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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.

Zusammenfassung Sakkaden sind schnelle Augenbewegungen, die es uns erlauben, unseren Blick auf Objekte unseres Interesses auszurichten und diese Objekte dadurch einer visuellen Detailanalyse zu unterziehen. Die Anatomie und Physiologie des sakkadischen Systems wurde umfangreich charakterisiert, so dass es gerne als Modellsystem herangezogen wird, um die neuronalen Mechanismen der Bewegungskontrolle zu studieren. Das prazise Wissen um die funktionelle Organisation des sakkadischen Systems wiederum liefert wertvolle topodiagnostische und systemphysiologische Informationen bei der neurologischen Untersuchung. Die vorliegende Arbeit gibt einen Uberblick uber die Anatomie und Physiologie des sakkadischen Systems, die klinische und labortechnische Untersuchung von Sakkaden sowie typische klinische Befundkonstellationen.

The remote distractor effect is a robust finding whereby a saccade to a lateralised visual target is delayed by the simultaneous, or near simultaneous, onset of a distractor in the opposite hemifield. Saccadic inhibition is a more recently discovered phenomenon whereby a transient change to the scene during a visual task induces a depression in saccadic frequency beginning within 70 ms, and maximal around 90-100 ms. We assessed whether saccadic inhibition is responsible for the increase in saccadic latency induced by remote distractors. Participants performed a simple saccadic task in which the delay between target and distractor was varied between 0, 25, 50, 100 and 150 ms. Examination of the distributions of saccadic latencies showed that each distractor produced a discrete dip in saccadic frequency, time-locked to distractor onset, conforming closely to the character of saccadic inhibition. We conclude that saccadic inhibition underlies the remote distractor effect.

SummaryOne popular and fruitful approach to understanding what influences the decision of where to look next has been to present targets in a series of trials either to the right or left of a central fixation point and examine sequential effects on saccadic latency [1–3]. However, there is a problem with this paradigm: Every saccade to a target is necessarily followed by an equal and opposite movement back to the center, yet the potentially confounding influence of this refixation saccade is rarely considered. Here, we introduce a novel random-walk paradigm that eliminates this difficulty. Each successive target appears to the left or right of the previous one, allowing us to study long sequences of saccades uncontaminated by refixations. This exposes a new stimulus-history effect, which is remarkably prolonged and relates primarily to movement direction: A saccade reduces the latency for subsequent movements made in the same direction and retards those in the opposite direction. Although in conventional refixation paradigms this effect cancels out, it is of particular significance in the real world—where our fixation point shifts constantly with the object of interest—and reflects a prediction of the way that real objects typically move.

This study aimed to investigate the repeatability and reliability of saccadic latency and fixation stability as a function of sighting-dominance and contact lens wear. Eye movements were recorded in 12 healthy adults who performed a pro- saccade and a fixation task in four conditions; baseline, retest, non-sighting eye viewing and plano contact lens wear. The re-sults showed that saccadic latency and fixation stability (indexed via logBCEA) have good internal consistency, reliability and repeatability, which are not influenced by sighting- dominance or contact lens wear. For standard deviation of eye position, internal consistency was low to moderate. The results also indicated that the non-sighting eye is slightly less stable than the sighting eye and that wearing a contact lens decreases precision.

Because the time to respond to a stimulus depend markedly on expectation, measurements of reaction time can, conversely, provide information about the brain's estimate of the probability of a stimulus. Previous studies have shown that the quantitative relationship between reaction time and static, long-term expectation or prior probability can be explained economically by the LATER model of decision reaction time. What is not known, however, is how the neural representation of expectation changes in the short term, as a result of immediate cues. Here, we manipulate the foreperiod—the delay between the start of a trial and the appearance of the stimulus—to see how saccadic latency, and thus expectation, varies with different delays. It appears that LATER can provide a quantitative explanation of this relationship, in terms both of average latencies and of their statistical distribution. We also show that expectancy appears to be subject to a process of low-pass filtering, analogous to the spatial blur that degrades visual acuity.

In the global effect, saccades are displaced towards a distractor if the latter is near to the target, an effect thought to reflect spatial averaging in neurons of the superior colliculus. The temporal dynamics of the global effect have not been well studied, however. We had twelve subjects perform horizontal saccades to a target in trials in which there were either no distractor or a distractor stimulus located 20° above or below the target. The distractor appeared either simultaneously with the target or preceded it by an interval of between 100 and 800 ms, and was either flashed for only 100 ms or remained visible until the subject responded with a saccade. Both flashed and persistent distractors reduced saccadic latency if they preceded target onset, indicating that subjects could use this cue to prepare saccades in advance. Saccadic endpoint was displaced towards a flashed distractor only if it was simultaneous with the target. However, persistent distractors produced a global effect for both simultaneous presentation and distractor-target intervals of 100 ms, but not for longer intervals. We conclude that the global effect requires of the distractor both a recent onset and persistence of the distractor, and that distractor-related activity decays rapidly within 300 ms.

