Blindness and Brain Plasticity in Navigation and Object Perception

John J. Rieser, Daniel H. Ashmead, Ford Ebner, Anne L. Corn

• Publisher: Psychology Press
• Year: 2007
• Print ISBN: 9780805855517
• eBook ISBN: 9781136678936
• Topic: Bildung
• Subtopic: Inklusive Bildung

Research into the development of sensory structures in the brains of blind or visually-impaired individuals has opened a window into important ways in which the mind works. In these individuals, the part of the brain that is usually devoted to processing visual information is given over to increased processing of the touch and hearing sense. This d

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INTRODUCTION

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Theory and Issues in Research on Blindness and Brain Plasticity

John J. Rieser

The content of this volume is focused on perceiving, learning, and remembering about objects and environments when exploring them without vision by locomoting, touching, and listening. It is about how perception, knowledge, and action come to be coupled together in the absence of vision.

Some people who are blind or have severely impaired vision are highly effective at navigating and show high levels of skill in getting from place to place. Some are highly effective at recognizing and manipulating objects and show high levels of skill in daily life, with tools for thought (such as computer keyboards, maps, dictionaries) and tools for action (such as those used in the factory, school, and home). And some are highly effective at understanding and imagining the spatial and temporal relationships that define the areas of science and mathematics. Examples of individuals achieving high levels of effectiveness are apparent in many areas, including participation in athletics (Ponchillia, Strause, & Ponchillia, 2002), spatial orientation (Loomis, Klatzky, Golledge, Ciccinelli, & Pellegrino, 1993), and musical performance (Rauschecker & Korte, 1993). But some individuals are not highly effective. The chapters in this volume are focused on some of the causes that might underlie differences in effective spatial functioning among individuals with severely impaired vision and are aimed at developing implications for future research, education, and rehabilitation.

The content is organized around three main issues—cortical remapping, sensory substitution, and development of individual differences. The chapters were written by scientists from the brain, cognitive, developmental, and rehabilitative sciences. Each author worked to understand the skillful and not-so-skillful levels of perception, learning, and action that can be associated with blindness and visual impairment. One major goal of this volume is to integrate findings from basic research within the brain sciences with research in the cognitive and developmental sciences. The purpose is to examine the implications of findings of the brain sciences showing plasticity with findings from the cognitive and developmental sciences showing cognitive limitations, individual differences, and developmental differences. We hope the resulting discussions are useful in identifying where further research is needed and inspiring people to focus on the problems. A second major goal is to integrate the basic findings and theory from the brain and cognitive and developmental sciences with techniques and theory of the educational and rehabilitative sciences for persons with severe visual impairment. The individual chapter authors were not invited to end by listing recommendations for new methods of rehabilitation. Instead they were invited to write about their own areas of research, believing that the collection will inspire new research and technologies aimed at rehabilitation.

The purpose of this introductory chapter is to describe how the coeditors set the stage for the chapter writers and in this way provide an overview of the central disciplines and main themes of the chapters in the volume.

USE-ORIENTED RESEARCH AND THE INTERDISCIPLINARY AND MULTIDISCIPLINARY NATURE OF THE WORKS

Research orientations can be classified in many ways; for example, basic research, applied research, and mission-oriented research. A defining theme of this collection is use-oriented research. By use-oriented we mean research using scientific methods to understand how the mind and brain work, in the context of a set of practical problems. Stokes (1997) wrote about use-oriented research and focused on Louis Pasteur's research—which resulted in the technique of pasteurization of milk and led to the new field of bacteriology. This volume is focused on how mind and brain accomplish skillful navigation and object perception without vision, while focusing on the practicalities of intervention.

The issues and questions examined here originate from six professional and scientific groups, namely, animal models and brain science, human cognitive neuroscience, cognitive sciences (emphasizing perceptual, cognitive, and developmental psychology), engineering; blind education and rehabilitation, and advocacy. Many of the chapter authors participate actively in two or more of these scientific/professional groups. Findings from scientists working at three of the disciplinary intersections are featured here. One finding consists of recent research from animal models and human brain imaging and suggests that the occipital cortex of people with vision impaired from birth is recruited in nonvisual processing to a greater degree than in sighted people who wear blindfolds. A second finding consists of demonstrations that nonvisual information can, in some cases, substitute neatly for visual information in the control of some tasks. And the third finding consists of demonstrations that visual input relatively early in life may facilitate the development of some types of nonvisual spatial functioning stemming from auditory, tactual, and motor input.

