Syntactic priming effects in aphasia: an investigation of local syntactic dependencies

This study explored on-line processing of local syntactic dependencies in normal subjects and in Broca's and Wernicke's aphasics using a lexical decision paradigm. In addition, subjects performed a grammatically judgement task on the real word pairs used in the lexical decision tasks. Results of two experiments for normal subjects indicated different syntactic priming effects as a function of the type of local syntactic dependency. Word pairs that formed a single constituent phrase, i.e., a verb phrase, showed both facilitory and inhibitory effects, whereas word pairs that reflected local syntactic dependencies across a phrase boundary, i.e., pronoun verb, showed only inhibitory effects. Broca's aphasics failed to show facilitory effects when presented with word pairs forming a single constituent phrase but, similar to normals, did show inhibition when presented with word pairs that reflected local syntactic dependencies across a phrase boundary. In contrast, Wernicke's aphasics failed to show inhibitory effects in both experiments. The implications of these results for theories of language processing deficits in aphasia are considered.     

Processing local transitions versus long-distance syntactic hierarchies

A recent study by Fitch and Hauser reported that finite-state grammars can be learned by non-human primates, whereas phrase-structure grammars cannot. Humans, by contrast, learn both grammars easily. This species difference is taken as the critical juncture in the evolution of the human language faculty. Given the far-reaching relevance of this conclusion, the question arises as to whether the distinction between these two types of grammars finds its reflection in different neural systems within the human brain.     

Speech prosody in Broca's aphasia

Because speech prosody is thought to be impaired in Broca's aphasia, we conducted three experiments using Broca's aphasics and nonneurological control subjects in order to determine to what extent this statement is accurate. Using three acoustic measures of speech prosody—sentence-final fundamental frequency (F₀) fall, F₀ declination, and sentence-final lengthening—we found that some aspects of prosody were spared while others were abnormal. All Broca's aphasics, regardless of degree of impairment, exhibited sentence-final F₀ fall. F₀ declination was present in simple sentences but was absent over longer domains; moreover, the amount of declination was correlated with the degree of linguistic impairment. Sentence-final lengthening was clearly absent in Broca's aphasia; in fact, sentence-terminal words were actually shorter than their sentence-initial and medial counterparts.     

On-line syntactic processing in aphasia: studies with auditory moving window presentation

Twenty-eight aphasic patients with left hemisphere strokes and matched control subjects were tested on an auditory moving windows task in which successive phrases of a sentence were presented in response to subjects' self-paced button presses and subjects made timed judgments regarding the plausibility of each sentence. Pairs of sentences were presented that differed in syntactic complexity. Patients made more errors and/or took longer in making the plausibility judgments than controls, and were more affected than controls by the syntactic complexity of a sentence in these judgments. Normal subjects showed effects of syntactic structure in self-paced listening. On-line syntactic effects differed in patients as a function of their comprehension level. High-performing patients showed the same effects as normal control subjects; low performing patients did not show the same effects of syntactic structure. On-line syntactic effects also differed in patients as a function of their clinical diagnosis. Broca's aphasic patients' on-line performances suggested that they were not processing complex syntactic structures on-line, while fluent aphasics' performances suggested that their comprehension impairment occurred after on-line processing was accomplished. The results indicate that many aphasic patients retain their ability to process syntactic structure on-line, and that different groups of patients with syntactic comprehension disorders show different patterns of on-line syntactic processing.     

Comprehension of passives in Broca's aphasia

Drai and Grodzinsky have statistically analyzed a large corpus of data on the comprehension of passives by patients with Broca's aphasia. The data come, according to Drai and Grodzinsky, from binary choice tasks. Among the languages that are analyzed are Dutch and German. Drai and Grodzinsky argue that Dutch and German speaking Broca patients should be relatively good (that is, perform above chance) on comprehension of passive sentences, since in Dutch and German passives the relative order of the object and lexical verb is the underlying order and hence no movement takes place. We will demonstrate that both their linguistic arguments and their selection of Dutch data are invalid.     

