David H. Brainard - US grants

The visual system adjusts to stabilize object color appearance against changes in illumination. This proposal consists of experiments designed to study the adjustment, which is often called color constancy. Understanding color constancy is necessary for a complete theory of human color vision. In addition, color constancy is an example of a larger class of perceptual constancies (e.g. size constancy and shape constancy) that together allow us to perceive a stable physical world. As such, a detailed characterization of the color system may provide insights that generalize to these other perceptual systems. The first set of experiments is designed to characterize performance for natural viewing conditions. In these experiments the stimuli will consist of real illuminated objects. Asymmetric color matching procedures will be used to provide quantitative data. The results of the first set of experiments will be compared with similar data obtained using computer graphics simulations as stimuli. The purpose of this comparison is to establish whether computer graphics technology provides a valid method for studying real world color performance. Because many image parameters are technically difficult to manipulate and control in real images, a valid graphics simulation would make a richer set of experimental manipulations possible. The third set of experiments is designed to measure the action of early color mechanisms for spatially complex stimuli. To isolate early mechanisms, the stimuli will consist of multiple uniformly colored regions. These stimuli have the advantage that they can be described by a relatively small number of parameters. The proposed experiments are designed to provide quantitative tests of qualitative principles that might govern mechanisms of chromatic adaptation and simultaneous color contrast. If valid, these principles allow a finite set of measurements to predict the joint action of the mechanisms for a broad class of images. A final experiment is designed to ask whether early visual mechanisms are independent from higher-level processes that parse the image into objects and illuminants. If so, then the results of the proposed research can be used to determine the degree to which measured real image color constancy can be explained by the action of early mechanisms.

[unreadable] DESCRIPTION (provided by applicant): DED. Vision is useful because it informs us about physical properties of the environment. In the case of color, one important function is to provide information about object identity - color is generally considered a perceptual correlate of object surface reflectance. For color to be a reliable guide to object identity, the perceived color of an object must remain stable across variations in the scenes in which it is viewed. This requirement is non-trivial because the light reflected to the eye varies with scene factors that are extrinsic to the object, such as the spectrum of the illumination and the reflectance of nearby objects. The visual system adjusts to stabilize (partially) object color appearance against changes in these extrinsic factors, a phenomenon called color constancy. This proposal consists of experiments designed to study object color appearance and its constancy. Color constancy is an example of a larger class of perceptual constancies (e.g. size constancy and shape constancy) that together allow us to perceive a stable physical world. As such, a detailed characterization of the color system may provide insights that generalize beyond color per se. The proposed research consists of behavioral experiments with human observers that will allow a functional characterization of how we perceive object color. Questions to be addressed include a) how does the visual system integrate information across the surface of a three-dimensional object to arrive at an overall percept of object color? b) how is this process affected by variations in the material properties of objects (i.e. variations in the object's bidirectional reflectance distribution function)? c) how stable is object color perception across variation in object shape and pose? d) how does object color perception depend on geometrical and spectral properties of the illumination? e) can we model color perception within a computational framework derived from inverse optics? and f) what role do mechanisms of adaptation tapped by objective threshold measurements play in object color constancy across changes in complex scenes? This research should help us understand how color vision works in the real world and provide a foundation for clarifying the neural processing of color. [unreadable] [unreadable]

biomedical equipment

? DESCRIPTION (provided by applicant): The broad goal of this proposal is to provide core support services for 21 Participating Investigators and over 30 Associate Investigators to: (1) enhance the quality and quantity of their research; (2) facilitate collaborations between investigators with different backgrounds and skills; and (3) recruit new investigators to vision research, help young vision investigators establish their labs, and allow established investigators to explore new directions. Participating Investigators hold 25 individual R01 research grants from the National Eye Institute, and Associate Investigators study vision but do not currently hold an R01 grant from the NEI. Collectively, the investigators represent a broad range of vision research, and include experts on animal models of retinal degeneration, retinal circuitry, gene therapy, cell and molecular biology, molecular genetics, eye, central visual pathways and cortical physiology, visual performance and cortical function in awake- behaving primates, cognitive neuroscience of vision, computational modeling, and visual psychophysics. The core grant will support 5 resource/service modules: Biostatistics provides expert assistance in experimental design and data analysis, particularly for clinical studies, as well as bioinformatics support; Image Analysis provides expert support for the development and implementation of image processing and analysis solutions, as well as other data analysis services; Imaging and Electrophysiology provides vision investigators access to shared equipment and technical support for a variety of imaging modalities and electrophysiological recording, including conventional and two-photon confocal microscopy, multi-electrode array recording from in vitro tissue, and spectral OCT imaging; Instrumentation provides for design and construction of custom stimulus delivery, data acquisition, and electrophysiological instruments that are unavailable from commercial sources, as well as maintenance and repair of such instruments; Noninvasive Assessment of Visual Function provides equipment and technical support for assessing visual function in animal models. Methods include ERG, pupillometry, and water maze testing of vision.

