On the preservation of word order in aphasia: cross-linguistic evidence

Studies of language production in English-speaking aphasics (both fluent and nonfluent) generally lead to the conclusion that word order is preserved to a much greater degree than grammatical morphology and/or lexical retrieval. However, because word order is rigidly preserved even in normal English speech, this pattern might reflect nothing more than "the weak link in the chain." Using a constrained production paradigm, we provide evidence showing that canonical sentence order is well preserved in both fluent and nonfluent patients, in Italian and German (languages that permit much more pragmatic word-order variation) as well as English. Patients also retain the ability to order nouns around a preposition, and among Italian patients, access to a high-frequency form of pragmatic word-order variation is also retained. Syntactic difficulties seem to revolve not around loss of ordering principles, but (1) reduction in syntactic complexity, (2) overuse of canonical word order as a "safe harbor," (3) blend errors in which a form appears in legal but semantically incorrect position, and (4) abandonment of the effort to produce a complete sentence under stressful conditions. We offer a redefinition of syntactic impairment as a problem in the access of phrase structure types, resulting in a preference for higher frequency forms. Parallels between lexical retrieval and phrase structure retrieval suggest that similar mechanisms may be at work in both cases.     

Picture-naming in aphasia

The distribution of picture-naming errors for Broca's aphasics (n = 9), Wernicke's aphasics (n = 9), conduction aphasics (n = 9), frontal anomics (n = 7), and posterior anomics (n = 9) was examined to determine the diagnostic power of error types in picture-naming. Negated responses were associated with Broca's aphasia, whole-part errors ("hose" for nozzle) were associated with frontal anomia, and poor phonemic cuing was associated with Wernicke's aphasia. In addition, the relative distribution of the three most prominent naming errors-phonemic errors, semantic errors, and multiword circumlocutions-tended to distinguish the two anomic subgroups from the other aphasia subgroups. Anomic aphasics produced the fewest phonemic errors and the most multiword circumlocutions; this pattern suggests minimal word-production difficulty in anomic aphasia relative to the other aphasia syndromes. Despite such group differences, the overall picture indicates that there is considerable similarity among aphasia syndromes in terms of picture-naming behavior.     

Frontal-opercular aphasia.

The standard nomenclature divides nonfluent aphasic syndromes with relatively spared comprehension into Broca's aphasia and transcortical motor aphasia. We report on a patient with a persistent nonfluent aphasia from a discrete, primarily cortical, frontal-opercular lesion who had impaired syntax but intact repetition and, therefore, did not conform to the traditional classification. Based on this patient's behavior and a review of other cases, we have divided the nonfluent aphasias with intact comprehension into five disorders. (1) Verbal akinesia-exhibiting diminished intention or drive to speak and associated with medial frontal lesions (supplementary motor area and cingulate gyrus) or with lesions damaging the efferent projections from these areas. (2) Disorders of syntax-telegraphic and agrammatic utterances that may be associated with dominant pars opercularis lesions. (3) Phonemic disintegration-a failure to correctly produce phonemes, which may be associated with injury to the opercular primary motor cortex or efferent projections from this area. (4) Defects of lexical access-patients who struggle to find words and are impaired at timed word-generation tasks. Defects of lexical access may be associated with lesions of the pars triangularis and adjacent prefrontal cortex. (5) Mixed defects. According to this model, the traditional patient with Broca's aphasia would exhibit disorders of syntax, phonemic disintegration, and defects of lexical access, whereas the traditional patient with transcortical motor aphasia would have verbal akinesia or defects of lexical access or both. Our patient had defects of lexical access and syntax, but only mild symptoms of phonemic disintegration, suggesting that his opercular primary motor cortex was relatively intact. Our patient's ability to repeat normally while his propositional speech remained telegraphic suggests that different neural mechanisms subserve these functions.     

