role for cerebellar circuits in reward-driven learning.

Amygdala Function, Blood Flow, and Functional Connectivity in Nonclinical Schizotypy

BACKGROUND AND HYPOTHESIS

Schizotypy can be utilized as a phenotypic risk marker for schizophrenia and its spectrum and might relate to putative dimensional biological markers of the psychosis spectrum. Among these are amygdala function and structure, which are impaired in schizophrenia, but possibly also correlated with subclinical expression of schizotypy in nonclinical samples. We tested whether different parameters relating to amygdala function would be different in healthy subjects with relatively higher vs lower schizotypy traits.

STUDY DESIGN

Sixty-three psychiatrically healthy subjects (42 with higher vs 21 with lower schizotypy scores, selected on the basis of the Oxford-Liverpool Inventory of Feelings and Experiences positive schizotypy subscale) underwent a multimodal imaging protocol, including functional magnetic resonance imaging (fMRI) during a task-based emotional (fearful) face recognition paradigm, arterial spin labeling for measurement of regional cerebral blood flow (rCBF) at rest, and resting-state fMRI for functional connectivity (FC) analyses, as well as a T1-weighted structural MRI scan.

STUDY RESULTS

The high schizotypy group showed significantly higher right amygdala activation during viewing of fearful emotional images and lower resting-state FC of the left amygdala with a cerebellum cluster, but no differences in resting-state amygdala rCBF or volume.

CONCLUSIONS

Our findings demonstrate a functionally relevant effect of schizotypy on amygdala activation in the absence of baseline rCBF or macroscopic structure. This suggests that while schizotypy might affect some functional or structural parameters in the brain, certain functionally relevant effects only emerge during cognitive or emotional triggers.

Resting-State Functional Connectivity of the Cerebellum in Patients With Chronic Low Back Pain

OBJECTIVE

Chronic low back pain affects nociceptive responses in the cerebellum, which leads to increased pain perception and sensorimotor control dysfunction. This study aimed to investigate altered functional connectivity in the anterior and posterior lobes of the cerebellum during chronic low back pain.

DESIGN

Twenty patients with chronic low back pain and 18 healthy participants underwent 3.0 T resting-state functional magnetic resonance imaging. The bilateral lobule V of the anterior cerebellum and Crus I of the posterior cerebellum were selected as the region of interest for identifying the corresponding networks.

RESULTS

The left lobule V had a greater intrinsic connectivity with the left insular cortex, left orbitofrontal cortex, and bilateral medial prefrontal cortex in patients with chronic low back pain. In contrast, the right lobule V and bilateral Crus I had a significantly decreased connectivity with the contralateral multimodal cerebral networks, including the default mode network, salience network, and emotional network.

CONCLUSIONS

The cerebellum had mechanistic implications in pain-related changes, which are involved in motor control, cognition, and emotion processing. These findings provide a novel perspective on the role of functional subregions in chronic low back pain, which add to the growing body of evidence that the cerebellum can be a potential target for noninvasive brain stimulation for chronic pain treatment.

Neural circuit mechanisms to transform cerebellar population dynamics for motor control in monkeys

We exploit identification of neuron types during extracellular recording to demonstrate how the cerebellar cortex's well-established architecture transforms inputs into outputs. During smooth pursuit eye movements, the floccular complex performs distinct input-output transformations of temporal dynamics and directional response properties. The responses of different interneuron types localize the circuit mechanisms of each transformation. Mossy fibers and unipolar brush cells emphasize eye position dynamics uniformly across the cardinal axes; Purkinje cells and molecular layer interneurons code eye velocity along directionally biased axes; Golgi cells show unmodulated firing. Differential directional response properties of different neuron types localize the directional input-output transformation to the last-order inputs to Purkinje cells. Differential temporal dynamics pinpoint the site of the temporal input-output transformation to granule cells. Specific granule cell population dynamics allow the temporal transformations required in the area we study and generalize to many temporal transformations, providing a complete framework to understand cerebellar circuit computation.

Impact statement

We dissect the circuit computations performed by the floccular complex of the cerebellum during an exemplar sensory-motor behavior, taking advantage of knowledge of the circuit architecture, existence of discrete neuron types, and a newfound ability to identify neuron types from extracellular recordings. Our results describe the contributions of the major neuron types to the cerebellar input-output computations, identify the population dynamics needed in granule cells to support those computations, and to create a basis set to enable temporally-specific motor behavior and motor learning.

Identifying major depressive disorder based on cerebral blood flow and brain structure: An explainable multimodal learning study

Magnetic resonance imaging (MRI) offers non-invasive assessments of brain structure and function for analyzing brain disorders. With the increasing accumulation of multimodal MRI data in recent years, integrating information from various modalities has become an effective strategy for improving the detection of brain disorders. This study focuses on identifying major depressive disorder (MDD) by using arterial spin labeling (ASL) perfusion MRI in conjunction with structural MRI data. We collected ASL and structural MRI data from 260 participants, including 169 MDD patients and 91 healthy controls. We developed an explainable fusion method to identify MDD, utilizing cerebral blood flow (CBF) data from ASL perfusion MRI and brain tissue volumes from structural MRI. The fusion model, which integrates multimodal data, demonstrated superior predictive performance for MDD. By combining MRI regional volumes with CBF data, we achieved more effective results than using each modality independently. Additionally, we analyzed feature importance and interactions to explain the fusion model. We identified fourteen important features, comprising eight regional volumes and six regional CBF measures, that played a crucial role in the identification of MDD. Furthermore, we found three feature interactions among the important features and seven interactions between structural and functional features, which were particularly prominent in the model. The results of this study suggest that the fusion learning approach, which integrates ASL and structural MRI data, is effective in detecting MDD. Moreover, the study demonstrates that the model explanation method can reveal key features that influence the decisions of models, as well as potential interactions among these key features or between functional and structural features in identifying MDD.

Cerebellar activity and functional connectivity in subacute subcortical aphasia: Association with language recovery

Loss of language function (aphasia) is a common complication after stroke, and post-stroke recovery remains highly unpredictable due to the absence of reliable neurobiomarkers. Growing evidence points to involvement of the cerebellum in language processing; however, it is unclear if abnormal cerebellar activity and altered functional connectivity (FC) to language-related regions of cerebral cortex are underlying neural mechanisms for subcortical aphasia. In this longitudinal observational study, we used resting-state functional magnetic resonance imaging to examine potential abnormalities in spontaneous cerebellar activity and resting-state (rs)FC with language networks among post-stroke patients with subacute subcortical aphasia (n = 19) compared to healthy controls (HCs, n = 18). In addition, correlations between rsFC variables and language performance metrics were examined at post-stroke baseline and at follow-up. Compared to HCs, patients with subacute subcortical aphasia exhibited significantly reduced fractional amplitude of low frequency fluctuations, a measure of spontaneous activity, in the right cerebellar Crus II (rCrus II) region and reduced rsFC between rCrus II and left inferior frontal gyrus (LIFG), left angular gyrus (LAG), and left middle temporal gyrus (LMTG). Both rCrus II-LAG and rCrus II-LMTG rsFC values were positively correlated with Aphasia Battery of Chinese scores at baseline. Baseline rCrus II-LIFG rsFC was also positively correlated with spontaneous speech and naming scores at follow-up. A stronger baseline rCrus II-LIFG rsFC predicted superior recovery of language function post-stroke. We conclude that the right cerebellum may be an effective therapeutic target for subcortical aphasia.

