Vision research at Rochester is organized into three major themes:
- The neural mechanisms that underlie visual experience,
- the role of vision in guiding behavior,
- and advanced technologies of ophthalmic optics.
Most faculty in CVS contribute to two or more of these themes.
CVS had been built on the conviction that progress in vision science requires the coordinated efforts of scientists with very different skills. Researchers in the center apply a number of approaches to their research; many apply more than one. Core methodological foci are:
- advanced neuroscience methods
- behavioral and psychophysical methods
- computational analysis and modeling
- advanced optical techniques
Researchers in CVS have been at the forefront in developing advanced scientific techniques, including multi-electrode recordings in awake-behaving monkeys, virtual reality tools for studying complex visuomotor behaviors, advanced mathematical analysis of behavioral and neural data, and the application of adaptive optics to basic and clinical vision research.
Richard Aslin : Perceptual learning and development
Aslin is interested in the processes and mechanisms that lead to the development of sensory, perceptual, and cognitive abilities in human infants. A line of work that grew out of studies of auditory sequence learning has investigated how adults, children, and infants group sequentially presented elements based solely on the distributional cues (conditional probabilities) contained in the stream of elements. Element-sequences have consisted of simple 2-D shapes, as well as spatially defined locations in a serial reaction time task.
His most recent work has extended this rapid statistical learning from the temporal to the spatial domain by presenting elements simultaneously, thereby creating configurations defined by their spatial correlation. Both adults and human infants are remarkably sensitive to these spatial correlations in multi-element scenes, and on-going work is using eye-tracking to reveal the attentional constraints on statistical learning. Students are trained in the use of psychophysical methods adapted to assess perceptual performance in infants and young children.
Mina Chung : Inherited retinal diseases and genetic factors contributing to age-related macular degeneration
Dr. Chung's research interests include inherited retinal diseases and genetic factors contributing to age-related macular degeneration. Dr. Chung has an adjunct faculty appointment as a member of the University of Rochester Center for Visual Sciences and participates in teaching a graduate-level course in the Department of Optics.
In collaboration with CVS, she is developing new adaptive optics technology for retinal imaging to study early cellular changes in macular diseases. She was awarded a research grant from the Howard Hughes Medical Institute to study patients with macular diseases using adaptive optics imaging technology and multifocal electroretinography, a clinical test of the retinal photoreceptors.
Greg DeAngelis : Neural basis of 3D visual perception and multi-sensory cue integration
The main goal of work in the DeAngelis lab is to understand the neural basis of visual perception and visually-guided behavior. A major challenge is to understand how the brain computes the location and movement of objects in three-dimensional space, and how these computations take into account motion of the observer. The approach is to link neuronal activity to perception as closely as possible using a combination of electrophysiology and psychophysics in alert trained monkeys.
Major emphasis is placed on establishing causal links between neural activity and behavior using techniques such as electrical microstimulation and reversible inactivation. Current research in the DeAngelis lab has 3 main foci:
- neural mechanisms of depth perception from binocular disparity and motion parallax;
- neural substrates of multisensory (visual/vestibular) integration for self-motion perception; and
- neural mechanism of optimal (i.e., Bayesian) cue integration.
Students in the lab are trained in quantitative electrophysiology and psychophysics, statistical analysis of neural and behavioral data, and computational modeling of neural population codes.
Charles Duffy : Neural processing of motion, spatial orientation
Duffy studies the activity of extrastriate visual areas, using single unit recordings in awake macaques and psychophysical methods in humans and macaques to examine mechanisms of spatial orientation. Past work has demonstrated the existence of neurons that are specifically activated during the viewing of optic flow fields and other complex motions, and this work has shown that the viewing of optic flow produces illusions that provide powerful insights into the neural mechanism involved. Future experiments will use feedback controlled full field visual stimulators and sled induced vestibular stimulation to study mechanisms of spatial orientation in healthy monkeys and humans and diseased humans. Students are trained in single unit recording in awake monkeys performing visual tasks, and in the analysis of simultaneous visual and vestibular stimulation.
