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Jian-Fang Zhou, Wu-Jie Yuan, Zhao Zhou
Microsaccades are involuntary and very small eye movements during fixation. Recently, the microsaccade-related neural dynamics have been extensively investigated both in experiments and by constructing neural network models. Experimentally, microsaccades also exhibit many behavioral properties. It's well known that the behavior properties imply the underlying neural dynamical mechanisms, and so are determined by neural dynamics. The behavioral properties resulted from neural responses to microsaccades, however, are not yet understood and are rarely studied theoretically...
October 14, 2016: Scientific Reports
Tyler R Peel, Ziad M Hafed, Suryadeep Dash, Stephen G Lomber, Brian D Corneil
Microsaccades aid vision by helping to strategically sample visual scenes. Despite the importance of these small eye movements, no cortical area has ever been implicated in their generation. Here, we used unilateral and bilateral reversible inactivation of the frontal eye fields (FEF) to identify a cortical drive for microsaccades. Unexpectedly, FEF inactivation altered microsaccade metrics and kinematics. Such inactivation also impaired microsaccade deployment following peripheral cue onset, regardless of cue side or inactivation configuration...
August 2016: PLoS Biology
Pengxiao Zang, Gangjun Liu, Miao Zhang, Changlei Dongye, Jie Wang, Alex D Pechauer, Thomas S Hwang, David J Wilson, David Huang, Dengwang Li, Yali Jia
We propose an innovative registration method to correct motion artifacts for wide-field optical coherence tomography angiography (OCTA) acquired by ultrahigh-speed swept-source OCT (>200 kHz A-scan rate). Considering that the number of A-scans along the fast axis is much higher than the number of positions along slow axis in the wide-field OCTA scan, a non-orthogonal scheme is introduced. Two en face angiograms in the vertical priority (2 y-fast) are divided into microsaccade-free parallel strips. A gross registration based on large vessels and a fine registration based on small vessels are sequentially applied to register parallel strips into a composite image...
July 1, 2016: Biomedical Optics Express
Moritz Köster
No abstract text is available yet for this article.
July 27, 2016: Proceedings. Biological Sciences
Alex L White, Martin Rolfs
Saccadic eye movements occur frequently even during attempted fixation, but they halt momentarily when a new stimulus appears. Here we demonstrate that this rapid, involuntary "oculomotor freezing" reflex is yoked to fluctuations in explicit visual perception. Human observers reported the presence or absence of a brief visual stimulus while we recorded microsaccades, small spontaneous eye movements. We found that microsaccades were reflexively inhibited if and only if the observer reported seeing the stimulus, even when none was present...
July 6, 2016: Journal of Neurophysiology
Sven Ohl, Reinhold Kliegl
Saccadic eye movements are frequently followed by smaller secondary saccades which are generally assumed to correct for the error in primary saccade landing position. However, secondary saccades can also occur after accurate primary saccades and they are often as small as microsaccades, therefore raising the need to further scrutinize the processes involved in secondary saccade generation. Following up a previous study, we analyzed secondary saccades using rate analysis which allows us to quantify experimental effects as shifts in distributions, therefore going beyond comparisons of mean differences...
July 2016: Vision Research
Alessandro Piras, Milena Raffi, Michela Persiani, Monica Perazzolo, Salvatore Squatrito
The present study shows the relationship between microsaccades and heading perception. Recent research demonstrates that microsaccades during fixation are necessary to overcome loss of vision due to continuous stimulation of the retinal receptors, even at the potential cost of a decrease in visual acuity. The goal of oculomotor fixational mechanisms might be not retinal stabilization, but controlled image motion adjusted to be optimal for visual processing. Thus, patterns of microsaccades may be exploited to help to understand the oculomotor system, aspects of visual perception, and the dynamics of visual attention...
October 1, 2016: Behavioural Brain Research
Zongpeng Sun, Marc Junker, Peter W Dicke, Peter Thier
Recent studies have suggested that microsaccades, the small amplitude saccades made during fixation, are precisely controlled. Two lines of evidence suggest that the cerebellum plays a key role not only in improving the accuracy of macrosaccades but also of microsaccades. First, lesions of the fastigial oculomotor regions (FOR) cause horizontal dysmetria of both micro- and macrosaccades. Secondly, our previous work on Purkinje cell simple spikes in the oculomotor vermis (OV) has established qualitatively similar response preferences for these two groups of saccades...
June 3, 2016: European Journal of Neuroscience
Uday K Jagadisan, Neeraj J Gandhi
UNLABELLED: Executive control of voluntary movements is a hallmark of the mammalian brain. In the gaze-control network, this function is thought to be mediated by a critical balance between neurons responsible for generating movements and those responsible for fixating or suppressing movements, but the nature of this balance between the relevant elements-saccade-generating and fixation-related neurons-remains unclear. Specifically, it has been debated whether the two functions are necessarily coupled (i...
June 1, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Wu-Jie Yuan, Jian-Fang Zhou, Changsong Zhou
Microsaccades are very small eye movements during fixation. Experimentally, they have been found to play an important role in visual information processing. However, neural responses induced by microsaccades are not yet well understood and are rarely studied theoretically. Here we propose a network model with a cascading adaptation including both retinal adaptation and short-term depression (STD) at thalamocortical synapses. In the neural network model, we compare the microsaccade-induced neural responses in the presence of STD and those without STD...
