Cerebellar Control of Balance and Locomotion

Effects of cerebellar transcranial direct current stimulation on the excitability of spinal motor neurons and vestibulospinal tract in healthy individuals

Cerebellar transcranial direct current stimulation (ctDCS) modulates cerebellar cortical excitability in a polarity-dependent manner and affects inhibitory pathways from the cerebellum. The cerebellum modulates spinal reflex excitability via the vestibulospinal tract and other pathways projecting to the spinal motor neurons; however, the effects of ctDCS on the excitability of spinal motor neurons and vestibulospinal tract remain unclear. The experiment involved 13 healthy individuals. ctDCS (sham-ctDCS, anodal-ctDCS, and cathodal-ctDCS) was applied to the cerebellar vermis at 2 mA with an interval of at least 3 days between each condition. We measured the maximal M-wave (Mmax) and maximal H-reflex (Hmax) in the right soleus muscle to assess the excitability of spinal motor neurons. We applied galvanic vestibular stimulation (GVS) for 200 ms at 100 ms before tibial nerve stimulation to measure Hmax conditioned by GVS (GVS-Hmax) and calculated the change rate of Hmax by GVS as the excitability of vestibulospinal tract. We measured the Mmax, Hmax, and GVS-Hmax before, during, and after ctDCS in the sitting posture. No main effects of tDCS condition, main effects of time, or interaction effects were observed in Hmax/Mmax or the change rate of Hmax by GVS. It has been suggested that ctDCS does not affect the excitability of spinal motor neurons and vestibulospinal tract, as measured by neurophysiological methods, such as the H-reflex, in healthy individuals in a sitting posture. Effect of ctDCS on other descending pathways to spinal motor neurons, the neurological mechanism of tDCS and the cerebellar activity during the experiment may have contributed to these results. Therefore, we need to investigate the involvement of the cerebellum in Hmax/Mmax and the change rate of Hmax by GVS under different neuromodulation techniques and postural conditions.

Quantitative Gait and Balance Outcomes for Ataxia Trials: Consensus Recommendations by the Ataxia Global Initiative Working Group on Digital-Motor Biomarkers

With disease-modifying drugs on the horizon for degenerative ataxias, ecologically valid, finely granulated, digital health measures are highly warranted to augment clinical and patient-reported outcome measures. Gait and balance disturbances most often present as the first signs of degenerative cerebellar ataxia and are the most reported disabling features in disease progression. Thus, digital gait and balance measures constitute promising and relevant performance outcomes for clinical trials.This narrative review with embedded consensus will describe evidence for the sensitivity of digital gait and balance measures for evaluating ataxia severity and progression, propose a consensus protocol for establishing gait and balance metrics in natural history studies and clinical trials, and discuss relevant issues for their use as performance outcomes.

Video-Based Kinematic Analysis of Movement Quality in a Phase 3 Clinical Trial of Troriluzole in Adults with Spinocerebellar Ataxia: A Post Hoc Analysis

INTRODUCTION

Traditional methods for assessing movement quality rely on subjective standardized scales and clinical expertise. This limitation creates challenges for assessing patients with spinocerebellar ataxia (SCA), in whom changes in mobility can be subtle and varied. We hypothesized that a machine learning analytic system might complement traditional clinician-rated measures of gait. Our objective was to use a video-based assessment of gait dispersion to compare the effects of troriluzole with placebo on gait quality in adults with SCA.

METHODS

Participants with SCA underwent gait assessment in a phase 3, double-blind, placebo-controlled trial of troriluzole (NCT03701399). Videos were processed through a deep learning pose extraction algorithm, followed by the estimation of a novel gait stability measure, the Pose Dispersion Index, quantifying the frame-by-frame symmetry, balance, and stability during natural and tandem walk tasks. The effects of troriluzole treatment were assessed in mixed linear models, participant-level grouping, and treatment group-by-visit week interaction adjusted for age, sex, baseline modified Functional Scale for the Assessment and Rating of Ataxia (f-SARA), and time since diagnosis.

RESULTS

From 218 randomized participants, 67 and 56 participants had interpretable videos of a tandem and natural walk attempt, respectively. At Week 48, individuals assigned to troriluzole exhibited significant (p = 0.010) improvement in tandem walk Pose Dispersion Index versus placebo {adjusted interaction coefficient: 0.584 [95% confidence interval (CI) 0.137 to 1.031]}. A similar, nonsignificant trend was observed in the natural walk assessment [coefficient: 1.198 (95% CI - 1.067 to 3.462)]. Further, lower baseline Pose Dispersion Index during the natural walk was significantly (p = 0.041) associated with a higher risk of subsequent falls [adjusted Poisson coefficient: - 0.356 [95% CI - 0.697 to - 0.014)].

CONCLUSION

Using this novel approach, troriluzole-treated subjects demonstrated improvement in gait as compared to placebo for the tandem walk. Machine learning applied to video-captured gait parameters can complement clinician-reported motor assessment in adults with SCA. The Pose Dispersion Index may enhance assessment in future research. TRIAL REGISTRATION-CLINICALTRIALS.

GOV IDENTIFIER

NCT03701399.

Effects of Anodal tDCS Applied Over the Cerebellum Combined with Physical Therapy on Center of Gravity Sway in a Patient with Cerebellar Ataxia: A Single-Case Study

Damage to the cerebellum results in dysfunctional standing postural control. Patients with cerebellar ataxia have a larger sway in the center of gravity (COG) while standing. Transcranial direct current stimulation (tDCS) has been applied in the rehabilitation of patients with central nervous system disorders; however, its effect on COG sway in patients with cerebellar ataxia remains unknown. We aimed to confirm the effects of anodal cerebellar tDCS (ctDCS) combined with physical therapy on COG sway in a patient with cerebellar ataxia using a retrospective ABA single-case study design. This study involved a patient with left cerebellar hemorrhage. Walking and postural balance rehabilitation were conducted in phase A. Anodal ctDCS was combined with the walking and postural balance rehabilitation in phase B. We measured COG sway in the open- and closed-eyes standing conditions daily throughout all the phases. In the open-eyes standing condition, there was no significant change in COG sway in phase B. Conversely, in the closed-eyes standing condition, the circumferential area, total sway path length, and anteroposterior sway path length decreased in phase B. No change was observed in the mediolateral sway path length. The combination of anodal ctDCS and physical therapy may decrease COG sway in patients with cerebellar ataxia in the closed-eyes standing condition, and its effect may be greater in the anteroposterior direction.

The effects of corticotropin-releasing factor on motor learning

Corticotropin-releasing factor (CRF) is mainly secreted from the hypothalamic paraventricular nuclei and plays a crucial role in stress-related responses. Recent studies have reported that CRF is a neuromodulator in the central nervous system. In the cerebellum, CRF is essential for the induction of long-term depression (LTD) at the parallel fiber-Purkinje cell synapses. Given that LTD is thought to be one of the fundamental mechanisms of motor learning, CRF may affect motor learning. However, the role of CRF in motor learning in vivo remains unclear. In this study, we aimed to examine the role of CRF in motor learning. This was achieved through a series of behavioral experiments involving the in vivo administration of CRF and its antagonists. Rats injected with CRF directly into the cerebellum exhibited superior performance on the rotarod test, especially during initial training phases, compared to control subjects. Conversely, rats receiving a CRF receptor antagonist demonstrated reduced endurance on the rotating rod compared to controls. Notably, CRF mRNA expression levels in the cerebellum did not show significant variance between the CRF-injected and control groups. These findings imply a critical role of endogenous CRF in cerebellar motor learning and suggest that exogenous CRF can augment this process. (199 words).

Understanding mechanisms of generalization following locomotor adaptation

Our nervous system has the remarkable ability to adapt our gait to accommodate changes in our body or surroundings. However, our adapted walking patterns often generalize only partially (or not at all) between different contexts. Here, we sought to understand how the nervous system generalizes adapted gait patterns from one context to another. Through a series of split-belt treadmill walking experiments, we evaluated different mechanistic hypotheses to explain the partial generalization of adapted gait patterns from split-belt treadmill to overground walking. In support of the credit assignment hypothesis, our experiments revealed the central finding that adaptation involves recalibration of two distinct forward models. Recalibration of the first model generalizes to overground walking, suggesting that the model represents the general movement dynamics of our body. On the other hand, recalibration of the second model does not generalize to overground walking, suggesting the model represents dynamics specific to treadmill walking. These findings reveal that there is a predefined portion of forward model recalibration that generalizes across context, leading to overall partial generalization of walking adaptation.