Steven Feldon : Orbital disease and neuro-ophthalmology
Dr. Feldon's research interests involve using his expertise in thyroid eye disease to investigate the role of fibroblasts in Graves' disease. In a collaborative effort with Dr. Richard Phipps, the aim is to develop a model of how immune system cells interact with orbital fibroblasts. The hope is to develop rational therapy treatments for this and possibly other autoimmune diseases affecting eye structures. Dr. Feldon's directs an ophthalmology photographic reading center for federal, industry, and foundation sponsored clinical trials. Current studies evaluate Thyroid Eye Disease and Idiopathic Intracranial Hypertension. He also collaborates with Dr. Krystel Huxlin on mechanisms of visual restoration after stroke. In addition he is an inventor of devices for ophthalmology including tonometers and holds seven patents.
Jim Fienup : Image processing, wavefront sensing
Professor Fienup's research interests center around imaging science. His work includes unconventional imaging, phase retrieval, wavefront sensing, and image reconstruction and restoration. These techniques are applied to passive and active optical imaging systems, synthetic-aperture radar, and biomedical imaging modalities. His past work has also included diffractive optics and image quality assessment.
Edward Freedman : Neural control of coordinated movements
In order to interact with objects in our environment we must be able to gather accurate sensory information about our surroundings, distinguish our movements from the movements of objects in the world, and coordinate our own movements in order to orient, and navigate smoothly through a complex environment. In my lab we study the neural control of coordinated orienting behaviors including gaze shifts and pursuit of stationary and moving targets in the head-unrestrained subject. We seek to understand the roles of neurons in the brainstem, cerebellum and cortex in generating and executing these movements within the context of testing critical predictions of models (i.e. hypotheses) of these critical sensorimotor control systems.
Lin Gan : Development of mammalian retina and inner ear
Human retina and inner ear are the most common places of genetic disorders that cause blindness and deafness due to the degeneration of retinal and inner ear neurons. To understand the disease processes, the research in our Laboratory focuses on elucidating the molecular mechanisms regulating the normal development and maintenance of these neurons. We have been investigating the roles of three classes of transcription factors (TFs), the basic helix-loop-helix (bHLH), POU-homeodomain (POU-HD), and LIM-domain TFs, in mouse retina and inner ear. Using homologous recombination in mouse embryonic stem (ES) cells to mutate these TF genes, we have shown that these TFs function in a genetic cascade to regulate the differentiation of neuronal progenitor cells into specific types of neurons and to regulate the maturation and survival of post-differentiation neurons. We intend to explore the application of these factors in neuronal protection and in the regeneration of specific retinal and inner ear neurons from stem cells.
Ralf Haefner : Perceptual decision-making
My primary scientific interest lies in understanding how the brain forms percepts and how it uses them to make decisions, especially in the visual domain. In particular, I am interested in how the brain's perceptual beliefs about the outside world are represented by the responses of populations of cortical neurons. To that end I use tools from machine learning to construct mathematical models that aim to explain neural responses and behavior.
Benjamin Hayden : Neural basis of decision-making
We are constantly confronted with choices: What should we eat? How should we allocate our time? Where should we go next? Should we follow a safe path or a risky one that offers a potentially larger payoff? The brain has evolved sophisticated machinery to balance competing interests to make beneficial choices. Our lab wants to know how the brain solves these problems - and why it fails so often. Specifically, we are interested in identifying the neural calculations that promote adaptive decision-making, especially when rewards are involved. To do this, our lab records the activity of single neurons during simple eye movement choices. To eye movement system is particularly appealing because the underlying control circuitry is well-understood.
Holly Hindman : Corneal wound healing, ocular optics, and keratoplasty procedures
Dr. Hindman is a clinician-scientist whose clinical expertise is in the treatment of cornea and ocular surface disease and in their surgical management with various types of corneal transplantation procedures. Dr. Hindman's research interest is in exploring the reason for post-operative limitations in visual function following these procedures. In collaboration with Dr. Krystel Huxlin, Dr. Geunyoung Yoon, and Dr. Richard Phipps, she is identifying the role of keratocyte activation into scar-forming myofibroblasts on post-operative ocular optics and on visual performance. Her lab uses a three-pronged approach to investigate their hypotheses – cell biology studies of corneal wound healing, prospective clinical studies, and prospective experimental studies.
