Saccadic Suppression of Displacement Does Not Reflect a Saccade-Specific Bias to Assume Stability.
Ontology highlight
ABSTRACT:
SUBMITTER: Born S
PROVIDER: S-EPMC6969937 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Processing of visual information in the central (foveal) and peripheral visual field is vastly different. To achieve a homogeneous representation of the visual world across eye movements, the visual system needs to compensate for these differences. By introducing subtle changes between peripheral and foveal inputs across saccades, one can test this compensation. We morphed shapes between a triangle and a circle and presented two different change directions (circularity decrease or increase) at varying magnitudes across a saccade. In a change-discrimination task, observers disproportionally often reported percepts of circularity increase. To test the relationship with visual-field differences, we measured perception when shapes were exclusively presented either in the periphery (before a saccade), or in the fovea (after a saccade). We found that overall shapes were perceived as more circular before than after a saccade and the more pronounced this difference was for a participant, the smaller was their circularity-increase bias in the change-discrimination task. We propose that visual-field differences have a direct and an indirect influence on transsaccadic perception of shape change. The direct influence is based on the distinct appearance of shape in the central and peripheral visual field in a trial, causing an increase of the perceptual magnitude of circularity-decrease changes. The indirect influence is based on long-term build-up of transsaccadic expectations; if a change is opposite (circularity increase) to the expectation (circularity decrease), it should elicit a strong error signal facilitating change detection. We discuss the concept of transsaccadic expectations and theoretical implications for transsaccadic perception of other feature changes.
| S-EPMC7611036 | biostudies-literature
Project description:Humans do not notice small displacements to objects that occur during saccades, termed saccadic suppression of displacement (SSD), and this effect is reduced when a blank is introduced between the pre- and postsaccadic stimulus (Bridgeman, Hendry, & Stark, 1975; Deubel, Schneider, & Bridgeman, 1996). While these effects have been studied extensively in adults, it is unclear how these phenomena are characterized in children. A potentially related mechanism, saccadic suppression of contrast sensitivity-a prerequisite to achieve a stable percept-is stronger for children (Bruno, Brambati, Perani, & Morrone, 2006). However, the evidence for how transsaccadic stimulus displacements may be suppressed or integrated is mixed. While they can integrate basic visual feature information from an early age, they cannot integrate multisensory information (Gori, Viva, Sandini, & Burr, 2008; Nardini, Jones, Bedford, & Braddick, 2008), suggesting a failure in the ability to integrate more complex sensory information. We tested children 7 to 12 years old and adults 19 to 23 years old on their ability to perceive intrasaccadic stimulus displacements, with and without a postsaccadic blank. Results showed that children had stronger SSD than adults and a larger blanking effect. Children also had larger undershoots and more variability in their initial saccade endpoints, indicating greater intrinsic uncertainty, and they were faster in executing corrective saccades to account for these errors. Together, these results suggest that children may have a greater internal expectation or prediction of saccade error than adults; thus, the stronger SSD in children may be due to higher intrinsic uncertainty in target localization or saccade execution.
| S-EPMC7571331 | biostudies-literature
Project description:Introspection makes it clear that we do not see the visual motion generated by our saccadic eye movements. We refer to the lack of awareness of the motion across the retina that is generated by a saccade as saccadic omission [1]: the visual stimulus generated by the saccade is omitted from our subjective awareness. In the laboratory, saccadic omission is often studied by investigating saccadic suppression, the reduction in visual sensitivity before and during a saccade (see Ross et al. [2] and Wurtz [3] for reviews). We investigated whether perceptual stability requires that a mechanism like saccadic suppression removes perisaccadic stimuli from visual processing to prevent their presumed harmful effect on perceptual stability [4, 5]. Our results show that a stimulus that undergoes saccadic omission can nevertheless generate a shape contrast illusion. This illusion can be generated when the inducer and test stimulus are separated in space and is therefore thought to be generated at a later stage of visual processing [6]. This shows that perceptual stability is attained without removing stimuli from processing and suggests a conceptually new view of perceptual stability in which perisaccadic stimuli are processed by the early visual system, but these signals are prevented from reaching awareness at a later stage of processing.
