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Cerebellum (London, England) Jun 2016The cerebellum is involved in sensorimotor operations, cognitive tasks and affective processes. Here, we revisit the concept of the cerebellar syndrome in the light of... (Review)
Review
The cerebellum is involved in sensorimotor operations, cognitive tasks and affective processes. Here, we revisit the concept of the cerebellar syndrome in the light of recent advances in our understanding of cerebellar operations. The key symptoms and signs of cerebellar dysfunction, often grouped under the generic term of ataxia, are discussed. Vertigo, dizziness, and imbalance are associated with lesions of the vestibulo-cerebellar, vestibulo-spinal, or cerebellar ocular motor systems. The cerebellum plays a major role in the online to long-term control of eye movements (control of calibration, reduction of eye instability, maintenance of ocular alignment). Ocular instability, nystagmus, saccadic intrusions, impaired smooth pursuit, impaired vestibulo-ocular reflex (VOR), and ocular misalignment are at the core of oculomotor cerebellar deficits. As a motor speech disorder, ataxic dysarthria is highly suggestive of cerebellar pathology. Regarding motor control of limbs, hypotonia, a- or dysdiadochokinesia, dysmetria, grasping deficits and various tremor phenomenologies are observed in cerebellar disorders to varying degrees. There is clear evidence that the cerebellum participates in force perception and proprioceptive sense during active movements. Gait is staggering with a wide base, and tandem gait is very often impaired in cerebellar disorders. In terms of cognitive and affective operations, impairments are found in executive functions, visual-spatial processing, linguistic function, and affective regulation (Schmahmann's syndrome). Nonmotor linguistic deficits including disruption of articulatory and graphomotor planning, language dynamics, verbal fluency, phonological, and semantic word retrieval, expressive and receptive syntax, and various aspects of reading and writing may be impaired after cerebellar damage. The cerebellum is organized into (a) a primary sensorimotor region in the anterior lobe and adjacent part of lobule VI, (b) a second sensorimotor region in lobule VIII, and (c) cognitive and limbic regions located in the posterior lobe (lobule VI, lobule VIIA which includes crus I and crus II, and lobule VIIB). The limbic cerebellum is mainly represented in the posterior vermis. The cortico-ponto-cerebellar and cerebello-thalamo-cortical loops establish close functional connections between the cerebellum and the supratentorial motor, paralimbic and association cortices, and cerebellar symptoms are associated with a disruption of these loops.
Topics: Cerebellar Diseases; Cerebellum; Humans
PubMed: 26105056
DOI: 10.1007/s12311-015-0687-3 -
Philosophical Transactions of the Royal... Apr 2017If a visual object of interest suddenly starts to move, we will try to follow it with a smooth movement of the eyes. This response aims to reduce image motion on the... (Review)
Review
If a visual object of interest suddenly starts to move, we will try to follow it with a smooth movement of the eyes. This response aims to reduce image motion on the retina that could blur visual perception. In recent years, our knowledge of the neural control of smooth pursuit initiation has sharply increased. However, stopping smooth pursuit eye movements is less well understood and will be discussed in this paper. The most straightforward way to study smooth pursuit stopping is by interrupting image motion on the retina. This causes eye velocity to decay exponentially towards zero. However, smooth pursuit stopping is not a passive response, as shown by behavioural and electrophysiological evidence. Moreover, smooth pursuit stopping is particularly influenced by active prediction of the upcoming end of the target. Here, we suggest that a particular class of inhibitory neurons of the brainstem, the omnipause neurons, could play a central role in pursuit stopping. Furthermore, the role of supplementary eye fields of the frontal cortex in smooth pursuit stopping is also discussed.This article is part of the themed issue 'Movement suppression: brain mechanisms for stopping and stillness'.
Topics: Animals; Brain Stem; Humans; Inhibition, Psychological; Macaca mulatta; Neurons; Pursuit, Smooth; Visual Perception
PubMed: 28242734
DOI: 10.1098/rstb.2016.0200 -
Annual Review of Vision Science Sep 2021In healthy vision, the fovea provides high acuity and serves as the locus for fixation achieved through saccadic eye movements. Bilateral loss of the foveal regions in... (Review)
Review
In healthy vision, the fovea provides high acuity and serves as the locus for fixation achieved through saccadic eye movements. Bilateral loss of the foveal regions in both eyes causes individuals to adopt an eccentric locus for fixation. This review deals with the eye movement consequences of the loss of the foveal oculomotor reference and the ability of individuals to use an eccentric fixation locus as the new oculomotor reference. Eye movements are an integral part of everyday activities, such as reading, searching for an item of interest, eye-hand coordination, navigation, or tracking an approaching car. We consider how these tasks are impacted by the need to use an eccentric locus for fixation and as a reference for eye movements, specifically saccadic and smooth pursuit eye movements.
