Search

In visual search tasks, distractors similar to the target can attract our attention and affect the speed of attentional disengagement. The attentional disengagement refers to shifting attention away from stimuli that are not relevant to the task. Previous studies mainly focused on the attentional disengagement of one feature dimension. However, the mechanisms of different feature dimensions on attentional disengagement in single and conjunction visual search remain unclear. In the current study, we adopted the oculomotor disengagement paradigm and used saccade latency as an indicator to explore the effects of different feature dimensions of center stimuli on attentional disengagement. In both single and conjunction feature search tasks, participants began each search by fixating on a center stimulus that appeared simultaneously with search display but would not be the target. Participants were instructed to ensure the first saccade to the target location. In Experiments 1A (single feature search) and 1B (conjunction feature search), we found that the attentional disengagement was significantly delayed or accelerated when center stimuli shared color features with the target or salient distractor, but not in shape feature. Moreover, we found that the difference between the two feature dimensions might be caused by their different search difficulty (Experiment 1C). Therefore, in Experiment 2, we matched the difficulty of searching for color and shape tasks before exploring whether there were differences in the effects of different feature dimensions on attentional disengagement. However, the results in Experiment 2 were similar to those in Experiment 1A, indicating that the different effects of feature dimensions on attentional disengagement were caused by feature asymmetry. Therefore, in Experiment 3, we improved the salient discernibility of shape dimension and matched color search to it. The results showed that although the attentional disengagement was delayed in shape dimension, it was still smaller than that in color dimension. Our results supported that goal-oriented attention sets were the main cause of delayed attentional disengagement. By series of experiments, we found that the utilization of different feature dimensions was associated with task difficulty and the features asymmetry in both single and conjunction visual search. [ABSTRACT FROM AUTHOR]

Two experiments investigated what eye movements can reveal about how we process surprising information and how we update mental models in dynamic and unstructured environments. Participants made saccades to visual targets presented one at a time, radially, around an invisible perimeter. Target locations were normally distributed and shifted at an unannounced point during the task. Trials following the shift were considered surprising and unexpected. These unexpected and surprising events prompted the need to update. Slower saccadic latencies were observed for surprising/unexpected events, perhaps indicative of the need to reorient attention to the unexpected target location. Longer dwell times were observed for events that signaled a change in the distribution. These data show that eye movement metrics provide a reliable indicator of mental model updating when contingencies change even in the absence of explicit change signals. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is a chronic and progressive autoimmune disorder that affects the Central Nervous System (CNS). MS is a clinical diagnosis that is confirmed by MRI, visual evoked potentials, and CSF examination. The objective of the current review and meta-analysis is to evaluate the value of saccadic eye movement abnormalities – particularly saccadic latency – as a diagnostic tool for Multiple Sclerosis. We searched the literature in MEDLINE, PubMed, Web of Science and Cochrane Library from 1st January 1998, through 1st September 2018. Published studies of adult patients who are diagnosed with MS and had VOR testing including saccadic eye movement test, and reporting saccadic latency. We calculated pooled mean differences (MD) and 95% confidence intervals (CI) using a random-effects model for latencies in milliseconds (ms) between MS patients and normal controls. The considerable heterogeneity decided the effect model. Five studies met all inclusion criteria. MS patients had a significantly longer saccadic latency compared to the control group, with 135 MS cases and 126 controls, were included in this meta-analysis. The results indicated that there is a significant increase in saccadic latency in the MS group (MD = 31.99, 95% CI = 14.08, 49.90, p =.0005). Based on current evidence from published studies, Saccadic latency can serve as a diagnostic tool to support the clinical diagnosis of MS. [ABSTRACT FROM AUTHOR]

