Posts Tagged eye movements

[Abstract] Eye Movements Interfere With Limb Motor Control in Stroke Survivors

Background. Humans use voluntary eye movements to actively gather visual information during many activities of daily living, such as driving, walking, and preparing meals. Most stroke survivors have difficulties performing these functional motor tasks, and we recently demonstrated that stroke survivors who require many saccades (rapid eye movements) to plan reaching movements exhibit poor motor performance. However, the nature of this relationship remains unclear.

Objective. Here we investigate if saccades interfere with speed and smoothness of reaching movements in stroke survivors, and if excessive saccades are associated with difficulties performing functional tasks.

Methods. We used a robotic device and eye tracking to examine reaching and saccades in stroke survivors and age-matched controls who performed the Trail Making Test, a visuomotor task that uses organized patterns of saccades to plan reaching movements. We also used the Stroke Impact Scale to examine difficulties performing functional tasks.

Results. Compared with controls, stroke survivors made many saccades during ongoing reaching movements, and most of these saccades closely preceded transient decreases in reaching speed. We also found that the number of saccades that stroke survivors made during ongoing reaching movements was strongly associated with slower reaching speed, decreased reaching smoothness, and greater difficulty performing functional tasks.

Conclusions. Our findings indicate that poststroke interference between eye and limb movements may contribute to difficulties performing functional tasks. This suggests that interventions aimed at treating impaired organization of eye movements may improve functional recovery after stroke.

  

via Eye Movements Interfere With Limb Motor Control in Stroke Survivors – Tarkeshwar Singh, Christopher M. Perry, Stacy L. Fritz, Julius Fridriksson, Troy M. Herter, 2018

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[Abstract] Eye Movements Interfere With Limb Motor Control in Stroke Survivors

Background. Humans use voluntary eye movements to actively gather visual information during many activities of daily living, such as driving, walking, and preparing meals. Most stroke survivors have difficulties performing these functional motor tasks, and we recently demonstrated that stroke survivors who require many saccades (rapid eye movements) to plan reaching movements exhibit poor motor performance. However, the nature of this relationship remains unclear.

Objective. Here we investigate if saccades interfere with speed and smoothness of reaching movements in stroke survivors, and if excessive saccades are associated with difficulties performing functional tasks.

Methods. We used a robotic device and eye tracking to examine reaching and saccades in stroke survivors and age-matched controls who performed the Trail Making Test, a visuomotor task that uses organized patterns of saccades to plan reaching movements. We also used the Stroke Impact Scale to examine difficulties performing functional tasks.

Results. Compared with controls, stroke survivors made many saccades during ongoing reaching movements, and most of these saccades closely preceded transient decreases in reaching speed. We also found that the number of saccades that stroke survivors made during ongoing reaching movements was strongly associated with slower reaching speed, decreased reaching smoothness, and greater difficulty performing functional tasks.

Conclusions. Our findings indicate that poststroke interference between eye and limb movements may contribute to difficulties performing functional tasks. This suggests that interventions aimed at treating impaired organization of eye movements may improve functional recovery after stroke.

via Eye Movements Interfere With Limb Motor Control in Stroke Survivors – Tarkeshwar Singh, Christopher M. Perry, Stacy L. Fritz, Julius Fridriksson, Troy M. Herter, 2018

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[Abstract] Review of rehabilitation and habilitation strategies for children and young people with homonymous visual field loss caused by cerebral vision impairment

 

Abstract

Partial and homonymous visual field loss (HVFL) is a common consequence of post-chiasmatic injury to the primary visual pathway or injury to the primary visual cortex. Different approaches to rehabilitation have been reported for older adults with HVFL and there is evidence to support the use of compensatory training over other proposed therapies. We reviewed the literature to investigate the current state of the art of rehabilitation and habilitation strategies for children and young people with HVFL, and whether there is enough evidence to support the use of these strategies in the paediatric population. We have provided an overview of the existing literature on children and young people with HVFL, a brief overview of rehabilitation strategies for adults with HVFL, and evidence on whether these different interventions have been applied with children and young people effectively. We found that there have been very few studies to investigate these strategies with children and young people, and the quality of evidence is currently low. New research is required to evaluate which strategies are effective for children and young people with HVFL and whether new strategies need to be developed.