The eye movement system is sensitive to reward. However, whilst the eye movement system is extremely flexible, the extent to which changes to oculomotor behavior induced by reward paradigms persist beyond the training period or transfer to other oculomotor tasks is unclear. To address these issues we examined the effects of presenting feedback that represented small monetary rewards to spatial locations on the latency of saccadic eye movements, the time-course of learning and extinction of the effects of rewarding saccades on exogenous spatial attention and oculomotor inhibition of return. Reward feedback produced a relative facilitation of saccadic latency in a stimulus driven saccade task which persisted for three blocks of extinction trials. However, this hemifield-specific effect failed to transfer to peripheral cueing tasks. We conclude that rewarding specific spatial locations is unlikely to induce long-term, systemic changes to the human oculomotor or attention systems.

We use eye movements constantly to gather information. Saccades are efficient when they maximize the information required for the task, however there is controversy regarding the efficiency of eye movement planning. For example, saccades are efficient when searching for a single target (Nature, 434 (2005) 387–391), but are inefficient when searching for an unknown number of targets in noise, particularly under time pressure (Vision Research 74 (2012), 61–71). In this study, we used a multiple-target search paradigm and explored whether altering the noise level or increasing saccadic latency improved efficiency. Experiments used stimuli with two levels of discriminability such that saccades to the less discriminable stimuli provided more information. When these two noise levels corresponded to low and moderate visibility, most observers did not preferentially select informative locations, but looked at uncertain and probable target locations equally often. We then examined whether eye movements could be made more efficient by increasing the discriminability of the two stimulus levels and by delaying the first saccade so that there was more time for decision processes to influence the saccade choices. Some observers did indeed increase the proportion of their saccades to informative locations under these conditions. Others, however, made as many saccades as they could during the limited time and were unselective about the saccade goal. A clear trend that emerges across all experiments is that conditions with a greater proportion of efficient saccades are associated with a longer latency to initiate saccades, suggesting that the choice of informative locations requires deliberate planning.

Saccades are necessary for optimal vision. Little is known about saccades in children. We recorded saccades using an infrared eye tracker in 39 children, aged 8-19 years. Participants made saccades to visual targets that stepped 10 degrees or 15 degrees horizontally and 5 degrees or 10 degrees vertically at unpredictable time intervals. Saccadic latency decreased significantly with increasing age, while saccadic gain and peak velocity did not vary with age. Saccadic gains and peak velocities in children are similar to reported adult values. This implies maturity of the neural circuits responsible for making saccades accurate and fast. Saccade latency decreases as the brain matures.

Summary.-The purpose of the study was to investigate saccadic latency and percentage of express saccades involved in predictable tasks between skilled and novice ball players. Participants performed four different tasks, including time and direction unpredictable task, time predictable task, direction predictable task, and time and direction predictable task at the visual angles of 10 and 20". Skilled ball players had shorter mean saccadic latency than novice players on direction and time and direction predictable tasks. The percentage of express saccades of skilled ball players was higher than that of novice players on the latter. Saccadic latency was shorter in the 10" condition in time and direction unpredictable task and time predictable task than for 20". These results suggested that predictive ability might be one of the general characters distinguishing skilled ball athletes from novices in visuomotor performance. The prediction might reduce the mean difference in the saccadic latency at various visual angles. In sport-specific conditions, athlete's performances are usually superior in complex visuomotor performance compared with that of nonathletes. It is well known that athletes respond more quickly and accurately than nonathletes. Visual search behavior in ball sports plays an important role in picking up the necessary information to guide right actions. In particular, the visual prediction system in ball games plays a crucial role in guiding the athlete's search for essential information basic to their skilled responses. Many researchers showed that skilled ball athletes displayed more appropriate and efficient visual search strategies than their novice counterparts. Williams and Davids (1998) examined the importance of using a movement-based response paradigm to examine prediction in sport. Skilled and novice soccer defenders viewed 1-on-1 and 3-on-3 offensive sequences on a large video projection screen. Analysis showed that skilled soccer players were quicker at responding. The reaction time paradigm has also been used successfully in badminton (Abernethy & Russell, 1987), baseball (Paull & Glencross, 1997), basketball (Tenenbaum, Stewart, & Sheath, 1999), tennis (Tenenbaum, Levi-Kolker, Sade, Lieberman, & Lidor, 1996), and volleyball (Handford & Wil

Many factors influence how long it takes to respond to a visual stimulus. The lowest-level factors, such as luminance and contrast, determine how easily different elements of a target can be detected. Higher-level factors are to do with whether these elements constitute a stimulus requiring a response; they include prior probability and urgency. It is natural to think of these two processes, detection and decision, as occurring in series, so that overall reaction time is essentially the sum of the contributions of each stage. Here, measurements of saccadic latency to visual targets whose contrast and prior probability are systematically manipulated demonstrate that there are indeed separable stages of detection and decision. Both can be quantitatively described by rise-to-threshold mechanisms; the average rate of rise of the first is a simple logarithmic function of target contrast, whereas the second shows the linear rise characteristic of the LATER model of neural decision making. The implication is that under normal, high-contrast conditions, in which detection is very fast, the random variability that is characteristic of all reaction times is not caused by sensory noise but is gratuitously introduced by the brain itself; paradoxically, by conferring unpredictability it may aid an organism's survival.

