I am a postdoctoral scholar working with Dr. Jason Yeatman. With a background in optometry, vision science, psychophysics and cognitive neuroscience my long-term goal is to study the intersection of basic visual mechanisms and various neurodevelopmental disorders and to extend this understanding in creating effective early screening tools, and in advancing evidence-based therapeutic and remediation programs. Inherent to this interest is the need for developmental data in large and demographically diverse populations. I strongly believe that such inclusive research not only contributes to scientific advancements but can go beyond to bridge health and education disparities. I joined the Brain Development and Education lab at Stanford after taking a medical break. During my break, I had the opportunity to run a vision screening camp for a school for differently abled children. Many children with a learning disability are misunderstood to have a vision problem making optometrist the first people to diagnose the disability but intervention stops at that point. This kindled my curiosity and I soon discovered the lack of converging understanding on the role of visual processing in dyslexia that in turn limits the possibility of evidence-based intervention. I was deeply interested in understanding the role of vision and attention in dyslexia. Over the past three years, I developed visual measures based on the most cited hypothesis in the dyslexia literature. These measures were designed such that they inform us about the hypothesized construct in an ecologically relevant paradigm for reading. I developed a validation scheme where measures are first deployed on the adult population and various behavioral and eye tracking aspects of the measure are characterized. The measures are built on a browser-based platform (using PsychoPy© and jsPsych©) where they are validated against the laboratory-based measurements. All the web-based visual measures have timing parameters optimized to ensure measurement validity. Over the past year, I have focused on optimizing these visual measures to make them adaptive, short, and reliable for kindergarten and first grade children. My goal in the current project is to leverage this battery of visual measures to understand how visual deficits are linked to the development of reading disorders. The web-based assessments are designed to be deployed to a large and diverse population of unprecedented scale.
Honors & Awards
Postdoctoral award, MCHRI (2021)
Doctor of Philosophy, University of Massachusetts Boston (2018)
Master of Science, University of Waterloo (2011)
Bachelor of Science, Birla Institute of Technology and Science (2008)
Jason Yeatman, Postdoctoral Faculty Sponsor
Community and International Work
Association for India's development
Marginalized communities in India
Opportunities for Student Involvement
Children with dyslexia show no deficit in exogenous spatial attention but show differences in visual encoding.
In the search for mechanisms that contribute to dyslexia, the term "attention" has been invoked to explain performance in a variety of tasks, creating confusion since all tasks do, indeed, demand "attention." Many studies lack an experimental manipulation of attention that would be necessary to determine its influence on task performance. Nonetheless, an emerging view is that children with dyslexia have an impairment in the exogenous (automatic/reflexive) orienting of spatial attention. Here we investigated the link between exogenous attention and reading ability by presenting exogenous spatial cues in the multi-letter processing task-a task relevant for reading. The task was gamified and administered online to a large sample of children (N = 187) between 6 and 17 years. Children with dyslexia performed worse overall at rapidly recognizing and reporting strings of letters. However, we found no evidence for a difference in the utilization of exogenous spatial cues, resolving two decades of ambiguity in the field. Previous studies that claimed otherwise may have failed to distinguish attention effects from overall task performance or found spurious group differences in small samples. RESEARCH HIGHLIGHTS: We manipulated exogenous visual spatial attention using pre-cues in a task that is relevant for reading and we see robust task effects of exogenous attention. We found no evidence for a deficit in utilizing exogenous spatial pre-cues in children with dyslexia. However, children with dyslexia showed reduced recognition ability for all letter positions. Children with dyslexia were just as likely to make letter transposition errors as typical readers.
View details for DOI 10.1111/desc.13458
View details for PubMedID 37985400
Spatial attention in encoding letter combinations.
1800; 11 (1): 24179
Reading requires the correct identification of letters and letter positions within words. Selective attention is, therefore, required to select chunks of the text for sequential processing. Despite the extensive literature on visual attention, the well-known effects of spatial cues in simple perceptual tasks cannot inform us about the role of attention in a task as complex as reading. Here, we systematically manipulate spatial attention in a multi-letter processing task to understand the effects of spatial cues on letter encoding in typical adults. Overall, endogenous (voluntary) cue benefits were larger than exogenous (reflexive). We show that cue benefits are greater in the left than in the right visual field and larger for the most crowded letter positions. Endogenous valid cues reduced errors due to confusing letter positions more than misidentifications, specifically for the most crowded letter positions. Therefore, shifting endogenous attention along a line of text is likely an important mechanism to alleviate the effects of crowding on encoding letters within words. Our results help set the premise for constructing theories about how specific mechanisms of attention support reading development in children. Understanding the link between reading development and attention mechanisms has far-reaching implications for effectively addressing the needs of children with reading disabilities.
View details for DOI 10.1038/s41598-021-03558-4
View details for PubMedID 34921202
Rapid online assessment of reading ability.
2021; 11 (1): 6396
An accurate model of the factors that contribute to individual differences in reading ability depends on data collection in large, diverse and representative samples of research participants. However, that is rarely feasible due to the constraints imposed by standardized measures of reading ability which require test administration by trained clinicians or researchers. Here we explore whether a simple, two-alternative forced choice, time limited lexical decision task (LDT), self-delivered through the web-browser, can serve as an accurate and reliable measure of reading ability. We found that performance on the LDT is highly correlated with scores on standardized measures of reading ability such as the Woodcock-Johnson Letter Word Identification test (r=0.91, disattenuated r=0.94). Importantly, the LDT reading ability measure is highly reliable (r=0.97). After optimizing the list of words and pseudowords based on item response theory, we found that a short experiment with 76 trials (2-3min) provides a reliable (r=0.95) measure of reading ability. Thus, the self-administered, Rapid Online Assessment of Reading ability (ROAR) developed here overcomes the constraints of resource-intensive, in-person reading assessment, and provides an efficient and automated tool for effective online research into the mechanisms of reading (dis)ability.
