Intrasaccadic perception triggers pupillary constriction

International audienceIt 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 6.67 ms). At this rate of flicker, the gratings were perceived as homogeneous surfaces while participants fixated. However, the flickering gratings contained ambiguous motion: rightward and leftward motion for vertical gratings; upward and downward motion for horizontal gratings. When participants made a saccade perpendicular to the gratings' orientation (e.g., a leftward saccade for a vertical grating), the eye's peak velocity matched the gratings' motion. As a result, the retinal image was approximately stable for a brief moment during the saccade, and this gave rise to an intrasaccadic percept: A normally invisible stimulus became visible when eye velocity was maximal. Our results confirm and extend previous studies by demonstrating intrasaccadic perception using a reflexive measure (pupillometry) that does not rely on subjective report. Our results further show that intrasaccadic perception affects all stages of visual processing, from the pupillary response to visual awareness

Can pulsed lighting help adults with dyslexia to read better: Testing LeFloch and Ropars’s hypothesis

Abstract The aim of the present study was to test Le Floch and Ropars’ hypothesis according to which dyslexia is mainly triggered by visual processing deficits, namely an absence of eye dominance, which induce the aberrant perception of afterimages for individual letters. According to these authors, dyslexic readers would be expected to produce reading performances very similar to those of controls under pulsed lighting conditions. 23 participants with dyslexia and 19 control readers were recruited and asked to perform two reading tasks under three different lighting conditions; standard lighting, pulsed lighting and a combination of the two. We used two reading measures for each participant and each lighting condition: (1) a reading accessibility index (using the MNREAD test) and (2) a text reading comprehension score. To control for individual differences in reading skills, all participants also completed a series of French standardized tests which were used to compute an individual reading impairment score. Finally, visual acuity and eye dominance were measured to control for participants’ visual function. We found no effect of lighting conditions on either of the two reading measures. This was true for all reading impairment score values and irrespective of whether participants showed eye dominance or not. Furthermore, even under pulsed lighting, individuals with dyslexia did not reach the reading performance of skilled adult readers, regardless of their eye dominance. In conclusion, we failed to show a clear positive impact of pulsed lighting on the reading skills of adults with dyslexia. This set of results does not support the visual hypothesis of dyslexia proposed by Le Floch and Ropars

The Mind-Writing Pupil : A Human-Computer Interface Based on Decoding of Covert Attention through Pupillometry

International audienceWe present a new human-computer interface that is based on decoding of attention through pupillometry. Our method builds on the recent finding that covert visual attention affects the pupillary light response: Your pupil constricts when you covertly (without looking at it) attend to a bright, compared to a dark, stimulus. In our method, participants covertly attend to one of several letters with oscillating brightness. Pupil size reflects the brightness of the selected letter, which allows us-with high accuracy and in real time-to determine which letter the participant intends to select. The performance of our method is comparable to the best covert-attention brain-computer interfaces to date, and has several advantages: no movement other than pupil-size change is required; no physical contact is required (i.e. no electrodes); it is easy to use; and it is reliable. Potential applications include: communication with totally locked-in patients, training of sustained attention, and ultra-secure password input

Detecting non-adjacent dependencies is the exception rather than the rule

International audienceStatistical learning refers to our sensitivity to the distributional properties of our environment. Humans have been shown to readily detect the dependency relationship of events that occur adjacently in a stream of stimuli but processing non-adjacent dependencies (NADs) appears more challenging. In the present study, we tested the ability of human participants to detect NADs in a new Hebb-naming task that has been proposed recently to study regularity detection in a noisy environment. In three experiments, we found that most participants did not manage to extract NADs. These results suggest that the ability to learn NADs in noise is the exception rather than the rule. They provide new information about the limits of statistical learning mechanisms

The Mind-Writing Pupil: A Human-Computer Interface Based on Decoding of Covert Attention through Pupillometry