The gaze direction of another person is an important social cue, allowing us to orient quickly in social interactions. The effect of short-term redirection of visual attention to the same object that other people are looking at is known as the gaze cueing effect. There is evidence that the strength of this effect depends on many social factors, such as the trust in a partner, her/his gender, social attitudes, etc. In our study we investigated the influence of race of face stimuli on the strength of the gaze cueing effect. Using the modified Posner Cueing Task an attentional shift was assessed in a scene where avatar faces of different race were used as distractors. Participants were instructed to fix the black dot in the centre of the screen until it changes colour, and then as soon as possible to make a rightward or leftward saccade, depending on colour of a fixed point. A male distractor face was shown in the centre of the screen simultaneously with a fixed point. The gaze direction of the distractor face changed from straight ahead to rightward or leftward at the moment when colour of a fixed point changed. It could be either congruent or incongruent with the saccade direction. We used face distractors of three race categories: Caucasian (own race faces), Asian and African (other race faces). Twenty five Caucasian participants took part in our study. The results showed that the race of face distractors influence the strength of the gaze cueing effect, that manifested in the change of latency and velocity of the ongoing saccades.

Rigorous behavioral studies made in human subjects have shown that small-eccentricity target displacements are associated with increased saccadic reaction times, but the reasons for this remain unclear. Before characterizing the neurophysiological foundations underlying this relationship between the spatial and temporal aspects of saccades, we tested the triggering of small saccades in the male rhesus macaque monkey. We also compared our results to those obtained in human subjects, both from the existing literature and through our own additional measurements. Using a variety of behavioral tasks exercising visual and nonvisual guidance of small saccades, we found that small saccades consistently require more time than larger saccades to be triggered in the nonhuman primate, even in the absence of any visual guidance and when valid advance information about the saccade landing position is available. We also found a strong asymmetry in the reaction times of small upper versus lower visual field visually guided saccades, a phenomenon that has not been described before for small saccades, even in humans. Following the suggestion that an eye movement is not initiated as long as the visuo-oculomotor system is within a state of balance, in which opposing commands counterbalance each other, we propose that the longer reaction times are a signature of enhanced times needed to create the symmetry-breaking condition that puts downstream premotor neurons into a push-pull regime necessary for rotating the eyeballs. Our results provide an important catalog of nonhuman primate oculomotor capabilities on the miniature scale, allowing concrete predictions on underlying neurophysiological mechanisms. [ABSTRACT FROM AUTHOR]

Amblyopia is a developmental disorder of vision associated with abnormal visual stimulation during early childhood. It is known that amblyopia may affect not only spatial vision parameters but also oculomotor behavior. Several previous studies showed that increased saccadic reaction time (latency) may be present in amblyopic subjects. In our recent work, we have demonstrated that not only amblyopic but also a dominant eye may show increased saccadic latency in strabismic individuals. Since saccadic latency can be considered as a decision time, we have applied LATER (Linear Approach to Threshold with Ergodic Rate) decision model to find out how developmental impairment of visual input affects visual decision-making processes, as well as to verify whether amblyopia affects also the cortical ability to inhibit more primitive, early saccadic responses during our modified delayed saccade task. Ten subjects with strabismic amblyopia and twelve control subjects were examined. As we expected, strabismic amblyopes showed decreased rate of rise of the neural decision signal for all viewing conditions as compared to controls. In addition, the comparison between the strabismic and anisometropic groups revealed that the amblyopic eye in strabismic subjects showed decreased rate of rise of the decision signal as compared to amblyopic eye in anisometropic subjects. Although we speculated that amblyopia may reduce the ability of cortical control and favor more reflexive, early saccadic actions to occur, our findings did not confirm this hypothesis. This study provide further evidence that amblyopia is associated with cortical deficits which affect the cortical decision about saccade initiation. [ABSTRACT FROM AUTHOR]

In the present study, we investigated whether peripheral vision can be used to monitor multiple moving objects and to detect single-target changes. For this purpose, in Experiment 1, a modified multiple object tracking (MOT) setup with a large projection screen and a constant-position centroid phase had to be checked first. Classical findings regarding the use of a virtual centroid to track multiple objects and the dependency of tracking accuracy on target speed could be successfully replicated. Thereafter, the main experimental variations regarding the manipulation of to-be-detected target changes could be introduced in Experiment 2. In addition to a button press used for the detection task, gaze behavior was assessed using an integrated eyetracking system. The analysis of saccadic reaction times in relation to the motor response showed that peripheral vision is naturally used to detect motion and form changes in MOT, because saccades to the target often occurred after target-change offset. Furthermore, for changes of comparable task difficulties, motion changes are detected better by peripheral vision than are form changes. These findings indicate that the capabilities of the visual system (e.g., visual acuity) affect change detection rates and that covert-attention processes may be affected by vision-related aspects such as spatial uncertainty. Moreover, we argue that a centroid-MOT strategy might reduce saccade-related costs and that eyetracking seems to be generally valuable to test the predictions derived from theories of MOT. Finally, we propose implications for testing covert attention in applied settings. [ABSTRACT FROM AUTHOR]

