The planning of a sequence of saccades in pro- and antisaccade tasks: Influence of visual integration time and concurrent motor processing (original) (raw)
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Object structure and saccade planning
Cognitive Brain Research, 2004
When orienting to a newly appearing display, evidence shows that two saccadic eye movements are often prepared together. By looking the relation between the landing positions of the first and the second saccade, we examine the frame of reference used for the preparation of the second saccade aiming for a new object or exploring within the same object. We demonstrate that the action to be performed on the object affects the coding of the second saccade. A second saccade directed to a new object is coded to aim for a target position on it and is adjusted to the landing position of the first saccade, whereas a second saccade within the same object is coded as a fixed motor vector applied irrespective of the initial landing position on the object.
Human Movement Science, 2004
The present experiment examined the one-target advantage (OTA) with regard to saccadic eye movements. The OTA, previously found with manual pointing responses, refers to the finding that movements are executed faster when the limb is allowed to stop on the target compared to the situation where it has to proceed and hit a second target. Using an adapted limb movement OTA task, saccades of 5°and 15°were made to (a) a single target (one-target), (b) one target and immediately to another target without a change in direction (two-target-extension), and (c) one target and immediately back to the start location (two-target-reversal). Unlike manual movements, the movement times for the initial saccade in the two-target-extension condition were not prolonged compared to either of the other two conditions. Moreover, this pattern of results was found for both the shorter and longer amplitude saccades. The results indicate that the OTA does not occur in the oculomotor system and therefore is not a general motor control phenomenon.
Trans-saccadic processing of visual and motor planning during sequential eye movements
How the brain maintains perceptual continuity across eye movements that yield discontinuous snapshots of the world is still poorly understood. In this study we adapted a framework from the dual task paradigm, well suited to reveal bottlenecks in mental processing, to study how information is processed across sequential saccades. The pattern of RTs allowed us to distinguish among three forms of transsaccadic processing (no trans-saccadic processing, trans-saccadic visual processing, and trans-saccadic visual processing and saccade planning models). Using a cued double-step saccade task we show that even though saccade execution is a processing bottleneck, limiting access to incoming visual information, partial visual and motor processing that occur prior to saccade execution are used to guide the next eye movement. These results provide insights into how the oculomotor system is designed to process information across multiple fixations that occur during natural scanning.
The Concurrent Programming of Saccades
PLOS ONE, 2016
Sequences of saccades have been shown to be prepared concurrently however it remains unclear exactly what aspects of those saccades are programmed in parallel. To examine this participants were asked to make one or two target-driven saccades: a reflexive saccade; a voluntary saccade; a reflexive then a voluntary saccade; or vice versa. During the first response the position of a second target was manipulated. The new location of the second saccade target was found to impact on second saccade latencies and second saccade accuracy showing that some aspects of the second saccade program are prepared in parallel with the first. However, differences were found in the specific pattern of effects for each sequence type. These differences fit well within a general framework for saccade control in which a common priority map for saccade control is computed and the influence of saccade programs on one another depends not so much on the types of saccade being produced but rather on the rate at which their programs develop.
Integration of visual information for saccade production
Human Movement Science, 2011
To foveate a visual target, subjects usually execute a primary hypometric saccade (S1) bringing the target in perifoveal vision, followed by a corrective saccade (S2) or by more than one S2. It is still debated to what extent these S2 are pre-programmed or dependent only on post-saccadic retinal error. To answer this question, we used a visually-triggered saccade task in which target position and target visibility were manipulated. In one-third of the trials, the target was slightly displaced at S1 onset (so-called double step paradigm) and was maintained until the end of S1, until the start of the first S2 or until the end of the trial. Experiments took place in two visual environments: in the dark and in a dimly lit room with a visible random square background. The results showed that S2 were less accurate for shortest target durations. The duration of post-saccadic visual integration thus appears as the main factor responsible for corrective saccade accuracy. We also found that the visual context modulates primary saccade accuracy, especially for the most hypometric subjects. These findings suggest that the saccadic system is sensitive to the visual properties of the environment and uses different strategies to maintain final gaze accuracy.
