Cathleen M. Moore - US grants

DESCRIPTION (provided by applicant): There is a great deal of evidence that eye movements and attention are linked. However, evidence regarding the nature of the link is sometimes contradictory and lacking. Specification of the relationship between the two systems would allow us to consider attention, which is a poorly specified construct, within the relatively concrete and neurally well understood domain of eye movements. We propose to investigate the relationship between attention and eye movements within a new domain to help resolve some of the contradictions and fill in some of the gaps of knowledge. Specifically, we seek to understand the relationship between attention and eye movements through an investigation of attentional resolution, which is the precision with which one can discretely move attention among closely spaced items. Attentional resolution is remarkably coarse given the precision with which people can perceive simply that there are multiple items present. Eye movements, it seems, may be limited in a similar way; counting items in a closely spaced display, for example, is no easier when one is allowed to fixate the items than when one must rely on attention only. Together, these observations suggest that oculomotor limitations may determine at least some attentional limitations (or vice versa), thereby providing a specific link and domain of inquiry between the two systems. We will begin by comparing attentional resolution to saccadic resolution, which is the precision with which people can move their eyes to individual items. We hypothesize that the limits of attentional control are imposed by the limits of saccadic control, and therefore that attentional resolution will be indiscriminable from or coarser than saccadic resolution. We will then relate the instability of ocular fixation to the coarseness of attentional resolution. We hypothesize that the limitations of attentional resolution are at least partly determined by the spatial uncertainty that is created by ocular jitter during fixation, and therefore that attentional resolution will be finer when that jitter is eliminated by optically stabilizing the display. Finally, we will assess how experimental manipulations that are known to affect saccadic behavior affect attentional resolution. We hypothesize, for example, that transient adaptation of the saccadic system will transfer to the attentional control system and alter observers' attentional resolution.

This project is concerned with how the human visual system is able to maintain an up-to-date representation of the world when the world and the position of the person in the world are constantly changing. Consider, for example, a driver on a busy street. As the car moves down the road, new objects come into view and other objects go out of view. At the same time, objects out it the world, such as pedestrians and other vehicles, are independently changing course. This example highlights how critical it is that visual information be dynamically updated. This project will test the hypothesis that the updating process is guided by the viewer's current interpretation of what objects are out in the world and where they are relative to each other. The implication is that the updating process is active and viewer dependent.

Understanding the dynamic process of representational updating can facilitate the design of human-machine interfaces, roadways, and other artifacts by allowing designers to take into account the strengths and weaknesses of human visual processing. Knowing how the visual representations are updated can also guide educational programs for drivers, lifeguards, air traffic controllers, heavy machine operators, airport security screeners, and others who rely on careful scrutiny of a visual environment.

DESCRIPTION (provided by applicant): This research investigates intersensory mechanisms that underlie the influence of auditory stimuli on visual perception. Findings from single-cell neurophysiology, event-related brain potentials, and functional MRI indicate that neurons in cortical areas that were once thought to be unisensory can be driven by stimuli from multiple modalities. Moreover, the timing of multisensory-driven activity is such that it is unlikely to be due to just to feedback from anatomically later cortical areas. A set of recently reported behavioral effects showing the enhancement of visual perception from informationally unrelated but concomitantly presented auditory stimuli seem to be manifestations of these multisensory mechanisms. To date, however, these effects have not been understood in terms of any common intersensory mechanism. This research tests the audiovisual temporal-encapsulation hypothesis which states that an abrupt transient auditory stimulus defines a temporal window within which the representation of visual stimuli that appear in that time window are isolated from interaction with temporally surrounding visual information. This hypothesis can account for all of the effects reviewed above and it makes novel predictions beyond these, which are the focus of the present proposal. Significantly, the intersensory effects that have been reported in the literature are primarily examples of visual facilitation by concomitant auditory stimuli. The new predictions that we have derived from the audiovisual temporal encapsulation hypothesis are examples of impaired visual perception by concomitant auditory stimuli, which make them especially powerful for testing the hypothesis. The general idea is that if visual information is encapsulated by concomitant auditory stimuli, then it follows that tasks that require integration o that encapsulated visual information with information sampled at a different time will be impaired. This idea will be tested in three specific aims. Specific Aim 1 tests the effects of auditory stimuli in a visual integration task. Specific Aim 2 tests the effects of auditory stimulion the processes by which visible persistence for moving stimuli is actively suppressed known, as motion deblurring. Specific Aim 3 tests the effects of auditory stimuli on the processes by which visual information is suppressed during eye movements, known as saccadic suppression. If confirmed, the audiovisual temporal-encapsulation hypothesis could explain why people are susceptible to auditory distraction when engaged in what are primarily visual tasks (e.g., driving). Moreover, the encapsulation process might be a mechanism that is subject to failure in impaired states due to drugs, alcohol or disease. It may also be a mechanism that is subject to decline with age.

