Direction selectivity

…on “ON” (bright stimuli) motion selectivity using connectome-constrained deep mechanistic networks (DMNs) of the fly visual system. DMNs feature a one-to-one corre

…By measuring feature selectivity 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

Animals must infer the three-dimensional structure of the surrounding world from two-dimensional images on their retinas. 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

Feedback mechanisms are pervasive across the nervous system, regulating neural networks through the backpropagation of information at different levels. Neuroanatomical data have shown the presence of feedback neurons within the visual system of $\textit{Drosophila}$, where information such as visual motion is extracted. However, prevailing models of motion detection, as well as other visual features, rely on feedforward networks, so far neglecting feedback adjustments originating from higher hierarchical levels. The functional significance of feedback circuits, particularly inhibitory feedback

Activity of sensory neurons is driven not only by stimuli but also by the behavior of the animal. For example, in the primary visual cortex (V1) of a mouse, the gain of sensory responses is modulated by the speed of movement [1]. On average, the response strength increases with running speed - this effect is prominent and systematic. Individual neurons can, however, reveal distinctive patterns of gain modulation. This diversity raises questions about how nuanced the impact of behavior on sensory coding is, whether it is limited to coarse gain changes, and what its computational function might

A primary goal in systems neuroscience is to understand how neuronal connectivity impacts the activity and dynamics in mechanistic models of neural processing. New connectome datasets of the fruit fly provide access to the connectivity of every neuron in its neural circuits. However, the functional role of recurrent connections in the fruit fly remains incompletely understood. For instance, although its visual system is predominantly feedforward, strong feedback connections have been identified in its motion detecting pathways [1]. What is the role of recurrent connections in the visual percep

…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

Postsynaptic density protein 95 (PSD-95) is an important signalling scaffold of the PSD of excitatory synapses. We have previously shown that PSD-95 dependent silent synapse maturation closes the critical period (CP) for ocular dominance plasticity in mouse V1: PSD-95 KO mice display both functional & structural hallmarks of CP plasticity and synapses cannot properly stabilize. Since the development of binocularity happens during the CP, we hypothesized that PSD-95 KOs should display compromised binocular integration. To test this hypothesis, we performed both behavioural experiments and m

The retina processes and transmits visual signals throughout a defined neuronal circuit to retinal ganglion cells, which project to the visual centers of the brain. Microglia have been shown to fine-tune the neuronal circuitry by pruning functionally weak synapses during brain development. However, we do not know whether microglia have a similar impact on the neuronal circuit of the retina.In mice, microglia invade the developing retina as early as embryonic age (E) 11.5, where they reside in in the emerging outer- (OPL) and inner plexiform layer (IPL) throughout adulthood. Here, we investigat

Detecting the direction of image motion is important for visual navigation, predator avoidance and prey capture, and thus essential for the survival of all animals that have eyes. However, the direction of motion is not explicitly represented at the level of the photoreceptors: it rather needs to be computed by subsequent neural circuits, involving a comparison of the signals from neighboring photoreceptors over time. The exact nature of this process represents a classic example of neural computation and has been a longstanding question in the field. Much progress has been made in recent years

Detecting the direction of image motion is important for visual navigation, predator avoidance and prey capture, and thus essential for the survival of all animals that have eyes. However, the direction of motion is not explicitly represented at the level of the photoreceptors: it rather needs to be computed by subsequent neural circuits. The exact nature of this process represents a classic example of neural computation and has been a longstanding question in the field. Our results obtained in the fruit fly Drosophila demonstrate that the local direction of motion is computed in two parallel

Cells preferentially responding to visual motion in a particular direction are said to be direction-selective, and these were first identified in the primary visual cortex. Since then, direction-selective responses have been observed in the retina of several species, including mice, indicating motion analysis begins at the earliest stage of the visual hierarchy. Yet little is known about how retinal direction selectivity contributes to motion processing in the visual cortex. In this talk, I will present our experimental efforts to narrow this gap in our knowledge. To this end, we used genetic

…tend to propagate towards the caudal direction (Gribizis et al., 2019) have impacts on the directio

Visual motion provides us with rich cues about the three-dimensional structure of our environment. However, it is generally unknown how circuits of neurons decode spatial information carried by patterns of visual motion. Here, we study the neural mechanisms of a collision avoidance behavior in walking Drosophila fruit flies as a simple model of motion-based spatial vision. In psychophysical experiments, we observed that flies exhibit slowing upon encountering small objects moving back-to-front in the frontolateral visual field. With a simple simulation, we demonstrate that this slowing can be

Despite the recent success of deep learning in artificial intelligence, the lack of biological plausibility and labeled data in natural learning still poses a challenge in understanding biological learning. At the other extreme lies Hebbian learning, the simplest local and unsupervised one, yet considered to be computationally less efficient. In this talk, I would introduce a novel method to infer the form of Hebbian learning from in vivo data. Applying the method to the data obtained from the monkey inferior temporal cortex for the recognition task indicates how Hebbian learning changes th

The ability to encode the direction of image motion is fundamental to our sense of vision. Direction selectivity along the four cardinal directions is thought to originate in direction-selective ganglion cells (DSGCs), due to directionally-tuned GABAergic suppression by starburst cells. Here, by utilizing two-photon glutamate imaging to measure synaptic release, we reveal that direction selectivity along all four directions arises earlier than expected, at bipolar cell outputs. Thus, DSGCs receive directionally-aligned glutamatergic inputs from bipolar cell boutons. We further show that this b