Visual processing

Fast periodic visual stimulation (FPVS) has emerged as a promising tool for assessing cognitive function in individuals with dementia. This technique leverages electroencephalography (EEG) to measure brain responses to rapidly presented visual stimuli, offering a non-invasive and objective method for evaluating a range of cognitive functions. Unlike traditional cognitive assessments, FPVS does not rely on behavioural responses, making it particularly suitable for individuals with cognitive impairment. In this talk I will highlight a series of studies that have demonstrated its ability to detec

Our research explores the neural mechanisms underlying flexibility during natural social interactions - how animals process dynamic sensory cues from a partner, make decisions, and pattern the appropriate action for the current context. During Drosophila social interactions, males produce time-varying songs via wing vibration, while females arbitrate mating decisions. We discovered that male song structure and intensity are continually sculpted by the movements of the female, over timescales ranging from tens of milliseconds to minutes, and we have investigated the underlying circuit mechanism

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

…system, plays a pivotal role in visual processing, attention, and cognitive flexibility. Most of the studies have been using standard visual stimuli, but the advance of virtual reality (VR) tools is promising for better elucidating the dynamics of this neuromodulator in visually guided behaviors. The present study aims to explore the spatiotemporal activation of cortical cholinergic fibers during the presentation of a VR dynamic environment compared to standard visual stimuli using mesoscopic ACh imaging in awake mice.Choliner

…information, minimizing further processing for familiar stimuli. For example, fusiform face area (FFA) consistently shows decreased neural response to repeated presentation of the same faces. According to the traditional model of visual processing, information progresses from the lower brain regions' superficial cortical layers to the higher areas' middle layers. Within this framewor

Visual processing is the ability of the brain to analyze and interpret visual information received from the eyes, and it is extensively studied in rodent primary visual cortex (V1) by revealing the relationship between neural circuitry and its functional behaviour. Within the V1, binocular neurons are crucial for stereopsis establishment and for various innate behaviours including navigation and predation. The development of binocular neurons requires vision stimulation since opening of eyes to reconstruct and modify the neural circuit according to the receptive field tunings. However, this bi

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

…In this study, we focused on visual processing and approached the above question by examining the intera

Visual coding is a highly dynamic process and continuously adapts to the current viewing context. At early stages of visual processing, adaptation was generally studied without considering behavioural contexts. However, we recently learned that locomotion and arousal strongly modulate visual processing, even at the retina level. Here, we aim to understand how locomotion impacts visual adaptation in the superior colliculus (SC), the most prominent visual centre in mice, which integrates retinal input in its superficial layers and performs sensorimotor transformations in its deeper layers. We r

…forming pathways and higher order visual cortices, the influence of the vestibular system on early stages of visual processing remains less understood. In this study, we aimed to investigate the impact of vestibular inputs on visual responses within key region receiving retinal input: the thalamic Lateral Geniculate Nucleus (LGN). To determine the specific effects of vestibular information on vi

Natural scenes are highly dynamic, challenging the reliability of visual processing. Yet, humans and many animals can perform accurate visual behaviors in nature, whereas computer vision devices struggle with changing environments. How do animal eyes achieve this? Here, we reveal the algorithms and mechanisms of rapid luminance gain control in Drosophila, resulting in stable visual processing. We identify the dendrites of specific third order neurons as the site of luminance gain control. The circuitry further involves wide field neurons, matching computational predictions that local spatial p

Navigating through a vivid environment requires animals to rapidly process a bewildering mass of sensory signals and interpret it in the context of ongoing behavior. Local and global motion cues along with luminance information guide them to orient and interact adaptively within the world. Larval zebrafish react to such signals with behaviors ranging from active light seeking and shadow avoidance to optomotor swimming or hunting that are expressed in kinematically distinct movements. We asked how are the brain-wide networks of neurons organized that process such signals and how do they integra

