Gene R. Stoner - US grants

DESCRIPTION (Adapted From The Applicant's Abstract): Unlike stimuli used in traditional neurophysiological experiments most natural scenes have many objects that occlude one another. The ability to decompose these scenes into component objects depends on the proper detection and grouping of object parts. This perceptual process, termed figure-ground interpretation is central to the healthy function of the visual system. It has been hypothesized that figure-ground interpretation occurs relatively early in the visual processing stream. Correspondingly, one objective of the proposal is to determine whether neurons in cortical areas V1, V2 and MT are sensitive to the same stimulus manipulations that influence the perception of figure-ground. Results from behavioral studies have demonstrated that the veridical perception of motion in complex dynamic scenes depends upon figure-ground interpretation. Recent neurophysiological data suggest that changes in figure-ground interpretation alter the response properties of directionally selective neurons in cortical area MT. Hence, a second objective of this proposal is to characterize the interaction between figure-ground and visual motion processing in area MT. These objectives will be achieved by the application of several novel visual displays that simulate simple occlusion of one object by another. Use of combined behavioral and neurophysiological techniques will establish a correspondence between perceptual and neural events. Results from these experiments will lead to more refined models of visual processing and aid in the development of artificial sensory systems. In addition, the research will provide important information for the treatment of brain-damaged and disease conditions that disrupt visual function.

DESCRIPTION (provided by applicant): The long-term goal of this research is to understand the neural mechanisms underlying the perception of complex natural scenes in healthy and diseased visual systems. Unlike the stimuli used in traditional neurophysiological studies, most natural images are composed of multiple, frequently overlapping, objects. The ability to segment these images into component objects depends upon the detection and interpretation of regions of object overlap. This process is referred to as figure-ground interpretation. One objective of this proposal is to understand the neuronal basis of figure-ground interpretation. A physically salient object can be perceptually suppressed by the presence of another more salient object. This suppression underlies the ability to select one object as a target for action while ignoring other objects. A second objective of this proposal is to understand the neuronal mechanisms underlying this suppression. To achieve these objectives, a number of novel visual displays have been developed. To establish a correspondence between perceptual and neuronal events, a combination of behavioral and neurophysiological techniques will be used. Results from these experiments will lead to more refined models of visual processing and aid in the development of artificial sensory systems. In addition, this research will provide information for the treatment of brain-damaged and disease conditions that disrupt visual function.

DESCRIPTION (provided by applicant): One of the fundamental unanswered questions of sensory biology is how information provided by individual neurons within the brain is linked into a coherent whole. Individual visually responsive neurons only respond to stimulation over a limited portion of the visual image known as the receptive field. The proposed research addresses the question of how the visual system integrates this limited information into an accurate representation of that world. Specifically, this research focuses on the ability of the visual system to selectively integrate information that arises from the same visual object. The conventional view has been that visually responsive neurons have relatively fixed neuronal properties that are stimulus independent. Based on recent discoveries, this research hypothesizes instead that neurons adapt their response properties such that they selectively integrate only that information that arises from the same perceptual object. This research explores this hypothesis as it applies to the perception of visual motion and depth. The ability to appropriately integrate visual information is intrinsic to normal visual perception and cognition, and disruptions of that ability accompany ageing and mental pathologies such as schizophrenia. This research thus promises to provide insight into normal mental function and is pertinent to developing treatments of mental pathologies. The long term goal of this project is to provide insight into the neural events that underlie our perception of the world. Our detailed understanding of the brain mechanisms that underlie normal perception will ultimately aid the treatment and prevention of neurological and psychiatric disorders. These aims are pertinent to the development of prosthetic and behavioral therapies for the visually handicapped.

DESCRIPTION (provided by applicant): Optogenetics refers to a cutting-edge set of molecular methods that allows for light-based control of targeted neurons in intact brains. These methods have immense potential as a basic research tool to determine the role of specific neuronal populations in healthy and abnormal brain function. In addition, further development of these methods may lead to new types of treatments for neurological and psychiatric disorders, as well as a new class of prostheses for those with sensory impairments. This project is aimed at further developing these methods so that they can achieve their basic research and clinical potential. This proposal introduces key improvements in the molecular methods as well as fundamental improvements in their application to the study of higher-order perceptual and cognitive functions. Critically, the approach of this proposal is minimally invasive and hence, unlike previous methods, causes little to no tissue damage. In addition, the improvements introduced by this proposal allow for more precise targeting of neurons and more potent control of the responses of those neurons. This proposal uses these methods to systematically determine their efficacy at both the neuronal and the behavioral levels. A key innovation of this approach is the development of an optogenetic window. This window will permit long-term health of the cortex, functional mapping prior to delivery of molecular agents, precise targeting of molecular agents to specific functional sites, and assessment with established optical imaging, electrophysiological, and behavioral methods. This proposal will allow patterns of neuronal modulation (both inhibitory and excitatory) to be related to specific perceptual and behavioral effects. The successful completion of this project will have enormous benefits for basic research into higher-order perceptual and cognitive functions, and will provide a solid foundation for the development of new treatments for the sensory impaired as well as those with psychiatric or neurological disorders. PUBLIC HEALTH RELEVANCE: The long-term goal of this project is to provide insight into the neuronal mechanisms that underlie perception and cognition. This project will provide methods and knowledge that will aid in the treatment and prevention of neurological and psychiatric disorders. These aims are also directly relevant to the development of prostheses for the visually handicapped.