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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...

Objective: This study aimed to identify differences in vestibulo-ocular reflex gain (VOR gain) and saccadic response in the suppression head impulse paradigm (SHIMP) between predictable and less predictable head movements, in a group of healthy subjects. It was hypothesized that higher prediction could lead to a lower VOR gain, a shorter saccadic latency, and higher grouping of saccades.Methods: Sixty-two healthy subjects were tested using the video head impulse test and SHIMPs in four conditions: active and passive head movements for both inward and outward directions. VOR gain, latency of the first saccade, and the level of saccade grouping (PR-score) were compared among conditions. Inward and active head movements were considered to be more predictable than outward and passive head movements.Results: After validation, results of 57 tested subjects were analyzed. Mean VOR gain was significantly lower for inward passive compared with outward passive head impulses (p < 0.001), and it was higher for active compared with passive head impulses (both inward and outward) (p ≤ 0.024). Mean latency of the first saccade was significantly shorter for inward active compared with inward passive (p ≤ 0.001) and for inward passive compared with outward passive head impulses (p = 0.012). Mean PR-score was only significantly higher in active outward than in active inward head impulses (p = 0.004).Conclusion: For SHIMP, a higher predictability in head movements lowered gain only in passive impulses and shortened latencies of compensatory saccades overall. For active impulses, gain calculation was affected by short-latency compensatory saccades, hindering reliable comparison with gains of passive impulses. Predictability did not substantially influence grouping of compensatory saccades.

Objective: This study sought to investigate whether the size of the target used in the horizontal vHIT has an effect on the saccade profile of healthy subjects, and to expand upon previous work linking age to the existence of small vHIT saccades.Methods: 48 participants were recruited between 18 and 77 years of age, with no history of vestibular, oculomotor or neurological conditions and a visual acuity of at least 0.3 LogMAR. Participants underwent four consecutive horizontal vHIT trials using the standard target size and three smaller targets. VOR gain and metrics for saccadic incidence, peak eye velocity and latency were then extracted from results. Results: Target size was a statistically significant influence on saccade metrics. As target size increased, saccadic incidence decreased while peak eye velocity and latency increased. However, a potential order effect was also discovered, and once this was corrected for the remaining effect of target size was small and is likely clinically insignificant. The effect of age was much stronger than target size; increasing age was strongly positively correlated with saccadic incidence and showed a medium size correlation with peak velocity, though not with saccadic latency.Conclusion: While this study suggests that target size may have a statistically significant impact on the vHIT saccade profile of normal subjects, age has a greater influence on the incidence and size of small vHIT saccades.

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.

When exploring the visual environment, one uses saccades to shift gaze and fixation to gather spatially and temporally localized information. We propose that the temporal structure of our environment should constrain the temporal allocation of saccades. Here we probe the possibility of learning to control saccadic latencies in a choice paradigm. Six participants made saccades within 80–300 ms following a target horizontally stepping by 10° between two fixed locations. For each participant we constructed two classes of latencies, “short” and “long,” using the first and last quartiles of the individual baseline distribution (e.g., [80;152] ms and [185;300] ms, respectively). We then concurrently reinforced each class in three blocked conditions across ~60 experimental sessions per participant, using different reinforcement probabilities such that the relative ratio of reinforcement rates for short vs. long latencies was 9/1, 1/9, or 1/1. Latency distributions followed the reinforcement conditions: distributions shifted toward the shorter or longer values or became strongly bimodal. Moreover, the relative rates of short over long latencies matched the relative rates of reinforcers earned for the corresponding latencies (slope up to 0.95), which reveals the ability to choose when to saccade. Our results reveal that learned contingencies considerably affect the allocation of saccades in time and are in line with recent studies on the temporal adjustment of behavior to dynamic environments. This study provides strong evidence for fine operant control of saccadic latency, supporting the hypothesis of a cost-benefit control of saccade latencies.NEW & NOTEWORTHY Saccades may be regarded as an information-foraging behavior mostly concerned with the spatial localization of objects, yet our world is dynamic and environmental temporal regularities should also affect saccade decisions. We present behavioral data from a choice task establishing that humans can learn to choose their saccadic latencies depending on the reinforcement contingencies. This suggests a cost-benefit-based policy that takes into account the learned temporal properties of the environmental contingencies for controlling saccade triggering.

In some industrial inspection processes, multiprocess-handling workers are required to enter the results of visual inspection tests without using their hands because of efficiency or hygiene reasons. We have developed a hands-free visual inspection system by using saccadic latency, a temporal characteristic of saccadic eye movements. The proposed system is free from the Midas touch problem (i.e., the difficulty in developing an eye-typing interface owing to the difficulty in differentiating between intentional blinks and gazes and natural ones). For verifying the system, an experiment was conducted in which ten subjects performed a visual inspection task. The average defect detection rates were 99.4%, and no Midas touch–related errors were observed. Results of the error analysis showed that redesigning the system interface would lead to a further enhancement of the system performance. © 2011 Wiley Periodicals, Inc. © 2012 Wiley Periodicals, Inc.

