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Cortical Visual Loss
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Tests for motion perception require computerized displays that are not available in most clinics. Smooth pursuit eye movements depend on motion perception, and LM and AF had impaired smooth pursuit (348), but one can have impaired motion perception with normal smooth pursuit and vice versa (357). Patients with akinetopsia can tell when something is moving (348) and they can see the direction of simple moving dots or patterns (349, 351, 352), but they cannot see differences in speed or discern the overall direction of flow in noisy displays that contain other elements that are stationary or moving randomly (351, 352, 358). They have trouble using motion cues in searching for objects (355) or identifying the shapes of objects defined by differences in motion between the object and the background (352, 358). They also struggle with lip-reading (354).
Physiology of Three-Dimensional Eye Movements: Smooth Pursuit and Vestibulo-Ocular Reflex
Published in Michael Fetter, Thomas Haslwanter, Hubert Misslisch, Douglas Tweed, Three-Dimensional Kinematics of Eye, Head and Limb Movements, 2020
As mentioned above, the neural control of smooth pursuit eye movements has to solve the problem of redundant degrees of freedom because, at any moment, point targets can be tracked by rotating the eye around infinitely many axes. 3D rotation axes are conveniently described by the angular velocity vector, which is defined by applying the right-hand rule: if you point your right thumb in the direction of the velocity vector, the fingers curl round in the direction the body is spinning and the vector’s length denotes the speed of rotation.
Motor Aspects of Lateralization: Evidence for Evaluation of the Hypotheses of Chapter 8
Published in Robert Miller, Axonal Conduction Time and Human Cerebral Laterality, 2019
Two papers report on laterality of smooth pursuit eye movements in normal subjects, both using concurrent tasks as a means of assessing the contributions of each hemisphere. Larmande et al. (1985) studied the effect of visual pursuit on lateralized performance in a dichotic listening task. Visual pursuit, in whatever direction, interfered with right hemisphere function in the dichotic listening task. Sava et al. (1988) exposed normal subjects to a variety of visual tracking tasks. Concurrently, the subjects were given a reaction time test to simple stimuli presented in either left or right visual fields. For three out of the four tracking tasks, reaction time in the left field was increased, while right field reaction time was unchanged. This indicates that the visual tracking tasks engaged the activity of the right hemisphere rather than the left. The exceptional test was the one where the movement of the tracked stimulus was most predictable. We have already seen that in manual tracking tasks right hand superiority can occur for tracking predictable moving targets, and is then not based on superior visual feedback but on more accurate programs to an extrapolated target position.
The Effect of Target Velocity on the Fast Corrective Response during Reaching Movement
Published in Journal of Motor Behavior, 2022
Kosuke Numasawa, Tomohiro Kizuka, Seiji Ono
In our experiment, participants were required to track the target motion, unlike the MFR. When we look at a small moving object, smooth pursuit eye movements are used to hold the target image on the fovea (Krauzlis, 2004; Lisberger, 2010; Ono, 2015). Smooth pursuit eye movements are driven by retinal slip signals generated from the difference between actual target motion and eye velocity. In particular, retinal slip information carried in the MT/MST plays an important role in the initial part of smooth pursuit (Dursteler & Wurtz, 1988; Newsome et al., 1985). As mentioned above, since arm movements responding to visual motion are associated with neuronal activity in the MT/MST, we speculate that the fast corrective response shares the same visual motion processing as smooth pursuit eye movements. Indeed, our results indicate that the initial amplitude (first 50 ms) of the corrective response increases according to the target velocity. However, a previous study has reported that the initial part of smooth pursuit (open-loop period) is not dependent on target velocity (Lisberger & Westbrook, 1985). Thus, one possible explanation is that the initiation of arm movement is generated differently from the eye movement, even though they both share a common retinal slip signal. Indeed, Saijo et al. (2005) have suggested that the MFR and the eye movements elicited by the large-field visual motion are separated even they are processed by the same visual information in parallel (Saijo et al., 2005).
Eye Movement Abnormalities in Amyotrophic Lateral Sclerosis in a Tunisian Cohort
Published in Neuro-Ophthalmology, 2022
Arwa Rekik, Saloua Mrabet, Imen Kacem, Amina Nasri, Mouna Ben Djebara, Amina Gargouri, Riadh Gouider
Altered horizontal smooth pursuits were the most common eye movement abnormality among our patients. However, results do diverge when it comes to studying smooth pursuits in ALS patients. For example, Shaunak and collaborators found that smooth pursuits were normal in all of the 17 patients involved in their study.22 Gizzi and co-authors found them altered, but only in patients who had associated Parkinsonism.18 Recent studies conducted on the Korean population by Kang et al. found, similar to our study that altered horizontal pursuits were the main abnormality (64% of cases).19 Smooth pursuit eye movements are generated through the cerebro-ponto-cerebellar pathway. Cortical regions are considered as the generators of the pursuit movement with the pons being the final destination. The frontal lobe is implicated via the frontal eye fields (FEF), which encode and predict the pursuit trajectories.23,24 These anatomical data explain the established correlations of altered smooth pursuits with the presence of non-motor signs in general and specifically with bladder dysfunction and executive impairment. Such a combination may not be so surprising since both executive and bladder dysfunction are consistent with frontal lobe pathology.
Successful return to professional work after neglect, extinction, and spatial misperception – Three long-term case studies
Published in Neuropsychological Rehabilitation, 2021
Optokinetic Stimulation with Active Smooth Pursuit Eye Movements (OKS + Pursuit) was used with the three patients as described previously in Kerkhoff et al. (2013). Patients sat (singly) on the right side in front of a large visual display (horizontal extension: 100°, vertical extension: 70°) projected via beamer onto a white wall. Different moving patterns and velocities ranging from 5°–30° moving horizontally to the left side were used for training. The patient was instructed to make active following eye movements as far as possible to the left (contralesional) side when looking at the moving visual patterns. When the patient reached the left margin of the display, he was instructed to keep his eyes there for at least 3 seconds and then return his eyes to the right side of the display and repeat the task.