Examining the Tools Used to Infer Models of Lexical Activation: Eye-tracking, Mouse-tracking, and Reaction Time

Most models of auditory word recognition describe the activation of lexical items in a continuous and graded manner. Much evidence in favor of these models comes from the visual-world paradigm, using either eye fixations or computer cursor trajectories as dependent measures. In particular, Spivey, Grosjean and Knoblich (2005) relied on their observation of unimodality in the distribution of cursor trajectories to argue in favor of a single cognitive process consistent with a continuous model of lexical activation. The present study addresses two questions: (1) whether the logic of inferring the number of cognitive processes from distributional analyses can be extended to a different dependent variable – reaction times, and (2) how robust the distribution of cursor trajectories is to changes in cursor speed (mouse gain). In Experiment 1, eye movements and reaction times were recorded in a visual-world paradigm and reaction times were modeled using ex-Gaussian curve-fitting. Participants responded slower to trials with a phonological competitor presented alongside the target than to trials with a control image presented alongside the target. Crucially, this difference was manifested as a shifting of the distribution rather than as a skewing of the distribution and lends additional support for a continuous model of lexical activation. Experiment 2 measured eye and mouse movements concurrently in a similar visual-world task to investigate the relationship between these two dependent measures at the level of the individual trial. In addition, Experiment 2 manipulated the speed of the cursor (mouse gain) between subjects. The low mouse gain served to reduce the effect of phonological competition. Moreover, the shape of the distribution of cursor trajectories across phonological competitor and control conditions was indistinct with low mouse gain, while the shape of the distributions across the two conditions differed with high mouse gain. This effect of mouse gain shows that the distribution of cursor trajectories is not robust to changes in mouse gain. Moreover, it raises questions about the strength of the linking hypothesis necessary to interpret the distribution of cursor trajectories

Multi-sensory Design for people with visual impairments

Architectural design commonly focuses on the visual qualities of its manifestation, leaving people with visual impairments aside from its qualitative goals. In order to counteract this phenomenon and appropriately address people with low visual acuity / legal blindness, we must understand the people within this large community as well as current policies focusing on different types of accommodations for spatial practicality. Understanding the people will entail a dive into what a visual impairment is, what it is like, and understanding how people perceive the world as a whole. Then it is necessary to understand current policies that designers have adopted in order to benefit those with physical disabilities by making all space accessible to all people. After establishing an understanding of the current state of the issue we can move forward by breaking down a set of guiding principle that is based on sensory cues. This will lead to an understanding of how to make architecture a multi-sensory experience for everyone while specifically benefiting those with visual impairments

The Timing of Reward-Seeking Action Tracks Visually-Cued Theta Oscillations in Primary Visual Cortex

An emerging body of work challenges the view that primary visual cortex (V1) represents the visual world faithfully. Theta oscillations in the local field potential (LFP) of V1 have been found to convey temporal expectations and, specifically, to express the delay between a visual stimulus and the reward that it portends. We extend this work by showing how these oscillatory states in male, wild-type rats can even relate to the timing of a visually cued reward-seeking behavior. In particular, we show that, with training, high precision and accuracy in behavioral timing tracks the power of these oscillations and the time of action execution covaries with their duration. These LFP oscillations are also intimately related to spiking responses at the single-unit level, which themselves carry predictive timing information. Together, these observations extend our understanding of the role of cortical oscillations in timing generally and the role of V1 in the timing of visually cued behaviors specifically.Fil: Levy, Joshua M.. University Johns Hopkins; Estados UnidosFil: Zold, Camila Lidia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; ArgentinaFil: Namboodiri, Vijay Mohan K.. University of North Carolina; Estados UnidosFil: Hussain Shuler, Marshall G. University Johns Hopkins; Estados Unido

Utilization of Low Altitude Remote Sensing Techniques for Coral Bleaching Assessments

M.S. University of Hawaii at Manoa 2016.Includes bibliographical references.The utilization of small-unmanned aerial systems (sUAS) as a cheap, effective complement to other assessment tools is imminent in the field of coral reef ecology. Here, we describe the current status of sUAS in the field of coastal monitoring, and introduce the utilization of low-altitude sUAS assessments for coral reef research using proof-of-concept results and completed work describing the distribution of coral bleaching across several patch reefs in Kāneʻohe Bay, Hawaii. Overlapping sub- centimeter reef imagery collected during the 2015 coral bleaching event was used to construct complete high-resolution reef images of four Kāneʻohe Bay patch reefs located in “long residence time” and “short residence time” flow regimes. The spatial distributions of bleached and paled corals were assessed in relation to coastal stressors (sedimentation rates, salinity and phosphate concentrations). Results support the notion that phosphate, an important inorganic nutrient, differed significantly between “closer to shore” and “further from shore” reefs instead of between previously determined flow regimes. Mean phosphate concentrations and salinities were both significantly correlated to unhealthy (bleached or paled) coral cover. When assessing the environmental conditions in close temporal proximity to image collection, only salinity had a strong negative correlation with the cover of unhealthy coral. Paled, bleached, and healthy coral on all four reefs were significantly clumped spatially, although bleached corals had the largest mean distances between affected colonies. This project provides valuable insight into the relationships between Kāneʻohe Bay patch reefs and coastal stressors at previously unexplored spatial scales, and demonstrates the effective use of sUAS surveys in the field of coral reef science

Visually-guided timing and its neural representation

Stimulus-driven timing is a fundamental aspect of human and animal behavior. This type of timing can be subdivided into three principal axes: interval generation, storage, and evaluation. In this thesis, we present results related to each of these axes and describe their implications for how we understand timed behavior. In Chapter 2, we address interval generation, which is the process of creating an internal representation of an ongoing temporal interval. While several studies have found evidence for neural oscillators which may subserve this function, it has remained an open question whether such a mechanism can be useful for timing at even the lowest level of cortex. To address this question, we analyze electrophysiological data collected from rats performing a timing task and find evidence that, indeed, timed reward-seeking behavior tracks oscillatory states in primary visual cortex. This kind of finding raises an important question: how is this temporal information stored after the interval has been generated? This process is called interval storage, and we address the sources of noise that might corrupt it in Chapter 3. Specifically, we devise a novel timing task for humans (BiCaP) to address whether memory biases can account for performance on a classification task, in which a subject must decide whether a test interval is more similar to one or another reference interval. We find that they do, and argue that these sources of noise must be accounted for in theories of timing. In Chapter 4, we deal with interval evaluation which is the process of using this stored temporal information to make valuation decisions. We study this process through the lens of foraging behavior. Specifically, we develop and test a framework that rationalizes observed spatial search patterns of wild animals and humans by accounting for the temporal information they gather about their environment, and how they discount delayed rewards (temporal discounting). Lastly, in Chapter 5, we discuss how these processes are integrated and the implications of these findings for theories of timing