Abstract We present a new human-computer interface that is based on decoding of attention through pupillometry. Our method builds on the recent finding that covert visual attention affects the pupillary light response: Your pupil constricts when you covertly (without looking at it) attend to a bright, compared to a dark, stimulus. In our method, participants covertly attend to one of several letters with oscillating brightness. Pupil size reflects the brightness of the selected letter, which allows us-with high accuracy and in real time-to determine which letter the participant intends to select. The performance of our method is comparable to the best covert-attention brain-computer interfaces to date, and has several advantages: no movement other than pupil-size change is required; no physical contact is required (i.e. no electrodes); it is easy to use; and it is reliable. Potential applications include: communication with totally locked-in patients, training of sustained attention, and ultra-secure password input. : human-computer interface, brain-computer interface, pupillometry, covert visual attention Manuscript in preparation [v1.1.4; Wed Sep 9 13:22:41 2015; There are many types of BCIs (reviewed in Keywords The first P300 spellers relied heavily on direct fixation: When participants did not move their eyes, but attended covertly to the letters, accuracy was only around 60%. Thus, four out of ten times the system selected another letter than the user had intended Expressed as information-transfer rate (ITR), which is a common measure for evaluating BCI performance These are hurdles for real-world applications (see also Birbaumer, 2006). Recently, a very different method, based on pupillometry, was developed and tested with partly locked-in patients Here we present an entirely new human-computer interface (HCI) that combines the performance of a P300 speller with the usability of pupillometry. Our system builds on the recent discovery that the pupil constricts (shrinks) when you covertly attend to a bright stimulus, compared to a dark Methods Preregistration This experiment was preregistered on Jan 21, 2015 (https://osf.io/yvaqs/). Whenever a deviation from registration occurred, it is indicated in the sections below. Materials and availability Participant data, experimental software, and analysis scripts are available from: https://github.com/smathot/mind-writing-pupil. This repository also includes a ready-to-use package for using our HCI with supported systems (currently tested with EyeLink and EyeTribe eye trackers, and Windows and Linux operating systems). A screencast of our method is available on-line: https://youtu.be/cGfkD2opTz4 Participants Ten naive participants from the community of Aix-Marseille Université were recruited (normal or corrected vision; 7 women; age range: 20-25). Participants received €90 for their participation (deviation from preregistration: We originally planned to pay €60). Participants provided written informed consent prior to the experiment. The study was conducted with approval of the ethics committee of Aix-Marseille Université (Ref.: 2014-12-03-09), and conformed to the Declaration of Helsinki (7 th rev.). Software and apparatus General stimuli and procedure Before each block, a nine-point eye-tracker calibration was performed. At the start of each trial, an automatic single-point recalibration (drift correction) was performed. The display consisted of a green central fixation dot (r = 0.2°) on a gray background (13.0 cd/m 2 ). Items were presented in a circular configuration at an eccentricity of 9.2

Text Reading Fluency and Text Reading Comprehension Do Not Rely on the Same Abilities in University Students With and Without Dyslexia

Developmental dyslexia is a specific learning condition characterized by severe and persistent difficulties in written word recognition, decoding and spelling that may impair both text reading fluency and text reading comprehension. Despite this, some adults with dyslexia successfully complete their university studies even though graduating from university involves intensive exposure to long and complex texts. This study examined the cognitive skills underlying both text reading comprehension and text reading fluency (TRF) in a sample of 54 university students with dyslexia and 63 university students without dyslexia, based on a set of tests adapted for an adult population, including listening comprehension, word reading, pseudoword reading (i.e., decoding), phonemic awareness, spelling, visual span, reading span, vocabulary, non-verbal reasoning, and general knowledge. The contribution of these skills to text reading fluency and text reading comprehension was examined using stepwise multiplicative linear regression analyses. As far as TRF is concerned, a regression model including word reading, pseudoword reading and spelling best fits the data, while a regression model including listening comprehension, general knowledge and vocabulary best fits the data obtained for text reading comprehension. Overall, these results are discussed in the light of the current literature on adults with dyslexia and both text reading fluency and text reading comprehension

Pupillary responses during one brightness-transition cycle.

<p>a) Example data from one participant. Pupil size as a function of whether the target changes from bright to dark (blue line) or from dark to bright (orange line). Shadings indicate standard deviation. b) The pupil size difference (i.e. orange—blue) for all participants. The participant indicated in red did not reach our criteria for successful training. The participant indicated by the arrow corresponds to the example shown in (a). All data is from Phase 1, in which participants selected one out of two stimuli.</p

The symbol-selection procedure used for free writing.

<p>Initially, there are eight groups of characters and control symbols (‘backspace’, ‘space’, and ‘accept’). When one group has been selected (here ‘abcd’), it unfolds into four individual symbols (here ‘a’, ‘b’, ‘c’, and ‘d’), after which a final selection is made (here ‘a’).</p

The mind-writing pupil: Near-perfect decoding of visual attention with pupillometry

<p>Slides for:</p> <p>Mathôt, S., Melmi, J.-B., van der Linden, L., & Van der Stigchel, S. (2015, May). <em>The Mind-Writing Pupil: Near-Perfect Decoding of Visual Attention with Pupillometry</em>. Talk presented at the Annual Meeting of the Vision Sciences Society, St. Pete Beach, FL, United States.</p