BRAIN IMAGINING STUDIES DEMONSTRATING THE EXPERIENCE-DEPENDENT PLASTICITY OF THE OCCIPITAL CORTEX FOR PROCESSING TACTUAL AND AUDITORY INFORMATION

Brain imaging studies during the last 10 to 20 years have shown differences in the degree to which the occipital cortex of persons with congenitally impaired vision participates in nonvisual processing compared to the occipital cortex of blindfolded sighted persons.

For processing tactual and haptic stimuli such as reading Braille or identifying raised line Roman letter this has been shown via the use of positron emission tomography, functional magnetic resonance imagery, and transmagnetic resonance and evoked potentials (Burton et al., 2002; Cohen et al., 1997; Melzer et al., 2001; Pascual-Leone, Wassermann, Sadato, & Hallett, 1995; Roeder, Rosler, & Neville, 2001; among others). The same methods have been used to demonstrate this for processing auditory information for spatial localization, pattern recognition, and language comprehension (Rauschecker & Korte, 1993; Roeder, Roesler, & Neville, 2000).

This body of empirical work makes it clear that the occipital cortex of people born with severely impaired vision is participating in the processing of non-visually explored spatial inputs from touch and from audition to a greater or different degree than in sighted persons who are blindfolded. Little is known about the possible brain plasticity of persons who lost their vision after infancy or early childhood. Little is known about the possible plasticity of persons who had severe but partial losses of vision involving, for example, only their visual fields, as in the case of macular degeneration or advanced glaucoma, or their acuity and contrast sensitivity, as in the case of congenital cataracts. And finally, virtually nothing is known about the implications of such plasticity for gaining high levels of skill at spatial functioning. A major goal of this volume is to discuss what is and is not yet known, what needs to be known, and the possible implications for spatial functioning and sensory substitution.

SENSORY SUBSTITUTION AND SPATIAL FUNCTIONING

The concept of sensory substitution is that information about objects and the environment that is usually provided by one sensory modality can be supplied by other modalities. This is a fundamental basis of education and rehabilitation designed for learners who are blind or have severe visual impairment, and it is clear that touch, hearing, and motor exploration can provide information about objects and environments that many people typically glean via vision (Blasch, Wiener, & Welsh, 1997). For example, hearing can supply information that is used to steer locomotion around walls (Ashmead et al., 1998), and hearing is used as an aid to dynamic spatial orientation when people walk in unfamiliar surroundings (Easton & Bentzen, 1999). Recent quantitative research is specifying the acoustic frequencies that specify the locations of objects and the sensitivities of listeners with impaired vision to them (Ashmead, Davis, & Northington, 1995).

When people locomote, it is important for them to keep up to date on their spatial orientation, that is, the changing network of self-to-object distances and directions. When walking with vision or with severely impaired vision, people tend to rely on vision for orientation, but when walking without vision people navigate with good precision by integrating the distances walked and turned during the path of their walk (Loomis et al., 1993; Philbeck, Klatzky, Behrmann, Loomis, & Goodridge, 2001; Rieser & Pick, 2002; Thinus- Blanc & Gaunet, 1997). In addition, nonvisual cues can be used effectively to steer walking along straight lines, without unintended veering (Guth & LaDuke, 1995; Millar, 1999). When exploring new environments by walking, people not only keep up to date on their spatial orientation relative to different places along their path but they also learn the spatial layout of objects and other landmarks encountered along the way (Haber, Haber, Penningroth, Novak, & Radgowski, 1993; Rieser, Lockman, & Pick, 1980; Wanet-Defalque, Vanlierde, & Michaux, 2001).

Finally, active touch provides important information about the shapes of objects as well as the texture and rigidity of their materials (Lederman & Klatzky, 1997), faces (Kilgour & Lederman, 2002) and in addition is a good basis for reading Braille. Although it is clear that hearing, active touch, and active motor exploration can provide information to substitute for vision, what are not clear are what forms of information combine precision with range and ease of perceiving, and what accounts for individual differences in how efficiently different individuals learn to use the information.

DEVELOPMENTAL AND INDIVIDUAL DIFFERENCES IN SPATIAL FUNCTIONING AMONG PERSONS WITH SEVERE VISUAL IMPAIRMENT

As noted above, there is a broad range of individual differences in the spatial functioning of persons who are blind or have severe visual impairment (e.g. Barth & Foulke, 1979; Long & Hill, 1997), and some believe that the range of variation is greater among persons with severe visual impairment than among persons with normal vision (Warren, 1994). Rieser, Hill, and their colleagues found this to be the case in an unpublished study of the spatial orientation of 40 persons born without vision compared to 25 persons who lost vision later in childhood. The standard deviation of those with early loss of vision was nearly twice that of the late-onset group. Although the top 10 performers were equally divided across the two groups, the worst 15 performers were all congenitally blind.