Time Dependent Effects of Cerebellar tDCS on Cerebello-cortical Connectivity Networks in Young Adults

The cerebellum is involved in non-motor processing, supported by topographically distinct cerebellar activations and closed-loop circuits between the cerebellum and the cortex. Disruptions to cerebellar function may negatively impact prefrontal function and processing. Cerebellar resources may be important for offloading cortical processing, providing crucial scaffolding for normative performance and function. Here, we used transcranial direct current stimulation (tDCS) to temporarily alter cerebellar function and subsequently investigated resting state network connectivity. Critically, what happens to these circuits if the cerebellum is not functioning optimally, or after stimulation, remains relatively unknown. We employed a between-subjects design with 74 participants total (38 female; M = 22.0 years, SD = 3.45), applying anodal (n = 25), cathodal (n = 25), or sham (n = 24) stimulation to the cerebellum to examine the effect of stimulation on cerebello-cortical resting state connectivity in young adults. We predicted increased functional connectivity following cathodal stimulation and decreased functional connectivity following anodal stimulation. We found, anodal stimulation resulted in increased connectivity in both ipsilateral and contralateral regions of the cortex, perhaps indicative of a compensatory response to degraded cerebellar output. Additionally, a window analysis also demonstrated a time dependent nature to the impacts of cerebellar tDCS on connectivity, particularly with cognitive regions of the cerebral cortex. This work suggests that when cerebellar outputs are degraded, in this case by tDCS, the cerebellum offloads its processing responsibility which encourages more cortical regions to engage to compensate for the degraded cerebellar output. This results in in differences in cortical activation patterns and performance deficits. These results might inform and update existing compensatory models, which focus primarily on the cortex, to include the cerebellum as a vital structure involved in the scaffolding of cortical processing.

Global functional connectivity reorganization reflects cognitive processing speed deficits and fatigue in multiple sclerosis

BACKGROUND AND PURPOSE

Cognitive impairment (CI) in multiple sclerosis (MS) is associated with bidirectional changes in resting-state centrality measures. However, practicable functional magnetic resonance imaging (fMRI) biomarkers of CI are still lacking. The aim of this study was to assess the graph-theory-based degree rank order disruption index (kD) and its association with cognitive processing speed as a marker of CI in patients with MS (PwMS) in a secondary cross-sectional fMRI analysis.

METHODS

Differentiation between PwMS and healthy controls (HCs) using kD and its correlation with CI (Symbol Digit Modalities Test) was compared to established imaging biomarkers (regional degree, volumetry, diffusion-weighted imaging, lesion mapping). Additional associations were assessed for fatigue (Fatigue Scale for Motor and Cognitive Functions), gait and global disability.

RESULTS

Analysis in 56 PwMS and 58 HCs (35/27 women, median age 45.1/40.5 years) showed lower kD in PwMS than in HCs (median -0.30/-0.06, interquartile range 0.55/0.54; p = 0.009, Mann-Whitney U test), yielding acceptable yet non-superior differentiation (area under curve 0.64). kD and degree in medial prefrontal cortex (MPFC) correlated with CI (kD/MPFC Spearman's ρ = 0.32/-0.45, p = 0.019/0.001, n = 55). kD also explained fatigue (ρ = -0.34, p = 0.010, n = 56) but neither gait nor disability.

CONCLUSIONS

kD is a potential biomarker of CI and fatigue warranting further validation.

Functional Connectivity-Based Searchlight Multivariate Pattern Analysis for Discriminating Schizophrenia Patients and Predicting Clinical Variables

BACKGROUND

Schizophrenia, a multifaceted psychiatric disorder characterized by functional dysconnectivity, poses significant challenges in clinical practice. This study explores the potential of functional connectivity (FC)-based searchlight multivariate pattern analysis (CBS-MVPA) to discriminate between schizophrenia patients and healthy controls while also predicting clinical variables.

STUDY DESIGN

We enrolled 112 schizophrenia patients and 119 demographically matched healthy controls. Resting-state functional magnetic resonance imaging data were collected, and whole-brain FC subnetworks were constructed. Additionally, clinical assessments and cognitive evaluations yielded a dataset comprising 36 clinical variables. Finally, CBS-MVPA was utilized to identify subnetworks capable of effectively distinguishing between the patient and control groups and predicting clinical scores.

STUDY RESULTS

The CBS-MVPA approach identified 63 brain subnetworks exhibiting significantly high classification accuracies, ranging from 62.2% to 75.6%, in distinguishing individuals with schizophrenia from healthy controls. Among them, 5 specific subnetworks centered on the dorsolateral superior frontal gyrus, orbital part of inferior frontal gyrus, superior occipital gyrus, hippocampus, and parahippocampal gyrus showed predictive capabilities for clinical variables within the schizophrenia cohort.

CONCLUSION

This study highlights the potential of CBS-MVPA as a valuable tool for localizing the information related to schizophrenia in terms of brain network abnormalities and capturing the relationship between these abnormalities and clinical variables, and thus, deepens our understanding of the neurological mechanisms of schizophrenia.

The Cerebellum and the Motor Cortex: Multiple Networks Controlling Multiple Aspects of Behavior

The cerebellum and its thalamic projections to the primary motor cortex (M1) are well known to play an essential role in executing daily actions. Anatomic investigations in animals and postmortem humans have established the reciprocal connections between these regions; however, how these pathways can shape cortical activity in behavioral contexts and help promote recovery in neuropathological conditions remains not well understood. The present review aims to provide a comprehensive description of these pathways in animals and humans and discuss how novel noninvasive brain stimulation (NIBS) methods can be used to gain a deeper understanding of the cerebellar-M1 connections. In the first section, we focus on recent animal literature that details how information sent from the cerebellum and thalamus is integrated into an broad network of cortical motor neurons. We then discuss how NIBS approaches in humans can be used to reliably assess the connectivity between the cerebellum and M1. Moreover, we provide the latest perspectives on using advanced NIBS approaches to investigate and modulate multiple cerebellar-cortical networks involved in movement behavior and plasticity. Finally, we discuss how these emerging methods have been used in translation research to produce long-lasting modifications of cerebellar-thalamic-M1 to restore cortical activity and motor function in neurologic patients.

