Influence of Spatiotemporal Stimulus Structure on Memory-Guided Saccade Sequences

Saccades - rapid eye movements that place targets of interest on the fovea - are used to measure cognitive processes such as visual working memory. The goal of this study was to identify the influence of spatiotemporal structure, set size, and order of presentation on performance in memory-guided saccade sequences. Fourteen participants were presented with visual stimuli that differed in spatiotemporal structure (Sequential, Spatial, or Random) and set size (3-6) which they had to reproduce with sequential saccades. Results were analyzed with respect to % correct target recall, absolute error, and relative error. There was a significant influence of structure on errors (random>spatial > sequential), set size on correct recall and errors, primacy on correct recall, and interaction effects. These results indicate that spatiotemporal structure is beneficial for memory chunking in saccade sequence planning, however, this has complex interactions with set size, order, and the way saccade errors are measured

Updating spatial working memory in a dynamic visual environment

The present review describes recent developments regarding the role of the eye movement system in representing spatial information and keeping track of locations of relevant objects. First, we discuss the active vision perspective and why eye movements are considered crucial for perception and attention. The second part focuses on the question of how the oculomotor system is used to represent spatial attentional priority, and the role of the oculomotor system in maintenance of this spatial information. Lastly, we discuss recent findings demonstrating rapid updating of information across saccadic eye movements. We argue that the eye movement system plays a key role in maintaining and rapidly updating spatial information. Furthermore, we suggest that rapid updating emerges primarily to make sure actions are minimally affected by intervening eye movements, allowing us to efficiently interact with the world around us

Causal inference for spatial constancy across saccades

Contains fulltext : 157148.pdf (publisher's version ) (Open Access)During saccadic eye movements, the image on our retinas is, contrary to subjective experience, highly unstable. This study examines how the brain distinguishes the image perturbations caused by saccades and those due to changes in the visual scene. We first show that participants made severe errors in judging the presaccadic location of an object that shifts during a saccade. We then show that these observations can be modeled based on causal inference principles, evaluating whether presaccadic and postsaccadic object percepts derive from a single stable object or not. On a single trial level, this evaluation is not ?either/or? but a probability that also determines the weight by which pre- and postsaccadic signals are separated and integrated in judging object locations across saccades.20 p