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.

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 Fitts’s Law (1954) 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

We designed two extensions of Saslow's well-known gap and overlap conditions that require increased voluntary effort because of the progressive elimination of target onsets and fixation point offsets, and obtained repeatable data obeying simple numerical relations. For each of the five stimulus lighting conditions, saccadic latency was measured as a function of the retinal eccentricity or displacement of the target. Latencies were fitted by a serial processing model in which the visually guided minimum tracking latency VGL min is supplemented by two types of delay, dubbed `unlock' and `target', that can be either short or long (`direct' or `indirect'), depending on the conditions. There are two findings: (1) The model has utility. The rank order of saccadic latencies for the five stimulus lighting conditions was constant across all subjects, sessions and eccentricities in the range 7.5 ′ –6° left or right. For pooled data, and the saccadic latency plateau (1–6°), the model was also within ±3 ms of the mean latencies. (2) Latencies of tiny saccades to intrafoveolar stimulation (7.5–45 ′ ) were invariably long in all five stimulus conditions. One factor here must be the experimentally measured local prolongation of VGL min .

We used a countermanding paradigm to investigate the relationship between conflicting cues for controlling human saccades. Subjects made a saccade to a target appearing suddenly in the periphery; but on some trials, after a delay, a stop-signal was presented that instructed subjects to inhibit the saccade. As we increased this delay, subjects increasingly failed to inhibit the movement. From measurements of this relationship, and of saccadic latency in control trials, we estimated the average time needed to inhibit the saccade (the stop-signal reaction time or SSRT). SSRTs were similar across subjects, between 125 and 145 ms, and did not vary with target luminance. We then investigated a race model in which the target initiates a response preparation signal rising linearly with a rate varying randomly from trial to trial, and racing against a similarly rising signal initiated by the cue to inhibit the saccade. The first process to cross a trigger threshold determines whether the saccade is initiated or not. In Monte Carlo simulations, this model correctly predicted the probability of successful saccade inhibition as a function of the stop-signal delay, and also the statistical distributions of saccadic latency during trials in which a stop-signal was presented but the subject failed to inhibit the saccade. These findings provide a comparison to results previously described in the monkey, and show that a simple race model with a linear rise to threshold may underlie behavioural performance in tasks of this kind.

A point light source flickering on and off during a horizontal saccade projects a horizontal array onto the retina. The apparent visual direction of the tail end of the perceived (phantom) array reflects the amount of perisaccadic shift of spatiotopic coordinates that has been completed by the end of the saccade. Four men, saccading 8 degrees to the right across a flashing light, judged the horizontal visual direction of the left (tail) end of the phantom array relative to the left end of a standard 8 degrees array that had projected an image onto the retina before the saccade began. On average, the left ends appeared to be aligned when the last flash in the phantom array was imaged on the retina 7.4 degrees to the right of the image of the left end of the standard array. This result implies that the shift of spatiotopic coordinates is virtually complete by the end of the saccade.

Saccadic latency was studied as a function of the direction of sudden target displacements (steps) and of subsequent smooth target motion (ramps) in Macaca fascicularis. The monkey fixated a central spot that suddenly changed its position and then moved constantly at 10 deg s-1, thus eliciting initial saccades and subsequent pursuit eye movements (recorded by a magnetic search-coil technique). Latencies for initial saccades differed markedly in the vertical axis, being shorter in upward than downward directions for both step and ramp components of target motion. Saccadic latency was also related to the mean pursuit velocity, indicating that the oculomotor system accounts for the direction of step and ramp components of target motion in an integrative way.

The phantom array was used to probe the time course of the shift in retinal local signs that accompanies a saccadic eye movement. The phantom array materializes when one saccades in the dark across a point light source blinking 120 times per second. One sees a stationary array of flashes--the first materializes discretely near the intended endpoint of the saccade, and subsequent flashes materialize progressively closer to the actual position of the blinking light. Four trained observers indicated the perceived location, relative to the phantom array, of a 1-msec marker flash (M) produced by two LEDs (light-emitting diodes) that vertically bracketed the blinking light. The marker was seen as spatially coincident with the first flash when it flashed 80 to 0 msec before the saccade, and was seen as spatially coincident with either the first flash or the actual position of the blinking light when it flashed more than 80 msec before the saccade, indicating, respectively, that the shift is presaccadic and rather abrupt.

