Duration Illusions in a Train of Visual Stimuli

Perception ◽  
1995 ◽  
Vol 24 (10) ◽  
pp. 1177-1187 ◽  
Author(s):  
David Rose ◽  
Joanna Summers
Keyword(s):  
Visual System ◽  
Visual Stimuli ◽  
Stimulus Contrast ◽  
Stimulus Processing ◽  
Interflash Interval

The first stimulus in a sequential train of identical flashes of light appears to last longer than those in the middle of the train. Four flashes (each 600 or 667 ms) were presented and the first was shortened until it appeared to have the same duration as that of the next. The duration of the first stimulus was found to be overestimated by about 50%. The illusion was unaffected by stimulus contrast, size, or interflash interval (between 100 and 600 ms). For some subjects, the last stimulus in the train also appeared to be about 50% longer than the penultimate flash. The results are discussed in terms of theories of how attention, arousal, and stimulus processing can affect duration perception. The mechanisms activated are peculiar to the visual system, since no similar illusion of duration was consistently experienced with a train of auditory tones.

scholarly journals Using perceptual tasks to selectively measure magnocellular and parvocellular performance: Rationale and a user’s guide

2021 ◽  
Author(s):  
Mark Edwards ◽  
Stephanie C. Goodhew ◽  
David R. Badcock
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Lateral Geniculate Nucleus ◽  
Cognitive Functions ◽  
Visual Information ◽  
Visual Stimuli ◽  
Visual Scene ◽  
Ongoing Debate ◽  
Parvocellular Pathway ◽  
Lesion Studies

AbstractThe visual system uses parallel pathways to process information. However, an ongoing debate centers on the extent to which the pathways from the retina, via the Lateral Geniculate nucleus to the visual cortex, process distinct aspects of the visual scene and, if they do, can stimuli in the laboratory be used to selectively drive them. These questions are important for a number of reasons, including that some pathologies are thought to be associated with impaired functioning of one of these pathways and certain cognitive functions have been preferentially linked to specific pathways. Here we examine the two main pathways that have been the focus of this debate: the magnocellular and parvocellular pathways. Specifically, we review the results of electrophysiological and lesion studies that have investigated their properties and conclude that while there is substantial overlap in the type of information that they process, it is possible to identify aspects of visual information that are predominantly processed by either the magnocellular or parvocellular pathway. We then discuss the types of visual stimuli that can be used to preferentially drive these pathways.

scholarly journals Cortical reorganization of the visual system in post-stroke hemianopia studied with fMRI

Stroke ◽  
2001 ◽  
Vol 32 (suppl_1) ◽  
pp. 334-334
Author(s):  
Gereon Nelles ◽  
Guido Widmann ◽  
Joachim Esser ◽  
Anette Meistrowitz ◽  
Johannes Weber ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Visual Stimuli ◽  
Checkerboard Pattern ◽  
Partial Recovery ◽  
Area 18 ◽  
Area 19 ◽  
Stimulation Of

102 Introduction: Restitution of unilateral visual field defects following occipital cortex lesions occurs rarely. Partial recovery, however, can be observed in patients with incomplete lesion of the visual cortex. Our objective was to study the neuroplastic changes in the visual system that underlie such recovery. Methods and Results: Six patients with a left PCA-territory cortical stroke and 6 healthy control subjects were studied during rest and during visual stimulation using a 1.5 T fMRI with a 40 mT gradient. Visual stimuli were projected with a laptop computer onto a 154 x 115 cm screen, placed 90 cm in front of the gantry. Subjects were asked to fixate a red point in the center of the screen during both conditions. During stimulation, a black-and-white checkerboard pattern reversal was presented in each hemifield. For each side, 120 volumes of 48 contiguous axial fMRI images were obtained during rest and during hemifield stimulation in alternating order (60 volumes for each condition). Significant differences of rCBF between stimulation and rest were assessed as group analyses using statistical parametric mapping (SPM 99; p<0.01, corrected for multiple comparison). In controls, strong increases of rCBF (Z=7.6) occurred in the contralateral primary visual cortex V1 (area 17) and in V3a (area 18) and V5 (area 19). No differences were found between the right and left side in controls. During stimulation of the unaffected (left) visual field in hemianopic patients, activation occurred in contralateral V1, but the strongest increases of rCBF (Z>10) were seen in contralateral V3a (area 18) and V5 (area 19). During stimulation of the hemianopic (right) visual field, no activation was found in the primary visual cortex of either hemisphere. The most significant activation (Z=9.2) was seen in the ipsilateral V3a and V5 areas, and contralateral (left) V3a. Conclusions: Partial recovery from hemianopia is associated with strong ipsilateral activation of the visual system. Processing of visual stimuli in the hemianopic side spares the primary visual cortex and may involve recruitment of neurons in ipsilateral (contralesional) areas V3a and V5.

