Method to Quickly Map Multifocal Pupillary Response Fields (mPRF) Using Frequency Tagging.

We present a method for mapping multifocal Pupillary Response Fields in a short amount of time using a visual stimulus covering 40° of the visual angle divided into nine contiguous sectors simultaneously modulated in luminance at specific, incommensurate, temporal frequencies. We test this multifocal Pupillary Frequency Tagging (mPFT) approach with young healthy participants (N = 36) and show that the spectral power of the sustained pupillary response elicited by 45 s of fixation of this multipartite stimulus reflects the relative contribution of each sector/frequency to the overall pupillary response. We further analyze the phase lag for each temporal frequency as well as several global features related to pupil state.

Failed remyelination of the nonhuman primate optic nerve leads to axon degeneration, retinal damages, and visual dysfunction.

White matter disorders of the central nervous system (CNS), such as multiple sclerosis (MS), lead to failure of nerve conduction and long-lasting neurological disabilities affecting a variety of sensory and motor systems, including vision. While most disease-modifying therapies target the immune and inflammatory response, the promotion of remyelination has become a new therapeutic avenue to prevent neuronal degeneration and promote recovery. Most of these strategies have been developed in short-lived rodent models of demyelination, which spontaneously repair and do not reflect the size, organization, and biology of the human CNS.

Jumpy and Jerky: When Peripheral Vision Faces Reverse-Phi.

When an annulus in fast apparent motion reverses its contrast over time, the foveal and peripheral percepts are strikingly different. In central vision, the annulus appears to follow the same path as an annulus without flicker, whereas in the periphery, the stimulus seems to randomly jump across the screen. The illusion strength depends on motion speed and reversal rate.

Cursive Eye-Writing With Smooth-Pursuit Eye-Movement Is Possible in Subjects With Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder causing a progressive motor weakness of all voluntary muscles, whose progression challenges communication modalities such as handwriting or speech. The current study investigated whether ALS subjects can use Eye-On-Line (EOL), a novel eye-operated communication device allowing, after training, to voluntarily control smooth-pursuit eye-movements (SPEM) so as to eye-write in cursive. To that aim, ALS participants ( = 12) with preserved eye-movements but impaired handwriting were trained during six on-site visits.

Effects of pupillary responses to luminance and attention on visual spatial discrimination.

The optic quality of the eyes is, at least in part, determined by pupil size. Large pupils let more light enter the eyes, but degrade the point spread function, and thus the spatial resolution that can be achieved (Campbell & Gregory, 1960). In natural conditions, the pupil is mainly driven by the luminance (and possibly the color and contrast) at the gazed location, but is also modulated by attention and cognitive factors.

A novel method of inducing endogenous pupil oscillations to detect patients with unilateral optic neuritis.

Purpose: To use and test a new method of inducing endogenously generated pupillary oscillations (POs) in patients with unilateral optic neuritis (ON), to describe a signal analysis approach quantifying pupil activity and to evaluate the extent to which POs permit to discriminate patients from control participants.

Method: Pupil size was recorded with an eye-tracker and converted in real time to modulate the luminance of a stimulus (a 20° disk) presented in front of participants. With this biofeedback setting, an increasing pupil size transforms into a high luminance, entraining a pupil constriction that in turn decreases the stimulus luminance, and so on, resulting in endogenously generated POs.

Revolution of Alzheimer Precision Neurology. Passageway of Systems Biology and Neurophysiology.

The Precision Neurology development process implements systems theory with system biology and neurophysiology in a parallel, bidirectional research path: a combined hypothesis-driven investigation of systems dysfunction within distinct molecular, cellular, and large-scale neural network systems in both animal models as well as through tests for the usefulness of these candidate dynamic systems biomarkers in different diseases and subgroups at different stages of pathophysiological progression. This translational research path is paralleled by an "omics"-based, hypothesis-free, exploratory research pathway, which will collect multimodal data from progressing asymptomatic, preclinical, and clinical neurodegenerative disease (ND) populations, within the wide continuous biological and clinical spectrum of ND, applying high-throughput and high-content technologies combined with powerful computational and statistical modeling tools, aimed at identifying novel dysfunctional systems and predictive marker signatures associated with ND. The goals are to identify common biological denominators or differentiating classifiers across the continuum of ND during detectable stages of pathophysiological progression, characterize systems-based intermediate endophenotypes, validate multi-modal novel diagnostic systems biomarkers, and advance clinical intervention trial designs by utilizing systems-based intermediate endophenotypes and candidate surrogate markers.