April 2016: Physical Review. E
Yoram S Bonneh, Yael Adini, Uri Polat
Spontaneous eyeblinks are known to serve important physiological functions, and recent evidence shows that they are also linked to cognitive processes. It is yet unclear whether this link reflects a crude rate modulation or, alternatively, an automatic and precise process, tightly linked to the low-level properties of sensory stimuli. We have recently reported (Y. S. Bonneh, Adini, & Polat, 2015) that, for microsaccades, the onset and release from inhibition in response to transient stimuli depend systematically on the low-level stimulus parameters...
May 1, 2016: Journal of Vision
Timothée Masquelier, Geoffrey Portelli, Pierre Kornprobst
It is now reasonably well established that microsaccades (MS) enhance visual perception, although the underlying neuronal mechanisms are unclear. Here, using numerical simulations, we show that MSs enable efficient synchrony-based coding among the primate retinal ganglion cells (RGC). First, using a jerking contrast edge as stimulus, we demonstrate a qualitative change in the RGC responses: synchronous firing, with a precision in the 10 ms range, only occurs at high speed and high contrast. MSs appear to be sufficiently fast to be able reach the synchronous regime...
2016: Scientific Reports
Gabriel Coscas, Marco Lupidi, Florence Coscas
Optical coherence tomography angiography (OCT-A) is a promising new method for visualizing the retinal vasculature and choroidal vascular layers in the macular area and provides depth-resolved functional information on blood flow in these vessels. OCT-A is based on the concept that in a static eye the only moving structure in the fundus of the eye is blood flowing through the vessels. Contrast is generated based on the difference between moving cells in the vasculature and the static surrounding tissue. Artifacts can arise due to scan positioning errors caused by normal ocular microsaccades...
2016: Developments in Ophthalmology
Xiaoguang Tian, Masatoshi Yoshida, Ziad M Hafed
Microsaccades exhibit systematic oscillations in direction after spatial cueing, and these oscillations correlate with facilitatory and inhibitory changes in behavioral performance in the same tasks. However, independent of cueing, facilitatory and inhibitory changes in visual sensitivity also arise pre-microsaccadically. Given such pre-microsaccadic modulation, an imperative question to ask becomes: how much of task performance in spatial cueing may be attributable to these peri-movement changes in visual sensitivity? To investigate this question, we adopted a theoretical approach...
2016: Frontiers in Systems Neuroscience
Daw-An Wu, Patrick Cavanagh
How do we know where we are looking? A frequent assumption is that the subjective experience of our direction of gaze is assigned to the location in the world that falls on our fovea. However, we find that observers can shift their subjective direction of gaze among different nonfoveal points in an afterimage. Observers were asked to look directly at different corners of a diamond-shaped afterimage. When the requested corner was 3.5° in the periphery, the observer often reported that the image moved away in the direction of the attempted gaze shift...
2016: Journal of Vision
Suzanne P McKee, Dennis M Levi, Clifton M Schor, J Anthony Movshon
We measured saccadic latencies in a large sample (total n = 459) of individuals with amblyopia or risk factors for amblyopia, e.g., strabismus or anisometropia, and normal control subjects. We presented an easily visible target randomly to the left or right, 3.5° from fixation. The interocular difference in saccadic latency is highly correlated with the interocular difference in LogMAR (Snellen) acuity-as the acuity difference increases, so does the latency difference. Strabismic and strabismic-anisometropic amblyopes have, on average, a larger difference between their eyes in LogMAR acuity than anisometropic amblyopes and thus their interocular latency difference is, on average, significantly larger than anisometropic amblyopes...
2016: Journal of Vision
Josselin Gautier, Harold E Bedell, John Siderov, Sarah J Waugh
During visual fixation, we constantly move our eyes. These microscopic eye movements are composed of tremor, drift, and microsaccades. Early studies concluded that microsaccades, like larger saccades, are binocular and conjugate, as expected from Hering's law of equal innervation. Here, we document the existence of monocular microsaccades during both fixation and a discrimination task, reporting the location of the gap in a foveal, low-contrast letter C. Monocular microsaccades differ in frequency, amplitude, and peak velocity from binocular microsaccades...
2016: Journal of Vision
Jian-Fang Zhou, Wu-Jie Yuan, Zhao Zhou, Changsong Zhou
Recently, the significant microsaccade-induced neural responses have been extensively observed in experiments. To explore the underlying mechanisms of the observed neural responses, a feedforward network model with short-term synaptic depression has been proposed [Yuan, W.-J., Dimigen, O., Sommer, W. and Zhou, C. Front. Comput. Neurosci. 7, 47 (2013)]. The depression model not only gave an explanation for microsaccades in counteracting visual fading, but also successfully reproduced several microsaccade-related features in experimental findings...
2016: Scientific Reports
Sven Ohl, Christian Wohltat, Reinhold Kliegl, Olga Pollatos, Ralf Engbert
UNLABELLED: During visual fixation, the eye generates microsaccades and slower components of fixational eye movements that are part of the visual processing strategy in humans. Here, we show that ongoing heartbeat is coupled to temporal rate variations in the generation of microsaccades. Using coregistration of eye recording and ECG in humans, we tested the hypothesis that microsaccade onsets are coupled to the relative phase of the R-R intervals in heartbeats. We observed significantly more microsaccades during the early phase after the R peak in the ECG...
January 27, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Leon Y Deouell
No abstract text is available yet for this article.
May 2016: European Journal of Neuroscience
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