Frank Burchert

Tense and Agreement dissociations in German agrammatic speakers : Underspecification vs. hierarchy

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 Lees, 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,), 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.

Does morphology make the difference? Agrammatic sentence comprehension in German.

This study examines the syntactic comprehension of seven German agrammatic speakers. The German language allows the study of the interaction of syntactic principles and morphological devices in the comprehension process. In addition, due to its relatively free word order, German allows the study of strictly minimal pairs of canonical and non-canonical sentences in addition to the rather controversial active-passive contrast. A central research question was whether the pattern of agrammatic comprehension predicted by the trace deletion hypothesis (TDH, Grodzinsky, 1990, 1995), relatively normal comprehension performance of canonical sentences and chance performance on non-canonical sentences, can be found in a language with richer morphology than English. The generalisability of the TDH-pattern to morphologically rich languages is not obvious, given that case morphology in particular can provide explicit cues to the detection of the agent and patient roles in a sentence. The results of this study indicate that morphology does not make a difference. Furthermore, the group results are in line with the TDH-predictions only for number marked sentences but not for case marked sentences. However, single case analysis reveals different patterns of syntactic comprehension in agrammatic patients, a spectrum that encompasses near-normal comprehension of canonical and non-canonical sentences, overall chance performance, and TDH-like profiles.

Neural correlates of syntactic transformations

Many agrammatic aphasics have a specific syntactic comprehension deficit involving processing syntactic transformations. It has been proposed that this deficit is due to a dysfunction of Brocas area, an area that is thought to be critical for comprehension of complex transformed sentences. The goal of this study was to investigate the role of Brocas area in processing canonical and non‐canonical sentences in healthy subjects. The sentences were presented auditorily and were controlled for task difficulty. Subjects were asked to judge the grammaticality of the sentences while their brain activity was monitored using event‐related functional magnetic resonance imaging. Processing both kinds of sentences resulted in activation of language‐related brain regions. Comparison of non‐canonical and canonical sentences showed greater activation in bilateral temporal regions; a greater activation of Brocas area in processing antecedent‐gap relations was not found. Moreover, the posterior part of Brocas area was conjointly activated by both sentence conditions. Brocas area is thus involved in general syntactic processing as required by grammaticality judgments and does not seem to have a specific role in processing syntactic transformations. Hum. Brain Mapp. 22:74–83, 2004.

Production of Non-Canonical Sentences in Agrammatic Aphasia: Limits in Representation or Rule Application?.

The study reported here compares two linguistically informed hypotheses on agrammatic sentence production, the TPH [Friedmann, N., & Grodzinsky, Y. (1997). Tense and agreement in agrammatic production: Pruning the syntactic tree. Brain and Language, 56, 397-425.] and the DOP [Bastiaanse, R., & van Zonneveld, R. (2005). Sentence production with verbs of alternating transitivity in agrammatic Brocas aphasia. Journal of Neurolinguistics, 18, 59-66]. To explain impaired production of non-canonical sentences in agrammatism, the TPH basically relies on deleted or pruned clause structure positions in the left periphery, whereas the DOP appeals to limitations in the application of movement rules. Certain non-canonical sentences such as object-questions and object-relative clauses require the availability of nodes in the left periphery as well as movement to these nodes. In languages with relatively fixed word order such as English, the relevant test cases generally involve a coincidence of left periphery and movement, such that the predictions of the TPH and the DOP are identical although for different reasons. In languages with relatively free word order such as German, on the other hand, it is possible to devise specific tests of the different predictions due to the availability of scrambling. Scrambled object sentences, for example, do not involve the left periphery but do require application of movement in a domain below the left periphery. A study was conducted with German agrammatic subjects which elicited canonical sentences without object movement and non-canonical scrambled sentences with object movement. The results show that agrammatic speakers have a particular problem with the production of scrambled sentences. Further evidence reported in the study from spontaneous speech, elicitation of object relatives, questions and passives and with different agrammatic subjects confirms that non-canonical sentences are generally harder to produce for agrammatics. These findings provide evidence in favor of the DOP and it will be argued that a cross-modal explanation of agrammatic deficits is possible if two factors--movement and canonicity--are taken into consideration.

Passives in agrammatic sentence comprehension : a German Study

Background: A large number of studies examining agrammatic comprehension of canonical and non‐canonical sentences in Brocas 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.