Continuous Auditory Feedback of Eye Movements: An Exploratory Study toward Improving Oculomotor Control.

As eye movements are mostly automatic and overtly generated to attain visual goals, individuals have a poor metacognitive knowledge of their own eye movements. We present an exploratory study on the effects of real-time continuous auditory feedback generated by eye movements. We considered both a tracking task and a production task where smooth pursuit eye movements (SPEM) can be endogenously generated.

Sustained smooth pursuit eye movements with eye-induced reverse-phi motion.

The gain and speed of smooth pursuit eye movements quickly drop whenever a moving tracked target disappears behind an occluder. The present study tests to what extent pursuit maintenance after target disappearance depends on the occluder's characteristics. In all experiments, a target moving for 2500 ms, (or 1250 ms) at 13.

OB3D, a new set of 3D objects available for research: a web-based study.

Studying object recognition is central to fundamental and clinical research on cognitive functions but suffers from the limitations of the available sets that cannot always be modified and adapted to meet the specific goals of each study. We here present a new set of 3D scans of real objects available on-line as ASCII files, OB3D. These files are lists of dots, each defined by a triplet of spatial coordinates and their normal that allow simple and highly versatile transformations and adaptations.

Beta, but not gamma, band oscillations index visual form-motion integration.

Electrophysiological oscillations in different frequency bands co-occur with perceptual, motor and cognitive processes but their function and respective contributions to these processes need further investigations. Here, we recorded MEG signals and seek for percept related modulations of alpha, beta and gamma band activity during a perceptual form/motion integration task. Participants reported their bound or unbound perception of ambiguously moving displays that could either be seen as a whole square-like shape moving along a Lissajou's figure (bound percept) or as pairs of bars oscillating independently along cardinal axes (unbound percept).

A Bayesian computational model for online character recognition and disability assessment during cursive eye writing.

This research involves a novel apparatus, in which the user is presented with an illusion inducing visual stimulus. The user perceives illusory movement that can be followed by the eye, so that smooth pursuit eye movements can be sustained in arbitrary directions. Thus, free-flow trajectories of any shape can be traced.

Repetition blindness for natural images of objects with viewpoint changes.

When stimuli are repeated in a rapid serial visual presentation (RSVP), observers sometimes fail to report the second occurrence of a target. This phenomenon is referred to as "repetition blindness" (RB). We report an RSVP experiment with photographs in which we manipulated object viewpoints between the first and second occurrences of a target (0°, 45°, or 90° changes), and spatial frequency (SF) content.

Speeding up the brain: when spatial facilitation translates into latency shortening.

Waves of activity following a focal stimulation are reliably observed to spread across the cortical tissue. The origin of these waves remains unclear and the underlying mechanisms and function are still debated. In this study, we ask whether waves of activity modulate the magnetoencephalography (MEG) signals recorded in humans during visual stimulation with Gabor patches sequentially flashed along a vertical path, eliciting a perception of vertical apparent motion.

Cursive writing with smooth pursuit eye movements.

The eyes never cease to move: ballistic saccades quickly turn the gaze toward peripheral targets, whereas smooth pursuit maintains moving targets on the fovea where visual acuity is best. Despite the oculomotor system being endowed with exquisite motor abilities, any attempt to generate smooth eye movements against a static background results in saccadic eye movements. Although exceptions to this rule have been reported, volitional control over smooth eye movements is at best rudimentary.

Perceptual alternations between unbound moving contours and bound shape motion engage a ventral/dorsal interplay.

Visual shape and motion information, processed in distinct brain regions, should be combined to elicit a unitary coherent percept of an object in motion. In an fMRI study, we identified brain regions underlying the perceptual binding of motion and shape independently of the features-contrast, motion, and shape-used to design the moving displays. These displays alternately elicited a bound (moving diamond) or an unbound (disconnected moving segments) percept, and were either physically unchanging yet perceptually bistable or physically changing over time.

Impaired saccadic eye movement in primary open-angle glaucoma.

