Assessment of verb and sentence processing deficits in stroke-induced aphasia: the Italian version of the Northwestern Assessment of Verbs and Sentences (NAVS-I)

Background

The Northwestern Assessment of Verbs and Sentences (NAVS) assesses verb and sentence production and comprehension in aphasia. Results from the original English version and from its adaptation to German have shown that the NAVS is able to capture effects of verb-argument structure (VAS) complexity (i.e., lower accuracy for two- and three-argument vs. one-argument verbs) and syntactic complexity (i.e., lower accuracy for non-canonical vs. canonical sentences) in both agrammatic participants and individuals with mild (residual) forms of aphasia. The NAVS has been recently adapted to Italian (NAVS-I) and tested on a group of healthy participants, with results showing longer reaction times to complex vs. simple verbs and sentences.

Aims

The present study aimed to test the ability of NAVS-I to i) capture verb/sentence production and comprehension deficits in Italian-speaking individuals with agrammatism or with fluent aphasia, and ii) differentiate individuals with aphasia from healthy age-matched participants, with the overall goal to validate its use in clinical practice.

Methods & Procedures

Forty-four healthy participants and 28 individuals with aphasia (10 with agrammatic speech production) were administered the NAVS-I, which includes tasks assessing production and comprehension of verbs requiring one, two or three arguments, as well as production and comprehension of canonical and non-canonical sentences.

Outcomes & Results

On the Verb Naming Task (VNT), better production of one- (vs. two- and three-) argument verbs was found in the agrammatic group, whereas, verb production in the fluent group was solely predicted by word length and imageability. No effects of argument optionality (i.e., greater difficulty for optionally transitive verbs than for 1-argument verbs) were found. Sentence-level tasks found no differences between the agrammatic and the fluent group in production or comprehension of both canonical and non-canonical sentences; rather, sentence comprehension accuracy was predicted by demographic variables and by aphasia severity. At the individual level, performance on the NAVS-I was significantly different from that of healthy speakers in 26/28 patients.

Conclusions

Data show that the NAVS-I is able to capture effects of argument structure complexity in verb production, and effects of syntactic complexity in sentence production and comprehension. In addition, our results point to verb production as the task with greater capability to differentiate agrammatism from other (fluent) forms of aphasia. The study provides support for the use of the NAVS-I in the diagnosis of aphasia, as it is able to detect language deficits at the individual level, even in participants with mild (residual) forms of aphasia.

Buccofacial apraxia in primary progressive aphasia

Buccofacial apraxia (BFA) is associated with nonfluent/agrammatic variant primary progressive aphasia (nfvPPA) as well as with the severity of apraxia of speech (AOS), a core symptom of nfvPPA. However, an association with agrammatism has not been established. The aim of this study was to examine the association between BFA and agrammatism in nfvPPA and to determine differences in atrophic regions in primary progressive aphasia (PPA) with and without BFA. Seventy-four patients with PPA were recruited, including 34, 15, 10, and 15 patients with nfvPPA, semantic variant PPA, logopenic variant PPA, and unclassified PPA, respectively. All patients underwent language examination and BFA evaluations. Voxel-based morphometry (VBM) was performed to determine whether atrophy of a specific lesion correlated with the presence of BFA. BFA was observed in 20 and 3 patients with nfvPPA and unclassified PPA, respectively. In a comparison of patients with nfvPPA with and without BFA, the BFA group showed significantly worse spontaneous speech and writing in the Western Aphasia Battery. The agrammatism ratio or the ratio of agrammatic errors to the total number of particles was higher in the BFA group; however, the severity of prosodic and phonetic components of AOS did not differ between the two groups. VBM showed that the severity of BFA correlated with atrophy of the opercular and triangular areas of the inferior frontal gyrus to a part of the left middle frontal gyrus. BFA has a different anatomical basis from AOS in patients with nfvPPA and that BFA is characterized by more anterior degeneration compared to that of AOS.

Tractography of supplementary motor area projections in progressive speech apraxia and aphasia

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Degeneration of SMA white matter tracts occurs in progressive apraxia of speech.

