Anticipatory smooth pursuit eye movements scale with the probability of visual motion: The role of target speed and acceleration.

Sensory-motor systems can extract statistical regularities in dynamic uncertain environments, enabling quicker responses and anticipatory behavior for expected events. Anticipatory smooth pursuit eye movements (aSP) have been observed in primates when the temporal and kinematic properties of a forthcoming visual moving target are fully or partially predictable. To investigate the nature of the internal model of target kinematics underlying aSP, we tested the effect of varying the target kinematics and its predictability.

Mammals Achieve Common Neural Coverage of Visual Scenes Using Distinct Sampling Behaviors.

Most vertebrates use head and eye movements to quickly change gaze orientation and sample different portions of the environment with periods of stable fixation. Visual information must be integrated across fixations to construct a complete perspective of the visual environment. In concert with this sampling strategy, neurons adapt to unchanging input to conserve energy and ensure that only novel information from each fixation is processed.

What over When in causal agency: Causal experience prioritizes outcome prediction over temporal priority.

Prior expectations strongly structure the way we perceive the world and ourselves. For instance, action-outcome prediction can modulate time perception and causal experience. We designed a study that allowed us to investigate whether action-outcome prediction has similar effects on time perception and intentional causality.

A behavioral receptive field for ocular following in monkeys: Spatial summation and its spatial frequency tuning.

In human and non-human primates, reflexive tracking eye movements can be initiated at very short latency in response to a rapid shift of the image. Previous studies in humans have shown that only a part of the central visual field is optimal for driving ocular following responses. Herein, we have investigated spatial summation of motion information across a wide range of spatial frequencies and speeds of drifting gratings by recording short-latency ocular following responses in macaque monkeys.

Speed Estimation for Visual Tracking Emerges Dynamically from Nonlinear Frequency Interactions.

Sensing the movement of fast objects within our visual environments is essential for controlling actions. It requires online estimation of motion direction and speed. We probed human speed representation using ocular tracking of stimuli of different statistics.

Sex differences in visuomotor tracking.

There is a growing interest in sex differences in human and animal cognition. However, empirical evidences supporting behavioral and neural sex differences in humans remain sparse. Visuomotor behaviors offer a robust and naturalistic empirical framework to seek for the computational mechanisms underlying sex biases in cognition.

Recurrent network dynamics reconciles visual motion segmentation and integration.

In sensory systems, a range of computational rules are presumed to be implemented by neuronal subpopulations with different tuning functions. For instance, in primate cortical area MT, different classes of direction-selective cells have been identified and related either to motion integration, segmentation or transparency. Still, how such different tuning properties are constructed is unclear.

Visual stimulation quenches global alpha range activity in awake primate V4: a case study.

Increasing evidence suggests that sensory stimulation not only changes the level of cortical activity with respect to baseline but also its structure. Despite having been reported in a multitude of conditions and preparations (for instance, as a quenching of intertrial variability, Churchland et al., 2010), such changes remain relatively poorly characterized.

A Normalization Mechanism for Estimating Visual Motion across Speeds and Scales.

Interacting with the natural environment leads to complex stimulations of our senses. Here we focus on the estimation of visual speed, a critical source of information for the survival of many animal species as they monitor moving prey or approaching dangers. In mammals, and in particular in primates, speed information is conceived to be represented by a set of channels sensitive to different spatial and temporal characteristics of the optic flow [1-5].

The Flash-Lag Effect as a Motion-Based Predictive Shift.

Due to its inherent neural delays, the visual system has an outdated access to sensory information about the current position of moving objects. In contrast, living organisms are remarkably able to track and intercept moving objects under a large range of challenging environmental conditions. Physiological, behavioral and psychophysical evidences strongly suggest that position coding is extrapolated using an explicit and reliable representation of object's motion but it is still unclear how these two representations interact.

The relative contribution of noise and adaptation to competition during tri-stable motion perception.

Animals exploit antagonistic interactions for sensory processing and these can cause oscillations between competing states. Ambiguous sensory inputs yield such perceptual multistability. Despite numerous empirical studies using binocular rivalry or plaid pattern motion, the driving mechanisms behind the spontaneous transitions between alternatives remain unclear.

Behavioral characterization of prediction and internal models in adolescents with autistic spectrum disorders.

Autism has been considered as a deficit in prediction of the upcoming event or of the sensory consequences of our own movements. To test this hypothesis, we recorded eye movements from high-functioning autistic adolescents and from age-matched controls during a blanking paradigm. In this paradigm, adolescents were instructed to follow a moving target with their eyes even during its transient disappearance.