Bias-accounting meta-analyses overcome cerebellar neglect to refine the cerebellar behavioral topography

The cerebellum plays important roles in motor, cognitive, and emotional behaviors. Previous cerebellar coordinate-based meta-analyses and mappings have attributed different behaviors to cerebellar subareas, but an accurate behavioral topography is lacking. Here, we show overrepresentation of superior activation foci, which may be exacerbated by historical cerebellar neglect. Unequal foci distributions render the null hypothesis of standard activation likelihood estimation unsuitable. Our new method, cerebellum-specific activation-likelihood estimation (C-SALE), finds behavioral convergence beyond baseline activation rates. It does this by testing experimental foci versus null models sampled from a data-driven, biased probability distribution of finding foci at any cerebellar location. Cerebellar mappings were made across five BrainMap task domains and thirty-five subdomains, illustrating improved specificity of the new method. Twelve of forty (sub)domains reached convergence in specific cerebellar subregions, supporting dual motor representations and placing cognition in posterior-lateral regions. Repeated subsampling revealed that whereas action, language and working memory were relatively stable, other behaviors produced unstable meta-analytic maps. Lastly, meta-analytic connectivity modeling in the same debiased framework was used to reveal coactivation networks of cerebellar behavioral clusters. In sum, we created a new method for cerebellar meta-analysis that accounts for data biases and can be flexibly adapted to any part of the brain. Our findings provide a refined understanding of cerebellar involvement in human behaviors, highlighting regions for future investigation in both basic and clinical applications.

Structural deviations of the posterior fossa and the cerebellum and their cognitive links in a neurodevelopmental deletion syndrome

High-impact genetic variants associated with neurodevelopmental disorders provide biologically-defined entry points for mechanistic investigation. The 3q29 deletion (3q29Del) is one such variant, conferring a 40-100-fold increased risk for schizophrenia, as well as high risk for autism and intellectual disability. However, the mechanisms leading to neurodevelopmental disability remain largely unknown. Here, we report the first in vivo quantitative neuroimaging study in individuals with 3q29Del (N = 24) and neurotypical controls (N = 1608) using structural MRI. Given prior radiology reports of posterior fossa abnormalities in 3q29Del, we focused our investigation on the cerebellum and its tissue-types and lobules. Additionally, we compared the prevalence of cystic/cyst-like malformations of the posterior fossa between 3q29Del and controls and examined the association between neuroanatomical findings and quantitative traits to probe gene-brain-behavior relationships. 3q29Del participants had smaller cerebellar cortex volumes than controls, before and after correction for intracranial volume (ICV). An anterior-posterior gradient emerged in finer grained lobule-based and voxel-wise analyses. 3q29Del participants also had larger cerebellar white matter volumes than controls following ICV-correction and displayed elevated rates of posterior fossa arachnoid cysts and mega cisterna magna findings independent of cerebellar volume. Cerebellar white matter and subregional gray matter volumes were associated with visual-perception and visual-motor integration skills as well as IQ, while cystic/cyst-like malformations yielded no behavioral link. In summary, we find that abnormal development of cerebellar structures may represent neuroimaging-based biomarkers of cognitive and sensorimotor function in 3q29Del, adding to the growing evidence identifying cerebellar pathology as an intersection point between syndromic and idiopathic forms of neurodevelopmental disabilities.

Increased understanding of complex neuronal circuits in the cerebellar cortex

The prevailing belief has been that the fundamental structures of cerebellar neuronal circuits, consisting of a few major neuron types, are simple and well understood. Given that the cerebellum has long been known to be crucial for motor behaviors, these simple yet organized circuit structures seemed beneficial for theoretical studies proposing neural mechanisms underlying cerebellar motor functions and learning. On the other hand, experimental studies using advanced techniques have revealed numerous structural properties that were not traditionally defined. These include subdivided neuronal types and their circuit structures, feedback pathways from output Purkinje cells, and the multidimensional organization of neuronal interactions. With the recent recognition of the cerebellar involvement in non-motor functions, it is possible that these newly identified structural properties, which are potentially capable of generating greater complexity than previously recognized, are associated with increased information capacity. This, in turn, could contribute to the wide range of cerebellar functions. However, it remains largely unknown how such structural properties contribute to cerebellar neural computations through the regulation of neuronal activity or synaptic transmissions. To promote further research into cerebellar circuit structures and their functional significance, we aim to summarize the newly identified structural properties of the cerebellar cortex and discuss future research directions concerning cerebellar circuit structures and their potential functions.

Cerebellar involvement in Parkinson's disease: Pathophysiology and neuroimaging

ABSTRACT

Parkinson's disease (PD) is a neurodegenerative disease characterized by various motor and non-motor symptoms. The complexity of its symptoms suggests that PD is a heterogeneous neurological disorder. Its pathological changes are not limited to the substantia nigra-striatal system, but gradually extending to other regions including the cerebellum. The cerebellum is connected to a wide range of central nervous system regions that form essential neural circuits affected by PD. In addition, altered dopaminergic activity and α-synuclein pathology are found in the cerebellum, further suggesting its role in the PD progression. Furthermore, an increasing evidence obtained from imaging studies has demonstrated that cerebellar structure, functional connectivity, and neural metabolism are altered in PD when compared to healthy controls, as well as among different PD subtypes. This review provides a comprehensive summary of the cerebellar pathophysiology and results from neuroimaging studies related to both motor and non-motor symptoms of PD, highlighting the potential significance of cerebellar assessment in PD diagnosis, differential diagnosis, and disease monitoring.

The cerebellum acts as the analog to the medial temporal lobe for sensorimotor memory

The cerebellum is critical for sensorimotor learning. The specific contribution that it makes, however, remains unclear. Inspired by the classic finding that for declarative memories, medial temporal lobe (MTL) structures provide a gateway to the formation of long-term memory but are not required for short-term memory, we hypothesized that for sensorimotor memories, the cerebellum may play an analogous role. Here, we studied the sensorimotor learning of individuals with severe ataxia from cerebellar degeneration. We dissected the memories they formed during sensorimotor learning into a short-term temporally-volatile component, that decays rapidly with a time constant of just 15 to 20 s and thus cannot lead to long-term retention, and a longer-term temporally-persistent component that is stable for 60 s or more and leads to long-term retention. Remarkably, we find that these individuals display dramatically reduced levels of temporally-persistent sensorimotor memory, despite spared and even elevated levels of temporally-volatile sensorimotor memory. In particular, we find both impairment that systematically worsens with memory window duration over shorter memory windows (<12 s) and near-complete impairment of memory maintenance over longer memory windows (>25 s). This dissociation uncovers a unique role for the cerebellum as a gateway for the formation of long-term but not short-term sensorimotor memories, mirroring the role of the MTL for declarative memories. It thus reveals the existence of distinct neural substrates for short-term and long-term sensorimotor memory, and it explains both the trial-to-trial differences identified in this study and long-standing study-to-study differences in the effects of cerebellar damage on sensorimotor learning ability.