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SMA commissural, putamen and precentral tracts were associated with speech apraxia.

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Agrammatism was associated with SMA-prefrontal and frontal aslant tracts.

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Tract profile analysis suggests different disease epicenters across syndromes.

Progressive apraxia of speech (AOS) is a motor speech disorder affecting the ability to produce phonetically or prosodically normal speech. Progressive AOS can present in isolation or co-occur with agrammatic aphasia and is associated with degeneration of the supplementary motor area. We aimed to assess breakdowns in structural connectivity from the supplementary motor area in patients with any combination of progressive AOS and/or agrammatic aphasia to determine which supplementary motor area tracts are specifically related to these clinical symptoms. Eighty-four patients with progressive AOS or progressive agrammatic aphasia were recruited by the Neurodegenerative Research Group and underwent neurological, speech/language, and neuropsychological testing, as well as 3 T diffusion magnetic resonance imaging. Of the 84 patients, 36 had apraxia of speech in isolation (primary progressive apraxia of speech, PPAOS), 40 had apraxia of speech and agrammatic aphasia (AOS-PAA), and eight had agrammatic aphasia in isolation (progressive agrammatic aphasia, PAA). Tractography was performed to identify 5 distinct tracts connecting to the supplementary motor area. Fractional anisotropy and mean diffusivity were assessed at 10 positions along the length of the tracts to construct tract profiles, and median profiles were calculated for each tract. In a case-control comparison, decreased fractional anisotropy and increased mean diffusivity were observed along the supplementary motor area commissural fibers in all three groups compared to controls. PPAOS also had abnormal diffusion in tracts from the supplementary motor area to the putamen, prefrontal cortex, Broca’s area (frontal aslant tract) and motor cortex, with greatest abnormalities observed closest to the supplementary motor area. The AOS-PAA group showed abnormalities in the same set of tracts, but with greater involvement of the supplementary motor area to prefrontal tract compared to PPAOS. PAA showed abnormalities in the left prefrontal and frontal aslant tracts compared to both other groups, with PAA showing greatest abnormalities furthest from the supplementary motor area. Severity of AOS correlated with tract metrics in the supplementary motor area commissural and motor cortex tracts. Severity of aphasia correlated with the frontal aslant and prefrontal tracts. These findings provide insight into how AOS and agrammatism are differentially related to disrupted diffusivity, with progressive AOS associated with abnormalities close to the supplementary motor area, and the frontal aslant and prefrontal tracts being particularly associated with agrammatic aphasia.

Functional differentiation in the language network revealed by lesion-symptom mapping

Theories of language organization in the brain commonly posit that different regions underlie distinct linguistic mechanisms. However, such theories have been criticized on the grounds that many neuroimaging studies of language processing find similar effects across regions. Moreover, condition by region interaction effects, which provide the strongest evidence of functional differentiation between regions, have rarely been offered in support of these theories. Here we address this by using lesion-symptom mapping in three large, partially-overlapping groups of aphasia patients with left hemisphere brain damage due to stroke (N = 121, N = 92, N = 218). We identified multiple measure by region interaction effects, associating damage to the posterior middle temporal gyrus with syntactic comprehension deficits, damage to posterior inferior frontal gyrus with expressive agrammatism, and damage to inferior angular gyrus with semantic category word fluency deficits. Our results are inconsistent with recent hypotheses that regions of the language network are undifferentiated with respect to high-level linguistic processing.

Contribution of the Cerebellum and the Basal Ganglia to Language Production: Speech, Word Fluency, and Sentence Construction-Evidence from Pathology

Evidence reported in recent decades increasingly confirms that both the cerebellum and the basal ganglia, which are primarily involved in movement control, also have a significant role in a vast range of cognitive and affective functions. Evidence from pathology indicates that the disorders of some aspects of language production which follow damage of the cerebellum or respectively basal ganglia, i.e., disorders of speech, word fluency, and sentence construction, have identifiable neuropsychological profiles and that most manifestations can be specifically attributed to the dysfunctions of mechanisms supported by one or the other of these structures. The cerebellum and the basal ganglia are reciprocally interconnected. Thus, it is plausible that some disorders observed when damage involves one of these structures could be remote effects of abnormal activity in the other. However, in a purely clinical-neuropsychological perspective, primary and remote effects in the network are difficult to disentangle. Functional neuroimaging and non-invasive brain stimulation techniques likely represent the indispensable support for achieving this goal.

