Visual system

Investigate development and organisation of the visual system using single-cell and spatial molecular profiling. The postdoctoral work combines multi-omics, viral engineering and computational modelling. The priority review date has passed; later applications are considered if the vacancy remains unfilled, through the final date shown.

…Using the Drosophila melanogaster visual system, I will discuss our efforts to dissect how individuality in circuit wiring emerges during development, and how that helps generate individual behavioral variation.

…the first complete wiring diagram of a visual system, which has been used to identify all 200+ cell types that are intrinsic to the Drosophila optic lobe. About half of these cell types were previously unknown, and less than 20% have ever been recorded by a physiologist. I will argue that plausible functions for many cell types can be guessed by interpreting the wiring diagram. VVTNS Fifth Season Closing Lecture. Presented in the van Vreeswijk Theoretical Neuroscience Semi

…scene of overlapping objects, the visual system quickly parses positional relationship

…in more than 90 cell types in the fly visual system and leveraging a pair of recently annotated optic lobe connectomes[2][3], we evalu

…For instance, animals use visual cues like motion parallax and binocular disparity to judge distances to objects as they navigate their environment. Although studies in several vision models have found neural activity that correlates with distance signals, the causal behavioral role of neurons and the range of possible properties that inform distance perception have remained poorly understood. Here, we developed a novel high-throughput behavioral assay to identify neurons i

The visual system processes vast amounts of information by internally weighting stimulus inputs based on their local features and behavioral relevance [1]. Although evidence shows that behavioral relevance influences stimulus saliency, it is not well understood how integrating stimulus and social information impacts perception and decision-making. Previous studies indicate that predicting others’ actions improves with real-time observation of their movements [3]. Additionally, game-theoretic simulations show that real-time feedback leads to leader-follower behavior, where one agent acts and t

…of single-cells in the fruit fly visual system and ca

The role of sensory systems is to interpret real-world events to facilitate behavior. For instance, the visual system enacts compensatory eye movements based on a global motion representation, generated by combining local motion signals from the retina. However, due to the aperture problem, local motion signals are inherently ambiguous, and how the visual system solves the aperture problem is unclear. We studied how the mouse Nucleus of the Optic Tract (NOT) integrates retinal visual information and how this supports behavioral responses. NOT mediates the horizontal optokinetic reflex, the com

The visual system consists of a hierarchy of distinct brain areas, each responsible for processing different aspects of visual features. To better understand how signals from an upstream area contribute to visual processing in the downstream area, this project will focus on a specific type of computation broadly found in the visual system: i.e., selectivity to motion direction. Many neurons in the mouse superior colliculus, a direct target of the retina, preferentially respond to stimuli moving in one direction, but not the opposite, with diverse direction preferences across populations. Such

Motion is encoded by the visual system using multiple cues. In primary visual cortex (V1), one cue is the tracking of object edges in a direction perpendicular to their orientation. Another cue, called motion streak, relates to tracking fast objects that create a smeared perception of motion along their trajectory. Intriguingly, dual tuning, to both cues in the same neuron, occurs in mutually perpendicular directions. We aimed to determine if dual tuning is predicted by a neuron’s spatio-temporal receptive field (STRF). Drifting white noise (DWN) patterns were presented at range of speeds (0:1

…data on the endocannabinoid (ECB) system has been gathered from higher brain regions like the prefrontal cortex, leaving aside structures that integrate the sensory systems. However, considering the conservation of cortical organization across areas and species, studying the latter would not only impact the understanding of the perceptual effects of cannabinoids, but potentially provide insights into the neural circuits involved in more complex behaviours.To this end, w

Early perspectives on the brain's visual system suggested that it is comprised of separate information streams, each specializing in processing distinct visual features. In this scheme, neurons in lower regions conduct local analyses of image elements within their small receptive fields, while neurons in higher visual areas represent the visual scene in a more global and abstract manner (e.g., by identification and segmentation of objects). However, when processing ambiguous visual stimuli, such as those generated by Kanizsa figures, the local analysis by lower levels might be insufficient for