Converging and Diverging Cerebellar Pathways for Motor and Social Behaviors in Mice

Evidence from clinical and preclinical studies has shown that the cerebellum contributes to cognitive functions, including social behaviors. Now that the cerebellum's role in a wider range of behaviors has been confirmed, the question arises whether the cerebellum contributes to social behaviors via the same mechanisms with which it modulates movements. This review seeks to answer whether the cerebellum guides motor and social behaviors through identical pathways. It focuses on studies in which cerebellar cells, synapses, or genes are manipulated in a cell-type specific manner followed by testing of the effects on social and motor behaviors. These studies show that both anatomically restricted and cerebellar cortex-wide manipulations can lead to social impairments without abnormal motor control, and vice versa. These studies suggest that the cerebellum employs different cellular, synaptic, and molecular pathways for social and motor behaviors. Future studies warrant a focus on the diverging mechanisms by which the cerebellum contributes to a wide range of neural functions.

Altered cerebellar effective connectivity in first-episode schizophrenia and long-term changes after treatment

AIM

Cerebello-cortical functional dysconnectivity plays a key role in the pathology of schizophrenia (SZ). We aimed to investigate the changes in cerebello-cortical directional connectivity in patients with SZ.

METHODS

A total of 180 drug-naïve patients with first-episode SZ (54 reassessed after 1 year of treatment) and 166 healthy controls (HCs) were included. Resting-state functional magnetic resonance imaging was used to perform Granger causal analysis, in which each of the nine cerebellar functional systems was defined as a seed. The observed effective connectivity (EC) alterations at baseline were further assessed at follow-up and were associated with changes in psychotic symptom.

RESULTS

We observed increased bottom-up EC in first-episode SZ from the cerebellum to the cerebrum (e.g. from the cerebellar attention and cingulo-opercular systems to the bilateral angular gyri, and from the cerebellar cingulo-opercular system to the right inferior frontal gyrus). In contrast, decreased top-down EC in the first-episode SZ was mainly from the cerebrum to the cerebellum (e.g. from the right inferior temporal gyrus, left middle temporal gyrus, left putamen, and right angular gyrus to the cerebellar language system). After 1 year of antipsychotic treatment, information projections from the cerebrum to the cerebellum were partly restored and positively related to symptom remission.

CONCLUSION

These findings suggest that decreased top-down EC during the acute phase of SZ may be a state-dependent alteration related to symptoms and medication. However, increased bottom-up EC may reflect a persistent pathological trait.

Preterm Birth Alters the Regional Development and Structural Covariance of Cerebellum at Term-Equivalent Age

Preterm birth is associated with increased risk for a spectrum of neurodevelopmental disabilities. The cerebellum is implicated in a wide range of cognitive functions extending beyond sensorimotor control and plays an increasingly recognized role in brain development. Morphometric studies based on volume analyses have revealed impaired cerebellar development in preterm infants. However, the structural covariance between the cerebellum and cerebral cortex has not been studied during the neonatal period, and the extent to which structural covariance is affected by preterm birth remains unknown. In this study, using the structural MR images of 52 preterm infants scanned at term-equivalent age and 312 full-term controls from the Developing Human Connectome Project, we compared volumetric growth, local cerebellum shape development and cerebello-cerebral structural covariance between the two groups. We found that although there was no significant difference in the overall volume measurements between preterm and full-term infants, the shape measurements were different. Compared with the control infants, preterm infants had significantly larger thickness in the vermis and lower thickness in the lateral portions of the bilateral cerebral hemispheres. The structural covariance between the cerebellum and frontal and parietal lobes was significantly greater in preterm infants than in full-term controls. The findings in this study suggested that cerebellar development and cerebello-cerebral structural covariance may be affected by premature birth.

No Evidence for Semantic Prediction Deficits in Individuals With Cerebellar Degeneration

Cerebellar involvement in language processing has received considerable attention in the neuroimaging and neuropsychology literatures. Building off the motor control literature, one account of this involvement centers on the idea of internal models. In the context of language, this hypothesis suggests that the cerebellum is essential for building semantic models that, in concert with the cerebral cortex, help anticipate or predict linguistic input. To date, supportive evidence has primarily come from neuroimaging studies showing that cerebellar activation increases in contexts in which semantic predictions are generated and violated. Taking a neuropsychological approach, we put the internal model hypothesis to the test, asking if individuals with cerebellar degeneration (n = 14) show reduced sensitivity to semantic prediction. Using a sentence verification task, we compare reaction time to sentences that vary in terms of cloze probability. We also evaluated a more constrained variant of the prediction hypothesis, asking if the cerebellum facilitates the generation of semantic predictions when the content of a sentence refers to a dynamic rather than static mental transformation. The results failed to support either hypothesis: Compared to matched control participants (n = 17), individuals with cerebellar degeneration showed a similar reduction in reaction time for sentences with high cloze probability and no selective impairment in predictions involving dynamic transformations. These results challenge current theorizing about the role of the cerebellum in language processing, pointing to a misalignment between neuroimaging and neuropsychology research on this topic.

The Cerebellum Is Sensitive to the Lexical Properties of Words During Spoken Language Comprehension

Over the past few decades, research into the function of the cerebellum has expanded far beyond the motor domain. A growing number of studies are probing the role of specific cerebellar subregions, such as Crus I and Crus II, in higher-order cognitive functions including receptive language processing. In the current fMRI study, we show evidence for the cerebellum's sensitivity to variation in two well-studied psycholinguistic properties of words-lexical frequency and phonological neighborhood density-during passive, continuous listening of a podcast. To determine whether, and how, activity in the cerebellum correlates with these lexical properties, we modeled each word separately using an amplitude-modulated regressor, time-locked to the onset of each word. At the group level, significant effects of both lexical properties landed in expected cerebellar subregions: Crus I and Crus II. The BOLD signal correlated with variation in each lexical property, consistent with both language-specific and domain-general mechanisms. Activation patterns at the individual level also showed that effects of phonological neighborhood and lexical frequency landed in Crus I and Crus II as the most probable sites, though there was activation seen in other lobules (especially for frequency). Although the exact cerebellar mechanisms used during speech and language processing are not yet evident, these findings highlight the cerebellum's role in word-level processing during continuous listening.