BEPS: Development, validation, and normative data of a sentence production test in French

Assessing one's sentence production ability can help to identify difficulties experienced by individuals with aphasia and enables targeted intervention. Speech-language pathologists working with the francophone population must contend with the current lack of a sentence production evaluation tool. The aim of this article is to present the development, validation, and normative data of a French-language test used to evaluate the production of sentences: the BEPS (Batterie d'Évaluation de la Production Syntaxique). The BEPS includes four tasks based on Bock and Levelt's model of sentence production, namely (1) Verb Naming Task, (2) Verb Inflection Task, (3) Constituent Assembly Task, and (4) Thematic Role Assignment Task. For each task, various psycholinguistic parameters were controlled or manipulated. The BEPS had good content and construct validity, excellent test-retest reliability and good internal consistency. This battery fulfills the current needs for clinical tool in the francophone population when assessing sentence production capacities. Normative data are presented for individuals 19-79 years of age (n = 191). Raw scores were converted to percentiles for each task. The BEPS represents significant assistance to help clinicians identify the origins of the syntactic production deficits of patients with poststroke and degenerative diseases.

Quantitative assessment of grammar in amyloid-negative logopenic aphasia

Logopenic primary progressive aphasia (lvPPA) typically results from underlying Alzheimer's disease, but subjects have been reported that do not show beta-amyloid (Aβ) deposition. These subjects do not differ on neurological and speech-language testing from Aβ-positive lvPPA, but they impressionistically show increased grammatical deficits. We performed a quantitative linguistic analysis of grammatical characteristics in Aβ-negative lvPPA compared to Aβ-positive lvPPA and agrammatic PPA, which is characterized by increased grammatical difficulties. Aβ-negative lvPPA used fewer function words and correct verbs but more syntactic and semantic errors compared to Aβ-positive lvPPA. These measures did not differ between Aβ-negative lvPPA and agPPA. Both lvPPA cohorts showed a higher mean length of utterance, more complex sentences, and fewer nouns than agPPA. Aβ-negative lvPPA subjects appear unique and share linguistic features with both agPPA and Aβ-positive lvPPA. Quantitative language analysis in lvPPA may be able to distinguish those with and without Aβ deposition.

Distinct [18F]THK5351 binding patterns in primary progressive aphasia variants

PURPOSE

To assess the binding of the PET tracer [¹⁸F]THK5351 in patients with different primary progressive aphasia (PPA) variants and its correlation with clinical deficits. The majority of patients with nonfluent variant (NFV) and logopenic variant (LV) PPA have underlying tauopathy of the frontotemporal lobar or Alzheimer disease type, respectively, while patients with the semantic variant (SV) have predominantly transactive response DNA binding protein 43-kDa pathology.

METHODS

The study included 20 PPA patients consecutively recruited through a memory clinic (12 NFV, 5 SV, 3 LV), and 20 healthy controls. All participants received an extensive neurolinguistic assessment, magnetic resonance imaging and amyloid biomarker tests. [¹⁸F]THK5351 binding patterns were assessed on standardized uptake value ratio (SUVR) images with the cerebellar grey matter as the reference using statistical parametric mapping. Whole-brain voxel-wise regression analysis was performed to evaluate the association between [¹⁸F]THK5351 SUVR images and neurolinguistic scores. Analyses were performed with and without partial volume correction.

RESULTS

Patients with NFV showed increased binding in the supplementary motor area, left premotor cortex, thalamus, basal ganglia and midbrain compared with controls and patients with SV. Patients with SV had increased binding in the temporal lobes bilaterally and in the right ventromedial frontal cortex compared with controls and patients with NFV. The whole-brain voxel-wise regression analysis revealed a correlation between agrammatism and motor speech impairment, and [¹⁸F]THK5351 binding in the left supplementary motor area and left postcentral gyrus. Analysis of [¹⁸F]THK5351 scans without partial volume correction revealed similar results.