Object scrambling in Dutch Broca's aphasia

This study focuses on the production of sentences in which objects have been moved without a change in the order of the thematic roles. In Dutch, the basic word order is subject-adverb-object-verb. The object can be moved over the adverb; this is called object scrambling. The difference between the two word orders is pragmatic in nature: in the basic word order the focus is on the object, in the scrambled order, the focus is on the adverb. The aim of the present study is to evaluate if production of constructions with moved objects is impaired in Broca's aphasia and if so, whether that is for syntactic or pragmatic reasons. The results show that for individuals with Broca's aphasia, sentences with the scrambled word order are more difficult to produce than sentences with the basic word order, even if the scrambled order results in a pragmatically more acceptable sentence. This falsifies several theories of production in Broca's aphasia and shows an interesting parallel to the performance on comprehension tasks.     

Reconstructive retrieval deficits in Broca's aphasia

Anterior aphasic patients' ability to utilize the phonemic and/or semantic features of verbal material for retention purposes was investigated. In the first experiment, patients were asked to either detect word repetitions, phoneme repetitions, or rhymes in a list of items. The aphasics performed well on word and phoneme repetition detection but below both normals and amnesic Korsakoffs on rhyme detection. In the second experiment the patients were instructed to analyze either the physical, phonemic, or semantic features of words they were later asked to recognize. Aphasics were differentially affected (as were normals) by these instructions: semantic feature analysis resulted in the best performance, followed by phonemic feature analysis. It was concluded that anterior aphasics can analyze, recirculate, and even store the phonemic features of words, but find difficulty in reconstructing the originally presented item from these features.     

Verb and auxiliary movement in agrammatic Broca's aphasia

Verb production in agrammatic Broca's aphasia has repeatedly been shown to be impaired by a number of investigators. Not only is the number of verbs produced often significantly reduced, but verb inflections and auxiliaries are often omitted as well (e.g., Bastiaanse, Jonkers, & Moltmaker-Osinga, 1996; Saffran, Berndt, & Schwartz, 1989; Thompson, Shapiro, Li, &Schendel, 1994, 1997). It has been suggested that these problems are, in part, caused by the fact that finite verbs need to be moved from their base-generated position to inflectional nodes in the syntactic tree (e.g., Bastiaanse & Van Zonneveld, 1998). Others have suggested that production deficits in agrammatism can be predicted based on the position that certain structures take in the syntactic tree (Friedmann & Grodzinsky, 1997; Hagiwara, 1995). If the former theory is correct, several predictions can be made. First of all, the discrepancy between production of finite verbs in the matrix and embedded clause that has been found for Dutch (Bastiaanse & Van Zonneveld, 1998) should not be observed in English, since the word order of the matrix and embedded clause are the same in the latter language. Second, if verb movement (including movement of auxiliaries) is problematic for speakers with agrammatic aphasia, then a hierarchy in the production of auxiliaries in yes/no questions, auxiliaries, and finite verbs in declarative sentences in English would be expected, since the former has been moved and the two latter are in base-generated position. In the present paper, these hypotheses were tested in a cross-linguistic study of Dutch and English. Results showed the position in the syntactic tree does not predict deficit patterns; rather the critical factor appears to relate to whether or not verb or auxiliary movement is required.     

Lexical structure in parsing long-distance dependencies

We review a series of experiments investigating lexical influences in parsing sentences with long-distance dependencies. We report three primary results. First, gaps are posited and filled immediately following verbs that are typically used transitively, even when the filler is an implausible object of the verb. However, gaps are not posited after verbs that are typically used intransitively. Second, plausibility determines whether or not a filler is treated as the object of a verb when the verb is typically used with both a direct object and an infinitive complement. Finally, verb control information is used immediately in determining which noun phrase will be interpreted as the understood subject of an infinitive complement.     

