Background and Objectives:Individuals with cerebellar ataxia (CA) can develop impulsive behavioral symptoms, often resulting in negative interpersonal consequences, detrimentally impacting their quality of life. Limited evidence exists concerning impulsivity in CA and its associated behavioral changes. We assessed impulsive traits in CA using the Barratt impulsivity scale (BIS-11) and compared them with those of Parkinson disease (PD), in order to investigate the differences in the impulsive trait profiles between CA and PD.Methods:We conducted a dual-center cross-sectional study with CA and PD subjects enrolled through consecutive sampling from movement disorders clinics at Columbia University Medical Center and Vanderbilt University Medical Center, respectively. Age-matched controls were recruited at the respective institutions. Participants were excluded if they had prior or comorbid neurological and psychiatric diseases known to be associated with impulsivity. All subjects completed the BIS-11 questionnaire as a measure of impulsive traits. We used a general linear model and a least absolute shrinkage and selection operation regression to compare the total, subscale, and individual items of the BIS-11 scores between groups. Subgroup analyses were performed to isolate cerebellar contributions to impulsivity from potential effects of extracerebellar pathology and dopaminergic dysfunction or medications.Results:A total of 190 participants: 90 age-matched controls, 50 CA, and 50 PD participants completed the assessments. Persons with CA reported 9.7% greater BIS-11 scores than controls (p < 0.001), while persons with PD participants reported 24.9% higher than controls (p < 0.001). In CA, the most impacted domain of impulsivity was non-planning. In contrast, persons with PD noted greater impulsivity across the non-planning, attentional, and motor domains.Discussion:Impulsivity in CA is uniquely driven by the non-planning trait, unlike in PD. This suggests that the cerebellum and basal ganglia may differentially govern impulsive behaviors with the cerebellum contributing to the brain circuitry of impulsivity in a domain-specific manner.

Background – A promising new approach, transcranial direct current stimulation (tDCS) has recently been used as a therapeutic modality for cerebellar ataxia. However, the strength of the conclusions drawn from individual studies in the current literature may be constrained by the small sample size of each trial. Methods – Following a systematic literature retrieval of studies, meta-analyses were conducted by pooling the standardized mean differences (SMDs) using random-effects models to assess the efficacy of tDCS on cerebellar ataxia, measured by standard clinical rating scales. Domain-specific effects of tDCS on gait and hand function were further evaluated based on 8-meter walk and 9-hole peg test performance times, respectively. To determine the safety of tDCS, the incidences of adverse effects were analyzed using risk differences. Results – Out of 293 citations, 5 randomized controlled trials involving a total of 72 participants with cerebellar ataxia were included. Meta-analysis indicated a 26.1% ( p = 0.003) improvement in ataxia immediately after tDCS with sustained efficacy over months (28.2% improvement after 3 months, p = 0.04) when compared to sham stimulation. tDCS seems to be domain-specific as the current analysis suggested a positive effect on gait (16.3% improvement, p = 0.04), however failed to reveal differences for hand function ( p = 0.10) with respect to sham. The incidence of adverse events in tDCS and sham groups was similar. Conclusion – tDCS is an effective intervention for mitigating ataxia symptoms with lasting results that can be sustained for months. This treatment shows preferential effects on gait ataxia and is relatively safe.

The brain can learn to generate actions, such as reaching to a target, using different movement strategies. Understanding how different variables bias which strategies are learned to produce such a reach is important for our understanding of the neural bases of movement. Here we introduce a novel spatial forelimb target task in which perched head-fixed mice learn to reach to a circular target area from a set start position using a joystick. These reaches can be achieved by learning to move into a specific direction or to a specific endpoint location. We find that mice gradually learn to successfully reach the covert target. With time, they refine their initially exploratory complex joystick trajectories into controlled targeted reaches. The execution of these controlled reaches depends on the sensorimotor cortex. Using a probe test with shifting start positions, we show that individual mice learned to use strategies biased to either direction or endpoint-based movements. The degree of endpoint learning bias was correlated with the spatial directional variability with which the workspace was explored early in training. Furthermore, we demonstrate that reinforcement learning model agents exhibit a similar correlation between directional variability during training and learned strategy. These results provide evidence that individual exploratory behavior during training biases the control strategies that mice use to perform forelimb covert target reaches.