CONCLUSION

[¹⁸F]THK5351 imaging shows a topography closely matching the anatomical distribution of predicted underlying pathology characteristic of NFV and SV PPA. [¹⁸F]THK5351 binding correlates with the severity of clinical impairment.

Investigating the origin of nonfluency in aphasia: A path modeling approach to neuropsychology

A major challenge in understanding the origin of clinical symptoms in neuropsychological impairments is capturing the complexity of the underlying cognitive structure. This paper presents a practical guide to path modeling, a statistical approach that is well-suited for modeling multivariate outcomes with a multi-factorial origin. We discuss a step-by-step application of such a model to the problem of nonfluency in aphasia. Individuals with aphasia are often classified into fluent and nonfluent groups for both clinical and research purposes, but despite a large body of research on the topic, the origin of nonfluency remains obscure. We propose a model of nonfluency inspired by the psycholinguistic approach to sentence production, review several bodies of work that have independently suggested a relationship between fluency and various elements in this model, and implement it using path modeling on data from 112 individuals with aphasia from the AphasiaBank. The results show that word production, comprehension, and working memory deficits all contribute to nonfluency, in addition to syntactic impairment which has a strong and direct impact on fluency. More generally, we demonstrate that a path model is an excellent tool for exploring complex neuropsychological symptoms such as nonfluency.

Tracking the development of agrammatic aphasia: A tensor-based morphometry study

Agrammatic aphasia can be observed in neurodegenerative disorders and has been traditionally linked with damage to Broca's area, although there have been disagreements concerning whether damage to Broca's area is necessary or sufficient for the development of agrammatism. We aimed to investigate the neuroanatomical correlates of the emergence of agrammatic aphasia utilizing a unique cohort of patients with primary progressive apraxia of speech (PPAOS) that did not have agrammatism at baseline but developed agrammatic aphasia over time. Twenty PPAOS patients were recruited and underwent detailed speech/language assessments and 3T MRI at two visits, approximately two years apart. None of the patients showed evidence of agrammatism in writing or speech at baseline. Eight patients developed aphasia at follow-up (progressors) and 12 did not (non-progressors). Tensor-based morphometry utilizing symmetric normalization (SyN) was used to assess patterns of grey matter atrophy and voxel-based morphometry was used to assess patterns of grey matter loss at baseline. The progressors were younger at onset and more likely to show distorted sound substitutions or additions compared to non-progressors. Both groups showed change over time in premotor and motor cortices, posterior frontal lobe, basal ganglia, thalamus and midbrain, but the progressors showed greater rates of atrophy in left pars triangularis, thalamus and putamen compared to non-progressors. The progressors also showed greater grey matter loss in pars triangularis and putamen at baseline. This cohort provided a unique opportunity to assess the anatomical changes that accompany the development of agrammatic aphasia. The results suggest that damage to a network of regions including Broca's area, thalamus and basal ganglia are responsible for the development of agrammatic aphasia in PPAOS. Clinical and neuroimaging abnormalities were also present before the onset of agrammatism that could help improve prognosis in these subjects.

An Exploratory Investigation of E-Rest: Teletherapy for Chronically Aphasic Speakers

Delivering aphasia therapy via telecommunication may provide a means to deliver intensive therapy in a cost-effective way. Teletherapy, remotely-administered (language) treatment, may support the repetitive drill practices that people with chronic aphasia need to perform when learning to compensate for their lasting language difficulties. The use of teletherapy may allow speech and language pathologists (SLPs) to focus in-person sessions more strongly on the generalisation of therapy effects to daily life. This single subject study is an investigation whether a teletherapy application called e-REST meets the criteria of accessibility, user-friendliness, as well as effectiveness. e-REST, the teletherapy version of the Dutch and adapted Reduced Syntax Therapy, teaches chronically aphasic speakers of Dutch who experience difficulties in sentence production to convey their messages in a kind of telegraphic style. The results obtained suggest that it is reasonable to conduct a larger study into the user-friendliness, accessibility, effectiveness, and cost-effectiveness of e-REST.

