Cognitive Electrophysiology of Attention

Signals of the Mind

George R. Mangun

• Publisher: Academic Press
• Year: 2013
• Print ISBN: 9780123984517
• eBook ISBN: 9780123984968
• Topic: Psychology
• Subtopic: Cognitive Psychology & Cognition
• Index: Psychology

Cognitive Electrophysiology of Attention explores the fundamental mechanisms of attention and related cognitive functions from cognitive neuroscience perspectives. Attention is an essential cognitive ability that enables humans to process and act upon relevant information while ignoring distracting information, and the capacity to focus attention is at the core of mental functioning. Understanding the neural bases of human attention remains a key challenge for neuroscientists and psychologists, and is essential for translational efforts to treat attentional deficits in a variety of neurological and psychiatric disorders. Cognitive electrophysiology is at the center of a multidisciplinary approach that involves the efforts of psychologists, neuroscientists, neuropsychologists, psychiatrists, and neurologists to identify basic brain mechanisms and develop translational approaches to improve mental health. This edited volume is authored by leading investigators in the field and discusses methods focused on electrophysiological recordings in humans, including electroencephalography (EEG) and event-related potential (ERP) methods, and also incorporates evidence from functional magnetic resonance imaging (fMRI). Cognitive Electrophysiology of Attention illuminates specific models about attentional mechanisms in vision, audition, multisensory integration, memory, and semantic processing in humans.- Provides an exhaustive overview of attention processes, going from normal functioning to the pathological, and using a combination of methodological tools- An important reference for electrophysiology researchers looking at underlying attention processes rather than the methods themselves- Enables researchers across a broad range of cognitive-process and methodological specialties to stay current on particular hypotheses, findings, and methods- Edited and authored by the worldwide leaders in the field, affording the broadest, most expert coverage available

Section II

Feature and Object Attention

Outline

Introduction

Chapter 8 Object-Category Processing, Perceptual Awareness, and the Role of Attention during Motion-Induced Blindness

Chapter 9 Feature- and Object-Based Attention

Chapter 10 Neural Mechanisms of Feature-Based Attention

Chapter 11 Effects of Preparatory Attention to Nonspatial Features in the Visual Cortex

Chapter 12 The Neural Basis of Color Binding to an Attended Object

Chapter 13 Switching Attention between the Local and Global Levels in Visual Objects

Chapter 14 Contour Integration

Chapter 15 Attentional Control of Multisensory Integration is Preserved in Aging

Introduction

Face invisible – a vase seen instead.

Space divisible

into the haves and have nots

at least in the head.

Attentional fates determined early on by wheres

more than whats though both may matter

for the neural chatter

in a brain laid out to represent the world as it is.

ERPs the electrical whiz kid

that slices and dices time and space whether

readily accessible or somewhere hid

so that cognitive neuroscientists can continue to save face in the competition

about the whys and wherefores of visual cognition.

By Marta Kutas

Chapter 8

Object-Category Processing, Perceptual Awareness, and the Role of Attention during Motion-Induced Blindness

Joseph A. Harris^1,2, David L. Barack^1,2,3, Alex R. McMahon¹, Stephen R. Mitroff^1,2 and Marty G. Woldorff^1,2,4,5, ¹Center for Cognitive Neuroscience, Duke University, Durham, NC, USA, ²Department of Psychology & Neuroscience, Duke University, Durham, NC, USA, ³Department of Philosophy, Duke University, Durham, NC, USA, ⁴Department of Psychiatry, Duke University, Durham, NC, USA, ⁵Department of Neurobiology, Duke University, Durham, NC, USA