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.

We investigated the effects of a low concentration of sevoflurane on a saccadic eye movement task that reflects the performance of higher neural decision and control mechanisms. The experiments were performed double-blind in five subjects, using either 0.15% end-tidal sevoflurane in oxygen, or pure oxygen as a placebo. Saccades were recorded and analysed using a computer-based recording system that also controlled the presentation of visual targets. Administration of oxygen produced no significant change in median latency compared with breathing air; but in four of the five subjects, administration of sevoflurane in oxygen caused a significant increase in latency. These results suggest that measurement of median saccadic latency may be a useful functional measurement of impairment of performance during recovery from anaesthesia.

Previous studies have shown that the retinal eccentricity of target stimuli has surprisingly little effect on the latency of visually driven saccades. But up until now researchers have addressed this issue by presenting saccadic targets in an unstructured visual field. This contrasts with everyday vision in which eye movements are initiated to stimuli within a cluttered environment. The present experiment compared latencies for target onsets in an empty visual field with a condition in which continuously illuminated location markers "tagged" the possible target locations. Previous reports of no effect of eccentricity on latencies in an unstructured field were replicated. However, a significant effect of eccentricity was found when location markers were used. Interestingly this did not reflect a lengthening of latencies as would be predicted by a reduction in target discriminability. Instead, latencies were relatively facilitated to near-visual onsets in the location marker condition. It is concluded that under more natural viewing conditions the latency of saccades is likely to be modulated by the eccentricity of target stimuli. This effect can be explained by competitive attentional interactions in saccade target selection processes.

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.

International audience; The objective was to explore how face exploration affects postural control in healthy children. The novelty here is that eye movements and posture were simultaneously recorded. Three groups of children participated in the study: 12 children of 7.8±0.5 years old, 13 children of 10.4±0.5 years old and 12 children of 15.7±0.9 years old. Eye movements were recorded by video-oculography and postural stability was recorded by a platform. Children were invited to explore five emotional faces (neutral, happy, sad fear and angry). Analysis of eye movements was done on saccadic latency, percentage of exploration time spent and number of saccades for each specific region of interest (ROI): eyes, nose and mouth. Analysis of posture was made on surface area, sway length and mean velocity of the center of pressures (CoP). Results showed that visual strategies, exploration and postural control develop during childhood and adolescence. Indeed, after nine years-old, children started to look the eyes ROI firstly, then the nose ROI and finally the mouth ROI. The number of saccades decreased with the age of children. The percentage of exploration time spent in eyes ROI was longer than the others ROIs and greater for unpleasant faces (sad, fear and angry) with respect to pleasant emotional face (happy). We found that in front of sad and happy faces the surface area of the CoP was significantly larger compared to other faces (neutral and angry). These results suggest that visual strategies and postural control change during children's development and can be influenced by the emotional face.

The passage of time can be estimated either explicitly, e.g. before leaving home in the morning, or implicitly, e.g. when catching a flying ball. In the present study, the latency of saccadic eye movements was used to evaluate differences between implicit and explicit timing. Humans were required to make a saccade between a central and a peripheral position on a computer screen. The delay between the extinction of a central target and the appearance of an eccentric target was the independent variable that could take one out of four different values (400, 900, 1400 or 1900 ms). In target trials, the delay period lasted for one of the four durations randomly. At the end of the delay, a saccade was initiated by the appearance of an eccentric target. Cue&target trials were similar to target trials but the duration of the delay was visually cued. In probe trials, the duration of the upcoming delay was cued, but there was no eccentric target and subjects had to internally generate a saccade at the estimated end of the delay. In target and cue&target trials, the mean and variance of latency distributions decreased as delay duration increased. In cue&target trials latencies were shorter. In probe trials, the variance increased with increasing delay duration and scalar variability was observed. The major differences in saccadic latency distributions were observed between visually-guided (target and cue&target trials) and internally-generated saccades (probe trials). In target and cue&target trials the timing of the response was implicit. In probe trials, the timing of the response was internally-generated and explicitly based on the duration of the visual cue. Scalar timing was observed only during probe trials. This study supports the hypothesis that there is no ubiquitous timing system in the brain but independent timing processes active depending on task demands.

