Accessibility of case and gender contrasts for agent--object assignment in Broca's aphasics and fluent anomics

Yugoslav agrammatic Broca's aphasics, fluent anomics, and control subjects were tested for comprehension of agent-object relations in a series of simple Serbo-Croatian sentences in the conversational past tense, consisting of two nouns and a transitive action verb. The availability of two closed class cues--case contrasts and gender contrasts--as well as the availability of an open class lexical cue--animacy contrasts--was varied across sentences. An analysis of subjects' agent-object assignments yielded the following results: Both Broca's aphasics and fluent anomics showed a selective impairment in sensitivity to closed class morphology, although anomics were considerably less impaired than Broca's aphasics. This finding was interpreted as evidence for a non-syndrome-dependent vulnerability of abilities to process closed class morphology for comprehension. In addition, the pattern of agent-object assignments for Broca's aphasics revealed that the degree to which they were able to access the two closed class cues depended on a convergence of the various cues to agent-object relations. In particular, a convergence of case and gender contrasts had an interactive effect on Broca's responses: Gender agreement cues were accessed only in the presence of convergent case contrasts. Conversely, sensitivity to case contrasts was dramatically heightened in the presence of convergent gender contrasts. These results were consistent with a view that the two cues function as intrasentential "primes" or "retrieval cues" for one another.     

Aphasic adults' use of heuristic and structural linguistic cues for sentence analysis

Eight aphasic adults with relatively preserved auditory comprehension and 12 normal adults were tested for their ability to analyze sentences in which the functional relations between the verb and nouns was either directly reflected by word order expectancies, or marked by a functor or non-NVN word order. The subjects' task was to designate the agent of each sentence. Results indicated that aphasics utilize word order expectancies but are impaired in their ability to exploit functors and particularly, word order markers for sentence analysis. Results are discussed in terms of aphasics' use of heuristic versus structural linguistic cues for interpreting sentences.     

Dissociation of algorithmic and heuristic processes in language comprehension: Evidence from aphasia

Three groups of aphasic patients, Broca's, Conduction, and Wernicke's, and a nonaphasic patients control group were tested for comprehension of object-relative center-embedded sentences. The sentences were of three types: sentences in which semantic constraints between words allowed the subjects to assign a correct semantic reading of the sentence without decoding the syntax, sentences in which semantic constraints were relaxed and for which a correct reading was only possible with knowledge of syntactic relationships among words, and sentences which described highly improbable events. The subjects' task was to choose which of two pictures captured the meaning expressed in the sentence. Broca's and Conduction aphasics performed near perfectly on sentences where they could use semantic information. Their performance dropped to chance when they had to use syntactic information. These results support a neuropsychological dissociation of heuristic and algorithmic processes based primarily, though not exclusively, on semantic and syntactic information, respectively.     

Processing passive sentences in aphasia: deficits and strategies

Broca's and Wernicke's aphasics' ability to process passive sentences in the absence of semantic cues was investigated in an experiment which varies syntactic complexity and word order. The results indicate that Broca and Wernicke patients use different strategies for sentence comprehension. Wernicke patients use rather general strategies for interpretation, which assign syntactic function according to sequential arrangements of words. Broca's aphasics, by contrast, base their interpretation on specific structural elements of the sentence's surface form, without, however, being able to exploit the full syntactic information of these elements. The different strategies are interpreted to reflect differential underlying deficits.     

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.     

The effect of pictorial context on sentence memory in Broca's and Wernicke's aphasia

Eighteen aphasic patients (8 Broca's and 10 Wernicke's aphasics), 11 right hemisphere damaged patients and 12 normal subjects were tested to assess the effect of pictorial context on verbal memory with a sentence recognition task. The subjects were read aloud a stimulus sentence describing a simple event and simultaneously shown a picture congruent or incongruent with the sentence. Immediately following or after an interval of 30 sec, the subjects were read aloud a second sentence and asked to judge whether this sentence was the same or different from the stimulus sentence. The results indicated that verbal memory was better retained in supportive situations than in distracting situations, and that this contextual effect was greater in aphasic patients than in any of the other groups. Verbal memory declined rapidly after an interval in aphasic patients, but not in normal subjects. The Broca's and the Wernicke's aphasics demonstrated different performance patterns when semantic analysis of sentences was critical.     

