Mechanisms underlying writing and speech in aphasia

As a parallel to the dual decoding concept for processing of written language we proposed that phonological encoding does not necessarily occur in writing and that the phonemic and graphemic subsystems can be independent on the one-word level. This hypothesis was tested by comparing oral and written performance in a picture-naming task in Broca's and Wernicke's aphasics. In addition, the residual tacit knowledge of the orthographic properties of the names of the pictures was examined with a multiple-choice recognition task. The principal finding is that Broca's aphasics who were better in written than in oral naming showed more graphemically and semantically motivated errors than aphasics who were better in oral than in written naming, the latter producing more phonemically motivated errors. This result supports the dual encoding concept for writing on the singleword level, implying a direct route from the mental lexicon to the graphemic system in parallel with a route mediated by the phonemic system. Multiple-choice recognition was found to be superior to both oral and written performance in both Broca's and Wernicke's aphasics.     

Production deficits in aphasia: A voice-onset time analysis

An experimental study was conducted to examine phonetic and phonemic deficits in the speech production of aphasics. Subjects included four Broca's aphasics, four Conduction aphasics, five Wernicke's aphasics, one nonaphasic dysarthric patient, and four normal controls. The subjects read a list of words containing word-initial stop consonants which were subsequently measured acoustically for voice-onset time. The results showed that Broca's aphasics exhibit a more severe production disorder than Conduction aphasics who in turn exhibit a more severe disorder than Wernicke's aphasics, in accord with clinical observations. In addition, although Broca's aphasics produced both phonetic and phonemic errors, the results showed that they have a pervasive phonetic disorder which affects their correct target productions as well as the total number of phonetic errors produced. This deficit however seems to be a speech deficit rather than a low-level motor control problem. In contrast, the Wernicke's aphasics show a deficit characterized by isolated phonemic mistargeting errors. Finally, the pattern of productions for the Conduction aphasics indicates that some patients show a predominantly phonetic disorder similar to the Broca's aphasics and others show predominantly a phonemic disorder similar to the Wernicke's aphasics.     

Aphasia type and aging

We analyzed the relationship between age and clinical type of aphasia in 167 right-handed men who had suffered cerebrovascular accidents. Patients with unequivocal diagnoses as Broca's, Wernicke's, anomic, conduction, and global aphasics were considered. The median age of the Broca's group (51 years old) was significantly lower than that of the total group (55.8 years old), while the median age of the Wernicke's group was significantly higher (63 years old). Moreover the incidence of Wernicke's aphasia increased steadily with age, while incidence of the other types of aphasia peaked in the sixth decade and then diminished with increasing age.     

The effects of grammatic class and cue type on cueing responsiveness in aphasia

This study investigated the effects of two types of cues (semantic and phonemic) and two grammatic classes (noun and verb) on cueing responsiveness. Subjects consisted of 10 Broca's, 10 Wernicke's, 8 conduction, and 8 anomic aphasics. Cues were administered following failure to name on confrontation. Responsiveness to the two types of cues was dependent on aphasic type and grammatic class. Broca's and conduction aphasics responded better to phonemic cueing, while anomic aphasics were more responsive to semantic cueing. With regard to grammatic class, aphasics responded better to phonemic cueing on nouns; however, no significant difference between types of cues was demonstrated on verbs. Neuropsychological implications for the cueing and naming processes are discussed.     

The nature of the phonological disorder in conduction aphasia

Sequences of attempts to name pictured objects were used to examine phonological dysfunction in three diagnostic subgroups of aphasia. A prevalence of "phonologically-oriented sequences" (i.e., those sequences that contained only attempts with a phonological resemblance to the target word) was found to be a diagnostic criterion for conduction aphasia. When compared to a group of Broca's (n = 7) and Wernicke's (n = 5) aphasics, all the conduction aphasics (n = 6) produced proportionately more of such phonologically-oriented sequences on a picture naming test. An examination of the phonologically-oriented sequences produced by the conduction aphasics indicates that speech production in conduction aphasia involves dysfunction at an early stage of sound-encoding. The theoretical implications of this view are discussed.     

Syntactic and semantic processes in aphasic deficits: The availability of prepositions

The availability of a specific category of closed class items (prepositions) was examined in Broca's and Wernicke's aphasia. The role of prepositions was varied (syntactic/semantic) in two tasks: one requiring production of prepositions and the other acceptability judgments. Overall, it was easier to perform the acceptability task than to produce the target item. In the judgment task, Wernicke's aphasics more accurately determined the acceptability of prepositions in their syntactic role than in their semantic role, but Broca's aphasics showed no such difference. In the production task, Wernicke's aphasics again were more likely to produce prepositions which were in a primarily syntactic role. Broca's aphasics, however, failed to produce such syntactically based prepositions. The results suggest that the availability of a given closed class vocabulary form is not merely a function of its class membership but also of its functional role, and this fact serves to distinguish aspects of Broca's and Wernicke's aphasics' deficit.     

