Different Sensory Information Is Used for State Estimation when Stationary or Moving.

The accurate estimation of limb state is necessary for movement planning and execution. While state estimation requires both feedforward and feedback information, we focus here on the latter. Prior literature has shown that integrating visual and proprioceptive feedback improves estimates of static limb position.

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.

Reinforcement Motor Learning After Cerebellar Damage Is Related to State Estimation.

Recent work showed that individuals with cerebellar degeneration could leverage intact reinforcement learning (RL) to alter their movement. However, there was marked inter-individual variability in learning, and the factors underlying it were unclear. Cerebellum-dependent sensory prediction may contribute to RL in motor contexts by enhancing body state estimates, which are necessary to solve the credit-assignment problem.

Different sensory information is used for state estimation when stationary or moving.

The accurate estimation of limb state is necessary for movement planning and execution. While state estimation requires both feedforward and feedback information, we focus here on the latter. Prior literature has shown that integrating visual and proprioceptive feedback improves estimates of static limb position.

Mechanisms of Human Motor Learning Do Not Function Independently.

Human motor learning is governed by a suite of interacting mechanisms each one of which modifies behavior in distinct ways and rely on different neural circuits. In recent years, much attention has been given to one type of motor learning, called motor adaptation. Here, the field has generally focused on the interactions of three mechanisms: sensory prediction error SPE-driven, explicit (strategy-based), and reinforcement learning.

Cerebellar Dysfunction in Multiple Sclerosis: Considerations for Research and Rehabilitation Therapy.

. Cerebellar pathology is common among persons with multiple sclerosis (PwMS). The cerebellum is well recognized for its role in motor control and motor learning and cerebellar pathology in multiple sclerosis is associated with enhanced motor impairment and disability progression.

Is the dynamic gait index a useful outcome to measure balance and ambulation in patients with cerebellar ataxia?

Background: Ataxia can adversely affect balance and gait and increase the incidence of falls, which puts individuals at greater risk for injury. Thus, interventions focused on balance and gait are integral in rehabilitation training. In order to determine if rehabilitation interventions are effective, we need an outcome measure to detect change.

Aberrant activity in an intact residual muscle is associated with phantom limb pain in above-knee amputees.

Many individuals who undergo limb amputation experience persistent phantom limb pain (PLP), but the underlying mechanisms of PLP are unknown. The traditional hypothesis was that PLP resulted from maladaptive plasticity in sensorimotor cortex that degrades the neural representation of the missing limb. However, a recent study of individuals with upper limb amputations has shown that PLP is correlated with aberrant electromyographic (EMG) activity in residual muscles, posited to reflect a retargeting of efferent projections from a preserved representation of a missing limb.

Can the ARAT Be Used to Measure Arm Function in People With Cerebellar Ataxia?

Objective: For people with ataxia, there are validated outcome measures to address body function and structure (BFS) impairments and participation; however, no outcome measure exists for upper extremity (UE) activity level in this population. The purpose of this study was to determine whether the action research arm test (ARAT), a measure of UE activity validated for other neurological conditions, might be a useful outcome measure for capturing UE activity limitations in ataxia.

Methods: A total of 22 participants with ataxia were evaluated to assess construct validity of the ARAT; 19 of the participants were included in the interrater reliability assessment.

Reinforcement Signaling Can Be Used to Reduce Elements of Cerebellar Reaching Ataxia.

Damage to the cerebellum causes a disabling movement disorder called ataxia, which is characterized by poorly coordinated movement. Arm ataxia causes dysmetria (over- or under-shooting of targets) with many corrective movements. As a result, people with cerebellar damage exhibit reaching movements with highly irregular and prolonged movement paths.

Interactions between motor exploration and reinforcement learning.

Motor exploration, a trial-and-error process in search for better motor outcomes, is known to serve a critical role in motor learning. This is particularly relevant during reinforcement learning, where actions leading to a successful outcome are reinforced while unsuccessful actions are avoided. Although early on motor exploration is beneficial to finding the correct solution, maintaining high levels of exploration later in the learning process might be deleterious.