A characterization of verb use in Turkish agrammatic narrative speech

This study investigates the characteristics of narrative-speech production and the use of verbs in Turkish agrammatic speakers (n = 10) compared to non-brain-damaged controls (n = 10). To elicit narrative-speech samples, personal interviews and storytelling tasks were conducted. Turkish has a large and regular verb inflection paradigm where verbs are inflected for evidentiality (i.e. direct versus indirect evidence available to the speaker). Particularly, we explored the general characteristics of the speech samples (e.g. utterance length) and the uses of lexical, finite and non-finite verbs and direct and indirect evidentials. The results show that speech rate is slow, verbs per utterance are lower than normal and the verb diversity is reduced in the agrammatic speakers. Verb inflection is relatively intact; however, a trade-off pattern between inflection for direct evidentials and verb diversity is found. The implications of the data are discussed in connection with narrative-speech production studies on other languages.

Comparing the production of complex sentences in Persian patients with post-stroke aphasia and non-damaged people with normal speaking

BACKGROUND

Cerebrovascular disease leading to stroke is the most common cause of aphasia. Speakers with agrammatic non-fluent aphasia have difficulties in production of movement-derived sentences such as passive sentences, topicalized constituents, and Wh-questions. To assess the production of complex sentences, some passive, topicalized and focused sentences were designed for patients with non-fluent Persian aphasic. Afterwards, patients' performance in sentence production was tested and compared with healthy non-damaged subjects.

METHODS

In this cross sectional study, a task was designed to assess the different types of sentences (active, passive, topicalized and focused) adapted to Persian structures. Seven Persian patients with post-stroke non-fluent agrammatic aphasia (5 men and 2 women) and seven healthy non-damaged subjects participated in this study. The computed tomography (CT) scan or magnetic resonance imaging (MRI) showed that all the patients had a single left hemisphere lesion involved middle cerebral artery (MCA), Broca`s area and in its white matter. In addition, based on Bedside version of Persian Western Aphasia Battery (P-WAB-1), all of them were diagnosed with moderate Broca aphasia. Then, the production task of Persian complex sentences was administered.

RESULTS

There was a significant difference between four types of sentences in patients with aphasia [Degree of freedom (df) = 3, P < 0.001]. All the patients showed worse performance than the healthy participants in all the four types of sentence production (P < 0.050).

CONCLUSION

In general, it is concluded that topicalized and focused sentences as non-canonical complex sentences in Persian are very difficult to produce for patients with agrammatic non-fluent aphasia. It seems that sentences with A-movement are simpler for the patients than sentences involving A`-movement; since they include shorter movements in compare to topicalized and focused sentences.

Losing track of time? Processing of time reference inflection in agrammatic and healthy speakers of German

BACKGROUND

Individuals with agrammatic aphasia (IWAs) have problems with grammatical decoding of tense inflection. However, these difficulties depend on the time frame that the tense refers to. Verb morphology with reference to the past is more difficult than with reference to the non-past, because a link needs to be made to the past event in discourse, as captured in the PAst DIscourse LInking Hypothesis (PADILIH; Bastiaanse, R., Bamyaci, E., Hsu, C., Lee, J., Yarbay Duman, T., Thompson, C. K., 2011. Time reference in agrammatic aphasia: A cross-linguistic study. J. Neurolinguist. 24, 652-673). With respect to reference to the (non-discourse-linked) future, data so far indicate that IWAs experience less difficulties as compared to past time reference (Bastiaanse, R., Bamyaci, E., Hsu, C., Lee, J., Yarbay Duman, T., Thompson, C. K., 2011. Time reference in agrammatic aphasia: A cross-linguistic study. J. Neurolinguist. 24, 652-673), supporting the assumptions of the PADILIH. Previous online studies of time reference in aphasia used methods such as reaction times analysis (e.g., Faroqi-Shah, Y., Dickey, M. W., 2009. On-line processing of tense and temporality in agrammatic aphasia. Brain Lang. 108, 97-111). So far, no such study used eye-tracking, even though this technique can bring additional insights (Burchert, F., Hanne, S., Vasishth, S., 2013. Sentence comprehension disorders in aphasia: the concept of chance performance revisited. Aphasiology 27, 112-125, doi:10.1080/02687038.2012.730603).

