Scientific

Abstract – The distinction between stimulus chromaticity and perception of hue is critical for understanding color vision. A chromatic stimulus has spectral properties that characterize light entering the eye. The colors we experience, on the other hand, are perceptual constructs from neural processing within hierarchically organized cortical visual areas. Previous research, however, often has confounded stimulus chromaticity with perceptual color experience, leaving unsolved the fundamental question of whether the neural responses at each stage of processing represent a physical stimulus or instead a color we see. This question is addressed by dissociating the physical domain of chromatic stimulation from the perceptual domain of color experience, using a novel approach that causes sustained color percepts to vary over time without altering a rapidly changing temporal stream of retinal stimulation. fMRI measurements show a hierarchical progression of color processing in the ascending human ventral visual pathway, from a representation of the chromatic stimulus in V1 to perceptually experienced color in V4.   [METHODS: Stimulus chromaticity was dissociated from color appearance using dichoptically rivalrous chromaticities that were swapped between the eyes every 120 msec. The surprising percept is a single sustained color for about 2 seconds (during which there are 16 eye swaps) followed by a different sustained color (Christiansen, D’Antona & Shevell, J. Vision, 2017). In the fMRI experiments, observers reported their sustained color percept while BOLD responses were measured at each level of the visual cortical hierarchy. A chromatic representation was reconstructed from BOLD responses separately for each stage (V1, V2, V3, V4v, VO1) by transforming the fMRI measurements using an inverted encoding model (Brouwer & Heeger, J. Neurosci., 2009).]    https://imb.uchicago.edu/steve-shevell/

Abstract Braille literacy is decreasing despite braille being crucial for the social and economic opportunity, which are linked to higher rates of employment, higher education, financial stability, self-sufficiency, and self-esteem. The Philippines is one area in the world, which is particularly affected by braille illiteracy. Up to four percent of the people there are blind or visually impaired, compared to one percent in Canada. In a previous study by Lopez aimed to identify what visually impaired child-barriers encounter when using existing assistive technologies for learning to read, Lopez found that accessibility, portability, durability, and usability were key design criteria that directly related to user needs. We hypothesize that the design criteria captured by Lopez did not entirely encompass all criteria that could lead to the best device outcomes. The purpose of this research was to develop a comprehensive set of ideal design criteria for a device for braille literacy education in the Philippines, to implement these criteria in future design work.

Abstract Retinopathy of prematurity (ROP) emerged as a cause of blindness in children in industrialized countries during the late 1940s and 1950s with increased survival of preterm babies due to improvements in neonatal care including use of supplemental oxygen. During the 1950s, ROP was the single commonest cause of blindness in children in many industrialized countries (the “first epidemic”). Hyperoxia was proposed as an important risk factor which was largely supported by laboratory-research and clinical studies.  The use of oxygen was restricted in the mid-1950s which was followed by a reduction in the incidence of blindness from ROP, but higher rates of infant mortality and cerebral palsy.  Oxygen was used more liberally in the 1960s, and blindness from ROP began to re-emerge (the “second epidemic”). The introduction of increasingly sophisticated technology, including accurate methods of monitoring oxygen, and better management of neonatal and perinatal complications in prematurely born infants in the 1970s were probably the major factors responsible for reduction of blinding ROP observed during this period. In industrialized countries, blindness from ROP is now largely restricted to infants in the extremely low birth weight group. However, ROP has been described with increasing frequency in regions with rapidly developing neonatal care and this has been termed the “third epidemic.” The reasons for this epidemic are mixed: premature birth and low birth weight dominate in settings which are able to deliver high-quality neonatal care while exposure to other potentially modifiable risk factors, including oxygen, being important in neonatal units which have shortages of resources and so are unable to provide optimum standards of care.

Abstract Animals and humans with foveal vision exhibit vergence eye position-related changes in the response of their vestibulo-ocular reflex (VOR) consistent with geometrical expectations. For example, if one views a near target, the gain of the VOR is greater than if a far target is viewed. Modulation of VOR gain is seen in darkness, occurs at short latency, and is associated with neural activity within the vestibular nuclei. I will briefly review the geometry and then discuss the behavioral and neurophysiological evidence that supports vergence mediated vestibular responses. https://medicine.umich.edu/dept/khri/w-michael-king-phd