Dissociating Cerebellar Regions Involved in Formulating and Articulating Words and Sentences

We investigated which parts of the cerebellum are involved in formulating and articulating sentences using (i) a sentence production task that involved describing simple events in pictures; (ii) an auditory sentence repetition task involving the same sentence articulation but not sentence formulation; and (iii) an auditory sentence-to-picture matching task that involved the same pictorial events and no overt articulation. Activation for each of these tasks was compared to the equivalent word processing tasks: noun production, verb production, auditory noun repetition, and auditory noun-to-picture matching. We associate activation in bilateral cerebellum lobule VIIb with sequencing words into sentences because it increased for sentence production compared to all other conditions and was also activated by word production compared to word matching. We associate a paravermal part of right cerebellar lobule VIIIb with overt motor execution of speech, because activation was higher during (i) production and repetition of sentences compared to the corresponding noun conditions and (ii) noun and verb production compared to all matching tasks, with no activation relative to fixation during any silent (nonspeaking) matching task. We associate activation within right cerebellar Crus II with covert articulatory activity because it activated for (i) all speech production more than matching tasks and (ii) sentences compared to nouns during silent (nonspeaking) matching as well as sentence production and sentence repetition. Our study serendipitously segregated, for the first time, three distinct functional roles for the cerebellum in generic speech production, and it demonstrated how sentence production enhanced the demands on these cerebellar regions.

Cerebellar Functions Beyond Movement and Learning

The cerebellum has a well-established role in controlling motor functions, including coordination, posture, and the learning of skilled movements. The mechanisms for how it carries out motor behavior remain under intense investigation. Interestingly though, in recent years the mechanisms of cerebellar function have faced additional scrutiny since nonmotor behaviors may also be controlled by the cerebellum. With such complexity arising, there is now a pressing need to better understand how cerebellar structure, function, and behavior intersect to influence behaviors that are dynamically called upon as an animal experiences its environment. Here, we discuss recent experimental work that frames possible neural mechanisms for how the cerebellum shapes disparate behaviors and why its dysfunction is catastrophic in hereditary and acquired conditions-both motor and nonmotor. For these reasons, the cerebellum might be the ideal therapeutic target.

Structured connectivity in the output of the cerebellar cortex

The spatial organization of a neuronal circuit is critically important for its function since the location of neurons is often associated with function. In the cerebellum, the major output of the cerebellar cortex are synapses made from Purkinje cells onto neurons in the cerebellar nuclei, yet little has been known about the spatial organization of these synapses. We explored this question using whole-cell electrophysiology and optogenetics in acute sagittal cerebellar slices to produce spatial connectivity maps of cerebellar cortical output in mice. We observed non-random connectivity where Purkinje cell inputs clustered in cerebellar transverse zones: while many nuclear neurons received inputs from a single zone, several multi-zonal connectivity motifs were also observed. Single neurons receiving input from all four zones were overrepresented in our data. These findings reveal that the output of the cerebellar cortex is spatially structured and represents a locus for multimodal integration in the cerebellum.

Selective recruitment of the cerebellum evidenced by task-dependent gating of inputs

Functional magnetic resonance imaging (fMRI) studies have documented cerebellar activity across a wide array of tasks. However, the functional contribution of the cerebellum within these task domains remains unclear because cerebellar activity is often studied in isolation. This is problematic, as cerebellar fMRI activity may simply reflect the transmission of neocortical activity through fixed connections. Here, we present a new approach that addresses this problem. Rather than focus on task-dependent activity changes in the cerebellum alone, we ask if neocortical inputs to the cerebellum are gated in a task-dependent manner. We hypothesize that input is upregulated when the cerebellum functionally contributes to a task. We first validated this approach using a finger movement task, where the integrity of the cerebellum has been shown to be essential for the coordination of rapid alternating movements but not for force generation. While both neocortical and cerebellar activity increased with increasing speed and force, the speed-related changes in the cerebellum were larger than predicted by an optimized cortico-cerebellar connectivity model. We then applied the same approach in a cognitive domain, assessing how the cerebellum supports working memory. Enhanced gating was associated with the encoding of items in working memory, but not with the manipulation or retrieval of the items. Focusing on task-dependent gating of neocortical inputs to the cerebellum offers a promising approach for using fMRI to understand the specific contributions of the cerebellum to cognitive function.

Cerebellar Heterogeneity and Selective vulnerability in Spinocerebellar Ataxia Type 1 (SCA1)

Heterogeneity is one of the key features of the healthy brain and selective vulnerability characterizes many, if not all, neurodegenerative diseases. While cerebellum contains majority of brain cells, neither its heterogeneity nor selective vulnerability in disease are well understood. Here we describe molecular, cellular and functional heterogeneity in the context of healthy cerebellum as well as in cerebellar disease Spinocerebellar Ataxia Type 1 (SCA1). We first compared disease pathology in cerebellar vermis and hemispheres across anterior to posterior axis in a knock-in SCA1 mouse model. Using immunohistochemistry, we demonstrated earlier and more severe pathology of PCs and glia in the posterior cerebellar vermis of SCA1 mice. We also demonstrate heterogeneity of Bergmann glia in the unaffected, wild-type mice. Then, using RNA sequencing, we found both shared, as well as, posterior cerebellum-specific molecular mechanisms of pathogenesis that include exacerbated gene dysregulation, increased number of altered signaling pathways, and decreased pathway activity scores in the posterior cerebellum of SCA1 mice. We demonstrated unexpectedly large differences in the gene expression between posterior and anterior cerebellar vermis of wild-type mice, indicative of robust intraregional heterogeneity of gene expression in the healthy cerebellum. Additionally, we found that SCA1 disease profoundly reduces intracerebellar heterogeneity of gene expression. Further, using fiber photometry, we found that population level PC calcium activity was altered in the posterior lobules in SCA1 mice during walking. We also identified regional differences in the population level activity of Purkinje cells (PCs) in unrestrained wild-type mice that were diminished in SCA1 mice.

