Occurrence of express saccades under isoluminance and low contrast luminance conditions

1991 ◽  
Vol 7 (5) ◽  
pp. 505-510 ◽  
Author(s):  
Heike Weber ◽  
Burkhart Fischer ◽  
Michael Bach ◽  
Franz Aiple
Keyword(s):  
Human Subjects ◽  
Reaction Times ◽  
Luminance Contrast ◽  
Saccade Target ◽  
White Background ◽  
Color Contrast ◽  
Express Saccades ◽  
Low Contrast ◽  
Green Background ◽  
White Target

AbstractSaccadic reaction times (SRTs) of three human subjects were analyzed. The gap paradigm was used (i.e. fixation point offset precedes target onset) to obtain high proportions of express saccades (i.e. saccades of extremely short reaction times) in the SRT distributions. In one set of experiments, the luminance of the (red) saccade target was varied from brighter to darker than the (green) background including an isoluminance condition. Express saccades were obtained in response to pure color contrast stimuli with about the same frequency and reaction time as to stimuli with both color and luminance contrast. In a second experiment, the luminance contrast of a white target on a white background was lowered below 10%. Again the number of express saccades was not reduced. Thus, in contrast to other perceptual phenomena the visual neural mechanisms underlying the generation of express saccades are not affected by isoluminance nor low contrast luminance.

Color stimuli perception in presence of light scattering

2006 ◽  
Vol 23 (3-4) ◽  
pp. 597-601 ◽  
Author(s):  
MARIS OZOLINSH ◽  
MICHÉLE COLOMB ◽  
GATIS IKAUNIEKS ◽  
VARIS KARITANS
Keyword(s):  
Visual Acuity ◽  
Light Scattering ◽  
Luminance Contrast ◽  
White Background ◽  
Color Contrast ◽  
Entire Area ◽  
Red Color ◽  
Blue Component ◽  
Different Color ◽  
Landolt C

Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresponding to the blue, green, and red color contributions in achromatic white stimuli (computer digital R, G, or B values for chromatic stimuli equal to RGB values in the achromatic white background) that results in the greatest luminance contrast for the white–blue stimuli, thus advancing the visual acuity for the white-blue stimuli. Besides such blue stimuli on the white background are displayed with a uniform, spatially unmodulated distribution of the screen blue phosphor emission over the entire area of the screen including the stimulus C optotype area. It follows that scattering, which has the greatest effect on the blue component of screen luminance, has the least effect on the perception of white–blue stimuli.

Luminance and color effects on localization of briefly flashed visual stimuli

1996 ◽  
Vol 13 (3) ◽  
pp. 567-573 ◽  
Author(s):  
Roger E. Graves
Keyword(s):  
Visual Stimuli ◽  
High Sensitivity ◽  
Luminance Contrast ◽  
Stimulus Size ◽  
Color Contrast ◽  
Visual Localization ◽  
Magnocellular Pathway ◽  
Localization Task ◽  
Parvocellular System ◽  
Green Background

AbstractVisual localization was studied by flashing small stimuli on a green background and requiring observers to press keys to indicate whether the stimulus appeared to the left or right of fixation. The results suggest that, for small (0.25 deg) briefly flashed (17 ms) stimuli at an eccentric location (10 deg), color contrast is not useable and localization presumably must rely on the magnocellular pathway. When stimulus size and duration were increased at 10-deg eccentricity, isochromatic stimuli could be localized at less than 10% luminance contrast (again suggesting use of the magnocellular high sensitivity luminance-contrast system), but isoluminant color-contrast stimuli could also be localized (suggesting use of the color-contrast sensitive parvocellular system). Thus, the results indicate that, dependent on stimulus conditions, both magnocellular and parvocellular pathways were utilized by normal observers in this localization task.

scholarly journals Express saccades and superior colliculus responses are sensitive to short-wavelength cone contrast