Immediate memory span, recognition memory for subspan series of words, and serial position effects in recognition memory for supraspan series of verbal and nonverbal items in Broca's and Wernicke's aphasia

Four Broca's aphasics, four Wernicke's aphasics, and four matched controls were investigated on three verbal and one visual short-term memory tasks. Experiment 1 considered memory span and subspan recognition memory for verbal items and Experiment 2 assessed serial position effects in supraspan verbal recognition memory. The Broca's aphasics demonstrated verbal memory deficits, which could not be attributed to linguistic disturbances, while the verbal memory deficiencies seen with the Wernicke's aphasics could be regarded as secondary to linguistic defects. In Experiment 3, where visual recognition memory was investigated, only the Broca's aphasics showed deficient performance. The wider context of deficient mnemonic performance in aphasia is discussed.     

Syntactic component in language responsible cognitive structure: Neurological evidence

From the results of a broad ranging comprehension test, a hierarchy of difficulty emerged that is shared by the two groups of aphasics (Broca's and Wernicke's aphasics) and by the control group of normal subjects. The parallelism has been interpreted as a confirmation of the hypothesis that syntactic competence is not inaccessible either in Wernicke's or in Broca's aphasia. The Minimal Distance Principle, as a relevant recognition principle, has been studied, and although not confirmed by the scores has been brought to the fore both by the correlations between the variables under study and by the correlations with the concomitant variables of age and level of education.     

Contrasting speech patterns in apraxia of speech and phonemic paraphasia

This study was designed to determine if perceptual phonological analysis would reveal distinctions between patients with apraxia of speech and patients with phonemic paraphasic speech. Test findings from 10 Broca's aphasics with apraxia of speech were compared to findings from 10 paraphasic speakers (5 conduction and 5 Wernicke's aphasics). Several marked differences were revealed. Predominant locus of errors and relative difficulty of different classes of phonemic segments were significant discriminators. There was a nonsignificant trend for substituted phonemes to be further from target phonetically in the paraphasic patients. In addition, the two groups showed certain consistent differences in the types of errors they produced. Apraxic patients produced many errors of transitionalization, while sequencing errors were more typical of the patients with phonemic paraphasia. The findings are interpreted in relation to a neuropsychological model of speech. It is suggested that phonemic paraphasia represents a breakdown mainly in the retrieval of phonological word patterns, while apraxia of speech is characterized predominantly by a disturbance in encoding phonological patterns into appropriate speech movements.     

Comprehension in aphasia: a cross-linguistic study

Broca's aphasics and normal controls were tested to determine relative sparing and impairment of word order, grammatical morphology, and semantic information in a sentence interpretation task. Patients were native speakers of English, German, or Italian, languages that vary drastically in the "cue validity" or information value of these three sources of information. Word order was selectively spared while grammatical morphology was selectively impaired in all three languages. Nevertheless, language-specific patterns of sentence interpretation remained in Broca's aphasics, even within the impaired morphological component, supporting an interpretation in terms of "accessing" rather than a "loss." Testing with Wernicke's aphasics, anomics, and some additional age-matched controls suggested that the selective vulnerability of morphology is not specific to agrammatic patients, at least in this paradigm.     

Analytical competence and language impairment in aphasia

Matched groups of Broca's and Wernicke's aphasics, brain-damaged patients without aphasia and chronic schizophrenics were tested in a nonverbal matching task where the subject had to indicate which of two pictures was more closely linked to a clue picture. Eight additional verbal and nonverbal reference tasks were administered. Both aphasic groups performed worse than brain-damaged controls when the identification of individual attributes or actions shared by clue and referent was required, but were unimpaired when the two had a set of referential-situational associations in common. Factor analyses resulted for both groups in two factors, one of which represents general Language Impairment. For the Broca's aphasics this factor was closely related to general organic deficit as measured by the Trail Making Test; for the Wernicke's aphasics it was associated with tasks which might be considered illustrative of analytical competence in isolating and comparing individual features of objects or concepts.     