The term amblyopia is used to describe reduced visual function in one eye (or both eyes, though not so often) which cannot be fully improved by refractive correction and explained by the organic cause observed during regular eye examination. This developmental disorder of spatial vision affects about 2-5% of the population and is associated with abnormal visual experience (e.g. anisometropia, strabismus) during infancy or early childhood. Several studies have shown prolongation of saccadic latency time in amblyopic eye. In our opinion, study of saccadic latency in the context of central vision deficits assessment, should be based on central retina stimulation. For this reason, we proposed saccade delayed task. It requires inhibitory processing for maintaining fixation on the central target until it disappears – what constitutes the GO signal for saccade. The experiment consisted of 100 trials for each eye and was performed under two viewing conditions: monocular amblyopic / non-dominant eye and monocular dominant eye. We examined saccadic latency in 16 subjects (mean age 30±11 years) with anisometropic amblyopia (two subjects had also microtropia) and in 17 control subjects (mean age 28±8 years). Participants were instructed to look at central (fixation) target and when it disappears, to make the saccade toward the periphery (10 deg) as fast as possible, either left or the right target. The study results have proved the significant difference in saccadic latency between the amblyopic (mean 262±48 ms) and dominant (mean 237±45 ms) eye, in anisometropic group. In the control group, the saccadic latency for dominant (mean 226±32ms) and non-dominant (mean 230±29 ms) eye was not significantly different.By the use of LATER (Linear Approach to the Threshold with Ergodic Rate) decision model we interpret our findings as a decrease in accumulation of visual information acquired by means of central (affected) retina in subjects with anisometropic amblyopia.

A salient object can attract attention irrespective of its relevance to current goals. However, this bottom up effect tends to be short-lived (e.g. < 150 ms) and it is generally assumed that top down processes such as goals or task instructions operating in later time windows override the effect of salience operating in early time windows. While the majority of studies on visual search and scene viewing comply with the assumptions of top down and bottom up processes operating in different time windows and that the former overrides the latter, we point to some possible anomalies in decision research. To explore these anomalies and thereby test the two key assumptions, we manipulate the salience and valence of one information cue in a decision task. Our analyses reveal that in decision tasks top down and bottom up processes do not operate in different time windows as predicted, nor does the former process necessarily override the latter. Instead, we find that the maximum effect of salience on the likelihood of making a saccade to the target cue is delayed until about 20 saccades after stimulus onset and that the effects of salience and valence are additive rather than multiplicative. Further, we find that in the positive and neutral valence conditions, salience continues to exert pressure on saccadic latency, i.e. the interval between saccades to the target with high salience targets being fixated faster than low salience targets. Our findings challenge the assumption that top down and bottom up processes operate in different time windows and the assumption that top down processes necessarily override bottom up processes. [ABSTRACT FROM AUTHOR]