2016 ◽  
Vol 113 (24) ◽  
pp. 6743-6748 ◽  
Author(s):  
Nathan J. Hall ◽  
Carol L. Colby
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Short Wavelength ◽  
Human Subjects ◽  
Reaction Times ◽  
Saccadic Eye Movements ◽  
Express Saccades ◽  
Color Information ◽  
Express Saccade ◽  
Psychophysical Studies

A key structure for directing saccadic eye movements is the superior colliculus (SC). The visual pathways that project to the SC have been reported to carry only luminance information and not color information. Short-wavelength–sensitive cones (S-cones) in the retina make little or no contribution to luminance signals, leading to the conclusion that S-cone stimuli should be invisible to SC neurons. The premise that S-cone stimuli are invisible to the SC has been used in numerous clinical and human psychophysical studies. The assumption that the SC cannot use S-cone stimuli to guide behavior has never been tested. We show here that express saccades, which depend on the SC, can be driven by S-cone input. Further, express saccade reaction times and changes in SC activity depend on the amount of S-cone contrast. These results demonstrate that the SC can use S-cone stimuli to guide behavior. We conclude that the use of S-cone stimuli is insufficient to isolate SC function in psychophysical and clinical studies of human subjects.

Visual thresholds to low-contrast pattern displacement, color contrast, and luminance contrast stimuli in Parkinson's disease

1994 ◽  
Vol 9 (5) ◽  
pp. 563-570 ◽  
Author(s):  
Bernhard A. Haug ◽  
Claudia Trenkwalder ◽  
Geoffrey B. Arden ◽  
Wolfgang H. Oertel ◽  
Walter Paulus
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Luminance Contrast ◽  
Color Contrast ◽  
Low Contrast ◽  
Contrast Pattern

Saccades to somatosensory targets. I. behavioral characteristics

1996 ◽  
Vol 75 (1) ◽  
pp. 412-427 ◽  
Author(s):  
J. M. Groh ◽  
D. L. Sparks
Keyword(s):  
Reaction Time ◽  
Target Location ◽  
Human Subjects ◽  
Reaction Times ◽  
Saccade Target ◽  
Velocity Amplitude ◽  
Visual Frame ◽  
Saccade Velocity ◽  
Saccade Task ◽  
Visual Targets

1. We compared the properties of saccades to somatosensory and visual targets. This comparison provides insight into the translation of sensory signals coding target location in different sensory coordinate frameworks into motor commands of a common format. Vibrotactile stimuli were delivered to the hands, which were fixed in position and concealed beneath a barrier. Saccades of different directions and amplitudes were elicited by the same somatosensory target from different initial eye positions. Both monkeys and humans served as subjects. 2. Somatosensory saccades were less accurate than visual saccades in both humans and monkeys. When the barrier concealing the hands was removed, somatosensory saccade accuracy improved. While the hands were concealed, the visual frame of reference provided by room illumination did not greatly affect saccade accuracy: accuracy was not degraded in complete darkness for two of three monkeys. 3. The endpoints of saccades to a single somatosensory target varied with initial eye position for the monkeys, but not for the human subjects. 4. We also found evidence of an effect of limb position on somatosensory saccades: when human subjects performed the task with crossed hands, the incidence of curved saccades increased. Saccades often began in the direction of the unstimulated hand and curved markedly toward the stimulated hand. When one subject was required to delay the saccade by 600-1,000 ms after target onset (the delayed saccade task), the saccades were straight. Somatosensory saccades were also straight when the hands were not crossed. 5. The reaction times of somatosensory saccades were longer than the reaction times of visual saccades, and they decreased as a function of saccade amplitude. The delayed saccade task reduced the differences between somatosensory and visual saccade reaction times. The reaction times of saccades to very dim visual targets increased into the range found for saccades to somatosensory targets. When the saccade target was the combination of the somatosensory and visual stimuli at the same location, the reaction time was slightly lower than for visual targets alone. 6. The peak velocities of somatosensory saccades were lower than those of visual saccades of the same amplitude. The velocities of saccades to combined somatosensory and visual targets were indistinguishable from those of saccades to visual targets alone. The differences between somatosensory and visual saccade velocity were maintained in the delayed trial type. These differences suggest that the main sequence or velocity-amplitude relationship characteristic of saccades depends on the modality of the target. 7. The implications of these modality-dependent differences in accuracy, reaction time, and saccade velocity are discussed with regard to models of the saccade generator and the coordinate transformation necessary for somatosensory saccades.