| S-EPMC3254668 | biostudies-literature
Project description:The eye movement system reacts very systematically to visual transients that are presented during the planning phase of a saccade. About 50 to 70 ms after the onset of a transient, the number of saccades that are started decreases, a phenomenon that has been termed saccadic inhibition. Saccades started just before this time window are hypometric compared to regular saccades, presumably because the presentation of the transient stops them in mid-flight. Recent research investigating the properties of repeated saccades to fixed locations found that these early saccades were additionally faster than expected from the main sequence relation, suggesting that a saccadic dead time during which saccades can no longer be modified does not exist. The present study investigated the properties of saccades to random locations in a guided saccade task. As expected, early saccades starting just before the saccadic inhibition dip in frequency were hypometric. Their velocity profiles implied that these saccades were actively stopped after reaching peak velocity. However, the peak velocities of these saccades did not generally deviate from the main sequence relation. The question whether an active stop of early saccades is incompatible with the idea of a saccadic dead time is open to debate.
| S-EPMC5857173 | biostudies-other
Project description:Although our eyes are in constant movement, we remain unaware of the high-speed stimulation produced by the retinal displacement. Vision is drastically reduced at the time of saccades. Here, I investigated whether the reduction of the unwanted disturbance could be established through a saccade-contingent habituation to intra-saccadic displacements. In more than 100 context trials, participants were exposed either to an intra-saccadic or to a post-saccadic disturbance or to no disturbance at all. After induction of a specific context, I measured peri-saccadic suppression. Displacement discrimination thresholds of observers were high after participants were exposed to an intra-saccadic disturbance. However, after exposure to a post-saccadic disturbance or a context without any intra-saccadic stimulation, displacement discrimination improved such that observers were able to see shifts as during fixation. Saccade-contingent habituation might explain why we do not perceive trans-saccadic retinal stimulation during saccades.
| S-EPMC7093108 | biostudies-literature
Project description:Whenever we move our eyes, some visual information obtained before a saccade is combined with the visual information obtained after a saccade. Interestingly, saccades rarely land exactly on the saccade target, which may pose a problem for transsaccadic perception as it could affect the quality of postsaccadic input. Recently, however, we showed that transsaccadic feature integration is actually unaffected by deviations of saccade landing points. Possibly, transsaccadic integration remains unaffected because the presaccadic shift of attention follows the intended saccade target and not the actual saccade landing point during regular saccades. Here, we investigated whether saccade landing point errors can in fact alter transsaccadic perception when the presaccadic shift of attention follows the saccade landing point deviation. Given that saccadic adaptation not only changes the saccade vector, but also the presaccadic shift of attention, we combined a feature report paradigm with saccadic adaptation. Observers reported the color of the saccade target, which occasionally changed slightly during a saccade to the target. This task was performed before and after saccadic adaptation. The results showed that, after adaptation, presaccadic color information became less precise and transsaccadic perception had a stronger reliance on the postsaccadic color estimate. Therefore, although previous studies have shown that transsaccadic perception is generally unaffected by saccade landing point deviations, our results reveal that this cannot be considered a general property of the visual system. When presaccadic shifts of attention follow altered saccade landing points, transsaccadic perception is affected, suggesting that transsaccadic feature perception might be dependent on visual spatial attention.