Objective The effect of altitude on brain function is not yet well understood, nor is the influence of height and speed of ascent. Additionally, the relationship between acute mountain sickness (AMS) symptoms and brain function at altitude is unclear. We hypothesized that a deterioration from baseline measures of brain function occurs after rapid, mechanical ascent to 3459 m and would be less pronounced in persons taking acetazolamide. Methods In this double blind, randomized, placebo-controlled study, 20 healthy volunteers (14 men, 6 women; mean age [±SD] 43 ± 16 years) were alternately allocated to acetazolamide 250 mg or to placebo, taken every 12 hours commencing 3 days before ascent. Prosaccadic and antisaccadic eye movements, heart rate, arterial saturation, and Lake Louise AMS scores were assessed at sea level and 15 to 22 hours after ascent to 3459 m. Results Arterial oxygen saturation was significantly lower in the placebo group compared to the acetazolamide group at altitude (Wilcoxon signed-rank test, median [interquartile range]: acetazolamide vs placebo: 92% [5] vs 85% [5]; P = .007), with no differences in prosaccadic latency, heart rate, or Lake Louise score. No differences in saccadic latencies from baseline to altitude were observed in the placebo group, whereas prosaccadic latencies were significantly longer at altitude with acetazolamide (altitude vs baseline: 153 ms [41] vs 176 ms [52], P = .008). Conclusions Brain function, measured by saccadic eye movements, appears to be unimpaired after rapid ascent to 3459 m. Although acetazolamide improves oxygen saturations, it may worsen prosaccades, possibly indicating adverse effects of acetazolamide on brain function at moderate altitude. [ABSTRACT FROM AUTHOR]

The present study explores the threat bias for fearful facial expressions using saccadic latency, with a particular focus on the role of low-level facial information, including spatial frequency and contrast. In a simple localisation task, participants were presented with spatially-filtered versions of neutral, fearful, angry and happy faces. Together, our findings show that saccadic responses are not biased toward fearful expressions compared to neutral, angry or happy counterparts, regardless of their spatial frequency content. Saccadic response times are, however, significantly influenced by the spatial frequency and contrast of facial stimuli. We discuss the implications of these findings for the threat bias literature, and the extent to which image processing can be expected to influence behavioural responses to socially-relevant facial stimuli. [ABSTRACT FROM AUTHOR]

The term amblyopia is used to describe reduced visual function in one eye (or both eyes, though not so often) which cannot be fully improved by refractive correction and explained by the organic cause observed during regular eye examination. Amblyopia is associated with abnormal visual experience (e.g., anisometropia) during infancy or early childhood. Several studies have shown prolongation of saccadic latency time in amblyopic eye. In our opinion, study of saccadic latency in the context of central vision deficits assessment, should be based on central retina stimulation. For this reason, we proposed saccade delayed task. It requires inhibitory processing for maintaining fixation on the central target until it disappears--what constitutes the GO signal for saccade. The experiment consisted of 100 trials for each eye and was performed under two viewing conditions: monocular amblyopic/non-dominant eye and monocular dominant eye. We examined saccadic latency in 16 subjects (mean age 30 ± 11 years) with anisometropic amblyopia (two subjects had also microtropia) and in 17 control subjects (mean age 28 ± 8 years). Participants were instructed to look at central (fixation) target and when it disappears, to make the saccade toward the periphery (10?) as fast as possible, either left or the right target. The study results have proved the significant difference in saccadic latency between the amblyopic (mean 262 ± 48 ms) and dominant (mean 237 ± 45 ms) eye, in anisometropic group. In the control group, the saccadic latency for dominant (mean 226 ± 32 ms) and non-dominant (mean 230 ± 29 ms) eye was not significantly different. By the use of LATER (Linear Approach to the Threshold with Ergodic Rate) decision model we interpret our findings as a decrease in accumulation of visual information acquired by means of central retina in subjects with anisometropic amblyopia. [ABSTRACT FROM AUTHOR]

Recently, we showed that salience affects initial saccades only in a static stimulus environment; subsequent saccades were unaffected by salience but, instead, were directed in line with task requirements (Siebold, van Zoest, & Donk, PLoS ONE 6(9): e23552, ). Yet multiple studies have shown that people tend to fixate salient regions more often than nonsalient ones when they are looking at images-in particular, when salience is defined by dynamic changes. The goal of the present study was to investigate how oculomotor selection beyond an initial saccade is affected by salience as derived from changing, as opposed to static, stimuli. Observers were presented with displays containing two fixation dots, one target, one distractor, and multiple background elements. They were instructed to fixate on one of the fixation dots and make a speeded eye movement to the target, either directly or preceded by an initial eye movement to the other fixation dot. In Experiment 1, target and distractor differed in orientation contrast relative to the background, such that one was more salient than the other, whereas in Experiments 2 and 3, the orientation contrast between the two elements was identical. Here, salience was implemented by a continuous luminance flicker or by a difference in luminance contrast, respectively, which was presented either simultaneously with display onset or contingent upon the first saccade. The results showed that in all experiments, initial saccades were strongly guided by salience, whereas second saccades were consistently goal directed if the salience manipulation was present from display onset. However, if the flicker or luminance contrast was presented contingent upon the initial saccade, salience effects were reinstated. We argue that salience effects are short-lived but can be reinstated if new information is presented, even when this occurs during an eye movement. [ABSTRACT FROM AUTHOR]

