Handbook of the Neuroscience of Language

Brigitte Stemmer, Harry A. Whitaker

• Publisher: Academic Press
• Year: 2008
• ISBN:
  9780080564913
• Topic: Languages & Linguistics
• Subtopic: Linguistics
• Index: Languages & Linguistics

In the last ten years the neuroscience of language has matured as a field. Ten years ago, neuroimaging was just being explored for neurolinguistic questions, whereas today it constitutes a routine component. At the same time there have been significant developments in linguistic and psychological theory that speak to the neuroscience of language. This book consolidates those advances into a single reference.

The Handbook of the Neuroscience of Language provides a comprehensive overview of this field. Divided into five sections, section one discusses methods and techniques including clinical assessment approaches, methods of mapping the human brain, and a theoretical framework for interpreting the multiple levels of neural organization that contribute to language comprehension. Section two discusses the impact imaging techniques (PET, fMRI, ERPs, electrical stimulation of language cortex, TMS) have made to language research. Section three discusses experimental approaches to the field, including disorders at different language levels in reading as well as writing and number processing. Additionally, chapters here present computational models, discuss the role of mirror systems for language, and cover brain lateralization with respect to language. Part four focuses on language in special populations, in various disease processes, and in developmental disorders. The book ends with a listing of resources in the neuroscience of language and a glossary of items and concepts to help the novice become acquainted with the field.

Editors Stemmer & Whitaker prepared this book to reflect recent developments in neurolinguistics, moving the book squarely into the cognitive neuroscience of language and capturing the developments in the field over the past 7 years.

• History section focuses on topics that play a current role in neurolinguistics research, aphasia syndromes, and lesion analysis
• Includes section on neuroimaging to reflect the dramatic changes in methodology over the past decade
• Experimental and clinical section reflects recent developments in the field

PART I

METHODS AND TECHNIQUES

CHAPTER 1 Classical and Contemporary Assessment of Aphasia and Acquired Disorders of Language

YVES. TURGEON¹, JOËL. MACOIR²

¹Restigouche Health Authority, Campbellton Regional Hospital, Campbellton, NB, Canada

²Département de réadaptation, Programme de maîtrise en orthophonie, Université Laval, Québec (QC), Canada

ABSTRACT

The detection and diagnosis of language problems are the starting point for all clinical intervention. The choice of the theoretical approach and selection of assessment tools are thus of utmost importance. Classical and contemporary assessment methods for acquired language impairments are discussed with a comparison of clinical–neuroanatomical and psycholinguistic approaches. Bedside evaluation and screening tools provide some rough information on the patient’s global communication profile and may indicate whether more comprehensive assessment is indicated. Comprehensive assessment explores in depth the different aspects of language and depending on the theoretical framework provides information on the type of aphasia or the functional processing components impaired. Specific pathologies such as dementia, traumatic brain injury, and right hemisphere brain damage may require the assessment of specific aspects of language. Finally, the importance of evaluating language in conjunction with other mental functions must be considered.

1.1. INTRODUCTION

The evaluation of language is one of the most important tasks of speech-language pathologists and professionals from a variety of disciplines and backgrounds (neuropsychologists, occupational therapists, physicians, nurses, and so forth). The assessment procedure is often the first contact with clients and also constitutes the starting point of all clinical interventions. Because of the absence of biological markers or simple assessment methods, the early detection or diagnosis of language problems remains dependent on various indirect assessments (i.e., language function must be inferred from the client’s performance on various tasks devised to explore different areas of this function) aimed at identifying specific impairments and eliminating other possible causes.

The main goal of language screening is to determine whether a client has a problem or not; the output of this type of assessment is a “pass” or “fail”, based on an established criterion that could lead to a more extensive evaluation or a follow-up assessment. Diagnosis and differential diagnosis assessments are usually performed to label the communication problem and/or differentiate it from other disorders in which similar characteristics are usually reported. Language evaluation provides the clinician with a detailed description of the client’s baseline level of functioning in all areas of communication in order to identify affected and preserved components, plan treatment, establish treatment effectiveness, or track progress over time through periodic re-evaluations. The clinician must consider not only the different areas of language, but also important related abilities and components such as cognitive functions, pragmatics, emotions, awareness of deficits, and so forth. The selection of evaluation tools is also influenced by the specific objectives of the assessment. Screening for a language disorder is usually performed with standardized screening measures whereas standardized norm-referenced tests are used for diagnosis and differential diagnosis assessments as well as for clinical treatment purposes (baseline, effectiveness, and progress).

In this chapter, we first outline the nature of acquired language deficits as well as reference models for their assessment. We then briefly report classical methods and tests for the assessment of language impairments in aphasia and other pathological affections. Finally, we address the question of the interface between language and other cognitive functions.