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Source: Review of rehabilitation and habilitation strategies for children and young people with homonymous visual field loss caused by cerebral vision impairment – The Lincoln Repository

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[Abstract] Spontaneous ocular positioning during visual imagery in patients with hemianopia and/or hemineglect

Highlights

We recorded gaze positions during visual imagery in patients with HLH or neglect.

Spatially consistent mental imagery was possible in all hemianopic patients.

Neglect patients had a representational disability for the left side of the map.

Hemianopic patients positioned their gaze contralesionally-Neglect patients positioned their gaze ipsilesionally.

Occipital and fronto-parietal cortices are involved in visual imagery.


Abstract

Spontaneous eye movements during imagery are not random and can be used to study and reveal mental visualization processes (Fourtassi et al., 2013; Johansson et al. 2006). For example, we previously showed that during memory recall of French towns via imagery healthy individuals looks straight ahead when recalling Paris and their subsequent gaze positions are significantly correlated with the real GPS coordinates of the recalled towns. This correlation suggests that memory retrieval is done via depictive representations as it is never found when the towns are recalled using verbal fluency. In the present paper we added to this finding by showing that the mental image is spontaneously centered on the head or body midline.

In order to investigate the capacities of visual imagery in patients, and by extension, the role of primary visual cortex and fronto-parietal cortex in spatial visual imagery, we recorded gaze positions during memory recall of French towns in an imagery task, a non-imagery task (verbal fluency), and a visually-guided task in five patients with left or right hemianopia and in four patients with hemineglect (two with left hemianopia and two without).

The correlation between gaze position and real GPS coordinates of the recalled towns was significant in all hemianopic patients, but in patients with hemineglect this was only the case for towns located on the right half of the map of France. This suggests hemianopic patients can perform spatially consistent mental imagery despite direct or indirect unilateral lesions of the primary visual cortex. In contrast, the left-sided towns recalled by hemineglect patients, revealed that they have some spatial inconsistency or representational difficulty.

Hemianopic patients positioned and maintained their gaze in their contralesional hemispace, suggesting that their mental map was not centered on their head or body midline. This contralesional gaze positioning appeared to be a general compensation strategy and was not observed in patients with neglect (with or without hemianopia). Instead, neglect patients positioned their gaze in their ipsilesional hemispace and only when performing the visual imagery task.

These findings are discussed in the context of the role of occipital and fronto-parietal cortices in the neuroanatomical model of visual imagery developed by Kosslyn et al. (2006).

 

Source: Spontaneous ocular positioning during visual imagery in patients with hemianopia and/or hemineglect

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[ARTICLE] Driving with Homonymous Visual Field Defects: Driving Performance and Compensatory Gaze Movements – Full Text PDF

Aim of this pilot study was to assess the driving performance and its relationship to the visual search behavior, i.e., eye and head movements, of patients with homonymous visual field defects (HVFDs) in comparison to healthy-sighted subjects during a simulated driving test.

Eight HVFD patients and six healthy-sighted ageand gender-matched control subjects underwent a 40-minute driving test with nine hazardous situations. Eye and head movements were recorded during the drive.

Four out of eight patients passed the driving test and showed a driving performance similar to that of the control group. One control group subject failed the test. Patients who passed the test showed an increased number of head and eye movements. Patients who failed the test showed a rightwards-bias in average lane position, probably in an attempt to maximize the safety margin to oncoming traffic.

Our study supports the hypothesis that a considerable subgroup of subjects with HVFDs show a safe driving behavior, because they adapt their viewing behavior by increased visual scanning.

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[ARTICLE] Eye movements during saccadic and fixation tasks in patients with hemianopia – Full Text PDF

ABSTRACT

Objectives The aim was to quantify oculomotor performance in hemianopic patients and in healthy controls during saccadic and fixation tasks, and to detect potential spontaneous adaptive mechanisms in the patients.

