Dominant frequency content of ocular microtremor from normal subjects

Bolger, Ciarán; Bojanić, Stana; Sheahan, N. F.; Coakley, Davis; Malone, J. F.

doi:10.1016/s0042-6989(98)00322-8

Cited by 54 publications

(46 citation statements)

References 16 publications

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“…This is consistent with the findings reported by Usher and Donnelly (1998), in which sensitivity decreased as presentation duration T S increased from 32 to 160 msec. Current estimates put T E at between 10 and 25 msec (Bolger et al, 1999). A spectral analysis of the image motion recorded in Experiment 3 (due to head and eye movement) revealed a peak at around 40 Hz, with a much smaller but pronounced peak at 80 Hz.…”

Section: Discussionmentioning

confidence: 82%

“…Microsaccades, on the other hand, can be both large and fast, and so might play a role, although their relative infrequency (approximately one every 500 msec, according to Coakley, 1983) would limit their influence over many trials. The third form of eye movement, ocular microtremor (OMT, or physiological nystagmus), has a relatively small amplitude but is both fast and continuous (Bolger, Bojanic, Sheahan, Coakley, & Malone, 1999;Carpenter, 1988;Ratliff & Riggs, 1950), making it a strong candidate for producing eye movement influence in rapid presentation paradigms. The maximum offsets one would expect in a pair of rows of elements shown for two consecutive 10-msec intervals are shown in Table 1, with derivation of the OMT values described in the Appendix.…”

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confidence: 99%

“…Note-The translation component in this period due to oculomotor microtremors (OMTs) and microsaccades is much larger than that due to drift. The figures are only approximate, since reports differ in the literature as to the precise values and will depend on the particular individual (Bolger, Bojanic, Sheahan, Coakley, & Malone, 1999;Carpenter, 1988;Ratliff & Riggs, 1950). More information for the process of calculating the amplitude of OMT influence is given in the Appendix.…”

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confidence: 99%

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A spatial explanation for synchrony biases in perceptual grouping: Consequences for the temporal-binding hypothesis

Wallis

2005

Perception & Psychophysics

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If two images are shown in rapid sequential order, they are perceived as a single, fused image. Despite this, recent studies have revealed that fundamental perceptual processes are influenced by extremely brief temporal offsets in stimulus presentation. Some researchers have suggested that this is due to the action of a cortical temporal-binding mechanism, which would serve to keep multiple mental representations of one object distinct from those of other objects. There is now gathering evidence that these studies should be reassessed. This article describes evidence for sensitivity to fixational eye and head movements, which provides a purely spatial explanation for the earlier results. Taken in conjunction with other studies, the work serves to undermine the current body of behavioral evidence for a temporal-binding mechanism.

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Section: Discussionmentioning

confidence: 82%

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confidence: 99%

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confidence: 99%

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A spatial explanation for synchrony biases in perceptual grouping: Consequences for the temporal-binding hypothesis

Wallis

2005

Perception & Psychophysics

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“…To detect a full spectrum of the eye movements, a much faster camera is needed. Tremor, one of the fastest movement in the human body can reach frequencies up to 100Hz [25]. Majority of videokeratometers are dedicated to create the single topography map of the cornea.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Analysis of keratoscopic images for detecting fixational eye movements and ocular surface deformation

2009

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A sequence of videokeratoscopic images was registered using commercially available instrument E300 at a rate of 50 fps. During the 20 seconds measurement, subject's head was fixed strongly. Acquired images were analyzed for detecting fixational eye movements and corneal surface deformation. For this purpose two rings were extracted from each frame and the ellipses were fitted to them, using least square method. The time series of the ellipses geometrical parameters were considered: minor and major axes length as well as the ellipses center and the orientation. The frequency spectra of mentioned parameters were obtained by application of the Fast Fourier Transform. The longitudinal position of the corneal apex was controlled, thanks to the cone side viewer installed inside the videokeratoscope. The average amplitude of the variation of the ellipse's axes length is around 20μm and of the orientation of the ellipse around 0,1 rad. In the signals frequency characteristics, appear the peak corresponding to the heart rate. No clear relationship was found between the variations of the fitted ellipse parameters and the longitudinal position of the corneal apex. The fixational eye movements were examined using two different methods. One of them consists of calculating the correlation function between the first and successive frame of the sequence and searching its maximum. The other is based on tracking the center of the ellipse fitted to particular ring of the videokeratoscopic image. The accuracy of the second method found to be higher. Simple methods proposed in this work can extend the application of videokeratoscopic measurements.

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“…At first sight tremor seems reasonable near the visual centre, because it is small in magnitude, however the frequency is high. Bolger et al (1999) measured ocular microtremor, finding frequencies in the range 70-100Hz, with a mean frequency of 84Hz. If "on" or "off" responses can be produced by movements of outlines at this frequency, then tremor could be used for detection of sharp outlines, perhaps, with activity in the form of "spikes" corresponding with the "onset" or "offset" events.…”

Section: Detection Of Outlines and Intensitymentioning

confidence: 99%

A Model for Visual Perception and Recognition of Outlines

Firth¹

2017

Preprint

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Many topics in vision are still not well understood. A model for visual perception and recognition of shapes is described, by combining ideas relating to receptive fields of ganglion cells in the retina, eye movements during fixation, multiple spatial scales of precision, attention, axes and coordinates. The main objective is to provide a realistic scheme for perception of outlines, with recognition that is not prevented by changes of size and viewpoint. Outlines are detected by changes with time arising from eye movements, followed by identification of vertical and horizontal axes, and use of levels of precision that depend on the size of the area of attention. The increments of position in these levels increase in size as the size of area increases, so in an index of positions the increment numbers remain constant for all sizes. After changes of viewpoint, "attentional planes" connect changed positions on outlines to positions with a standard orientation of axes, so that shapes may be matched with stored representations. Spatial coordinates are related to positions at the retina by representations based on eye movements.

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Dominant frequency content of ocular microtremor from normal subjects

Cited by 54 publications

References 16 publications

A spatial explanation for synchrony biases in perceptual grouping: Consequences for the temporal-binding hypothesis

A spatial explanation for synchrony biases in perceptual grouping: Consequences for the temporal-binding hypothesis

Analysis of keratoscopic images for detecting fixational eye movements and ocular surface deformation

A Model for Visual Perception and Recognition of Outlines

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