Topics: Eye Movements; Humans; Macular Degeneration; Pursuit, Smooth; Saccades; Vision, Ocular
PubMed: 34038144
DOI: 10.1146/annurev-vision-100119-125555 -
Seminars in Hearing Aug 2018Oculomotor evaluation as part of videonystagmography is an integral tool in the assessment of vestibular function providing a global assessment of the neurological... (Review)
Review
Oculomotor evaluation as part of videonystagmography is an integral tool in the assessment of vestibular function providing a global assessment of the neurological pathways associated with oculomotor function. The value of an oculomotor evaluation for pediatric evaluation is well established; however, many questions can also arise with the application to the pediatric population. Oculomotor function is age dependent which can have a significant effect on the test results obtain in children. The underlying neural substrates and age effects are discussed across the literature with specific results from recent research using clinical oculomotor equipment and protocols. The evidence suggests there are several key differences in the pediatric population compared with adults. These include longer saccade latencies, reduced smooth pursuit gain, increased optokinetic asymmetry, increased variability in all responses, and increased artifact in saccade and smooth pursuit testing.
PubMed: 30038455
DOI: 10.1055/s-0038-1666818 -
Journal of Neurologic Physical Therapy... Apr 2016Uncompensated vestibular hypofunction results in postural instability, visual blurring with head movement, and subjective complaints of dizziness and/or imbalance. We...
Vestibular Rehabilitation for Peripheral Vestibular Hypofunction: An Evidence-Based Clinical Practice Guideline: FROM THE AMERICAN PHYSICAL THERAPY ASSOCIATION NEUROLOGY SECTION.
BACKGROUND
Uncompensated vestibular hypofunction results in postural instability, visual blurring with head movement, and subjective complaints of dizziness and/or imbalance. We sought to answer the question, "Is vestibular exercise effective at enhancing recovery of function in people with peripheral (unilateral or bilateral) vestibular hypofunction?"
METHODS
A systematic review of the literature was performed in 5 databases published after 1985 and 5 additional sources for relevant publications were searched. Article types included meta-analyses, systematic reviews, randomized controlled trials, cohort studies, case control series, and case series for human subjects, published in English. One hundred thirty-five articles were identified as relevant to this clinical practice guideline.
RESULTS/DISCUSSION
Based on strong evidence and a preponderance of benefit over harm, clinicians should offer vestibular rehabilitation to persons with unilateral and bilateral vestibular hypofunction with impairments and functional limitations related to the vestibular deficit. Based on strong evidence and a preponderance of harm over benefit, clinicians should not include voluntary saccadic or smooth-pursuit eye movements in isolation (ie, without head movement) as specific exercises for gaze stability. Based on moderate evidence, clinicians may offer specific exercise techniques to target identified impairments or functional limitations. Based on moderate evidence and in consideration of patient preference, clinicians may provide supervised vestibular rehabilitation. Based on expert opinion extrapolated from the evidence, clinicians may prescribe a minimum of 3 times per day for the performance of gaze stability exercises as 1 component of a home exercise program. Based on expert opinion extrapolated from the evidence (range of supervised visits: 2-38 weeks, mean = 10 weeks), clinicians may consider providing adequate supervised vestibular rehabilitation sessions for the patient to understand the goals of the program and how to manage and progress themselves independently. As a general guide, persons without significant comorbidities that affect mobility and with acute or subacute unilateral vestibular hypofunction may need once a week supervised sessions for 2 to 3 weeks; persons with chronic unilateral vestibular hypofunction may need once a week sessions for 4 to 6 weeks; and persons with bilateral vestibular hypofunction may need once a week sessions for 8 to 12 weeks. In addition to supervised sessions, patients are provided a daily home exercise program.
DISCLAIMER
These recommendations are intended as a guide for physical therapists and clinicians to optimize rehabilitation outcomes for persons with peripheral vestibular hypofunction undergoing vestibular rehabilitation.Video Abstract available for more insights from the author (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A124).
Topics: Dizziness; Evidence-Based Practice; Humans; Physical Therapy Modalities; Postural Balance; Treatment Outcome; Vestibular Diseases
PubMed: 26913496
DOI: 10.1097/NPT.0000000000000120 -
Journal of Alzheimer's Disease : JAD 2015A growing body of literature has investigated changes in eye movements as a result of Alzheimer's disease (AD). When compared to healthy, age-matched controls, patients... (Review)
Review
A growing body of literature has investigated changes in eye movements as a result of Alzheimer's disease (AD). When compared to healthy, age-matched controls, patients display a number of remarkable alterations to oculomotor function and viewing behavior. In this article, we review AD-related changes to fundamental eye movements, such as saccades and smooth pursuit motion, in addition to changes to eye movement patterns during more complex tasks like visual search and scene exploration. We discuss the cognitive mechanisms that underlie these changes and consider the clinical significance of eye movement behavior, with a focus on eye movements in mild cognitive impairment. We conclude with directions for future research.