Methods Eye movements were recorded in 33 hemianopic patients (15 right, 18 left, disease duration 0.2-29 years) and 14 healthy subjects by Scanning Laser Ophthalmoscope allowing determination of the absolute fovea position relative to the stimulus without calibration. Landing accuracy of saccades was determined for 5° saccades, indicated by the number of dysmetric saccades (DS), and fixation stability (FS) after landing. Furthermore, during continuous fixation of a central cross, FS and distribution of fixational eye movements (FEM) were measured. Size of macular sparing was determined using custom microperimetry software (stimulus grid 0.5°).

Results Landing accuracy was decreased, indicated by significantly more DS (hypo- and hypermetric) to the blind side compared with the seeing side. Their number was more increased in macular sparing <4°. DS were not correlated with age and disease duration.. FS after landing was lower after saccades to the blind side. Distribution of FEM during continuous fixation was asymmetrically shifted to the blind side, especially in macular sparing <4°.

Conclusions Number of DS was not correlated with disease duration indicating insufficient spontaneous long-term adaptation. Increased number of DS and decreased FS after landing in patients with small or absent macular sparing stresses the importance of intact parafoveal vision. Asymmetric FEM during continuous fixation indicate an advantageous adaptive mechanism to shift the visual field border towards the hemianopic side.

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[Editorial] Neural bases of binocular vision and coordination and their implications in visual training programs

Opening

To see or not to see? That is the question of this research topic. How do human beings see not with their eyes but with their brain, which lies in a moving body, itself evolving in a continuously changing environment? What and how do humans see in the context of a particular task at a given moment? How do humans cease to see after some damage in the brain or neurofunctional disorder? And how may the basic science of eye movements and vision help to develop efficient visual training programs?

The present research topic, entitled Neural bases of binocular vision and coordination and their implications in visual training programs, aims at putting forward our knowledge of the neural underpinnings of vision in its motor, sensory, cognitive, emotional and vegetative expressions. It does not target an exhaustive collection of what we know in the field of visual neurosciences. For that purpose, the reader may refer to the volume sets by Chalupa and Werner (2003). Rather, this research topic focuses on the latest findings on the neural aspects of eye movements and visual perception that directly help to understand and improve visual training programs in pathological conditions. Such disorders follow damages of the cerebral visual pathways (e.g., hemianopia) or refer to syndromes hitherto believed to be peripheral but in which neurophysiology and brain imaging are uncovering neural correlates or causes (e.g., amblyopia).

The research topic is divided into three parts respectively dedicated to eye movements, visual perception, and visual training programs, each having six chapters, and starts with an overview. In the introductory chapter, Coubard, Urbanski, Bourlon and Gaumet (2014) remind the reader of the importance of action in visual processing before describing the cascade of physiological mechanisms underlying eye movements, followed by a description of the five main neurovisual systems. After an overview of pathological conditions causing not eye but brain blindness – also called neurovisual disorders – the authors end by describing the disciplines of visual rehabilitation.

Continue —>  Frontiers | Editorial: Neural bases of binocular vision and coordination and their implications in visual training programs | Frontiers in Integrative Neuroscience.

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[ARTICLE] Translational Vision Science and Technology – Homonymous Visual Field Loss and Its Impact on Visual Exploration: A Supermarket Study – Full Text

Conclusion

…Homonymous VFDs may critically interfere with quality of life. In a special-offer supermarket search task, we investigated the performance of 10 patients with homonymous VFDs and 10 control subjects. A considerable number of patients completed the task successfully despite the visual impairment and performed indistinguishably from the control subjects. On average, homonymous visual-field loss was associated with longer search time. Analysis of eye-tracking data revealed that efficient visual search strategy may help some patients to compensate for their visual impairment. For the present supermarket search task, effective visual exploration included longer glancing toward the peripheral visual field…

via Translational Vision Science and Technology – Homonymous Visual Field Loss and Its Impact on Visual Exploration: A Supermarket Study.

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