Parent-reported problems in children with Cerebral Visual Impairment: Improving the discriminative ability from ADHD and dyslexia using screening inventories.

Daily problems of children with Cerebral Visual Impairment (CVI) are often misinterpreted as symptoms of behavioural disorders or learning disabilities instead of higher order visual function (HOVF) deficits. It is difficult to differentiate between various paediatric clinical groups based on daily manifestations. We used two CVI inventories (V-CVI-I, HVFQI) and an ADHD questionnaire (AVL) to compare parent-reported visual and behavioural problems of children with CVI, ADHD, dyslexia and neurotypical children (Age 6-15, Verbal Intelligence > 70). Our results show a higher percentage of parent-reported visual problems in children with CVI compared to all other groups, which was not affected by their visual acuity levels. On most HOVF categories, a higher percentage of parent-reported visual problems was also found in children with ADHD or dyslexia compared to neurotypical children. Children with ADHD had significantly more parent-reported behavioural problems, but more behavioural problems were reported by the parents of children with CVI compared to neurotypical children as well. Our findings complicate using the existing inventories for initial screening and referral of children with potential CVI. We propose a shortened screening list to improve the potential differentiation between CVI and ADHD or dyslexia based on parent-reported visual problems in everyday life.

Eye tracking: empirical foundations for a minimal reporting guideline.

In this paper, we present a review of how the various aspects of any study using an eye tracker (such as the instrument, methodology, environment, participant, etc.) affect the quality of the recorded eye-tracking data and the obtained eye-movement and gaze measures. We take this review to represent the empirical foundation for reporting guidelines of any study involving an eye tracker. We compare this empirical foundation to five existing reporting guidelines and to a database of 207 published eye-tracking studies. We find that reporting guidelines vary substantially and do not match with actual reporting practices. We end by deriving a minimal, flexible reporting guideline based on empirical research (Section "An empirically based minimal reporting guideline").

Environmental Enrichment Improves Vestibular Oculomotor Learning in Mice.

We assessed the behavioral effects of environmental enrichment on contrast sensitivity, reflexive eye movements and on oculomotor learning in mice that were housed in an enriched environment for a period of 3 weeks. Research has shown that a larger cage and a more complex environment have positive effects on the welfare of laboratory mice and other animals held in captivity. It has also been shown that environmental enrichment affects various behavior and neuroanatomical and molecular characteristics. We found a clear effect on oculomotor learning. Animals that were housed in an enriched environment learned significantly faster than controls that were housed under standard conditions. In line with existing literature, the enriched group also outperformed the controls in behavioral tests for explorative behavior. Meanwhile, both visual and reflexive oculomotor performance in response to visual and vestibular stimuli was unaffected. This points toward an underlying mechanism that is specific for motor learning, rather than overall motor performance.

Developmental changes in visual search are determined by changing visuospatial abilities and task repetition: A longitudinal study in adolescents.

Using a longitudinal study design, a group of 94 adolescents participated in a visual search task and a visuospatial ability task yearly for four consecutive years. We analyzed the association between changes in visuospatial ability and changes in visual search performance and behavior and estimated additional effects of age and task repetition. Visuospatial ability was measured with the Design Organization Test (DOT). Search performance was analyzed in terms of reaction time and response accuracy. Search behavior was analyzed in terms of the number of fixations per trial, the saccade amplitude, and the distribution of fixations over different types of elements. We found that both the increase in age and the yearly repetition of the DOT had a positive effect on visuospatial ability. We show that the acceleration of visual search during childhood can be explained by the increase in visuospatial abilities with age during adolescence. With the yearly task repetition, visual search became faster and more accurate, while fewer fixations were made with larger saccade amplitudes. The combination of increasing visuospatial ability and task repetition makes visual search more effective and might increase the performance of many daily tasks during adolescence.

Trajectories of Cognitive and Motor Function Between Ages 45 and 90 Years: A Population-Based Study.