| S-EPMC7488614 | biostudies-literature
Project description:A perceptual judgment is typically characterized by constructing psychometric and chronometric functions, i.e., by mapping the accuracies and reaction times of motor choices as functions of a sensory stimulus feature dimension. Here, we show that various saccade metrics (e.g., peak velocity) are similarly modulated as functions of sensory cue viewing time during performance of an urgent-decision task. Each of the newly discovered functions reveals the dynamics of the perceptual evaluation process inherent to the underlying judgment. Remarkably, saccade peak velocity correlates with statistical decision confidence, suggesting that saccade kinematics reflect the degree of certainty with which an urgent perceptual decision is made. The data were explained by a race-to-threshold model that also replicates standard performance measures and cortical oculomotor neuronal activity in the task. The results indicate that, although largely stereotyped, saccade metrics carry subtle but reliable traces of the underlying cognitive processes that give rise to each oculomotor choice.
| S-EPMC6060154 | biostudies-literature
Project description:Perceptual stability is facilitated by a decrease in visual sensitivity during rapid eye movements, called saccadic suppression. While a large body of evidence demonstrates that saccadic programming is plastic, little is known about whether the perceptual consequences of saccades can be modified. Here, we demonstrate that saccadic suppression is attenuated during learning on a standard visual detection-in-noise task, to the point that it is effectively silenced. Across a period of 7 days, 44 participants were trained to detect brief, low-contrast stimuli embedded within dynamic noise, while eye position was tracked. Although instructed to fixate, participants regularly made small fixational saccades. Data were accumulated over a large number of trials, allowing us to assess changes in performance as a function of the temporal proximity of stimuli and saccades. This analysis revealed that improvements in sensitivity over the training period were accompanied by a systematic change in the impact of saccades on performance-robust saccadic suppression on day 1 declined gradually over subsequent days until its magnitude became indistinguishable from zero. This silencing of suppression was not explained by learning-related changes in saccade characteristics and generalized to an untrained retinal location and stimulus orientation. Suppression was restored when learned stimulus timing was perturbed, consistent with the operation of a mechanism that temporarily reduces or eliminates saccadic suppression, but only when it is behaviorally advantageous to do so. Our results indicate that learning can circumvent saccadic suppression to improve performance, without compromising its functional benefits in other viewing contexts.
| S-EPMC8018005 | biostudies-literature
Project description:We make fast, ballistic eye movements called saccades more often than our heart beats. Although every saccade causes a large movement of the image of the environment on our retina, we never perceive this motion. This aspect of perceptual stability is often referred to as saccadic suppression: a reduction of visual sensitivity around the time of saccades. Here, we investigated the neural basis of this perceptual phenomenon with extracellular recordings from awake, behaving monkeys in the middle temporal, medial superior temporal, ventral intraparietal, and lateral intraparietal areas. We found that, in each of these areas, the neural response to a visual stimulus changes around an eye movement. The perisaccadic response changes are qualitatively different in each of these areas, suggesting that they do not arise from a change in a common input area. Importantly, our data show that the suppression in the dorsal stream starts well before the eye movement. This clearly shows that the suppression is not just a consequence of the changes in visual input during the eye movement but rather must involve a process that actively modulates neural activity just before a saccade.
| S-EPMC2787621 | biostudies-other
Project description:To establish a perceptually stable world despite the large retinal shifts caused by saccadic eye movements, the visual system reduces its sensitivity to the displacement of visual stimuli during saccades (e.g. saccadic suppression of displacement, SSD). Previous studies have demonstrated that inserting a temporal blank right after a saccade improves displacement detection performance. This 'blanking effect' suggests that visual information right after the saccade may play an important role in SSD. To understand the mechanisms underlying SSD, we here compare the effect of pre- and post-saccadic stimulus contrast on displacement detection during a saccade with and without inserting a blank. Our results show that observers' sensitivity to detect visual displacement was reduced by increasing post-saccadic stimulus contrast, but a blank relieves the impairment. We successfully explain the results with a model proposing that parvo-pathway signals suppress the magno-pathway processes responsible for detecting displacements across saccades. Our results suggest that the suppression of the magno-pathway by parvo-pathway signals immediately after a saccade causes SSD, which helps to achieve the perceptual stability of the visual world across saccades.
| S-EPMC7283269 | biostudies-literature