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Clinical Neurophysiology : Official... Jun 2011
Topics: Attention; Brain; Fixation, Ocular; Humans; User-Computer Interface
PubMed: 21183404
DOI: 10.1016/j.clinph.2010.11.014 -
Vision Research Sep 2014Humans display image-independent viewing biases when inspecting complex scenes. One of the strongest such bias is the central tendency in scene viewing: observers favour...
Humans display image-independent viewing biases when inspecting complex scenes. One of the strongest such bias is the central tendency in scene viewing: observers favour making fixations towards the centre of an image, irrespective of its content. Characterising these biases accurately is important for three reasons: (1) they provide a necessary baseline for quantifying the association between visual features in scenes and fixation selection; (2) they provide a benchmark for evaluating models of fixation behaviour when viewing scenes; and (3) they can be included as a component of generative models of eye guidance. In the present study we compare four commonly used approaches to describing image-independent biases and report their ability to describe observed data and correctly classify fixations across 10 eye movement datasets. We propose an anisotropic Gaussian function that can serve as an effective and appropriate baseline for describing image-independent biases without the need to fit functions to individual datasets or subjects.
Topics: Attention; Eye Movements; Fixation, Ocular; Humans; Models, Theoretical; Visual Perception
PubMed: 25080387
DOI: 10.1016/j.visres.2014.06.016 -
Journal of Neurophysiology May 1998Visual fixation, the act of maintaining the eyes directed toward a location of interest, is a highly skilled behavior necessary for high-level vision in primates. In... (Comparative Study)
Comparative Study
Visual fixation, the act of maintaining the eyes directed toward a location of interest, is a highly skilled behavior necessary for high-level vision in primates. In spite of its significance, visual fixation is not well understood; it is not even clear what attributes of the visual input are used to control fixation. Here we show, in four Macaca fascicularis monkeys, that the position the eyes assume during fixation depends on the luminance of the background. Dark background yields fixation positions that are shifted upward with respect to the fixation positions obtained with a dimly illuminated, featureless background. This phenomenon was observed previously in a nutshell by Snodderly; here first we rigorously establish its existence by testing proper controls. We then study the properties of this upshift of the fixation position. We show that, although the size of the upshift varies between monkeys, for all monkeys the upshift is larger than the radius of the fovea. Hence, if the background is dim, the eyes are positioned during fixation so that the target does not fall on the fovea. The size of the upshift remains almost unchanged while the eyes fixate at different orbital positions; thus the upshift is not caused by orbital mechanics. The upshift clearly is present even at the first days of training, but with additional training in fixation with dark background, the upshift increases in size. The upshift rotates with the head. The upshift increases gradually with decreasing levels of background luminosity. Luminosity, not visual contrast, is indeed the primary variable determining the size of the upshift. The contribution of a unit area of the retina to the upshift decreases as inverse square root of distance from the target; therefore, it is the perifoveal region of the retina that mostly contributes to the upshift, while the far periphery has little influence. The upshift can be induced or be canceled in the midst of a fixation by changing the background illumination; hence, the upshift is indeed an attribute of the fixation control system. Finally, the fixation-upshift studied here is different from a previously reported upshift of the endpoints of memory-guided saccades with respect to their target locations. These two types of upshift add up to each other. In discussing the function of the upshift, we note a possible morphological analogue with the retinal rod distribution. The upshift moves the line of gaze to a point intermediate between the fovea and the "dorsal rod peak." The upshift thus may improve visual acuity in scotopic conditions. The brain structure in which the upshift is generated must be involved in both ocular control and visual sensation. We consider several possibilities, of which we regard as the most likely the cerebellum and superior colliculus.
Topics: Animals; Contrast Sensitivity; Darkness; Eye Movements; Fixation, Ocular; Head; Lighting; Macaca fascicularis; Posture
PubMed: 9582243
DOI: 10.1152/jn.1998.79.5.2766 -
Mind over muscle: the role of gaze control, spatial cognition, and the quiet eye in motor expertise.Cognitive Processing Aug 2011In the course of all motor behavior, the brain is limited in how much information it can process and act upon at a time. Performers must constantly decide where to look,...
In the course of all motor behavior, the brain is limited in how much information it can process and act upon at a time. Performers must constantly decide where to look, what to attend to, and how to time fixated information with precisely controlled actions. The gaze can be directed to only one location at a time and information central to success must be selected from spatially complex environments, most often under severe time constraints. The coordination of these processes is explored in this Special issue in a number of motor tasks, including golf, soccer, law enforcement, and ballet. The papers describe the visual information and quiet eye characteristics that underlie the ability to make decisions under complex task conditions and the relationship between control of the gaze and task outcomes. With the attainment of motor expertise, measureable changes occur within the gaze, cognitive, and neural systems that are useful in training, rehabilitation, and the treatment of motor deficits.
