NeuroLecture Speaker Series
Impact of Distorted Optics on Spatial and Depth Vision - Lessons from Human Disease Models
Shrikant Bharadwaj, LV Prasad Eye Institute (Optometry and Vision Sciences)
May 6 • 12:30 pm • Reynolds School of Journalism 101
The process of "seeing" involves the capture of light photons by the anatomical substrate called "eye" and processing these photons using a black box called "brain". The output of this black box manifests itself as perception including form, depth, motion and color and as motor actions including eye movements of various sorts. As vision scientists, our goal is to understand the functioning of the black box by systematically studying perception and motor action in response to known experimental manipulations. As clinicians, we use the output of the black box as a measure of how well the individual is seeing and interacting with the world around them. Given that the "eye" forms the substrate for perception by the "brain", it is conceivable that properties of the "eye" - optics, in this case - will have a significant impact on the quality of perception. The clinic presents several interesting scenarios where the optics of the eye are distorted but their impact on perception is not systematically understood thus far. In my talk, I will use two examples to illustrate this issue. In both cases, the eye is heavily distorted and there may also be significant interocular difference in distortions depending on disease presentation. What impact do these distortions have on spatial and depth perception and how does modifying the optics using rigid contact lenses impact perception will be the focus of my presentation.
Scotopic Vision and Aging
Megan Tillman, UC Davis (Neuroscience)
May 4 • 3:00 pm • Reynolds School of Journalism 101
Poor night vision is a common complaint amongst the elderly, however, the cause of this impairment is not straightforward. Many factors are thought to contribute to the age-related decline in scotopic sensitivity, including reduced pupil size, increased optical density of the ocular media, rod photoreceptor death, and delayed photopigment kinetics. The goal of the current research was to measure the retinal activity of normal younger and older adults using the electroretinogram (ERG) and control for optical changes (i.e., pupil size and ocular media density) so as to determine a neural contribution for the age-related scotopic vision loss. Both full-field and multifocal ERGs were recorded in order to understand the global and topographical changes, respectively, in the rod-mediated retina of older adults.
Synchonization of Circadian Clocks to Daily Environmental Cycles
Patrick Emery, University of Massachusetts Medical School (Neurobiology)
April 21 • 4:00 pm • Davidson Math & Science 105
Circadian clocks play the critical role of optimizing most bodily functions - from basic metabolism to complex behaviors - with the time of day. These timekeepers need to be synchronized with the environment to be helpful. Therefore, they are able to respond to multiple inputs, such as light and temperature. Interestingly, in Drosophila, these two environmental cues can be detected in a cell-autonomous manner. The seminar will focus on these cell-autonomous photic and thermal sensing mechanisms, and how they converge on a single pacemaker protein, TIMELESS, to entrain together circadian clocks.
Roles of Cortical Single- and Double-Opponent Cells in Color Vision
Robert Shapley, New York University (Center for Neural Science)
April 15 • 3:00 pm • William J. Raggio Building 2030
Color and form interact in visual perception. We will consider the neural mechanisms in the visual cortex that are the basis for color-form interactions.
Pulse Trains to Percepts: The Challenge of Creating a Perceptually Intelligible World with Sight Recovery Techniques
Ione Fine, University of Washington (Psychology)
April 8 • 11:30 am • Reynolds School of Journalism 101
An extraordinary variety of sight recovery therapies are either about to begin clinical trials, have begun clinical trials, or are currently being implanted in patients. However, as yet we have little insight into the perceptual experience likely to be produced by these implants. This review focuses on methodologies, such as optogenetics, small molecule photoswitches and electrical prostheses, which use artificial stimulation of the retina to elicit percepts. For each of these technologies, the interplay between the stimulating technology and the underlying neurophysiology is likely to result in distortions of the perceptual experience. Here, we simulate some of these potential distortions and discuss how they might be minimized either through changes in the encoding model or through cortical plasticity.
Color Vision in the Peripheral Retina
Vicki Volbrecht, Colorado State University (Psychology)
April 1 • 3:00 pm • William J. Raggio Building 2030
The study of peripheral color vision presents challenges due to the presence of both rods and cones in the peripheral retina. As many studies have shown, color perception in the peripheral retina differs from color perception in the fovea; and color perception also varies across the peripheral retina with retinal eccentricity and location. These differences are not surprising due to differences in the retinal mosaic with retinal eccentricity and location. Despite these differences, though, when viewing objects in everyday life that cover both the foveal and peripheral retina, we perceive a uniform color percept. Similarly, when an object is viewed binocularly along the horizontal meridian in the peripheral retina, the color percept is uniform even though the object falls on the temporal retina of one eye and the nasal retina of the other eye; viewed monocularly, the color of the object may differ if it falls on the temporal or nasal retina. Recently, our laboratory has been investigating some of these issues as it relates to peripheral color vision and uniform color percepts across the differing retinal mosaic.
Transcriptional Regulation of Heart Development and Chromatin Structure
Benoit Bruneau, UCSF (Gladstone Institute of Cardiovascular Disease)
March 10 • 4:00 pm • William J. Raggio Building 3005
Complex networks of transcription factors regulate cardiac cell fate and morphogenesis, and dominant mutations in transcription factor genes lead to most instances of inherited congenital heart defects (CHDs). The mechanisms underlying CHDs that result from these mutations is not known, but regulation of gene expression within a relatively narrow developmental window is clearly essential for normal cardiac morphogenesis. We have detailed the interactions between CHD-associated transcription factors, their interdependence in regulating cardiac gene expression and morphogenesis, and their function in establishing early cardiac lineage boundaries that are disrupted in CHD. We have also delineated an essential role by CTCF in regulating genome-wide three-dimensional chromatin organization.