Comprehending homographs in aphasia

This study assessed 13 aphasic subjects' knowledge of the multiple meanings of homographs. The results indicated that the various meanings were less available to aphasic subjects than to normal subjects. In addition, specific meanings became less available as they became less typical although the number of meanings associated with a homograph did not influence performance. Aphasia type also did not influence performance. Performance on the experimental test was significantly correlated with auditory comprehension level and picture naming ability. The results were related to recent findings on semantic organization in aphasia.     

Numerical taxonomy of aphasia

Two hundred consecutively seen aphasics, 142 of them with infarcts, were examined by tests of fluency, comprehension, repetition, naming, and information content. The language scores were subjected to a minimum variance clustering algorithm separately for the total and for the infarct groups. The latter generated 10 clusters on a dendrogram. Attribute analysis of each cluster provided a clinically meaningful profile of language performance for these groups. The degree of correlation of most computer generated clusters with clinically recognized groups was high, and the homogeneity of some of the clusters is striking. An exception appears to be “conduction aphasia,” which is bimodally distributed. One of these clusters, with high fluency and low comprehension scores, was renamed “afferent conduction” aphasia, and the other, with lower fluency and higher comprehension, was renamed “efferent conduction” aphasia. The Principal Components Analysis was used to evaluate the discriminatory value of language characteristics, and the Nearest Neighbor Network Analysis was used to evaluate the significance of clustering. The dendrogram for all aphasics showed a less specific and less homogenous six clusters.     

Text comprehension in aphasia

The semantic and pragmatic strategies in the comprehension of spoken texts are investigated in four subgroups of aphasic patients and in normal and brain-damaged controls. Short texts of similar linguistic structure were read to the subjects, who were required to choose the picture, from a multiple choice set of five, that was appropriate to the story. Besides a picture showing the main event of the story, one picture depicted the literal sense of a metaphorical comment, and the others misrepresented semantic functions expressed in the text. With respect to these types of responses, both aphasics and controls exhibited the same pattern of reaction. It is concluded that the redundancy of texts makes up for the difficulties aphasics have in comprehending isolated words and sentences.     

Phonemic imperception in aphasia

This study investigated characteristics of 14 aphasics with impaired phoneme discrimination identified from a population of 100 patients with left hemisphere lesions. All patients with impaired phoneme discrimination were significantly impaired in aural comprehension, but many showed intact sound recognition and some showed normal reading comprehension. Defects in phoneme discrimination were typically seen in the acute stage of aphasia resulting from stroke; and in most instances, defects in phoneme discrimination were no longer apparent 4 months postonset. All patients who recovered normal phoneme discrimination also made significant improvement in aural comprehension. The findings support the concept that some aural comprehension defects result from a specific disturbance in phoneme discrimination.     

Crossed aphasia in multilinguals

Reports of crossed aphasia in single case studies of bilinguals have led to incidence studies of crossed aphasia among larger groups of stroke patients. Among a few others, studies carried out in India (K. R. Nair & Virmani, 1973 Indian Journal of Medical Research, 61, 9; P. Chary, 1986, In Language processing in bilinguals: Psycholinguistic and neuropsychological perspectives) have lent support to the notion of a higher incidence of crossed aphasia among bi- and multilinguals and form major citations in support of the hypothesis that bilingualism could lead to a greater bilateral cerebral representation of languages. This paper reports on the incidence of crossed aphasia in a large unselected population of stroke patients in monolingual and multilingual speakers of South India, which is in agreement with the previous reports of a higher incidence of crossed aphasia in multilinguals. However, along with this high incidence of crossed aphasia a low incidence of sinistrality was also seen. In order to confirm these findings and their significance two further studies were carried out-an incidence study of crossed aphasia in a population of mono- and multilingual aphasics and an incidence study of hand dominance in a normal population. The results and their significance to the issue of crossed aphasia in multilinguals are presented.     

