The Cognitive Neuroscience of Reading

A Special Issue of scientific Studies of Reading

Rebecca Sandak, Russell A. Poldrack, Rebecca Sandak, Russell A. Poldrack

• Publisher: Routledge
• Year: 2018
• ISBN:
  9781135066642
• Edition: 1
• Topic: Bildung
• Subtopic: Lehrmethoden für Lesekompetenz

This special issue of Scientific Studies of Reading highlights the great deal of progress that has been made recently in understanding the neurobiological foundations of basic processes in reading. The papers demonstrate how functional neuroimaging techniques have provided novel insights into how reading works in the brain, and how these processes may be disorganized in reading disorders. Importantly, they illustrate that understanding how reading works in the brain is not a simple end-goal, but rather reveals new phenomena that will serve to constrain theories of reading. Although these articles make clear that full understanding of these processes is well off in the distance, the editors hope that they will inspire further collaboration between reading researchers and neuroscientists.

Introduction to This Special Issue: The Cognitive Neuroscience of Reading

Russell A. Poldrack
Univeristy of California, Los Angeles

Rebecca Sandak
Haskins Laboratories New Haven, Connecticut

That reading happens in the brain is obvious, but how this occurs has been a focus of scientific investigation for more than 100 years. This special issue of Scientific Studies of Reading highlights the great deal of progress that has been made recently in understanding the neurobiological foundations of basic processes in reading.

Until the last quarter of the 20th century, scientific understanding of the neural basis of reading came almost exclusively from studies of patients with focal brain lesions. The classic work of Déjerine (1891) demonstrated that lesions to the occipital cortex and splenium of the corpus callosum resulted in alexia without agraphia, or the inability to read with a spared ability to write, whereas lesions that included the inferior parietal lobe (angular gyrus) resulted in alexia with agraphia. These results provided an early suggestion that separate regions of the brain might be involved in different components of reading ability. Subsequent work in the 20th century extended these observations; in particular, much work has examined the syndromes of acquired phonological, surface, and deep dyslexia, which can occur following brain lesions (e.g., Coltheart, Patterson, & Marshall, 1980; Patterson, Marshall, & Coltheart, 1985). However, the limits of lesion approaches necessitate a relatively crude mapping of function to structure.

With the advent of safe and widely accessible functional neuroimaging techniques, cognitive neuroscientists have begun to examine the neural basis of reading at a number of different levels of analysis, and the articles in this issue highlight the diversity of approaches and techniques that have been brought to bear. Two broad classes of neuroimaging techniques are used in this work. Psychophysiological imaging techniques, such as event-related potentials and magnetoencephalography (MEG), measure the electrical or magnetic signals that are created by neural activity. These techniques can measure brain activity with high temporal resolution (down to the millisecond level), but their ability to localize activity in the brain is rather limited. Hemodynamic imaging techniques, such as positron emission tomography or functional magnetic resonance imaging (fMRI), measure the blood flow response that occurs when neurons are active. Because this blood flow response is relatively slow (peaking several seconds after the neural activity), these techniques are limited in their temporal resolution. However, they can provide much better spatial resolution than psychophysiological techniques (down to about 1 mm for fMRI).

How Can Neuroscience Inform the Science of Reading?

Neuroimaging clearly produces pretty pictures of brain activation, but it is often asked whether neuroimaging can reveal anything about cognitive processes (such as reading) that is not already known. The articles in this issue demonstrate a number of ways in which this can occur. To highlight one example, there has been a long-standing debate over the role of phonological processing in skilled reading (reviewed by Frost, 1998), with one set of theorists offering online-processing data suggesting rapid activation of phonological representations and another set of theorists highlighting neuropsychological dissociations between phonological and lexical processing. As Sandak, Mencl, Frost, and Pugh outline, neuroimaging has provided converging evidence for the early phonology theory by showing that regions in the ventral visual stream (which have been thought to subserve the "direct" route from orthography to semantics) are sensitive to phonological variables. This finding also highlights the limitations of neuroimaging and the need for converging techniques. For example, fMRI cannot be used to determine when these phonological effects arise during processing; do they occur early in the visual recognition of words, or are they due to later feedback effects? To answer this question, one must use techniques such as EEG-MEG, which provide greater temporal resolution (at the cost of lower spatial resolution). Salmelin and Helenius outline how these techniques have been used to characterize the time course of early visual processes in reading and to show that these early processes are delayed in individuals with reading disabilities.

Another way that neuroimaging can inform the science of reading is by demonstrating common underlying neural mechanisms for tasks that appear to be quite different. Misra, Katzir, Wolf, and Poldrack use this approach to help explain why rapid automatized naming tasks, which involve rapid naming of single letters or other objects, are so strongly predictive of text reading skills. By showing that rapid naming of single letters engages many of the same neural systems as single-word reading, this work shows how simple tasks can be used to decompose the component processes of reading skills.

To fully understand the neural basis of skilled reading, it is also important to understand how reading skills are acquired during childhood. This is made difficult by the fact that the brain is still developing throughout the ages during which children acquire reading skills. Palmer, Brown, Petersen, and Schlaggar discuss a number of fundamental issues regarding how functional neuroimaging can be used to study the development of reading skills. In particular, they highlight several important methodological difficulties that arise with the use of neuroimaging techniques in children and show that these difficulties can be overcome to provide a fascinating picture of the developing brain as it acquires reading skills.

Whereas most neuroimaging studies of reading have focused on the single-word level, the goal of reading is comprehension, so it is also crucial to understand the neural systems involved in syntactic and semantic processing at the sentence level and higher. Caplan outlines a long-standing program of research using neuroimaging to understand sentence comprehension. This work highlights the oft-noted fact that reading is built on top of spoken language, noting that similar neural mechanisms appear to be involved in both written and spoken sentence comprehension.