The turtle visual system mediates a complex spatiotemporal transformation of visual stimuli into cortical activity

2017 ◽  
Vol 204 (2) ◽  
pp. 167-181 ◽  
Author(s):  
Mahmood S. Hoseini ◽  
Jeff Pobst ◽  
Nathaniel C. Wright ◽  
Wesley Clawson ◽  
Woodrow Shew ◽  
...  
Keyword(s):  
Visual System ◽  
Visual Stimuli ◽  
Cortical Activity

scholarly journals Reduplication of Visual Stimuli

1994 ◽  
Vol 7 (3-4) ◽  
pp. 135-142 ◽  
Author(s):  
A. W. Young ◽  
D. J. Hellawell ◽  
S. Wright ◽  
H. D. Ellis
Keyword(s):  
Recognition Memory ◽  
Visual System ◽  
Facial Expressions ◽  
Visual Stimuli ◽  
Auditory Stimuli ◽  
Emotional Facial Expressions ◽  
Visual Problem

Investigation of P.T., a man who experienced reduplicative delusions, revealed significant impairments on tests of recognition memory for faces and understanding of emotional facial expressions. On formal tests of his recognition abilities, P.T. showed reduplication to familiar faces, buildings, and written names, but not to familiar voices. Reduplication may therefore have been a genuinely visual problem in P.T.'s case, since it was not found to auditory stimuli. This is consistent with hypotheses which propose that the basis of reduplication can lie in part in malfunction of the visual system.

scholarly journals Is the Tilt-Illusion in the stimuli?

2018 ◽  
Author(s):  
Bernt Skottun
Keyword(s):  
Visual System ◽  
Present Report ◽  
Visual Stimuli ◽  
Orientation Tuning ◽  
Tilt Illusion ◽  
Amplitude Spectra

Interference between visual stimuli has been assessed mainly in regard to how such interactions mayreduce stimulus power. The question of if, or to what extent, interference may change stimuli in other wayshas been largely ignored. The present report asks if interference may alter the amplitude spectra of elongatedcontours so as cause their perceived orientations to be changed. Computations indicate that for two stimulidiffering in orientation by between 5 and 40 degrees interference is largest for orientations between the peakorientations of the two stimuli which may cause their orientation tuning functions to be ”pushed” apart.Since interference takes place in the stimuli and is independent of vision and the visual system it is possible,therefore, for the physics of stimuli to cause illusory tilt.

scholarly journals Even Moderate Visual Stimuli Leads to Behavioural Responses in Term and Preterm Infants

2019 ◽  
Vol 12 (1) ◽  
pp. 14-15
Author(s):  
C. Zores ◽  
V. Vincent ◽  
A. Marchal ◽  
M. Davy ◽  
D. Astruc ◽  
...  
Keyword(s):  
Visual System ◽  
Preterm Infants ◽  
Visual Stimuli ◽  
Light Level ◽  
Hospital Environment ◽  
Sleep Disruption ◽  
Very Preterm Infants ◽  
Behavioural Responses ◽  
Very Preterm

Very preterm infants (VPI) are exposed to atypical visual stimuli in the hospital. Their visual system was shown to be mature enough to allow them to physiologically react to ecological visual stimuli in the NICU from 28 weeks post-menstrual age (PMA). These stimuli have also been shown to induce sleep disruption. However, little is known about their behavioural responses to light level changes of different amplitudes, encountered in the hospital environment.