Comprehension of sentence structure in anomic and conduction aphasia

Picture-pointing auditory and reading comprehension tests were administered to anomic and conduction aphasics. Subjects responded to active sentences of the present progressive form. The possible errors which a subject could make on these experimental tasks included failure to correctly interpret noun order, number, or lexical meaning. Both groups made significantly more correct responses than error responses. Of their error responses, noun-order errors significantly exceeded number and lexical errors for which no differences were observed. When compared with results previously obtained for agrammatic Broca's aphasics, no differences in the pattern of errors were identified. These results are discussed relative to current theories of syntactic processing and for the mechanisms which account for these syntactic comprehension deficits following aphasia.     

Word-finding abilities of three types of aphasic subjects

Word-finding difficulties are often observed among different types of aphasic patients. This investigation analyzed the word-finding abilities of 30 aphasic subjects (10 Broca's, 10 Wernicke's, and 10 anomic). Forty nouns counterbalanced according to word length and frequency of occurrence in English language usage were used as stimuli and presented through four modalities (oral expression, writing, auditory comprehension, and reading comprehension). It was expected that patterns of word finding abilities would help in the classification of the different types of aphasia. In addition, long words and less frequently occurring words in English language usage should prove more difficult in word-finding ability, regardless of modality. The results of this study found long words and less frequent words were more difficult for aphasic subjects. Among the modalities, long words were significantly harder than short words for the writing modality only. It was also found that semantic errors were the most common errors for all types of aphasic subjects. Broca's subjects produced significantly moreno response errors in oral expression; Wernicke's subjects produced significantly more semantic and phonemic errors in reading comprehension; and, Wernicke's subjects produced significantly more unrelated errors in both oral expression and reading comprehension. Clinical implications were also discussed.The present study was based on a doctoral dissertation completed at the City University of New York in partial fulfillment of the requirements of the doctoral degree in Speech and Hearing Sciences by the first author under the direction of the second author. The authors wish to thank Dr. Louis J. Gerstman for his assistance with the statistical analysis of this research and Dr. Robert Goldfarb for all his helpful suggestions and editorial comments.     

Nasal consonant production in Broca's and Wernicke's aphasics: speech deficits and neuroanatomical correlates

The present study investigated the articulatory implementation deficits of Broca's and Wernicke's aphasics and their potential neuroanatomical correlates. Five Broca's aphasics, two Wernicke's aphasics, and four age-matched normal speakers produced consonant-vowel-(consonant) real word tokens consisting of [m, n] followed by [i, e, a, o, u]. Three acoustic measures were analyzed corresponding to different properties of articulatory implementation: murmur duration (a measure of timing), amplitude of the first harmonic at consonantal release (a measure of articulatory coordination), and murmur amplitude over time (a measure of laryngeal control). Results showed that Broca's aphasics displayed impairments in all of these parameters, whereas Wernicke's aphasics only exhibited greater variability in the production of two of the parameters. The lesion extent data showed that damage in either Broca's area or the insula cortex was not predictive of the severity of the speech output impairment. Instead, lesions in the upper and lower motor face areas and the supplementary motor area resulted in the most severe implementation impairments. For the Wernicke's aphasics, the posterior areas (superior marginal gyrus, parietal, and sensory) appear to be involved in the retrieval and encoding of lexical forms for speech production, resulting in increased variability in speech production.     

The noun-verb problem in Chinese aphasia.

Previous studies have shown that Broca's aphasics experience a selective difficulty with action naming inside or outside of a sentence context. Conversely, it has been suggested that Wernicke's aphasics are particularly impaired in object naming. A number of explanations have been offered to account for this double dissociation, including grammatical accounts according to which the main verb problem in agrammatic Broca's aphasics is viewed as a by-product of their syntactic and/or morphological impairment, due perhaps to the greater morphological load carried by verbs (compared with nouns). In the Chinese language, there are no verb conjugations and no declensions. Hence there is no reason to expect a relationship between morphological impairment and deficits in action naming. We examined comprehension and production of object and action names, outside of a sentence context, in a sample of Chinese-speaking Broca's and Wernicke's aphasics. There was an interaction between patient group and object/action naming, but no corresponding interaction on the comprehension task. We conclude that action-naming deficits in Broca's aphasia (and/or the corresponding sparing of action names in Wernicke's aphasia) cannot be attributed to morphological differences between nouns and verbs. We also found a sublexical variant of the noun/verb dissociation applied to the internal structure of compound words made up of a verbal and a nominal element: Broca's aphasics tended to lexicalize the verbal portion of these words more often than the nominal compound, while Wernicke's showed the opposite pattern. These sublexical effects are difficult to explain in syntactic terms nor do they fit the standard lexical view. A modified lexical account is proposed, emphasizing semantic/conceptual effects in a distributed lexicon.     