View details for DOI 10.1038/s41598-021-85907-x
View details for PubMedID 33737729
The ups and downs of sensory eye balance: Monocular deprivation has a biphasic effect on interocular dominance.
2021; 183: 53–60
Classic studies of ocular dominance plasticity in early development showed that monocular deprivation suppresses the neural representation and visual function of the deprived eye. However, recent studies have shown that a short period of monocular deprivation (<3 h) in normal adult humans, shifts sensory eye dominance in favor of the deprived eye. How can these opposing effects be reconciled? Here we argue that there are two systems acting in opposition at different time scales. A fast acting, stabilizing, homeostatic system that rapidly decreases gain in the non-deprived eye or increases gain in the deprived eye, and a relatively sluggish system that shifts balance toward the non-deprived eye, in an effort to reduce input of little utility to active vision. If true, then continuous deprivation should produce a biphasic effect on interocular balance, first shifting balance away from the non-deprived eye, then towards it. Here we investigated the time course of the deprivation effect by monocularly depriving typical adults for 10 h and conducting tests of sensory eye balance at six intervening time points. Consistent with previous short-term deprivation work, we found shifts in sensory eye dominance away from the non-deprived eye up until approximately 5 h. We then observed a turning point, with balance shifting back towards the non-deprived eye, -, a biphasic effect. We argue that this turning point marks where the rapid homeostatic response saturates and is overtaken by the slower system responsible for suppressing monocular input of limited utility.
View details for DOI 10.1016/j.visres.2021.01.010
View details for PubMedID 33684826
Assessing the kaleidoscope of monocular deprivation effects
JOURNAL OF VISION
2018; 18 (13): 14
Short-term monocular deprivation (∼150 min) temporarily shifts sensory eye balance in favor of the deprived eye (Lunghi, Burr, & Morrone, 2011; Zhou, Clavagnier, & Hess, 2013), opposite to classic deprivation studies (Hubel & Wiesel, 1970). Various types of deprivation-light-tight, diffuser lenses, image degradation-have been tested, and it seemed that a deprivation of contrast was necessary, and sufficient, for these shifts. This could be accommodated in a feedforward model of binocular combination (Meese, Georgeson, & Baker, 2006; Sperling & Ding, 2010), in which the shift reflects a (persistent) reweighting induced by an interocular gain control mechanism tasked with maintaining binocular balance (Zhou, Clavagnier, et al., 2013). Here, we used a novel "kaleidoscopic" monocular deprivation that, although it rendered images fractionated and uninformative, preserved gross luminance, color, spatial frequency, motion, and contrast information, effectively sneaking the image degradation past early, feedforward mechanisms, targeting higher levels. Kaleidoscopic deprivation produced effects indistinguishable from traditional light-tight patching. This rules out contrast imbalance as the sole factor driving these shifts in sensory eye balance. In addition, since the suppression of the kaleidoscopic image likely requires feedback from higher-level processes capable of determining the behavioral relevance of an eye's information (Foley & Miyanshi, 1969; Jiang, Costello, & He, 2007; Kovács, Papathomas, Yang, & Fehér, 1996; Wolf & Hochstein, 2011), feedforward-only models may need to be elaborated.
View details for DOI 10.1167/18.13.14
View details for Web of Science ID 000454710400014
View details for PubMedID 30572342
New rules for visual selection: Isolating procedural attention
JOURNAL OF VISION
2017; 17 (2): 18
High performance in well-practiced, everyday tasks-driving, sports, gaming-suggests a kind of procedural attention that can allocate processing resources to behaviorally relevant information in an unsupervised manner. Here we show that training can lead to a new, automatic attentional selection rule that operates in the absence of bottom-up, salience-driven triggers and willful top-down selection. Taking advantage of the fact that attention modulates motion aftereffects, observers were presented with a bivectorial display with overlapping, iso-salient red and green dot fields moving to the right and left, respectively, while distracted by a demanding auditory two-back memory task. Before training, since the motion vectors canceled each other out, no net motion aftereffect (MAE) was found. However, after 3 days (0.5 hr/day) of training, during which observers practiced selectively attending to the red, rightward field, a significant net MAE was observed-even when top-down selection was again distracted. Further experiments showed that these results were not due to perceptual learning, and that the new rule targeted the motion, and not the color of the target dot field, and global, not local, motion signals; thus, the new rule was: "select the rightward field." This study builds on recent work on selection history-driven and reward-driven biases, but uses a novel paradigm where the allocation of visual processing resources are measured passively, offline, and when the observer's ability to execute top-down selection is defeated.
View details for DOI 10.1167/17.2.18
View details for Web of Science ID 000397220000018
View details for PubMedID 28245497
Light and Sight
Light and Its Many Wonders, National Academy of Sciences
Viva Books, India,. 2015: 368-380
View details for DOI HIGP-2179
- Color shifts at different viewing eccentricities on flat-panel rear projection displays in steps of perceptibility threshold units JOURNAL OF MODERN OPTICS 2013; 60 (14): 1151-1158