Abstract

Perceptual information represented in the brain, whether a viewer is aware of it or not, holds the potential to influence subsequent behavior. Here we tracked a well-established event-related-potential (ERP) measure of visual-object-category processing, the face-specific ventrolateral-occipital N170 response, across conditions of perceptual awareness. To manipulate perceptual awareness, we employed the motion-induced-blindness (MIB) paradigm, in which covertly attended, static, visual-target stimuli that are superimposed on a globally moving array of distractors perceptually disappear and reappear. Subjects responded with a button press when the target images (faces and houses) actually physically occurred (and thus perceptually appeared) and when they perceptually reappeared after an MIB episode. A comparison of the face-specific N170 ERP activity (face-vs-house responses) revealed robust face-selective ERP activity for physically appearing images and no such activity for perceptual reappearances following MIB episodes, suggesting that face-specific processing had continued uninterrupted during MIB. In addition, electrophysiological activity preceding an actual appearance of a target image, collapsed across face and house image types, was compared to that preceding the perceptual reappearance of a continuously present image (following MIB). This comparison revealed a parietally distributed positive-polarity response that preceded only reappearances following MIB. Such a result suggests a possible role of parietally mediated attentional capture by the present-but-suppressed target in the reestablishment of perceptual awareness at the end of an MIB episode. The present results provide insight into the level of visual processing that can occur in the absence of awareness, as well as into the mechanisms underlying MIB and its influence on perceptual awareness.

Keywords

Attention; Awareness; ERP; Face processing; Motion-induced blindness; Perception

Acknowledgments

This work was supported by a grant from the National Institutes of Health (R01-MH060415) to M.G.W.

Introduction

The extent of visual processing that occurs outside of awareness is an unresolved issue of broad importance to the field of cognitive neuroscience. Research examining this question is predicated on the notion that any information that is represented in the brain, whether an individual is aware of it or not, holds the potential to affect subsequent behavior in a relevant way. Identifying the information coded in the brain with or without explicit awareness therefore enhances our understanding of what determines or influences behavior.

One method of identifying perceptual processes that occur in the absence of awareness is through the dissociation paradigm, which is comprised of several essential components (Reingold & Merikle, 1988). In vision, for example, once a visual perceptual process of interest is identified, two measures of this process are obtained as a viewer is presented with images invoking this process. An explicit measure is derived from the viewer's behavioral output or report regarding the content of the images, which serves as an index of their level of awareness. A second measure is typically implicit in nature and reflects the processing of the image content of which the viewer may not be aware, as in the case of behavioral priming or neural responses. Through any number of possible manipulations of the presentation parameters of relevant images (e.g., a manipulation using motion-induced blindness (MIB), for example, as described below), conditions are created in which images are present but not visible to the viewer, which is reflected in a marked decrease of the explicit measure (Kim & Blake, 2005). The implicit measure is then probed in these conditions of reduced awareness vs. those with full awareness. If the implicit measure of the perceptual process is shown to be intact, regardless of the viewer's ability to report relevant image content, then it is inferred that this process is occurring in the absence of awareness (Holender, 1986; Reingold & Merikle, 1988).

Discrimination of object category by the visual system is evident through multiple measures, behavioral and neural, and thus provides explicit and implicit indices that can be used to examine its relationship with visual awareness. A particularly well-studied and readily measured process reflecting such categorical discrimination is face-specific processing. Neural reflections of this process have been most directly observed as enhancements of specific neural responses to face images relative to images of any other object category that are observed in functional modules of the ventral extrastriate and ventral temporal cortices in human and nonhuman primates (Allison et al., 1994; Harries & Perrett, 1991; Perrett, Hietanen, Oram, & Benson, 1992). In normal human observers, for example, face-specific responses have been localized to areas in the fusiform gyrus and lateral occipital cortex using function magnetic resonance imaging (fMRI) measures (Kanwisher, McDermott, & Chun, 1997; Puce, Allison, Gore, & Mccarthy, 1995), and in the occipitotemporal sulcus through intracranial recordings in patients (Puce, McCarthy, Bentin, & Allison, 1997). Using scalp-recorded event-related potential (ERP) measures, face-specific processing has been recorded as a negative-polarity amplitude enhancement over lateral–inferior temporal–occipital regions, peaking at ∼170 ms after stimulus onset (Bentin, Allison, Puce, Perez, & McCarthy, 1996), often followed at longer latencies (∼300–800 ms) by a smaller amplitude but longer duration negative wave with a very similar scalp distribution (Harris, Wu, & Woldorff, 2011; Philiastides, Ratcliff, & Sajda, 2006). These high temporal resolution electrophysiological measures of this process are especially useful indices of this relatively high-level of object-category discrimination that may not require an explicit report of image content, and thus can serve as an informative implicit measure of this process.

