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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 -
Journal of Vision Feb 2021Our eyes are never still, but tend to "freeze" in response to stimulus onset. This effect is termed "oculomotor inhibition" (OMI); its magnitude and time course depend...
Our eyes are never still, but tend to "freeze" in response to stimulus onset. This effect is termed "oculomotor inhibition" (OMI); its magnitude and time course depend on the stimulus parameters, attention, and expectation. We previously showed that the time course and duration of microsaccade and spontaneous eye-blink inhibition provide an involuntary measure of low-level visual properties such as contrast sensitivity during fixation. We investigated whether this stimulus-dependent inhibition also occurs during smooth pursuit, for both the catch-up saccades and the pursuit itself. Observers followed a target with continuous back-and-forth horizontal motion while a Gabor patch was briefly flashed centrally with varied spatial frequency and contrast. Catch-up saccades of the size of microsaccades had a similar pattern of inhibition as microsaccades during fixation, with stronger inhibition onset and faster inhibition release for more salient stimuli. Moreover, a similar stimulus dependency of inhibition was shown for pursuit latencies and peak velocity. Additionally, microsaccade latencies at inhibition release, peak pursuit velocities, and latencies at minimum pursuit velocity were correlated with contrast sensitivity. We demonstrated the generality of OMI to smooth pursuit for both microsaccades and the pursuit itself and its close relation to the low-level processes that define saliency, such as contrast sensitivity.
Topics: Adolescent; Adult; Attention; Blinking; Contrast Sensitivity; Female; Humans; Inhibition, Psychological; Male; Oculomotor Muscles; Pursuit, Smooth; Saccades; Young Adult
PubMed: 33630026
DOI: 10.1167/jov.21.2.12 -
Vision Research Nov 2022Saccades during smooth pursuit can help bring the fovea on target, particularly in cases of low pursuit gain. Individuals with macular degeneration often suffer damage...
Saccades during smooth pursuit can help bring the fovea on target, particularly in cases of low pursuit gain. Individuals with macular degeneration often suffer damage to the central retina including the fovea, which impacts oculomotor function such as fixation, saccadic and smooth pursuit eye movements. We hypothesized that these oculomotor changes in macular degeneration (MD) would make saccades less appropriately directed (even if more numerous). To investigate saccades during pursuit in MD, we conducted a quantitative analysis of smooth pursuit eye movement data from a prior study, Vision Research 141 (2017) 181-190. Here we examined saccade frequency, magnitude, and direction across viewing conditions for MD and control participants during pursuit of a target moving in a modified step-ramp paradigm. Individuals with MD had more variability in saccade directions that included directions orthogonal to the target trajectory. PRL eccentricity significantly correlated with increases in saccades in non-target directions during smooth pursuit. These results suggest that a large number of saccades during pursuit in MD participants are unlikely to be catch-up saccades that serve to keep the eye on the target.
Topics: Eye Movements; Humans; Macular Degeneration; Photic Stimulation; Pursuit, Smooth; Saccades
PubMed: 35870286
DOI: 10.1016/j.visres.2022.108102 -
Journal of Neurophysiology Mar 2021Smooth pursuit eye movements and visual motion perception rely on the integration of current sensory signals with past experience. Experience shapes our expectation of...
Smooth pursuit eye movements and visual motion perception rely on the integration of current sensory signals with past experience. Experience shapes our expectation of current visual events and can drive eye movement responses made in anticipation of a target, such as anticipatory pursuit. Previous research revealed consistent effects of expectation on anticipatory pursuit-eye movements follow the expected target direction or speed-and contrasting effects on motion perception, but most studies considered either eye movement or perceptual responses. The current study directly compared effects of direction expectation on perception and anticipatory pursuit within the same direction discrimination task to investigate whether both types of responses are affected similarly or differently. Observers ( = 10) viewed high-coherence random-dot kinematograms (RDKs) moving rightward and leftward with a probability of 50%, 70%, or 90% in a given block of trials to build up an expectation of motion direction. They were asked to judge motion direction of interleaved low-coherence RDKs (0%-15%). Perceptual judgements were compared with changes in anticipatory pursuit eye movements as a function of probability. Results show that anticipatory pursuit velocity scaled with probability and followed direction expectation (attraction bias), whereas perceptual judgments were biased opposite to direction expectation (repulsion bias). Control experiments suggest that the repulsion bias in perception was not caused by retinal slip induced by anticipatory pursuit, or by motion adaptation. We conclude that direction expectation can be processed differently for perception and anticipatory pursuit. We show that expectations about motion direction that are based on long-term trial history affect perception and anticipatory pursuit differently. Whereas anticipatory pursuit direction was coherent with the expected motion direction (attraction bias), perception was biased opposite to the expected direction (repulsion bias). These opposite biases potentially reveal different ways in which perception and action utilize prior information and support the idea of different information processing for perception and pursuit.