Sentence comprehension in aphasia in two clear case-marking languages

Studies of aphasia in Indo-European languages point to a selective vulnerability of morphological case marking in sentence comprehension. However, in case-marking languages such as German and Serbo-Croatian, the use of case marking to express formal grammatical gender diminishes the clarity of grammatical role marking. In Hungarian and Turkish, there are simple and reliable markings for the direct object. These markings are not linked to grammatical gender. Compared to Hungarian, the Turkish accusative marking is somewhat lower in availability, but somewhat higher in detectability. The processing of these cues by aphasics was tested using the design of MacWhinney, Pléh, and Bates (1985. Cognitive Psychology, 17, 178-209). Simple sentences with two nouns and one transitive verb were read to Broca's and Wernicke's aphasics, anomics, and control subjects in both Turkey and Hungary. The main effect of case marking was extremely strong. However, this was not true for all groups. The aphasics used the case cue far less than the normals, with the Hungarian Wernicke's group showing the greatest loss. Word order variations were largely ignored in all groups whenever the case-marking cue was present. When case marking was absent, Turkish subjects had a clear SOV interpretation for NNV sentences and Hungarians had a clear SVO interpretation for NVN sentences, in accord with basic patterns in their languages. When there was a contrast between the animacy of the two nouns, subjects choose the animate nouns significantly more often. The effect of animacy was particularly strong in Turkish, in accord with basic facts of Turkish grammar. In Hungarian, VNN sentences without case marking were interpreted as VOS when the first noun was inanimate. In Turkish, VNN sentences without case marking were often interpreted as VSO. In general, the aphasic subjects showed a clear preservation of virtually all aspects of their native languages, albeit in a much noisier form. Despite the high reliability of the case-marking cue, it was damaged more than the word order cue in English subjects. The near-chance processing of the case cue by the Wernicke's aphasics in Hungarian can probably be attributed to the relatively greater difficulty involved in detecting the Hungarian accusative suffix.     

Part of speech and phonological form implied in written-word comprehension: Evidence from homograph disambiguation by normal and aphasic subjects

A sentence construction experiment examining the effect of part of speech and phonological form in written-word comprehension is reported. Normal and aphasic subjects had to write sentences incorporating a given word pair, one word was a homograph (e.g., “bank”) whose meaning was context-biased by the other (e.g., “money”/“river”). The effect of three psycholinguistic factors on subjects' performance was questioned: (i) The relative frequency of one meaning of the homograph as compared to the other meaning; (ii) The lexical/syntactic ambiguity (“ball”/“can”); (iii) The same/different phonological forms of the two meanings (“fair”/“bass”). The results are discussed in the framework of a model in which multiple special-purpose procedures are involved in normal processing, some of them being differentially impaired by brain disease in Broca's and Wernicke's aphasics.     

Reading and listening comprehension in Broca's aphasia: Lexical versus syntactical errors

Ten agrammatic Broca's aphasics were presented with a series of four picture plates together with a spoken or written sentence stimulus. All sentence stimuli were of the structure, the + N + is/are + V + ing + the + N. The four pictures on each stimulus plate represented (a) the correct response, (b) a reversal of the stimulus sentence subject and object, (c) a change in the number of the subject of the stimulus sentence, and (d) a change in one of the major lexical items of the stimulus sentence. Subjects selected the correct picture most often. When they erred, they usually selected a subject-object reversal. Number errors were less frequent, and the patients seldom selected a change in major lexical item. This pattern occurred with both written and spoken sentences. These results were interpreted as reflecting the dependence of agrammatic Broca's aphasics on the semantic interpretation of the lexicon for decoding sentences in the face of deficits in syntactical-grammatical interpretation, irrespective of comprehension modality.     

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.     

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.     

Some aspects of language comprehension in anterior aphasia

The competency of language comprehension was evaluated in three groups: anterior aphasics, posterior aphasics, and normal control subjects. Test material was divided into two sentence groups (Fill in the Blank and True/False) emphasizing either (1) semantic, “real world,” identity words or (2) syntactic, relational words, and one paragraph interpretation task. Matching auditory and visual (written) presentations were given. The control subjects performed almost flawlessly but many errors were made by each aphasia group. Qualitative study revealed a marked difference in the comprehension problem of the two groups. The anterior aphasic group performed well on semantically weighted sentences but made errors on syntactically weighted material, regardless of mode of presentation. In contrast, the posterior aphasics made almost the same number of errors on both types of material, regardless of mode of presentation. These findings support the concept of defective language comprehension in anterior aphasia and further suggest that the defect centers on the syntactical structures which are also poorly handled in expressive output.     

