Syntactic processing in agrammatic aphasia by speakers of a Slavic language

Morphosyntactic Production and Verbal Working Memory: Evidence From Greek Aphasia and Healthy Aging

PURPOSE

The present work investigated whether verbal working memory (WM) affects morphosyntactic production in configurations that do not involve or favor similarity-based interference and whether WM interacts with verb-related morphosyntactic categories and/or cue-target distance (locality). It also explored whether the findings related to the questions above lend support to a recent account of agrammatic morphosyntactic production: Interpretable Features' Impairment Hypothesis (Fyndanis, Varlokosta, & Tsapkini, 2012).

METHOD

A sentence completion task testing production of subject-verb agreement, tense/time reference, and aspect in local and nonlocal conditions and two verbal WM tasks were administered to 8 Greek-speaking persons with agrammatic aphasia (PWA) and 103 healthy participants.

RESULTS

The 3 morphosyntactic categories dissociated in both groups (agreement > tense > aspect). A significant interaction emerged in both groups between the 3 morphosyntactic categories and WM. There was no main effect of locality in either of the 2 groups. At the individual level, all 8 PWA exhibited dissociations between agreement, tense, and aspect, and effects of locality were contradictory.

CONCLUSIONS

Results suggest that individuals with WM limitations (both PWA and healthy older speakers) show dissociations between the production of verb-related morphosyntactic categories. WM affects performance shaping the pattern of morphosyntactic production (in Greek: subject-verb agreement > tense > aspect). The absence of an effect of locality suggests that executive capacities tapped by WM tasks are involved in morphosyntactic processing of demanding categories even when the cue is adjacent to the target. Results are consistent with the Interpretable Features' Impairment Hypothesis (Fyndanis et al., 2012).

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.6024428.

Sentence comprehension in Slovak-speaking patients with Alzheimer's disease

BACKGROUND

According to some studies, sentence comprehension is diminished in Alzheimer's disease (AD) patients, but they differ on what underlies the sentence comprehension impairment. Sentence comprehension in AD patients has been studied mainly in the English language. It is less clear how patients with AD speaking a morphologically rich language with grammatical morphemes indicating case and through it even thematic roles process reversible sentences.

AIMS

To compare the comprehension of various syntactic constructions in Slovak-speaking AD patients and cognitively intact elderly people. We were concerned with the influence of the following aspects on sentence comprehension: its length, the order of thematic roles and the presence of a morphological cue placed on the first noun (or at the beginning of a sentence).

METHODS & PROCEDURES

We used our own Slovak test of sentence comprehension based on matching pictures to spoken sentences. These sentences contain transitive verbs and two nouns (person/animal), one functioning as a subject and the other as an object, which both can perform the action expressed by the verb. We assessed 62 healthy elderly people and two groups of AD patients. The first group consisted of 34 participants with a mild degree of AD and the other group of 43 participants with a moderate degree of AD.

OUTCOME & RESULTS

Statistical comparisons showed that the elderly controls were significantly better in the comprehension of simple active OVS (object-verb-subject word order) sentences and complex EO sentences (a centre-embedded relative clause with a relative pronoun substituting for an object) than patients with a mild degree of AD. In patients with a moderate degree of AD, comprehension of all tested sentence types was worse than in healthy elderly people. The results also indicated that even mild AD patients have more serious problems with processing sentences with non-canonical order of thematic roles regardless of a morphological cue at the beginning of a sentence.

CONCLUSION & IMPLICATIONS

The results point to diminished sentence comprehension in patients with AD. In the group of mild AD patients, the order of thematic roles played a significant role in their sentence comprehension. Even though the grammatical morphemes clearly code the functions of words in the Slovak language, mild AD patients do not process them in sentences with a non-canonical order of thematic roles at the same level as the healthy controls. Patients with moderate AD have significant problems even with the comprehension of sentences with a canonical order of thematic roles. These difficulties seem to be a consequence of insufficient resources for language processing.

The role of the striatum in sentence processing: disentangling syntax from working memory in Huntington's disease

The role of sub-cortical structures in language processing remains controversial. In particular, it is unclear whether the striatum subserves language-specific processes such as syntax or whether it solely affects language performance via its significant role in executive functioning and/or working memory. Here, in order to address this issue, we attempted to equalize working memory constraints while varying syntactic complexity, to study sentence comprehension in 15 patients with striatal damage, namely Huntington's disease at early stage, and in 15 healthy controls. More particularly, we manipulated the syntactic relation between a name and a pronoun while holding the distance between them constant. We exploited a formal principle of syntactic theory called Principle C. This principle states that whereas in a sentence such as "Paul smiled when he entered" Paul and he can be a single person, this interpretation is blocked in sentences such as "He smiled when Paul entered". In a second experiment we varied working memory load using noun-adjective gender agreement in center-embedded and right-branching relatives (e.g., "the girl who watches the dog is green" vs. "the girl watches the dog which is green"). The results show that HD patients correctly establish name-pronoun co-reference but they fail to block it when Principle C should apply. Furthermore, they have good performance with both center-embedded and right-branching relatives, suggesting that their difficulties in sentence comprehension do not arise from memory load impairment during sentence processing. Taken together, our findings indicate that the striatum holds a genuine role in syntactic processing, which cannot be reduced to its involvement in working memory. However, it only impacts on particular aspects of syntax that may relate to complex computations whereas other operations appear to be preserved. Hypotheses about the role of the striatum in syntactic processing are discussed.

