The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Howard C. Hughes - One of the best experts on this subject based on the ideXlab platform.
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effects of warning signals and Fixation Point offsets on the latencies of pro versus antisaccades implications for an interpretation of the gap effect
Experimental Brain Research, 1995Co-Authors: Patricia A Reuterlorenz, H M Oonk, L L Barnes, Howard C. HughesAbstract:The present study was designed to evaluate whether Fixation Point offsets have the same effects on the average latencies of prosaccades (responses towards target) and antisaccades (responses away from target). Gap and overlap conditions were run with and without an acoustic warning signal. The 'gap effect' was taken to be the difference in mean reaction time between gap and overlap trials. This effect was dramatically reduced by the presentation of the warning signal. Without this sig- nal, Fixation offsets can serve as warning signals them- selves, which artifactually inflates the magnitude of the gap effect. The warning effect of Fixation offsets was equivalent for pro and antisaccades. A significant gap ef- fect is still evident with the acoustic warning signal; however, in this case it is associated primarily with prosaccades. These results replicate and extend our pre- vious work demonstrating that, if their warning effects are controlled, the facilitatory effects of Fixation Point offsets are response dependent, and suggesting the exis- tence of a component process (Fixation release) which is closely linked with the processing architecture underly- ing target-directed saccades.
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Fixation-Point offsets reduce the latency of saccades to acoustic targets
Attention Perception & Psychophysics, 1991Co-Authors: Robert Fendrich, Howard C. Hughes, Patricia A. Reuter-lorenzAbstract:If an observer’s Fixation Point is extinguished just prior to the onset of a peripheral target, the latency to saccade to that target is reduced. We show that this "gap effect" is not specific to visual targets. Observers made saccades to a light flash or to a white-noise burst. A warning tone was presented on every trial to control for the possible warning effect of the Fixation-Point offset. For both target modalities, saccade latencies were significantly reduced when the Fixation Point was extinguished 200 msec prior to the target onset. Implications of this outcome for interpretations of the gap effect are considered. It is argued that the presence of a gap effect for tones, in conjunction with previous findings, is consistent with the hypothesis that the gap effect is produced by a facilitation of premotor processes in the superior colliculus.
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the reduction of saccadic latency by prior offset of the Fixation Point an analysis of the gap effect
Attention Perception & Psychophysics, 1991Co-Authors: Patricia A Reuterlorenz, Howard C. Hughes, Robert FendrichAbstract:The latency to initiate a saccade (saccadic reaction time) to an eccentric target is reduced by extinguishing the Fixation stimulus prior to the target onset. Various accounts have attributed this latency reduction (referred to as thegap effect) to facilitated sensory processing, oculomotor readiness, or attentional processes. Two experiments were performed to explore the relative contributions of these factors to the gap effect. Experiment 1 demonstrates that the reduction in saccadic reaction time (RT) produced by Fixation Point offset is additive with the effect of target luminance. Experiment 2 indicates that the gap effect is specific for saccades directed toward a peripheral target and does not influence saccades directed away from the target (i.e., antisaccades) or choice-manual RT. The results are consistent with an interpretation of the gap effect in terms of facilitated premotor processing in the superior colliculus.
Robert Fendrich - One of the best experts on this subject based on the ideXlab platform.
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The oculomotor gap effect without a foveal Fixation Point
Vision Research, 1999Co-Authors: Robert Fendrich, S Demirel, Shai DanzigerAbstract:Abstract 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° 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°. Results are interpreted in terms of a partial mediation of the gap effect by Fixation cells in the rostral pole of the superior colliculus.
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Are microsaccades responsible for the gap effect
Attention Perception & Psychophysics, 1995Co-Authors: Alan Kingstone, Robert Fendrich, Patricia A. Reuter-lorenz, C. Mark WessingerAbstract:Extinguishing a Fixation Point shortly before, or concurrently with, the onset of a peripheral visual target reduces the latency of saccades to that target. Saslow (1967) hypothesized that thisgap effect might occur because Fixation Point offsets reduce the incidence of corrective microsaccades with an associated saccadic refractory period. In the present study, a robust gap effect was obtained. However, using a Purkinje image eyetracker with 1 arcmin of resolution, we found that Fixation Point offsets had no effect on the occurrence of microsaccades and that the occurrence of microsaccades had no impact on the magnitude of the gap effect. Microsaccades therefore do not appear to play any part in the production of the gap effect.