BACKGROUND: To establish trajectories of cognitive and motor function, and to determine the sequence of change across individual tests in community-dwelling individuals aged 45-90 years. METHOD: Between 1997 and 2016, we repeatedly assessed cognitive function with 5 tests in 9514 participants aged 45-90 years from the population-based Rotterdam Study. Between 1999 and 2016, we measured motor function with 3 tests in 8297 participants. All participants were free from dementia, stroke, and parkinsonism. We assessed overall and education-specific cognitive and motor trajectories using linear mixed models with age as time scale. Next, we determined the sequence of change across individual tests. RESULTS: The number of assessments per participant ranged between 1 and 6 (mean interval, years [SD]: 5.1 [1.4]) for cognitive function, and 1 and 4 (5.4 [1.4]) for motor function. Cognitive and motor trajectories declined linearly between ages 45 and 65 years, followed by steeper declines after ages 65-70 years. Lower educated participants had lower cognitive function at age 45 years (baseline), and declined faster on most cognitive, but not on motor tests than higher educated participants. Up to a 25-year age difference between the fastest and slowest declining test scores was observed. CONCLUSIONS: On a population-level, cognitive and motor function decline similarly. Compared to higher educated individuals, lower educated individuals had lower cognitive function at baseline, and a faster rate of decline thereafter. These educational-effects were not seen for motor function. These findings benefit the understanding of the natural course of cognitive and motor function during aging, and highlight the role of education in the preservation of cognitive but not motor function.

Unraveling the Association Between Gait and Mortality-One Step at a Time.

BACKGROUND: Slowness of walking is one of the very first signs of aging and is considered a marker for overall health that is strongly associated with mortality risk. In this study, we sought to disentangle the clinical drivers of the association between gait and mortality. METHODS: We included 4,490 participants of the Rotterdam Study who underwent a gait assessment between 2009 and 2015 and were followed-up for mortality until 2018. Gait was assessed with an electronic walkway and summarized into the domains Rhythm, Phases, Variability, Pace, Tandem, Turning, and Base of Support. Cox models adjusted for age, sex, and height were built and consecutively adjusted for six categories of health indicators (lifestyle, musculoskeletal, cardiovascular, pulmonary, metabolic, and neurological). Analyses were repeated in comorbidity-free individuals. RESULTS: Multiple gait domains were associated with an increased risk of mortality, including Pace (hazard ratio (HR) per SD worse gait, adjusted for other domains: 1.34 [1.19-1.50]), Rhythm (HR: 1.12 [1.02-1.23]) and Phases (HR: 1.12 [1.03-1.21]). Similarly, a 0.1 m/s decrease in gait speed was associated with a 1.21 (1.15-1.27) times higher hazard of mortality (HR fully adjusted: 1.14 [1.08-1.20]). In a comorbidity-free subsample, the HR per 0.1 m/s decrease in gait speed was 1.25 (1.09-1.44). Cause-specific mortality analyses revealed an association between gait speed and multiple causes of death. CONCLUSIONS: Several gait domains were associated with mortality risk, including Pace which primarily represents gait speed. The association between gait speed and mortality persisted after an extensive adjustment for covariates, suggesting that gait is a marker for overall health.

TMS motor mapping: Comparing the absolute reliability of digital reconstruction methods to the golden standard.

BACKGROUND: Changes in transcranial magnetic stimulation motor map parameters can be used to quantify plasticity in the human motor cortex. The golden standard uses a counting analysis of motor evoked potentials (MEPs) acquired with a predefined grid. Recently, digital reconstruction methods have been proposed, allowing MEPs to be acquired with a faster pseudorandom procedure. However, the reliability of these reconstruction methods has never been compared to the golden standard. OBJECTIVE: To compare the absolute reliability of the reconstruction methods with the golden standard. METHODS: In 21 healthy subjects, both grid and pseudorandom acquisition were performed twice on the first day and once on the second day. The standard error of measurement was calculated for the counting analysis and the digital reconstructions. RESULTS: The standard error of measurement was at least equal using digital reconstructions. CONCLUSION: Pseudorandom acquisition and digital reconstruction can be used in intervention studies without sacrificing reliability.

Individual Differences in Motor Noise and Adaptation Rate Are Optimally Related.