Preclinical investigation of the effect of stress on the binding of [18F]F13640, a 5-HT1A radiopharmaceutical

BACKGROUND

[18F]F13640 is a new PET radiopharmaceutical for brain molecular imaging of serotonin 5-HT1A receptors. Since we intend to use this radiopharmaceutical in psychiatric studies, it is crucial to establish possible sensitivity modification of 5-HT1A receptors availability during an acute stress exposure. In this study, we first assessed the cerebrometabolic effects of a new animal model of stress with [18F]FDG and then proceeded to test for effects of this model on the cerebral binding of [18F]F13640, a 5-HT1A receptors PET radiopharmaceutical.

METHODS

Four groups of male Sprague-Dawley were used to identify the optimal model: "stressed group" (n = 10), "post-traumatic stress disorder (PTSD) group" (n = 9) and "restraint group" (n = 8), compared with a control group (n = 8). All rats performed neuroimaging [18F]FDG μPET-CT to decipher which model was the most appropriate to test effects of stress on radiotracer binding. Subsequently, a group of rats (n = 10) underwent two PET imaging acquisitions (baseline and PTSD condition) using the PET radiopharmaceutical [18F]F13640 to assess influence of stress on its binding. Voxel-based analysis was performed to assess [18F]FDG or [18F]F13640 changes.

RESULTS

In [18F]FDG experiments, the PTSD group showed a pattern of cerebrometabolic activation in various brain regions previously implicated in stress (amygdala, perirhinal cortex, olfactory bulb and caudate). [18F]F13640 PET scans showed increased radiotracer binding in the PTSD condition in caudate nucleus and brainstem.

CONCLUSIONS

The present study demonstrated stress-induced cerebrometabolic activation or inhibition of various brain regions involved in stress model. Applying this model to our radiotracer, [18F]F13640 showed few influence of stress on its binding. This will enable to rule out any confounding effect of stress during imaging studies.

Gait rhythm analysis as a new continuous scale for cerebellar ataxia: Power law and lognormal components represent the ataxic gait quantity

We estimated the severity of cerebellar ataxia by analyzing gait rhythm. We measured the step times in patients with pure cerebellar ataxia and healthy controls and then analyzed the distribution of the ratios of adjacent times. Gait rhythm displayed the best adaptation when expressed as the sum of the power law and lognormal distributions in both groups, and the groups could be distinguished by the exponent of the power law distribution, reflecting the fractal property of gait rhythm. Gait rhythm might reflect different features of impairment in patients with cerebellar ataxia, making it a useful continuous scale for cerebellar ataxia.

Effects of Cerebellar Non-Invasive Stimulation on Neurorehabilitation in Stroke Patients: An Updated Systematic Review

The cerebellum is emerging as a promising target for noninvasive brain stimulation (NIBS). A systematic review was conducted to evaluate the effects of cerebellar NIBS on both motor and other symptoms in stroke rehabilitation, its impact on functional ability, and potential side effects (PROSPERO number: CRD42022365697). A systematic electronic database search was performed by using PubMed Central (PMC), EMBASE, and Web of Science, with a cutoff date of November 2023. Data extracted included study details, NIBS methodology, outcome measures, and results. The risk of bias in eligible studies was also assessed. Twenty-two clinical studies involving 1016 participants were finally included, with a focus on outcomes related to post-stroke motor recovery (gait and balance, muscle spasticity, and upper limb dexterity) and other functions (dysphagia and aphasia). Positive effects were observed, especially on motor functions like gait and balance. Some efficiency was also observed in dysphagia rehabilitation. However, findings on language recovery were preliminary and inconsistent. A slight improvement in functional ability was noted, with no serious adverse effects reported. Further studies are needed to explore the effects of cerebellar NIBS on post-stroke non-motor deficits and to understand how cerebellar engagement can facilitate more precise treatment strategies for stroke rehabilitation.

Improvement of the thalamocortical white matter network in people with stable treated relapsing-remitting multiple sclerosis over time

Advanced imaging techniques (tractography) enable the mapping of white matter (WM) pathways and the understanding of brain connectivity patterns. We combined tractography with a network-based approach to examine WM microstructure on a network level in people with relapsing-remitting multiple sclerosis (pw-RRMS) and healthy controls (HCs) over 2 years. Seventy-six pw-RRMS matched with 43 HCs underwent clinical assessments and 3T MRI scans at baseline (BL) and 2-year follow-up (2-YFU). Probabilistic tractography was performed, accounting for the effect of lesions, producing connectomes of 25 million streamlines. Network differences in fibre density across pw-RRMS and HCs at BL and 2-YFU were quantified using network-based statistics (NBS). Longitudinal network differences in fibre density were quantified using NBS in pw-RRMS, and were tested for correlations with disability, cognition and fatigue scores. Widespread network reductions in fibre density were found in pw-RRMS compared with HCs at BL in cortical regions, with more reductions detected at 2-YFU. Pw-RRMS had reduced fibre density at BL in the thalamocortical network compared to 2-YFU. This effect appeared after correction for age, was robust across different thresholds, and did not correlate with lesion volume or disease duration. Pw-RRMS demonstrated a robust and long-distance improvement in the thalamocortical WM network, regardless of age, disease burden, duration or therapy, suggesting a potential locus of neuroplasticity in MS. This network's role over the disease's lifespan and its potential implications in prognosis and treatment warrants further investigation.

Heritability of cerebellar subregion volumes in adolescent and young adult twins

Twin studies have found gross cerebellar volume to be highly heritable. However, whether fine-grained regional volumes within the cerebellum are similarly heritable is still being determined. Anatomical MRI scans from two independent datasets (QTIM: Queensland Twin IMaging, N = 798, mean age 22.1 years; QTAB: Queensland Twin Adolescent Brain, N = 396, mean age 11.3 years) were combined with an optimised and automated cerebellum parcellation algorithm to segment and measure 28 cerebellar regions. We show that the heritability of regional volumetric measures varies widely across the cerebellum (h 2 $$ {h}^2 $$ 47%-91%). Additionally, the good to excellent test-retest reliability for a subsample of QTIM participants suggests that non-genetic variance in cerebellar volumes is due primarily to unique environmental influences rather than measurement error. We also show a consistent pattern of strong associations between the volumes of homologous left and right hemisphere regions. Associations were predominantly driven by genetic effects shared between lobules, with only sparse contributions from environmental effects. These findings are consistent with similar studies of the cerebrum and provide a first approximation of the upper bound of heritability detectable by genome-wide association studies.

The cannabinoid antagonist, AM251 attenuates ataxia related deficiencies in a cerebellar ataxic model

Aim: Disruption in cerebellar inputs, as well as dysfunction of Purkinje cells (PCs), causes a change in the timing of electrical signaling in the cerebellum resulting in disorders such as cerebellar ataxia. Although much clinical and molecular genetics research has been conducted to understand this disorder, there is no specific treatment for cerebellar ataxia. As cannabinoid type 1 receptors (CB1Rs) are highly expressed in the cerebellum and have been suggested as a therapeutic strategy, we determined whether AM251, a cannabinoid receptor antagonist, was neuroprotective of PCs in a rat cerebellar ataxic model.Materials and methods: To this end, we conducted behavioral and histological tests in the 3-acetylpyridine (3AP) rat cerebellar ataxia model, to explore whether AM251 was protective against induction of ataxia and cell death.Results: Rats with chemical degeneration of the inferior olive induced by 3AP (55 mg/kg, i.p.) clearly showed cerebellar ataxic symptoms. The locomotor activity and motor coordination of the ataxic animals were clearly disrupted compared to the control group. Further, histological analysis showed cell death and PCs degenerated with loss of cell membrane integrity associated with 3AP. Pre-treatment by AM251 improved the locomotor activity of the ataxic animals, and AM251 almost prevented PCs neuronal degeneration.Conclusion: Our data which show protection of cerebellar PCs and motor improvement in the ataxic rat model by treatment with AM251 suggests that targeting cannabinoid receptors should be considered for therapeutic intervention in cerebellar ataxia.HIGHLIGHTS:AM251 was protective against induction of ataxia and cell death.CBR antagonist typically ameliorated 3AP induced Ataxia.AM251 affected explorative and gait disturbances induced by 3AP.CBR antagonist improved impairments of anxiety-like behaviors following 3AP.