Topics: Adult; Anticipation, Psychological; Eye Movements; Female; Humans; Male; Motion Perception; Motivation; Photic Stimulation; Pursuit, Smooth; Young Adult
PubMed: 33534656
DOI: 10.1152/jn.00630.2020 -
Journal of Neurophysiology Jul 2020Macular degeneration (MD) often leads to the loss of the fovea and surrounding central visual field. This type of visual loss is very common and can present particular...
Macular degeneration (MD) often leads to the loss of the fovea and surrounding central visual field. This type of visual loss is very common and can present particular challenges for oculomotor tasks that may rely on the fovea. For certain tasks, individuals develop a new, eccentric fixational locus. Our previous work has shown that smooth pursuit is impaired in MD. However, extent of retinal lesion size and eccentricity of fixation do not directly contribute to changes in smooth pursuit gain. Oculomotor limitations due to eccentric eye position in the orbit may be another culprit. Here we test the hypothesis that deficits in smooth pursuit in MD would be reduced under head-unrestrained conditions. To that end, we examined eye, head, and gaze movements in eight individuals with MD and seven age-matched controls in response to a step-ramp pursuit stimulus. We found that despite variability across participants, both groups had similar smooth pursuit head movements ( = 0.76), while both had significantly higher pursuit gains in the head-restrained condition ( < 0.0001), suggesting that in older populations, head movements may lead to a decrease in pursuit gain. Furthermore, we did not find a correlation between eccentricity of fixation and amount of head displacement during the trial ( = 0.25), suggesting that eccentric eye position does not lead to higher reliance on head movements in smooth pursuit. Our finding that individuals with MD have lower pursuit gains, despite similar head movements as controls, suggests a difference in how MD affects mechanisms underlying eye versus head movements in smooth pursuit. This article is the first to look at eye and head movements in observers with macular degeneration. It is the first to show that in older individuals, regardless of central field defect, freedom of head movement may reduce pursuit gain. Despite oculomotor limitations due to eccentric fixation, individuals with macular degeneration do not rely on head movements more than age-matched controls, with both groups having a similarly heterogenous eye and head movement strategy for pursuit.
Topics: Aged; Aged, 80 and over; Aging; Female; Fixation, Ocular; Head Movements; Humans; Macular Degeneration; Male; Middle Aged; Pursuit, Smooth
PubMed: 32519572
DOI: 10.1152/jn.00001.2020 -
PloS One 2022Human smooth pursuit eye movements and motion perception behave similarly when observers track and judge the motion of simple objects, such as dots. But moving objects...
Human smooth pursuit eye movements and motion perception behave similarly when observers track and judge the motion of simple objects, such as dots. But moving objects in our natural environment are complex and contain internal motion. We ask how pursuit and perception integrate the motion of objects with motion that is internal to the object. Observers (n = 20) tracked a moving random-dot kinematogram with their eyes and reported the object's perceived direction. Objects moved horizontally with vertical shifts of 0, ±3, ±6, or ±9° and contained internal dots that were static or moved ±90° up/down. Results show that whereas pursuit direction was consistently biased in the direction of the internal dot motion, perceptual biases differed between observers. Interestingly, the perceptual bias was related to the magnitude of the pursuit bias (r = 0.75): perceptual and pursuit biases were directionally aligned in observers that showed a large pursuit bias, but went in opposite directions in observers with a smaller pursuit bias. Dissociations between perception and pursuit might reflect different functional demands of the two systems. Pursuit integrates all available motion signals in order to maximize the ability to monitor and collect information from the whole scene. Perception needs to recognize and classify visual information, thus segregating the target from its context. Ambiguity in whether internal motion is part of the scene or contributes to object motion might have resulted in individual differences in perception. The perception-pursuit correlation suggests shared early-stage motion processing or perception-pursuit interactions.
Topics: Bias; Environment; Humans; Motion; Motion Perception; Pursuit, Smooth
PubMed: 36174036
DOI: 10.1371/journal.pone.0275324 -
Vision Research Dec 2017Macular degeneration results in heterogeneous central field loss (CFL) and often has asymmetrical effects in the two eyes. As such, it is not clear to what degree the...
Macular degeneration results in heterogeneous central field loss (CFL) and often has asymmetrical effects in the two eyes. As such, it is not clear to what degree the movements of the two eyes are coordinated. To address this issue, we examined smooth pursuit quantitatively in CFL participants during binocular viewing and compared it to the monocular viewing case. We also examined coordination of the two eyes during smooth pursuit and how this coordination was affected by interocular ratios of acuity and contrast, as well as CFL-specific interocular differences, such as scotoma sizes and degree of binocular overlap. We hypothesized that the coordination of eye movements would depend on the binocularity of the two eyes. To test our hypotheses, we used a modified step-ramp paradigm, and measured pursuit in both eyes while viewing was binocular, or monocular with the dominant or non-dominant eye. Data for CFL participants and age-matched controls were examined at the group, within-group, and individual levels. We found that CFL participants had a broader range of smooth pursuit gains and a significantly lower correlation between the two eyes, as compared to controls. Across both CFL and control groups, smooth pursuit gain and correlation between the eyes are best predicted by the ratio of contrast sensitivity between the eyes. For the subgroup of participants with measurable stereopsis, both smooth pursuit gain and correlation are best predicted by stereoacuity. Therefore, our results suggest that coordination between the eyes during smooth pursuit depends on binocular cooperation between the eyes.