Individual variations in motor adaptation rate were recently shown to correlate with movement variability or "motor noise" in a forcefield adaptation task. However, this finding could not be replicated in a meta-analysis of adaptation experiments. Possibly, this inconsistency stems from noise being composed of distinct components that relate to adaptation rate in different ways. Indeed, previous modeling and electrophysiological studies have suggested that motor noise can be factored into planning noise, originating from the brain, and execution noise, stemming from the periphery. Were the motor system optimally tuned to these noise sources, planning noise would correlate positively with adaptation rate, and execution noise would correlate negatively with adaptation rate, a phenomenon familiar in Kalman filters. To test this prediction, we performed a visuomotor adaptation experiment in 69 subjects. Using a novel Bayesian fitting procedure, we succeeded in applying the well-established state-space model of adaptation to individual data. We found that adaptation rate correlates positively with planning noise (ß = 0.44; 95% HDI = [0.27 0.59]) and negatively with execution noise (ß = -0.39; 95% HDI = [-0.50 -0.30]). In addition, the steady-state Kalman gain calculated from planning and execution noise correlated positively with adaptation rate (r = 0.54; 95% HDI = [0.38 0.66]). These results suggest that motor adaptation is tuned to approximate optimal learning, consistent with the "optimal control" framework that has been used to explain motor control. Since motor adaptation is thought to be a largely cerebellar process, the results further suggest the sensitivity of the cerebellum to both planning noise and execution noise.

Visual search accelerates during adolescence.

We studied changes in visual-search performance and behavior during adolescence. Search performance was analyzed in terms of reaction time and response accuracy. Search behavior was analyzed in terms of the objects fixated and the duration of these fixations. A large group of adolescents (N = 140; age: 12-19 years; 47% female, 53% male) participated in a visual-search experiment in which their eye movements were recorded with an eye tracker. The experiment consisted of 144 trials (50% with a target present), and participants had to decide whether a target was present. Each trial showed a search display with 36 Gabor patches placed on a hexagonal grid. The target was a vertically oriented element with a high spatial frequency. Nontargets differed from the target in spatial frequency, orientation, or both. Search performance and behavior changed during adolescence; with increasing age, fixation duration and reaction time decreased. Response accuracy, number of fixations, and selection of elements to fixate upon did not change with age. Thus, the speed of foveal discrimination increases with age, while the efficiency of peripheral selection does not change. We conclude that the way visual information is gathered does not change during adolescence, but the processing of visual information becomes faster.

Cerebellar transcranial direct current stimulation interacts with BDNF Val66Met in motor learning.

BACKGROUND: Cerebellar transcranial direct current stimulation has been reported to enhance motor associative learning and motor adaptation, holding promise for clinical application in patients with movement disorders. However, behavioral benefits from cerebellar tDCS have been inconsistent. OBJECTIVE: Identifying determinants of treatment success is necessary. BDNF Val66Met is a candidate determinant, because the polymorphism is associated with motor skill learning and BDNF is thought to mediate tDCS effects. METHODS: We undertook two cerebellar tDCS studies in subjects genotyped for BDNF Val66Met. Subjects performed an eyeblink conditioning task and received sham, anodal or cathodal tDCS (N = 117, between-subjects design) or a vestibulo-ocular reflex adaptation task and received sham and anodal tDCS (N = 51 subjects, within-subjects design). Performance was quantified as a learning parameter from 0 to 100%. We investigated (1) the distribution of the learning parameter with mixture modeling presented as the mean (M), standard deviation (S) and proportion (P) of the groups, and (2) the role of BDNF Val66Met and cerebellar tDCS using linear regression presented as the regression coefficients (B) and odds ratios (OR) with equally-tailed intervals (ETIs). RESULTS: For the eyeblink conditioning task, we found distinct groups of learners (MLearner = 67.2%; SLearner = 14.7%; PLearner = 61.6%) and non-learners (MNon-learner = 14.2%; SNon-learner = 8.0%; PNon-learner = 38.4%). Carriers of the BDNF Val66Met polymorphism were more likely to be learners (OR = 2.7 [1.2 6.2]). Within the group of learners, anodal tDCS supported eyeblink conditioning in BDNF Val66Met non-carriers (B = 11.9% 95%ETI = [0.8 23.0]%), but not in carriers (B = 1.0% 95%ETI = [-10.2 12.1]%). For the vestibulo-ocular reflex adaptation task, we found no effect of BDNF Val66Met (B = -2.0% 95%ETI = [-8.7 4.7]%) or anodal tDCS in either carriers (B = 3.4% 95%ETI = [-3.2 9.5]%) or non-carriers (B = 0.6% 95%ETI = [-3.4 4.8]%). Finally, we performed additional saccade and visuomotor adaptation experiments (N = 72) to investigate the general role of BDNF Val66Met in cerebellum-dependent learning and found no difference between carriers and non-carriers for both saccade (B = 1.0% 95%ETI = [-8.6 10.6]%) and visuomotor adaptation (B = 2.7% 95%ETI = [-2.5 7.9]%). CONCLUSIONS: The specific role for BDNF Val66Met in eyeblink conditioning, but not vestibulo-ocular reflex adaptation, saccade adaptation or visuomotor adaptation could be related to dominance of the role of simple spike suppression of cerebellar Purkinje cells with a high baseline firing frequency in eyeblink conditioning. Susceptibility of non-carriers to anodal tDCS in eyeblink conditioning might be explained by a relatively larger effect of tDCS-induced subthreshold depolarization in this group, which might increase the spontaneous firing frequency up to the level of that of the carriers.