Inhibiting cholinergic signalling in the cerebellar interpositus nucleus impairs motor behaviour

The role of neuromodulators in the cerebellum is not well understood. In particular, the behavioural significance of the cholinergic system in the cerebellum is unknown. To investigate the importance of cerebellar cholinergic signalling in behaviour, we infused acetylcholine receptor antagonists, scopolamine and mecamylamine, bilaterally into the rat cerebellum (centred on interpositus nucleus) and observed the motor effects through a battery of behavioural tests. These tests included unrewarded behaviour during open field exploration and a horizontal ladder walking task and reward-based beam walking and pellet reaching tasks. Infusion of a mix of the antagonists did not impair motor learning in the horizontal ladder walking or the reaching task but reduced spontaneous movement during open field exploration, impaired coordination during beam walking and ladder walking, led to fewer reaches in the pellet reaching task, slowed goal-directed reaching behaviour and reduced reward pellet consumption in a free access to food task. Infusion of the muscarinic antagonist scopolamine on its own resulted in deficits in motor performance and a reduction in the number of reward pellets consumed in the free access to food task. By contrast, infusion of the nicotinic antagonist mecamylamine on its own had no significant effect on any task, except beam walking traversal time, which was reduced. Together, these data suggest that acetylcholine in the cerebellar interpositus nucleus is important for the execution and coordination of voluntary movements mainly via muscarinic receptor signalling, especially in relation to reward-related behaviour.

Digital Measures of Postural Sway Quantify Balance Deficits in Spinocerebellar Ataxia

BACKGROUND

Maintaining balance is crucial for independence and quality of life. Loss of balance is a hallmark of spinocerebellar ataxia (SCA).

OBJECTIVE

The aim of this study was to identify which standing balance conditions and digital measures of body sway were most discriminative, reliable, and valid for quantifying balance in SCA.

METHODS

Fifty-three people with SCA (13 SCA1, 13 SCA2, 14 SCA3, and 13 SCA6) and Scale for Assessment and Rating of Ataxia (SARA) scores 9.28 ± 4.36 and 31 healthy controls were recruited. Subjects stood in six test conditions (natural stance, feet together and tandem, each with eyes open [EO] and eyes closed [EC]) with an inertial sensor on their lower back for 30 seconds (×2). We compared test completion rate, test-retest reliability, and areas under the receiver operating characteristic curve (AUC) for seven digital sway measures. Pearson's correlations related sway with the SARA and the Patient-Reported Outcome Measure of Ataxia (PROM ataxia).

RESULTS

Most individuals with SCA (85%-100%) could stand for 30 seconds with natural stance EO or EC, and with feet together EO. The most discriminative digital sway measures (path length, range, area, and root mean square) from the two most reliable and discriminative conditions (natural stance EC and feet together EO) showed intraclass correlation coefficients from 0.70 to 0.91 and AUCs from 0.83 to 0.93. Correlations of sway with SARA were significant (maximum r = 0.65 and 0.73). Correlations with PROM ataxia were mild to moderate (maximum r = 0.56 and 0.34).

CONCLUSION

Inertial sensor measures of extent of postural sway in conditions of natural stance EC and feet together stance EO were discriminative, reliable, and valid for monitoring SCA. © 2024 International Parkinson and Movement Disorder Society.

The Scale for Assessment and Rating of Ataxia Is Reliable and Valid in the Telehealth Setting for Patients With Cerebellar Ataxia

OBJECTIVE

Health care has increasingly expanded into a hybrid in-person/telehealth model. Patients with a variety of health conditions, including cerebellar ataxia, have received virtual health evaluations; however, it remains unknown whether some outcome measures that clinicians utilize in the telehealth setting are reliable and valid. The goal of this project is to evaluate the psychometric properties of the Scale for Assessment and Rating of Ataxia (SARA) for patients with cerebellar ataxia in the telehealth setting.

METHODS

Nineteen individuals with cerebellar impairments were recruited on a voluntary basis. Participants completed 2 30-minute testing sessions during which a clinical examination and the SARA were performed. One session was performed in person, and the other session was assessed remotely. Outcome measure performance was video recorded in both environments and independently scored by 4 additional raters with varying levels of clinical experience (ranging from 6 months to 29 years). Concurrent validity was assessed with the Spearman rank order correlation coefficient (α < .05), comparing the virtual SARA scores to their gold standard in-person scores. Interrater reliability was evaluated with the intraclass correlation coefficient (ICC) (2,4) (α < .05).

RESULTS

Fourteen of the 19 participants completed both in-person and telehealth SARA evaluations. We found that the in-person SARA and the telehealth SARA have large concurrent validity (Spearman rho significant at the 2-tailed α of .01 = 0.90; n = 14). Additionally, raters of varying years of experience had excellent interrater reliability for both the in-person SARA (ICC [2,4] = 0.97; n = 19) and the telehealth SARA (ICC [2,4] = 0.98; n = 14).

CONCLUSION

Our results show that the telehealth SARA is comparable to the in-person SARA. Additionally, raters of varying years of clinical experience were found to have excellent interrater reliability scores for both remote and in-person SARA evaluations.

IMPACT

Our study shows that the SARA can be used in the telehealth setting for patients with ataxia.

Getting LOST: A conceptual framework for supporting and enhancing spatial navigation in aging

Spatial navigation is more difficult and effortful for older than younger individuals, a shift which occurs for a variety of neurological, physical, and cognitive reasons associated with aging. Despite a large body of evidence documenting age-related deficits in spatial navigation, comparatively less research addresses how to facilitate more effective navigation behavior for older adults. Since navigation challenges arise for a variety of reasons in old age, a one-size-fits-all solution is unlikely to work. Here, we introduce a framework for the variety of spatial navigation challenges faced in aging, which we call LOST-Location, Orientation, Spatial mapping, and Transit. The LOST framework builds on evidence from the cognitive neuroscience of spatial navigation, which reveals distinct components underpinning human wayfinding. We evaluate research on navigational aids-devices and depictions-which help people find their way around; and we reflect on how navigation aids solve (or fail to solve) specific wayfinding difficulties faced by older adults. In summary, we emphasize a bespoke approach to improving spatial navigation in aging, which focuses on tailoring navigation solutions to specific navigation challenges. Our hope is that by providing precise support to older navigators, navigation opportunities can facilitate independence and exploration, while minimizing the danger of becoming lost. We conclude by delineating critical knowledge gaps in how to improve older adults' spatial navigation capacities that the novel LOST framework could guide to address. This article is categorized under: Psychology > Development and Aging Neuroscience > Cognition Neuroscience > Behavior.

Case Series: Vestibular Migraines in Fragile X Premutation Carriers

BACKGROUND

Vestibular migraine (VM) is one of the most common causes of recurrent vertigo and presents with a history of spontaneous or positional vertigo with a history of migraine headaches. While research has identified a high prevalence of migraine headaches and vestibular deficits among fragile X premutation carriers, there has been no discussion about VM within this population.

OBJECTIVE

This case series and review seeks to describe the clinical characteristics and pathophysiology of VM among individuals with the fragile X premutation. We also seek to discuss treatment and future steps in addressing VM in this population.

METHODS

A review of the literature regarding vestibular migraine and presentation of migraine headaches and vestibular deficits among premutation carriers was performed. A detailed clinical history of migraine headaches and vertigo was obtained from three patients with the fragile X premutation seen by the senior author (RJH).

RESULTS

All three cases first developed symptoms of migraine headaches earlier in life, with the development of VM near menopause. Two of the three cases developed progressive balance issues following the development of VM. All three cases found that their VM episodes were improved or resolved with pharmacological and/or lifestyle interventions.

CONCLUSIONS

It is important to recognize VM among premutation carriers because beneficial treatments are available. Future studies are needed regarding the prevalence of VM and the relationship to subsequent FXTAS. The pathophysiology of VM remains uncertain but possibilities include mitochondrial abnormalities, cranial nerve VIII toxicity secondary to neurotoxic protein accumulation, and calcitonin gene-related peptide (CGRP) signaling dysfunction due to altered levels of fragile X messenger ribonucleoprotein (FMRP).

Appropriate Vestibular Stimulation in Children and Adolescents-A Prerequisite for Normal Cognitive, Motor Development and Bodily Homeostasis-A Review

The structural development of the vestibular part of the inner ear is completed by birth but its central connections continue to develop until adolescence. Their development is dependent on vestibular stimulation-vestibular experience. Studies have shown that vestibular function, modulated by experience and epigenetic factors, is not solely an instrument for body position regulation, navigation, and stabilization of the head and images but also influences cognition, emotion, the autonomous nervous system and hormones. To emphasize the importance of appropriate vestibular stimulation, we present a literature review of its effect on bodily homeostasis, cognition and emotion.

Efficacy of transcranial direct current stimulation in patients with knee osteoarthritis: A systematic review

OBJECTIVE

Transcranial direct current stimulation (tDCS) has demonstrated its efficacy in alleviating pain among individuals with musculoskeletal disorders. This review focuses on the application of tDCS as a therapeutic intervention for managing knee osteoarthritis (OA), a prevalent musculoskeletal condition. The primary objective is to assess the effectiveness of tDCS(add-on tDCS and /or stand-alone tDCS), whether as an add-on to existing treatments or as a standalone therapy, in reducing pain and enhancing functional capacity in patients with knee OA.