Speed of Lexical Activation in Nonfluent Broca''s Aphasia and Fluent Wernicke''s Aphasia

Rapid, automatic access to lexical/semantic knowledge is critical in supporting the tight temporal constraints of on-line sentence comprehension. Based on findings of “abnormal” lexical priming in nonfluent aphasics, the question of disrupted automatic lexical activation has been the focus of many recent efforts to understand their impaired sentence comprehension capabilities. The picture that emerges from this literature is, however, unclear. Nonfluent Broca's aphasic patients showinconsistent,notabsent,lexical priming, and there is little consensus about the conditions under which they do and do not prime. The most parsimonious explanation for the variable findings from priming studies to date is that the primary disturbance in Broca's lexical activation has something to do withspeedof activation. Broca's aphasic patients prime when sufficient time is allowed for activation to spread among associates. To examine this “slowed activation” hypothesis, the time course of lexical activation was examined using a list priming paradigm. Temporal delays between successive words ranged from 300 to 2100 msec. One nonfluent Broca's aphasic patient and one fluent Wernicke's patient were tested. Both patients displayed abnormal priming patterns, though of different sorts. In contrast to elderly subjects, who prime at relatively short interstimulus intervals (ISIs) beginning at 500 msec, the Broca's aphasic subject showed reliable automatic priming but only at a long ISI of 1500 msec. That is, this subject retained the ability to access lexical information automatically if allowed sufficient time to do so, a finding that may help explain disrupted comprehension of normally rapid conversational speech. The Wernicke's aphasic subject, in contrast, showed normally rapid initial activation but continued to show priming over an abnormally long range of delays, from 300 msec through 1100 msec. This protracted priming suggests failure to dampen activation and might explain the semantic confusion exhibited by fluent Wernicke's patients.     

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.     

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.     

Effect of lexical cues on the production of active and passive sentences in Broca's and Wernicke's aphasia

This study compared the sentence production abilities of individuals with Broca's and Wernicke's aphasia in an attempt to explore the extent to which impaired lexical retrieval impedes sentence production. The ability to produce active and passive reversible and non-reversible sentences was examined when varying amounts of lexical information was provided. The results showed that both Wernicke's and Broca's aphasic individuals were impaired in passive sentence production and that these difficulties were not overcome when lexical cues (the relevant nouns and uninflected verb) were provided. However when auxiliary and past tense morphemes were provided along with the verb stem, production of passive sentences improved drastically for both groups. Analysis of error patterns, however, revealed differences between the two groups, suggesting that Broca's aphasic subjects may find passive sentences difficult due to problems with retrieving the relevant grammatical morphemes. Subjects with Wernicke's aphasia may have been unable to automatically access the passive sentence structure.     

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.     

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.     

Syntactic and semantic contributions to sentence comprehension in agrammatism

Five aphasic subjects, who demonstrated agrammatic speech, and eight control subjects were presented with a sentence-picture matching task in which the factors of syntactic complexity, semantic reversibility, and sentence plausibility were independently varied. A subset of the sentences was patterned after that presented by A. Caramazza and E. Zurif (1976, Brain and Language, 5, 572-583) who concluded that Broca's aphasics rely on semantic constraints instead of syntactic information for sentence comprehension. Our aphasic subjects showed the same pattern of performance on this subset of sentences. However, the results from the full set of sentence materials we tested show that the aphasic subjects could perform some sentence level syntactic analyses, even when syntactic information conflicted with semantic constraints. The aphasic subjects correctly interpreted most active and passive sentences. They failed, however, to assign thematic roles and adjectives in center-embedded relative sentences, and instead relied on nonsyntactic information. These results show that both semantic and syntactic information contributed to sentence comprehension in the aphasic subjects we tested, in contrast to previous claims that syntactic and semantic processes are completely dissociated in this population.