Effects Of Saccadic Eye Movements Research Articles

570 Utility of Gaze-Control for Real-Time Surgical Training During Minimally Invasive Surgery - a Feasilibility Study of Eye-Tracking Technology

Abstract Aim Training in laparoscopic surgery is limited to observing what the trainee is doing on the screen and reliant on verbal coaching. The idea of a physical pointer onto the screen in real-time to allow for more focused supervision and to improve communication was conceptualised. The study aims to demonstrate the feasibility and identify the challenges of using eye-tracking glasses in producing this digital pointer onto a screen. Method Pupil Core (Pupil Labs GmbH) eye-tracking glasses were used to calibrate the edges of a computer monitor to the pupil tracking cameras (200Hz) and the point-of-view (POV) cameras. Utilising the accompanying open-source Pupil Core software, a red-dot cursor was programmed to display in real-time on an accompanying screen. A video of a simulated laparoscopic cholecystectomy and geometric shapes were displayed onto the screen to demonstrate the technology. Results A red dot pointer was successfully displayed on a screen as an overlay controlled entirely by gaze. It was able to track the edges of shapes and used to point out anatomical structures in a video in real-time. Despite the tester looking away from the screen and leaving the seated position, the glasses were able to recallibrate automatically and work seamlessly after. The saccadic nature of eye movements meant that the tracing lines were not always smooth. Conclusions This study demonstrates that the technology exists to make this feasible. Further optimisation in software design is required to mitigate the effects of saccadic eye movements. Further studies collecting objective data is required to demonstrate a minimum viable product.

Effects of saccadic eye movements on episodic & semantic memory fluency in older and younger participants

ABSTRACT Research has demonstrated that performing a sequence of saccadic horizontal eye movements prior to retrieval facilitates performance on tests of episodic memory. This has been observed in both laboratory tasks of retention and autobiographical memory. To date, the work has centred on performance in younger individuals. This paper extends previous investigations by examining the effects of saccadic eye movements in older persons. Autobiographical episodic and semantic memory fluency was assessed in younger (age range 18–35, mean = 22.50), and older (age range 55–87, mean = 70.35) participants following saccadic (vs. fixation control) manipulations. The main effects of eye movements and age were found for episodic autobiographical memory (greater fluency after eye movements and in younger participants). Semantic autobiographical memory showed a main effect of age (greater fluency in younger participants), whereas general semantic memory showed no effect of age or eye movement. These findings indicate that saccadic horizontal eye movements can enhance episodic personal memory in older individuals. This has implications as a technique to improve autobiographical recollection in the elderly and as an adjunct in reminiscence therapy.

Motor behavior-induced prefrontal cortex activation and episodic memory function

Background The objective of this paper was to evaluate the potential individual and combined effects of acute exercise coupled with bilateral interhemispheric activation on episodic memory function. Six experiments were conducted. Methods Experiment 1 was a within-subject, counterbalanced experiment. Participants completed four visits, including 1) exercise and saccadic eye movements, 2) exercise only, 3) saccadic eye movements only, and 4) no exercise and no saccadic eye movements (control). A word-list memory assessment was employed, including a long-term (20-min delay) memory evaluation. In Experiment 2, we evaluated the effects of saccadic eye movements on prefrontal cortex oxygenation, a proxy for neuronal activity. Similarly, in our third experiment, we evaluated the effects of acute exercise on prefrontal cortex oxygenation. Thus, experiments 2 and 3 were employed to provide mechanistic insights from the results shown in experiment 1. Experiment 4 replicated Experiment 1, but instead of increasing prefrontal cortex activation via saccadic eye movements, we used a fist clenching protocol. Experiment 5 evaluated the effects of fist clenching on prefrontal cortex oxygenation. Results Collectively, these 5 experimental studies showed that acute exercise (Experiment 1), saccadic eye movements (Experiment 1), and fist clenching (Experiment 4) enhanced memory function, and that acute exercise (Experiment 3), saccadic eye movements (Experiment 2) and fist clenching (Experiment 5) all increased prefrontal cortex oxygenation. Experiment 6 demonstrated that prefrontal cortex oxygenation was positively associated with episodic memory function. Conclusion These six experiments suggest that several behaviors, such as acute exercise, saccadic eye movements and fist clenching may improve memory function and may, potentially, do so via increases in prefrontal cortex oxygenation.