Between-object and within-object saccade programming in a visual search task
Vision Research, 2006
The role of the perceptual organization of the visual display on eye movement control was examined in two experiments using a task where a two-saccade sequence was directed toward either a single elongated object or three separate shorter objects. In the Wrst experiment, we examined the consequences for the second saccade of a small displacement of the whole display during the Wrst saccade. We found that between-object saccades compensated for the displacement to aim for a target position on the new object whereas withinobject saccades did not show compensation but were coded as a Wxed motor vector applied irrespective of wherever the preceding saccade landed. In the second experiment, we extended the paradigm to examine saccades performed in diVerent directions. The results suggest that the within-object and between-object saccade distinction is an essential feature of saccadic planning.
Bilateral interactions in saccade programming
Experimental Brain Research, 1996
Subjects were required to make a saccade to a target appearing randomly 4 ~ to the left or right of the current fixation position (1280 trials per experiment). Location cues were used to direct visual attention and start saccade preparation to one of the two locations before target onset. When the cue indicated the target location (valid trials), the generation of express saccades (visually guided saccades with latencies around 100 ms) was strongly facilitated. When the opposite location was cued (invalid trials), express saccades were abolished and replaced by a population of mainly fast-regular saccades (latencies around 150 ms). This was found with a peripheral cue independently of whether the fixation point was removed before target onset (gap condition; experiment 1) or remained on throughout the trial (overlap condition; experiment 2). The same pattern also was observed with a central cue that did not involve any visual stimulation at a peripheral location (experiment 3). In the case where the primary saccade was executed in response to the cue and the target appeared at the opposite location, continuous amplitude transition functions were observed: starting at about 60-70 ms from target onset onward, the amplitude of the cue-elicited saccades continuously decreased from 4 ~ to values below 1 ~ The results are explained by a fixation-gating model, according to which the antagonism between fixation and saccade activity gives rise to multimodal distributions of saccade latencies. It is argued that allocation of visual attention and saccade preparation to one location entails a successive disengagement of the fixation system controlling saccade preparation within the hemifield to which the saccade is prepared and a partial engagement of the opposite fixation system.
Role of Supplementary Eye Field in Saccade Initiation: Executive, Not Direct, Control
Journal of Neurophysiology, 2010
Isoda, Masaki and Jun Tanji. Cellular activity in the supplementary eye field during sequential performance of multiple saccades. J Neurophysiol 88: 3541-3545, 2002; 10.1152/jn.00299.2002. To investigate how single neurons in the supplementary eye field (SEF) participate in sequential performance of multiple saccades, we analyzed presaccadic activity while monkeys were performing three saccades in six different orders from memory. The saccades in each sequence were separated by a fixation period and initiated from the same fixation point with intervening return saccades. We found that the majority of the presaccadic activity of the SEF neurons differed significantly depending on the numerical position of saccades in each sequence (rank order). This rank-order selectivity was found in parallel with the selectivity for the sequence of three saccades. Our data suggest a role for SEF neurons in the coding of temporally ordered saccadic eye movements.
The Saccadic system more readily co-processes orthogonal than co-linear saccades
Real-life visual tasks such as tracking jumping objects and scanning visual scenes often require a sequence of saccadic eye movements. The ability of the ocular motor system to parallel process saccades has been previously demonstrated. We recorded the monocular eye movements of five normal human subjects using the magnetic search coil technique in a double step paradigm. Initial target jumps were always purely horizontal or purely vertical. We were interested in the latency to onset of the second saccade as a function of direction in relation to the first saccade. When the inter stimulus interval (ISI) was 150 or 180 ms orthogonal second saccades were of significantly shorter latency than second co-linear saccades. When the ISI was 250 ms the latencies of orthogonal and co-linear second saccades were statistically indistinguishable. Based on these findings it is postulated that the ocular motor system can more readily co-process orthogonal than co-linear saccades.
Vision research, 2010
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.