The relation between gesture and language in aphasic communication

Effective communication in aphasia depends not only on use of preserved linguistic capacities but also (and perhaps primarily) on the capacity to exploit alternative modalities of communication, such as gesture. To ascertain the capacity of aphasic patients to use gesture in their spontaneous communication, informally structured interviews were conducted with two Wernicke's aphasics and two Broca's aphasics, as well as with four normal controls. The performances of the patient groups were compared on the physical parameters of gesture, the points in the communication where gestures occurred, and several facets of the semantics and pragmatics of gesture. Generally speaking, the gestures of the aphasics closely paralleled their speech output: on most indices, the performance of the Wernicke's aphasics more closely resembled that of the normal controls. Wernicke's aphasics differed from normals in the clarity of their language and gestures: While individual linguistic units were often clear, the relation among units was not. In contrast, the Broca's aphasics equaled or surpassed the normal controls in the clarity of their communications. The results offer little support for the view that aphasic patients spontaneously enhance their communicative efficacy through the use of gesture; these findings can, however, be interpreted as evidence in favor of a “central organizer” which controls critical features of communication, irrespective of the modality of expression.     

Lexical creativity during instances of word-finding difficulty: Broca's vs. Wernicke's aphasia

Lexical innovation--the creation of a word by combining existing morphemes in a novel way (e.g. "map ball" for "globe")--was evaluated as a method for circumventing word-finding difficulty in Broca's and Wernicke's aphasia. Aphasic groups were matched for naming performance and compared to a control group of normal adults matched for age and education. Lexical innovations were collected during the administration of a confrontation naming test, and were then analyzed in terms of the correctness of morpheme combination, semantic accuracy, novelty, and communicative effectiveness. An innovation was considered to be communicatively effective when its intended referent was understood by a naive judge. The lexical innovations of the two aphasic groups were diametrically opposed: as compared to both Broca's aphasics and normal adults, Wernicke's aphasics innovated significantly less often, and their innovations were significantly inferior in terms of: semantic precision, the proper construction of morpheme combination, and communicative effectiveness. This pattern suggests that lack of verbal fluency may be compatible with lexical creativity, while empty logorrheic speech may be an impediment to lexical creativity. Similarly, we conclude that the agrammatism of Broca's asphasia does not interfere with lexical innovation, while the paragrammatism of Wernicke's aphasia does interfere with lexical innovation, thus suggesting that paragrammatism affects morpheme combination at the word level as well as the sentence level.     

The classifier problem in Chinese aphasia

In recent years, research on the relationship between brain organization and language processing has benefited tremendously from cross-linguistic comparisons of language disorders among different types of aphasic patients. Results from these cross-linguistic studies have shown that the same aphasic syndromes often look very different from one language to another, suggesting that language-specific knowledge is largely preserved in Broca's and Wernicke's aphasics. In this paper, Chinese aphasic patients were examined with respect to their (in)ability to use classifiers in a noun phrase. The Chinese language, in addition to its lack of verb conjugation and an absence of noun declension, is exceptional in yet another respect: articles, numerals, and other such modifiers cannot directly precede their associated nouns, there has to be an intervening morpheme called a classifier. The appropriate usage of nominal classifiers is considered to be one of the most difficult aspects of Chinese grammar. Our examination of Chinese aphasic patients revealed two essential points. First, Chinese aphasic patients experience difficulty in the production of nominal classifiers, committing a significant number of errors of omission and/or substitution. Second, two different kinds of substitution errors are observed in Broca's and Wernicke's patients, and the detailed analysis of the difference demands a rethinking of the distinction between agrammatism and paragrammatism. The result adds to a growing body of evidence suggesting that grammar is impaired in fluent as well as nonfluent aphasia.     

Errors resembling semantic paralexias in Spanish-speaking aphasics.

Forty-one Spanish-speaking left-hemisphere-damaged patients were selected and divided into seven groups (transcortical, Broca's aphasia, conduction aphasia, Wernicke's aphasia, anomic aphasia, alexia without agraphia, and global aphasia). A reading battery composed of eight different subtests was given to each patient (reading of letters, reading of syllables, reading of pseudowords, reading of words, reading of sentences, understanding commands, reading and comprehension of texts, and logographic reading). Different types of reading errors were analyzed. Only in the logographic reading subtest were some word-recognition errors found, resembling semantic paralexias. It is proposed that semantic paralexias in English (and other languages) depend upon the partial logographic nature of the reading system. The importance of cross-linguistic analysis of reading errors, taking into account reading system idiosyncracies, is emphasized.