The Saccadic system more readily co-processes orthogonal than co-linear saccades (original) (raw)
Related papers
Interocular timing differences in the horizontal components of human saccades
Vision Research, 2001
The occurrence of systematic interocular differences in the time of initiation of saccades in various directions was investigated in normal human subjects (n= 4). Saccades were recorded binocularly with scleral sensor coils on each of the eyes with a temporal resolution of 0.1 ms (sampling frequency 10 000 Hz). Analysis was done in the velocity domain after digital differentiation. It was found that, in the initial phase of horizontal saccades, the nasalward moving eye lagged the temporalward moving eye consistently by slightly less than 1 ms. No such difference was found in vertical (upward or downward) saccades. In oblique saccades, the systematic initial lag of the nasalward moving eye was similarly present in the horizontal component of the saccade, but absent in the vertical component. It is postulated that this interocular timing difference in horizontal saccades is due to the additional synaptic delay caused by the abducens internuclear neuron in the pathway to the medial rectus muscle of the eye.
Directional interactions between current and prior saccades
Frontiers in human neuroscience, 2014
One way to explore how prior sensory and motor events impact eye movements is to ask someone to look to targets located about a central point, returning gaze to the central point after each eye movement. Concerned about the contribution of this return to center movement, Anderson et al. (2008) used a sequential saccade paradigm in which participants made a continuous series of saccades to peripheral targets that appeared to the left or right of the currently fixated location in a random sequence (the next eye movement began from the last target location). Examining the effects of previous saccades (n-x) on current saccade latency (n), they found that saccadic reaction times (RT) were reduced when the direction of the current saccade matched that of a preceding saccade (e.g., two left saccades), even when the two saccades in question were separated by multiple saccades in any direction. We examined if this pattern extends to conditions in which targets appear inside continuously mark...
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.
Latency of peripheral saccades
Journal of the Optical Society of America, 1979
Displaying the point of gaze to the observer in addition to a point target provides a secondary visual feedback (2VFB). Eccentric fixation is achieved using a biased 2VFB to yield an experimentally imposed "eccentric fovea." The target is suddenly moved to a new position and the task is to regain it, in the "eccentric fovea." It is found that the pattern of eye-movement response consistently starts with saccadric foveal exploration of the target, but its latency has twice the duration of a regular voluntary saccade. Practice, however, makes for the shortened latency tending asymptotically to the regular saccadic duration.
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.
Brain Research, 2008
Previous studies have shown that a saccade is coded in a specific reference frame according to its goal: to aim for a new object or to explore an object which has already been fixated. In a two saccade sequence, the second saccade aiming for a new object is programmed in a retinocentric reference frame in which the spatial location of the second object is stored in spatial memory before the first saccade and updated after its execution. The second saccade exploring the same object is coded in an oculocentric reference frame in which object size is directly transformed into a fixed motor vector, encoded in motor memory before the first saccade and simply applied after its execution. The integration of parafoveal visual information appears to be crucial in the selection of the appropriate reference frame. The two experiments presented here investigate how and when the saccadic system integrates visual information to plan a sequence of saccades. In separate blocks, subjects were asked to execute a sequence of prosaccades directed toward a single object or two short objects, or to execute a sequence of antisaccades in the opposite direction of the stimuli. The latency of the initial saccade was modulated by using the Gap-200, Gap-0 and Overlap-600 ms paradigms. The results show that the time available for segmenting the visual stimulation into discrete objects and application of a specific reference frame according to this segmentation is critical for saccadic planning.
The initial direction and landing position of saccades
1995
We studied the trajectories of self-paced saccades in two experimental conditions. Saccades were made between two visual targets in one condition and between the same two, not visible, positions in the other condition. Target pairs were presented which required oblique saccades of 20 or 40 deg. At least 200 saccades were made between each pair of targets. Horizontal and vertical eye movements were measured of the right eye with a scleral coil technique. We computed the angle between starting and end point of each primary saccade (effective direction). We also computed the angle between starting point and eye position when the saccade had covered a distance of 2.5 deg (initial direction). We found that variability in initial directions was two to seven times larger than variability in the effective directions. This effect was found in both experimental directions for saccades made in all tested directions. We conclude that curvedness of saccades is the result of a purposeful control strategy. The saccadic trajectories show that, initially, the eye is accelerated roughly in the direction of the target and subsequently is guided to the target. This behavior cannot be described by present models of saccade generation. We suggest that the coupling between saccadic pulse and step signals is not as tight as generally is accepted in the literature.
How Saccade Intrusions Affect Subsequent Motor and Oculomotor Actions
Frontiers in neuroscience, 2016
In daily activities, there is a close spatial and temporal coupling between eye and hand movements that enables human beings to perform actions smoothly and accurately. If this coupling is disrupted by inadvertent saccade intrusions, subsequent motor actions suffer from delays, and lack of coordination. To examine how saccade intrusions affect subsequent voluntary actions, we used two tasks that require subjects to make motor/oculomotor actions in response to a visual cue. One was the memory guided saccade (MGS) task, and the other the hand reaction time (RT) task. The MGS task required subjects to initiate a voluntary saccade to a memorized target location, which is indicated shortly before by a briefly presented cue. The RT task required subjects to release a button on detection of a visual target, while foveating on a central fixation point. In normal subjects of various ages, inadvertent saccade intrusions delayed subsequent voluntary motor, and oculomotor actions. We also studi...
Bimodal saccade distributions and the origin of express saccades
Saccadic reaction times (SRTs) are typically distributed unimodally when subjects are ask to move their eyes from a central fixation to a target as quick as possible after its appearance. If, however, the fixation cue disappears shortly before target onset, then SRT is reduced, and the reduction is often accompanied by splitting of the unimodal distribution into two or more modes. The fastest mode of these rapid eye movements have been termed 'express saccades'. The origin of these fast modes are under considerable discussion. In this paper we show that bimodal distributions with a fast peak of express saccades can have there origin in the way information is processed in the intermediate layer of the superior colliculus.
The influence of stimulus direction and eccentricity on pro- and anti-saccades in humans
Experimental Brain Research, 2007
We examined the sensory and motor inXuences of stimulus eccentricity and direction on saccadic reaction times (SRTs), direction-of-movement errors, and saccade amplitude for stimulus-driven (prosaccade) and volitional (antisaccade) oculomotor responses in humans. Stimuli were presented at Wve eccentricities, ranging from 0.5° to 8°, and in eight radial directions around a central Wxation point. At 0.5° eccentricity, participants showed delayed SRT and increased direction-of-movement errors consistent with misidentiWcation of the target and Wxation points. For the remaining eccentricities, horizontal saccades had shorter mean SRT than vertical saccades. Stimuli in the upper visual Weld trigger overt shifts in gaze more easily and faster than in the lower visual Weld: prosaccades to the upper hemiWeld had shorter SRT than to the lower hemiWeld, and more anti-saccade direction-of-movement errors were made into the upper hemiWeld. With the exception of the 0.5° stimuli, SRT was independent of eccentricity. Saccade amplitude was dependent on target eccentricity for prosaccades, but not for antisaccades within the range we tested. Performance matched behavioral measures described previously for monkeys performing the same tasks, conWrming that the monkey is a good model for the human oculomotor function. We conclude that an upper hemiWeld bias lead to a decrease in SRT and an increase in direction errors.