METHODS

A comprehensive search was conducted across multiple databases, including PubMed, Science Direct, OVID, MEDLINE, CINAHL, EMBASE, ProQuest, and Google Scholar, and Web of Science. The search terms employed were "Transcranial direct current stimulation" or "tDCS" in combination with "Osteoarthritis" or "OA" and "knee." After eliminating duplicates and studies that did not meet the inclusion criteria, a total of 14 relevant articles were identified for review.

RESULTS

Among the included studies, twelve reported statistically significant improvements in pain levels when comparing the active tDCS group to the sham tDCS group. Only two studies reported no significant difference in pain intensity between the active tDCS and sham tDCS groups. Findings regarding functional abilities were diverse, with some studies demonstrating a significant enhancement in functional outcomes in the active tDCS group, while others observed no statistically significant differences.

CONCLUSION

The results of this review suggest that tDCS holds promise as a pain management intervention for individuals with knee OA. Notably, anodal tDCS applied over the primary motor cortex (M1) appears to be particularly effective in alleviating pain in patients with knee OA. However, the impact of tDCS on functional performance appears to be limited.

Motor adaptation and immediate retention to overground gait-slip perturbation training in people with chronic stroke: an experimental trial with a comparison group

Background

Perturbation-based training has shown to be effective in reducing fall-risk in people with chronic stroke (PwCS). However, most evidence comes from treadmill-based stance studies, with a lack of research focusing on training overground perturbed walking and exploring the relative contributions of the paretic and non-paretic limbs. This study thus examined whether PwCS could acquire motor adaptation and demonstrate immediate retention of fall-resisting skills following bilateral overground gait-slip perturbation training.

Methods

65 PwCS were randomly assigned to either (i) a training group, that received blocks of eight non-paretic (NP-S1 to NP-S8) and paretic (P-S1 to P-S8) overground slips during walking followed by a mixed block (seven non-paretic and paretic slips each interspersed with unperturbed walking trials) (NP-S9/P-S9 to NP-S15/P-S15) or (ii) a control group, that received a single non-paretic and paretic slip in random order. The assessor and training personnel were not blinded. Immediate retention was tested for the training group after a 30-minute rest break. Primary outcomes included laboratory-induced slip outcomes (falls and balance loss) and center of mass (CoM) state stability. Secondary outcomes to understand kinematic contributors to stability included recovery strategies, limb kinematics, slipping kinematics, and recovery stride length.

Results

PwCS within the training group showed reduced falls (p < 0.01) and improved post-slip stability (p < 0.01) from the first trial to the last trial of both paretic and non-paretic slip blocks (S1 vs. S8). During the mixed block training, there was no further improvement in stability and slipping kinematics (S9 vs. S15) (p > 0.01). On comparing the first and last training trial (S1 vs. S15), post-slip stability improved on both non-paretic and paretic slips, however, pre-slip stability improved only on the non-paretic slip (p < 0.01). On the retention trials, the training group had fewer falls and greater post-slip stability than the control group on both non-paretic and paretic slips (p < 0.01). Post-slip stability on the paretic slip was lower than that on the non-paretic slip for both groups on retention trials (p < 0.01).

Conclusion

PwCS can reduce laboratory-induced slip falls and backward balance loss outcomes by adapting their post-slip CoM state stability after bilateral overground gait-slip perturbation training. Such reactive adaptations were better acquired and retained post-training in PwCS especially on the non-paretic slips than paretic slips, suggesting a need for higher dosage for paretic slips.

Clinical registry number

NCT03205527.

Increased Cerebellar Gray Matter Volume in Athletes: A Voxel-Wise Coordinate-Based Meta-Analysis

Purpose: The purpose of this systematic review and meta-analysis study was to investigate distinct brain structural characteristics in athletes as compared with those in non-athletes by quantifying regional gray matter (GM) volume changes using voxel-based morphometry analysis based on a whole-brain approach. Methods: The systematic literature search was conducted from November 1, 2020 to October 18, 2021 via the two search engines including the PubMed and Web of Science. We included 13 studies that reported GM volume data in 229 athletes as compared 219 non-athletes based on the whole-brain analysis with specific three-dimensional coordinates in a standard stereotactic space. Thus, we performed a coordinate-based meta-analysis using the seed-based d mapping via permutation of subject images methods. Result: The coordinate-based meta-analysis reported that the athletes significantly reveal greater regional GM volume across right cerebellar lobules IV-V and Brodmann area 37 regions than those in the non-athletes with minimal levels of heterogeneity and publication bias between the included studies. The subgroup analyses show that greater GM volume for athletes in closed-skill sports appeared across the right cerebellar hemispheric lobules VIII and the right cingulum than those for non-athletes. Conclusion: These cumulative findings from multiple brain imaging studies suggest potential brain plasticity evidence in the athletes who experienced extensive motor training.

Review articles (Meta-Analyses) effects of walking on cognitive function in individuals with mild cognitive impairment: a systematic review and meta-analysis

BACKGROUND

Mild cognitive impairment (MCI) is the stage between the expected cognitive decline of normal aging and the more serious decline of dementia. Previous studies have shown that regular exercise can improve cognition and physical performance in older adults. Walking is a low-technology and low-cost exercise that has been proven to improve cognition and mobility in healthy elderly individuals. However, no systematic review or meta-analysis has explored whether walking can improve cognitive function in older adults with MCI. This study aimed to explore the effects of walking interventions on cognitive functions in individuals with MCI.

METHODS

In accordance with the PRISMA guidelines, MEDLINE, PubMed, SPORTDiscus, Cochrane Central Register of Controlled Trials, CINAHL, Web of Science, Airiti Library, and the National Digital Library of Theses and Dissertations in Taiwan were searched from inception to July 2023. Independent reviewers selected randomized clinical trials (RCT) that compared the effects of walking with no intervention or other exercises in individuals with MCI. The primary outcomes were cognitive functions, and the secondary outcome was walking endurance. Three reviewers independently conducted data extraction. The risk of bias was assessed using the Revised Cochrane Risk of Bias assessment tool.

RESULTS

Fourteen RCTs were included in this review. The quality of evidence in these studies was rated as good to excellent. The results of the meta-analysis showed that the individuals with MCI had no significant improvement in cognitive function but had significant improvement in the 6-min walk test (Mean Difference=23.70, p=0.008) after walking interventions compared to no intervention or other exercises.

CONCLUSION

Walking intervention has no significant improvement on cognitive functions in older adults with MCI. However, walking induces beneficial effects on aerobic capacity.

TRIAL REGISTRATION

This systematic review has the registration number CRD42021283753 on PROSPERO.

Susceptibility to walking balance perturbations in young adults is largely unaffected by anticipation

Despite progress in understanding the mechanisms governing walking balance control, the number of falls in our older adult population is projected to increase. Falls prevention systems and strategies may benefit from understanding how anticipation of a balance perturbation affects the planning and execution of biomechanical responses to mitigate instability. However, the extent to which anticipation affects the proactive and reactive adjustments to perturbations has yet to be fully investigated, even in young adults. Our purpose was to investigate the effects of anticipation on susceptibility to two different mechanical balance perturbations - namely, treadmill-induced perturbations and impulsive waist-pull perturbations. Twenty young adults (mean ± standard deviation age: 22.8 ± 3.3 years) walked on a treadmill without perturbations and while responding to treadmill belt (200 ms, 6 m/s2) and waist-pull (100 ms, 6% body weight) perturbations delivered in the anterior and posterior directions. We used 3D motion capture to calculate susceptibility to perturbations during the perturbed and preceding strides via whole-body angular momentum (WBAM) and anterior-posterior margin of stability (MoSAP). Contrary to our hypotheses, anticipation did not affect young adults' susceptibility to walking balance challenges. Conversely, perturbation direction significantly affected walking instability. We also found that susceptibility to different perturbation contexts is dependent on the outcome measure chosen. We suggest that the absence of an effect of anticipation on susceptibility to walking balance perturbations in healthy young adults is a consequence of their having high confidence in their reactive balance integrity. These data provide a pivotal benchmark for the future identification of how anticipation of a balance challenge affects proactive and reactive balance control in populations at risk of falls.

Dystonia and Parkinson's disease: Do they have a shared biology?