AIMS

This study investigated (1) whether processing of future and past time reference inflection differs between non-brain-damaged individuals (NBDs) and IWAs, and (2) underlying mechanisms of time reference comprehension failure by IWAs.

METHODS AND PROCEDURES

A visual-world experiment combining sentence-picture matching and eye-tracking was administered to 12 NBDs and 6 IWAs, all native speakers of German. Participants heard German sentences with periphrastic future ('will+V') or periphrastic past ('has+V-d') verb forms while they were presented with corresponding pictures on a computer screen.

RESULTS AND DISCUSSION

NBDs scored at ceiling and significantly higher than the IWAs. IWAs had below-ceiling performance on the future condition, and both participant groups were faster to respond to the past than to the future condition. These differences are attributed to a pre-existing preference to look at a past picture, which has to be overcome. Eye movement patterns suggest that both groups interpret future time reference similarly, while IWAs show a delay relative to NBDs in interpreting past time reference inflection. The eye tracking results support the PADILIH, because processing reference to the past in discourse syntax requires additional resources and thus, is problematic and delayed for people with aphasia.

A Systematic Review on methods of evaluate sentence production deficits in agrammatic aphasia patients: Validity and Reliability issues

BACKGROUND

The grammar assessment in aphasia has been done by few standard tests, but today these tests cannot precise evaluate the sentence production in agrammatic patients. In this study, we review structures and contents of tests or tasks designed to find more frequent methods for sentence production ability in aphasia patients.

MATERIALS AND METHODS

We searched the Cochrane library, Medline by PubMed, Science Direct, Scopus, and Google Scholar from 1980 to October 1, 2013 and evaluated all of exist tests or tasks included in the articles and systematic reviews. The sentence production has been studied in three methods. It contains the use of sentence production in spontaneous speech, tasks designed and both methods. The quality of studies was assessed using Critical Appraisal Skills Program.

RESULTS

The 160 articles were reviewed and 38 articles were studied according to inclusion and exclusion criteria. They were classified into three categories based on assessment methods of sentence production. In 39.5% studies, researchers have used tasks designed, 7.9% articles have applied spontaneous speech and 52.6% articles have used both methods for evaluation production. Inter-rater reliability was between 90% and 100% and intra-rater reliability was between 96% and 98% in studied.

CONCLUSION

Agrammatic aphasia has syntax disorders, especially in sentence production. Most researchers and clinicians used both methods for evaluation production.

Primary progressive aphasia: linguistic patterns and clinical variants

We investigated whether primary progressive aphasias (PPA) reflect non-random degradation of linguistic dimensions that might be supported by different neural subsystems and to what extent this degradation contributes to the emergence of clinical entities: semantic (S), logopenic (L) and nonfluent (NF) aphasia; apraxia of speech was also considered if associated with language disorders (AOS/aph). Forty-two aphasic patients are reported. Two main definable patterns of linguistic deficits tended to emerge that corresponded with identifiable patterns of brain atrophy, and probably diseases: the S variant, which principally expresses the impact of a "deep" cognitive (semantic) disorder on language, and AOS/aph in which "peripheral" executive components play a significant role. By contrast, NF aphasia emerged as a heterogeneous variant due to disorganization of various dimensions within the linguistic domain, that assumes different patterns depending on the differential distribution of atrophy in the perisylvian regions.

