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An important aspect of aphasia is the observation of behavioral variability between and within individual participants. Our study addresses variability in sentence comprehension in German, by testing 21 individuals with aphasia and a control group and involving (a) several constructions (declarative sentences, relative clauses and control structures with an overt pronoun or PRO), (b) three response tasks (object manipulation, sentence-picture matching with/without self-paced listening), and (c) two test phases (to investigate test-retest performance). With this systematic, large-scale study we gained insights into variability in sentence comprehension. We found that the size of syntactic effects varied both in aphasia and in control participants. Whereas variability in control participants led to systematic changes, variability in individuals with aphasia was unsystematic across test phases or response tasks. The persistent occurrence of canonicity and interference effects across response tasks and test phases, however, shows that the performance is systematically influenced by syntactic complexity.
The presence or absence of generalization after treatment can provide important insights into the functional relationship between cognitive processes. The aim of the present study was to investigate the relationship between the cognitive processes that underlie sentence comprehension and production in aphasia. Using data from seven participants who took part in a case-series intervention study that focused on noncanonical sentence production [Stadie et al. (2008). Unambiguous generalization effects after treatment of noncanonical sentence production in German agrammatism. Brain and Language, 104, 211-229], we identified patterns of impairments and generalization effects for the two modalities. Results showed (a) dissociations between sentence structures and modalities before treatment, (b) an absence of cross-modal generalization from production to comprehension after treatment, and (c), a co-occurrence of spared comprehension before treatment and generalization across sentence structures within production after treatment. These findings are in line with the assumption of modality-specific, but interacting, cognitive processes in sentence comprehension and production. More specifically, this interaction is assumed to be unidirectional, allowing treatment-induced improvements in production to be supported by preserved comprehension.
Recently, neurolinguistic explanations informed by linguistic theory have been proposed to account for spontaneous and elicited agrammatic speech production. These are either formulated in terms of impaired representations or they refer to impaired processing. Both have in common that they assume severe disorders of question production due to vulnerability of the left periphery of sentence structures in the representational account, of verb movement in the processing account. We report the results of question elicitation and spontaneous speech analysis in eight chronic German agrammatic speakers. The results indicate that there is not one homogeneous agrammatic pattern, but that the data reveal double dissociations which cannot be accounted for by the unitary explanations of agrammatism which are presently available. An alternative explanation will be provided which-in contrast to the representational account not only refers to global hierarchically organized nodes but relies on linguistic differences within these nodes. The assumption that they can be differentially affected in agrammatism can account for the observed patterns. (c) 2005 Elsevier Ltd. All rights reserved
Tense and Agreement dissociations in German agrammatic speakers : Underspecification vs. hierarchy
(2005)
The aim of the present paper was to investigate whether German agrammatic production data are compatible with the Tree-Pruning-Hypothesis (TPH; Friedmann & Grodzinsky, 1997). The theory predicts unidirectional patterns of dissociation in agrammatic production data with respect to Tense and Agreement. However, there was evidence of a double dissociation between Tense and Agreement in our data. The presence of a bidirectional dissociation is incompatible with any theory which assumes a hierarchical order between these categories such as the TPH or other versions thereof (such as Lee's, 2003 top-down hypothesis). It will be argued that the data can better be accounted for by relying on newer linguistic theories such as the Minimalist Program (MP, Chomsky, 2000), which does not assume a hierarchical order between independent syntactic Tense and Agreement nodes but treats them as different features (semantically interpretable vs. uninterpretable) under a single node. (c) 2005 Elsevier Inc. All rights reserved
Background: In behavioural tests of sentence comprehension in aphasia, correct and incorrect responses are often randomly distributed. Such a pattern of chance performance is a typical trait of Broca's aphasia, but can be found in other aphasic syndromes as well. Many researchers have argued that chance behaviour is the result of a guessing strategy, which is adopted in the face of a syntactic breakdown in sentence processing. Aims: Capitalising on new evidence from recent studies investigating online sentence comprehension in aphasia using the visual world paradigm, the aim of this paper is to review the concept of chance performance as a reflection of a syntactic impairment in sentence processing and to re-examine the conventional interpretation of chance performance as a guessing behaviour. Main Contribution: Based on a review of recent evidence from visual world paradigm studies, we argue that the assumption of chance performance equalling guessing is not necessarily compatible with actual real-time parsing procedures in people with aphasia. We propose a reinterpretation of the concept of chance performance by assuming that there are two distinct processing mechanisms underlying sentence comprehension in aphasia. Correct responses are always the result of normal-like parsing mechanisms, even in those cases where the overall performance pattern is at chance. Incorrect responses, on the other hand, are the result of intermittent deficiencies of the parser. Hence the random guessing behaviour that persons with aphasia often display does not necessarily reflect a syntactic breakdown in sentence comprehension and a random selection between alternatives. Instead it should be regarded as a result of temporal deficient parsing procedures in otherwise normal-like comprehension routines. Conclusion: Our conclusion is that the consideration of behavioural offline data alone may not be sufficient to interpret a performance in language tests and subsequently draw theoretical conclusions about language impairments. Rather it is important to call on additional data from online studies that look at language processing in real time in order to gain a comprehensive picture about syntactic comprehension abilities of people with aphasia and possible underlying deficits.