Kidney function, gait pattern and fall in the general population: a cohort study.

Background: Gait disturbance is proposed as a mechanism for higher risk of fall in kidney disease patients. We investigated the association of kidney function with gait pattern in the general population and tested whether the association between impaired kidney function and fall is more pronounced in subjects with lower gait function. Methods: We included 1430 participants (mean age: 60 years) from the Rotterdam Study. Kidney function was assessed using estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR). We assessed global gait, gait velocity and seven independent gait domains: Rhythm, Phases, Variability, Pace, Tandem, Turning and Base of Support. Regression models adjusted for cardiometabolic and neurological factors were used. We evaluated whether participants with impaired kidney function and impaired gait fell more in the previous year. Results: The study population had a median (interquartile range) ACR of 3.6 (2.5-6.2) mg/g and mean ± SD eGFR of 87.6 ± 15 mL/min/1.73 m2. Higher ACR and lower eGFR were associated with lower global gait score [per doubling of ACR: -0.10, 95% confidence interval (CI): -0.14 to -0.06, and per SD eGFR:-0.09, 95% CI: -0.14 to -0.03] and slower gait speed (ACR: -1.44 cm/s, CI: -2.12 to -0.76; eGFR: -1.55 cm/s, CI: -2.43 to -0.67). Worse kidney function was associated with lower scores in Variability domain. The association between impaired kidney function and history of fall was present only in participants with lower gait scores [odds ratio (95% CI): ACR: 1.34 (1.09-1.65); eGFR: 1.58 (1.07-2.33)]. Conclusions: We observed a graded association between lower kidney function and impaired gait suggesting that individuals with decreased kidney function, even at an early stage, need to be evaluated for gait abnormalities and might benefit from fall prevention programmes.

Pain Experience is Somatotopically Organized and Overlaps with Pain Anticipation in the Human Cerebellum.

Many fMRI studies have shown activity in the cerebellum after peripheral nociceptive stimulation. We investigated whether the areas in the cerebellum that were activated after nociceptive thumb stimulation were separate from those after nociceptive toe stimulation. In an additional experiment, we investigated the same for the anticipation of a nociceptive stimulation on the thumb or toe. For his purpose, we used fMRI after an electrical stimulation of the thumb and toe in 19 adult healthy volunteers. Following nociceptive stimulation, different areas were activated by stimulation on the thumb (lobule VI ipsilaterally and Crus II mainly contralaterally) and toe (lobules VIII-IX and IV-V bilaterally and lobule VI contralaterally), i.e., were somatotopically organized. Cerebellar areas innervated non-somatotopically by both toe and thumb stimulation were the posterior vermis and Crus I, bilaterally. In the anticipation experiment, similar results were found. However, here, the somatotopically activated areas were relatively small for thumb and negligible for toe stimulation, while the largest area was innervated non-somatotopically and consisted mainly of Crus I and lobule VI bilaterally. These findings indicate that nociceptive stimulation and anticipation of nociceptive stimulation are at least partly processed by the same areas in the cerebellum. This was confirmed by an additional conjunction analysis. Based on our findings, we hypothesize that input that is organized in a somatotopical manner reflects direct input from the spinal cord, while non-somatotopically activated parts of the cerebellum receive their information indirectly through cortical and subcortical connections, possibly involved in processing contextual emotional states, like the expectation of pain.

Performance on tasks of visuospatial memory and ability: A cross-sectional study in 330 adolescents aged 11 to 20.

