Biology subjects

Gilaie-Dotan, S.

Publications and source records attributed to Gilaie-Dotan, S..

7 recordsLinked to original sources

bioRxiv2023

Parafoveal vision reveals qualitative differences between FFA and PPA

The center-periphery visual field axis guides early visual system organization with enhanced resources devoted to central vision leading to reduced peripheral performance relative to that of central vision (i.e., behavioral eccentricity effect) for most visual functions. The center-periphery organization extends to high-order visual cortex where for example the well-studied face-sensitive fusiform face area (FFA) shows sensitivity to central vision and place-sensitive parahippocampal place area (PPA) shows sensitivity to peripheral vision. As we have recently found that face perception is more sensitive to eccentricity than place perception, here we examined whether these behavioral findings reflect differences in FFA and PPAs sensitivities to eccentricity. We assumed FFA would show higher sensitivity to eccentricity than PPA would, but that both regions modulation by eccentricity would be invariant to the viewed category. We parametrically investigated (fMRI, n=32) how FFAs and PPAs activations are modulated by eccentricity ([≤]8{degrees}) and category (upright/inverted faces/houses) while keeping stimulus size constant. As expected, FFA showed an overall higher sensitivity to eccentricity than PPA. However, both regions activation modulations by eccentricity were dependent on the viewed category. In FFA a reduction of activation with growing eccentricity ("BOLD eccentricity effect") was found (with different amplitudes) for all categories. In PPA however, there were qualitative modulations of the BOLD eccentricity effect with mild BOLD eccentricity effect for houses but a reverse BOLD eccentricity effect for faces and no modulation for inverted faces. Our results emphasize that peripheral vision investigations are critical to further our understanding of visual processing both quantitatively and qualitatively. Significance statementVisual perception significantly deteriorates with growing distance from central vision (behavioral eccentricity effect) with varying degrees according to visual function. For some functions (but not others) deterioration follows the reduction of resources devoted to peripheral vision at early visual processing stages. While early stages of visual processing reflect retinal spatial arrangement, here we found that activations in high-order visual areas that are less sensitive to visual field location show a BOLD fMRI activation eccentricity effect that mirrors the behavioral eccentricity effect. Importantly, the BOLD eccentricity effects we found varied across regions and were modulated quantitatively and qualitatively by the viewed visual categories. Our results emphasize that peripheral vision investigations are critical to further our understanding of visual processing.

neuroscience↗

bioRxiv2023

The effect of virtual visual scene inclination transitions on gait modulation in healthy young vs older adults - a virtual reality study

Bipedal locomotion requires body adaptation to maintain stability after encountering a transition to inclined walking. A major adaptation is the change in walking speed to maintain optimal energy consumption. When transitioning to uphill walking, people exert more energy to counteract gravitational forces pulling them backward, while when transitioning to downhill walking people break to avoid uncontrolled acceleration. This behavior is controlled by three main senses: proprioception and vestibular (aka body-based cues), and visual cues. In this study, we aimed to measure the influence of the visual cues on these modulations in healthy older adults and compare it to healthy young adults. To that end, we used a fully immersive virtual-reality system embedded with a self-paced treadmill and projected visual scene that allowed us to manipulate the inclinations of the treadmill and the visual scene in an independent manner. In addition, we measured the visual field dependency of each participant using the rod and frame test. The group of older adults presented the braking (decelerating), and exertion (accelerating) effects, in response to downhill and uphill visual illusions, respectively, in a similar manner as the young group. Furthermore, we found a significant correlation between the intensity of the speed modulation and the visual field dependency for each group separately, however the visual field dependency was significantly higher in the elderly adults. These results suggest that with aging individuals maintain their reliance on the visual system to modulate their gait in accordance with surface inclination in the same manner as young adults.

neuroscience↗

bioRxiv2020

Vision affects gait speed but not patterns of muscle activation during inclined walking - a virtual reality study