Behavioral-induced Prefrontal Cortex Activation And Episodic Memory Function

PURPOSE: Here we evaluated the effects of several behaviors (e.g., acute exercise, fist clenching, and saccades) on episodic memory, and whether prefrontal cortex oxygenation mediated these relationships. Six experiments were conducted to evaluate these direct and indirect effects. METHODS & RESULTS: Experiment 1 was a four-visit, within-subject, counterbalanced randomized controlled experiment. The visits included 1) exercise and saccadic eye movements, 2) exercise only, 3) saccadic eye movements only, and 4) no exercise and no saccadic eye movements (control). A word-list based episodic memory assessment was employed, including a long-term memory evaluation. The RM ANOVA was statistically significant (P=0.01, η2p=0.15), as the number of words recalled at the delay period were, respectively, 7.8 (2.7), 8.1 (2.7), 8.1 (2.3), and 6.6 (2.8). In our second experiment, we evaluated the effects of saccadic eye movements on prefrontal cortex oxygenation (PFC O2Hb), a proxy for neuronal activity. We found a main effect for time over a three-minute period, (P<0.001, η2p=0.31), representing higher oxygenation levels during saccadic eye movement. In our third experiment, we evaluated the effects of acute exercise on PFC O2Hb, which also demonstrated an increase in PFC O2Hb across time, (P=0.04, η2p=0.09). Experiment 4 replicated Experiment 1, but instead of saccadic eye movements, used a fist clenching protocol. The RM ANOVA was statistically significant (P<0.001, η2p=0.46), with memory being significantly better for the exercise only, fist only, and exercise + exercise visit compared to control. Experiment 5 evaluated the effects of fist clenching on PFC O2Hb. Results demonstrated a significant main effect for time, with oxygenation increasing during fist clenching, (P<0.001, η2p=0.35). Experiment 6 demonstrated that PFC oxygenation was statistically significantly positively associated with episodic memory function, in that, for every 1 μM increase in oxygenation during memory encoding, there was a 0.27 increase in the number of words (out of 8) recalled (b=0.27; 95% CI: 0.02, 0.52; p = .03). CONCLUSION These six experiments suggest that several behaviors may improve memory function and may, potentially, do so via increases in PFC O2Hb.

The effect of saccadic eye movements on the sensor-level magnetoencephalogram.

We used a combination of simulation and recordings from human subjects to characterize how saccadic eye movements affect the magnetoencephalogram (MEG). We used simulated saccadic eye movements to generate simulated MEG signals. We also recorded the MEG signals from three healthy adults to 5° magnitude saccades that were vertical up and down, and horizontal left and right. The signal elicited by the rotating eye dipoles is highly dependent on saccade direction, can cover a large area, can sometimes have a non-intuitive trajectory, but does not significantly extend above approximately 30Hz in the frequency domain. In contrast, the saccadic spikes (which are primarily monophasic pulses, but can be biphasic) are highly localized to the lateral frontal regions for all saccade directions, and in the frequency domain extend up past 60Hz. Gamma band saccadic artifact is spatially localized to small regions regardless of saccade direction, but beta band and lower frequency saccadic artifact have broader spatial extents that vary strongly as a function of saccade direction. We have here characterized the MEG saccadic artifact in both the spatial and the frequency domains for saccades of different directions. This could be important in ruling in or ruling out artifact in MEG recordings.

Effects of saccadic eye movements on postural control in older adults.

Effects of saccadic eye movements on postural control in older adults.

Effects of saccadic eye movements on postural control stabilization

Several structures of the central nervous system share involvement in both ocular and postural control, but the visual mechanisms in postural control are still unclear. There are discrepant evidences on whether saccades would improve or deteriorate stabilization of posture. The purpose of this study was to determine the influence of saccadic eye movements on postural control while standing in different basis of support. Twelve young adults stood upright in wide and narrow stances while performing fixation and saccades of low and high frequencies. Body sway was attenuated during saccades. Trunk anterior-posterior sway and trunk total displacement decreased during saccades compared to fixation; higher sway mean frequency in anterior-posterior direction during saccades was observed. Body sway was reduced in wide compared to narrow stance during high frequency saccades. These results indicate that eye movement improves postural stabilization and this effect is stronger in combination of wide stance-high frequency gaze condition.

Effects of saccadic eye movements on visual memory for natural objects

Effects of saccadic eye movements on visual memory for natural objects

Saccadic Eye Movements Modulate Visual Responses in the Lateral Geniculate Nucleus

We studied the effects of saccadic eye movements on visual signaling in the primate lateral geniculate nucleus (LGN), the earliest stage of central visual processing. Visual responses were probed with spatially uniform flickering stimuli, so that retinal processing was uninfluenced by eye movements. Nonetheless, saccades had diverse effects, altering not only response strength but also the temporal and chromatic properties of the receptive field. Of these changes, the most prominent was a biphasic modulation of response strength, weak suppression followed by strong enhancement. Saccadic modulation was widespread, and affected both of the major processing streams in the LGN. Our results demonstrate that during natural viewing, thalamic response properties can vary dramatically, even over the course of a single fixation.

Role of synchrony in contour binding: some transient doubts sustained.

