PTVR - A software in Python to make virtual reality experiments easier to build and more reproducible.

Researchers increasingly use virtual reality (VR) to perform behavioral experiments, especially in vision science. These experiments are usually programmed directly in so-called game engines that are extremely powerful. However, this process is tricky and time-consuming as it requires solid knowledge of game engines.

A New Vessel-Based Method to Estimate Automatically the Position of the Nonfunctional Fovea on Altered Retinography From Maculopathies.

Purpose: The purpose of this study was to validate a new automated method to locate the fovea on normal and pathological fundus images. Compared to the normative anatomic measures (NAMs), our vessel-based fovea localization (VBFL) approach relies on the retina's vessel structure to make predictions.

Methods: The spatial relationship between the fovea location and vessel characteristics is learnt from healthy fundus images and then used to predict fovea location in new images.

The inhibitory effect of word neighborhood size when reading with central field loss is modulated by word predictability and reading proficiency.

For normally sighted readers, word neighborhood size (i.e., the total number of words that can be formed from a single word by changing only one letter) has a facilitator effect on word recognition.

From Psychoacoustics to Brain Waves: A Longitudinal Approach to Novel Word Learning.

Musical expertise has been shown to positively influence high-level speech abilities such as novel word learning. This study addresses the question whether low-level enhanced perceptual skills causally drives successful novel word learning. We used a longitudinal approach with psychoacoustic procedures to train 2 groups of nonmusicians either on pitch discrimination or on intensity discrimination, using harmonic complex sounds.

Activation time-course of phonological code in silent word recognition in adult readers with and without dyslexia.

In skilled adult readers, reading words is generally assumed to rapidly and automatically activate the phonological code. In adults with dyslexia, despite the main consensus on their phonological processing deficits, little is known about the activation time course of this code. The present study investigated this issue in both populations.

Linguistic processes do not beat visuo-motor constraints, but they modulate where the eyes move regardless of word boundaries: Evidence against top-down word-based eye-movement control during reading.

Where readers move their eyes, while proceeding forward along lines of text, has long been assumed to be determined in a top-down word-based manner. According to this classical view, readers of alphabetic languages would invariably program their saccades towards the center of peripheral target words, as selected based on the (expected) needs of ongoing (word-identification) processing, and the variability in within-word landing positions would exclusively result from systematic and random errors. Here we put this predominant hypothesis to a strong test by estimating the respective influences of language-related variables (word frequency and word predictability) and lower-level visuo-motor factors (word length and saccadic launch-site distance to the beginning of words) on both word-skipping likelihood and within-word landing positions.

The optimal use of non-optimal letter information in foveal and parafoveal word recognition.

Letters and words across the visual field can be difficult to identify due to limiting visual factors such as acuity, crowding and position uncertainty. Here, we show that when human readers identify words presented at foveal and para-foveal locations, they act like theoretical observers making optimal use of letter identity and letter position information independently extracted from each letter after an unavoidable and non-optimal letter recognition guess. The novelty of our approach is that we carefully considered foveal and parafoveal letter identity and position uncertainties by measuring crowded letter recognition performance in five subjects without any word context influence.

The influence of word frequency on word reading speed when individuals with macular diseases read text.

People with central field loss (CFL) use peripheral vision to identify words. Eccentric vision provides ambiguous visual inputs to the processes leading to lexical access. Our purpose was to explore the hypothesis that this ambiguity leads to strong influences of inferential processes, our prediction being that increasing word frequency would decrease word reading time.

Motion Masking by Stationary Objects: A Study of Simulated Saccades.

Saccades are crucial to visual information intake by re-orienting the fovea to regions of interest in the visual scene. However, they cause drastic disruptions of the retinal input by shifting the retinal image at very high speeds. The resulting motion and smear are barely noticed, a phenomenon known as saccadic omission.

The magnification factor accounts for the greater hypometria and imprecision of larger saccades: Evidence from a parametric human-behavioral study.

Saccades quite systematically undershoot a peripheral visual target by about 10% of its eccentricity while becoming more variable, mainly in amplitude, as the target becomes more peripheral. This undershoot phenomenon has been interpreted as the strategic adjustment of saccadic gain downstream of the superior colliculus (SC), where saccades are programmed. Here, we investigated whether the eccentricity-related increase in saccades' hypometria and imprecision might not instead result from overrepresentation of space closer to the fovea in the SC and visual-cortical areas.