Predictive coding theories argue that recent experience establishes expectations that generate prediction errors when violated. Neural correlates of prediction errors have been widely reported, but their perceptual consequences remain unknown. We had observers perform a dual-report task on the orientation of briefly presented gratings within predictable or random sequences. Observers first made a speeded response to categorize grating orientation (clockwise or counterclockwise from vertical), then reproduced the orientation without time pressure by rotating a bar. This allowed us to separately

Biological systems must selectively encode partial information about the environment, as dictated by the capacity constraints at work in all living organisms. For example, we cannot see every feature of the light field that reaches our eyes; temporal resolution is limited by transmission noise and delays, and spatial resolution is limited by the finite number of photoreceptors and output cells in the retina. Classical efficient coding theory describes how sensory systems can maximize information transmission given such capacity constraints, but it treats all input features equally. Not all inp

…of neural activity in the fly visual system as measured in the l

Retinotopy is generally preserved across the visual system, but its cellular-level organization remains elusive. How precisely is topographic information transmitted from the retina? To address this question, here we combined experimental and computational modelling approaches. First, using two-photon calcium imaging of retinal ganglion cell (RGC) axons as well as local neurons in the superior colliculus (SC), we performed functional mapping of the retinocollicular projection at a single-cell resolution in awake mice. The tiling patterns of RGC axon terminals and their corresponding receptive

We hardly notice when there is a speck on our glasses, the obstructed visual information seems to be magically filled in. The mechanistic basis for this fundamental perceptual phenomenon has, however, remained obscure. What enables neurons in the visual system to respond to context when the stimulus is not available? While feedforward information drives the activity in cortex, feedback information is thought to provide contextual signals that are merely modulatory. We have made the discovery that mouse primary visual cortical neurons are strongly driven by feedback projections from higher visu

Our visual system continually adapts to its sensory environment. As a result, both the encoding accuracy of sensory information and perceptual behavior change according to the recent history of sensory input. Here we tested the hypothesis that adaptation to the recent history of sensory input optimally prepares the perceptual system for the future, i.e. establishes efficient sensory representations for the next expected sensory input. We first quantitatively characterized the changes in neural encoding accuracy induced by adaptation with a psychophysical discrimination experiment. We measu

We hardly notice when there is a speck on our glasses, the obstructed visual information seems to be magically filled in. The visual system uses visual context to predict the content of the stimulus. What enables neurons in the visual system to respond to context when the stimulus is not available? In cortex, sensory processing is based on a combination of feedforward information arriving from sensory organs, and feedback information that originates in higher-order areas. Whereas feedforward information drives the activity in cortex, feedback information is thought to provide contextual signal

Profound changes in the visual environment occur over the course of the day-night cycle. There is therefore a profound pressure for cells and circuits within the visual system to adjust their function over time, to match the prevailing visual environment. Here, I will discuss electrophysiological data collected from nocturnal and diurnal rodents that reveal how the visual code is ‘temporally optimised’ by 1) the retina’s circadian clock, and 2) a change in behavioural temporal niche.

How does the visual system of insects function in vastly different light intensities, process separate parts of the visual field in parallel, and cope with eye sizes that differ between individuals? This talk will give you the answers we receive from our unique(ly adorable) model system: hawkmoths.

…successful in modeling the visual system, using mostly feedforward networks and leveraging community-wide efforts centered around benchmarks to both improve model architectures and evaluate model fits to data. Now that recurrent neural networks (RNNs) are also used to model a larger variety of brain functions, there is a similar need for developing appropriate metrics to compare these models. Towards this goal, we have built a high-throughput pipeline for training different RNN models on

…example is selective attention in the visual system, which allows to preferentially route signals from behaviourally relevant stimuli to downstream visual areas, while suppressing irrelevant visual information. It is an open question which neural mechanisms realize selective routing, and how this process is controlled. Here we propose that spontaneous synchronization in recurrent networks is the key mechanism for selective processin