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David P M Northmore
Only ray-finned fishes possess a torus longitudinalis (TL), a paired, elongated body attached to the medial margins of the optic tectum. Its granule cells project large numbers of fine fibers running laterally over adjacent tectum, synapsing excitatorily on the spiny dendrites of pyramidal cells. Sustained TL activity is evoked visuotopically by dark stimuli; TL bursting is a corollary discharge of saccadic eye movements. To suggest a function for this ancient structure, neural network models were constructed to show that: (1) pyramidal cells could form an attentional locus, selecting one out of several moving objects to track, but rapid image shifts caused by saccades disrupt tracking; (2) TL could supply both the pre-saccade position of a locus, and the shift predicted from a saccade so as to prime pyramidal dendrites at the target location, ensuring the locus stays with the attended object; (3) that the specific pattern of synaptic connections required for such predictive priming could be learned by an unsupervised rule; (4) temporal and spatial filtering of visual pattern input to TL allows learning from a complex scene...
January 3, 2017: Vision Research
Scott L Fairhall, Jens Schwarzbach, Angelika Lingnau, Martijn Gerbrand Van Koningsbruggen, David Melcher
Brain representations of visual space are predominantly eye-centred (retinotopic) yet our experience of the world is largely world-centred (spatiotopic). A long-standing question is how the brain creates continuity between these reference frames across successive eye movements (saccades). Here we use functional magnetic resonance imaging (fMRI) to address whether spatially specific repetition suppression (RS) is evident during trans-saccadic perception. We presented two successive Gabor patches (S1 and S2) in either the upper or lower visual field, left or right of fixation...
November 29, 2016: NeuroImage
Benjamin T Dunkley, Bianca Baltaretu, J Douglas Crawford
The cortical sites for the trans-saccadic storage and integration of visual object features are unknown. Here, we used a variant of fMRI-Adaptation where subjects fixated to the left or right of a briefly presented visual grating, maintained fixation or saccaded to the opposite side, then judged whether a re-presented grating had the same or different orientation. fMRI analysis revealed trans-saccadic interactions (different > same orientation) in a visual field-insensitive cluster within right supramarginal gyrus...
September 2016: Cortex; a Journal Devoted to the Study of the Nervous System and Behavior
David Souto, Karl R Gegenfurtner, Alexander C Schütz
Visual uncertainty may affect saccade adaptation in two complementary ways. First, an ideal adaptor should take into account the reliability of visual information for determining the amount of correction, predicting that increasing visual uncertainty should decrease adaptation rates. We tested this by comparing observers' direction discrimination and adaptation rates in an intra-saccadic-step paradigm. Second, clearly visible target steps may generate a slower adaptation rate since the error can be attributed to an external cause, instead of an internal change in the visuo-motor mapping that needs to be compensated...
2016: Frontiers in Human Neuroscience
Naoko Inaba, Kenji Kawano
After a saccade, most MST neurons respond to moving visual stimuli that had existed in their post-saccadic receptive fields and turned off before the saccade ("trans-saccadic memory remapping"). Neuronal responses in higher visual processing areas are known to be modulated in relation to gaze angle to represent image location in spatiotopic coordinates. In the present study, we investigated the eye position effects after saccades and found that the gaze angle modulated the visual sensitivity of MST neurons after saccades both to the actually existing visual stimuli and to the visual memory traces remapped by the saccades...
February 23, 2016: Scientific Reports
Matteo Valsecchi, Karl R Gegenfurtner
The same object produces quite distinct images in the cortical representation, depending on whether it is looked at foveally or with the periphery, yet some form of size constancy prevents us from experiencing objects inflating or deflating as we move our eyes. According to the prominent sensorimotor account of vision by O'Regan and Noë [1], we constantly learn to discount the predictable sensory effects of motor actions, such as the projection of a stimulus on a larger cortical area as it gets foveated. Although previous studies have shown that foveal and parafoveal inputs can be associated in visual memory [2, 3], trans-saccadic prediction error could in principle re-calibrate even the appearance of peripheral and foveal stimuli...
