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Wernicke's 1903 case pure agraphia : an enigma for classical models of written language processing
(1996)
The processing of nonverbal auditory stimuli has not yet been sufficiently investigated in patients with aphasia. On the basis of a duration discrimination task, we examined whether patients with left-sided cerebrovascular lesions were able to perceive time differences in the scale of approximately 150ms. Further linguistic and memory-related tasks were used to characterize more exactly the relationships in the performances between auditory nonverbal task and selective linguistic or mnemonic disturbances. All examined conduction aphasics showed increased thresholds in the duration discrimination task. The low thresholds on this task were in a strong correlative relation to the reduced performances in repetition and working memory task. This was interpreted as an indication of a pronounced disturbance in integrating auditory verbal information into a long-term window (sampling disturbance) resulting in an additional load of working memory. In order to determine the lesion topography of patients with sampling disturbances, the anatomical and psychophysical data were correlated on the basis of a voxelwise statistical approach. It was found that tissue damage extending through the insula, the posterior superior temporal gyrus, and the supramarginal gyrus causes impairments in sequencing of time-sensitive information.
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
Most studies investigating the impact of literacy on oral language processing have shown that literacy provides phonological awareness skills in the processing of oral language. The implications of these results on aphasia tests could be significant and pose questions on the adequacy of such tools for testing non-literate individuals. Aiming at examining the impact of literacy on oral language processing and its implication on aphasia tests, this study tested 12 non-literate and 12 literate individuals with a modified Amharic version of the Bilingual Aphasia Test (Paradis and Amberber, 1991, Bilingual Aphasia Test. Amharic version. Hillsdale, NJ: Lawrence Erlbaum.). The problems of phonological awareness skills in oral language processing in non-literates are substantiated. In addition, compared with literate participants, non-literate individuals demonstrated difficulties in the word/sentence-picture matching tasks. This study has also revealed that the Amharic version of the Bilingual Aphasia Test may be viable for testing Amharic-speaking non-literate individuals with aphasia when modifications are incorporated.
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
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.
Rapid recovery of aphasia and deep dyslexia after extensive left-hemisphere damage in childhood
(1994)
Background: While the role of the right hemisphere (RH) in prosodic processing is prominent, research on the perception of lexical tones has shown that left hemisphere damaged (LHD) patients are more impaired than right hemisphere damaged (RHD) patients. Dichotic listening and imaging studies with healthy speakers of tone languages demonstrate that at least at the phonemic and lexical level, prosody is processed in the left hemisphere (LH) when the variations in pitch are phonemically distinctive. There is no report available yet on the perceptual discrimination of a Bantu language in patients after unilateral brain damage. Aims: We addressed the question of how well Shona aphasic patients and right hemisphere damaged patients perceive pitch contrasts in Shona lexical words and also in their homologous low-pass filtered counterparts. We also sought to discover the validity of the current hypotheses on hemispheric lateralisation particularly the hypothesis on hemispheric lateralisation based on language function to account for the Shona data. Methods Procedures: A total of 7 LHD and 7 RHD patients and 14 healthy controls participated in two discrimination tasks that examined perception of lexical tone in (a) bisyllabic Shona words and (b) low-pass filtered stimuli. In both tasks the participants were tasked with judging the pitch as the same or different in 120 bisyllabic words and 120 low-pass filtered stimuli. Outcomes Results: The results demonstrated that the tonal discrimination of the LHD group was more reduced in comparison to the RHD group and control participants. However, the performance of the RHD patients was not error free relative to the control participants, although significantly better than the LHD patients in both tasks. Conclusions: At least for the phonemic and lexical levels, brain damage to the dominant hemisphere results in lexical tone impairment for LHD patients, and cognitive load processing results in a subdued but good performance for RHD patients. The LH is therefore dominant for processing tone when it is lexically distinctive.
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
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 Broca's 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 Broca's 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 Broca's area in processing antecedent-gap relations was not found. Moreover, the posterior part of Broca's area was conjointly activated by both sentence conditions. Broca's 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. (C) 2004 Wiley-Liss, Inc