Topic: eye movements

Investigate how eye movements shape perception with Martina Poletti and Michele Rucci at the University of Rochester. Research spans spatial representations, foveal and peripheral processing, attention, retinal anatomy, emmetropization and myopia. The laboratory combines human psychophysics, controlled retinal stimulation, computational modelling, precise eye and head tracking, retinal imaging and EEG during active vision. Researchers work within the Center for Visual Science and Brain and Cognitive Sciences, with collaborations in optics, neuroscience and ophthalmology. Applications comprise

Contemporary Bayesian theories of the mind highlight the role of prediction errors as a driving force in learning processes and the updating of our models of the world and of ourselves. This process is postulated to manifest both at explicit levels (e.g., subjective responses) and at implicit levels (e.g., eye movements, reaction time) of behavior. We developed a novel associative learning task in immersive virtual reality, in which a cue probabilistically predicted the subsequent location of a target to which participants had to reach. Specifically, the current study (N = 30) examined: (1) wh

Human eye movements are controlled by six extraocular muscles. Although the eye socket restricts eye movements to almost pure rotations (3 degrees-of-freedom) the brain seems to control it using only 2 degrees of freedom, keeping the torsional component in a strict relationship with the gaze angles (azimuth and elevation), according to Donders’ Law (Tweed et al.,1987). To study the control principles that may lead to such behaviour, we have designed a scaled-up cable-driven robotic eye with six actuators, with cable insertion points closely matching the relative positions of its biological cou

Selection is the hallmark of attention: processing improves for attended items but is relatively impaired for unattended items. It is well known that visual spatial attention changes sensory signals and perception in this selective fashion. In the work I will present, we asked whether and how attentional selection happens across time. First, our experiments revealed that voluntary temporal attention (attention to specific points in time) is selective, resulting in perceptual tradeoffs across time. Second, we measured small eye movements called microsaccades and found that directing voluntary t

Smooth pursuit eye movements are among our most intriguing motor behaviors. They are able to keep the line of sight on smoothly moving targets with little or no overt effort or deliberate planning, and they can respond quickly and accurately to changes in the trajectory of motion of targets. Nevertheless, despite these seeming automatic characteristics, pursuit is highly sensitive to high-level factors, such as the choices made about attention, or beliefs about the direction of upcoming motion. Investigators have struggled for decades with the problem of incorporating both high- and low-lev

Everything we see has a location. We know where things are before we know what they are. But how do we know where things are? Receptive fields in the visual system specify location but neural delays lead to serious errors whenever targets or eyes are moving. Motion may be the problem here but motion can also be the solution, correcting for the effects of delays and eye movements. To demonstrate this, I will present results from three motion illusions where perceived location differs radically from physical location. These help understand how and where position is coded. We first look at the ef

Human vision relies on rapid eye movements (saccades) 2-3 times every second to bring peripheral targets to central foveal vision for high resolution inspection. This rapid sampling of the world defines the perception-action cycle of natural vision and profoundly impacts our perception. Marmosets have similar visual processing and eye movements as humans, including a fovea that supports high-acuity central vision. Here, I present a novel approach developed in my laboratory for investigating the neural mechanisms of visual processing using naturalistic free viewing and simple target foraging pa

Current computational models of visual salience accurately predict the distribution of fixations on isolated visual stimuli. It is not known, however, whether the global salience of a stimulus, that is its effectiveness in the competition for attention with other stimuli, is a function of the local salience or an independent measure. Further, do task and familiarity with the competing images influence eye movements? In this talk, I will present the analysis of a computational model of the global salience of natural images. We trained a machine learning algorithm to learn the direction of the f

Outside the foveola, visual acuity and other visual functions gradually deteriorate with increasing eccentricity. Humans compensate for these limitations by relying on a tight link between perception and action; rapid gaze shifts (saccades) occur 2-3 times every second, separating brief “fixation” intervals in which visual information is acquired and processed. During fixation, however, the eye is not immobile. Small eye movements incessantly shift the image on the retina even when the attended stimulus is already foveated, suggesting a much deeper coupling between visual functions and oculomo

n natural vision, active vision refers to the changes in visual input resulting from self-initiated eye movements. In this talk, I will present studies that show that the stimulus-related activity during active vision differs substantially from that occurring during classical flashed-stimuli paradigms. Our results uncover novel and efficient mechanisms that improve visual perception. In a general way, the nervous system appears to engage in sensory modulation mechanisms, precisely timed to self-initiated stimulus changes, thus coordinating neural activity across different cortical areas and se

We introduce OpenEyeSim 2.1, an extension of the OpenEyeSim platform that includes simulation of accommodation control and chromatic aberrations. It is suitable for developing models of the joint learning of visual representations, eye movements, and accommodation control in the perception-action cycle. The simulated lens properties are kept simple for efficiency reasons but are detailed enough to capture essential depth-of-field effects. The model can simulate different accommodation states depending on focal point and pupil aperture. The longitudinal chromatic aberration is used to produce c

Much of our current understanding of brain-based visual processing is derived from studies involving immobilised animals. However, in reallife scenarios, visual perception is intrinsically linked with the movements of the eyes, head, and body. To gain amore comprehensive understanding of visual processing under these conditions, studying eye movement in freely moving subjects, such as mice is crucial. Our research is dedicated (i) to developing innovative hardware and software solutions to facilitate this advanced tracking and analysis and (ii) employing these techniques to study freely moving