Jennifer Hunter : Mechanisms of light-induced retinal damage, Development of non-invasive fluorescence imaging techniques
Dr. Hunter's research interests include mechanisms of light-induced retinal damage and development of non-invasive fluorescence imaging techniques to study retinal function in healthy and diseased eyes.
Krystel Huxlin : Improving vision after damageperceptual learning and physiological optics
Broadly, my research is focused on better understanding how the damaged, adult visual system can repair itself. Is the system capable of such plasticity? What are the principles governing such processes?
Our first research avenue examines neuronal changes that underlie and behavioral properties that characterize recovery of visual functions after visual cortex damage in adulthood. Psychophysical techniques are used to both measure and retrain visual performance following damage to the visual cortex. In the past, neurochemical studies in an animal model allowed us to then correlate neuronal changes with the degree and type of visual recovery attained as a function of training. For the last 10 years, we have applied this knowledge to humans with cortical blindness (in the form of hemianopsia or quadrantanopsia). In addition to behavioral characterization of the properties of the recovery that can be attained with different training paradigms, we are interested in using attentional and other manipulations (e.g. transcranial magnetic stimulation, pharmacology) to enhance the recovery potential of the damaged visual system. Functional MRI is then used to study how the remaining cortical circuity is altered by both damage and subsequently, by training. It is hoped that this body of work will not only improve our understanding of the plasticity inherent in brain-damaged individuals with vision loss, but will also ultimately improve how we treat this underserved patient population in the clinic.
Our second research avenue studies the interplay between corneal wound healing and optical quality of the eye. The eye is the sensory input to the entire visual system and it relies on a transparent and properly-shaped cornea. If the cornea is damaged, this impairs all of vision. Our laboratory is unique in having developed a behaviorally fixating animal model in which we can reliably measure optical aberrations of the eye with the same degree of precision (and using the same instruments) as in humans. We can then study corneal damage and scarring - one of the major causes of blindness world-wide, and for which there is currently no effective treatment without side-effects. Using our unique animal mode, we can correlate optical aberrations, corneal structure and biology in health and disease. Such complex correlation is essential if we are to gain the knowledge necessary to design better ways of correcting optical aberrations, with minimal side-effects in terms of corneal and ocular health.
By applying the knowledge gained in this work, we are also contributing to the development of what we hope will be a safe, non-damaging form of laser refractive correction. This method is named femtosecond-IRIS or Blue-IRIS. Instead of ablating the cornea to change its shape, IRIS uses a femtosecond laser to alter its refractive index, thus altering the cornea's light-bending properties. This fully-customizable method appears to cause no corneal scarring and opens up both a new area of theoretical investigations into corneal biology related to laser-tissue interactions, and the possibility of creating a whole new paradigm for vision correction in humans.
Robert Jacobs : Visual and multisensory learning and memory; perceptual psychophysics; computational modeling
Jacobs studies perceptual cognition -- learning, memory, recognition, categorization -- in both visual and multisensory (visual-auditory, visual-haptic) environments using behavioral experimentation and computational modeling. Our perceptual environments are highly redundant. People obtain information from multiple sensory modalities (e.g., vision, audition, and touch). Even within visual environments, people obtain information from multiple visual cues (e.g., shading, motion, and texture). This perceptual redundancy raises many important issues. For example, how do people integrate the information provided by multiple sensory sources? How do people know which sources are reliable and which sources are unreliable? Do people integrate the information from multiple sources in a statistically optimal way? As a second example, people often show excellent cross-modal transfer of knowledge. For instance, a person who is trained to visual categorize a set of objects can often categorize those same (and similar) objects when the objects are grasped but not seen. What are the mechanisms underlying cross-modal transfer? Do people represent objects and events in an amodal or modality-independent format? If so, what is the nature of this format? These questions, and many more, are addressed through a combination of experimentation and modeling. Using techniques from the statistics and machine learning literatures, we often build models, known as Ideal Observers, of statistically optimal performance on a task. By comparing the model's performance on this task with people's performances, we can evaluate whether people are behaving in an optimal manner. If not, further experimentation and modeling allows us to probe the "bottlenecks" preventing better performance.