Parkinsonism and dystonia co-occur across many movement disorders and are most encountered in the setting of Parkinson's disease. Here we aim to explore the shared neurobiological underpinnings of dystonia and parkinsonism through the clinical lens of the conditions in which these movement disorders can be seen together. Foregrounding the discussion, we briefly review the circuits of the motor system and the neuroanatomical and neurophysiological aspects of motor control and highlight their relevance to the proposed pathophysiology of parkinsonism and dystonia. Insight into shared biology is then sought from dystonia occurring in PD and other forms of parkinsonism including those disorders in which both can be co-expressed simultaneously. We organize these within a biological schema along with important questions to be addressed in this space.

The Effect of Motor Imaginary Combined with Transcranial Direct Current Stimulation (tDCS) on Balance in Middle-Aged Women with High Fall Risk: A Double-Blind Randomized Controlled Trial

Introduction. The risk of falling and its subsequent injuries increases with aging. Impaired balance and gait are important contributing factors to the increased risk of falling. A wide range of methods was examined to improve balance, but these interventions might produce small effects or be inapplicable for this population. The current study aimed at investigating the effect of motor imaginary (MI) training combined with transcranial direct current stimulation (tDCS) over the cerebellum on balance in middle-aged women with high fall risk. Methods. Thirty subjects aged 40-65 years old were divided into two groups including intervention ( $n=15$ ) and sham control ( $n=15$ ). The participants completed a 4-week program 3 times per week. The intervention group performed MI training combined with tDCS over the cerebellum, and the control group performed MI training combined with sham tDCS over the cerebellum. Static and dynamic balance were measured at baseline and after completing the 4-week program using balance error scoring system (BESS) and Y balance testing, respectively. Result. A one-way analysis of covariance and paired $t$ -tests were used to analyze the data. Significant improvement was observed in both balance tests in the intervention group after the implementation of the 4-week intervention program compared to the control group. The within-group analysis showed that both static and dynamic balance improved significantly from the baseline values only in the intervention group ( $p<0.05$ ) and not in the control group ( $p>0.05$ ). Conclusion. The results of the study indicate that MI training combined with tDCS over the cerebellum can lead to balance improvement in middle-aged women with high fall risk.

Flat versus Simulated Mountain Trail Running: A Multidisciplinary Comparison in Well-Trained Runners

This paper compares cardiopulmonary and neuromuscular parameters across three running aerobic speeds in two conditions that differed from a treadmill's movement: flat condition (FC) and unpredictable roll variations similar to mountain trail running (URV). Twenty well-trained male runners (age 33 ± 8 years, body mass 70.3 ± 6.4 kg, height 1.77 ± 0.06 m, V˙O₂max 63.8 ± 7.2 mL·kg^-1·min^-1) voluntarily participated in the study. Laboratory sessions consisted of a cardiopulmonary incremental ramp test (IRT) and two experimental protocols. Cardiopulmonary parameters, plasma lactate (BLa^-), cadence, ground contact time (GT) and RPE values were assessed. We also recorded surface electromyographic (sEMG) signals from eight lower limb muscles, and we calculated, from the sEMG envelope, the amplitude and width of peak muscle activation for each step. Cardiopulmonary parameters were not significantly different between conditions (V˙O₂: p = 0.104; BLa^-: p = 0.214; HR: p = 0.788). The amplitude (p = 0.271) and width (p = 0.057) of sEMG activation peaks did not change between conditions. The variability of sEMG was significantly affected by conditions; indeed, the coefficient of variation in peak amplitude (p = 0.003) and peak width (p < 0.001) was higher in URV than in FC. Since the specific physical demands of running can differ between surfaces, coaches should resort to the use of non-traditional surfaces, emphasizing specific surface-related motor tasks that are normally observed in natural running environments. Seeing that the variability of muscle activations was affected, further studies are required to better understand the physiological effects induced by systematic surface-specific training and to define how variable-surface activities help injury prevention.

Pharmacologic antagonism of CB1 receptors improves electrophysiological alterations in Purkinje cells exposed to 3-AP

INTRODUCTION

Although ataxia is associated with cerebellar dysfunction, little is known about the effects of 3-AP exposure on Purkinje cell electrophysiological properties. Here, we evaluated these parameters in cerebellar vermis brain slices.

METHODS

Purkinje cells were exposed to artificial cerebrospinal fluid (aCSF) (control) or to 1 mM 3-acetylpyridine (3-AP) in the recording chamber. The effects of a cannabinoid agonist (WIN; 7.5 nmol) and a cannabinoid antagonist (AM; 20 nmol) were evaluated under both conditions.

RESULTS

Exposure to 3-AP induced dramatic changes in cellular excitability that likely would affect Purkinje cell output. In whole-cell current clamp recordings, 3-AP-exposed Purkinje cells demonstrated a significantly higher frequency of action potentials, a larger afterhyperpolarization (AHP), and a larger rebound of action potentials. In addition, 3-AP caused a significant decrease in the interspike interval (ISI), half-width, and first spike latency. Remarkably, the action potential frequency, AHP amplitude, rebound, ISI, action potential halfwidth, and first spike latency were no longer different from controls in 3-AP cells treated with AM. Sag percentage, on the other hand, showed no significant difference under any treatment condition, indicating that cannabinoids' actions on 3-AP-mediated Purkinje cell changes may not include effects on neuronal excitability through changes of Ih.

CONCLUSIONS

These data show that cannabinoid antagonists reduce the excitability of Purkinje cells following exposure to 3-AP and suggest their potential as therapeutics in cerebellar dysfunctions.

Fighting secondary triple-negative breast cancer in cerebellum: A powerful aid from a medicinal mushrooms blend

Breast cancer (BC) is the second most common cause of brain metastasis onset in patients, with the cerebellum accounting for the 33% of cases. In the current study, using a 4T1 triple-negative mouse BC model, we revealed that an orally administered medicinal mushrooms (MM) blend, rich in β-glucans, played a direct and specific anti-cancer action on cerebellar metastases, also bettering locomotor performances. The neuroprotective effect of the MM blend plays through (i) a direct and specific inhibition of cerebellar metastatization pattern typical of TNBC (with an induced reduction of about 50% of metastases density) and (ii) the regulation of apoptosis and proliferation-related genes, as suggested by expression changes of specific molecular markers, i.e. PCNA, p53, Bcl2, BAX, CASP9, CASP3, Hsp70 and AIF. Therefore, inhibiting the metastatization process, triggering a significant apoptosis increase, and lessening cell proliferation, this MM supplement, employed as adjuvant treatment in association with conventional therapy, could represent a promising approach, in the field of Integrative Oncology, for patients' management in both prevention and treatment of brain metastases from BC.

Effect of disturbance stimulation using a split-belt treadmill on a patient with cerebellar ataxia: a case report

PURPOSE

We present the case of a patient with cerebellar ataxia who was treated with walking practice using a split-belt treadmill with disturbance stimulation. The treatment effects were evaluated for improvements in standing postural balance and walking ability.

CASE PRESENTATION

The patient was a 60-year-old Japanese male who developed ataxia after cerebellar hemorrhage. Assessment was performed using the Scale for the Assessment and Rating of Ataxia, Berg Balance Scale, and Timed Up-and-Go tests. A 10 m walking speed and walking rate were also assessed longitudinally. The obtained values were fit into a linear equation (y = ax + b), and the slope was calculated. This slope was then used as the predicted value for each period relative to the pre-intervention value. After removing the trend of the value for each period relative to the pre-intervention value, the amount of pre- to post-intervention change for each period was calculated to verify the intervention effect. Furthermore, to verify the changes in gait over time, a three-dimensional motion analyzer was used to analyze the pre- and post-intervention gait five times, and the results were kinematically compared.

RESULTS

No significant pre- to post-intervention changes were observed in the Scale for the Assessment and Rating of Ataxia scores. Conversely, the Berg Balance Scale score, walking rate, and 10 m walking speed increased, and the Timed Up-and-Go score decreased in the B1 period, indicating a marked improvement from the predicted results based on the linear equation. For changes in gait determined using three-dimensional motion analysis, an increase in stride length was observed in each period.

CONCLUSION

The present case findings suggest that walking practice with disturbance stimulation using a split-belt treadmill does not improve inter-limb coordination, but contributes to improving standing posture balance, 10 m walking speed, and walking rate.

The cerebellum and anxiety

Although the cerebellum is traditionally known for its role in motor functions, recent evidence points toward the additional involvement of the cerebellum in an array of non-motor functions. One such non-motor function is anxiety behavior: a series of recent studies now implicate the cerebellum in anxiety. Here, we review evidence regarding the possible role of the cerebellum in anxiety-ranging from clinical studies to experimental manipulation of neural activity-that collectively points toward a role for the cerebellum, and possibly a specific topographical locus within the cerebellum, as one of the orchestrators of anxiety responses.

