Publications

In the flash-grab effect, an object flashed on a moving background appears to be shifted in the direction of the motion. The same background motion also distorts the flashed object's perceived shape. An even greater shift in the perceived location is produced by the frame effect, raising the question of whether it also produces a shape distortion. This phenomenon is important because the frame effect has been linked to perceptual stabilization during eye movements where the whole visual field acts as the frame. We found that, unlike the flash-grab case, shape was preserved for the frame effect to a much greater extent than for the flash-grab. Next, we tested the extent to which shape distortions could be predicted from the size of the shifts in position of individual shape elements. We found that observed distortions were weaker than predicted distortions for the frame effect, but stronger for the flash-grab stimulus. Finally, we examined whether the greater shape distortion for the flash-grab was due to the nature of the background motion (rotation vs. translation) or the aperture within which the background motion was presented (circular vs. rectangular). We found that both factors contributed to greater shape distortion. Our findings show that motion-induced shape distortions are not solely based on the individual position shifts of the shape elements when tested in isolation. The shape preservation for the frame effect may be achieved through engaging shape-based mechanisms tuned to the dynamics of saccadic eye movements.

PURPOSE: The purpose of this study is to address the challenge of limited donor retinal ganglion cell (RGC) migration into the retina after transplantation, which is largely due to donor neuron accumulation at the inner limiting membrane (ILM). We present a minimally invasive technique, ILM photodisruption, to locally ablate the ILM and thereby promote RGC engraftment.

METHODS: ILM photodisruption uses indocyanine green as a photosensitizer, which is delivered to the ILM and activated with ultra-short laser pulses. This process generates vapor nanobubbles (VNBs) that, upon collapse, create localized disruptions in the ILM. In this study, we finetuned this technology in bovine and postmortem human organotypic retinal explants to generate patterned ILM pores. To assess the impact of these photodisruption patterns on RGC transplantation, we applied induced pluripotent stem cell (iPSC)-derived RGCs to the ILM surface and co-cultured them for 7 days. Using advanced microscopy and spatial metric tools, we assessed donor RGC survival, spreading, and neurite localization. We compared ILM photodisruption to a current standard method of enzymatically digesting the ILM.

RESULTS: ILM photodisruption was highly effective in creating pores in both the bovine ILM and the thicker, more complex human ILM. In contrast, collagenase treatment had no effect on the human ILM. Both collagenase and ILM photodisruption significantly promoted donor RGC survival, enhanced cell spreading, and resulted in more neurites that extended deeper into the retina.

CONCLUSIONS: Our findings demonstrate that ILM photodisruption can overcome a key barrier in RGC replacement therapy and, as such, may help advance vision restoration strategies for glaucoma.

Despite more than five decades of research into eye movements in reading, questions remain about the relationship between lower-level lexical and higher-level semantic factors. We explored the simultaneous effects of word frequency (lower, higher), contextual predictability (lower, higher), and parafoveal preview (valid, invalid) on the processing of target words embedded in short passages of text. Using a repeated-measures design, 80 participants read 240 two-line passages, each containing a four- or five-letter target word. Corpus-based word frequencies and Cloze predictabilities were used as continuous variables in Bayesian mixed-effect analyses of fixation time and skipping measures. Key findings included robust main effects of frequency, predictability, and preview validity, as well as two-way interactions between Frequency × Preview in gaze duration, and Predictability × Preview in gaze duration and skipping. Frequency effects on gaze duration were greater under invalid preview conditions, suggesting that higher-frequency words facilitate corrective processing when preview is misleading. Predictability effects on gaze duration and skipping were enhanced under valid preview, indicating that contextual facilitation depends on coherent parafoveal input. No interaction was observed between frequency and predictability nor a three-way interaction, supporting the view that lexical access and contextual integration operate via distinct mechanisms. These findings highlight the critical role of parafoveal information in shaping the expression of lexical and contextual influences during reading.

Reported perception can exhibit a repulsive bias away from a task-irrelevant prior stimulus. Previous research has suggested that this repulsive serial bias is driven by low-level adaptation, such that the prior stimulus repels the representation of the new stimulus during encoding. To test this account, the present study compared the repulsive serial bias with another perceptual bias that is known to be driven by an adaptation mechanism (e.g., the tilt aftereffect). We measured the repulsive serial bias using a common location delayed estimation task and the adaptation-driven bias using a location estimation task with an inducer stimulus. We found that, although both repulsive serial bias and adaptation-driven bias were evident, the two biases were not correlated. In addition, only the repulsive serial bias was associated with a response time effect, where responses were slower when the bias was stronger. Moreover, mouse-tracking data for the repulsive serial bias exhibited a pattern that started with a stronger repulsion and ended with smaller repulsion, which cannot be explained by an adaptation mechanism alone. Taken together, our findings suggest that repulsive serial bias in continuous estimation tasks involves post-perceptual decisional processes that are not present in the adaptation-driven bias.