We investigated coordinated saccadic eye and head movements following predictive horizontal visual targets at +/- 30 degrees by applying transcranial magnetic stimulation (TMS) over the cerebellum before the start of the gaze movement in 10 young subjects. We found three effects of TMS on eye-head movements: 1. Saccadic latency effect. When stimulation took place shortly before movements commenced (75-25 ms before), significantly shorter latencies were found between predictive target presentation and initiation of saccades. Eye latencies were significantly decreased by 45 ms on average, but head latencies were not. 2. Gaze amplitude effect. Without TMS, for the 60 degrees target amplitudes, head movements usually preceded eye movements, as expected (predictive gaze type 3). With TMS 5-75 ms before the gaze movement, the number of eye movements preceding head movements by 20-50 ms was significantly increased (p0.001) and the delay between eye and head movements was reversed (p0.001), i.e. we found eye-predictive gaze type 1. 3. Saccadic peak velocity effect. For TMS 5-25 s before the start of head movement, mean peak velocity of synkinetic eye saccades increased by 20-30% up to 600 degrees/s, compared to 350-400 degrees/s without TMS. We conclude that transient functional cerebellar deficits exerted by means of TMS can change the central synkinesis of eye-head coordination, including the preprogramming of the saccadic pulse and step of a coordinated gaze movement.

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.

Building upon the finding that athletes have faster saccadic eye movements than controls (Lenoir et al., Percept Motor Skills 2000;91:546-552), the aim of this study was to compare prosaccadic and antisaccadic eye movements in table tennis players of different levels. Saccadic latency, error rate, and reaction time on a visuomotor task (key press) were measured. Saccadic latency and error rate did not decrease with an increasing level of expertise. Finger reaction times correlated positively with antisaccadic latencies, but not with prosaccadic latencies. It is concluded that in an active population, saccadic performance does not allow the discrimination between recreational, moderate, and top players because of a ceiling effect. The relation between eye and finger movements is discussed in the framework of common brain areas during movement preparation.

In order to investigate the role of mental rotation in the directional control of eye movements, we instructed subjects to make saccades in directions different from that of a visual stimulus (rotated saccades). Saccadic latency increased linearly with the amount of directional transformation imposed between the stimulus and the response. This supports the hypothesis that reorienting a saccade is accomplished through a mental rotation process. No differences were found in amplitude, duration, velocity, and curvature between rotated and visually guided saccades. Analogous to mental rotation tasks involving reaching arm movements, it is surmised that frontal/prefrontal cortical structures participate in rotated saccades by reorienting the intended saccadic direction. A linear increase in response time with the imposed directional transformation was also found in an analogous mental task not requiring a directed motor response, namely, mentally localizing a point in space at a certain angle from a stimulus direction. However, the speed of mental rotation was systematically lower than in the rotated saccade task. These findings indicate that mental rotation is a rather general mechanism through which directional transformations are achieved.

Saccades were elicited in 30 schizophrenic patients before medication, in 17 of them during medication with neuroleptics, and in 12 healthy controls using six paradigms that tested different types of saccades: (a) the externally triggered and visually guided saccades; (b) the externally triggered and internally guided saccades (anti-saccades); and (c) the internally triggered and internally guided saccades (memory-guided saccades). Latency of the primary saccade, gain (eye amplitude to target amplitude), and percentage of unwanted saccades (fixation suppression errors) were calculated. The externally triggered and externally guided saccades were only slightly affected in the patients, indicating that the function of parieto-tectal pathways was preserved. In contrast, the internally guided and externally triggered saccades showed abnormally long latencies, slightly smaller gains, and an increased rate of suppression errors regardless of the medication status. These findings were even more pronounced in the internally triggered and internally guided saccades such as memory-guided saccades. According to animal experiments and studies on patients with disorders of the basal ganglia, the performance of these saccades is based on the function of the pre- and dorsolateral frontal cortex and its connections to the basal ganglia. The minimal improvement of some of the parameters after clinical improvement and during treatment with neuroleptics suggests that the eye-movement deficits are associated with abnormalities of schizophrenia, which do not basically change under medication with neuroleptics. The observed effects of neuroleptics also argue against a primary abnormality in the dopaminergic input to the frontal cortex – basal ganglia oculomotor loop and support the view that there is a primary disturbance of the cortical input to the oculomotor loop through the basal ganglia in schizophrenics.