Looking for symmetry: fixational eye movements are biased by image mirror symmetry.

Humans are highly sensitive to symmetry. During scene exploration, the area of the retina with dense light receptor coverage acquires most information from relevant locations determined by gaze fixation. We characterized patterns of fixational eye movements made by observers staring at synthetic scenes either freely (i.

Fixational saccades during grating detection and discrimination.

We investigated the patterns of fixational saccades in human observers performing two classical perceptual tasks: grating detection and discrimination. First, participants were asked to detect a vertical or tilted grating with one of three spatial frequencies and one of four luminance contrast levels. In the second experiment, participants had to discriminate the spatial frequency of two supra-threshold gratings.

Dynamic resolution of ambiguity during tri-stable motion perception.

Multi-stable perception occurs when an image falling onto the retina has multiple incompatible interpretations. We probed this phenomenon in psychophysical experiments using a moving barber-pole visual stimulus configured as a square to generate three competing perceived directions, horizontal, diagonal and vertical. We characterised patterns in reported switching type and percept duration, classifying switches into three groups related to the direction cues driving such transitions i.

Dynamic interaction between retinal and extraretinal signals in motion integration for smooth pursuit.

Due to the aperture problem, the initial direction of tracking responses to a translating bar is biased towards the direction orthogonal to the bar. This observation offers a powerful way to explore the interactions between retinal and extraretinal signals in controlling our actions. We conducted two experiments to probe these interactions by briefly (200 and 400 ms) blanking the moving target (45° or 135° tilted bar) during steady state (Experiment 1) and at different moments during the early phase of pursuit (Experiment 2).

Anisotropic connectivity implements motion-based prediction in a spiking neural network.

Predictive coding hypothesizes that the brain explicitly infers upcoming sensory input to establish a coherent representation of the world. Although it is becoming generally accepted, it is not clear on which level spiking neural networks may implement predictive coding and what function their connectivity may have. We present a network model of conductance-based integrate-and-fire neurons inspired by the architecture of retinotopic cortical areas that assumes predictive coding is implemented through network connectivity, namely in the connection delays and in selectiveness for the tuning properties of source and target cells.

Motion-based prediction explains the role of tracking in motion extrapolation.

During normal viewing, the continuous stream of visual input is regularly interrupted, for instance by blinks of the eye. Despite these frequents blanks (that is the transient absence of a raw sensory source), the visual system is most often able to maintain a continuous representation of motion. For instance, it maintains the movement of the eye such as to stabilize the image of an object.

More is not always better: adaptive gain control explains dissociation between perception and action.

Moving objects generate motion information at different scales, which are processed in the visual system with a bank of spatiotemporal frequency channels. It is not known how the brain pools this information to reconstruct object speed and whether this pooling is generic or adaptive; that is, dependent on the behavioral task. We used rich textured motion stimuli of varying bandwidths to decipher how the human visual motion system computes object speed in different behavioral contexts.

Dynamics of local input normalization result from balanced short- and long-range intracortical interactions in area V1.

To efficiently drive many behaviors, sensory systems have to integrate the activity of large neuronal populations within a limited time window. These populations need to rapidly achieve a robust representation of the input image, probably through canonical computations such as divisive normalization. However, little is known about the dynamics of the corticocortical interactions implementing these rapid and robust computations.

Motion-based prediction is sufficient to solve the aperture problem.

In low-level sensory systems, it is still unclear how the noisy information collected locally by neurons may give rise to a coherent global percept. This is well demonstrated for the detection of motion in the aperture problem: as luminance of an elongated line is symmetrical along its axis, tangential velocity is ambiguous when measured locally. Here, we develop the hypothesis that motion-based predictive coding is sufficient to infer global motion.

Motion clouds: model-based stimulus synthesis of natural-like random textures for the study of motion perception.

Choosing an appropriate set of stimuli is essential to characterize the response of a sensory system to a particular functional dimension, such as the eye movement following the motion of a visual scene. Here, we describe a framework to generate random texture movies with controlled information content, i.e.

A processing work-flow for measuring erythrocytes velocity in extended vascular networks from wide field high-resolution optical imaging data.

Comprehensive information on the spatio-temporal dynamics of the vascular response is needed to underpin the signals used in hemodynamics-based functional imaging. It has recently been shown that red blood cells (RBCs) velocity and its changes can be extracted from wide-field optical imaging recordings of intrinsic absorption changes in cortex. Here, we describe a complete processing work-flow for reliable RBC velocity estimation in cortical networks.