Case report: Backward gait training combined with gait-synchronized cerebellar transcranial alternating current stimulation in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is characterized by recurrent falls caused by postural instability, and a backward gait is considered beneficial for postural instability. Furthermore, a recent approach for rehabilitation combined with gait-oriented synchronized stimulation using non-invasive transcranial patterned stimulation could be promising for balance function. Here, we present a case of PSP with backward gait training combined with gait-synchronized transcranial alternating current stimulation (tACS). A 70-year-old woman with PSP-Richardson's syndrome underwent backward gait training combined with synchronized cerebellar tACS. Initially, she underwent short-term intervention with combined training of backward gait with synchronized cerebellar tACS, asynchronized, or sham stimulation according to the N-of-1 study design. Synchronized tACS training demonstrated a decrease in postural instability, whereas asynchronized or sham stimulation did not. The additional long-term interventions of combined backward gait training with synchronized cerebellar tACS demonstrated further decrease in postural instability with improvements in gait speed, balance function, and fall-related self-efficacy in daily life. The present case describes a novel approach for motor symptoms in a patient with PSP. Backward gait training with synchronized cerebellar tACS may be a promising therapeutic approach.

Swing-phase pelvis perturbation improves dynamic lateral balance during walking in individuals with spinal cord injury

The purpose of this study was to determine whether the control of lateral balance can be improved by applying repeated lateral perturbation force to the pelvis during swing versus stance phase walking in individuals with spinal cord injury (SCI). Fourteen individuals with incomplete SCI were recruited in this study. Each participant visited the lab once and was tested in two experimental sessions that consisted of (1) treadmill walking with bilateral perturbation force applied to the pelvis in the lateral direction during either swing or stance phase of each leg and (2) overground walking pre- and post-treadmill walking. Applying the swing-phase perturbation during walking induced a greater increase in the muscle activation of hip abductors and ankle plantar flexors and a greater improvement in lateral balance control after the removal of perturbation force, in comparison to the results of the stance-phase perturbation condition (P ≤ 0.03). Participants also exhibited a greater reduction in overground step width and a greater improvement in overground walking speed after a session of treadmill walking practice with the swing-phase perturbation, compared with the result of the stance-phase perturbation (P = 0.01). These findings suggest that applying perturbation force to the pelvis during the swing phase of gait while walking may enhance muscle activities of hip abductors and improve lateral balance control in individuals with SCI. A walking practice with the swing-phase pelvis perturbation can be used as a rehabilitation approach to improve the control of lateral balance during walking in people with SCI.

Interactions across emotional, cognitive and subcortical motor networks underlying freezing of gait

Freezing of gait (FOG) is a gait disorder affecting patients with Parkinson's disease (PD) and related disorders. The pathophysiology of FOG is unclear because of its phenomenological complexity involving motor, cognitive, and emotional aspects of behavior. Here we used resting-state functional MRI to retrieve functional connectivity (FC) correlated with the New FOG questionnaire (NFOGQ) reflecting severity of FOG in 67 patients with PD. NFOGQ scores were correlated with FCs in the extended basal ganglia network (BGN) involving the striatum and amygdala, and in the extra-cerebellum network (CBLN) involving the frontoparietal network (FPN). These FCs represented interactions across the emotional (amygdala), subcortical motor (BGN and CBLN), and cognitive networks (FPN). Using these FCs as features, we constructed statistical models that explained 40% of the inter-individual variances of FOG severity and that discriminated between PD patients with and without FOG. The amygdala, which connects to the subcortical motor (BGN and CBLN) and cognitive (FPN) networks, may have a pivotal role in interactions across the emotional, cognitive, and subcortical motor networks. Future refinement of the machine learning-based classifier using FCs may clarify the complex pathophysiology of FOG further and help diagnose and evaluate FOG in clinical settings.

Short term effects of anodal cerebellar vs. anodal cerebral transcranial direct current stimulation in stroke patients, a randomized control trial

Background

Balance and gait impairments are major motor deficits in stroke patients that require intensive neuro-rehabilitation. Anodal transcranial direct current stimulation is a neuro-modulatory technique recently used in stroke patients for balance and gait improvement. Majority of studies focusing on tDCS have assessed its effects on cerebral motor cortex and more recently cerebellum as well but to our best knowledge the comparison of stimulating these two regions in stroke patients is not investigated so far.

Objective

The current study aimed to compare the effect of anodal transcranial direct current stimulation on cerebellar and cerebral motor cortex M1 in stroke patients.

Materials and methods

This double-blinded, parallel, randomized, sham controlled trial included 66 patients with a first-ever ischemic stroke were recruited into three groups; Cerebellar stimulation group (CbSG), M1 Stimulation Group (MSG), and Sham stimulation group (SSG). A total of three sessions of anodal transcranial direct current stimulation were given on consecutive days in addition to non-immersive virtual reality using Xbox 360 with kinect. Anodal tDCS with an intensity of 2 mA was applied for a duration of 20 min. Primary outcome measures berg balance scale (BBS), timed up and go test (TUG), BESTest Balance Evaluation-Systems Test (BESTest) and secondary outcomes measures montreal cognitive assessment (MoCA), mini mental state examination (MMSE), Johns Hopkins Fall Risk Assessment Tool (JHFRAT), twenty five feet walk test (25FWT), six minute walk test (6MWT), and tDCS Adverse Effects was assessed before initiation of treatment (T0) and at the end of third session of stimulation (T1).

Results

The results of between group's analysis using mean difference showed a significant difference with p-value <0.05 for balance (BBS, TUG, BESTest), walking ability (6MWT, 25FWT), risk of fall (JHFRAT). Cognitive function did not show any significant change among the groups for MoCA with p-value >0.05 but MMSE was improved having significant p-value (p = 0.013). However, 6MWT and 25FWT showed non-significant results for both between group and within group analysis. In pairwise comparison both the cerebellar and cerebral stimulation groups showed Significant difference with p-value <0.05 in comparison to sham stimulation; BBS (cerebellar vs. sham p ≤ 0.001, cerebral vs. sham p = 0.011), TUG (cerebellar vs. sham p = 0.001, cerebral vs. sham p = 0.041), Bestest (cerebellar vs. sham p = 0.007, cerebral vs. sham p = 0.003). Whereas for JHFRAT only cerebellar stimulation in comparison to sham and motor cortex stimulation showed significant improvements (cerebellar vs. M1 p = 0.037, cerebellar vs. sham p = 0.037). MMSE showed significant improvement in M1 stimulation (M1 vs. cerebellar p = 0.036, M1 vs. sham p = 0.011).

Conclusion

Findings of the study suggest anodal tDCS stimulation of the cerebellum and cerebral motor cortex both improves gait, balance and risk of fall in stroke patients. However, both stimulation sites do not induce any notable improvement in cognitive function. Effects of both stimulation sites have similar effects on mobility in stroke patients.

Deconstruction of Vermal Cerebellum in Ramp Locomotion in Mice

The cerebellum is involved in encoding balance, posture, speed, and gravity during locomotion. However, most studies are carried out on flat surfaces, and little is known about cerebellar activity during free ambulation on slopes. Here, it has been imaged the neuronal activity of cerebellar molecular interneurons (MLIs) and Purkinje cells (PCs) using a miniaturized microscope while a mouse is walking on a slope. It has been found that the neuronal activity of vermal MLIs specifically enhanced during uphill and downhill locomotion. In addition, a subset of MLIs is activated during entire uphill or downhill positions on the slope and is modulated by the slope inclines. In contrast, PCs showed counter-balanced neuronal activity to MLIs, which reduced activity at the ramp peak. So, PCs may represent the ramp environment at the population level. In addition, chemogenetic inactivation of lobule V of the vermis impaired uphill locomotion. These results revealed a novel micro-circuit in the vermal cerebellum that regulates ambulatory behavior in 3D terrains.

Development of Cerebellar Reserve

The cerebellar reserve is defined as the capacity of the cerebellum for compensation and restoration following injury. This unique cerebellar ability is attributed to various forms of synaptic plasticity that incorporate multimodal and redundant cerebellar inputs, two major features of the cerebellar circuitry. It is assumed that the cerebellar reserve is acquired from the age of 12 years after the maturation of both the cerebellar adaptative behaviors and cerebellar functional connectivity. However, acquiring the cerebellar reserve is also affected by two other factors: vulnerability and growth potential in the developing cerebellum. First, cerebellar injury during the critical period of neural circuit formation (especially during fetal and neonatal life and infancy) leads to persistent dysfunction of the cerebellum and its targets, resulting in the limitation of the cerebellar reserve. Secondly, growth potential appears to facilitate cerebellar reserve during the stage when the cerebellar reserve is still immature. Based on these findings, the present mini-review proposes a possible developmental trajectory underlying the acquisition of cerebellar reserve. We highlight the importance of studies dedicated to the understanding of the cerebellar resilience to injuries.