Communicative gestures in aphasia

Gestural communications of 10 mild and moderate aphasics and five controls were examined in two conditions: Face-to-face informal dyadic conversation and restricted visual access between speaker and listener. Gestural production was significantly reduced with restriction of visual access, supporting the posited communicative function of the hand and arm gestures investigated in this study. No differences were found between aphasic and control subjects in the rate of gestural communication in the natural condition of face-to-face interaction. Moderate aphasics, however, were found to produce proportionally fewer of the complex semantic modifying and relational communicative gestures and more nonspecific, nonconsensually shared, unclear gestures. Gestural complexity was significantly negatively correlated with measures of linguistic impairment for the aphasics. The relationship between the frequency and complexity of communicative gestures and concurrent verbalizations was also examined. The findings of this study provide confirmation for the view that there is an identifiable class of gestures utilized by aphasics for communication, aphasics are impaired in their gestural communicative competence in natural conditions of communication, and the quality of aphasics' gestural communications parallels changes in their verbal communication patterns.     

Phonological transformations in conduction aphasia

Different explanations and subtypes of conduction aphasia are analyzed. Characteristics of literal paraphasias in parietal-insular conduction aphasia are discussed, emphasizing that paraphasias in conduction aphasia are articulatory-based (articulatory literal paraphasias) and due mainly to phoneme substitutions and phoneme deletions; they result basically in switches in phoneme manner and place of articulation. Similarities between errors in ideomotor apraxia and conduction aphasia language deficits are presented. It is proposed that language deviations (in oral as in written language) in conduction aphasia can be understood as a segmentary apraxia of speech.     

Hemiplegic writing in severe aphasia

Three patients with severe aphasia and right hemiplegia are described who could write to dictation with the right arm using a limb prosthesis though agraphic with the "intact" left hand. The phenomenon of "hemiplegic writing" is explained as an access to submerged or preprocessing levels in language and action structure, through the use of older proximal motor systems. This interpretation has implications for our understanding of language and brain function, as well as for approaches to the treatment of patients with severe language disorders.     

Selective word-learning deficits in aphasia

The purpose of this study was to determine whether patients with focal brain damage can learn anything about a new word, and if so, whether selected aspects of the new word are acquired depending on the nature of the patient's language processing deficit. In the context of drawing pictures with a number of felt pens identical in all respects except color, agrammatic Broca's aphasics and fluent aphasics were exposed to the new word "bice," an adjective referring to the dark green portion of the color spectrum. Our findings revealed that brain-damaged patients can engage in lexical acquisition, but Broca's aphasics and fluent aphasics apparently learn about different aspects of the new word. Specifically, on successive exposures to "bice," both Broca's aphasics and fluent aphasics exhibit progressively more accurate hypotheses for identifying a bice-colored object. During subsequent assessments, agrammatic aphasics reveal on a metalinguistic judgment task their significant difficulty appreciating the grammatical form class of "bice"; on an object classification task, fluent aphasics are significantly impaired in their classification of bice-colored objects as "bice." Taken together, these unique word-learning profiles reinforce earlier observation on the selective nature of language processing deficits after focal left-hemisphere insult, and support the claim that separate language processing devices may be selectively compromised in different groups of aphasics. The relationship between syntactic and lexical semantic processing is discussed.     

Space and the parietal cortex

Current views of the parietal cortex have difficulty accommodating the human inferior parietal lobe (IPL) within a simple dorsal versus ventral stream dichotomy. In humans, lesions of the right IPL often lead to syndromes such as hemispatial neglect that are seemingly in accord with the proposal that this region has a crucial role in spatial processing. However, recent imaging and lesion studies have revealed that inferior parietal regions have non-spatial functions, such as in sustaining attention, detecting salient events embedded in a sequence of events and controlling attention over time. Here, we review these findings and show that spatial processes and the visual guidance of action are only part of the repertoire of parietal functions. Although sub-regions in the human superior parietal lobe and intraparietal sulcus contribute to vision-for-action and spatial functions, more inferior parietal regions have distinctly non-spatial attributes that are neither conventionally 'dorsal' nor conventionally 'ventral' in nature.