While walking, our locomotion is affected by and adapts to the environment based on vision-based and body-based (vestibular and proprioception) cues, all contributing to an "Internal Model of Gravity". During surface inclination transitions, we modulate gait to counteract gravitational forces by braking during downhill walking to avoid uncontrolled acceleration or by exerting effort to avoid deceleration while walking uphill. In this study, we investigated the role of vision in gait modulation during surface inclination transitions by using an immersive large-scale Virtual Reality (VR) system equipped with a self-paced treadmill and projected visual scenes that allowed us to modulate physical-visual inclinations congruence parametrically. Gait speed and leg muscle electromyography (EMG) were measured in 12 healthy young adults. In addition, the magnitude of subjective visual misperception of verticality was measured by the rod and frame test. During virtual (non-veridical) inclination transitions, vision modulated gait speed after transitions by (i) slowing down to counteract the excepted gravitational boost in virtual downhill inclinations and by (ii) speeding up to counteract the expected gravity resistance in virtual uphill inclinations. These gait speed modulations were reflected in muscle activation intensity changes and associated with subjective visual verticality misperception. However, temporal patterns of muscle activation, which are significantly affected by real gravitational inclination transitions, were not affected by virtual (visual) inclination transitions. Our results delineate the contribution of vision to functional locomotion on uneven surfaces and may lead to enhanced rehabilitation strategies for neurological disorders affecting movement. Significance statementA crucial component of successful locomotion is maintaining balance and speed while walking on uneven surfaces. In order to reach successful locomotion, an individual must utilize multisensory integration of visual, gravitational, and proprioception cues. The contribution of vision to this process is still unclear, thus we used a fully immersive virtual reality treadmill setup allowing us to manipulate visual (virtual) and gravitational (real) surface inclinations independently during locomotion of healthy adults. While vision modulated gait speed for a short period after inclination transitions and this was predictive of individuals visual dependency, muscle activation patterns were only affected by gravitational surface inclinations, not by vision. Understanding the visions contribution to successful locomotion may lead to improved rehabilitation for movement disorders.

neuroscience↗

bioRxiv2020

Size matters - larger images are better remembered

We are constantly exposed to multiple visual scenes, and while freely viewing them without an intentional effort to memorize or encode them, only some are remembered. It has been suggested that image memorability is influenced by multiple factors as depth of processing (1-3), familiarity (4), and visual category (5-7). However, this is typically investigated with intentional (8, 9) or unintentional (10, 11) encoding tasks. Furthermore, since visual memory relies on size-invariant visual perception (12-14), image size is not considered a contributing factor. Here we reasoned that during naturalistic free viewing of images without an encoding task, bigger images would be better remembered due to multiple factors (as vaster expanse of activated visual cortex (15, 16), deeper processing). In an extensive set of experiments participants (n=117) freely viewed small to large images (3{degrees}-24{degrees}) without any encoding task. Subsequently, they were presented with mid-sized images (50% already seen) and were asked to report if they recall seeing them or not. Larger images were better remembered (~23% more than smaller images), image memorability was proportional to image size, faces were better remembered, and outdoors the least. These were independent of image set, presentation order, or screen resolution. While multiple factors affect image memorability (1-7), here we show that during free viewing with no encoding task, a basic physical image dimension influences its memorability.

neuroscience↗

bioRxiv2020

Oculomotor-related measures but not distance visual acuity are predictive of reading ability in first graders