Broca's aphasia, verbs and the mental lexicon

Verb production is notoriously difficult for individuals with Broca's aphasia, both at the word and at the sentence level. An intriguing question is at which level in the speech production these problems arise. The aim of the present study is to identify the functional locus of the impairment that results in verb production deficits in Broca's aphasia. Levelt's (1989) model is used as a theoretical framework for this study. Two experiments have been conducted, one on verb movement and one on verbs with alternating transitivity. The results suggest that the functional impairment in Broca's aphasia should be located in Levelt's "grammatical encoder."     

Dysprosody in Broca's aphasia: a case study

A detailed acoustic analysis of timing, intensity, and fundamental frequency (F0) at different levels of linguistic structure was conducted on the speech output of a Broca's aphasic who was a native speaker of Thai. Timing was measured with respect to syllables, phrases, and sentences in connected speech. Intensity variation at the sentence level was measured in connected speech. F0 variation associated with the five Thai tones was measured in both isolated words and connected speech. Results indicated that timing was differentially impaired depending upon complexity of articulatory gesture and size of the linguistic structure. Timing, as well as intensity, was aberrant at the sentence level. In contrast, F0 contours of the five tones were spared at all levels of linguistic structure. Findings are interpreted to support the view that dysprosody in Broca's aphasia is more applicable to speech timing than to F0.     

Deficits in thematic integration processes in Broca's and Wernicke's aphasia

This study investigated how normal subjects and Broca's and Wernicke's aphasics integrate thematic information incrementally using syntax, lexical-semantics, and pragmatics in a simple active declarative sentence. Three priming experiments were conducted using an auditory lexical decision task in which subjects made a lexical decision on a 'target' (the last word of each sentence) preceded by a 'prime' (a subject noun phrase and verb). The presence and magnitude of priming was compared to a baseline condition in which non-words systematically replaced real word primes. Normal subjects showed evidence for combinatorial thematics by exhibiting significant and larger amounts of thematic priming in the condition where two real words were present in the prime than in the conditions in which only one real word was present in the prime. Additionally, normal subjects showed sensitivity to both syntactic structures and pragmatics. In contrast, Broca's patients did not show significant priming for any condition nor did they show a difference in the magnitude of priming among the conditions. Nonetheless, they showed sensitivity to pragmatics. Wernicke's patients showed significant priming for all conditions, but did not show differences in the magnitude of priming among the conditions. However, they showed sensitivity to sentence grammaticality and pragmatics. The distinct patterns of performance of Broca's and Wernicke's aphasics are discussed in terms of the nature of their impairments in the processes of combinatorial thematics.     

A crosslinguistic study of grammaticality judgments in Broca's aphasia

Crosslinguistic studies of sentence comprehension and production in Broca's aphasia have yielded two complementary findings: (1) grammatical morphology appears to be more impaired than word order principles in every language studied, but (2) the degree to which grammatical morphology is retained by aphasic patients depends upon the "strength" or importance of those morphemes in the patient's premorbid language. In an earlier study comparing violations of word order and agreement, we found that English-speaking Broca's aphasics showed greater sensitivity to errors of ordering than to errors of agreement, providing further evidence for the selective vulnerability of morphology. However, because English is a rigid word order language with a relatively weak inflectional system, it could be argued that word order is resilient to brain damage because it is the strongest source of information in this language. The present study compared the performance of English-speaking Broca's aphasics and normal controls with their Italian counterparts in the same grammaticality judgment experiment. Four predictions relating to our previous work were confirmed. (1) Italian aphasics, like their English-speaking counterparts, showed general preservation of grammatical knowledge and (2) they were able to use this knowledge in an "on-line" fashion. (3) Within each language, Broca's aphasics showed greater impairment in their ability to recognize errors of morphological selection (i.e., agreement) compared with errors made by moving the same words to an incorrect position downstream. Nevertheless (4), crosslinguistic differences observed in previous studies of comprehension and production were also observed in this grammaticality judgment task: a processing advantage for agreement errors in Italian normals and aphasics, and a processing advantage for ordering errors in English normals and aphasics.     

