Visual motion

…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

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

The ability to encode visual motion information is an essential prerequisite for organisms to navigate their surroundings. For example, animals need to detect whole-field motion in order to stabilize themselves within their environment. While it is known that some features of naturalistic motion such as its directionality are already extracted in the retina, it is still unclear whether all the necessary cues are already available at these early stages. Here we take advantage of the optomotor response (OMR) behavior in the larval zebrafish to study how these animals respond to whole-field motio

…circuits that selectively encode visual motion. In both flies and mice, early visual circuits separately detect the movement of light and dark edges. Strong parallels have been noted between the two systems in their anatomy, circuitry, and the suite of computations that they perform. However, because their direction-selective cells have different morphologies and employ different neurotransmitters and receptors, the similarities between them exist not at the molecular level, but at the algorithmic level. While similarities in the

The processing of natural visual environments rich with motion is central to animal survival. Many aspects of perceiving and detecting visual motion are already mature before the onset of visual experience. How the visual system develops to enable these functions in the absence of external stimuli remains unclear. A prominent transient feature of developing circuits is the ability to generate complex spatiotemporal patterns of spontaneous activity, even before sensory organs mature. For example, before vision onset in the mammalian retina, activity propagates in the form of spatiotemporally st

Self-motion through a visual world creates a pattern of expanding visual motion called optic flow. Heading estimation from the optic flow is accurate in rigid environments. But it becomes challenging when other humans introduce an independent motion to the scene. The biological motion of human walkers consists of translation through space and associated limb articulation. The characteristic motion pattern is regular, though complex. A world full of humans moving around is nonrigid, causing heading errors. But limb articulation alone does not perturb the global structure of the flow field, matc

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

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

…area of the neocortex that processes visual motion, even weak motion signals evoke selective responses in the presence of noise. We also observe tuned patterns of activity in the absence of visual motion that suggest feature-selective amplification within the circuit. In addition, respo

Evolution has endowed primates, including humans, with a powerful visual system, seemingly providing us with a detailed perception of our surroundings. But in reality the underlying process is one of active filtering, enhancement and reshaping. For visual motion perception, the dorsal pathway in primate visual cortex and in particular area MT/V5 is considered to be of critical importance. Combining physiological and psychophysical approaches we have used the processing and perception of visual motion and area MT/V5 as a model for the interaction of sensory (bottom-up) signals with cognitive (t

…of state such as hunger and locomotion. On internal state-modulation of sensory processing, I have shown how hunger alters visual motion processing in blowflies (Longden et al. 2014), and identified a role for octopamine in modulating motion vision duri

Many visual systems can process information in dynamically changing environments. In general, visual perception scales with changes in the visual stimulus, or contrast, irrespective of background illumination. This is achieved by adaptation. However, visual perception is challenged when adaptation is not fast enough to deal with sudden changes in overall illumination, for example when gaze follows a moving object from bright sunlight into a shaded area. We have recently shown that the visual system of the fly found a solution by propagating a corrective luminance-sensitive signal to higher pro