January 11, 2016: Current Biology: CB
Laurence C Jayet Bray, Sonia Bansal, Wilsaan M Joiner
Extraretinal information, such as corollary discharge (CD), is hypothesized to help compensate for saccade-induced visual input disruptions. However, support for this hypothesis is largely for one-dimensional transsaccadic visual changes, with little comprehensive information on the spatial characteristics. Here we systematically mapped the two-dimensional extent of this compensation by quantifying the insensitivity to different displacement metrics. Human subjects made saccades to targets positioned at different amplitudes (4° or 8°) and directions (rightward, oblique, or upward)...
March 2016: Journal of Neurophysiology
Jonathan Grainger, Katherine J Midgley, Phillip J Holcomb
We used a trans-saccadic priming paradigm combined with ERP recordings to track the time-course of integration of information across a prime word briefly presented at fixation and a subsequent target word presented 4 degrees to the right of fixation. Trans-saccadic repetition priming effects (Experiments 1 and 2) were compared with priming effects obtained with centrally located targets (Experiment 3). In Experiment 2, target stimuli were preceded by a 100ms forward mask at the target location, hence allowing an attention shift to the target location prior to target onset...
January 8, 2016: Neuropsychologia
Christian Wolf, Alexander C Schütz
Due to the inhomogenous visual representation across the visual field, humans use peripheral vision to select objects of interest and foveate them by saccadic eye movements for further scrutiny. Thus, there is usually peripheral information available before and foveal information after a saccade. In this study we investigated the integration of information across saccades. We measured reliabilities--i.e., the inverse of variance-separately in a presaccadic peripheral and a postsaccadic foveal orientation--discrimination task...
2015: Journal of Vision
Annalisa Bosco, Markus Lappe, Patrizia Fattori
When saccadic eye movements consistently fail to land on the intended target, saccade accuracy is maintained by gradually adapting the amplitude of successive saccades to the same target. Such saccadic adaptation is usually induced by systematically displacing a small visual target during the execution of the saccade. However, saccades are normally performed to extended objects. Here we report changes in saccade amplitude when the size of a target object is systematically changed during a saccade. Moreover, we find that this manipulation also affected the visual perception of the size of that object...
October 28, 2015: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Benjamin Bolte, Markus Lappe
Virtual reality strives to provide a user with an experience of a simulated world that feels as natural as the real world. Yet, to induce this feeling, sometimes it becomes necessary for technical reasons to deviate from a one-to-one correspondence between the real and the virtual world, and to reorient or reposition the user's viewpoint. Ideally, users should not notice the change of the viewpoint to avoid breaks in perceptual continuity. Saccades, the fast eye movements that we make in order to switch gaze from one object to another, produce a visual discontinuity on the retina, but this is not perceived because the visual system suppresses perception during saccades...
April 2015: IEEE Transactions on Visualization and Computer Graphics
Martin Szinte, David Aagten-Murphy, Donatas Jonikaitis, Heiner Deubel
Our perception of the auditory and visual stimuli in the world remains stable despite frequent head and eye movements. For visual stimuli, this stability is achieved through the correction (remapping) of the object's visual representation in retinotopically organized visual and oculomotor maps. In the present study, we use saccade curvature to investigate the competition between visual saccade targets and different multi-sensory distractors. We report clear physiological evidence for the existence of a supra-modal map of locations across saccades...
2015: Journal of Vision
Jean-Baptiste Bernard, Carlos Aguilar, Françoise Vitu, Eric Castet
Reading involves multiple eye movements and necessitates the integration of visual information from successive fixations. Here, we quantify the efficiency of trans-saccadic integration during foveal and peripheral word recognition by comparing performance for a human and an ideal observer. In Experiment 1, subjects were asked to identify random trigram letters presented at 13 possible positions on an invisible horizontal line at 0° or 10° eccentricity in lower visual field (horizontal distance from fixation dot: -6 to +6 letter slots)...