The effects of 0.15% quasi-steady-state end-tidal isoflurane on two saccadic eye-movement tests were examined in five volunteers using a newly devised computer-based recording system. The tests were saccadic latency and a countermanding task, the latter being an indicator of the highest levels of conscious performance. A moving light-emitting diode target was displayed on a screen and in the saccadic-latency task the latency of eye movement to the target was measured. In all five subjects the latency increased with anaesthetic by an amount which varied from 8 to 45 ms. This result was significantly different (p

When monkeys interrupt their saccadic scanning of a visual scene to look at a suddenly appearing target, saccades to the target are made after an “express” latency or after a longer “regular” latency. The purpose of this study was to analyze the spatial patterns of scanning, express, and regular saccades. Scanning patterns were spatially biased. Express saccade patterns were biased, too, and were directly correlated with scanning patterns. Regular saccade patterns were more uniform and were not directly correlated with scanning patterns. Express saccades, but not regular saccades, seemed to be facilitated by preparation to scan. This study contributes to a general understanding of how monkeys examine scenes containing both unchanging and suddenly appearing stimuli.

In order to consider the effects of spatial attention on human saccadic eye movements, we analyzed peak velocity, duration, latency and amplitude of saccades during Kanji-recognition tasks. The results suggest that the choice of region allocated for spatial attention has no effect on the characteristics of saccades. The distributions of saccadic latency showed 1 to 3 peaks, and their peak values were consistent with the results of earlier studies. Because of these facts, we consider that there are basic phases for making saccades regardless of the complexity of the tasks. The relation between saccadic latency and amplitude shows that a longer latency leads to a smaller amplitude. This suggests that the state of spatial attention before execution of a saccade affects its amplitude. Based on these results, a schematic model of the brain system for generating of saccades is proposed, and the process of generating saccades is hypothesized using this conceptual model.

Saccades are often elicited in the laboratory by the abrupt step-displacement of a single lit point which is initially the foveolar fixation point and then the eccentric refixation target. This was our Control condition. Four experiments modified the fixation arrangements to examine the effect of altered foveolar stimulation on saccadic latency and accuracy to targets within the central ±6 deg of the visual field. (1) No foveolar fixation point: The subject fixated the empty space midway between a pair of fixation guides, which later collapsed into a single refixation target. Latencies for small saccades were similar to the Control values. (2) No foveolar fixation point and no real refixation target: A pair of fixation guides underwent a yoked displacement, and it was easy to fixate and track the invisible midpoint. The smallest saccades were hypermetric, and the typical pattern of latency variation with retinal eccentricity was exaggerated in scale. (3) Spatial effects of a persistent non-target: The precise position of a non-target was important, latency increases being in the ipsilateral hemifield when the non-target was intrafoveolar and unilateral, bilateral when intrafoveolar and on the midline, and local when the non-target was extrafoveolar. (4) Temporal effects of a foveolar fixation point: Blanking an otherwise persistent fixation point for as little as 1 msec at the time of target presentation reduced the expected latency increase. We conclude that the position and timing of foveolar illumination can be critical for saccades of all sizes. Copyright © 1996 Elsevier Science Ltd.

Various models have been proposed to explain the interplay between bottom-up and top-down mechanisms in driving saccades rapidly to one or a few isolated targets. We investigate this relationship using eye-tracking data from subjects viewing natural scenes to test attentional allocation to high-level objects within a mathematical decision-making framework. We show the existence of two distinct types of bottom-up saliency to objects within a visual scene, which disappear within a few fixations, and modification of this saliency by top-down influences. Our analysis reveals a subpopulation of early saccades, which are capable of accurately fixating salient targets after prior fixation within the same image. These data can be described quantitatively in terms of bottom-up saliency, including an explicit face channel, weighted by top-down influences, determining the mean rate of rise of a decision-making model to a threshold that triggers a saccade. These results are compatible with a rapid subcortical pathway generating accurate saccades to salient targets after analysis by cortical mechanisms.

Aims: The underlying mechanisms of migraine remain poorly understood, partly because we lack objective methods for quantitative analysis of neurological function. To address this issue, we measured interictal saccadic latency in migraineurs and controls. Methods: In a cross-sectional study, we compared interictal saccadic latency distributions of 12,800 saccades in 32 migraineurs with 32 age- and sex-matched controls. Results: The variability of migraineurs’ reaction time distributions was significantly smaller (σ = 1.01 vs. 1.13; p Conclusions: The migraineur’s brain behaves significantly differently from that of a control during the interictal period. By analysing whole distributions, rather than just means, data can be related directly to current neurophysiological models: specifically, the observed decrease in variability suggests a functional deficit in the noradrenergic systems influencing the cerebral cortex. From a clinical perspective, this novel method of characterising neurological function in migraine is more rapid, practicable, inexpensive, objective and quantitative than previous methods such as evoked potentials and transcranial magnetic stimulation, and has the potential both to improve current diagnostic discrimination and to help guide future research into the underlying neural mechanisms.

In 35 healthy regular smokers, visually guided saccades were recorded after a nonsmoking period of at least 90 minutes and a second time within ten minutes after smoking one cigarette, using electro-oculo-graphy (EOG). A dose-related decrease in saccadic reaction time was seen with increasing daily cigarette consumption. This shortening of saccadic latency could result from the general arousal effect of nicotine on several parts of the central nervous system or from a modulation of the inhibitory system involved in saccadic initiation. In spite of this, the expected acute effect of cigarette smoking on saccadic latency time could not be demonstrated. The authors suggest that cigarette smoking exerts in regular smokers a long-term accelerating effect on saccadic latency time, lasting more than 90 minutes.