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Fixation-Point offsets reduce the latency of saccades to acoustic targets
Attention Perception & Psychophysics, 1991Co-Authors: Robert Fendrich, Howard C. Hughes, Patricia A. Reuter-lorenzAbstract:If an observer’s Fixation Point is extinguished just prior to the onset of a peripheral target, the latency to saccade to that target is reduced. We show that this "gap effect" is not specific to visual targets. Observers made saccades to a light flash or to a white-noise burst. A warning tone was presented on every trial to control for the possible warning effect of the Fixation-Point offset. For both target modalities, saccade latencies were significantly reduced when the Fixation Point was extinguished 200 msec prior to the target onset. Implications of this outcome for interpretations of the gap effect are considered. It is argued that the presence of a gap effect for tones, in conjunction with previous findings, is consistent with the hypothesis that the gap effect is produced by a facilitation of premotor processes in the superior colliculus.
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the reduction of saccadic latency by prior offset of the Fixation Point an analysis of the gap effect
Attention Perception & Psychophysics, 1991Co-Authors: Patricia A Reuterlorenz, Howard C. Hughes, Robert FendrichAbstract:The latency to initiate a saccade (saccadic reaction time) to an eccentric target is reduced by extinguishing the Fixation stimulus prior to the target onset. Various accounts have attributed this latency reduction (referred to as thegap effect) to facilitated sensory processing, oculomotor readiness, or attentional processes. Two experiments were performed to explore the relative contributions of these factors to the gap effect. Experiment 1 demonstrates that the reduction in saccadic reaction time (RT) produced by Fixation Point offset is additive with the effect of target luminance. Experiment 2 indicates that the gap effect is specific for saccades directed toward a peripheral target and does not influence saccades directed away from the target (i.e., antisaccades) or choice-manual RT. The results are consistent with an interpretation of the gap effect in terms of facilitated premotor processing in the superior colliculus.
Patricia A Reuterlorenz - One of the best experts on this subject based on the ideXlab platform.
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effects of warning signals and Fixation Point offsets on the latencies of pro versus antisaccades implications for an interpretation of the gap effect
Experimental Brain Research, 1995Co-Authors: Patricia A Reuterlorenz, H M Oonk, L L Barnes, Howard C. HughesAbstract:The present study was designed to evaluate whether Fixation Point offsets have the same effects on the average latencies of prosaccades (responses towards target) and antisaccades (responses away from target). Gap and overlap conditions were run with and without an acoustic warning signal. The 'gap effect' was taken to be the difference in mean reaction time between gap and overlap trials. This effect was dramatically reduced by the presentation of the warning signal. Without this sig- nal, Fixation offsets can serve as warning signals them- selves, which artifactually inflates the magnitude of the gap effect. The warning effect of Fixation offsets was equivalent for pro and antisaccades. A significant gap ef- fect is still evident with the acoustic warning signal; however, in this case it is associated primarily with prosaccades. These results replicate and extend our pre- vious work demonstrating that, if their warning effects are controlled, the facilitatory effects of Fixation Point offsets are response dependent, and suggesting the exis- tence of a component process (Fixation release) which is closely linked with the processing architecture underly- ing target-directed saccades.
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the reduction of saccadic latency by prior offset of the Fixation Point an analysis of the gap effect
Attention Perception & Psychophysics, 1991Co-Authors: Patricia A Reuterlorenz, Howard C. Hughes, Robert FendrichAbstract:The latency to initiate a saccade (saccadic reaction time) to an eccentric target is reduced by extinguishing the Fixation stimulus prior to the target onset. Various accounts have attributed this latency reduction (referred to as thegap effect) to facilitated sensory processing, oculomotor readiness, or attentional processes. Two experiments were performed to explore the relative contributions of these factors to the gap effect. Experiment 1 demonstrates that the reduction in saccadic reaction time (RT) produced by Fixation Point offset is additive with the effect of target luminance. Experiment 2 indicates that the gap effect is specific for saccades directed toward a peripheral target and does not influence saccades directed away from the target (i.e., antisaccades) or choice-manual RT. The results are consistent with an interpretation of the gap effect in terms of facilitated premotor processing in the superior colliculus.
Jay Pratt - One of the best experts on this subject based on the ideXlab platform.
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Estimating the components of the gap effect.
Experimental Brain Research, 2000Co-Authors: Jay Pratt, Harold Bekkering, Mark LeungAbstract:The gap effect refers to the finding that saccadic latencies are typically reduced when a Fixation Point is removed prior to the appearance of a peripheral target. This reduction in saccadic reaction time (SacRT) is thought to be due to a general warning effect and an oculomotor specific Fixation offset that occur when the Fixation Point is removed. In order to estimate the contribution of each of these effects to the overall gap effect, this paper introduces a new manipulation, the partial-gap trial, where the Fixation Point undergoes a change in size prior to the presentation of the target. The partial-gap trial is presumed to provide the visual warning effect of the Fixation offset (i.e. similar to that in a gap trial) but does not provide the Fixation offset effect (FOE). When the Fixation Point was abruptly reduced in size before the presentation of the target, the estimated decrease in SacRT due to the visual warning effect was 5–7% and did not differ in the presence or absence of an auditory warning signal. It was found that auditory warning effect and the FOE interacted in reducing SacRTs. Additionally, when the Fixation Point was abruptly increased in size before the presentation of the target, SacRTs were slower than when the Fixation Point did not change in size and remained present for the entire trial (i.e. an overlap trial). We conclude that this new partial-gap paradigm is a useful method for researchers wishing to separately examine FOE and visual warning effects.