Testing the limits of language production in long-term survivors of major stroke: A psycholinguistic and anatomic study

BACKGROUND: There is still a dearth of information about grammatical aspects of language production in aphasia. AIMS: Making novel use of methods of elicited production aimed at testing the limits of competence, we studied three cases of chronic aphasia, stemming from major stroke. We asked: (1) Whether the elicited production method reveals sparing of language abilities not readily evidenced in spontaneous utterances or on conventional aphasia tests. (2) Which language production abilities survive damage to both Broca's region and Wernicke's region? MATERIALS & PROCEDURES: Targeted words, morphological and syntactic structures were elicited by sentence completion with supporting linguistic and visual context. Targets were never modelled during the procedure. For verbs, visual and auditory contexts emphasise completed actions, targeting past tense forms. Lesion description was based on structural MRI scans. OUTCOMES & RESULTS: The three participants showed partially spared ability to produce nouns, adjectives, and verb stems in context. The elicitation method proved more productive in some cases than picture prompts or sentence prompts. Past tense inflections were usually omitted. Hence stems and inflections were dissociable. Two participants showed partial success with the passive, and no participant produced a full relative clause, including the relative pronoun, but two produced reduced forms of subject relatives. Partial sparing of production capability in these cases points to the likely importance of portions of the left hemisphere remote from Broca and Wernicke regions. CONCLUSIONS: This application of elicited production methodology demonstrates possibilities of lexical, morphological, and syntactic production not evident in spontaneous utterances or by conventional aphasia tests. Some lexical and grammatical capabilities survived massive damage to both anterior and posterior portions of the left hemisphere.

Asyntactic thematic role assignment by Mandarin aphasics: a test of the Trace-Deletion Hypothesis and the Double Dependency Hypothesis

This study examines the comprehension patterns of various sentence types by Mandarin-speaking aphasic patients and evaluates the validity of the predictions from the Trace-Deletion Hypothesis (TDH) and the Double Dependency Hypothesis (DDH). Like English, the canonical word order in Mandarin is SVO, but the two languages differ in that the head noun precedes the relative clause in English, but it follows the relative clause in Chinese. According to the Default Principle as stated in the TDH, the word order discrepancy will make subject relative clauses more difficult to comprehend for Mandarin agrammatics than object relative clauses, but the DDH predicts that agrammatic patients from the two languages have the same pattern of selective deficits. The results of this study support the prediction of the TDH.

Grammatism

Findings from the literature on language development, dyslexia, and adult sentence processing provide a vehicle for comparing two models of the symptom complex associated with agrammatism. One model contends that agrammatism represents a deficit in linguistic structures. The other model maintains that the linguistic behavior associated with agrammatism is the result of a limitation in language processing. To adjudicate between the models, the present paper examines one linguistic construction, the restrictive relative clause. The results of experimental investigations across several subject populations reveal parallel patterns of linguistic behavior on this construction. The findings favor the processing limitation account of the linguistic difficulties experienced by agrammatic aphasics in comprehending sentences with a restrictive relative clause.

The critical role of group studies in neuropsychology: comprehension regularities in Broca's aphasia

We reexamine the empirical record of the comprehension abilities of Broca's aphasic patients. We establish clear, commonly accepted, selection criteria and obtain a pool of results. We then subject these results to a detailed statistical analysis and show that these patients comprehend certain canonical sentences (actives, subject relatives, and clefts with agentive predicates) at above-chance levels, whereas comprehension of sentences that contain deviations from canonicity (passives, object-gap relatives, and clefts) is distinct and is at chance. That the latter is the case, and patients indeed guess at such structures, we show by comparing the distribution of individual results in passive comprehension to that of a model for such guessing-an analogous series of tosses of an unbiased coin. The two distributions are virtually identical. We conclude that the group's performance is stable, and well-delineated, despite intersubject variation whose source is now identified. This means that certain comprehension tests may not always be used for the diagnosis of individual patients, but they do characterize the group. It also means that group studies are not just a valid option in neuropsychology; they are a must, since demonstrations like ours indiciate very clearly that single-case studies may be misleading. As we show, the findings from any one patient, without the context of a group, may give a distorted picture of the pathological reality. Our conclusions thus promote studies of groups of brain-damaged patients as a central tool for the investigation of brain/behavior relations.

Comprehension of nonlexical categories in agrammatism

The focus of the paper is a proposal advanced by Grodzinsky (1984, 1986, 1990) concerning a possible syntactic deficit in agrammatism with respect to nonlexical categories. Eight native speakers of Serbo-Croatian, who presented a clinical picture of Broca's aphasia with agrammatism, were tested. Subjects' sensitivity to traces and their knowledge of the inflectional and determiner system was investigated using a grammaticality judgment paradigm. The processing load was further minimized by use of short sentences that unequivocally exemplified different syntactic violations. These steps led to significant improvement in the performance of agrammatic aphasics, a result that is incompatible with the claim that the content of nonlexical elements is lost in agrammatism.