"Express" saccades, named for their extremely short latencies, occur more frequently in a paradigm with a "gap" in time between the disappearance of the fixation mark and the appearance of the target to be fixated. To explain this result, it has been hypothesized that movements of the eyes are preceded by movements of attention [Posner (1980) Quarterly Journal of Experimental Psychology, 32, 3-25], and that removing the fixation mark allows attention to disengage from the fovea and to be deployed more rapidly to the peripheral target, thus diminishing saccadic latency [Fisher (1987) Reviews of Physiology, Biochemistry and Pharmacology, 105, 1-35]. We measured attention using extra-foveal vernier acuity performance. Our results provide direct evidence supporting the above hypothesis. First, we found that the rise of performance for increasing cue lead times was much faster in the "gap" paradigm. Second, the time function relating gap duration to discrimination performance was remarkably similar to the one relating gap duration and rate of express saccades reported by Mayfrank, Mobashery, Kimmig & Fischer [(1987) European Archives of Psychiatry and Neurological Science, 235, 269-275]. Third, control experiments showed that it was the disappearance of the fixation mark rather than a non-specific warning that led to more rapid shifts of attention and, thus, to better performance. We therefore conclude that the short latencies of "express" saccades may be based on a mechanism involving unusually rapid shifts of attention.

Saccadic latencies are commonly used to study decision mechanisms. For instance, in a random sequence, saccadic latency to a target depends on how frequently it has recently appeared. However, frequency is not the only factor that determines probability. Here we presented targets to the left or right, either in random sequences or in repeating patterns. Although the frequency of appearing on a given side was identical in each case, latencies for the low-frequency side were significantly shorter for repeating patterns than in random sequences, showing that the system can respond to the deterministic probabilities in such patterns. We then disrupted our patterns episodically, recommencing at a random starting position in the sequence. This significantly increased the latency, which remained high until the low-frequency target in the sequence reappeared, implying that the oculomotor system makes strategic use of low-frequency--but high-information--events to determine the phase of repeating sequences. The deterministic sequences of events in our patterns represent a simple model for the habitual sequences of actions commonly performed in daily life, which, when disrupted, require the engagement of a higher level problem-solving strategy to return us to our previous automated sequence as quickly as possible.

There is no evidence that high phenylalanine (Phe) levels have irreversible effects on the adult brain. Many adults with phenylketonuria (PKU) no longer follow a protein-restricted diet. Neuropsychological studies have shown that reaction time in adults with PKU is slower than controls. There are no data to show that this is directly related to Phe levels. Another way to assess reaction time is to measure saccadic latency. We have used a portable, head-mounted saccadometer to measure latency in the outpatient setting. Patients with PKU were split into three groups: off-diet (Phe>1,200 μmol/l), on-diet (Phe

It is known that visual transients prolong saccadic latency and reduce saccadic frequency. The latter effect was attributed to subcortical structures because it occurred only 60–70 ms after stimulus onset. We examined the effects of large task-irrelevant transients on steady-state pursuit and the generation of catch-up saccades. Two screen-wide stripes of equal contrast (4, 20, or 100%) were briefly flashed at equal eccentricities (3, 6, or 12°) from the pursuit target. About 100 ms after flash onset, we observed that pursuit gain dropped by 6–12% and catch-up saccades were entirely suppressed. The relatively long latency of the inhibition suggests that it results from cortical mechanisms that may act by promoting fixation or the deployment of attention over the visual field. In addition, we show that a loud irrelevant sound is able to generate the same inhibition of saccades as visual transients, whereas it only induces a weak modulation of pursuit gain, indicating a privileged access of acoustic information to the saccadic system. Finally, irrelevant changes in motion direction orthogonal to pursuit had a smaller and later inhibitory effect.

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.

Many theories assume that preknowledge of an upcoming target helps visual selection. In those theories, a top-down set can alter the salience of the target, such that attention can be deployed to the target more efficiently and responses are faster. Evidence for this account stems from visual search studies in which the identity of the upcoming target is cued in advance. In five experiments, we show that top-down knowledge affects the speed with which a singleton target can be detected but not the speed with which it can be localized. Furthermore, we show that these results are independent of the mode of responding (manual or saccadic) and are not due to a ceiling effect Our results suggest that in singleton search, top-down information does not affect visual selection but most likely does affect response selection. We argue that such an effect is found only when information from different dimensions needs to be integrated to generate a response and that this is the case in singleton detection tasks but not in other singleton search tasks. © 2010 The Psychonomic Society, Inc.