2015: Journal of Vision
Christian Poth, Arvid Herwig, Werner Schneider
By making saccadic eye movements, we can bring interesting peripheral objects into the fovea for high-acuity examination. Every saccade abruptly displaces and alters the retinal image of objects. Nevertheless, we perceive objects as stable in their locations. The visual system seems to deal with the retinal image displacement by actively assuming object stability across saccades. This assumption seems to be responsible for concealing actual object displacements across the saccade, rendering them hard to detect (cf...
2015: Journal of Vision
Matteo Valsecchi, Karl Gegenfurtner
Our visual world appears uniform despite the fact that the properties of our visual system change dramatically between foveal and peripheral vision. This might be explained by the fact that our visual system is able to predict the changes in sensory inputs associated with our eye movements and use potential prediction errors in order to maintain perceptual calibration. In a series of experiments we investigated whether the repeated exposure to a trans-saccadic change in the size of the object being foveated can lead to a change in its perceived size when viewed peripherally...
2015: Journal of Vision
B-R Baltaretu, B Dunkley, S Monaco, Y Chen, J Crawford
To date, the neural mechanisms of feature information integration across saccades, also known as trans-saccadic integration (TSI), of low-level object features are relatively unknown. Using fMRI adaptation (fMRIa), we found that the right inferior parietal lobule (IPL; specifically, SMG) and extrastriate cortex (putative V4) are sensitive to stimulus orientation in a space-fixed reference frame (Dunkley & Crawford, Society for Neuroscience Abstracts, 2012). To identify the neural mechanisms of underlying TSI in multiple reference frames, we employed fMRIa to probe three spatial conditions: 1) Space-fixed, 2) Retina-fixed and 3) Frame-independent (neither Space-fixed, nor Retina-fixed)...
2015: Journal of Vision
Celine Paeye, Therese Collins, Patrick Cavanagh
When saccading towards a grating that disappears during the eye movement, observers report a short-lived sensation of this target at the saccade goal (Wolf et al, 1980). Our study further characterizes this short-lived percept, examining how its localization can be influenced by a highly dissimilar post-saccadic stimulus. Participants made saccades towards a small, black square. During the eye movement this target was replaced with a white disk that was eight (experiment 1) or ten (experiment 2) times larger...
2015: Journal of Vision
Yalda Mohsenzadeh, J Crawford
After an intervening eye movement, or saccade, humans and animals are able to localize previously perceived visual targets (spatial updating). Although efforts have been made to discover the mechanism underlying spatial updating, there are still many unanswered questions about the neuronal mechanism of this phenomenon. State space model is an effective method for modeling dynamical systems and it can represent the internal behaviour of these systems. Therefore, we developed a state space model for updating target-related spatial information in gaze-centered coordinates...
2015: Journal of Vision
Cécile Eymond, Céline Paeye, Marianne Duyck, Patrick Cavanagh, Thérèse Collins
Sensorimotor adaptation is the process by which new associations between movements and their perceptual effects are learned. Previous work reported that the visual system learns associations between peripheral (coarse) and foveal (highly defined) images of objects to achieve feature constancy across eye movements (e.g., Cox et al., 2005). Here we investigated the ability to learn perceptual associations between peripheral and foveal object size across saccades. In a pre-adaptation phase, participants made saccades to a peripheral disk...
2015: Journal of Vision
Raphaëlle Malassis, Antoine Del Cul, Thérèse Collins
Predicting the sensory consequences of saccadic eye movements likely plays a crucial role in planning sequences of saccades and in maintaining visual stability despite saccade-caused retinal displacements. Deficits in predictive activity, such as that afforded by a corollary discharge signal, have been reported in patients with schizophrenia, and may lead to the emergence of positive symptoms, in particular delusions of control and auditory hallucinations. We examined whether a measure of delusional thinking in the general, non-clinical population correlated with measures of predictive activity in two oculomotor tasks...
2015: PloS One
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