Celeste Kidd : Development, learning, attention, decision-making, computational modeling
Celeste Kidd's work investigates the mechanisms that guide young children's early behavior and learning, with a special focus on attention and decision-making. Her work draws on rational models to make sense of both children's implicit attentional decisions, and overt behavioral decisions (e.g., selecting actions that optimize promised rewards). She employs a range of methodologies including eye-tracking, behavioral experiments, and large-scale eye-tracking corpus studies. A key feature of her approach is the combination of behavioral methods and computational modeling, which allows her to rigorously test competing theories of decision-making and learning by quantifying otherwise unobservable cognitive processes or variables.
Wayne Knox : Femtosecond laser technology for vision
The Knox group is working on new approaches to vision correction including femtosecond micromachining in ophthalmic polymers such as hydrogels and hydrophobic acrylates. They have written various diffractive and refractive structures as well as waveguides into ophthalmic materials with index changes as high as +0.10. The studies may result in new approaches to vision correction involving IOL surgery and other applications. In collaboration with Dr. Huxlin, Knox has carried out studies of refractive index modifications using femtosecond micromachining in live corneal tissue without tissue destruction and cell death. Another area of research involves use of high resolution nonlinear imaging techniques to study diffusion of dopants in the live cornea, and these have potential applications in corneal drug delivery.
Peter Lennie : Functional organization of visual pathways; Mechanisms of color vision
My work sits at the interface between visual perception and visual physiology. All my research is connected by the idea that visual perception can be explained in terms of underlying neural mechanisms. The work involves both perceptual experiments to explore performance, and physiological ones to record the activity of single neurons, the aim being, where possible, to link observations in the two domains. My recent work has focused on two broad problems: how the visual selectivities of neurons become elaborated at successive levels in the visual pathway, and how signals about color are represented in the brain.
Dean Lennie is not mentoring students at this time.
Richard Libby : Neurobiology of Glaucoma
Glaucoma is a complex group of diseases where many different genetic and environmental factors conspire to cause vision loss. While there are many different causes of glaucoma, the ultimate cause of vision loss in all glaucomas is the death of retinal ganglion cells (RGCs), the output neurons of the retina. Therefore, glaucoma is a neurodegeneration. Our lab focuses on the neurobiology of glaucoma. Primarily, we use mouse models of glaucoma and advanced mouse genetics to probe the pathophysiology of glaucoma. Specifically, we are interested in understanding the molecular processes that lead to RGC death in glaucoma and why are RGCs more likely to die in some patients than in others.
Scott MacRae : Refractive surgery
Dr. MacRae's main research is in using wavefront measurements to correct vision beyond the 20/20 level and improve contrast. He works closely with Drs. David Williams and Geunyoung Yoon, as well as industry. While some of his research studies are designed to obtain FDA approval for laser vision correction devices as well as presbyopic intraocular lenses for cataract surgery. His Studies of "customized LASIK" developed the Rochester Advanced Nomogram used by LASIK surgeons around the world. He is also working on improving optics of intraocular lenses that allow patients to see at distance and near after cataract surgery. Based at the state-of-the-art StrongVision clinic, Dr. MacRae combines a specialty refractive surgical practice with his research activities. He has over 25 years experience as a corneal specialist, cataract and LASIK surgeon.