1.2. NATURE OF LANGUAGE DEFICITS

Since higher mental functions depend on specialized cerebral substrates, a disturbance of any of these brain areas may lead to acquired impairments of language and communication. These may involve disorders of articulation, word and sentence comprehension and production, reading, and writing, which are commonly regarded as clinical manifestations of acquired language deficits. The majority of assessment tools are designed to evaluate these problems.

1.2.1. Classification of Aphasic Syndromes and Symptoms

There are various classifications for aphasic syndromes. For example, Goodglass (2001) suggested categorizing language deficits under 10 different types. In each of these aphasia types, particular symptoms can be regarded as signs of comprehension and production problems. For example, deficits at the word, sentence, or discourse levels are common forms of comprehension disorders. In contrast, reduced verbal fluency and word-finding difficulties are common forms of production disorders. Some types of aphasic disturbances, such as the loss of grammar and syntax or semantic deficits, have expressive and receptive aspects, and thus contribute to both comprehension and production disorders.

The classical definition of aphasic syndromes includes various categorization systems. Some experts define aphasic syndromes according to the types of language errors. Others focus on language production and related impairments of spontaneous speech. Despite these diverging views, a few clusters of aphasic symptoms have been proposed over the past few decades. It is conventional to group aphasias into two broadly defined categories: fluent and non-fluent. Fluent aphasias are distinguished by fluent speech and relatively normal articulation but difficulties in auditory comprehension, repetition, and presence of paraphasias. Non-fluent aphasias are characterized by relatively preserved verbal comprehension, but significant articulation and spoken production problems. Table 1.1 presents eight classical aphasia syndromes after Beeson and Rapcsak (2006).

Table 1.1 Classical Aphasia Syndromes

Syndromes	Language deficits	Key language errors
Fluent aphasias
Anomic	Normal fluency; good auditory comprehension and repetition	Anomia; may resolve to minimal word-finding difficulties
Conduction	Normal fluency; good auditory comprehension	Phonemic paraphasias; poor repetition
Transcortical sensory aphasia	Normal fluency; preserved repetition; poor comprehension	Verbal paraphasias; anomia
Wernicke	Normal fluency; poor comprehension; poor repetition	Jargon; logorrhea; anomia
Non-fluent aphasias
Transcortical motor	Reduced fluency; good auditory comprehension; good repetition	Reduced spontaneous speech; better naming than spontaneous speech
Broca	Reduced fluency; relatively good comprehension; poor repetition; agrammatism	Slow, halting speech production; phonetic and phonemic paraphasias; anomia; recurring utterances; articulatory impairment
Mixed transcortical	Reduced fluency; preserved repetition; markedly impaired auditory comprehension	Severely impaired verbal expression; anomia
Global	Severe reduction of fluency, severe comprehension deficit; poor repetition	Slow, halting speech production or mutism; articulatory impairment; severe anomia

After Beeson and Rapcsak (2006)

1.2.2. Pure Language Impairments

Aphasia experts discriminate between the aphasias and other disorders that impair communication but do not meet the definition of classical syndromes. A group of these conditions are regarded as “pure” impairments, and include pure alexia, also called letter-by-letter reading, in which the patient reads by spelling the letters out loud. Pure word deafness is a deficit distinct from generalized auditory agnosia in which comprehension and repetition of speech are impaired but reading, writing, and spontaneous speech are preserved. Pure agraphia refers to the inability to program movements necessary to form written words. Finally, agnosia refers to selective impairments of information processing in a single sensory modality (e.g., vision) that is not explained by a primary sensory defect, attention disorder, or language disorder. The most typical example is visual agnosia in which the individual fails to name an object (e.g., a telephone) present in his visual field but can name that same object when allowed to touch it or to hear sounds from that object. Beeson and Rapcsak (2006) view word deafness, pure alexia, and the agnosias as an input problem that may compromise comprehension of spoken and written language. Apraxia of speech, dysarthria, and mutism are considered as production problems. Apraxia of speech is an impairment of motor programming that results in articulatory impairment in the absence of a disturbance of motor control for speech production. Dysarthria is a motor speech disorder in which the speech subsystems (respiration, phonation, resonance, and articulation) are affected. Mutism is the complete inability to produce speech.

A comprehensive language assessment should always be based on typologies of syndromes and symptoms and/or on a theoretical model of language functioning. In the following section, we discuss the two main reference models for language assessment.

1.3. THEORETICAL MODELS FOR THE ASSESSMENT OF LANGUAG...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Contributors
• Preface
• Prologue
• PART I: METHODS AND TECHNIQUES
• PART II: NEUROIMAGING OF LANGUAGE
• PART III: EXPERIMENTAL NEUROSCIENCE OF LANGUAGE AND COMMUNICATION
• PART IV: CLINICAL NEUROSCIENCE OF LANGUAGE
• PART V: RESOURCES
• Glossary
• Index
• Color Plates