A Functional Atlas of the Cerebellum Based on NeuroSynth Task Coordinates

Although the human cerebellum has a surface that is about 80% of that of the cerebral cortex and has about four times as many neurons, its functional organization is still very much uncharted. Despite recent attempts to provide resting-state and task-based parcellations of the cerebellum, these two approaches lead to large discrepancies. This article describes a comprehensive task-based functional parcellation of the human cerebellum based on a large-scale functional database, NeuroSynth, involving an unprecedented diversity of tasks, which were reliably associated with ontological key terms referring to psychological functions. Involving over 44,500 participants from this database, we present a parcellation that exhibits replicability with earlier resting-state parcellations across cerebellar and neocortical structures. The functional parcellation of the cerebellum confirms the major networks revealed in prior work, including sensorimotor, directed (dorsal) attention, divided (ventral) attention, executive control, mentalizing (default mode) networks, tiny patches of a limbic network, and also a unilateral language network (but not the visual network), and the association of these networks with underlying ontological key terms confirms their major functionality. The networks are revealed at locations that are roughly similar to prior resting-state cerebellar parcellations, although they are less symmetric and more fragmented across the two hemispheres. This functional parcellation of the human cerebellum and associated key terms can provide a useful guide in designing studies to test specific functional hypotheses and provide a reference for interpreting the results.

Aberrant dynamic functional network connectivity in progressive supranuclear palsy

BACKGROUND

The clinical symptoms of progressive supranuclear palsy (PSP) may be mediated by aberrant dynamic functional network connectivity (dFNC). While earlier research has found altered functional network connections in PSP patients, the majority of those studies have concentrated on static functional connectivity. Nevertheless, in this study, we sought to evaluate the modifications in dynamic characteristics and establish the correlation between these disease-related changes and clinical variables.

METHODS

In our study, we conducted a study on 53 PSP patients and 65 normal controls. Initially, we employed a group independent component analysis (ICA) to derive resting-state networks (RSNs), while employing a sliding window correlation approach to produce dFNC matrices. The K-means algorithm was used to cluster these matrices into distinct dynamic states, and then state analysis was subsequently employed to analyze the dFNC and temporal metrics between the two groups. Finally, we made a correlation analysis.

RESULTS

PSP patients showed increased connectivity strength between medulla oblongata (MO) and visual network (VN) /cerebellum network (CBN) and decreased connections were found between default mode network (DMN) and VN/CBN, subcortical cortex network (SCN) and CBN. In addition, PSP patients spend less fraction time and shorter dwell time in a diffused state, especially the MO and SCN. Finally, the fraction time and mean dwell time in the distributed connectivity state (state 2) is negatively correlated with duration, bulbar and oculomotor symptoms.

DISCUSSION

Our findings were that the altered connectivity was mostly concentrated in the CBN and MO. In addition, PSP patients had different temporal dynamics, which were associated with bulbar and oculomotor symptoms in PSPRS. It suggest that variations in dynamic functional network connectivity properties may represent an essential neurological mechanism in PSP.

Insights into the genetic architecture of cerebellar lobules derived from the UK Biobank

In this work we endeavor to further understand the genetic architecture of the cerebellum by examining the genetic underpinnings of the different cerebellar lob(ul)es, identifying their genetic relation to cortical and subcortical regions, as well as to psychiatric disorders, as well as traces of their evolutionary trajectories. We confirm the moderate heritability of cerebellar volumes, and reveal genetic clustering and variability across their different substructures, which warranted a detailed analysis using this higher structural resolution. We replicated known genetic correlations with several subcortical volumes, and report new cortico-cerebellar genetic correlations, including negative genetic correlations between anterior cerebellar lobules and cingulate, and positive ones between lateral Crus I and lobule VI with cortical measures in the fusiform region. Heritability partitioning for evolutionary annotations highlighted that the vermis of Crus II has depleted heritability in genomic regions of "archaic introgression deserts", but no enrichment/depletion of heritability in any other cerebellar regions. Taken together, these findings reveal novel insights into the genetic underpinnings of the different cerebellar lobules.

Fetal brain MRI atlases and datasets: A review

Fetal brain development is a complex process involving different stages of growth and organization which are crucial for the development of brain circuits and neural connections. Fetal atlases and labeled datasets are promising tools to investigate prenatal brain development. They support the identification of atypical brain patterns, providing insights into potential early signs of clinical conditions. In a nutshell, prenatal brain imaging and post-processing via modern tools are a cutting-edge field that will significantly contribute to the advancement of our understanding of fetal development. In this work, we first provide terminological clarification for specific terms (i.e., "brain template" and "brain atlas"), highlighting potentially misleading interpretations related to inconsistent use of terms in the literature. We discuss the major structures and neurodevelopmental milestones characterizing fetal brain ontogenesis. Our main contribution is the systematic review of 18 prenatal brain atlases and 3 datasets. We also tangentially focus on clinical, research, and ethical implications of prenatal neuroimaging.

The cerebellum acts as the analog to the medial temporal lobe for sensorimotor memory

The cerebellum is critical for sensorimotor learning. The specific contribution that it makes, however, remains unclear. Inspired by the classic finding that, for declarative memories, medial temporal lobe structures provide a gateway to the formation of long-term memory but are not required for short-term memory, we hypothesized that, for sensorimotor memories, the cerebellum may play an analogous role. Here we studied the sensorimotor learning of individuals with severe ataxia from cerebellar degeneration. We dissected the memories they formed during sensorimotor learning into a short-term temporally-volatile component, that decays rapidly with a time constant of just 15-20sec and thus cannot lead to long-term retention, and a longer-term temporally-persistent component that is stable for 60 sec or more and leads to long-term retention. Remarkably, we find that these individuals display dramatically reduced levels of temporally-persistent sensorimotor memory, despite spared and even elevated levels of temporally-volatile sensorimotor memory. In particular, we find both impairment that systematically increases with memory window duration over shorter memory windows (<12 sec) and near-complete impairment of memory maintenance over longer memory windows (>25 sec). This dissociation uncovers a new role for the cerebellum as a gateway for the formation of long-term but not short-term sensorimotor memories, mirroring the role of the medial temporal lobe for declarative memories. It thus reveals the existence of distinct neural substrates for short-term and long-term sensorimotor memory, and it explains both newly-identified trial-to-trial differences and long-standing study-to-study differences in the effects of cerebellar damage on sensorimotor learning ability.

Significance Statement

A key discovery about the neural underpinnings of memory, made more than half a century ago, is that long-term, but not short-term, memory formation depends on neural structures in the brain's medial temporal lobe (MTL). However, this dichotomy holds only for declarative memories - memories for explicit facts such as names and dates - as long-term procedural memories - memories for implicit knowledge such as sensorimotor skills - are largely unaffected even with substantial MTL damage. Here we demonstrate that the formation of long-term, but not short-term, sensorimotor memory depends on a neural structure known as the cerebellum, and we show that this finding explains the variability previously reported in the extent to which cerebellar damage affects sensorimotor learning.