The existence of comprehension patterns in Broca's aphasia.

Berndt and Caramazza (1999) claim that Grodzinsky, Pi?ango, Zurif, and Drai (1999) were able to show a canonical-noncanonical difference (e.g., actives vs. passives) in the comprehension of Broca's aphasic patients only because of a patient selection bias. We show that the canonical-noncanonical comprehension pattern exists apart from any such bias, and that this pattern bears importantly on our understanding of the neuroanatomical organization of comprehension capacity at the sentence level.     

Speech sound errors in patients with conduction and Broca's aphasia

Speech sound errors exhibited by three conduction and three Broca's aphasic patients on naming and word-repetition tasks were subjected to phonemic and subphonemic analyses. In the conduction aphasic patients, errors occurred equally often on consonants and vowels in both the naming and word-repetition tasks, while in the Broca's aphasic patients errors occurred selectively on consonants. Transposition errors occurred almost as often as substitution errors in the conduction aphasic patients, while substitution errors constituted the majority of errors in the Broca's aphasic patients. The Broca's aphasic patients, as compared to the conduction aphasic patients, exhibited a markedly higher number of substitution errors occurring between phonemes separated by a single subphonemic feature on the naming task. On the basis of these findings, it was hypothesized that the differences in the error patterns of the two types of aphasia reflected differences in the underlying mechanisms of the impairment in each type.     

Phoneme errors in Broca's aphasia: three Finnish cases

The phonemic errors of three Finnish Broca's aphasics were analyzed according to various phonological features, frequency of segments, syllable, word, and stress positions, as well as for the phonotactic structure of the uncanonical products. It was found, e.g., that the distance between the syntagmatic error and its source could not be satisfactorily counted by phonemes, since the syllable had to be taken into account also in pathological Finnish. As regards the paradigmatic dimension of the errors, the number of incorrect features is even here in reverse relation to the frequency of the erroneous phonemes. Moreover, it was found that pure quantity errors and vowel harmony deviations are infrequent in the speech of Finnish Broca's aphasics.     

Proper and common nouns: form class judgments in Broca's aphasia

Studies of agrammatic Broca's aphasics' comprehension of sentences containing articles have demonstrated profound deficits. It has not been clear whether the impairments are due to an inability to isolate the article in the stream of speech, or to difficulty in the construction and/or interpretation of various syntactic, semantic, or pragmatic levels of representation. This paper reports three experiments on Broca's aphasics' ability to distinguish between common nouns (e.g., "a rose") and proper nouns (e.g., "Rose"). This grammatical form class decision is signaled by the presence or absence of an article, and is represented at the lexical node level of linguistic analysis. The three experiments demonstrated that Broca's aphasics point to pictures representing classes of objects when asked to point to "the X" and point to pictures representing unique individuals when asked to point to "X". Thus, they were shown to be able to use the presence or absence of an article to determine lexical category. Their performance was especially accurate in an oral language context which was highly redundant and in a written language context where patients themselves could control the rate of information flow. They were quantitatively impaired, relative to controls, in a third study, which made higher information processing demands. Moreover, in this third study nonsense syllables preceding the noun which are phonologically similar to a known article were much more likely to evoke the misclassification of its noun as common than were phonologically distinct nonsense syllables. These data indicate that Broca's aphasics indeed have some difficulty isolating the article in the stream of speech. Nevertheless, detailed analyses of aphasics' performance revealed their ability to distinguish between common nouns and proper nouns even under these demanding conditions. Taken together, the three studies show that insofar as agrammatic patients are able to keep track of the presence or absence of articles, they can make a grammatical decision at the lexical node level of linguistic analysis. We conclude, then, that agrammatic Broca's aphasics are particularly impaired in the use of articles to construct and/or interpret phrasal constituents.