Can a release of attention from fixation help explain the saccadic 'gap effect', the shortening of saccadic latency (SL) when the fixation spot is extinguished just before saccade target onset? Practiced observers generated SLs and button-presses to one of four 10 degrees eccentric targets in overlap (fixation spot stays on), gap0 (fixation offsets at target onset), and gap200 conditions; in gap200, the fixation spot was removed, dimmed, expanded, or brightened 200ms before target onset. Our data excluded speed-accuracy trade-offs, express saccades, stimulus salience, and oculomotor readiness, while fixation offset and general warning had minor effects, leaving attention release as the default explanation. Supporting this notion, finger-press reactions to foveal probe dots presented after the fixation spot was brightened (to hold attention) were faster than those made after the spot was removed (to release attention). Varying the time from gap onset to the probe dot mapped out the time-course of the putative attentional release, which takes approximately 140ms.

The effect of background layout on visual search performance, and more specifically on the tendency to refixate previously inspected locations and objects, was investigated. Older and younger adults performed a search task in which a background layout or landmark was present or absent in a gaze contingent visual search paradigm. Regardless of age, participants demonstrated fewer refixations when landmarks were present, with older adults showing a larger landmark advantage. This visual search advantage did not come at the cost of saccadic latency. Furthermore, the visual search performance advantage obtained in the presence of a background layout or landmark was observed both for individuals with small and large memory spans.

Aims The aim of this study was to assess the differences in saccadic latency (a measure of time delay experienced in eye movements) between alcohol-dependent and healthy controls. Materials and methods Participants Ninety-nine alcohol dependent patients were examined. Thirty-eight healthy controls were matched to the affected cohort according to demographic characteristics. Assessment In this study we used the Saccadometer Advanced System (Advanced Clinical Instrumentation, Cambridge, UK). The Saccadometer System allows quick and easy collection of saccadic responses within the shortest physiologically possible time (100 saccades in 5 min). The brevity of the testing routine minimizes any potential influence on the results due to fatigue in the test subjects. The eye movement measurements are automated and synchronised with stimuli presentation. This study analyzed saccadic latency and standard deviation of mean latency. Results There was higher saccadic latency and standard deviation of mean latency in alcohol-dependent individuals (224.43±56.24 msec) when compared to healthy controls (187.84±25.65 msec). A marked asymmetry of standard deviation of mean latency between right-sided and left-sided saccades was observed in the affected cohort. There was an increased standard deviation of right-sided saccades mean latency (69.96 msec) in alcohol-dependent individuals when compared to healthy controls (30.93 msec) and also an increased standard deviation of left-sided saccades mean latency (59.33 msec) when compared to healthy controls (33.09 msec). Conclusion It was found that alcohol dependence is associated with impaired (longer time delay) saccadic reaction.

PURPOSE. To investigate saccade dynamics as a function of age to determine whether they follow the pattern of development and decline predicted by Weale's model of aging. METHODS. One hundred ninety-five participants between the ages of 3 and 86 years made visually guided horizontal prosaccades ranging in size from 1° to 60° in response to dot stimuli. Eye movements were recorded binocularly with a video-based eye tracker, sampling at 120 Hz. Saccadic latency, accuracy, and velocity were measured and analyzed as a function of age. RESULTS. Mean saccadic latency decreased from 439 ms at 3 years to 172 ms at 14 years, followed by a period of relative stability to age 50 and finally, gradually increased to 264 ms at ≥80 years. For saccadic accuracy (amplitude gain), there was a statistically significant (P < 0.05) interaction between saccade size and age. Participants made increasingly hypometric saccades as age and saccade size increased. Average age group saccadic asymptotic peak velocity (v max ) increased during childhood from 446 deg/s at age 3, to a peak of 610 deg/s at 14 years and then gradually declined with age to approximately 345 deg/s for participants ≥80 years. CONCLUSIONS. Age affected saccadic latency, accuracy, and velocity. For each parameter there was a different pattern of development and decline probably related to the way in which the portion of the brain that controls each function develops and ages.

This study examined a potential confound in the inverse relationship between target duration and saccadic latency reported by Adam, Ketelaars, Kingma, and Hoek in 1993. Eight participants located a briefly flashed target by moving the eyes and the cursor toward its position in a (backward) mask condition and in a no-mask condition. Analysis showed similar saccadic latencies in both conditions, thereby refuting the potentially confounding role of the backward masking procedure. It is tentatively suggested that the longer saccadic latencies noted for shorter target durations may be associated with delayed accumulation of evidence for the detection of the target.