…of self-motion cues modulates visual processing in the superficial superior colliculus (sSC), the brain's first visual relay. We uncovered a projection from the ventral lateral geniculate nucleus to the sSC in mice that functions as a corollary discharge hub, conveying inhibitory signals about translational optic f

The visual system faces a dual challenge. On the one hand, features of the natural visual environment should be stably processed - irrespective of ongoing wiring changes, representational drift, and behavior. On the other hand, eye, head, and body motion require a robust integration of pose and gaze shifts in visual computations for a stable perception of the world. We address these dimensions of stable visual processing by studying the circuit mechanism of long-term representational stability, focusing on the role of plasticity, network structure, experience, and behavioral state while re

Normative principles describe how to efficiently encode visual scenes, and supervised learning models show how formal tasks shape visual processing, yet animal vision ultimately adapts to encode survival-relevant features. To study how ecology constrains visual processing, we present a reinforcement learning (RL) framework in which an agent aims to survive in a 3-d environment that it perceives through a vision model. In particular, we consider a visually-guided foraging task: the environment is populated with randomly placed objects, and the agent must learn to identify those that increase or

The primary visual cortex (V1) is fundamental for visual processing. Transcriptomics suggests that the microcircuit in V1 consists of many inhibitory and excitatory cell types1. However, exactly how those diverse cell populations participate in visual cognition in vivo is unknown. To address this question, we recorded from V1 of two anesthetized monkeys using high-density Neuropixel probes across all layers of cortex2. We identified single neuron waveforms using Kilosort2, followed by rigorous manual curation. Our final dataset was composed of 801 negative spiking neurons (from 2529 units, 5 s

Spatial context plays an important role in visual processing and perception. A rich set of surround effects that involve nonlinear interactions between the center and surround have been found in Primary Visual Cortex (V1). A general summary is that surround suppression is prevalent and the amount of suppression depends on the visual similarity between the center and surround. In recent years, convolutional neural networks (CNNs) have successfully modeled neural behavior across the visual cortices. However, there have been limited studies addressing the multitude of contextual effects that have

…For example, during visual processing a picture captured by the retina is processed hierarchically through the ventral stream, which gradually infers higher-level features encoded by the lower number of neurons. However, it is still unclear how neural networks learn to perform such tasks. Hebbian Learning (HL), a local form of plasticity that uses pre- and postsynaptic activity to change synaptic efficacy, has been used extensively in receptive field models, sparse coding, independent and principal component analysis, an

Surround suppression is ubiquitous in visual processing and perception. Neurophysiology and modeling studies reveal a rich set of spatial context effects in the Primary Visual Cortex, whereby surrounding stimuli nonlinearly modulate (e.g., suppress) the responses of a center target stimulus. Studies suggest that the strength of surround suppression depends on the image statistics of the center and surround pattern. Namely, if the center and surround share similar statistics, the neural responses are more suppressed by the surround. This behavior has been connected to computational benefits suc

…circuits and discover their role in visual processing. Our methods include electrophysiology, computational modeling, and circuit tracing using a variety of imaging techniques.

…Investigations of visual categorization in primates have focused on a hierarchy of cortical areas that transform veridical sensory information into abstract categorical representations. However, categorical behaviors are evident throughout the animal kingdom, including in species without a neocortex, raising a question about the contributions of subcortical regions to primate categorization. One candidate structure is the superior colliculus (SC), a midbrain sensori

…of brain activity, especially of visual processing, which are becoming widely used. Recently it was shown that partial weight sharing can be implemented with a "sleep phase", in which plasticity is anti-Hebb

My laboratory studies how the retina processes visual scenes and transmits this information to the brain. We use multi-electrode arrays to record the activity of hundreds of retina neurons simultaneously in conjunction with transgenic mouse lines and chemogenetics to manipulate neural circuit function. We are interested in three major areas. First, we work to understand how neurons in the retina are functionally connected. Second we are studying how light-adaptation and circadian rhythms alter visual processing in the retina. Finally, we are working to understand the mechanisms of retinal deg

…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