Sentence comprehension and morphological cues in aphasia: What eye-tracking reveals about integration and prediction

Abstract 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 IWAs 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 case-ambiguous 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 verb-agreement 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 subject-before-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-verb-number-agreement cue, was available. We attribute the results for IWA to deficits in predictive processes based on morpho-syntactic 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.

Unambiguous generalization effects after treatment of non-canonical sentence production in German agrammatism

Agrammatism is-among others, characterized by a deficit in producing grammatical structures. Of specific difficulty is the utilization of complex, non-canonical sentence structures (e.g. object-questions, passives, object-clefts). Several studies have documented positive effects when applying a specific treatment protocol in terms of increasingly correct production of target complex sentence structures with some variance in generalization patterns noted across individuals. The objective of this intervention study was to evaluate an intervention program focussing on the production of non-canonical sentences. Hypotheses about the occurrence of treatment effects were formulated on the basis of syntactic complexity, referring to the amount of syntactic phrase structures necessary to generate specific German sentence structures. A multiple single case study with seven agrammatic participants was applied, each participant receiving training in the production of object-relative-clauses and who-questions. The investigation was designed to unambiguously evaluate for each individual, structure specific and generalized learning effects with respect to the production of object-relative-clauses, who-questions and passive sentences. Results showed significant improvements for all sentences types. This outcome is considered within methodological issues of treatment studies. Theoretical and clinical implications are discussed.

Sentence comprehension disorders in aphasia: The concept of chance performance revisited

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 Brocas 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.

Grammaticality judgments on sentences with and without movement of phrasal constituents—an event-related fMRI study

Abstract One of the leading neurolinguistic theories of syntactic comprehension disorders in agrammatic aphasic subjects—the Trace Deletion Hypothesis—postulates a specific impairment in processing syntactic chains, and that this function is mediated by Brocas area. The aim of this study was to investigate whether the specific involvement of Brocas area in processing syntactic traces can be verified using functional brain imaging. We used event-related functional magnetic resonance imaging (fMRI) while healthy subjects were asked to judge the grammaticality of visually presented sentences with and without movement of phrasal constituents. During both kinds of sentences, fMRI showed activation in language-related brain regions. Comparing both kinds of sentences did not result in differential brain activation of left frontal or temporal regions. In particular, Brocas area was similarly activated in processing both moved and nonmoved sentences. Thus, Brocas area seems to be involved in general syntactic processing as required by grammaticality judgments rather than having a specific function in transmitting syntactic relations.

A Computational Evaluation of Sentence Processing Deficits in Aphasia

Individuals with agrammatic Brocas aphasia experience difficulty when processing reversible non-canonical sentences. Different accounts have been proposed to explain this phenomenon. The Trace Deletion account (Grodzinsky, 1995, 2000, 2006) attributes this deficit to an impairment in syntactic representations, whereas others (e.g., Caplan, Waters, Dede, Michaud, & Reddy, 2007; Haarmann, Just, & Carpenter, 1997) propose that the underlying structural representations are unimpaired, but sentence comprehension is affected by processing deficits, such as slow lexical activation, reduction in memory resources, slowed processing and/or intermittent deficiency, among others. We test the claims of two processing accounts, slowed processing and intermittent deficiency, and two versions of the Trace Deletion Hypothesis (TDH), in a computational framework for sentence processing (Lewis & Vasishth, 2005) implemented in ACT-R (Anderson, Byrne, Douglass, Lebiere, & Qin, 2004). The assumption of slowed processing is operationalized as slow procedural memory, so that each processing action is performed slower than normal, and intermittent deficiency as extra noise in the procedural memory, so that the parsing steps are more noisy than normal. We operationalize the TDH as an absence of trace information in the parse tree. To test the predictions of the models implementing these theories, we use the data from a German sentence-picture matching study reported in Hanne, Sekerina, Vasishth, Burchert, and De Bleser (2011). The data consist of offline (sentence-picture matching accuracies and response times) and online (eye fixation proportions) measures. From among the models considered, the model assuming that both slowed processing and intermittent deficiency are present emerges as the best model of sentence processing difficulty in aphasia. The modeling of individual differences suggests that, if we assume that patients have both slowed processing and intermittent deficiency, they have them in differing degrees.