The association of reproductive stage with lobular cerebellar network connectivity across female adulthood

Sex-specific differences in the aging cerebellum may be related to hormone changes with menopause. We evaluated the association between reproductive stage and lobular cerebellar network connectivity using data from the Cambridge Centre for Ageing and Neuroscience repository. We used raw structural and resting state neuroimaging data and information regarding age, sex, and menopause-related variables. Crus I and II and Lobules V and VI were our cerebellar seeds of interest. We characterized reproductive stage using the Stages of Reproductive Aging Workshop criteria. Results show that postmenopausal females have lower cerebello-striatal and cerebello-cortical connectivity, particularly in frontal regions, along with lower connectivity within the cerebellum, compared to reproductive females. Postmenopausal females also exhibit greater connectivity in some brain areas as well. Differences begin to emerge across transitional stages of menopause. Further, results reveal sex-specific differences in connectivity between female reproductive groups and age-matched male control groups. This suggests that menopause may be associated with cerebellar network connectivity in aging females, and sex differences in the aging brain may be related to this biological process.

Somatosensory impairment of the feet is associated with higher activation of prefrontal cortex during walking in older adults

BACKGROUND

Over-activation of prefrontal cortex during walking has been reported in older adults versus young adults. Heighted activity in prefrontal cortex suggests a shift toward an executive control strategy to control walking. A potential contributing factor is degraded functioning of pattern-generating locomotor circuits in the central nervous system that are important to walking coordination. Somatosensory information is a crucial input to these circuits, so age-related impairment of somatosensation would be expected to compromise the neural control of walking. The present study tested the hypothesis that poorer somatosensation in the feet of older adults will be associated with greater recruitment of the prefrontal cortex during walking. This study also examines the extent to which somatosensory function and prefrontal activity are associated with performance on walking and balance assessments.

METHODS

Forty seven older adults (age 74.6 ± 6.8 years; 32 female) participated in walking assessments (typical walking and obstacle negotiation) and Berg Balance Test. During walking, prefrontal activity was measured with functional near infrared spectroscopy (fNIRS). Participants also underwent somatosensory testing with Semmes-Weinstein monofilaments.

RESULTS

The primary findings is that worse somatosensory monofilament level was associated with greater prefrontal cortical activity during typical walking (r = 0.38, p = 0.008) and obstacle negotiation (r = 0.40, p = 0.006). For the obstacle negotiation task, greater prefrontal activity was associated with faster walking speed (p = 0.004). Poorer somatosensation was associated with slower typical walking speed (p = 0.07) and obstacles walking speed (p < 0.001), as well as poorer balance scores (p = 0.03).

CONCLUSIONS

The study findings are consistent with a compensation strategy of recruiting prefrontal/executive control resources to overcome loss of somatosensory input to the central nervous system. Future research should further establish the mechanisms by which somatosensory impairments are linked to the neural control and performance of walking tasks, as well as develop intervention approaches.

Purkinje Cell Activity Resonation Generates Rhythmic Behaviors at the Preferred Frequency of 8 Hz

Neural activity exhibits oscillations, bursts, and resonance, enhancing responsiveness at preferential frequencies. For example, theta-frequency bursting and resonance in granule cells facilitate synaptic transmission and plasticity mechanisms at the input stage of the cerebellar cortex. However, whether theta-frequency bursting of Purkinje cells is involved in generating rhythmic behavior has remained neglected. We recorded and optogenetically modulated the simple and complex spike activity of Purkinje cells while monitoring whisker movements with a high-speed camera of awake, head-fixed mice. During spontaneous whisking, both simple spike activity and whisker movement exhibit peaks within the theta band. Eliciting either simple or complex spikes at frequencies ranging from 0.5 to 28 Hz, we found that 8 Hz is the preferred frequency around which the largest movement is induced. Interestingly, oscillatory whisker movements at 8 Hz were also generated when simple spike bursting was induced at 2 and 4 Hz, but never via climbing fiber stimulation. These results indicate that 8 Hz is the resonant frequency at which the cerebellar-whisker circuitry produces rhythmic whisking.

The Predictive Values of Changes in Local and Remote Brain Functional Connectivity in Primary Angle-Closure Glaucoma Patients According to Support Vector Machine Analysis

Purpose

The primary angle-closure glaucoma (PACG) is an irreversible blinding eye disease in the world. Previous neuroimaging studies demonstrated that PACG patients were associated with cerebral changes. However, the effect of optic atrophy on local and remote brain functional connectivity in PACG patients remains unknown.

Materials and Methods

In total, 23 patients with PACG and 23 well-matched Health Controls (HCs) were enrolled in our study and underwent resting-state functional magnetic resonance imaging (rs-fMRI) scanning. The regional homogeneity (ReHo) method and functional connectivity (FC) method were used to evaluate the local and remote brain functional connectivity. Moreover, support vector machine (SVM) method was applied to constructing PACG classification model.

Results

Compared with the HC, PACG patients showed increased ReHo values in right cerebellum (CER)_8, left CER_4-5, and right CER_8. In contrast, PACG patients showed decreased ReHo values in the bilateral lingual gyrus (LING)/calcarine (CAL)/superior occipital gyrus (SOG) and right postcentral gyrus (PostCG). The ReHo value exhibited an accuracy of 91.30% and area under curve (AUC) of 0.95 for distinguishing the PACG patients from HC.

Conclusion

Our study demonstrated that the PACG patients showed abnormal ReHo value in the cerebellum, visual cortex, and supplementary motor area, which might be reflect the neurological mechanisms underlying vision loss and eye pain in PACG patients. Moreover, the ReHo values can be used as a useful biomarker for distinguishing the PACG patients from HCs.

Troubleshooting Gait Disturbances in Parkinson's Disease With Deep Brain Stimulation

Deep brain stimulation (DBS) of the subthalamic nucleus or the globus pallidus is an established treatment for Parkinson's disease (PD) that yields a marked and lasting improvement of motor symptoms. Yet, DBS benefit on gait disturbances in PD is still debated and can be a source of dissatisfaction and poor quality of life. Gait disturbances in PD encompass a variety of clinical manifestations and rely on different pathophysiological bases. While gait disturbances arising years after DBS surgery can be related to disease progression, early impairment of gait may be secondary to treatable causes and benefits from DBS reprogramming. In this review, we tackle the issue of gait disturbances in PD patients with DBS by discussing their neurophysiological basis, providing a detailed clinical characterization, and proposing a pragmatic programming approach to support their management.

Validity of balance measures in cerebellar ataxia: A prospective study with 12-month follow-up

INTRODUCTION

Balance deficits are common in cerebellar ataxia. Determining which balance outcome measures are psychometrically strong for this population remains an unmet need.

OBJECTIVE

Evaluate the validity and responsiveness of two clinic-based balance measures [Berg Balance Scale (BBS) and balance sub-component of the Scale for the Assessment and Rating of Ataxia (SARA-bal)] and two laboratory-based balance measures [Sensory Organization Test (SOT) and Limits of Stability (LOS)] in cerebellar ataxia.

DESIGN

Prospective cohort study.

SETTING

Institutional study assessing 40 participants with cerebellar ataxia at baseline, 6, and 12 months.

MAIN OUTCOME MEASURES

Balance was assessed using the BBS, SARA-bal, SOT, and LOS; disease severity was assessed using the SARA; and Patients' Global Impression of Change (PGIC) was used to estimate responsiveness to disease progress at 6 and 12 months.

RESULTS

BBS and SARA-bal (Spearman's correlation coefficient, ρS = -0.89, p < 0.01) demonstrated strong criterion validity. Convergent validity was moderate to high (ρS range:-0.75 to 0.92) and external validity was low (ρS range:-0.75 to 0.11). Composite SOT scores (SOT-COM; ρS=0.29, p<0.01) and maximal excursion (MXE-LOS) in the forward (F) and right (R) directions of the LOS (ρS = 0.18, p < 0.01) demonstrated moderate to low criterion and convergent validity. The area under the receiver operating characteristic curve (AUC_ROC ) and its effect size (standard response mean [SRM]) for categorizing 'stable' and 'worsened' patients at 6 and 12 months were satisfactory for the BBS (AUC_ROC :0.75; SRM-Stable:1.06; SRM-Worsened:1.16), SARA-bal (AUC_ROC :0.76; SRM-Stable:0.86; SRM-Worsened:0.85), and MXE-LOS(R) (AUC_ROC :0.29; SRM-Stable:0.41; SRM-Worsened:1.39).