Sensory enhancement of peripheral vision

More than 99% of the visual information is sampled by peripheral vision. Despite covering the majority of the visual field, the peripheral vision offers lower visual resolution than the fovea, that is responsible from gathering high resolution information from the central visual field. Although visual sensitivity changes drastically across the retina as a function of eccentricity, our visual experiences appear to be homogeneous. This apparent visual homogeneity is achieved by our visual system striving to optimize information gathering and minimize biological costs. To this end, the visual system uses various heuristics stemming from priors and expectations while dividing the labor of gathering information between available sensory systems. The aim of this dissertation is to provide an account of how various sensory mechanisms support peripheral vision. Particularly, in three studies, it investigated how peripheral vision and the execution of peripheral tasks are supported by transsaccadic learning and prediction, neural feedbacks providing additional processing resources, and supplementary information from other senses. Study I investigated how transsaccadic learning and object predictions of familiar objects supports peripheral vision. Through transsaccadic learning the visual system associates how the appearance of an object or a feature change from periphery to fovea. Using these object specific associations visual system generates predictions about these objects and how they would look like at different eccentricities. In addition, through lifelong experience on how object appearance changes as a function of eccentricity, the visual system could generate predictions even for novel objects. However, it was unclear whether object specific predictions reserved for familiar objects provide an advantage over general predictions that are also available for novel objects in visual tasks. Study I addressed this question in two experiments where observers unknowingly familiarized with a subset of the objects by performing a sham task that required them to make saccades to these objects. On the following day, they either performed a peripheral-foveal matching or transsaccadic change detection task with familiarized and novel objects. We found that the presence of familiar objects improved the performance in both tasks by providing more precise object specific predictions from previous peripheral-foveal associations that generalize across the visual hemifields. Thus, Study I shows that object specific predictions unique to familiar objects provide additional support to the peripheral vision and execution of peripheral tasks. Study II investigated a neural feedback mechanism that allows peripheral information to be processed in the fovea retinotopic cortex and supports peripheral discrimination. The support of the foveal-feedback mechanism in peripheral discrimination can be impaired when a foveal input is presented asynchronously with peripheral targets. However, it was not clear whether the peripheral object information has to compete with the foveal input for the same neural resources, or if it is masked by it. Study II tested both explanations with a peripheral letter discrimination using both novel and familiar characters. Crucially, we manipulated the spatial frequency compositions of the foveal noise. Thus, if the foveal noise is masking the foveal-feedback, we would expect the efficiency of the foveal noises to vary depending on the amount of shared spatial frequency with the peripheral characters. Alternatively, if foveal noise is competing with the foveal-feedback, we would expect a more general effect of foveal noise independent from how they are similar to the peripheral characters. We found that low spatial frequency foveal noise was more effective at impairing the peripheral discrimination of both familiar and novel characters, indicating a frequency specific masking of foveal-feedback. We follow-up this result with a control experiment where the low and medium spatial frequency noises were presented overlappingly with the peripheral and foveal characters. As anticipated, we found that low frequencies were more effective at masking peripheral characters than medium frequencies while the opposite pattern was true for the foveal characters. Additionally, behavioral oscillation analyses suggested that the masking of foveal-feedback is periodic at around 5 Hz. Thus, Study II shows that the peripheral discrimination of both novel and familiar objects is supported by a foveal-feedback mechanism that periodically processes peripheral information and subjects to masking. Study III investigated how imprecise peripheral information can be combined with sensory information from other modalities. More specifically, virtual and augmented reality applications are promising for augmenting user performance and experience by providing supplementary information across senses. However, one major bottleneck for these applications is to supplement information within a tight spatiotemporal window across different sensory modalities. Therefore, if and how spatiotemporally incongruent information from different sources is an important theoretical question with direct implications. Study III addressed this question by testing how imprecise peripheral information can be combined with supplementary tactile information when they are spatially and temporally incongruent. Using a custom-built setup, observers performed visual displacement judgments with or without spatially or temporally incongruent or congruent tactile displacement cues. Using their performance in the visual only condition, we modeled how observers combine visual and tactile information in the visuotactile conditions. We found that the combination weights systematically shifted towards tactile cues under temporal incongruency compared to congruency condition. In contrast, spatial incongruency altered how visual and tactile information are combined and hinted possible individual differences in cue combination strategies. Thus, the weighting of visual and tactile information is modulated and altered by spatial and temporal incongruency which might have important consequences for multisensory applications. Nevertheless, Study III suggests that despite large temporal and spatial incongruencies tactile cues can supplement peripheral visual information. In three studies, this dissertation seeks to understand how peripheral vision is supported by diverse neural and sensory mechanisms. In particular, peripheral vision is supported by precise object associations for familiar objects that are acquired through transsaccadic learning. These familiar object associations benefit peripheral matching and transsaccadic change detection by providing more precise peripheral to foveal and foveal to peripheral predictions than the general predictions available also for novel objects. Regardless of their familiarity, the peripheral discrimination of objects is also supported by a foveal-feedback mechanism that periodically processes peripheral object information in the foveal retinotopic areas. However, the processing of peripheral information is prone to masking by delayed foveal inputs with matching spatial frequency composition as the peripheral object. On the other hand, supplementary tactile information can be combined with imprecise peripheral information despite spatiotemporal incongruencies. However, while temporal incongruencies shift the weighting of visual and tactile information, spatial incongruencies can alter combination strategies differently across different individuals. In conclusion, these sensory interactions between peripheral vision and other sensory mechanisms support peripheral vision and offer better peripheral estimates for performing various tasks