Brad Mahon : Organization of visual object categories in the brain
My principal research focus is on how concepts of common objects are represented and organized in the brain. Most of this research is focused on how concepts are accessed from visual input and how those concepts then interface with other systems, such as the motor system controlling the hands, or language. So for instance, you might look at a glass sitting on the table, and think to yourself that it looks slippery, or reach out to grasp it, or you might say ‘hand me the glass.’ Each of these simple abilities is subserved by dissociable brain systems and is susceptible to selective impairment after brain damage. How is all of this information represented and accessed in the healthy brain, and what happens after the brain is damaged? If a patient loses the ability to use objects according to their function, what happens to linguistic or perceptual knowledge about those objects? Can knowledge that is lost after brain damage be ‘relearned,’ and if so, what are the neural mechanisms that underlie brain reorganization?
Ania Majewska : Imaging synaptic structure and function in the visual system
Our research interests lie in understanding how visual activity shapes the structure and function of connections between neurons in the visual cortex. During the critical period, closure of one eye leads to a shift in the responses of neurons towards the open eye. My lab's current work focuses on the structural basis for this rapid ocular dominance plasticity using in vivo two-photon microscopy to elucidate single cell structure deep in the intact brain. Our experiments suggest that fine scale changes in synaptic connectivity underlie rapid ocular dominance plasticity without an overall remodeling of the pre and postsynaptic scaffold. My lab is also interested in the mechanisms which underlie structural remodeling at synapses. We use imaging, electrophysiology and immunohistochemistry to explore the contributions of different pathways to structural plasticity. We have been studying the influence of microglia, the brain's immune cells, on the remodeling of synaptic structure and network connectivity. We find the microglial processes are highly dynamic and contact synapses in the parenchyma, causing changes in synaptic structure on contact. We believe that microglia are a critical part of the brain network where they aid in synaptic remodeling.
William Merigan : Function of primate extrastriate cortical areas
Merigan's research asks how the complex perceptual abilities of primates are mediated by the neural processing that takes place in the ventral stream of extrastriate visual cortex. He studies texture segmentation, shape recognition, perceptual grouping, visual search and motion perception in macaques and humans, and relates these abilities to the function of particular cortical areas. His recent research has focused on areas V4, TEO and TE in macaques and related areas in humans. Students learn to use localized inactivation, single unit physiology, and perceptual testing to examine the role of these areas in vision.
Jude Mitchell : Primate visual cortex, active vision, perception, and attention
An understanding of information processing at the level of cortical circuits remains a key challenge for understanding the brain and how the dysfunction of its circuits contributes to human mental disease. It has long been appreciated that internal brain states, such as selective attention, can profoundly modulate our perception. For example, when an observer focuses their attention toward a single object, such as a friend at a crowded party, it can lead to an almost complete filtering of the background. My research focuses on the role that internal brain states, such as selective attention, play in modulating sensory processing. In particular, I am interested in the distinct roles that different neuronal classes play in this process.
I have forged a new direction in research developing the smaller New World primate, the marmoset (Callithrix Jacchus), to study active visual perception and attention. The marmoset provides several advantages as a model organism for these studies. First, the marmoset’s visual and oculomotor system is highly similar to that of larger primates and humans. Second, the recent development of transgenic lines in this species has opened many new opportunities for biomedical research. At present, multiple international projects are developing genetic models of human mental disease as well as the methodologies to study their brain physiology. Last, due to their smooth lissencephalic brain, all of the visual and oculomotor areas lie accessible at the cortical surface of the marmoset, much facilitating the use of modern recording methods with planar and laminar arrays. In recent work I have established the necessary techniques for visual behavior and neurophysiology in this species. This opens new opportunities to study visual perception and attention in cortical circuits at a much deeper level.
Gary Paige : Multisensory interaction and adaptive plasticity in spatial localization and orientation
The integration of sensory-neural processes underlying our abilities to localize, track, and interact with a cluttered environment are fundamental attributes of daily life, ranging from mundane tasks such as reaching for objects to complex ones such as navigating to and from the workplace. These functions are also among the first to register problems with disease and aging. The goal of our research is to understand how the brain integrates sensory inputs from the outside world (location and motion of visual and auditory targets) with those of the internal senses (vestibular and somatosensory) to achieve meaningful spatial perceptions and behaviors, particularly eye, head and postural movements. An equally important interest is how plastic neural mechanisms register errors and adaptively adjust performance in order to maintain proper spatial calibration across modalities. Finally, an important translational concern is how natural aging affects both spatial behavior and adaptive plasticity. Our research environment is unique in structure and instrumentation, as well as broad and translational in character. We benefit from a collegiate and multi-disciplinary group of faculty and students working on problems of common interest.