Project Summary The goal of this work is to characterize changes in visual processes that transform the 2-dimensional retinal image into object-based 3-dimensional representations of the world as a function of location within the visual field. These processes?referred to collectively as perceptual organization?are critical to the success of more complex visual tasks including important everyday tasks like reading, recognizing individuals, and following dynamic events on a screen or in the world. The underlying neurophysiology of the most fundamental components of perceptual organization suggest the hypothesis that perceptual organization is relatively poor for information in peripheral regions of the visual field compared to central regions. We will test that hypothesis in this work. Part of the significance of this work is that macular degeneration, which is the leading cause of blindness in people over the age of 65, and is expected to affect nearly 2 million individuals in the U.S. by 2020, is characterized by progressive loss of vision in central regions of the visual field. Individuals with macular degeneration therefore have to learn to rely on information in their periphery, and many interventions for the disease focus on increasing the size of peripheral information to compensate for known decreases in spatial resolution with eccentricity. Despite the success of these interventions to improve sensitivity to peripheral stimuli, many patients continue to suffer dysfunction in more complex, and critical for everyday life, tasks such as reading and recognizing faces. We hypothesize that an important part of this residual dysfunction is caused by the need to rely on peripheral perceptual organization which yields relatively poor 3D models of the world, even if edges and other low-level features are perfectly discriminable. This project will (1) quantify a set of four basic perceptual organization processes that are directly relatable to the simple neurophysiological mechanisms that have been identified and that provide motivation for the basic hypothesis, (2) test the hypothesis that an important downstream process that depends on perceptual organization ? object-based attention ? also decreases in effectiveness in more peripheral regions of the visual field and (3) test the hypothesis that changes in perceptual organization as a function of location in the visual field can predict changes in object-based attention within individual observers. If this work provides support for the basic hypotheses being tested, then follow-up work will extend the measurements to patients with central visual-field loss and ask whether their specific dysfunctions can be accounted for by reliance on relatively poor perceptual organization and if so, seek to develop interventions that either improve or compensate specifically for this dependence.

PROJECT SUMMARY/ABSTRACT Breast cancer has the highest incidence of cancer for women in the U.S. and across the world. Despite advances in technology?from film-screen images to Full Field Digital Mammography (FFDM) and now to Digital Breast Tomosynthesis (DBT)?the yearly miss rate has remained stubbornly stable, ranging between 10-30% at screening. Technology alone is not reducing errors of omission; we need to understand the specific challenges faced by the human readers interpreting the images, and the specific errors that they lead to. Satisfaction of Search (SOS) refers to the fact that, after having detected a first lesion in a case, the miss rate for additional lesions in the same case is substantially elevated. This specific type of error has been shown to account for 30% of misses in the domains of Radiology where it has been studied, including chest radiography and Computed Tomography. And yet, it has never been studied in the domain of breast cancer. Thus, there is a critical need to determine how SOS contributes to errors in breast cancer screening. In the present project we will determine the rates of occurrence and the underlying causes of SOS in FFDM and DBT. We have devised a novel method that overcomes limitations of previous methods and that is optimized for use in FFDM and DBT. Previous approaches to studying SOS involved the photographic addition of artificial lesions to images, which is not feasible for breast imaging. Instead, we will construct a database of naturally occurring cases that is structured for studying SOS. This will involve the collection of multiple-lesion cases and controlled single-lesions cases, where the former are matched with the latter on key diagnostic dimensions, such as lesion type, lesion size, and breast density. In two main experiments (one with FFDM and one with DBT), radiologists will read cases from the experimental set, marking the locations and diagnoses for benign and malignant lesions. Signal-detection analyses over dual- and single-lesion cases will be used to estimate the rate of SOS. Eye position and pupil diameter will be tracked as participants read each case. These data will allow us to assess the prevalence of different known causes of SOS: (a) premature termination, in which search following first lesion detection is less comprehensive compared with single-lesion control cases; (b) perceptual set, in which, after having detected a first lesion, participants are biased to find subsequent lesions with similar perceptual features, leading to reduced sensitivity in the detection of perceptually dissimilar targets; and (c) resource depletion, in which the demands of maintaining information about a first-detected lesion in memory reduce available perceptual/cognitive resources, thereby reducing the efficiency of subsequent search. Understanding the rates and underlying causes of SOS in breast cancer detection will lay the foundation for planned future work to develop training programs and best practices that mitigate the specific causes of SOS errors and thereby reduce miss rates in breast cancer screening.