We use simulations to investigate the effect of sampling frequency on common dependent variables in eye-tracking. We identify two large groups of measures that behave differently, but consistently. The effect of sampling frequency on these two groups of measures are explored and simulations are performed to estimate how much data are required to overcome the uncertainty of a limited sampling frequency. Both simulated and real data are used to estimate the temporal uncertainty of data produced by low sampling frequencies. The aim is to provide easy-to-use heuristics for researchers using eye-tracking. For example, we show how to compensate the uncertainty of a low sampling frequency with more data and postexperiment adjustments of measures. These findings have implications primarily for researchers using naturalistic setups where sampling frequencies typically are low.

The aim of the present study was to investigate whether time-dependent biases of oculomotor selection as typically observed during visual search are better accounted for by an absolute-processing-speed account (J. P. de Vries, I. T. C. Hooge, M. A. Wiering, & F. A. J. Verstraten, 2011, How longer saccade latencies lead to a competition for salience. Psychological Science, 22, 9 16-923) or a relative-salience account (e.g., M. Donk, & W. van Zoest, 2008, Effects of salience are short-lived. Psychological Science, 19, 733-739; M. Donk & W. van Zoest, 2011, No control in orientation search: The effects of instruction on oculomotor selection in visual search. Vision Research, 51, 2156-2166). In order to test these two models, we performed an experiment in which participants were instructed to make a speeded eye movement to any of two orientation singletons presented among a homogeneous Set of vertically oriented background lines. One singleton, the fixed singleton, remained identical across conditions, whereas the other singleton, the variable singleton, varied such that its orientation contrast relative to the background lines was either smaller or larger than that of the fixed singleton. The results showed that the proportion of eye movements directed toward the fixed singleton varied substantially depending on the orientation contrast of the variable singleton. A model assuming selection behavior to be determined by relative salience provided a better fit to the individual data than the absolute processing speed model. These findings suggest that relative salience rather than the visibility of an element is crucial in determining temporal variations in oculomotor selection behavior and that an explanation of visual selection behavior is insufficient without the concept of a salience map. [ABSTRACT FROM AUTHOR]

One of possible ways to speed-up the prosaccadic latency examination is applying the target walk paradigm. The authors describe the physiological phenomena involved in carrying such paradigms, which may affect latency time and which should be balanced in this kind of task. Thirteen subjects were examined applying the newly designed target-walk paradigm and for comparison the standard prosaccade task. A significant reduction of the saccadic latency (p < 0.01) was found on average by 21 ms, which probably resulted from an increased saccadic decision urgency forced by the new test design. Another reason can be different ways of capturing of the subject’s attention achieved in this task. [Copyright &y& Elsevier]

Abstract: Data on saccadic latency in patients with Spinocerebellar Ataxia 2 (SCA2) are sparse and contradictory. In order to determine whether saccadic latency is definitely prolonged, identify its possible determinants and evaluate it as disease biomarker we assessed the saccadic latency by electronystagmography in 110 SCA2 patients and their paired controls. Mean saccadic latencies were significantly longer in patients when compared to controls for all tested target displacements. Forty-six percent of SCA2 patients had saccadic latencies above the normal range. Reciprobit plots of saccadic latency demonstrated a skewed distribution in the direction of longer latencies for the patients compared to controls. As saccadic latency increased, the velocity and amplitude of saccades significantly decreased in SCA2 subjects but not in controls. Saccadic latency was not influenced by any demographical, clinical or molecular SCA2 variables, but it showed a significant correlation with the performance of the Stroop test, the verbal fluency test and the Wisconsin Card Sorting Test in SCA2 patients. This paper demonstrated that saccadic latency is prolonged in SCA2 patients and it significantly correlates with the performance of frontal-executive functions, thus this parameter could be a useful biomarker to evaluate the efficiency of future therapeutical options on these dysfunctions. [Copyright &y& Elsevier]

