In two studies subjects were required to read Dutch sentences that in some cases contained a syntactic violation, in other cases a semantic violation. All syntactic violations were word category violations. The design excluded differential contributions of expectancy to influence the syntactic violation effects. The syntactic violations elicited an Anterior Negativity between 300 and 500 ms. This negativity was bilateral and had a frontal distribution. Over posterior sites the same violations elicited a P600/SPS starting at about 600 ms. The semantic violations elicited an N400 effect. The topographic distribution of the AN was more frontal than the distribution of the classical N400 effect, indicating that the underlying generators of the AN and the N400 are, at least to a certain extent, non-overlapping. Experiment 2 partly replicated the design of Experiment 1, but with differences in rate of presentation and in the distribution of items over subjects, and without semantic violations. The word category violations resulted in the same effects as were observed in Experiment 1, showing that they were independent of some of the specific parameters of Experiment 1. The discussion presents a tentative account of the functional differences in the triggering conditions of the AN and the P600/SPS.
Background: Growing evidence for overlap in the syntactic processing of language and music in non-brain-damaged individuals leads to the question of whether aphasic individuals with grammatical comprehension problems in language also have problems processing structural relations in music. Aims: The current study sought to test musical syntactic processing in individuals with Broca's aphasia and grammatical comprehension deficits, using both explicit and implicit tasks. Methods & Procedures: Two experiments were conducted. In the first experiment 12 individuals with Broca's aphasia (and 14 matched controls) were tested for their sensitivity to grammatical and semantic relations in sentences, and for their sensitivity to musical syntactic (harmonic) relations in chord sequences. An explicit task (acceptability judgement of novel sequences) was used. The second experiment, with 9 individuals with Broca's aphasia (and 12 matched controls), probed musical syntactic processing using an implicit task (harmonic priming). Outcomes & Results: In both experiments the aphasic group showed impaired processing of musical syntactic relations. Control experiments indicated that this could not be attributed to low-level problems with the perception of pitch patterns or with auditory short-term memory for tones. Conclusions: The results suggest that musical syntactic processing in agrammatic aphasia deserves systematic investigation, and that such studies could help probe the nature of the processing deficits underlying linguistic agrammatism. Methodological suggestions are offered for future work in this little-explored area
An event-related brain potential experiment was carried out to investigate on-line thematic role assignment during sentence-picture matching in patients with Broca's aphasia. Subjects were presented with a picture that was followed by an auditory sentence. The sentence either matched the picture or mismatched the visual information depicted. Sentences differed in complexity, and ranged from simple active semantically irreversible sentences to passive semantically reversible sentences. ERPs were recorded while subjects were engaged in sentence-picture matching. In addition, reaction time and accuracy were measured. Three groups of subjects were tested: Broca patients (N = 10), non-aphasic patients with a right hemisphere (RH) lesion (N = 8), and healthy aged-matched controls (N = 15). The results of this study showed that, in neurologically unimpaired individuals, thematic role assignment in the context of visual information was an immediate process. This in contrast to patients with Broca's aphasia who demonstrated no signs of on-line sensitivity to the picture-sentence mismatches. The syntactic contribution to the thematic role assignment process seemed to be diminished given the reduction and even absence of P600 effects. Nevertheless, Broca patients showed some off-line behavioral sensitivity to the sentence-picture mismatches. The long response latencies of Broca's aphasics make it likely that off-line response strategies were used.
To understand spoken language requires that the brain provides rapid access to different kinds of knowledge, including the sounds and meanings of words, and syntax. Syntax specifies constraints on combining words in a grammatically well formed manner. Agrammatic patients are deficient in their ability to use these constraints, due to a lesion in the perisylvian area of the languagedominant hemisphere. We report a study on real-time auditory sentence processing in agrammatic comprehenders, examining their ability to accommodate damage to the language system. We recorded event-related brain potentials (ERPs) in agrammatic comprehenders, nonagrammatic aphasics, and age-matched controls. When listening to sentences with grammatical violations, the agrammatic aphasics did not show the same syntax-related ERP effect as the two other subject groups. Instead, the waveforms of the agrammatic aphasics were dominated by a meaning-related ERP effect, presumably reflecting their attempts to achieve understanding by the use of semantic constraints. These data demonstrate that although agrammatic aphasics are impaired in their ability to exploit syntactic information in real time, they can reduce the consequences of a syntactic deficit by exploiting a semantic route. They thus provide evidence for the compensation of a syntactic deficit by a stronger reliance on another route in mapping sound onto meaning. This is a form of plasticity that we refer to as multiple-route plasticity. In listening to language, qualitatively different syntactic and semantic constraints are combined to derive the message from the speech signal. The basic distinction between syntax and semantics can be observed in electrophysiological recordings of brain activity, where this distinction is reflected in two qualitatively different brain signals: the P600͞SPS and the N400, respectively (1-4). In this study, we used these two languagerelated event-related brain potential (ERP) effects to investigate the language deficit of agrammatic comprehenders and the nature of possible compensatory processes resulting from brain damage.It is a well established finding in the ERP literature on language comprehension that varying the meaning relation between words affects the amplitude of a negative-going potential with an onset at Ϸ250 ms and a maximal amplitude at Ϸ400 ms after word onset. This potential is known as the N400. Although the grammatical structure of the sentence ''The pizza is too hot to drink'' is identical to that of the sentence ''The pizza is too hot to eat,'' drink elicits a larger negative-going potential than eat because of the semantic mismatch between drink and the sentence context. The amplitude of the N400 is a sensitive manifestation of the binding of word meanings into an overall interpretation of the utterance (3, 5, 6). In aphasia research, this ERP component has been used to track real-time comprehension deficits in brain-damaged patients, where it has revealed processing deficiencies in the time course of meaning activation and integr...
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