Clustering of Eye Fixations: A New Oculomotor Determinant of Reading Speed in Maculopathy.

Purpose: To describe and quantify a largely unnoticed oculomotor pattern that often occurs when patients with central field loss (CFL) read continuous text: Horizontal distribution of eye fixations dramatically varies across sentences and often reveals clusters. Also to statistically analyze the effect of this new factor on reading speed while controlling for the effect of saccadic amplitude (measured in letters per forward saccade, L/FS), an established oculomotor effect.

Methods: Quantification of nonuniformity of eye fixations (NUF factor) was based on statistical analysis of the curvature of fixation distributions.

A New Font, Specifically Designed for Peripheral Vision, Improves Peripheral Letter and Word Recognition, but Not Eye-Mediated Reading Performance.

Reading speed is dramatically reduced when readers cannot use their central vision. This is because low visual acuity and crowding negatively impact letter recognition in the periphery. In this study, we designed a new font (referred to as the Eido font) in order to reduce inter-letter similarity and consequently to increase peripheral letter recognition performance.

Intrasaccadic perception triggers pupillary constriction.

It is commonly believed that vision is impaired during saccadic eye movements. However, here we report that some visual stimuli are clearly visible during saccades, and trigger a constriction of the eye's pupil. Participants viewed sinusoid gratings that changed polarity 150 times per second (every 6.

Role of syllable segmentation processes in peripheral word recognition.

Previous studies of foveal visual word recognition provide evidence for a low-level syllable decomposition mechanism occurring during the recognition of a word. We investigated if such a decomposition mechanism also exists in peripheral word recognition. Single words were visually presented to subjects in the peripheral field using a 6° square gaze-contingent simulated central scotoma.

Eye movements and reading speed in macular disease: the shrinking perceptual span hypothesis requires and is supported by a mediation analysis.

Purpose: Reading speed of patients with central field loss (CFL) correlates with the size of saccades (measured in letters per forward saccade [L/FS]). We assessed whether this effect is mediated by the total number of fixations, by the average fixation duration, or by a mixture of both.

Methods: We measured eye movements (with a video eye tracker) of 35 AMD and 4 Stargardt patients (better eye decimal acuity from 0.

The Optimal Viewing Position effect in the lower visual field.

The Optimal Viewing Position (OVP) effect shows that word identification is best when the eyes first fixate near the centre of words. While this effect has been extensively studied in normal reading conditions, it has not been much investigated for words in the periphery. Here, we compared, in a perceptual identification task, the OVP effect for words presented either on the line of sight or in the lower visual field.

Gaze-contingent simulation of retinopathy: some potential pitfalls and remedies.

Many important results in visual neuroscience rely on the use of gaze-contingent retinal stabilization techniques. Our work focuses on the important fraction of these studies that is concerned with the retinal stabilization of visual filters that degrade some specific portions of the visual field. For instance, macular scotomas, often induced by age related macular degeneration, can be simulated by continuously displaying a gaze-contingent mask in the center of the visual field.

Wet versus dry age-related macular degeneration in patients with central field loss: different effects on maximum reading speed.

Purpose: To describe new, efficient predictors of maximum reading speed (MRS) in age-related macular degeneration (AMD) patients with central field loss. Type of AMD (wet versus dry) was scrutinized, because this factor seems to offer a promising model of differential visual adaptation induced by different temporal courses of disease progression.

Methods: Linear mixed-effects (LME) analyses were performed on a dataset initially collected to assess the effect of interline spacing on MRS.

Similar effect of cueing conditions on attentional and saccadic temporal dynamics.

Spatial attention permits to allocate more processing resources to a restricted portion of the visual space. The influential premotor theory states that the allocation of spatial attention relies on the same processes as those responsible for programming saccadic eye movements. Accordingly, several studies have already demonstrated a close spatial correspondence between attention and saccades.

Small effect of interline spacing on maximal reading speed in low-vision patients with central field loss irrespective of scotoma size.

Purpose: It has been suggested that crowding, the adverse low-level effect due to the proximity of adjacent stimuli, explains slow reading in low-vision patients with absolute macular scotomas. According to this hypothesis, crowding in the vertical dimension should be released by increasing the vertical spacing between lines of text. However, studies with different experimental paradigms and only a few observers have given discrepant results on this question.