Here we address the shape of the saccadic latency-eccentricity function. Previously it has been proposed that the bowl-shaped nature of this function is a by-product of diminished stimulus representation in the periphery. A direct prediction of this theory is that saccadic latencies in the periphery should be speeded if stimuli are increased in size in proportion to the cortical magnification factor ( M-scaling). Using a target-elicited saccade paradigm, ten subjects were shown M-scaled and unscaled Gaussian targets over a horizontal range of ± 40°. Saccadic latencies increased at an equal rate for peripheral targets regardless of whether targets were M-scaled or not. This suggests that the changes of latency with eccentricity are not a by-product of resources devoted to stimulus representation, but instead are a functional adaptation which takes account of the likelihood of saccades of each amplitude in the natural environment. [ABSTRACT FROM AUTHOR]

Abstract: Strategies of saccadic planning must take into account both the required level of accuracy of the saccades, and the time and resources needed to plan and execute the movements. To determine relationships between accuracy and time, we studied sequences of saccades made to scan a set of stationary targets located at the corners of an imaginary square. Target separation and size varied. The time taken to complete saccadic sequences increased with the required level of precision, in agreement with the classical relationship. This was mainly due to the use of error-correcting secondary saccades, whose frequency increased with target separation and decreased with target size. Increases in the time spent fixating near each target did not increase the accuracy of the next primary saccade in the sequence. Instead, secondary saccades were the principal means of correcting landing errors of primary saccades. The results are consistent with a scanning strategy that discourages careful planning of individual saccades in favor of increasing the rate of saccadic production (i.e., exploration), using secondary saccades as needed to correct saccadic landing errors. [Copyright &y& Elsevier]

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Do irrelevant visual features at fixation influence saccadic latency and direction? In a novel search paradigm, we found that when the feature of an irrelevant item at fixation matched the feature defining the target, oculomotor disengagement was delayed, and when it matched a salient distractor more eye movements were directed to that distractor. Latency effects were short-lived; direction effects persisted for up to 200 ms. We replicated latency results and demonstrated facilitated eye movements to the target when the fixated item matched the target colour. Irrelevant features of fixated items influence saccadic latency and direction and may be important considerations in predicting search behaviour. [ABSTRACT FROM AUTHOR]

Abstract: Researchers have shown that the promptness to initiate a saccade is modulated by countless factors pertaining to the visual context and the task. However, experiments on saccadic eye movements are usually designed in such a way that oculomotor performance is dissociated from the natural role of saccades, namely that of making crucial perceptual information rapidly available for high-resolution, foveal analysis. Here, we demonstrate that the requirement to perform a difficult perceptual judgment at the saccade landing location can reduce saccadic latency (by >15%) and increase saccadic peak velocity. Importantly, the effect cannot be explained in terms of arousal, as latency changes are specific to the location where the perceptual judgement is required. These results indicate that mechanisms for voluntary saccade initiation are under the powerful indirect control of perceptual goals. [Copyright &y& Elsevier]