Topics: Alzheimer Disease; Attention Deficit Disorder with Hyperactivity; Cognition Disorders; Eye Movements; Humans; Photic Stimulation; Psychomotor Performance
PubMed: 25182738
DOI: 10.3233/JAD-141173 -
Journal of Clinical Neurophysiology :... Nov 2019The cerebellum works as a network hub for optimizing eye movements through its mutual connections with the brainstem and beyond. Here, we review three key areas in the... (Review)
Review
The cerebellum works as a network hub for optimizing eye movements through its mutual connections with the brainstem and beyond. Here, we review three key areas in the cerebellum that are related to the control of eye movements: (1) the flocculus/paraflocculus (tonsil) complex, primarily for high-frequency, transient vestibular responses, and also for smooth pursuit maintenance and steady gaze holding; (2) the nodulus/ventral uvula, primarily for low-frequency, sustained vestibular responses; and (3) the dorsal vermis/posterior fastigial nucleus, primarily for the accuracy of saccades. Although there is no absolute compartmentalization of function within the three major ocular motor areas in the cerebellum, the structural-functional approach provides a framework for assessing ocular motor performance in patients with disease that involves the cerebellum or the brainstem.
Topics: Animals; Cerebellum; Eye Movements; Humans; Ocular Motility Disorders
PubMed: 31688323
DOI: 10.1097/WNP.0000000000000579 -
Brain Sciences Aug 2023Non-motor symptoms in Parkinson's disease (PD) include ocular, visuoperceptive, and visuospatial impairments, which can occur as a result of the underlying... (Review)
Review
Non-motor symptoms in Parkinson's disease (PD) include ocular, visuoperceptive, and visuospatial impairments, which can occur as a result of the underlying neurodegenerative process. Ocular impairments can affect various aspects of vision and eye movement. Thus, patients can show dry eyes, blepharospasm, reduced blink rate, saccadic eye movement abnormalities, smooth pursuit deficits, and impaired voluntary and reflexive eye movements. Furthermore, visuoperceptive impairments affect the ability to perceive and recognize visual stimuli accurately, including impaired contrast sensitivity and reduced visual acuity, color discrimination, and object recognition. Visuospatial impairments are also remarkable, including difficulties perceiving and interpreting spatial relationships between objects and difficulties judging distances or navigating through the environment. Moreover, PD patients can present visuospatial attention problems, with difficulties attending to visual stimuli in a spatially organized manner. Moreover, PD patients also show perceptual disturbances affecting their ability to interpret and determine meaning from visual stimuli. And, for instance, visual hallucinations are common in PD patients. Nevertheless, the neurobiological bases of visual-related disorders in PD are complex and not fully understood. This review intends to provide a comprehensive description of visual disturbances in PD, from sensory to perceptual alterations, addressing their neuroanatomical, functional, and neurochemical correlates. Structural changes, particularly in posterior cortical regions, are described, as well as functional alterations, both in cortical and subcortical regions, which are shown in relation to specific neuropsychological results. Similarly, although the involvement of different neurotransmitter systems is controversial, data about neurochemical alterations related to visual impairments are presented, especially dopaminergic, cholinergic, and serotoninergic systems.
PubMed: 37626529
DOI: 10.3390/brainsci13081173 -
Journal of Neurotrauma Jan 2020Smooth pursuit eye movements (SPEMs) and saccadic eye movements are both commonly impaired following sport-related concussion (SRC). Typical oculomotor assessments...
Smooth pursuit eye movements (SPEMs) and saccadic eye movements are both commonly impaired following sport-related concussion (SRC). Typical oculomotor assessments measure individual eye movements in a series of restrictive tests designed to isolate features such as response times. These measures lack ecological validity for athletes because athletes are adept at simple tasks designed for the general population. Yet, because eye movement metrics are sensitive and well-characterized neuroanatomically, it would be valuable to test whether athletes exhibit abnormal eye movements with more challenging tasks. To address this gap in knowledge, we collected eye-tracking data during a sport-like task to gain insight on gaze behavior during active self-motion. SPEMs and saccadic eye movements were recorded during a sport-like visual task within 24-48 h following SRC. Thirty-six Division I student-athletes were divided into SRC and control (CON) groups. All participants completed two blocks of the Wii Fit soccer heading game (WF) while wearing a monocular infrared eye tracker. Eye movement classification systems quantified saccadic amplitude (SA), velocity (SV), and count (SC); as well as SPEM velocity (SPV) and amplitude (SPA). Separate Mann-Whitney U tests evaluated SPA and SC and found no significant effects (SPA, = 0.11; SC, = 0.10). A multi-variate analysis of variance (MANOVA) for remaining variables revealed SPV was significantly greater in CON ( < 0.05), but the SRC group had greater SA and SV ( < 0.05). These findings suggest that during a sport-like task, to maintain foveation SRC subjects used larger amplitude, faster saccades, but exhibited slower SPEMs. Measuring oculomotor function during ecologically valid, sport-like tasks may serve as a concussion biomarker and provide insights into eye movement control after SRC.
Topics: Adolescent; Athletes; Athletic Injuries; Brain Concussion; Female; Humans; Male; Pursuit, Smooth; Saccades
PubMed: 31524054
DOI: 10.1089/neu.2019.6595