Cognitive functions mature at different points in time between birth and adulthood. Of these functions, visuospatial skills, such as spatial memory and part-to-whole organization, have often been tested in children and adults but have been less frequently evaluated during adolescence. We studied visuospatial memory and ability during this critical developmental period, as well as the correlation between these abilities, in a large group of 330 participants (aged 11 to 20 years, 55% male). To assess visuospatial memory, the participants were asked to memorize and reproduce sequences of random locations within a grid using a computer. Visuospatial ability was tested using a variation of the Design Organization Test (DOT). In this paper-and-pencil test, the participants had one minute to reproduce as many visual patterns as possible using a numerical code. On the memory task, compared with younger participants, older participants correctly reproduced more locations overall and longer sequences of locations, made fewer mistakes and needed less time to reproduce the sequences. In the visuospatial ability task, the number of correctly reproduced patterns increased with age. We show that both visuospatial memory and ability improve significantly throughout adolescence and that performance on both tasks is significantly correlated.

The influence of cervical movement on eye stabilization reflexes: a randomized trial.

To investigate the influence of the amount of cervical movement on the cervico-ocular reflex (COR) and vestibulo-ocular reflex (VOR) in healthy individuals. Eye stabilization reflexes, especially the COR, are changed in neck pain patients. In healthy humans, the strength of the VOR and the COR are inversely related. In a cross-over trial the amplitude of the COR and VOR (measured with a rotational chair with eye tracking device) and the active cervical range of motion (CROM) was measured in 20 healthy participants (mean age 24.7). The parameters were tested before and after two different interventions (hyperkinesia: 20 min of extensive active neck movement; and hypokinesia: 60 min of wearing a stiff neck collar). In an additional replication experiment the effect of prolonged (120 min) hypokinesia on the eye reflexes were tested in 11 individuals. The COR did not change after 60 min of hypokinesia, but did increase after prolonged hypokinesia (median change 0.220; IQR 0.168, p = 0.017). The VOR increased after 60 min of hypokinesia (median change 0.155, IQR 0.26, p = 0.003), but this increase was gone after 120 min of hypokinesia. Both reflexes were unaffected by cervical hyperkinesia. Diminished neck movements influences both the COR and VOR, although on a different time scale. However, increased neck movements do not affect the reflexes. These findings suggest that diminished neck movements could cause the increased COR in patients with neck complaints.

Polyneuropathy relates to impairment in daily activities, worse gait, and fall-related injuries.

OBJECTIVE: To extensively investigate the association of chronic polyneuropathy with basic and instrumental activities of daily living (BADL and IADL), falls, and gait. METHODS: A total of 1,445 participants of the population-based Rotterdam Study (mean age 71 years, 54% women) underwent a polyneuropathy screening involving a symptom questionnaire, neurologic examination, and nerve conduction studies. Screening yielded 4 groups: no, possible, probable, and definite polyneuropathy. Participants were interviewed about BADL (Stanford Health Assessment questionnaire), IADL (Instrumental Activities of Daily Living scale), and frequency of falling in the previous year. In a random subset of 977 participants, gait was assessed with an electronic walkway. Associations of polyneuropathy with BADL and IADL were analyzed continuously with linear regression and dichotomously with logistic regression. History of falling was evaluated with logistic regression, and gait changes were evaluated with linear regression. RESULTS: Participants with definite polyneuropathy had more difficulty in performing BADL and IADL than participants without polyneuropathy. Polyneuropathy related to worse scores of all BADL components (especially walking) and 3 IADL components (housekeeping, traveling, and shopping). Participants with definite polyneuropathy were more likely to fall, and these falls more often resulted in injury. Participants with polyneuropathy had worse gait parameters on the walkway, including lower walking speed and cadence, and more errors in tandem walking. CONCLUSIONS: Chronic polyneuropathy strongly associates with impairment in the ability to perform daily activities and relates to worse gait and an increased history of falling.

Cerebellar patients do not benefit from cerebellar or M1 transcranial direct current stimulation during force-field reaching adaptation.