The temporal correlation hypothesis proposes that neurons signal mutual inclusion in complex features, such as extended contours, by phase-locking their firing [C. M. Gray and W. Singer, Proc. Nat]. Acad. Sci. USA 86, 1698 (1989)]. Although this hypothesis remains controversial, a number of recent psychophysical studies have suggested that temporal correlation among features can indeed promote perceptual grouping. In particular, subjects are better at detecting extended visual contours embedded within a field of distractor elements when a small delay is present between a cycling presentation of the contour and the background [Nature 394, 179 (1988)]. We have replicated this finding and examined three potentially confounding factors. First, we controlled local density and used more curved contours composed of bandpass elements to confirm that the effect was associated with contour integration and not with the operation of coarse-scale spatial filters. Second, we minimized the effects of saccadic eye movements (which could combine with the flicker of the asynchronous display to introduce motion cues at the contour location) both by using a fixation marker that was visible only when observers made a saccade (allowing them to reject these trials) and by retinally stabilizing the stimulus. We report that eye movements contribute to the effect. Third, we asked if either visible persistence or transients at the onset and the offset of the asynchronous stimuli might contribute to the effect. We report that the effect is largely abolished by the inclusion of prestimulus and poststimulus masks and is entirely abolished by ramping the contrast of the stimulus on and off. Neither ramping, masking, nor stabilization should specifically disrupt a contour-binding scheme based on temporal synchrony, and we conclude that it is the transient component at the onset and the offset of these stimuli that is responsible for the reported advantage for asynchronous presentation.

The effects of saccadic eye movements on the activity of geniculate relay neurons in the monkey.

Saccadic suppression is the reduced visibility that occurs during saccadic eye movements. Recent psychophysical studies have suggested that this is due to a reduction in responsiveness of magnocellular (M), but not parvocellular (P), cells of the lateral geniculate nucleus. To address this and other phenomena of responsiveness during saccades, we recorded from geniculate neurons in the behaving monkey before, during, and after saccades. Specifically, we measured neuronal responses to a flashing, whole-field illumination. Contrary to the prediction, most M neurons showed pronounced enhancement of visual activity during saccades, whereas such responsiveness of parvocellular (P) neurons was not significantly affected by saccades. We also analyzed the extent to which saccades affected burst firing, which results from activation of a voltage-dependent Ca2+ conductance. We found that both M and P cells displayed a significant suppression of burst firing during saccades. These results do not support the idea that saccadic suppression has an obvious substrate in reduced responsiveness of geniculate cells, but this suppression may be related to an increased visual threshold for detection associated with reduced burst firing.

The effect of saccadic eye-movements on spatial vision

The effect of saccadic eye-movements on spatial vision

Neuronal death of the cancellation theory?

The question of how the brain can construct a stable representation of the external world despite eye movements is a very old one. If there have been some wrong statements of problems (such as the inverted retinal image), other statements are less naive and have led to analytic solutions possibly adopted by the brain to counteract the spurious effects of eye movements. Following the MacKay (1973) objections to the analytic view of perceptual stability, Bridgeman et al. claim that the idea that signals canceling the effects of saccadic eye movements are needed is also a misconception, as is the claim that stability and position encoding are two distinct problems. It must be remembered, however, that what made the theory of “cancellation” formulated by von Holst and Mittelstaedt (1950) so appealing was the clinical observation of perceptual instability following ocular paralysis. Following the concept of corollary discharge, the theory of efference copy had the advantage of simultaneously solving three problems: the stability of the visual world during the saccade, the same visual stability across saccades, and the visual constancy problem of allowing the subject to know where an object in space is.

Saccadic eye movements and the detection of fast-moving gratings.

Experiments are presented in which the effect of saccadic eye movements on the visibility of sinusoidal gratings drifting with velocities between 2 deg/s and 400 deg/s is investigated. The results demonstrate that saccades are highly useful for detecting this class of stimuli. Due to a saccade, otherwise subthreshold stimuli become visible as short, distinct flashes of the seemingly stationary pattern. The paper analyzes in detail the dependence of the amount of facilitation on saccade size and relative direction and isolates the additional effect of saccadic suppression. A simple model is proposed which predicts the experimental findings.

The effect of saccades on threshold perception--a model study.

The effect of saccadic eye movements on threshold perception is investigated theoretically. The proposed model considers eye movements by taking into account the shifting of the stimulus pattern on the retina during the occurrence of an eye movement. Saccades are characterized by high velocity and short duration. These motions cause overshoots in the response of linear filters to certain stimulus patterns. Therefore, the model predicts facilitation effects of saccades in the perception of low spatial frequency patterns and patterns flickering with high temporal frequencies. These results agree with experimentally obtained data presented in a subsequent paper. A simple approach is formulated which approximates the complex shifting function of a saccade by a switching of the pattern.

A quantitative analysis of generation of saccadic eye movements by burst neurons

A quantitative analysis of generation of saccadic eye movements by burst neurons