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

Decision making often relies on accumulating evidence for different choices. Traditional decision-making models predict that neural activity will exhibit persistent ramping with evidence. By contrast, recent studies in rodents and primates have observed that the representation of accumulated evidence shifts between different neural populations as decision-making demands change within a trial. Prior models only accumulate and maintain evidence, but fail to explain the transfer of graded evidence between populations. This transfer supports the continuous representation of a decision when an anim

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

We actively sample our visual environment via gaze shifts, primarily involving eye and head movements. While there has been extensive research on human eye movements, this is not the case for head movements, which remain severely underexplored, both in terms of their behavioral characteristics and underlying electrophysiology. Here, we report data from multiple experiments where human participants performed gaze shifts that included real-world head and eye movements. Head and eye tracking data were recorded simultaneously with scalp EEG in healthy participants and intracranial EEG in epilepsy

A central interest in neuroscience is understanding how the brain produces and orchestrates behavior. Our group studies these topics in rats, utilizing recent advances in tracking technology and analytic tools to quantify and explore behavior in naturalistic, unrestrained contexts. Previous publications from the group describe robust postural and behavioral representations in the posterior parietal cortex (PPC), frontal motor cortex and primary sensory cortices (Mimica et al., 2018, Mimica, Tombaz et al., 2023). To better understand how neuronal populations integrate active sensory input to in

In today's society, people often find it difficult to read news outside their social circle or comfort zone. The questions of whether limited availability or active avoidance of such information determines its limited reach and which neurocognitive factors contribute to this outcome are of huge importance but not adequately studied. MyNewsScan is a news aggregator platform that we developed to tackle such questions. We performed experiments asking participants to select, read and evaluate news articles on MyNewsScan: either in our Edinburgh lab with collection of biometric information such as

…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

Goal-directed saccades have been studied extensively in primates. In contrast, eye movements in mice have been thought to mainly coordinate eye-head coupling, rather than actively select visual input, due to the absence of a retinal fovea and their reliance on non-visual senses. But does this hold true during naturalistic behaviour?To study mouse eye movements in a naturalistic context featuring self-initiated visual flow and the need for visual target tracking, we designed a foraging task presented in a virtual reality, projected onto a 210-degree immersive environment (Fig1A). The saccades w

…Accordingly, eye movement abnormalities associated with AD are often observed durin

Humans use eye movements to sample the visual world, and these impact which information is retained in memory. However, memory is not only affected by the amount of time spent viewing a visual scene but also by specific gaze patterns during visual exploration. Revisitations occur when the eye gaze returns to a previously fixated location, resembling retrieval processes and offering another chance to encode. What remains unclear is whether revisitations actually enhance long-term memory formation and how they are associated with hippocampal activity dynamics. In this study, 50 human participant

Eye movements are known to be driven by stimulus features (e.g., saliency). However, spatiotemporal dynamics of eye movements are remarkably stable within an individual. In a previous study, we recorded eye movements from 120 participants in a free-viewing task. Three principal components explained 60% of the variance of the data. The first principal component (PC1) loaded on fixation duration, and subjects could be clustered in two different visual exploration phenotypes: “static” and “dynamic” viewers. In a second EEG resting-state study on the same sample, carried out one year later, static

This study investigates whether retinotopic mapping can be integrated into classical computational architectures that model biological visual pathways, specifically deep convolutional neural networks (dCNNs), to enhance image categorization and localization performance. The study retrains a retinotopic dCNN on the ImageNet task, which involves classifying images into 1000 labels.The study's primary finding is that standard deep CNNs are highly effective in processing retinotopic inputs, despite the significant transformation of visual inputs that this mapping entails (A). The ResNet101 network

Animals move their head and eyes as they explore and sample the visual environment. Previous studies have demonstrated neural correlates of head and eye movements in rodent primary visual cortex (V1), but the sources and computational roles of these signals are unclear. We addressed this by combining measurement of head and eye movements with high density neural recordings in freely moving mice. V1 neurons responded primarily to gaze shifts, where head movements are accompanied by saccadic eye movements, rather than to head movements where compensatory eye movements stabilize gaze. A variety o

Generic neural networks optimized for task performance are often successful in predicting neural activity in animals. However, neural mechanisms dictate not only the task performance but also how a particular task is solved. Can we deduce mechanisms from cognitive strategies? To find out, we asked humans and monkeys to perform a challenging task in which they steered to a remembered goal location by integrating self-motion in a virtual environment lacking position cues. Although this task requires only mentally tracking one’s position relative to the goal, subjects physically tracked this late

…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

…and this is particularly true of eye movements. Here, the superior colliculus (SC) plays a fundamental role, issuing saccade motor commands in the form of strong peri-movement bursts that are very widely believed to specify both saccade metrics (direction and amplitude) and kinematics (speed). However, practically all models of saccade control by the SC rely on observations with small light spots as saccade targets. Instead, we asked monkeys to “loo

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

…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

…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

State-of-the-art machine vision models can predict human recognition memory for complex scenes with astonishing accuracy. In this talk I present work that investigated how memorable scenes are actually remembered and experienced by human observers. We found that memorable scenes were recognized largely based on recollection of specific episodic details but also based on familiarity for an entire scene. I thus highlight current limitations in machine vision models emulating human recognition memory, with promising opportunities for future research. Moreover, we were interested in what observers

…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

…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