In the case of some areas of nonvisual spatial functioning, the differences seem to follow a developmental pattern: People whose blindness or severely impaired vision occurred after a period of normal vision during childhood seem to develop better nonvisual skills than those who are born with severely impaired vision. This developmental pattern seems to apply to some spatial skills; for example, dynamic spatial orientation (Easton & Bentzen, 1999; Mor-rongiello, Timney, Humphrey, & Anderson, 1995; Rieser, Guth, & Hill, 1986; Rieser, Hill, & Taylor, 1992; but see also Loomis et al., 1993). However, the development of other nonvisual spatial skills such as listening to detect walls and other obstacles, may not show such a developmental pattern (Ashmead et al., 1998; Erin & Corn, 1994).

SEVEN SPECIFIC ISSUES ON WHICH THE CHAPTERS ARE FOCUSED

The chapters in this volume are aimed at answering one or more of the following specific questions involving blindness and brain plasticity:

1. Given that for people with early onset blindness the visual cortex is recruited to participate in tactile processing, what are the possible benefits of the recruitment to tactile pattern recognition and Braille reading and for object manipulation and object perception?
2. Given that for people with early onset blindness the visual cortex is recruited to participate in auditory processing, what are the possible benefits of the recruitment to auditory localization, sensitivity to auditory information for obstacles, and sensitivity to language or music?
3. To what degree does the recruitment of visual cortex to nonvisual spatial processing depend on heavy “doses” of experience using a particular nonvisual spatial skill versus to what degree is the recruitment of visual cortex a developmental phenomenon and heavily determined by the age of onset of blindness?
4. Given different tasks of daily living (for example wayfinding and spatial orientation, manipulating objects when using tools to cook, dress, or build things) and academic learning (for example reading Braille, comprehending text, understanding scientific concepts), for which of them does nonvisual information seem to substitute effectively and result in satisfactory learning and for which does sensory substitution seem to fall short?
5. Congenital and early onset blindness are associated with a larger range of individual differences in spatial skill than blindness acquired later in life and may be associated with a lower mean level of performance. Whereas the top-performing individuals with congenital blindness match the top-performing late-blinded and blindfolded sighted individuals, there are many more low-performing individuals among the congenitally blind. These individual differences among congenitally blind people cut across different etiologies of blindness. Can they be associated with different sensory substitution strategies or cognitive strategies? Can they be associated to different patterns of participation of the visual cortex in nonvisual spatial processing?
6. What do we already know about experience-dependent brain plasticity that can be applied to steer educational and rehabilitation interventions? What are the critical questions that need to be answered?
7. What do we already know about sensory substitution and spatial functioning and how can emerging technologies be used to steer educational and rehabilitation interventions? What are the critical questions that need to be answered?

CONCLUSIONS: THREE MAJOR ISSUES AND RELATED QUESTIONS TO KEEP IN MIND WHILE READING THIS VOLUME

Brain Plasticity—Cortical Remapping of Sensory, Sensorimotor, and Cognitive Functioning as a Function of Blindness

• What is the evidence that cortical remapping occurs in general?
• What is the evidence that the occipital cortex is remapped for people who are blind?
• How long-lived is the remapping? Are there developmental constraints on the remapping?
• What is the effect of the remapping on spatial functioning?
• What are the implications of the remapping for educational and rehabilitative strategies?

Developmental and Individual Differences in Cognitive Function and Learning

• What is the evidence that early visual experience either matters or does not matter for skill in navigating environments and manipulating objects?
• Is the range of individual differences in spatial functioning broader among people with congenital blindness and congenital severe visual impairment than among people with later-onset blindness or visual impairment?
• How might cortical remapping influence individual differences in spatial functioning among people who are blind or severely visually impaired?
• How mig...

Table of contents

• Front Cover
• Half Title
• Title Page
• TITLES OF RELATED INTEREST
• Copyright
• Contents
• Color Plate Figures
• Preface
• Half Title
• PART I INTRODUCTION
• PART II EXPERIENCE-DEPENDENT RECRUITMENT OF VISUAL CORTEX FOR NONVISUAL LEARNING AND DEVELOPMENT
• PART III PERCEPTION, SENSORY SUBSTITUTION, AND COGNITIVE STRATEGIES
• PART IV FROM USE-ORIENTED RESEARCH TO APPLICATION
• Author Index
• Subject Index