Health Law Implications of Advances in Neuroscience, Including Neuroimaging
Stacey Tovino, University of Nevada, Las Vegas (William S. Boyd School of Law)
March 4 • 3:00 pm • Mathewson-IGT Knowledge Center 124
Within the overlapping fields of neurolaw and neuroethics, scholars have given significant attention to the implications of advances in neuroscience for issues in criminal law, criminal procedure, constitutional law, law and religion, tort law, evidence law, confidentiality and privacy law, protection of human subjects, and even the regulation of neuroscience-based technologies. Less attention has been paid, however, to the implications of advances in neuroscience for more traditional civil and regulatory health law issues. In this presentation, I will examine the ways in which neuroscience impacts four different areas within civil and regulatory health law, including mental health parity law and mandatory mental health and substance use disorder law, public and private disability benefit law, disability discrimination law, and professional discipline. In some areas, especially mental health parity law and mandatory mental health and substance use disorder benefit law, advances in neuroscience have positively impacted health insurance coverage. In other areas, including disability discrimination law, the impact has not been as significant.
Perceptual Resolution of Color with Ambiguous Chromatic Neural Representations
Steven Shevell, University of Chicago (Psychology)
Feb 26 • 11:30 am • Reynolds School of Journalism 101
Our ability to see in the natural world depends on the neural representations of objects. Signals sent from the eye to the brain are the basis for what we see, but these signals must be transformed from the image-based representation of light in the eye to an object-based representation of edges and surfaces. A challenge for understanding this transformation is the ambiguous nature of the image-based representation from the eye. Textbooks examples demonstrate this ambiguity using a constant retinal image that causes fluctuation between two different bi-stable percepts (as in the face-or-vase illusion, or a Necker cube that switches between two orientations). Bi-stable colors also can be experienced with ambiguous chromatic neural representations. Recent experiments (1) generate ambiguous chromatic neural representations that result in perceptual bi-stability alternating between two colors, (2) reveal that two or more distinct objects in view, each with its own ambiguous chromatic representation, often have the same color, which reveals that grouping is a key aspect of resolving chromatic ambiguity, and (3) show that grouping survives even with unequal temporal properties among the separate ambiguous representations, as predicted by a model of binocularly integrated visual competition.
Understanding Person Recognition; Psychological, Computational, & Neural Perspectives
Alice O'Toole, University of Texas at Dallas (School of Behavioral and Brain Sciences)
Feb 19 • 11:30 am • Reynolds School of Journalism 101
Over the past decade, face recognition algorithms have shown impressive gains in performance, operating under increasingly unconstrained imaging conditions. It is now commonplace to benchmark the performance of face recognition algorithms against humans and to find conditions under which the machines perform more accurately than humans. I will present a synopsis of human-machine comparisons that we have conducted over the past decade, in conjunction with U.S. Government-sponsored competitions for computer-based face recognition systems. From these comparisons, we have learned much about human face recognition, and even more about person recognition. These experiments have led us to examine the neural responses in face- and body-selective cortical areas during person recognition in natural viewing conditions. I will describe the neuroimaging findings and conclude that human expertise for "face recognition" is better understood in the context of the whole person in motion-where the body and gait provide valuable identity information that supplements the face in poor viewing conditions.
Color Naming, Color Communication and the Evolution of Basic Color Terms
Delwin Lindsey, Ohio State University (Psychology)
Feb 19 • 12:30 pm • Reynolds School of Journalism 101
The study of the language of color is implicitly based on the existence of a shared mental representation of color within a culture. Berlin & Kay (1969) proposed that the great cross-cultural diversity in color naming occurs because different languages are at different stages along a constrained trajectory of color term evolution. However, most pre-industrial societies show striking individual differences in color naming (Lindsey & Brown, 2006, 2009). We argue that within-language diversity is not entirely lexical noise. Rather, it suggests a fundamental mechanism for color lexicon change. First, the diverse color categories---including some that do not conform to classical universal categories---observed within one society are often similar to those seen in people living in distant societies, on different continents, and speaking completely unrelated languages. Second, within-culture consensus is often low, either due to synonymy or to variation in the number and/or structure of color categories. Next, we introduce an information-theoretic analysis based on mutual information, and analyze within-culture communication efficiency across cultures. Color communication in Hadzane, Somali, and English provides insight into the structure of the lexical signals and noise in world languages (Lindsey et al., 2015). These three lines of evidence suggest a new view of color term evolution. We argue that modern lexicons evolved, under the guidance of universal perceptual constraints, from initially sparse (Levinson, 2000), distributed representations that mediate color communication poorly, to more complete representations, with high consensus color naming systems capable of mediating better color communication within the language community.
Critical Immaturities Limiting Infant Visual Sensitivity
Angela Brown, Ohio State University (Optometry)
Feb 19 • 1:00 pm • Reynolds School of Journalism 101
The vision of the human infant is remarkably immature: visual sensitivity to light is low, contrast sensitivity is poor, visual acuity is poor, color vision is poor, vernier acuity is poor, and stereopsis is probably not possible until the infant is several months old. The visual system of the human infant is known to be biologically immature as well: the photoreceptors, especially the foveal cones, are morphologically immature, and myelination of the ascending visual pathway is not complete at birth. Also, the infant is cognitively immature, for example the infant attention span is short. In this talk, I will unite these immaturities into a single picture of the infant visual system: the main critical immaturity that limits infant visual performance on these psychophysical tasks is a large amount of contrast-like noise that is added linearly to the visual signal, after the sites of visual light adaptation, but before the sites of visual contrast adaptation, and likely in the retina or ascending visual pathway.