This Integrative Graduate Education and Research Training (IGERT) award to the University of Pennsylvania supports the development of a new training paradigm for perception scientists and engineers, and is designed to provide them with a unique grasp of the computational and psychophysical underpinnings of the phenomena of perception. It will create a new role model of a well-rounded perceptual scientist with a firm grasp of both computational and experimental analytic skills. The existence of such a cadre of U.S. researchers will contribute to the country's global competitiveness in the growing machine perception and robotics industry.

Research and training activities are organized around five thematic areas related to complex scene perception: (1) Spatial perception and navigation; (2) Perception of material and terrain properties; (3) Neural responses to natural signals, saliency and attention; (4) Object Recognition in context and visual memory; and (5) Agile Perception. Interdisciplinary research will enable new insights into the astounding performance of human and animal perception as well as the design of new algorithms that will make robots perceive and act in complex scenes.

IGERT trainees will commit in advance of acceptance to a five-year graduate training program, comprising the following components: (1) Core disciplinary training; (2) one-year cross-disciplinary training in a chosen second discipline; (3) participation in two foundational and one integrational IGERT courses; (4) attendance of an interdisciplinary IGERT seminar; (5) co-advising throughout the 5 graduate years by an interdisciplinary faculty team ; and (6) completion of the Ph.D. dissertation.

IGERT is an NSF-wide program intended to meet the challenges of educating U.S. Ph.D. scientists and engineers with the interdisciplinary background, deep knowledge in a chosen discipline, and the technical, professional, and personal skills needed for the career demands of the future. The program is intended to catalyze a cultural change in graduate education by establishing innovative new models for graduate education and training in a fertile environment for collaborative research that transcends traditional disciplinary boundaries.

DESCRIPTION (provided by applicant): The broad goal of this proposal is to provide core support services for 26 Participating Investigators and 24 Associate Investigators to: (1) enhance the quality and quantity of their research;(2) facilitate collaborations between investigators with different backgrounds and skills;and (3) recruit new investigators to vision research, help young vision investigators establish their labs, and allow established investigators to explore new directions. Participating Investigators hold P30-qualifying individual research grants from NEI, and Associate Investigators hold individual grants from other sources or are applying for funding. Collectively the investigators represent a broad range of vision research, and include experts on animal models of retinal degeneration, retinal circuitry, gene therapy, cell and molecular biology, molecular genetics, eye, central visual pathways and cortical physiology, visual performance and cortical function in awake-behaving primates, cognitive neuroscience of vision, computational modeling, and visual psychophysics. The core grant will support 5 modules: Biostatistics provides expert assistance in experimental design and data analysis particularly for clinical studies;Image Analysis provides expert support for the development and implementation of image analysis solutions;Instrumentation provides for design and construction of optical and electrophysiological instruments that are unavailable from commercial sources;Noninvasive Assessment of Visual Function provides equipment and technical support for assessing visual function in animal models and humans. Principle methods include ERG, pupillometry, and psychophysics;Shared Imaging Equipment provides vision investigators access to shared equipment for a variety of imaging modalities, including conventional and two-photon confocal microscopy, multi-electrode array recording from in vitro tissue, and confocal SLO combined with spectral OCT imaging of in vivo retina.