scholarly journals Differential effect of value and salience on saccadic reaction times

2020 ◽  
Author(s):  
Mohammad Shams-Ahmar ◽  
Peter Thier
Keyword(s):  
Reaction Time ◽  
Rhesus Macaques ◽  
Reaction Times ◽  
Saccade Target ◽  
Visually Guided ◽  
Express Saccades ◽  
Visual Objects ◽  
Subjective Value ◽  
Reward Expectancy ◽  
The Impact

ABSTRACTExpress saccades, a mode of visually guided saccades, distinguished from regular saccades by extremely short reaction times, are triggered by inserting a temporal gap between the fixation dot and the saccade target. It is usually assumed that they are produced by a specific pathway in which the superior colliculus plays a key role. Whether and how this pathway deals with information on the subjective value of a saccade target is unknown. We, therefore, studied the influence of varying reward expectancies and compared it with the impact of the presence and absence of a temporal gap between the disappearance of the fixation dot and the appearance of the target on the visually guided saccades of two rhesus macaques (Macaca mulatta). We observed that the introduction of a gap shifted the entire saccadic reaction time distribution to shorter latencies while increasing the probability of express saccades. On the other hand, promoting the monkey’s reward expectancy shortened reaction times and increased peak velocities of regular saccades, and increased the probability of express saccades. Importantly, we observed that the reaction time and peak velocity of express saccades were not sensitive to the value of the saccade target, suggesting that the express pathway does not have access to information on value. We propose a new model on express saccades that treats the salience of visual objects in the scene differently from the subjective value assigned to them.

Sensitivity of express saccades to the expected value of the target

2020 ◽  
Author(s):  
Mohammad Shams-Ahmar ◽  
Peter Thier
Keyword(s):  
Reaction Time ◽  
Time Distribution ◽  
Reaction Times ◽  
Reaction Time Distribution ◽  
Saccade Target ◽  
Visually Guided ◽  
Express Saccades ◽  
Reward Expectancy ◽  
Saccadic Reaction Times ◽  
The Impact

Express saccades, a distinct fast mode of visually guided saccades, are probably underpinned by a specific pathway that is at least partially different from the one underlying regular saccades. Whether and how this pathway deals with information on the subjective value of a saccade target is unknown. We studied the influence of varying reward expectancies and compared it with the impact of a temporal gap between the disappearance of the fixation dot and the appearance of the target on the visually guided saccades of two rhesus macaques (Macaca mulatta). We found that increasing reward expectancy increased the probability and decreased the reaction time of express saccades. The latter influence was stronger in the later parts of the reaction time distribution of express saccades, satisfactorily captured by a linear shift model of change in the saccadic reaction time distribution. Although different in strength, increasing reward expectancy and inserting a temporal gap resulted in similar effects on saccadic reaction times, suggesting that these two factors summon the same mechanism to facilitate saccadic reaction times.

Night-time disability glare of constant-light LED traffic monitoring fill light

2021 ◽  
pp. 147715352098226
Author(s):  
X Cai ◽  
L Quan ◽  
J Wu ◽  
Y He
Keyword(s):  
Dynamic Range ◽  
Road Traffic ◽  
Reaction Times ◽  
High Dynamic Range ◽  
Luminance Contrast ◽  
Traffic Monitoring ◽  
Constant Light ◽  
Night Time ◽  
Disability Glare ◽  
Small Targets