Topics: Aged; Aged, 80 and over; Case-Control Studies; Contrast Sensitivity; Depth Perception; Female; Humans; Macular Degeneration; Male; Middle Aged; Pursuit, Smooth; Scotoma; Vision, Binocular; Vision, Monocular
PubMed: 28057580
DOI: 10.1016/j.visres.2016.12.013 -
Eye (London, England) Feb 2015Eye movements are a source of valuable information to both clinicians and scientists as abnormalities of them frequently act as clues to the localization of a disease... (Review)
Review
Eye movements are a source of valuable information to both clinicians and scientists as abnormalities of them frequently act as clues to the localization of a disease process. Classically, they are divided into two main types: those that hold the gaze, keeping images steady on the retina (vestibulo-ocular and optokinetic reflexes) and those that shift gaze and redirect the line of sight to a new object of interest (saccades, vergence, and smooth pursuit). Here we will review some of the major ocular motor abnormalities present in neurodegenerative disorders.
Topics: Convergence, Ocular; Humans; Neurodegenerative Diseases; Nystagmus, Optokinetic; Ocular Motility Disorders; Pursuit, Smooth; Reflex, Vestibulo-Ocular; Saccades
PubMed: 25412716
DOI: 10.1038/eye.2014.276 -
NeuroImage Aug 2020Most fMRI studies investigating smooth pursuit (SP) related brain activity have used simple synthetic stimuli such as a sinusoidally moving dot. However, real-life...
Most fMRI studies investigating smooth pursuit (SP) related brain activity have used simple synthetic stimuli such as a sinusoidally moving dot. However, real-life situations are much more complex and SP does not occur in isolation but within sequences of saccades and fixations. This raises the question whether the same brain networks for SP that have been identified under laboratory conditions are activated when following moving objects in a movie. Here, we used the publicly available studyforrest data set that provides eye movement recordings along with 3 T fMRI recordings from 15 subjects while watching the Hollywood movie "Forrest Gump". All three major eye movement events, namely fixations, saccades, and smooth pursuit, were detected with a state-of-the-art algorithm. In our analysis, smooth pursuit (SP) was the eye movement of interest, while saccades were acting as the steady state of viewing behaviour due to their lower variability. For the fMRI analysis we used an event-related design modelling saccades and SP as regressors initially. Because of the interdependency of SP and content motion, we then added a new low-level content motion regressor to separate brain activations from these two sources. We identified higher BOLD-responses during SP than saccades bilaterally in MT+/V5, in middle cingulate extending to precuneus, and in the right temporoparietal junction. When the motion regressor was added, SP showed higher BOLD-response relative to saccades bilaterally in the cortex lining the superior temporal sulcus, precuneus, and supplementary eye field, presumably due to a confounding effect of background motion. Only parts of V2 showed higher activation during saccades in comparison to SP. Taken together, our approach should be regarded as proof of principle for deciphering brain activity related to SP, which is one of the most prominent eye movements besides saccades, in complex dynamic naturalistic situations.
Topics: Algorithms; Brain; Female; Humans; Magnetic Resonance Imaging; Male; Motion Perception; Motion Pictures; Photic Stimulation; Pursuit, Smooth; Saccades
PubMed: 31923604
DOI: 10.1016/j.neuroimage.2019.116491 -
Current Opinion in Neurobiology Aug 2015Movements are variable. Recent findings in smooth pursuit eye movements provide an explanation for motor variation in terms of the organization of the brain's... (Review)
Review
Movements are variable. Recent findings in smooth pursuit eye movements provide an explanation for motor variation in terms of the organization of the brain's sensory-motor pathways. Variation in sensory estimation is propagated through sensory-motor circuits and ultimately causes motor variation. The sensory origin of motor variation creates trial-by-trial correlations among the responses of neurons at each level of the sensory motor circuit, and between neural and behavioral responses. We suggest that motor variation is a compromise between multiple competing constraints. The brain strives for motor behavior that is 'good enough' in the face of constraints that tend to promote variation.
Topics: Action Potentials; Animals; Humans; Models, Neurological; Motion Perception; Movement; Neurons; Pursuit, Smooth
PubMed: 25845626
DOI: 10.1016/j.conb.2015.03.008