Administrative ? Project Summary The Administrative Core Module provides the overall supervision and management of Penn?s Core Grant for Vision Research. This will be accomplished under the leadership of the PI, Dr. Brainard. Dr. Brainard is assisted by an Executive Committee consisting of the core module directors and other senior vision investigators at Penn. The Executive Committee has two primary administrative functions. The first is to monitor the projects of the core grant scientific staff, and provide direction and coordination with respect to these projects. As part of this, the Executive Committee collectively is aware of the full scope of vision research at Penn as well as the projects being supported by the core modules, and is alert to the possibility of identifying opportunities for collaboration between Penn vision investigators. The second EC function is to oversee the management of the core grant itself. In addition, staff support is provided through the Administrative Core Module for managing budgets, scheduling events, and preparing reports. Although disputes are not expected, formal procedures are provided for resolving any such disputes.

? DESCRIPTION (provided by applicant): A symptom of many ophthalmologic and neurologic disorders is photophobia: discomfort and pain from flickering and bright lights. More specifically, photophobia is a key symptom in patients with migraine, both during headache and also in the headache-free inter-ictal period. This clinical observation has been confirmed by systematic behavioral studies demonstrating lower discomfort thresholds for visual stimulation in such patients. There is also evidence that some forms of visual discomfort may be related to signals from intrinsically photosensitive retinal ganglion cells (ipRGCs) that contain the photopigment melanopsin. The three aims of this proposal will test the hypothesis that photophobia associated with migraine headache is related to altered responses to stimulation of melanopsin, as well as characterize the photoreceptor mechanisms that mediate the documented elevated neural response to light observed in migraine with aura. All three aims will employ a digital light integrator to produce spectral modulations that selectively and robustly stimulate individual photopigment classes. We will measure the effect of stimulation directed separately at melanopsin and the cone photoreceptors, as well as interactions between melanopsin and cone signals. Aim 1 will examine direct effects of melanopsin stimulation in healthy human subjects, using three distinct but complementary response measures: behavioral reports of visual discomfort and perception of brightness, fMRI and the pupillary light response. We will examine the specific role of melanopsin in behaviorally-assessed visual discomfort and brightness perception, measure sustained brain responses to direct melanopsin stimulation, and use the pupillary light response to assess individual differences in melanopsin responsivity as well as the stability of these differences over time. Aim 2 will also study healthy control subjects and characterize whether and how melanopsin signals interact with signals from cones, to regulate the response to cone-mediated light flicker. We will measure psychophysical thresholds for detection of cone-mediated flicker and assess how these are affected by changes in the melanopic component of an adapting background light, use fMRI to measure neural correlates of the psychophysical effects, and employ a novel paradigm that allows us to use the sluggish pupillary light response to test the hypothesis that melanopsin signals regulate the response to cone-mediated flicker at an early site along the visual pathways. Aim 3 will build on the results of Aims 1 and 2 to characterize the photoreceptor mechanism of the enhanced neural response to light observed in migraine with aura. We will also measure whether the migraineurs demonstrate systematic differences with controls in either the direct or interactive effects of melanopsin, and whether such differences are related to the enhanced light sensitivity of this patient population.

Overall - Project Summary The broad goal of this proposal is to provide core support services for 16 Participating Investigators and over 40 Associate Investigators to: (1) enhance the quality and quantity of their research; (2) facilitate collaborations between investigators with different backgrounds and skills; and (3) recruit new investigators to vision research, help young vision investigators establish their labs, and allow established investigators to explore new directions. The Participating Investigators hold 18 qualifying R01 research grants from the National Eye Institute. The Associate Investigators study vision but do not currently hold a qualifying R01 grant from the NEI. Collectively, the investigators represent a broad range of vision research, and include experts on animal models of retinal degeneration, retinal circuitry, gene therapy, cell and molecular biology, molecular genetics, eye, central visual pathways and cortical physiology, visual performance and cortical function in awake- behaving primates, cognitive neuroscience of vision, computational modeling, and visual psychophysics. The core grant will support 4 resource/service modules: Biostatistics provides expert assistance in experimental design and data analysis, particularly for clinical studies, as well as bioinformatics support; Imaging and Electrophysiology provides vision investigators access to shared equipment and technical support for a variety of imaging modalities and electrophysiological recording, including conventional and two-photon confocal microscopy, multi-electrode array recording from in vitro tissue, and spectral OCT imaging; Instrumentation provides for design and construction of custom stimulus delivery, data acquisition, and electrophysiological instruments that are unavailable from commercial sources, as well as maintenance and repair of such instruments; Scientific Transparency develops novel software tools for pre-processing, analysis, and presentation of imaging data, and supports data curation and analysis reproducibility.