New Insights into the Neuropsychological Profile and Intellectual Quotient Variability in Joubert Syndrome Compared to Other Congenital Cerebellar Malformations

The neuropsychological characteristics of the cerebellar cognitive affective syndrome (CCAS) in congenital, non-progressive malformations of the cerebellum have been scarcely investigated, and even less is known for Joubert syndrome (JS), an inherited, non-progressive cerebellar ataxia characterized by the so-called molar tooth sign. The few studies on this topic reported inconsistent results about intellectual functioning and specific neuropsychological impairments. The aim of this research is to examine the neuropsychological profile of JS compared to other congenital cerebellar malformations (CM), considering individual variability of intellectual quotient (IQ) in the two groups. Fourteen patients with JS and 15 patients with CM aged 6-25 years were tested through a comprehensive, standardized neuropsychological battery. Their scores in the neuropsychological domains were inspected through descriptive analysis and compared by mean of MANOVA and ANOVA models, then replicated inserting IQ as covariate. The two groups showed a largely overlapping neuropsychological profile, consistent with CCAS. However, the JS group showed worse performance in visual-spatial memory compared to CM patients, although this difference was mitigated when considering IQ. These findings highlight a divergence between JS and other CM in visual-spatial memory, which might suggest a critical role of the cerebellum in recalling task-relevant memories and might inform rehabilitative interventions.

Sex Differences and Behavioral Associations with Typically Developing Pediatric Regional Cerebellar Gray Matter Volume

The cerebellum contributes to motor and higher-order control throughout neurodevelopment, with marked growth during childhood. Few studies have investigated differential associations of cerebellar morphometry with function in males and females. The present study examines sex differences in regional cerebellar gray matter volume (GMV) and the moderating effect of sex on the relationship between GMV and motor, cognitive, and emotional functions in a large cohort of typically developing (TD) children. Participants included 371 TD children (123 females, age 8-12 years). A convolutional neural network-based approach was employed for cerebellar parcellation. Volumes were harmonized using ComBat to adjust for hardware-induced variations. Regression analyses examined the effect of sex on GMV and whether sex moderated the relationship between GMV and motor, cognitive, and emotional functions. Males showed larger GMV in right lobules I-V, bilateral lobules VI, crus II/VIIb, and VIII, left lobule X, and vermis regions I-V and VIII-X. Greater motor function correlated with less vermis VI-VII GMV in females. Greater cognitive function correlated with greater left lobule VI GMV in females and less left lobule VI GMV in males. Finally, greater internalizing symptoms correlated with greater bilateral lobule IX GMV in females but less in males. These findings reveal sexually dimorphic patterns of cerebellar structure and associations with motor, cognitive, and emotional functions. Males generally show larger GMV than females. Larger GMV was associated with better cognitive functioning for females and better motor/emotional functioning for males.

Smaller Cerebellar Lobule VIIb is Associated with Tremor Severity in Parkinson's Disease

Alterations in the cerebellum's morphology in Parkinson's disease (PD) point to its pathophysiological involvement in this movement disorder. Such abnormalities have previously been attributed to different PD motor subtypes. The aim of the study was to relate volumes of specific cerebellar lobules to motor symptom severity, in particular tremor (TR), bradykinesia/rigidity (BR), and postural instability and gait disorders (PIGD) in PD. We performed a volumetric analysis based on T1-weighted MRI images of 55 participants with PD (22 females, median age 65 years, Hoehn and Yahr stage 2). Multiple regression models were fitted to investigate associations between volumes of cerebellar lobules with clinical symptom severity based on MDS-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III score and sub-scores for TR, BR, and PIGD; adjusted for age, sex, disease duration, and intercranial volume as cofactors. Smaller volume of lobule VIIb was associated with higher tremor severity (P = 0.004). No structure-function relationships were detected for other lobules or other motor symptoms. This distinct structural association denotes the involvement of the cerebellum in PD tremor. Characterizing morphological features of the cerebellum leads to a better understanding of its role in the spectrum of motor symptoms in PD and contributes further to identifying potential biological markers.

Unraveling individual differences in learning potential: A dynamic framework for the case of reading development

Children show an enormous capacity to learn during development, but with large individual differences in the time course and trajectory of learning and the achieved skill level. Recent progress in developmental sciences has shown the contribution of a multitude of factors including genetic variation, brain plasticity, socio-cultural context and learning experiences to individual development. These factors interact in a complex manner, producing children's idiosyncratic and heterogeneous learning paths. Despite an increasing recognition of these intricate dynamics, current research on the development of culturally acquired skills such as reading still has a typical focus on snapshots of children's performance at discrete points in time. Here we argue that this 'static' approach is often insufficient and limits advancements in the prediction and mechanistic understanding of individual differences in learning capacity. We present a dynamic framework which highlights the importance of capturing short-term trajectories during learning across multiple stages and processes as a proxy for long-term development on the example of reading. This framework will help explain relevant variability in children's learning paths and outcomes and fosters new perspectives and approaches to study how children develop and learn.

Using rare genetic mutations to revisit structural brain asymmetry

Asymmetry between the left and right hemisphere is a key feature of brain organization. Hemispheric functional specialization underlies some of the most advanced human-defining cognitive operations, such as articulated language, perspective taking, or rapid detection of facial cues. Yet, genetic investigations into brain asymmetry have mostly relied on common variants, which typically exert small effects on brain-related phenotypes. Here, we leverage rare genomic deletions and duplications to study how genetic alterations reverberate in human brain and behavior. We designed a pattern-learning approach to dissect the impact of eight high-effect-size copy number variations (CNVs) on brain asymmetry in a multi-site cohort of 552 CNV carriers and 290 non-carriers. Isolated multivariate brain asymmetry patterns spotlighted regions typically thought to subserve lateralized functions, including language, hearing, as well as visual, face and word recognition. Planum temporale asymmetry emerged as especially susceptible to deletions and duplications of specific gene sets. Targeted analysis of common variants through genome-wide association study (GWAS) consolidated partly diverging genetic influences on the right versus left planum temporale structure. In conclusion, our gene-brain-behavior data fusion highlights the consequences of genetically controlled brain lateralization on uniquely human cognitive capacities.

A cerebro-cerebellar network for learning visuomotor associations

Consensus is rapidly building to support a role for the cerebellum beyond motor function, but its contributions to non-motor learning remain poorly understood. Here, we provide behavioral, anatomical and computational evidence to demonstrate a causal role for the primate posterior lateral cerebellum in learning new visuomotor associations. Reversible inactivation of the posterior lateral cerebellum of male monkeys impeded the learning of new visuomotor associations, but had no effect on movement parameters, or on well-practiced performance of the same task. Using retrograde transneuronal transport of rabies virus, we identified a distinct cerebro-cerebellar network linking Purkinje cells in the posterior lateral cerebellum with a region of the prefrontal cortex that is critical in learning visuomotor associations. Together, these results demonstrate a causal role for the primate posterior lateral cerebellum in non-motor, reinforcement learning.