As research on human behavior, such as spatial navigation, increasingly adopts naturalistic settings, establishing best practices for such experiments becomes essential. Although virtual reality offers a bridge between laboratory control and real-world complexity, it does not fully capture the experiential richness of real-world environments. Here, we present a demonstration of a mobile eye-tracking study conducted in a large-scale, outdoor urban environment, featuring unconstrained, long-duration free exploration and outside-pointing tasks. Using the city of Limassol, Cyprus, as our testbed, we showcase the feasibility of collecting high-quality mobile eye-tracking, head orientation, and GPS data "in the wild," capturing a wide range of natural behavior with minimal experimental constraints. Based on this experience, we provide a set of best practices tailored to the logistical and methodological challenges posed by complex, real-world urban settings, challenges unlikely to arise in traditional indoor or highly controlled environments. Although these recommendations have general relevance, we exemplify them in the context of spatial navigation research. By establishing methodological standards for studies at this scale, we aimed to encourage and inform future research into naturalistic human behavior outside the laboratory.

The low prevalence effect, which posits that people are more likely to miss a present target when its prevalence rate is low, has important implications for real-world scenarios such as cancer screening and bomb detection. This effect has primarily been studied under full visibility; however, real-world scenarios often come with incomplete visibility. Occlusion and poor visibility introduce perceptual uncertainty, potentially altering how people decide whether a target is present. Here, we applied Bayesian decision theory to a visual search paradigm with partial occlusion, examining how target prevalence (prior) and the degree of occlusion (likelihood information) affect search decisions. Participants made target present/absent responses to target/distractor stimuli. In Experiment 1, all items were invisible, forcing participants to rely on trial feedback to learn the target's prevalence. Experiment 2 also provided trial feedback, but allowed either a small or large portion of the display to be visible. Target prevalence varied between blocks (high, 50%; low, 25%). Results showed that, when items were entirely hidden, participants learned to probability match the target's prevalence. However, when some items were visible, participants rarely responded present when the target was in the occluded region. Comparing the data with models (e.g., probability matching, Bayesian maximizing) revealed mixed strategies. This study introduces a novel method for investigating visual search under occlusion and suggests that, although people integrate prevalence and sensory input, their decisions are not fully Bayesian.

Cortically induced blindness (CB) resulting from stroke damage to the early visual cortex leads to extensive, typically extrafoveal visual deficits and is known to alter large-scale oculomotor behavior. Here, we show that even with preserved foveal acuity, fixational oculomotor behavior is subtly altered in CB patients. Using high-precision eye tracking, we observed a small but consistent gaze offset toward the blind field during passive fixation, which disappeared during a high-acuity central task. Despite this offset, fixation precision in both tasks was comparable, and it was similar between CB patients and age-matched controls. Curiously, the underlying oculomotor dynamics were also similar across the two task conditions: Microsaccades exhibited nonsignificant directional tendencies, while ocular drift was biased away from the blind field. Our findings indicate that the adult oculomotor system dynamically adapts to asymmetric visual injury and/or input. We speculate that the small fixational offsets observed in CB may reflect an attentional pointer toward the blind field and/or a compensatory oculomotor rebalancing that counteracts an asymmetric visual drive following cortical damage. Together, these results reveal a surprising preservation of context-dependent fixation control following early visual cortex damage in adulthood.

Recreational therapists work in a broad field with numerous service settings for individuals with disabilities. Students' learning may be enhanced by providing opportunities during class time to implement services for more unfamiliar populations. Therefore, the purpose of this study was to investigate students' reflections from a class time fieldwork experience (CTFE) in a recreational therapy (RT) class with adolescents who engage in health-risk behaviors. A retrospective, qualitative content analysis of 111 RT students' perspectives was used for this study, and two main themes emerged: exposure to an unfamiliar community population and identifying personal biases and judgments. Implications are identified for RT educators and practitioners to apply these findings to future CTFEs, internships, and employment opportunities.