Purpose: This study evaluated hypothesis that the faster saccadic reaction time in professional clay-target shooters found in a previous study was because of a superiority of athletes arising at the attention level or at level of saccadic motor preparation. Method: Ten shooters with at least 6 yr of shooting training in Olympic shotgun disciplines and 10 control subjects participated in the experiments. In the first experiment, prosaccades were studied by comparing the saccadic latencies obtained from the overlap and gap paradigms. In the overlap paradigm, a target was presented randomly at one of four cardinal positions with the fixation point presented throughout the trial duration. In the gap paradigm, the fixation point was removed at the time of target presentation. In the second experiment, subjects were instructed to saccade as quickly as possible in the direction opposite to that of the target location (antisaccades). Results: Shooters had shorter saccadic latency than controls, both with gap and overlap conditions in the first experiment and in the antisaccade condition of the second experiment. Conclusion: This result indicates that athletes' advantage in saccadic reaction times cannot be attributed to improvement of the attentional mechanism of disengagement. Present results support the hypothesis that shooters develop shorter motor preparation to saccades.

Saccadic eye movements generated in response to a gap paradigm in which the fixation light spot was extinguished 200 ms prior to presentation of the target light spot showed appreciably shorter latencies than for the overlap paradigm in which the target light spot was presented 200 ms prior to extinction of the fixation light spot. When there was unpredictability in the direction of target presentation, i.e., to the left or right of the fixation light spot, the gap paradigm evoked mainly fast regular saccades of peak latency of 155 ms with relatively few express saccades which were defined as having latencies of less than 120 ms. By contrast, when the target always appeared to the right, a substantial population of express saccades with peak latency 95 ms was now generated. There was also a change in the relationship between saccadic latency and target angular displacement which covered the range 5-35 degrees . With the overlap paradigm and unpredictability of target direction, the latencies of the slow regular saccades increased markedly with target angular displacement. This was not the case with the same target direction when the latency of slow regular, fast regular, and express saccades remained constant with increasing target angular displacement. This indicates for targets appearing in the same hemifield that the ocular motor system operates with shortest latency irrespective of target angular displacement.

It has been suggested that the remote distractor effect is the result of nontarget stimulation of a central region representing a collicular fixation zone near the time of target onset. The distributed network of the cells responsible for this effect is believed to extend over a large area, responding to distractors ≤10 deg in the periphery. Several studies also implicate the superior colliculus as the substrate behind an inhibited saccadic response arising from a display change. We investigated this further by using a patch of pink noise of various sizes as a nontarget stimulus. We show that the onset of a small patch (2.3 × 2.3 deg) of centrally displayed pink noise can produce a significant increase in saccadic latency to a simultaneously presented peripheral Gabor target. In contrast, a large patch (36 × 36 deg) of pink noise did not increase latency despite the fact that it also stimulated the region representing the fixation zone. Furthermore, only the large patch of noise facilitated latency when presented before target onset. We also examined the effect of patch sizes between these two extremes and found a steady decrease in latency as patch size increased. This confirms that nontarget stimulation of the region representing the fixation zone near the time of target onset is not in itself sufficient to produce the increase in latency typically found with remote distractors. The results are consistent with the idea that only a spatially confined object leads to a discharge of collicular fixation neurons.

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.

The lateral intraparietal area (area LIP) contains a multimodal representation of extra-personal space. To further examine this representation, we trained rhesus monkeys on the predictive-cueing task. During this task, monkeys shifted their gaze to a visual target whose location was predicted by the location of an auditory or visual cue. We found that, when the sensory cue was at the same location as the visual target, the monkeys' mean saccadic latency was faster than when the sensory cue and the visual target were at different locations. This difference in mean saccadic latency was the same for both auditory cues and visual cues. Despite the fact that the monkeys used auditory and visual cues in a similar fashion, LIP neurons responded more to visual cues than to auditory cues. This modality-dependent activity was also seen during auditory and visual memory-guided saccades but to a significantly greater extent than during the predictive-cueing task. Additionally, we found that the firing rate of LIP neurons was inversely correlated with saccadic latency. This study indicates further that modality-dependent differences in LIP activity do not simply reflect differences in sensory processing but also reflect the cognitive and behavioral requirements of a task.

We compared the timed latencies of saccadic eye movement during isometric contraction of the bilateral and unilateral shoulder girdle elevators in a sitting posture. Muscle contraction force was increased in 10% increments from 0% to 60% of the maximal voluntary contraction (MVC) of each side. Saccadic latency was measured as the latency to the beginning of eye movement toward the lateral target that was moved at random intervals in 20° amplitude jumps. Eye movement was measured using the electro-oculogram technique. During bilateral contraction, saccadic latency decreased until 30% MVC and then began to increase at 40% MVC During unilateral contraction, saccadic latency decreased until 30% MVC in a similar pattern as in bilateral condition, was constant from 30% MVC to 50% MVC, followed by a slight increase at 60% MVC. The saccadic latencies at 10% and 40–60% MVC were significantly shorter during unilateral contraction than bilateral contraction. Thus, the relative force for producing a marked shortening of saccadic latency is observed within a wider range during unilateral contraction than bilateral contraction.