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Open Access Publications from the University of California

Scholarly Works (41 results)

  • Article
  • Peer Reviewed
UC Berkeley Previously Published Works (2016)
Biological sensory systems share a number of organizing principles. One such principle is the formation of parallel streams. In the visual system, information about bright and dark features is largely conveyed via two separate streams: theONandOFFpathways. While brightness and darkness can be considered symmetric and opposite forms of visual contrast, the response properties of cells in theONandOFFpathways are decidedly asymmetric. Here, we ask whether a simple contrast-encoding model predicts asymmetries for brights and darks that are similar to the asymmetries found in theONandOFFpathways. Importantly, this model does not include any explicit differences in how the visual system represents brights and darks, but it does include a common normalization mechanism. The phenomena captured by the model include (1) nonlinear contrast response functions, (2) greater nonlinearities in the responses to darks, and (3) larger responses to dark contrasts. We report a direct, quantitative comparison between these model predictions and previously published electrophysiological measurements from the retina and thalamus (guinea pig and cat, respectively). This work suggests that the simple computation of visual contrast may account for a range of early visual processing nonlinearities. Assessing explicit models of sensory representations is essential for understanding which features of neuronal activity these models can and cannot predict, and for investigating how early computations may reverberate through the sensory pathways.
    Cover page: A normalized contrast‐encoding model exhibits bright/dark asymmetries similar to early visual neurons
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2016)
    Understanding the current status and historical trends of gender representation within a research field is an important component of fostering a diverse and inclusive scientific community. Here, we report on the gender representation of a large sample of the vision science research community--the attendees of the Annual Meeting of the Vision Sciences Society (VSS). Our analysis shows that the majority of scientists at all career levels in our sample are male. This imbalance is most pronounced for the senior scientists, whereas predoctoral students are nearly balanced between the genders. Historically, the gender imbalance was larger than it is at present, and it has followed a slow-but-steady trend toward gender parity over the past decade. A longitudinal analysis based on tracking individual attendees shows a larger dropout rate for female than male predoctoral trainees. However, among the trainees who continue in the vision science field after graduate school, evidence suggests that career advancement is quite similar between the genders. In an additional analysis, we found that the VSS Young Investigator awardees and the abstract review committee members reflect substantial gender imbalances, suggesting that these recognitions have yet to catch up with the greater gender balance of the rising generation of junior vision scientists. We hope that this report will encourage awareness of issues of diversity in the scientific community and further promote the development of a research field in which all talented scientists are supported to succeed.
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2021)
      Dichoptic tone mapping methods aim to leverage stereoscopic displays to increase visual detail and contrast in images and videos. These methods, which have been called both binocular tone mapping and dichoptic contrast enhancement, selectively emphasize contrast differently in the two eyes' views. The visual system integrates these contrast differences into a unified percept, which is theorized to contain more contrast overall than each eye's view on its own. As stereoscopic displays become increasingly common for augmented and virtual reality (AR/VR), dichoptic tone mapping is an appealing technique for imaging pipelines. We sought to examine whether a standard photographic technique, exposure bracketing, could be modified to enhance contrast similarly to dichoptic tone mapping. While assessing the efficacy of this technique with user studies, we also re-evaluated existing dichoptic tone mapping methods. Across several user studies; however, we did not find evidence that either dichoptic tone mapping or dichoptic exposures consistently increased subjective image preferences. We also did not observe improvements in subjective or objective measures of detail visibility. We did find evidence that dichoptic methods enhanced subjective 3D impressions. Here, we present these results and evaluate the potential contributions and current limitations of dichoptic methods for applications in stereoscopic displays.
        Creative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2016)
        We conducted an online survey using a set of factual science questions that are commonly administered to assess fact-based scientific literacy. We report that the online population performed substantially better on this standard assessment than the traditional survey population. For example, it has been widely reported that 1 in 4 Americans does not know that the Earth revolves around the Sun, whereas among the online population, this ratio is reduced to 1 in 25. While new online platforms provide researchers with unprecedented ease of access to a large sample population for studying trends in public knowledge and attitudes, generalizing from online population samples to the US population at large poses a considerable challenge. We discuss the potential reasons for this discrepancy and the implications for conducting research online.
          Cover page: Does the Sun revolve around the Earth? A comparison between the general public and online survey respondents in basic scientific knowledge
          • Thesis
          • Peer Reviewed
          UC Berkeley Electronic Theses and Dissertations (2024)

          Many people have had the experience of viewing the world through optics, such as when wearing corrective spectacles or using augmented and virtual reality devices (AR/VR). The purpose of the optical lenses present in spectacles and devices is to bring images into focus, but they also produce unwanted distortions such as magnification and minification that change the retinal image size or shape of an object. Surprisingly, small changes in retinal image size or shape can have substantial perceptual and physical consequences. While spectacles have been around for centuries, there remains a large gap in the literature on how optical distortions affect the viewer. This dissertation contains experimental investigations related to how optical distortions affect perception and comfort, and how these effects change over time. Chapter 1 establishes a fundamental understanding of the onset of perceptual and physical symptoms produced by optical minification. Chapter 2 investigates how people adapt over time to a specific type of monocular distortion that alters depth and shape perception. Chapter 3 investigates how the visual system interprets the geometry of objects when faced with perceptual disruptions caused by optical distortions. Together this research provides a much-needed foundational understanding of optical distortions from multiple domains.