Tatiana Pasternak : Cortical Circuitry Underlying Memory-Guided Visual Decisions
Our research program is aimed at examining cortical circuitry underlying successful execution of sensory comparison tasks involving visual motion. We record the activity of MT neurons specialized in motion processing and of neurons in the lateral prefrontal cortex (LPFC), an area strongly associated with executive function, sensory working memory and attention. We are particularly interested in the still poorly understood influences of the LPFC on sensory cortex. Our experiments are designed to characterize the representation of visual motion in the LPFC and to examine the top-down influences it provides to MT during motion discrimination tasks. Our recent work revealed that the majority of the LPFC neurons show selectivity for behaviorally relevant motion direction and speed, suggesting its MT origins. We have also characterized the circuitry involved in assigning task relevance to such stimuli and examined memory-related signals its neurons carry. We record spiking activity and local field potentials and measure perceptual thresholds while monkeys compare various features of two sequential stimuli presented within and between different portions of the visual field.
Our current projects include the study of motion representation in the LPFC across space aimed at determining the local nature of the bottom-up signals arriving from MTs in both hemispheres. This information has important implications for the way LPFC neurons interpret sensory signals appearing in different portions of the visual field and for its top-down influences on the highly retinotopic and stimulus selective MT neurons. Another project is focused on the comparison of neural representation of motion and its location during memory guided discrimination tasks. We also study the behavior of neurons in area MT and their interactions with neurons in the LPFC during the same behavioral tasks. To determine the influence the LPFC on activity of MT neurons during all components of motion comparison tasks and its contribution to behavioral performance of these tasks we use selective reversible inactivation of regions in the LPFC shown to be active during such tasks. Our studies of the way LPFC represents and controls sensory signals used during memory-guided sensory tasks have important implications for elucidating the basis of cognitive dysfunction in mental disorders, long associated with deficits in sensory working memory and impaired prefrontal function.
Jannick Rolland : Optical system design and instrumentation for illumination optics, imaging science, and 3D visualization
Rolland's research interests center around optical system design and instrumentation for illumination optics, imaging science, and 3D visualization. Her current developments include state-of-the-art optical coherence tomography (OCT) systems, illumination devices, and head-worn displays (HWDs/HMDs). The research is expanding to leverage the emerging technology of freeform-optics. OCT is applied to tear-film measurements and keratoconus imaging; Illumination is applied to photodynamic therapy; HWDs may be used to support the investigation of brain functions. Recent works also included advances in image quality assessment as well as the development of a wavefront curvature sensor and associated wavefront reconstruction. She has over 90 peer reviewed publications and 18 patents.
Lizabeth Romanski : Functional organization of the primate frontal lobes
The integration of auditory and visual stimuli is crucial for recognizing objects by sight and sound, communicating effectively, and navigating through our complex world. While auditory and visual information are combined in many sites of the human brain, the combining of face and vocal information for effective communication has been shown to occur in specialized regions of the temporal and frontal lobes. Work in my laboratory is focused on how the ventral prefrontal cortex represents high level auditory information and the neuronal mechanisms which underlie integration of complex auditory and visual information, primarily face and vocal information during communication. Studies in our laboratory have shown that neurons within specific regions of the ventral prefrontal cortex are robustly responsive to complex sounds including species-specific vocalizations, while previous studies have shown that adjacent ventral prefrontal regions are selectively responsive to faces. We have shown that neurons within ventral prefrontal cortex are multisensory and respond to both faces and to the corresponding vocalizations. We are also interested in the factors that affect the integration of dynamic faces and vocalizations in the frontal lobe including temporal coincidence, stimulus congruence, as well as the emotional expression conveyed in the face-vocalization and the identity of the speaker. Further analysis of the neural mechanisms which support face and voice integration in non-human primates may help us to understand the mechanisms underlying social communication and social cognition.