Comprehension of non-canonical sentences can be difficult for individuals with aphasia (IWA). It is still unclear to which extent morphological cues like case marking or verb inflection may influence IWA's performance or even help to override deficits in sentence comprehension. Until now, studies have mainly used offline methods to draw inferences about syntactic deficits and, so far, only a few studies have looked at online syntactic processing in aphasia. We investigated sentence processing in German-speaking IWA by combining an offline (sentence-picture matching) and an online (eye-tracking in the visual-world paradigm) method. Our goal was to determine whether IWA are capable of using inflectional morphology (number-agreement markers on verbs and case markers in noun phrases) as a cue to sentence interpretation. We report results of two visual-world experiments using German reversible SVO and OVS sentences. In each study, there were eight IWA and 20 age-matched controls. Experiment 1 targeted the role of unambiguous case morphology, while Experiment 2 looked at processing of number-agreement cues at the verb in caseambiguous sentences. IWA showed deficits in using both types of morphological markers as a cue to non-canonical sentence interpretation and the results indicate that in aphasia, processing of case-marking cues is more vulnerable as compared to verbagreement morphology. We ascribe this finding to the higher cue reliability of agreement cues, which renders them more resistant against impairments in aphasia. However, the online data revealed that IWA are in principle capable of successfully computing morphological cues, but the integration of morphological information is delayed as compared to age-matched controls. Furthermore, we found striking differences between controls and IWA regarding subject-before-object parsing predictions. While in case-unambiguous sentences IWA showed evidence for early subjectbefore-object parsing commitments, they exhibited no straightforward subject-first prediction in case-ambiguous sentences, although controls did so for ambiguous structures. IWA delayed their parsing decisions in case-ambiguous sentences until unambiguous morphological information, such as a subject-verbnumber-agreement cue, was available. We attribute the results for IWA to deficits in predictive processes based on morphosyntactic cues during sentence comprehension. The results indicate that IWA adopt a wait-and-see strategy and initiate prediction of upcoming syntactic structure only when unambiguous case or agreement cues are available. (C) 2015 Elsevier Ltd. All rights reserved.
Background: A large number of studies examining agrammatic comprehension of canonical and non-canonical sentences in Broca's aphasia have focused on passives and results have been interpreted in theoretical frameworks such as the trace deletion hypothesis (TDH: Grodzinsky, 1995a). However, there are a number of unresolved issues associated with passives. The linguistic analysis of passive structures in different languages has remained controversial as well as the empirical neurolinguistic basis of agrammatic passive comprehension. In addition, a variety of morphological and semantic questions have been raised with respect to the implicit argument in short passives and the ordering of thematic roles reflected by different positions of the by-phrase in long passives. Aims: The major aims of the present study were to re-examine the analyses of passives with and without traces, the role of an implicit argument in short passives, and the influence of the position of the by-phrase on agrammatic sentence comprehension. Methods & Procedures: A binary picture-sentence matching task was administered to six non-fluent German agrammatic speakers. Various types of passives including long, short, and topicalised passives were tested. Additionally, comprehension of active SVO sentences was assessed in a separate but similar session. Only those patients whose comprehension on active sentences was above chance were included. Outcomes & Results: As a group, the six subjects performed above chance over all passive types. If only long canonical passives are considered, as is done in most studies, five subjects showed a pattern compatible with the TDH. However, the picture was modified if other passive constructions were taken into account, in which case only three of the six subjects showed TDH conformity. Conclusions: There is no unique pattern of agrammatic passive comprehension and only half of the agrammatic subjects conformed to the trace deletion hypothesis. Given the results on long canonical and topicalised passives, our data support linguistic analyses that assume a trace- based derivation of passives. Furthermore, the results are in line with linguistic analyses adopting an implicit argument in short passives. Since comprehension of topicalised passives with a canonical order of theta-roles was not better than that of long passives without a canonical order, the agrammatic problem with passives does not seem to hinge on semantics