Purpose: Our study aimed at investigating the extent to which saccadic eye movements are disrupted in patients with primary open-angle glaucoma (POAG). This approach followed upon the discovery of differences in the eye-movement behavior of POAG patients during the exploration of complex visual scenes.

Methods: The eye movements of 8 POAG patients and 4 healthy age-matched controls were recorded.

Coupled dynamics of bistable distant motion displays.

This study explores the extent to which a display changing periodically in perceptual interpretation through smooth periodic physical changes-an inducer-is able to elicit perceptual switches in an intrinsically bistable distant probe display. Four experiments are designed to examine the coupling strength and bistable dynamics with displays of varying degree of ambiguity, similarity, and symmetry-in motion characteristics-as a function of their locations in visual space. The results show that periodic fluctuations of a remote inducer influence a bistable probe and regulate its dynamics through coupling.

Magnetoencephalographic signatures of visual form and motion binding.

This study investigates neural magneto-encephalographic (MEG) correlates of visual form and motion binding. Steady-state visual evoked fields (SSVEF) were recorded in MEG while observers reported their bound or unbound perception of moving bars arranged in a square shape. By using pairs of oscillating vertical and horizontal bars, "frequency-tagged" at f1 and f2, we identified a region with enhanced sustained power at 2f1+2f2 intermodulation frequency correlated with perceptual reports.

Phase delays within visual cortex shape the response to steady-state visual stimulation.

Although the spatial organization of visual areas can be revealed by functional Magnetic Resonance Imaging (fMRI), the synoptic, non-invasive access to the temporal characteristics of the information flow amongst distributed visual processes remains a technical and methodological challenge. Using frequency-encoded steady-state visual stimulation together with a combination of time-resolved functional magnetic source imaging from magnetoencephalography (MEG) and anatomical magnetic resonance imaging (MRI), this study evidences maps of visuotopic sustained oscillatory neural responses distributed across the visual cortex. Our results further reveal relative phase delays across responding striate and extra-striate visual areas, which thereby shape the chronometry of neural processes amongst these regions.

Pupil dynamics during bistable motion perception.

Pupil size not only varies to changes in illumination but is also modulated by several cognitive factors, making it a potentially versatile physiological marker of cortical states. We recorded pupil dynamics while subjects continuously reported their bistable perception of ambiguous moving stimuli, plaids, and partially occluded rotating diamonds. We observed small (about 5% of surface change on average) but reliable pupil dilation around (-300 ms to 1.

Superposition catastrophe and form-motion binding.

Numerous studies indicate that perceiving global object motion results from the integration of local component motions across space and time. Less attention has been paid to the issue of motion selection, necessary to avoid spurious associations of component motions belonging to different objects and to solve the so-called "superposition catastrophe problem" (F. Rosenblatt, 1961).

Directional shifts in the barber pole illusion: effects of spatial frequency, spatial adaptation, and lateral masking.

We report the results of psychophysical experiments with the so-called barber pole stimulus providing new insights on the neuronal processes underlying the analysis of moving features such as terminators or line-endings. In experiment 1, we show that the perceived direction of a barber pole stimulus, induced by line-ending motion, is highly dependent on the spatial frequency and contrast of the grating stimulus: perceived direction is shifted away from the barber pole illusion at high spatial frequency in a contrast dependent way, suggesting that line-ends are not processed at high spatial scales. In subsequent experiments, we use a contrast adaptation paradigm and a masking paradigm in an attempt to assess the spatial structure and location of the receptive fields that process line-endings.

Contour interactions between pairs of Gabors engaged in binocular rivalry reveal a map of the association field.

A psychophysical study was conducted to investigate contour interactions (the 'association field'). Two Gabor patches were presented to one eye, with random-dot patches in corresponding locations of the other eye so as to produce binocular rivalry. Perceptual alternations of the two rivalry processes were monitored continuously by observers and the two time series were cross-correlated.

Dynamic competition between contour integration and contour segmentation probed with moving stimuli.

Line-ends, corners and junctions are important singularities for form analysis, object recognition, depth ordering or motion processing. In this study, we investigate the extent to which processing the motion of line ends depends on the spatial configuration of their immediate surround. To that aim, we used two vertical collinear line segments, translating clockwise or anti-clockwise along a circular path, together with a direction discrimination task.