Saccadic latencies measured in response to a step-wise displacement of the target may be substantially reduced if a gap separates the offset of the initial fixation point and the onset of the peripheral target. According to Fischer and Ramsperger (1984) this paradigm provokes a bimodal latency distribution which consists of a peak of very fast saccadic responses (express saccades) at about 110 ms and another peak arising from somewhat slower saccades (regular saccades). Using again the gap paradigm, we investigated the effect of an additional go/no-go (i.e. target trial/catch trial) decision on saccadic latencies. The experiments yielded the following results: (i) the distribution between the peaks of express and regular saccades strongly depends on the proportion of catch trials introduced into the trial sequence, which suggests the existence of different modes of operation of the decision processes for express and regular saccades. (ii) The catch trial effect on saccadic latency proved to be a local phenomenon in time: saccades which follow catch trials tend to be slower than those following target trials.

Spasm of fixation, consisting of impaired initiation of saccades in the presence of fixation target, but normal initiation in the absence of a fixation target, was measured in a patient with cerebral hemispheric damage. When a central target was constantly present, the patient made horizontal saccades to the sudden appearance of a second target at very prolonged latencies (mean 369 ms). In the absence of a central fixation target, saccadic latency decreased to normal (197 ms). Extinction of a target for a gap interval elicited very short latency movements (122 ms), termed express saccades. The intervals between self-paced horizontal refixation saccades with the head immobile were prolonged, whereas voluntary refixation saccades with the head free to move occurred at shorter intervals. We postulate that cerebral hemispheric damage may cause spasm of visual fixation by disinhibiting the substantia nigra pars reticulata, thereby inhibiting the superior colliculus.

These experiments show that the smooth-pursuit system responds to changes in contrast in a similar way to the known response of direction-specific mechanisms, suggesting that the smooth-pursuit system uses the signal generated by these mechanisms. Smooth pursuit eye movement velocity and saccadic latency were measured as a function of target contrast in two experiments using ramp target motion between 5 and 40 /sec. In the first experiment, the target velocity was predictable; in the second, it was unpredictable. Smooth pursuit eye velocity in response to predictable ramp targets was independent of target contrast. Saccadic latency decreased dramatically as contrast increased. However, eye velocity in response to unpredictable ramp targets increased with increasing target contrast over a narrow range of contrast (0.3 log units) above contrast threshold and then the response saturated.

Saccadic latency and velocity were measured using bipolar recording of the corneo-retinal potental in 85 subjects aged 20-68. Saccadic latency increased by 0.76% per year with age while saccadic velocity decreased by about 0.25% per year. The normal ranges of saccadic latency and velocity in relation to age have been defined.

Ten adult male subjects participated in an experiment in which they simultaneously visually tracked a jumpwise moving target and identified randomly generated auditory dots and dashes. Results indicated there was both an elimination of discrete saccades and a shortening of eye movement paths. It was also observed that the difficulty of the visual tracking task and the concurrent auditory task showed effects that were not independent of each other. Results could be construed to support both a divided attention and an opponent-process visual processing model.

Subjects in the present experiment made saccadic eye movements to words presented left and right of fixation. The words were presented in the range that approximates the distance covered by the eye during reading. The mean latencies were 30-100 msec shorter than mean fixation durations in reading. Latencies were significantly shorter for left-to-right saccades than for right-to-left saccades. There were also differences in saccadic latency as a function of task demands.

Studies of randomly elicited and predictive eye movements in patients with Parkinson's disease are described. In young normal subjects the peak velocity of predictive saccades (PS) is significantly reduced when compared with equal amplitude randomly elicited saccades (RS). The accuracy of RS, but not of PS, is determined by target amplitude. Thus RS and PS constitute two distinct populations of saccades and their possible differing supranuclear control is discussed. In performing RS Parkinsonian patients (PP) have a small but significantly prolonged latency when compared with age-matched normal controls (NC). During PS these patients show some ability to predict but unlike NC they were unable to further reduce saccadic latency with prior knowledge of the target's predictive pattern. During random (RSP) and predictive (PSP) smooth pursuit PP show a markedly increased phase lag. The ocular motor system of PP seems to have a similar “high level” disturbance to that reported for somato-motor control. Smooth pursuit “efficiency” (assessed as proportion of time actually pursuing) in PP was similar to that for NC but both groups shewed a better performance with the head free. The possible explanation for this is examined.

Using an overlap paradigm to increase the saccadic latency, the undershoot and variability of visually induced saccades has been measured as a function of latency (0.2–0.6 sec) and eccentricity (1–8 deg). The undershoot seems to be caused by a temporal filtering of the visual input (Where-function) and a subject dependent strategy to prevent overshoot above 0.1 deg. Perceptual localization JND has been measured as well for the same eccentricities, durations and subjects. It was considerably smaller than the saccade variability in the same conditions.