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Visual Fixation offsets affect both the initiation and the kinematic features of saccades
Experimental Brain Research, 1998Co-Authors: Jay PrattAbstract:It is well known that the removal of a Fixation Point prior to the presentation of a peripheral target dramatically reduces saccadic reaction time (SRT). This effect has become known as the “gap effect”. The present study examined several detailed kinematic variables to determine whether the removal of the Fixation Point also affects the manner in which saccades are produced. The findings indicate that saccades that were initiated after the removal of the Fixation Point had higher average velocities and reached greater peak velocities, accelerations, and decelerations than did saccades produced in the presence of the Fixation Point. The results suggest that the removal of the Fixation Point may affect the force-time curves of saccades in addition to affecting the time needed to initiate the saccades.
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Fixation Point offsets facilitate endogenous saccades
Attention Perception & Psychophysics, 1998Co-Authors: Richard A Abrams, Heather M Oonk, Jay PrattAbstract:Subjects produced saccades to continuously visible targets that were signaled by the pitch, not the location, of an auditory signal. Such endogenous saccades were initiated more quickly when the visual Fixation Point disappeared 200 msec before the signal (thus producing a “gap”), even though the alerting benefits of such a warning were eliminated by an earlier warning tone. The presence of the gap effect under these circumstances shows that the effect is more general than was previously believed: Visual Fixation Point offsets facilitate saccades by affecting oculomotor processes related to both visually elicited (exogenous) and centrally produced (endogenous) saccades. In addition, the magnitude of the gap effect for endogenous saccades was significantly smaller than that for exogenous saccades, suggesting that at least some of the effect arises in relatively early processes, such as those involved in the processing of sensory signals, and not exclusively in later processes, such as those involved in the preparation and production of saccades.
H. Koshimizu - One of the best experts on this subject based on the ideXlab platform.
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ICPR - Realization of an efficient line detection by askant glance camera vision system using extended Hough transform
Proceedings. Fourteenth International Conference on Pattern Recognition (Cat. No.98EX170), 1998Co-Authors: Masafumi Tominaga, Kunihito Kato, Kazuhito Murakami, H. KoshimizuAbstract:We propose a new vision mechanism which can saccadicly move its Fixation Point for detecting straight lines within the image frame. This system, askant glance camera vision (AGCV) system, can extract straight lines precisely around the Fixation Point and rather coarsely at the periphery of the Fixation Point. This camera system works in such a way that the Fixation Point catches the moving object by the information of the center of gravity of edges, and the edges of the moving object can be extracted better than the edges of the stationary object. This system demonstrates a model of the center fine/peripheral-coarse characteristics of human vision. This system is constructed by a slab-system which uses extended Hough transform functions and another subsystem which tracks an object and shifts its Fixation Point to the center of gravity. In this paper, we show some experimental results to show the performance of AGCV system.
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MVA - Realization of Askant Glance Camera Vision System by Using Extended Hough Transform
Journal of Machine Vision and Applications, 1996Co-Authors: Masafumi Tominaga, Kunihito Kato, Kazuhito Murakami, H. KoshimizuAbstract:We propose a new vision mechanism which can saccadicly move its Fixation Point for detecting straight lines within tlie image frame. Tliis system, askant glance camera vision ( AGCV ) system, can extract straight lines precisely around the Fixation Point and ratlier coarsely at tlie periphery of the Fixation Point. Tliis camera system works in such a way that tlie Fixation Point catches tlie moving object by tlie information of the center of b~avity of edges, and the edges of tlie moving object can be extracted ratlier finely than the edges of the sleeping object. Tliis system demonstrates a model of tlie center - fine / peripheral coarse characteristics of human vision. This system is constn~cted by a sub-system which uses extended Hougli transform filnctions and another sub-system which tracks an object and shifts its Fixation Point to tlie center of gravity. In tliis paper, we show some experimental results to sliow tlie performance of AGCV system. basic configuration of AGCV system and how to track the moving objects in a manner of askant glance. Finally we present some experimental results to demonstrate the effectivity of the AGCV system. Although this camera vision imitates sidelong glance, it is different from such a camera vision that pursues an object by moving its camera head. AGCV system extracts straight lines precisely around the Fixation Point and rather coarsely at tlie periphery of tlie Fixation Point in a software contrivance using an extended Hougli transform ( EHT ) fiinction. In section 3, we sliow the basis theory of EHT fiinction, and in section 4, we show an example of AGCV system which tracks moving objects. In section 5, the concept of the askant glance is extended to the angular sensitivity for line detection.