Fill light, used to helps cameras capture road traffic conditions at night, can lead to serious visual consequences for drivers. Research on disability glare from LED fill light is scarce and therefore this study explored strategies for controlling disability glare of constant-light LED traffic monitoring fill light. The threshold increment was used as an index to evaluate disability glare. The effective disability glare area of LED traffic monitoring fill light was determined based on high dynamic range technology. According to visual efficacy theory, there is a relationship between disability glare conditions and reaction times. The influencing factors include background luminance, luminance contrast and fill light luminance. The results showed that disability glare was the most intense in a range of 20 m to 30 m in front of LED fill light. To reduce the effect of disability glare on drivers, luminance contrast between small targets and the road surface should be greater than 0.5. The fill light luminance should not be greater than 100,000 cd/m2.

Traffic Signal Color Recognition Is a Problem for Both Protan and Deutan Color-Vision Deficients

2003 ◽  
Vol 45 (3) ◽  
pp. 495-503 ◽  
Author(s):  
David A. Atchison ◽  
Carol A. Pedersen ◽  
Stephen J. Dain ◽  
Joanne M. Wood
Keyword(s):  
Color Vision ◽  
Response Times ◽  
Reaction Times ◽  
Error Rates ◽  
Traffic Signal ◽  
White Background ◽  
Signal Design ◽  
Traffic Light ◽  
Light Signals ◽  
Signal Color

We investigated the effect of color-vision deficiency on reaction times and accuracy of identification of traffic light signals. Participants were 20 color-normal and 49 color-deficient males, the latter divided into subgroups of different severity and type. Participants performed a tracking task. At random intervals, stimuli simulating standard traffic light signals were presented against a white background at 5° to right or left. Participants identified stimulus color (red/yellow/green) by pressing an appropriate response button. Mean response times for color normals were 525, 410, and 450 ms for red, yellow, and green lights, respectively. For color deficients, response times to red lights increased with increase in severity of color deficiency, with deutans performing worse than protans of similar severity: response times of deuteranopes and protanopes were 53% and 35% longer than those of color normals. A similar pattern occurred for yellow lights, with deuteranopes and protanopes having increased response times of 85% and 53%, respectively. For green lights, response times of all groups were similar. Error rates showed patterns similar to those of response times. Contrary to previous studies, deutans performed much worse than protans of similar severity. Actual or potential applications of this research include traffic signal design and driver licensing.

Rolling balance board of adjustable geometry as a tool to assess balancing skill and to estimate reaction time delay

2021 ◽  
Vol 18 (176) ◽  
Author(s):  
Csenge A. Molnar ◽  
Ambrus Zelei ◽  
Tamas Insperger
Keyword(s):  
Reaction Time ◽  
Time Delay ◽  
Feedback Control ◽  
Mechanical Model ◽  
Human Subjects ◽  
Reaction Times ◽  
Physical Parameters ◽  
Stabilizing Feedback Control ◽  
Model Subject ◽  
Balance Board

The relation between balancing performance and reaction time is investigated for human subjects balancing on rolling balance board of adjustable physical parameters: adjustable rolling radius R and adjustable board elevation h . A well-defined measure of balancing performance is whether a subject can or cannot balance on balance board with a given geometry ( R , h ). The balancing ability is linked to the stabilizability of the underlying two-degree-of-freedom mechanical model subject to a delayed proportional–derivative feedback control. Although different sensory perceptions involve different reaction times at different hierarchical feedback loops, their effect is modelled as a single lumped reaction time delay. Stabilizability is investigated in terms of the time delay in the mechanical model: if the delay is larger than a critical value (critical delay), then no stabilizing feedback control exists. Series of balancing trials by 15 human subjects show that it is more difficult to balance on balance board configuration associated with smaller critical delay, than on balance boards associated with larger critical delay. Experiments verify the feature of the mechanical model that a change in the rolling radius R results in larger change in the difficulty of the task than the same change in the board elevation h does. The rolling balance board characterized by the two well-defined parameters R and h can therefore be a useful device to assess human balancing skill and to estimate the corresponding lumped reaction time delay.

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