Several studies have identified transcranial direct current stimulation (tDCS) as a potential tool in the rehabilitation of cerebellar disease. Here, we tested whether tDCS could alleviate motor impairments of subjects with cerebellar degeneration. Three groups took part in this study: 20 individuals with cerebellar degeneration, 20 age-matched controls, and 30 young controls. A standard reaching task with force-field perturbations was used to compare motor adaptation among groups and to measure the effect of stimulation of the cerebellum or primary motor cortex (M1). Cerebellar subjects and age-matched controls were tested during each stimulation type (cerebellum, M1, and sham) with a break of 1 wk among each of the three sessions. Young controls were tested during one session under one of three stimulation types (anodal cerebellum, cathodal cerebellum, or sham). As expected, individuals with cerebellar degeneration had a reduced ability to adapt to motor perturbations. Importantly, cerebellar patients did not benefit from anodal stimulation of the cerebellum or M1. Furthermore, no stimulation effects could be detected in aging and young controls. The present null results cannot exclude more subtle tDCS effects in larger subject populations and between-subject designs. Moreover, it is still possible that tDCS affects motor adaptation in cerebellar subjects and control subjects under a different task or with alternative stimulation parameters. However, for tDCS to become a valuable tool in the neurorehabilitation of cerebellar disease, stimulation effects should be present in group sizes commonly used in this rare patient population and be more consistent and predictable across subjects and tasks.NEW & NOTEWORTHY Transcranial direct current stimulation (tDCS) has been identified as a potential tool in the rehabilitation of cerebellar disease. We investigated whether tDCS of the cerebellum and primary motor cortex could alleviate motor impairments of subjects with cerebellar degeneration. The present study did not find stimulation effects of tDCS in young controls, aging controls, and individuals with cerebellar degeneration during reach adaptation. Our results require a re-evaluation of the clinical potential of tDCS in cerebellar patients.

Asymptomatic radiographic hip osteoarthritis is associated with gait differences, especially in women: A population-based study.

BACKGROUND: Hip and knee osteoarthritis (OA) are debilitating diseases that impair gait at severe stages. Although associations between OA and gait are established for normal walking, little is known about its relation with turning and tandem (heel-to-toe) walking. Furthermore, it is unknown how asymptomatic OA associates with gait, and whether associations differ by sex. We investigated how symptomatic and asymptomatic hip and knee OA associate with gait in community-dwelling individuals. METHODS: In 2706 participants of a population-based cohort study, gait was assessed by electronic walkway and summarised into seven gait domains. Hip and knee radiographs were graded for radiographic OA (ROA) using the Kellgren and Lawrence (K&L) score. Linear regression was used to investigate associations between ROA and gait. Analyses were repeated including only participants with asymptomatic ROA, defined as a K&L-score of 2 without pain. RESULTS: In total, 177 participants (6.5%) had hip ROA and 441 (16.3%) knee ROA. We found no associations of knee ROA with gait. Hip ROA associated with Rhythm, Tandem, and Turning. Furthermore, unilateral hip ROA associated with larger gait asymmetry and gait differences in osteoarthritic and non-osteoarthritic leg, when compared to people without hip ROA. Associations between hip ROA and gait were generally stronger for women than men. Associations for hip ROA remained after restricting to asymptomatic ROA. CONCLUSION: Hip ROA, but not knee ROA, associates with gait differences in normal walking, turning, and tandem walking in community-dwelling individuals. These associations differ between the sexes, and are already present for asymptomatic ROA.

Cerebellar tDCS Does Not Enhance Performance in an Implicit Categorization Learning Task.

Background: Transcranial Direct Current Stimulation (tDCS) is a form of non-invasive electrical stimulation that changes neuronal excitability in a polarity and site-specific manner. In cognitive tasks related to prefrontal and cerebellar learning, cortical tDCS arguably facilitates learning, but the few studies investigating cerebellar tDCS, however, are inconsistent. Objective: We investigate the effect of cerebellar tDCS on performance of an implicit categorization learning task. Methods: Forty participants performed a computerized version of an implicit categorization learning task where squares had to be sorted into two categories, according to an unknown but fixed rule that integrated both the size and luminance of the square. Participants did one round of categorization to familiarize themselves with the task and to provide a baseline of performance. After that, 20 participants received anodal tDCS (20 min, 1.5 mA) over the right cerebellum, and 19 participants received sham stimulation and simultaneously started a second session of the categorization task using a new rule. Results: As expected, subjects performed better in the second session than in the first, baseline session, showing increased accuracy scores and reduced reaction times. Over trials, participants learned the categorization rule, improving their accuracy and reaction times. However, we observed no effect of anodal tDCS stimulation on overall performance or on learning, compared to sham stimulation. Conclusion: These results suggest that cerebellar tDCS does not modulate performance and learning on an implicit categorization task.