MIB is a relatively recently discovered experimental manipulation that can be used for disrupting visual awareness of target images. In MIB, parafoveally presented static targets are superimposed on a globally moving array of distractors. While maintaining fixation at a specific nontarget spatial position (typically centrally located) and covertly attending to these ever-present static targets, viewers periodically lose and regain awareness of them (Bonneh, Cooperman, & Sagi, 2001). This striking perceptual phenomenon provides a novel and robust manner by which to attenuate visual awareness experimentally and serves as an appealing method by which to examine face-processing in the absence of awareness. To this end, experimenters use MIB to gauge the extent of target-associated processing that occurs in the absence of awareness by probing target-specific processing within and outside of MIB episodes (Kim & Blake, 2005).

A number of behavioral studies have suggested that MIB acts through a high-level or late mechanism to disrupt visual awareness. For example, the formation of negative afterimages, a process likely mediated by a relatively low-level of visual processing, is uninterrupted by MIB (Hofstoetter, Koch, & Kiper, 2004). Similarly, orientation-specific aftereffects persist following exposure to a Gabor patch of a given angle, regardless of whether it was presented during or outside of MIB (Montaser-Kouhsari, Moradi, Zandvakili, & Esteky, 2004; Rajimehr, 2004). Also, higher-level processes of object representation and updating have been demonstrated to occur during MIB. For example, one experiment showed that the sudden physical offset of a perceptually suppressed target “breaks” the blindness episode, making the viewer aware of this transient change. This in turn suggested that changes in the gross physical properties of the target (i.e., its presence or absence) were being processed during MIB episodes, despite the objects being invisible to the subject (Mitroff & Scholl, 2004). This group also showed that if two previously disparate objects are linked with a connecting line during a blindness episode, they tend to reemerge simultaneously as one object, suggesting that object-based representations can be updated during MIB (Mitroff & Scholl, 2005).

In addition to studies focusing on the visual processes that occur during MIB, research examining the more general dynamics of MIB has supported a mechanism of disruption that acts relatively late in terms of visual processing stages. Specifically, MIB episodes associated with specific static targets are shown to be enhanced (to occur more frequently and for greater durations) when those targets are covertly attended (Carter, Luedeman, Mitroff, & Nakayama, 2009). This is in contrast with a low-level mechanism of disruption, such as that seen in sandwich masking wherein visual mask stimuli occur immediately before and after a target image, which does not appear to be modulated by covert attention (Harris et al., 2011). In addition, the manner in which the visual system accounts for the static target location during blindness episodes is similar to the high-level mechanisms of perceptual filling-in observed for the retinal blindspot or scotomas (Hsu, Yeh, & Kramer, 2006). For example, superimposing a stationary grid over a static target and moving array results in the target being replaced by the stationary pattern, in what amounts to a perceptual filling-in effect based upon context (New & Scholl, 2008). In general, evidence has suggested a rivalrous relationship between the static target and array of moving distractor stimuli that is manifested in the temporal properties of MIB (Carter & Pettigrew, 2003). Although relatively few neural studies of MIB have been performed, this proposed rivalrous relationship has been supported by functional MRI measures that show a competitive relationship between ventral and dorsal visual regions associated with the static target and motion array, respectively, which track the perceptual state of the subject in their respective levels of activity (Donner, Sagi, Bonneh, & Heeger, 2008; Scholvinck & Rees, 2010). Nevertheless, a consensus on the neural mechanisms underlying MIB has yet to be reached.

In the present study, we employed the high temporal resolution measures of face-specific neural processing afforded by electroencephalogram (EEG) to examine the extent and nature of object-category processing that can occur during MIB. In addition, the possible mechanism by which MIB exerts disruption of awareness was investigated. These processes were probed by examining responses associated with the perceptual onset of a static target following a blindness episode. Specifically, two conditions were employed: one in which the disappearance and reappearance of target images was physical in nature (a “static” condition in which a target image actually appeared or disappeared), and the ot...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Preface
• Foreword
• Contributors
• Acknowledgments
• Section I: Spatial Attention
• Section II: Feature and Object Attention
• Section III: Attention and Cognitive Processes
• Index