Visual feature competition between central and peripheral retinal pathways’

Washington University, Saint Louis MO

Investigators

Abstract

Project Summary/Abstract Eye fixation enables us to see details of objects that require current attention using a specialized region in the retina called high-acuity area (or the fovea in humans). During eye fixation, visual inputs detected in the peripheral retina that may induce disruptive reflexive eye movements, such as optokinetic reflex (OKR), are suppressed. Eye movement and fixation are often disrupted in degenerative diseases in the early visual system (e.g. partial macular degeneration) as well as in high-order neural disorders. However, how the visual signals that evoke these two eye movements interact at the beginning of the vision, in the eye, is not well understood. In the eye, photoreceptors capture pixel representation of the visual scene. These signals are processed and transformed into visual feature representation, such as object motion, which triggers eye fixation, and background movement, which triggers OKR, in the retina before being sent to the brain. We hypothesize that these two visual feature signals interact with each other in the retina. To investigate this, we will use larval zebrafish as a model system. As larval zebrafish are transparent and easy to generate transgenic animals, this system uniquely allows us to optically record and optogenetically control neural activity throughout the visual system in behaving animals. This research will be the first to carry out such analysis in the retina. We will first behaviorally assess whether larval zebrafish can perform eye fixation in the presence of background movements. Next, using two-photon imaging of neural activity, we will identify the neural pathways that process eye fixation and OKR-evoking signals in the retina and retinal-recipient areas. Finally, by simultaneously recording behavior and neural activity in the eye and the brain, we will reveal how and where along these pathways, eye fixation and OKR-evoking signals interact with each other for selecting behaviors. Neural mechanisms underlying individual feature extraction in the retina have been extensively studied. Furthermore, these studies revealed that some of the feature signals are directly linked to behavior, such as OKR and eye fixation. However, in nature, we face visual scenes with multiple features that may compete with each other for behaviors, and the extent to which the neural basis of this computation is based in the early visual system, including the retina and retinal recipient areas of the brain, is less understood. By providing new fundamental knowledge about the circuitry and logic underlying the competition between central and peripheral vision, this project has broad implications for both normal and pathological vision.