CONCLUSION

BBS and SARA-bal have moderate to strong criterion and convergent validity and adequate responsiveness to balance changes. Both laboratory-based measures (SOT and LOS) demonstrated a high floor effect. The SOT-COM and MXE-LOS(R) demonstrated moderate to low criterion validity, with only the MXE-LOS(R) displaying adequate responsiveness to balance changes after 6 and 12 months. This article is protected by copyright. All rights reserved.

Consensus Paper: Ataxic Gait

The aim of this consensus paper is to discuss the roles of the cerebellum in human gait, as well as its assessment and therapy. Cerebellar vermis is critical for postural control. The cerebellum ensures the mapping of sensory information into temporally relevant motor commands. Mental imagery of gait involves intrinsically connected fronto-parietal networks comprising the cerebellum. Muscular activities in cerebellar patients show impaired timing of discharges, affecting the patterning of the synergies subserving locomotion. Ataxia of stance/gait is amongst the first cerebellar deficits in cerebellar disorders such as degenerative ataxias and is a disabling symptom with a high risk of falls. Prolonged discharges and increased muscle coactivation may be related to compensatory mechanisms and enhanced body sway, respectively. Essential tremor is frequently associated with mild gait ataxia. There is growing evidence for an important role of the cerebellar cortex in the pathogenesis of essential tremor. In multiple sclerosis, balance and gait are affected due to cerebellar and spinal cord involvement, as a result of disseminated demyelination and neurodegeneration impairing proprioception. In orthostatic tremor, patients often show mild-to-moderate limb and gait ataxia. The tremor generator is likely located in the posterior fossa. Tandem gait is impaired in the early stages of cerebellar disorders and may be particularly useful in the evaluation of pre-ataxic stages of progressive ataxias. Impaired inter-joint coordination and enhanced variability of gait temporal and kinetic parameters can be grasped by wearable devices such as accelerometers. Kinect is a promising low cost technology to obtain reliable measurements and remote assessments of gait. Deep learning methods are being developed in order to help clinicians in the diagnosis and decision-making process. Locomotor adaptation is impaired in cerebellar patients. Coordinative training aims to improve the coordinative strategy and foot placements across strides, cerebellar patients benefiting from intense rehabilitation therapies. Robotic training is a promising approach to complement conventional rehabilitation and neuromodulation of the cerebellum. Wearable dynamic orthoses represent a potential aid to assist gait. The panel of experts agree that the understanding of the cerebellar contribution to gait control will lead to a better management of cerebellar ataxias in general and will likely contribute to use gait parameters as robust biomarkers of future clinical trials.

Functional Outcomes Associated With Independence in Walking Among People With Hereditary Ataxias: An Exploratory Cross-sectional Study

OBJECTIVE

This study aimed to identify functional outcomes related to independence in walking among people affected by hereditary ataxias.

METHODS

Sixty participants were selected by convenience in a list provided by an organization of people with ataxia. Sociodemographic and clinical data were collected using a semistructured questionnaire. The Assessment and Rating of Ataxia was used to assess and rate cerebellar ataxia. Changes in body structure and function, limitation in activities, and restriction in participation were evaluated with specific outcome measures. Participants were classified as independent in walking if they were able to walk without walking aids or human assistance and as dependent in walking if they have been using walking aids (sticks, crutches, or walkers) for more than 6 months, using a wheelchair for locomotion most of the day, or both. Multivariate logistic regression analyses were conducted hierarchically and in blocks considering upper limbs function, balance systems, sensory functions, postural control, walking, independence, cognition, and perception as independent variables. The prevalence ratio for walking independence was determined.

RESULTS

The final regression model pointed out that gait capacity assessed by the 6-Minute Walk Test and dexterity assessed by the Box and Blocks test were the main markers related to walking independence in individuals with hereditary ataxias.

CONCLUSION

The distance covered in 6 minutes of walking (walking endurance) and upper extremity dexterity can be used to better assess the progression of cerebellar disease related to walking independence in individuals with hereditary ataxias.

IMPACT

This study supports early detection of individuals who are at risk of loss of walking independence and an optimized rehabilitation plan.

Wearable sensors detect impaired gait and coordination in LBSL during remote assessments

Background

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a rare leukodystrophy with motor impairment due to biallelic mutations in DARS2, which encodes mitochondrial aspartyl tRNA synthetase. Progressive ataxia is the primary feature.

Objective

The study objective is to determine the feasibility of remotely collecting quantitative gait and balance measures in LBSL.

Methods

The study design uses wearable accelerometers and the scale for the assessment and rating of ataxia (SARA) scale to assess gait and postural sway in LBSL and control participants' homes through video conferencing.

Results

Lateral step variability (LSV), which indicates stride variability, and elevation of the step at mid‐swing are increased for LBSL patients during brief walking tests. During stance with the eyes closed, LBSL participants show rapid accelerations and decelerations of body movement covering a large sway area and path. Both the LSV and sway area during stance with the feet together and eyes closed correlate strongly with the SARA.

Conclusions

Wearable accelerometers are valid and sensitive for detecting ataxia in LBSL patients during remote assessments. The finding of large increases in the sway area during stance with the eyes closed is intriguing since dorsal column dysfunction is universally seen in LBSL. This approach can be applied to related rare diseases that feature ataxia.

Why Should Constant Stimulation of Saccular Afferents Modify the Posture and Gait of Patients with Bilateral Vestibular Dysfunction? The Saccular Substitution Hypothesis

An ongoing EU Horizon 2020 Project called BionicVEST is investigating the effect of constant electrical stimulation (ES) of the inferior vestibular nerve in patients with bilateral vestibular dysfunction (BVD). The evidence is that constant ES results in improved postural stability and gait performance, and so the question of central importance concerns how constant ES of mainly saccular afferents in these BVD patients could cause this improved performance. We suggest that the constant ES substitutes for the absent saccular neural input to the vestibular nuclei and the cerebellum in these BVD patients and indirectly via these structures to other structures, which have been of great recent interest in motor control. One target area, the anterior midline cerebellum (the uvula), has recently been targeted as a location for deep-brain stimulation in human patients to improve postural stability and gait. There are projections from midline cerebellum to basal ganglia, including the striatum, which are structures involved in the initiation of gait. It may be that the effect of this activation of peripheral saccular afferent neurons is analogous to the effect of deep-brain stimulation (DBS) by electrodes in basal ganglia acting to help alleviate the symptoms of patients with Parkinson’s disease.

Cerebro-Cerebellar Response to Sequence Violation in a Cognitive Task: an fMRI Study

The phonological loop is part of Baddeley's verbal working memory (VWM) model that stores phonological information and refreshes its contents through an articulatory process. Many studies have reported the cerebellum's involvement during VWM tasks. In the motor literature, the cerebellum is thought to support smooth and rapid movement sequences through internal models that simulate the action of motor commands, then use the error signals generating from the discrepancy between the predicted and actual sensory consequences to adjust the motor system. Here, we hypothesize that a similar monitoring and error-driven adjustment process can be extended to VWM; specifically, the cerebellum checks for discrepancies between the predicted and actual articulatory process to ensure the accuracy and fluency of articulatory rehearsal. During neuroimaging, participants rehearsed a sequence of letters in sync with the presentation of a visual pacing stimulus (#) that was terminated by the occurrence of a probe letter. Participants judged whether the probe was the correct letter in the sequence (i.e., match trial), or deviated from the sequence (i.e., mismatch trial). Detection of sequence violation was not only associated with prolonged reaction time but also an increased activation in a left executive control network. Psychophysiological interaction was used to investigate whether the cerebellum interacts with the cerebral cortex for error monitoring and adjustments. We found increased functional connectivity between the right cerebellum and the cerebral cortex during mismatch relative to match probes, indicating sequence violation resulting in greater cerebellar connectivity with areas in the cerebral cortex involved in phonological sequencing.

The protective role of exercise against age-related neurodegeneration

Endurance exercise is a widely accessible, low-cost intervention with a variety of benefits to multiple organ systems. Exercise improves multiple indices of physical performance and stimulates pronounced health benefits reducing a range of pathologies including metabolic, cardiovascular, and neurodegenerative disorders. Endurance exercise delays brain aging, preserves memory and cognition, and improves symptoms of neurodegenerative pathologies like Amyotrophic Lateral Sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, and various ataxias. Potential mechanisms underlying the beneficial effects of exercise include neuronal survival and plasticity, neurogenesis, epigenetic modifications, angiogenesis, autophagy, and the synthesis and release of neurotrophins and cytokines. In this review, we discuss shared benefits and molecular pathways driving the protective effects of endurance exercise on various neurodegenerative diseases in animal models and in humans.