Perception across saccadic eye movements: On the interrelationship between pre- and postsaccadic information

This dissertation is devoted to the question of how the healthy human brain generates visual experience of its environment, in its homogenous and coherent nature, given the stream of heterogeneous and incoherent information available to the visual system. Heterogeneity refers to the varying spatial resolution of visual information processing across the visual field (fovea to periphery) and incoherence to disruptions of visual information by fast jerk-like eye movements called saccades. Both of these aspects and their implications are described in the Introduction. Individual approaches and outcomes of four studies, each contributing to the understanding of the issue of visual stability stated above, are outlined subsequently. To gain understanding on whether and how information from before and after a disruptive saccade is integrated into perception, the first study (Study I) investigated whether perception of a stimulus observed across a saccade can be predicted by a statistically optimal integration of pre- and postsaccadic signals. Results revealed that perceptual performance was close to predictions for optimal transsaccadic integration. Integration even seemed to occur when the presented stimulus changed some visual properties during the saccade. As the result of the first study implied that integration of pre- and postsaccadic information is a phenomenon that is robust against visual discrepancies, the question emerged as to what would lead to transsaccadic segregation i.e., a percept of discrepancy between the pre- and postsaccadic information. Driven by the idea that the ability to integrate or segregate information develops over the lifespan, the second study (Study II) aimed to investigate transsaccadic segregation in children compared to young adults. The study showed that children detect stimulus displacements across a saccade less precisely than adults, indicating less transsaccadic segregation at childhood. However, children’s segregation abilities showed a stronger improvement due to the implementation of a perceptual aid (postsaccadic blank) compared to adults. In addition, children made less accurate and less precise saccades than adults but were also faster to correct their saccade landing errors. These results suggest that saccadic uncertainty (expectations about self-induced position errors) play a role in transsaccadic perception. To further determine the principles guiding transsaccadic segregation, the third study (Study III) investigated perception of intrasaccadic shape changes (circularity increase or decrease), and its relationship with shape appearance across the visual field. Results revealed that shape changes where we increased circularity across saccades were more likely to be perceived by participants (than circularity-decrease changes). In addition, shape appeared more circular before a saccade in the peripheral visual field compared to after a saccade in the fovea. These results suggest the existence of a predisposition to detect shape changes opposite (circularity increase) to the typical transsaccadic experience (circularity decrease). This gives further support to the assumption that expectations regarding transsaccadic contingencies play a key role in the ability to detect intrasaccadic changes. The fourth study (Study IV) turned towards the issue of how presaccadic visual stimulation affects postsaccadic perception and investigated the effect of short-term luminance adaptation before a saccade on contrast perception after the saccade. Results revealed that postsaccadic perception can be altered by presaccadic adaptation during very short durations corresponding to natural fixation durations. To conclude, transsaccadic perception is determined by the integration or segregation of pre- and postsaccadic information. Study I revealed that transsaccadic integration can occur despite large intrasaccadic stimulus changes. Studies II and III suggest that transsaccadic segregation depends on typical transsaccadic experience. Study IV showed that transsaccadic perception is likely to be affected by basic aspects of visual information processing such as adaptation. Taken together, this dissertation suggests that the visual system has developed statistically optimal and predictive mechanisms for heterogeneous and incoherent information to result in a coherent and adaptable perception of the environment

Data of Causal inference for spatial constancy across saccades

Dataset belonging to article:Causal inference for spatial constancy across saccadesbyJeroen Atsma, Femke Maij, Mathieu Koppen, David E. Irwin, W. Pieter MedendorpTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Data of Causal inference for spatial constancy across saccades

Dataset belonging to article:Causal inference for spatial constancy across saccadesbyJeroen Atsma, Femke Maij, Mathieu Koppen, David E. Irwin, W. Pieter Medendor