Topics: Cognition; Fixation, Ocular; Humans; Motor Skills; Space Perception
PubMed: 21656242
DOI: 10.1007/s10339-011-0411-2 -
Philosophical Transactions of the Royal... Apr 2015In his Bakerian Lecture paper of 1801, Thomas Young provided the best account up to that time of the eye's optical system, including refraction by the cornea and the... (Review)
Review
In his Bakerian Lecture paper of 1801, Thomas Young provided the best account up to that time of the eye's optical system, including refraction by the cornea and the surfaces of the lens. He built a device, an optometer, for determining the eye's state of focus, making it possible to prescribe appropriate correction lenses. His main contribution, however, was to show that accommodation, the eye's focusing mechanism, was not the result of changes to the curvature of the cornea, nor to the length of the eye, but was due entirely to changes in the shape of the lens, which he described with impressive accuracy. He was wrong, however, in believing that the reason the lens bulges when focusing on near objects was because it behaved as a contracting muscle. Half a century later, Helmholtz showed that the lens bulges not by its own contraction, but when it is relaxed as a result of contraction of newly discovered circular muscles in the ciliary body. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.
Topics: Fixation, Ocular; History, 19th Century; Humans; Lens, Crystalline; Ocular Physiological Phenomena; Optometry
PubMed: 25750232
DOI: 10.1098/rstb.2014.0308 -
Vision Research Feb 1999Turning off a fixation point prior to or coincident with the appearance of a visual target reduces the latency of saccades to that target. We investigated this 'gap...
Turning off a fixation point prior to or coincident with the appearance of a visual target reduces the latency of saccades to that target. We investigated this 'gap effect' when subjects fixated a central point or the center of a square formed by four points that were 4, 2 or 1 degree eccentric from the square's center. The fixation anchor vanished 200 ms prior to the appearance of a saccadic target in a Gap condition, coincident with the target's appearance in a 0-Gap condition, or remained on in an Overlap condition. Saccadic reaction time was reduced in the Gap relative to 0-Gap condition irrespective of the type of fixation anchor. However, saccadic reaction time was not reduced in the 0-Gap relative to Overlap condition when the points forming the square had eccentricities of 2 or 4 degrees. Results are interpreted in terms of a partial mediation of the gap effect by fixation cells in the rostral pole of the superior colliculus.
Topics: Analysis of Variance; Fixation, Ocular; Humans; Reaction Time; Saccades
PubMed: 10341969
DOI: 10.1016/s0042-6989(98)00164-3 -
Movement Disorders : Official Journal... Oct 2011
Topics: Female; Fixation, Ocular; Humans; Male; Movement; Orientation; Parkinsonian Disorders; Posture; Psychomotor Disorders
PubMed: 22021156
DOI: 10.1002/mds.23980 -
Topics in Cognitive Science Jan 2019Decades of developmental research have capitalized on the fact that infants are surprised (i.e., look longer) at some events but not others. Differences in looking time... (Review)
Review
Decades of developmental research have capitalized on the fact that infants are surprised (i.e., look longer) at some events but not others. Differences in looking time have been considered to be a reflection of perceptual discrimination, or a reaction toward witnessing a violation of prior expectations. Here, we provide an overview of a new perspective on infant surprise that examines the underlying cognitive processes that drive this response. We suggest that looking time may reflect sophisticated statistical inference, and we review empirical evidence and computational modeling results from several recent studies to support this conjecture (Kidd, Piantadosi, & Aslin, ; Piantadosi, Kidd, & Aslin, ; Sim, Griffiths, & Xu, ; Sim & Xu, ; Téglás et al., ). We also discuss how our view relates to other new developmental research on surprise and learning (Stahl & Feigenson, , ) and outline some suggestions for future research.
Topics: Child Development; Cognition; Fixation, Ocular; Humans; Infant; Thinking; Visual Perception
PubMed: 30411516
DOI: 10.1111/tops.12393 -
Bulletin de La Societe Belge... 1989
Review
Topics: Convergence, Ocular; Eye Movements; Fixation, Ocular; Humans; Nystagmus, Pathologic
PubMed: 2486106
DOI: No ID Found -
Optics Letters May 2024Point scanning retinal imaging modalities, including confocal scanning light ophthalmoscopy (cSLO) and optical coherence tomography, suffer from fixational motion...
Point scanning retinal imaging modalities, including confocal scanning light ophthalmoscopy (cSLO) and optical coherence tomography, suffer from fixational motion artifacts. Fixation targets, though effective at reducing eye motion, are infeasible in some applications (e.g., handheld devices) due to their bulk and complexity. Here, we report on a cSLO device that scans the retina in a spiral pattern under pseudo-visible illumination, thus collecting image data while simultaneously projecting, into the subject's vision, the image of a bullseye, which acts as a virtual fixation target. An imaging study of 14 young adult volunteers was conducted to compare the fixational performance of this technique to that of raster scanning, with and without a discrete inline fixation target. Image registration was used to quantify subject eye motion; a strip-wise registration method was used for raster scans, and a novel, to the best of our knowledge, ring-based method was used for spiral scans. Results indicate a statistically significant reduction in eye motion by the use of spiral scanning as compared to raster scanning without a fixation target.
Topics: Humans; Retina; Fixation, Ocular; Ophthalmoscopy; Adult; Young Adult; Eye Movements
PubMed: 38691751
DOI: 10.1364/OL.517088