            Cover page: Distortions in Wearable Optics: Comfort, Perception, and Adaptation
            • Thesis
            • Peer Reviewed
            UC Berkeley Electronic Theses and Dissertations (2023)

            Due to the lateral separation of our eyes, the human visual system takes in two slightly different views of the world. These two views must be combined by the visual system into a single percept. Importantly, binocular combination can be challenged when the left and right eye views differ from each other, for example, in luminance, contrast or color. Failures of binocular combination can result in double vision, losses in-depth perception, and troublesome visual appearances like binocular rivalry. With advances in wearable binocular display technologies for virtual and augmented reality, the subjective appearances associated with artificial binocular differences introduced by these displays warrant in depth evaluation. This dissertation contains a body of work characterizing the subjective appearance of images in which different contrasts are presented to the two eyes. The work herein builds on seminal studies in vision science that paved the way for our understanding of binocular appearance, but primarily studied simplistic visual stimuli such as grating patterns that differ substantially from the structured and complex visual inputs that our visual system evolved for. In Chapter 1, I extend on prior work and examine percepts associated with a range of stimulus patterns with various degrees of complexity to deepen our understanding of binocular combination. In the remaining chapters, I leverage these insights to examine the implications of binocular appearance for three key applications in computer graphics and binocular display design: display imperfections, tonemapping, and field of view coverage. Wearable display technologies will advance the way that we interact with digital content and with the world at large, but their utility and impact are contingent on whether or not they can integrate well with our natural vision. Thus, in each chapter I discuss design guidelines based on the perceptual results to aid the development of better binocular displays that prevents undesirable visual artifacts, and exploit binocular vision to loosen technical specifications.

              • Article
              • Peer Reviewed
              UC Berkeley Previously Published Works (2014)
              Sighted animals must survive in an environment that is diverse yet highly structured. Neural-coding models predict that the visual system should allocate its computational resources to exploit regularities in the environment, and that this allocation should facilitate perceptual judgments. Here we use three approaches (natural scenes statistical analysis, a reanalysis of single-unit data from alert behaving macaque, and a behavioral experiment in humans) to address the question of how the visual system maximizes behavioral success by taking advantage of low-level regularities in the environment. An analysis of natural scene statistics reveals that the probability distributions for light increments and decrements are biased in a way that could be exploited by the visual system to estimate depth from relative luminance. A reanalysis of neurophysiology data from Samonds et al. (2012) shows that the previously reported joint tuning of V1 cells for relative luminance and binocular disparity is well matched to a predicted distribution of binocular disparities produced by natural scenes. Finally, we show that a percept of added depth can be elicited in images by exaggerating the correlation between luminance and depth. Together, the results from these three approaches provide further evidence that the visual system allocates its processing resources in a way that is driven by the statistics of the natural environment.
                Cover page: Perceived Depth in Natural Images Reflects Encoding of Low-Level Luminance Statistics
                • Article
                • Peer Reviewed
                UC Berkeley Previously Published Works (2018)
                  Cover page: Perceived Facial Distortions in Selfies Are Explained by Viewing Habits.
                  • Article
                  • Peer Reviewed
                  UC Berkeley Previously Published Works (2016)
                  Research in neuroscience has great potential for transforming education. However, the brain systems that support academic and cognitive skills are poorly understood in comparison to the systems that support sensory processing. Decades of basic research have examined the role that brain plasticity plays in the genesis and treatment of developmental visual disorders, which may help to inform how cognitive training approaches can be tailored for students who experience environmental disadvantage. In this review, we draw parallels between visual and cognitive intervention approaches, and suggest research avenues that could inform educational practice in the future.
                    Cover page: Sensory and cognitive plasticity: implications for academic interventions
                    • Article
                    • Peer Reviewed
                    UC Berkeley Previously Published Works (2015)
                    The nervous system has evolved in an environment with structure and predictability. One of the ubiquitous principles of sensory systems is the creation of circuits that capitalize on this predictability. Previous work has identified predictable non-uniformities in the distributions of basic visual features in natural images that are relevant to the encoding tasks of the visual system. Here, we report that the well-established statistical distributions of visual features--such as visual contrast, spatial scale, and depth--differ between bright and dark image components. Following this analysis, we go on to trace how these differences in natural images translate into different patterns of cortical input that arise from the separate bright (ON) and dark (OFF) pathways originating in the retina. We use models of these early visual pathways to transform natural images into statistical patterns of cortical input. The models include the receptive fields and non-linear response properties of the magnocellular (M) and parvocellular (P) pathways, with their ON and OFF pathway divisions. The results indicate that there are regularities in visual cortical input beyond those that have previously been appreciated from the direct analysis of natural images. In particular, several dark/bright asymmetries provide a potential account for recently discovered asymmetries in how the brain processes visual features, such as violations of classic energy-type models. On the basis of our analysis, we expect that the dark/bright dichotomy in natural images plays a key role in the generation of both cortical and perceptual asymmetries.
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