Dynamic functional changes upon thalamotomy in essential tremor depend on baseline brain morphometry

Patients with drug-resistant essential tremor (ET) may undergo Gamma Knife stereotactic radiosurgical thalamotomy (SRS-T), where the ventro-intermediate nucleus of the thalamus (Vim) is lesioned by focused beams of gamma radiations to induce clinical improvement. Here, we studied SRS-T impacts on left Vim dynamic functional connectivity (dFC, n = 23 ET patients scanned before and 1 year after intervention), and on surface-based morphometric brain features (n = 34 patients, including those from dFC analysis). In matched healthy controls (HCs), three dFC states were extracted from resting-state functional MRI data. In ET patients, state 1 spatial stability increased upon SRS-T (F1,22 = 19.13, p = 0.004). More frequent expression of state 3 over state 1 before SRS-T correlated with greater clinical recovery in a way that depended on the MR signature volume (t6 = 4.6, p = 0.004). Lower pre-intervention spatial variability in state 3 expression also did (t6 = - 4.24, p = 0.005) and interacted with the presence of familial ET so that these patients improved less (t6 = 4.14, p = 0.006). ET morphometric profiles showed significantly lower similarity to HCs in 13 regions upon SRS-T (z ≤ - 3.66, p ≤ 0.022), and a joint analysis revealed that before thalamotomy, morphometric similarity and states 2/3 mean spatial similarity to HCs were anticorrelated, a relationship that disappeared upon SRS-T (z ≥ 4.39, p < 0.001). Our results show that left Vim functional dynamics directly relates to upper limb tremor lowering upon intervention, while morphometry instead has a supporting role in reshaping such dynamics.

Emergence of syntax and word prediction in an artificial neural circuit of the cerebellum

The cerebellum, interconnected with the cerebral neocortex, plays a vital role in human-characteristic cognition such as language processing, however, knowledge about the underlying circuit computation of the cerebellum remains very limited. To gain a better understanding of the computation underlying cerebellar language processing, we developed a biologically constrained cerebellar artificial neural network (cANN) model, which implements the recently identified cerebello-cerebellar recurrent pathway. We found that while cANN acquires prediction of future words, another function of syntactic recognition emerges in the middle layer of the prediction circuit. The recurrent pathway of the cANN was essential for the two language functions, whereas cANN variants with further biological constraints preserved these functions. Considering the uniform structure of cerebellar circuitry across all functional domains, the single-circuit computation, which is the common basis of the two language functions, can be generalized to fundamental cerebellar functions of prediction and grammar-like rule extraction from sequences, that underpin a wide range of cerebellar motor and cognitive functions. This is a pioneering study to understand the circuit computation of human-characteristic cognition using biologically-constrained ANNs.

Understanding the role of AMPA receptors in autism: insights from circuit and synapse dysfunction

Autism spectrum disorders represent a diverse etiological spectrum that converge on a syndrome characterized by discrepant deficits in developmental domains often highlighted by concerns in socialization, sensory integration, and autonomic functioning. Importantly, the incidence and prevalence of autism spectrum disorders have seen sharp increases since the syndrome was first described in the 1940s. The wide etiological spectrum and rising number of individuals being diagnosed with the condition lend urgency to capturing a more nuanced understanding of the pathogenic mechanisms underlying the autism spectrum disorders. The current review seeks to understand how the disruption of AMPA receptor (AMPAr)-mediated neurotransmission in the cerebro-cerebellar circuit, particularly in genetic autism related to SHANK3 or SYNGAP1 protein dysfunction function and autism associated with in utero exposure to the anti-seizure medications valproic acid and topiramate, may contribute to the disease presentation. Initially, a discussion contextualizing AMPAr signaling in the cerebro-cerebellar circuitry and microstructural circuit considerations is offered. Subsequently, a detailed review of the literature implicating mutations or deletions of SHANK3 and SYNGAP1 in disrupted AMPAr signaling reveals how bidirectional pathogenic modulation of this key circuit may contribute to autism. Finally, how pharmacological exposure may interact with this pathway, via increased risk of autism diagnosis with valproic acid and topiramate exposure and potential treatment of autism using AMPAr modulator perampanel, is discussed. Through the lens of the review, we will offer speculation on how neuromodulation may be used as a rational adjunct to therapy. Together, the present review seeks to synthesize the disparate considerations of circuit understanding, genetic etiology, and pharmacological modulation to understand the mechanistic interaction of this important and complex disorder.

Aging, Neurodegenerative Disorders, and Cerebellum

An important part of the central nervous system (CNS), the cerebellum is involved in motor control, learning, reflex adaptation, and cognition. Diminished cerebellar function results in the motor and cognitive impairment observed in patients with neurodegenerative disorders such as Alzheimer's disease (AD), vascular dementia (VD), Parkinson's disease (PD), Huntington's disease (HD), spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), Friedreich's ataxia (FRDA), and multiple sclerosis (MS), and even during the normal aging process. In most neurodegenerative disorders, impairment mainly occurs as a result of morphological changes over time, although during the early stages of some disorders such as AD, the cerebellum also serves a compensatory function. Biological aging is accompanied by changes in cerebellar circuits, which are predominantly involved in motor control. Despite decades of research, the functional contributions of the cerebellum and the underlying molecular mechanisms in aging and neurodegenerative disorders remain largely unknown. Therefore, this review will highlight the molecular and cellular events in the cerebellum that are disrupted during the process of aging and the development of neurodegenerative disorders. We believe that deeper insights into the pathophysiological mechanisms of the cerebellum during aging and the development of neurodegenerative disorders will be essential for the design of new effective strategies for neuroprotection and the alleviation of some neurodegenerative disorders.

New Frontiers for the Understanding of Aging: The Power and Possibilities of Studying the Cerebellum

Understanding behavior in aging has benefited greatly from cognitive neuroscience. Our foundational understanding of the brain in advanced age is based on what now amounts to several decades of work demonstrating differences in brain structure, network organization, and function. Earlier work in this field was focused primarily on the prefrontal cortex and hippocampus. More recent evidence has expanded our understanding of the aging brain to also implicate the cerebellum. Recent frameworks have suggested that the cerebellum may act as scaffolding for cortical function, and there is an emerging literature implicating the structure in Alzheimer's disease. At this juncture, there is evidence highlighting the potential importance of the cerebellum in advanced age, though the field of study is relatively nascent. Here, we provide an overview of key findings in the literature as it stands now and highlight several key future directions for study with respect to the cerebellum in aging.