1Some estimates suggest that one in seven good readers and the majority of children with reading difficulties suffer from oculomotor dysfunction (OMD), an umbrella term for abnormalities in comfortable and accurate fixations, pursuits and saccades. However, national vision evaluation programs worldwide are often limited to distance visual acuity (dVA), not testing for OMD despite its high prevalence and the ease to detect it in brief optometric evaluations. We hypothesized that reading acquisition is dependent on good oculomotor functions and therefore inadequate oculomotor control will be associated with reading difficulties. We retrospectively examined and compared oculomotor evaluations and reading assessments (using standardized national reading norms) of a normative class (28 first graders (6-7 yr. olds)) that were independently obtained while blind to the other assessment. Almost a third (29.6%) were categorized as having OMD-related difficulties; better oculomotor performance was predictive of better reading performance. Control analysis revealed dVA was not positively associated with reading performance. Linear regression analyses further corroborated these findings. While this study is based on a small cohort and replications are needed, our results indicate that oculomotor functions are associated with reading acquisition and suggest that young children struggling with reading should be referred to a comprehensive visual evaluation including oculomotor assessments. This may allow providing treatments for learning-related visual issues.

neuroscience↗

bioRxiv2019

Studying the precuneus reveals structure-function-affect correlation in long-term meditators

Understanding the relationship between brain structure, function and self-reports has hardly been addressed until now in meditation research. Here we demonstrate such relationship, using Mindfulness meditation (MM). MM aims to reduce thought-related processes and enhance bodily awareness, thereby reducing identification with thought content and deconstructing maladaptive self-schema. We thus hypothesized that structure of the default mode network (DMN) regions, associated with spontaneous thoughts and self-representation, would negatively correlate with MM experience and self-reported positive affect, while positively correlating with DMN resting-state function.\n\nCross-sectionally comparing a unique group of adept MM practitioners and meditation-naive matched controls using voxel based morphometry revealed that gray matter (GM) density of the left precuneus (L-Prc) was negatively correlated with MM expertise. Furthermore, GM density of the L-Prc was positively correlated with resting state and task related functional (fMRI) measures within the L-Prc in the MM practitioners, but not in the controls. Finally, the L-Prcs GM density negatively correlated with positive affect across all participants.\n\nOur findings may shed light on understanding structure-function-self reports relationship. While our approach enables studying suggestive correlations in expert MM practitioners, longitudinal studies are required for direct insights concerning the question of causality.\n\nSignificance statementUnderstanding the relationship between brain structure and function, individual differences and self-reports, is an important goal of neuroscience. Yet, these factors were hardly investigated together in meditation research. The precuneus is part of the default mode network (DMN) involved in thought related processes. Mindfulness meditation (MM) is a mental practice aiming to reduce thought related processes. Here, by cross-sectionally comparing adept meditators and controls, we found that in the precuneus of MM practitioners, structure associated with function. Overall, structure negatively correlated with practice length, as well as with positive affect scores. The structure-function correlation was only significant in the meditators group, possibly implying that prolonged meditation improved structure and function attunement in the DMN. More generally, this study demonstrates that mental practice can be related to conjoint structural and functional effects, as well as to affective self-reports.

neuroscience↗

bioRxiv2019

Face discrimination does not outperform house discrimination at foveal to parafoveal locations

Since perceptual and neural face sensitivity is associated with a foveal bias, and neural place sensitivity is associated with a peripheral bias (integration over space), we hypothesized that face perception ability will decline more with eccentricity than place perception ability. We also hypothesized that face perception ability may show an upper visual field (UVF) bias due to the proximity of face-related regions to UVF retinotopic representations, and a left visual field (LeVF) bias due to earlier reports suggesting right hemisphere dominance for faces. Participants performed foveal and parafoveal face and house discrimination tasks for upright or inverted stimuli ([≤] 4{degrees}) while their eye movements were monitored. Low-level visual tasks were also measured. The eccentricity-related accuracy reductions were evident for all categories. Through detailed analyses we found (i) a robust face inversion effect across the parafovea, while for houses an opposite effect was found, (ii) higher eccentricity-related sensitivity for face performance than for house performance (via inverted vs. upright within-category eccentricity-driven reductions), (iii) within-category but not across-category performance associations across eccentricities, and (iv) no hemifield biases. Our central to parafoveal investigations suggest that high-level vision processing may be reflected in behavioural performance.

neuroscience↗