Saccadic latency is composed of separate sensory and motor processing delays. Therefore, any alteration in the sensory processing should effect the saccadic latency. Because the highest density of benzodiazepine (Bz) binding sites is located in cerebral cortex, sensory processing of stimuli in this cortical area is expected to be substantially effected by administration of Bzs. It is well known that sensory processing of binocular disparity occurs in the cerebral cortical areas and therefore the latency of saccades to stimuli defined by binocular disparity should be substantially affected by Bz intake. In this study, we tested this prediction by comparing the latency of saccadic eye movements for binocular disparity defined stimuli (stereo stimuli) with those for luminance contrast defined stimuli (luminance stimuli), after diazepam or placebo. Eye movements were mainly recorded by use of the magnetic search coil technique, and the study was performed in a randomized, double-blind way. Although diazepam prolonged the latency of saccades for stereo and luminance stimuli, the percentage increases in saccadic latency for the stereo stimuli were significantly larger than those for the luminance stimuli. Saccadic peak velocity, and saccadic amplitude, also significantly decreased after diazepam under conditions of stereo and luminance stimuli. However, there was no significant difference for either saccadic peak velocity or amplitude between the two types of target. The results suggest that the latency of saccades to binocular disparity defined random-dot stimuli could more sensitively reflect the pharmacodynamic effects of Bzs on the cerebral cortex. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis that elementary visuo-motor functions involved in visual scanning, as measured by fixation and saccadic tasks, are better in a group of high-level clay target shooters (N=7) than in a control group (N=8). In the fixation task, subject were told to keep fixation as still as possible on a target for 1 min, both in the presence and absence of distracters. For shooters, time did not have an effect on fixation stability, and they had more stable fixation than controls in the distracters condition. Results indicate a difference between groups on both the temporal span of attention and selective attention. In the saccadic task, subjects were asked to saccade, as fast as possible, towards a peripherally displayed target. Two conditions were used: simple reaction to target onset and discrimination between targets and distracters. Shooters had faster saccadic latency to targets than controls in both conditions. Finally, to evaluate the effect of exercise on saccadic latency, we trained one control subject to saccade to a target displayed at a constant spatial position. At the end of the training, saccadic latency reached a value comparable to that recorded in shooters. Learning was largely retinotopic, not showing transfer to untrained spatial positions. [Copyright &y& Elsevier]

Antisaccade performance was investigated in a sample of 2,006 young males as part of a large epidemiological study investigating psychosis proneness. This report summarizes the effects of task parameters on performance using a sample of 55,678 antisaccade trials collected from a subpopulation of 947 individuals. Neither the amplitude nor the latency of an error prosaccade in the antisaccade task was correlated with the latency of the ensuing corrective antisaccade that almost always followed an error. However, the latency of the corrective antisaccade decreased with increasing stimulus distance. Concerning the effects of specific task parameters, trials with stimuli closer to the central fixation point and trials preceded by shorter fixation intervals resulted in more errors and longer latencies for the antisaccades. Finally, there were learning and fatigue effects reflected mainly in the error rate, which was greater at the beginning and at the end of the 5-min task. We used a model to predict whether an error or a correct antisaccade would follow a particular trial. All task parameters were significant predictors of the trial outcome but their power was negligible. However, when modeled alone, response latency of the first movement predicted 40% of errors. In particular, the smaller this latency was, the higher the probability of an error. These findings are discussed in light of current hypotheses on antisaccade production mechanisms involving mainly the superior colliculus. [ABSTRACT FROM AUTHOR]

Humans usually perform about 3-4 saccades per second; hence, precision as well as latency and velocity of these fast eye movements are of crucial importance for analyzing complex and fast changing visual scenes, for example in traffic. Since visual performance is known to slowly decline with age, we investigated the effect of age on the most important characteristics of visually guided saccades. This investigation on age dependence of visually guided saccades included, for the first time, the gap condition, where the old fixation point disappears before the new one appears, allowing subjects to prepare for a saccade. Saccadic latencies and intersaccadic intervals increased with age, while their peak velocities and gains decreased, especially for threshold-adjusted luminance of the targets. The gap condition, however, improved reaction times (latencies) most pronounced in the older age groups, bringing performance for these groups close to the performance level of the young groups. This indicates that the slowing down of saccadic reaction times with age is not predominantly a motor problem, but, according to a common interpretation of the gap effect, a problem of disengaging attention from the old fixation spot. [ABSTRACT FROM AUTHOR]