A Study on Visual Mechanism with Optical Illusions

1997 ◽  
Vol 9 (2) ◽  
pp. 85-91 ◽  
Author(s):  
Masanori Idesawa ◽  
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Visual Stimuli ◽  
Close Relation ◽  
Depth Information ◽  
Optical Illusions ◽  
System A ◽  
Visual Mechanism ◽  
Human Visual Mechanism ◽  
Processing Techniques

Optical illusion seems to be the phenomena which are purely reflecting the mechanism of.human visual system and are expected as the effective cues to elucidating human visual mechanism. The author found the new types of 3-D visual illusion with binocular viewing. From the visual stimuli of binocular disparity given only along the contour of an object, human visual system can perceive entire 3-D illusory object where there are no physical visual stimuli giving depth information. They have close relation with the 3-D space perceiving functions in the human visual system. A study on these newly found optical illusions are introduced and the considerations are made for their applications and the exploitations including the contributions of information processing techniques such as computer graphics, computer vision and so on.

scholarly journals 3-D Illusory Phenomena with Binocular Viewing and Computer Vision

1992 ◽  
Vol 4 (3) ◽  
pp. 249-255
Author(s):  
Masanori Idesawa ◽  
Keyword(s):  
Computer Vision ◽  
Visual System ◽  
Human Visual System ◽  
Visual Function ◽  
Vision System ◽  
Visual Stimuli ◽  
Space Perception ◽  
Binocular Viewing ◽  
Depth Information ◽  
New Paradigm

The human visual system can perceive 3-D information of an object by using disparity between two eyes, gradient of illumination (shading), occlusion, textures and their perspective and so on. Consequently, the disparity and the occlusion observed with binocular viewing seems to be the most important cues to get 3-D information. For the artificial realization of the visual function such as in computer vision or robot vision system, it seems to be a clever way to learn from the human visual mechanism. Recently, the author found a new type of illusion. When the visual stimuli of disparity are given only partially along the contour of an object, human visual system can perceive the 3-D surface (not only plane but also curved) of the object where there are no physical visual stimuli to get depth information. The interactions between the perceived illusory surface (occlusion, intersection and transparency) can be recognized. These newly found illusory phenomena have close relations with the visual function of 3-D space perception and can provide a new paradigm in the field of computer vision and human interface.

ERG assessment of zebrafish retinal development

1999 ◽  
Vol 16 (5) ◽  
pp. 881-888 ◽  
Author(s):  
SHANNON SASZIK ◽  
JOSEPH BILOTTA ◽  
CARLA M. GIVIN
Keyword(s):  
Visual System ◽  
Spectral Sensitivity ◽  
Gradual Increase ◽  
Retinal Development ◽  
Visual Stimuli ◽  
Age Groups ◽  
Adult Zebrafish ◽  
Strong Response ◽  
Anatomical Studies ◽  
Sensitivity Functions

Research has shown that adult zebrafish have a complex visual system, with two possible opponent mechanisms. Anatomically, zebrafish retina develops in a sequential manner and is immature at hatching. The purpose of the present study was to assess zebrafish retinal development using the electroretinogram (ERG). ERG responses to visual stimuli were obtained from 4–5, 6–8, 13–15, and 21–24 days postfertilization (dpf) zebrafish. Individual waveforms were assessed and compared across the four age groups. Spectral-sensitivity functions were calculated for the a- and b-wave components of the ERG response. Results showed that the ERG waveforms and spectral-sensitivity functions varied with age. While the 21–24 dpf subjects had an ERG waveform that was similar to that of adults, the younger subjects did not. Although there were modest differences in the a-wave spectral sensitivity, substantial differences were found in the b-wave spectral sensitivities across the ages. There was a consistent strong response to ultraviolet wavelengths, while across the remaining parts of the spectrum, there was a gradual increase in sensitivity with age. Also, the 21–24 dpf subjects appear to have adult-like U- and S-cone functions, but were missing the L-M and the M-S opponent mechanisms found in the adult. These results support the findings of the anatomical studies and demonstrate that the zebrafish is a useful model for examining the development of retinal function.

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