Natural scenes

Retinal ganglion cells (RGCs) show high convergence onto their downstream projections, which poses a problem for information transfer: how is it possible to preserve information through a synaptic layer that has significantly more inputs than outputs? There are an infinite number of ways to perform compression, and lossy compression suggests efficient yet computation-agnostic methods for reading out input stimuli or activity patterns. However, downstream neurons must perform essential computations on their inputs for the organism’s survival, rather than simply recapitulate input activity. In t

Like many other animals, humans direct their gaze to selectively sample the visual space based on task demands. Visual search, the process of locating an item among several visually presented objects, is a key paradigm in studying visual attention. While much is known about the brain networks underlying visual search, our understanding of the neural computations driving this behavior is limited. Simulating this behavior in-silico can provide a tool for developing and testing hypotheses about these neural computations. To address this gap, we trained an image-computable artificial neural networ

…neurons extract information from the natural environment. Models derived from their responses to artificial stimuli often have a hard time to generalize and predict responses to natural scenes. However, models directly learned on the responses to natural scenes can be hard to interpret. To address this issue, we have recently developed an approach where we add small perturbations to natural scenes and measure how these perturbations change neuronal responses, to better understand the features extracted by sensory neurons. I will show se

…artificial stimuli, but rarely with natural scenes. Even at the level of the retina, it is unclear how these adaptive processes impact ganglion cells, the retinal output, and how they change their feature selectivity to natural scenes as a function of the recent stimulus history. This raises a major challenge for our understanding of how ganglion cells proce

During perception the visual system integrates current sensory evidence with previously acquired knowledge of the visual world. Presumably this computation relies on internal recurrent interactions. We record populations of neurons from the primary visual cortex of cats and macaque monkeys and find evidence for adaptive internal responses to structured stimulation that change on both slow and fast timescales. In the first experiment, we present abstract images, only briefly, a protocol known to produce strong and persistent recurrent responses in the primary visual cortex. We show that repetit

…variety of species to thrive in the natural world. For humans, a suite of color management tools, developed since the early 20th century and used in our everyday devices, allow for a straightforward investigation of human color vision. However, unified methods for constructing chromatic visual stimuli in a laboratory setting for other animals are lacking. This has limited the study of visual perception in animals, where the spatiotemporal and chromatic components of vision are often treated separately, and resu

The sequential analysis of information in a coarse-to-fine (CtF) manner is a fundamental processing strategy of the visual system. Previous studies have shown that neurons in the primary visual cortex (V1) of anesthetized animals can process spatial information in a CtF fashion, shifting their spatial frequency (SF) preference from low (coarse) to high (fine) throughout their response to static grating stimuli. However, many central questions regarding CtF processing, such as whether it occurs in awake behaving mice and potential computational advantages it may provide, remain unexplored. Here

Statistics of natural scenes are not uniform - their structure varies dramatically from ground to sky. It remains unknown whether these non-uniformities are reflected in the large-scale organization of the early visual system and what benefits such adaptations would confer. By deploying an efficient coding argument, we predict that changes in the structure of receptive fields across visual space increase the efficiency of sensory coding. To test this experimentally, developed a simple, novel imaging system that is indispensable for studies at this scale. In agreement with our predictions, we c

Animal sensory systems are optimally adapted to those features typically encountered in natural surrounds, thus allowing neurons that have a limited bandwidth to encode almost impossibly large input ranges. Importantly, natural scenes are not random, and peripheral visual systems have therefore evolved to reduce the predictable redundancy. The vertebrate visual cortex is also optimally tuned to the spatial statistics of natural scenes, but much less is known about how the insect brain responds to these. We are redressing this deficiency using several techniques. Olga Dyakova uses exquisite im

Visual processing begins in the retina: within only two synaptic layers, multiple parallel feature channels emerge, which relay highly processed visual information to different parts of the brain. To functionally characterize these feature channels we perform calcium and glutamate population activity recordings at different levels of the mouse retina. This allows following the complete visual signal across consecutive processing stages in a systematic way. In my talk, I will summarize our recent findings on the functional diversity of retinal output channels and how they arise within the retin