Time reference in agrammatic aphasia: A cross-linguistic study

It has been shown across several languages that verb inflection is difficult for agrammatic aphasic speakers. In particular, Tense inflection is vulnerable. Several theoretical accounts for this have been posed, for example, a pure syntactic one suggesting that the Tense node is unavailable due to its position in the syntactic tree (Friedmann & Grodzinsky, 1997); one suggesting that the interpretable features of the Tense node are underspecified (Burchert, Swoboda-Moll, & De Bleser, 2005; Wenzlaff & Clahsen, 2004, 2005); and a morphosemantic one, arguing that the diacritic Tense features are affected in agrammatism (Faroqi-Shah & Dickey, 2009; Lee, Milman, & Thompson, 2008). However recent findings (Bastiaanse, 2008) and a reanalysis of some oral production studies (e.g. Lee et al., 2008; Nanousi, Masterson, Druks, & Atkinson, 2006) suggest that both Tense and Aspect are impaired and, most importantly, reference to the past is selectively impaired, both through simple verb forms (such as simple past in English) and through periphrastic verb forms (such as the present perfect, 'has V-ed', in English). It will be argued that reference to the past is discourse linked and reference to the present and future is not (Zagona, 2003, in press). In-line with Avrutin's (2000) theory that suggests discourse linking is impaired in Broca's aphasia, the PAst DIscourse LInking Hypothesis (PADILIH) has been formulated. Three predictions were tested: (1) patients with agrammatic aphasia are selectively impaired in use of grammatical morphology associated with reference to the past, whereas, inflected forms which refer to the present and future are relatively spared; (2) this impairment is language-independent; and (3) this impairment will occur in both production and comprehension. Agrammatic Chinese, English and Turkish speakers were tested with the Test for Assessing Reference of Time (TART; Bastiaanse, Jonkers, & Thompson, unpublished). Results showed that both the English and Turkish agrammatic speakers performed as hypothesized, showing a selective deficit for production of inflected forms referring to the past, despite the typological difference between the languages. The Chinese agrammatic speakers were poor in reference to the past as well, but reference to the present and future also was severely impaired. For comprehension, the results were strikingly similar for the three languages: reference to the past was impaired for all. These results confirmed our hypothesis that reference to the past is discourse linked and, therefore, grammatical morphology used for reference to the past is impaired in agrammatic aphasia, whether this is done through Tense and/or Aspect markers.

Effects of syntactic and semantic argument structure on sentence repetition in agrammatism: Things we can learn from particles and prepositions

BACKGROUND

Sentence production impairment in aphasia has been attributed to several possible sources that are not mutually exclusive. Linguistic accounts often attribute the difficulty to the complexity of a verb's syntactic and/or semantic argument structure. Cognitive processing accounts emphasise the reduced processing capacity observed in agrammatic aphasia, which in turn has been attributed to reduced semantic short-term memory (STM) or slowed processing.

AIMS

In this study we used verb particles and prepositions to investigate effects of differences in syntactic and semantic argument structure on sentence repetition in aphasia. We predicted that verb particles and sentences containing verb-particle constructions would be easier to repeat than prepositions and prepositional transitive sentences, as the former have a less-complex semantic and syntactic argument structure than the latter. Also, semantic and phonological spans were assessed to determine if a reduction in either capacity correlates with repetition ability.

METHODS & PROCEDURES

Participants were eight individuals with chronic aphasia. The experimental task was repetition of transitive sentences balanced for length and lexical content containing either verb particles or prepositional object structures. Accuracy of sentence repetition and repetition of verb particles and prepositions within sentences was examined. We calculated the effect of structural complexity on the sentence repetition task as the difference between proportion correct of verb-particle constructions and prepositional transitives. Semantic and phonological STM spans and word spans were also assessed and correlated with this measure of the structural complexity effect on sentence repetition.

OUTCOMES & RESULTS

Verb-particle sentences were repeated correctly significantly more often than prepositional transitive sentences, and within those sentences verbal particles were repeated correctly significantly more often than prepositions. The effect was strongly associated with fluency scores: it was present in participants with low fluency scores, but not in those with high fluency scores. The phonological, but not the semantic, STM probe span measure correlated with both the difference in accurate repetition of verb-particle and prepositional transitive sentences and the particles and prepositions within those sentences.

CONCLUSIONS

Results indicate that differences in argument structure of particle and preposition constructions influence sentence repetition in agrammatic aphasia. The finding that lower fluency scores are associated with poorer performance on more complex structures suggests that this effect is associated with agrammatism. The impact of these structural distinctions between particles and prepositions should be taken into account during development of treatment stimuli for those with agrammatism.