The articles in this special issue demonstrate how functional neuroimaging techniques have provided novel insights into how reading works in the brain and how these processes may be disorganized in reading disorders. As highlighted in the commentary by Perfetti and Bolger, understanding how reading works in the brain is not a simple end goal but rather reveals new phenomena that will serve to constrain theories of reading. These articles also make clear that a full understanding of these processes is well off in the horizon, but it is our hope that they will inspire further collaboration between reading researchers and neuroscientists. It is precisely this kind of cross-discipline collaboration that defines cognitive neuroscience and that we believe will continue to inform our understanding of the psychology of reading.

Acknowledgements

Each article in this issue received external reviews in addition to our reviews. For their input as expert reviewers, we gratefully thank Susan Bookheimer, Piers Cornelissen, Julie Fiez, Timothy Keller, Bruce McCandliss, Maria Mody, Cathy Price, and Elise Temple.

Requests for reprints should be sent to Rebecca Sandak, Haskins Laboratories, 270 Crown Street, New Haven, CT 06511. E-mail: [email protected]

References

Coltheart, M., Patterson, Κ., & Marshall, J. C. (Eds.). (1980). Deep dyslexia. London: Routledge & Kegan Paul.

Caplan, D. (2004). Functional neuroimaging studies of written sentence comprehension. Scientific Studies of Reading, 8, 225-240.

Déjerine, J. (1891). Sur un cas de cécité verbale avec agraphie, suivi d'autopsie [On a case of word blindness with agraphia, follow-up autopsy]. Mémoires de la Société Biologique, 3, 197-201.

Frost, R. (1998). Toward a strong phonological theory of visual word recognition: True issues and false trails. Psychological Bulletin, 123, 71-99.

Misra, M., Katzir, T., Worf, M., & Poldrack, R. A. (2004). Neural systems for rapid automatized naming in skilled readers: Unraveling the RAN-reading relationship. Scientific Studies of Reading, 8, 241-256.

Palmer, E. D., Brown, T. T., Petersen, S. E., & Schlaggar, Β. L. (2004). Investigation of the functional neuroanatomy of single word reading and its development. Scientific Studies of Reading, 8, 203-223.

Patterson, K., Marshall, J. C., & Coltheart, M. (Eds.). (1985). Surface dyslexia: Cognitive and neuropsychological studies of phonological reading. London: Lawrence Erlbaum Associates, Ltd.

Salmelin, R., & Helenius, P. (2004). Functional neuroanatomy of impaired reading in dyslexia. Scientific Studies of Reading, 8, 257-272.

Sandak. R., Mencl, W. E., Frost, S. J., & Pugh, K. R. (2004). The neurobiological basis of skilled and impaired reading: Recent findings and new directions. Scientific Studies of Reading, 8, 273-292.

Investigation of the Functional Neuroanatomy of Single Word Reading and Its Development

Erica D. Palmer, Timothy T. Brown, Steven E. Petersen, and Bradley L, Schlaggar
Washington University in St. Louis

An understanding of the processing underlying single word reading will provide insight into how skilled reading is achieved, with important implications for reading education and impaired reading. Investigation of the functional neuroanatomy of both the mature and the developing systems will be critical for reaching this understanding. To this end, ongoing methodological advances in functional neuroimaging help to provide imaging data that are increasingly useful in complementing and expanding on results from decades of behavioral research. This article is an overview of progress in using functional neuroimaging to investigate single word reading. Methodological considerations are emphasized, particularly as they pertain to studying reading development. Strategies for overcoming methodological challenges are discussed, along with results of some recent work in which such strategies are applied.

An understanding of how skilled reading is achieved is a critical first step toward improved strategies for reading education and toward identifying, remediating, and possibly preventing developmental deficits in reading. The mature system of skilled readers is a rich source of information for achieving this understanding; however, one must bear in mind that it reflects the end point of years of practice. Therefore, investigation of the developing system is essential, as it is likely to yield important insight into characteristics of the mature system that underlies skilled reading. The question of how the end point of skilled reading is reached is made all the more interesting by the fact that reading is relatively new in evolutionary terms and does not emerge of its own accord. Because reading is a skill that must be taught, it is possible that different teaching techniques, for example, ultimately lead to a common end point but through different routes.

The study of reading and its development can be approached from a number of directions. For example, decades of behavioral research in cognitive psychology have provided an excellent foundation for understanding skilled and developing reading. Investigation of brain activity associated with reading is an approach that can provide data to complement or expand on the results obtained from purely behavioral work. For example, some children may perform certain lexical tasks with accuracy and response latencies that are indistinguishable from those of adults. However, comparison of patterns of brain activity between these two groups of research participants may reveal differences in how such performance is being achieved (cf. Schlaggar et al., 2002).

As another example of how patterns of brain activity might speak to results derived from cognitive psychology, consider a point of difference between competing models of single word reading. The most recent instantiation of the dual-route cascaded model (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001) includes a component called the phoneme system in which the processing underlying word pronunciation is affected by the spelling-to-sound consistency of a word but not by the word's frequency (Coltheart et al., 2001). A model developed under the connectionist approach (Plaut, McClelland, Seidenberg, & Patterson, 1996), in contrast, does not contain any components in which the effect of consistency is independent of the effect of frequency. Patterns of brain activity may help to adjudicate between these two alternatives: Observation of a brain region (or regions) in which activity is modulated by consistency but not by frequency could be explained more straightforwardly by the dual-route cascaded model.

Relating patterns of brain activity to maturational changes and to predictions afforded by cognitive psychology allows researchers to move beyond simply observing which brain re...

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