Jesse Schallek : Imaging blood flow in the living eye
The neural cells that line the back of our eyes are sensitive to light and initiate our ability to see. These cells are among the most metabolically active tissues in the human body and are nourished by a dense network of capillaries that circulate blood to deliver nutrients and remove waste products from these hard-working cells. However, dysfunction of this neural-vascular system associates with a variety of retinal diseases and collectively gives rise to the leading cause of blindness in the developed world.
Our lab investigates blood flow in the living eye by using a specialized camera called an Adaptive Optics Scanning Light Ophthalmoscope (AOSLO) to correct for small imperfections of the optics of the eye. Once corrected, we can image the microscopic integrity of the smallest vessels that are ten-times thinner than a human hair. Additionally, capturing videos of this tissue enables study of the movement of single blood cells flowing within this network. We are developing and applying this cutting-edge technology to study blood flow in the retina in conditions of health and disease.
Marc H. Schieber : Neural control of hand and finger movements
Our lab investigates how the brain controls movements of the body, and translates our findings to advance brain-machine interface technology for restoration and repair of lost or damaged neurological function. A longstanding line of investigation explores control of fine finger movements, like those used in typing, playing a musical instrument, or performing delicate surgery. More recent work explores the combination of reaching, grasping, and manipulating. In both realms, we study how the brain controls a rather complex set of muscles to achieve the required movement.
Ruchira Singh : Cellular and molecular mechanisms of retinal and neurodegenerative diseases
Duje Tadin : Neural mechanisms of visual perception
The general goal of Tadin’s research is to investigate neural mechanisms of human visual perception, with a longstanding focus on the mechanisms of visual motion processing—a fundamental visual ability. Current topics also include perceptual learning, attention, visual adaptation, binocular rivalry and multi-sensory processing. Tadin’s approach is to seek converging experimental evidence from a variety of methodological approaches, including human psychophysics, brain stimulation (transcranial magnetic stimulation and direct current stimulation), computational modeling and collaborations involving primate neurophysiology and neuroimaging. Tadin also has extensive experience investigating visual perception in special populations, including aging, low-vision, cortical blindness, autism and schizophrenia.
David R. Williams : Limits of human vision
Williams uses psychophysical, anatomical, and imaging techniques to understand how the structure of the eye and brain affects visual performance. He has used laser interferometric methods to psychophysically measure the spacing and diameter of photoreceptors in the living human eye. Another project uses adaptive optics to obtain an improved measure of the optical quality of the eye. His laboratory has recently acquired images of the living human retina that resolve single cone photoreceptors for the first time. A related project has provided the first differential absorption images of the primate photoreceptor mosaic that can distinguish the three cone types responsible for human color vision. Students learn a wide range of methods including the design and analysis of optical systems, visual psychophysics, retinal imaging, image processing, and the mathematical analysis of spatial and temporal sampling.
Geunyoung Yoon : Supernormal vision
It has been known that the human eye suffers from higher order monochromatic aberrations as well as defocus and astigmatism. The development of technology to correct the eye's higher order aberrations raises the issue of how much vision improvement can be obtained. An adaptive optics (AO) system that measures and corrects the eye's aberrations provides supernormal vision and improves both the contrast sensitivity and visual acuity by correcting the higher order aberration over conventional correction methods. These results encourage the development of customized correction methods such as laser refractive surgery, contact lenses, and IOLs to achieve supernormal vision in everyday life. However, it is true that several factors such as photoreceptor sampling, biomechanical response of the cornea, and chromatic aberration reduce the benefit of supernormal vision that could be provided by customized correction methods.
James Zavislan : Optical system design for clinical diagnostics
Research areas include improving the development of optical imaging systems to non-invasively quantify the lipid layer of the ocular tear film. Overall, research thrust is to improve the performance of bio-medical optical imaging systems by optimizing the illumination and detection of objects of interest.