The difference between simple and choice manual reaction time (RT) has been taken to be a measure of the time necessary for various cognitive operations. In contrast, simple and choice saccadic latencies (SL – time elapsing from stimulus onset to saccade initiation) are quite similar, suggesting that such responses may be more automated. In the present investigation, SL and saccadic reaction times (SR – time elapsing from stimulus onset to saccade completion) were measured for targets appearing in the same and different locations, and to different ends of compound stimuli (big arrows) composed of small elements (little arrows) using either the global figure or the local elements as indicators of required saccade direction. In addition, measures of sequence learning were obtained behaviorally over iterative trials (decreases in response time) and with post-test interrogation. The results indicated that local response times were significantly slower than choice or global response times. Both global precedence and consistency effects were observed. Robust sequence learning was observed under the local condition, but only in the choice condition were all subjects able to recall the sequence correctly. These results are discussed in terms of proposed models of visual perception and saccade generation based on parallel processing. [ABSTRACT FROM AUTHOR]

Recent neurophysiological studies of the saccadic ocular motor system have lent support to the hypothesis that this system uses a motor error signal in retinotopic coordinates to direct saccades to both visual and auditory targets. With visual targets, the coordinates of the sensory and motor error signals will be identical unless the eyes move between the time of target presentation and the time of saccade onset. However, targets from other modalities must undergo different sensory-motor transformations to access the same motor error map. Because auditory targets are initially localized in head-centered coordinates, analyzing the metrics of saccades from different starting positions allows a determination of whether the coordinates of the motor signals are those of the sensory system. We studied six human subjects who made saccades to visual or auditory targets from a central fixation point or from one at 10° to the right or left of the midline of the head. Although the latencies of saccades to visual targets increased as stimulus eccentricity increased, the latencies of saccades to auditory targets decreased as stimulus eccentricity increased. The longest auditory latencies were for the smallest values of motor error (the difference between target position and fixation eye position) or desired saccade size, regardless of the position of the auditory target relative to the head or the amplitude of the executed saccade. Similarly, differences in initial eye position did not affect the accuracy of saccades of the same desired size. When saccadic error was plotted as a function of motor error, the curves obtained at the different fixation positions overlapped completely. Thus, saccadic programs in the central nervous system compensated for eye position regardless of the modality of the saccade target, supporting the hypothesis that the saccadic ocular motor system uses motor error signals to direct saccades to auditory targets. [ABSTRACT FROM AUTHOR]

The mechanical features, electronics, and functional capabilities of the variable-stimulus arc are presented. The arc is a useful tool for studying saccadic refixational eye movements under a variety of experimental conditions. [ABSTRACT FROM AUTHOR]

Directing gaze towards auditory events is a natural behavior. In addition to the well-known accuracy of auditory elicited gaze responses for normal binaural listening, their latency is a measure of possible clinical interest and methodological importance. The aim was to develop a clinically feasible method to assess sound localization latency (SLL), and to study SLL as a function of simulated unilateral hearing loss (SUHL) and the relationship with accuracy. Eight healthy and normal-hearing adults (18–40 years) participated in this study. Horizontal gaze responses, recorded by non-invasive corneal reflection eye-tracking, were obtained during azimuthal shifts (24 trials) of a 3-min continuous auditory stimulus. In each trial, a sigmoid function was fitted to gaze samples. Latency was estimated by the abscissa corresponding to 50% of the arctangent amplitude. SLL was defined as the mean latency across trials. SLL was measured in normal-hearing and simulated SUHL conditions (SUHL 30 and SUHL 43 : mean threshold of 30 dB HL and 43 dB HL across 0.5, 1, 2, and 4 kHz). In the normal-hearing condition, the mean ± SD SLL was 280 ± 40 ms (n = 8) with a test-retest SD = 20 ms. A linear mixed model showed a statistically significant effect of listening condition on SLL. The SUHL 30 and SUHL 43 conditions revealed a mean SLL of 370 ± 49 ms and 540 ± 120 ms, respectively. Repeated measures correlation analysis showed a clear relationship between SLL and the average sound localization accuracy (R 2 = 0.94). The rapid and reliable method to obtain SLL may be an important clinical tool for evaluation of binaural processing. Future studies in clinical cohorts are needed to assess whether SLL may reveal information about binaural processing abilities beyond that afforded by sound localization accuracy. • Sound localization latency can be reliably and rapidly measured by gaze responses. • The latency increases systematically with increased simulated unilateral hearing loss. • Latency and accuracy are strongly associated across degrees of the simulated loss. [ABSTRACT FROM AUTHOR]