Increasing Motor Noise Impairs Reinforcement Learning in Healthy Individuals.

Motor variability from exploration is crucial for reinforcement learning as it allows the nervous system to find new task solutions. However, motor variability from noise can be detrimental to learning and may underlie slowed reinforcement learning performance observed in individuals with cerebellar damage. Here we examine whether artificially increasing noise in healthy individuals slows reinforcement learning in a manner similar to that seen in patients with cerebellar damage.

The cerebellum as a movement sensor.

In this article, we review a broad range of studies of cerebellar function and dysfunction and interpret them within the framework that the cerebellum acts as part of a mechanism of predictive control. We describe studies that span human behaviour and consider the motor and sensory impairments that result from cerebellar damage. We conclude that a parsimonious explanation of cerebellar function is as a predictor of the sensory outcomes of movement.

The cerebellum contributes to proprioception during motion.

Proprioception, the sense of limb position and motion, is essential for generating accurate movements. Limb position sense has typically been studied under static conditions (i.e.

Proprioceptive Localization Deficits in People With Cerebellar Damage.

It has been hypothesized that an important function of the cerebellum is predicting the state of the body during movement. Yet, the extent of cerebellar involvement in perception of limb state (i.e.

Effective reinforcement learning following cerebellar damage requires a balance between exploration and motor noise.

Reinforcement and error-based processes are essential for motor learning, with the cerebellum thought to be required only for the error-based mechanism. Here we examined learning and retention of a reaching skill under both processes. Control subjects learned similarly from reinforcement and error-based feedback, but showed much better retention under reinforcement.

Cerebellar damage impairs internal predictions for sensory and motor function.

The cerebellum is connected to cerebral areas that subserve a range of sensory and motor functions. In this review, we summarize new literature demonstrating deficits in visual perception, proprioception, motor control, and motor learning performance following cerebellar damage. In particular, we highlight novel results that together suggest a general role of the cerebellum in estimating and predicting movement dynamics of the body and environmental stimuli.

Continuous theta-burst stimulation to primary motor cortex reveals asymmetric compensation for sensory attenuation in bimanual repetitive force production.

Studies of fingertip force production have shown that self-produced forces are perceived as weaker than externally generated forces. This is due to mechanisms of sensory reafference where the comparison between predicted and actual sensory feedback results in attenuated perceptions of self-generated forces. Without an external reference to calibrate attenuated performance judgments, a compensatory overproduction of force is exhibited.

Sensory attenuation of self-produced feedback: the Lombard effect revisited.

The Lombard effect describes the automatic and involuntary increase in vocal intensity that speakers exhibit in a noisy environment. Previous studies of the Lombard effect have typically focused on the relationship between speaking and hearing. Automatic and involuntary increases in motor output have also been noted in studies of finger force production, an effect attributed to mechanisms of sensory attenuation.

Continuous theta-burst stimulation to primary motor cortex reduces the overproduction of forces following removal of visual feedback.

Forward models, generated from the efference copies of motor commands, are thought to monitor the accuracy of ongoing movement. By comparing predicted with actual afferent information, forward models also aid in the differentiation of self-produced movements from externally generated ones. Many have proposed that a consequence of this comparison is attenuation of the predicted component of incoming sensory signals.

Repetitive finger force production in predictable environments.

Previous research suggests that removal of visual feedback of force output in a sequential force production task results in a continuous escalation of the force magnitudes produced. Central predictive mechanisms involving reafference result in self-generated forces being perceived as weaker, thus leading to a systematic over-production of force. While this effect has been widely examined with respect to sensation of self-produced stimuli, its role in the sequential production of discrete forces has not been extensively studied.

Timing and visual feedback constraints on repetitive finger force production.

While much is known about sequential effects in motor timing, less is understood about whether movement parameters such as force show sequential dependencies. In this study, we examined the effect of timing constraints on repetitive unimanual force production sequences. Ten healthy participants produced a series of pinch grip forces in time to a metronome and to visually specified force amplitudes.