Величина латентного периода саккады и паттерн саккадического ответа в экспериментальной схеме «двойной шаг»
Though activation of Broca's region in the combinatorial processing of symbols (language, music) has been revealed by neurometabolic studies, most previous neurophysiological research found the earliest grammar indices in the temporal cortex, with inferior-frontal generators becoming active at relatively late stages. We use the attention- and task-free syntactic mismatch negativity (sMMN) event-related potential (ERP) to measure rapid and automatic sensitivity of the human brain to grammatical information in participants' native language (French). Further, sources underlying the MMN were estimated by applying the Parametrical Empirical Bayesian (PEB) approach, with the Multiple Sparse Priors (MSP) technique. Results showed reliable grammar-related activation focused on Broca's region already in the 150-190 ms time window, providing robust documentation of its involvement in the first stages of syntactic processing.
The goal of the present study was to investigate event-related potential (ERP) responses to Dutch negative and positive polarity adverbs of degree presented in licensed and unlicensed contexts with negative and affirmative particles directly preceding the polarity item. To control for effects of the processing of negation as such, neutral adverbs were also presented in negative and affirmative contexts. The results did not show any significant effect of negation for the non-polar adverbs, allowing context effects for polarity items to be interpreted as being due to the appropriateness of the context. Negative polarity violations elicited an N400 response that might reflect the lack of semantic congruity of the negative polarity item in an affirmative context. In contrast, processing positive polarity items in context of negation resulted in a positive effect resembling the P600, which may be considered as a marker of a different sort of integration difficulty caused by violation of licensing conditions and/or a search for a licensor in the wider discourse context. The study presented here is the first to show an unambiguous dissociation between responses to negative and positive polarity violations. This dissociation argues for different mechanisms underlying the processing of these two types of polarity; we propose that positive polarity items are sensitive to wider discourse context, while negative polarity items are more sensitive to local lexical context.
People suffering from agrammatic aphasia are known to have problems with different kinds of verbal inflection. Tense inflection is mostly more impaired than subject-verb agreementinflection. Problems with tense could either be morphosyntactic or morphosemantic in nature. Indications for the latter come from studies in which the past was found to be more impaired than present tense, even when the verbs where in their base position and both for uninflected as for inflected verbs. In the study presented here this issue is further explored, first in a grammaticality judgment task administered to agrammatic patients, then in a reaction time (RT) experiment with healthy participants.
A core issue in neurolinguistic research is to what extent the language problems that people with aphasia suffer from are specific for their brain damage. Possibly, the processes that require more cognitive resources for the healthy brain are vulnerable in aphasia. A way to tap into unimpaired language processing is to employ event-related potentials (ERPs). This study compares behavioral data from aphasic participants and ERP data from healthy participants on the time reference of verbs in Dutch.
Aphasia, a language impairment following stroke or brain trauma, is normally manifested behaviorally. Patients with the so-called non-fluent aphasia experience major difficulties at the level of morphosyntax (that is, producing and comprehending complex morphology and syntax). In contrast, patients with fluent aphasia predominantly show problems at the lexical-semantic level (that is, accessing word forms and lexical semantics). However, a few studies have proven that the language deficit in patients with aphasia is expressed not only in their linguistic performance, but also in specific electrophysiological responses.
In healthy individuals, incongruencies at different linguistic levels cause distinct event-related brain potentials (ERPs) registrated at the scalp. Syntactic incongruency elicits the ELAN and the P600 potentials, lexical-semantic incongruency elicits the N400 potential. Critically, in standard for those potentials linguistic contexts the lack of N400 was reported for fluent patients, while the lack of the ELAN and a reduced and delayed P600 – for non-fluent patients (Friederici et al. 1998, Wassenaar and Hagoort 2005). These findings support the idea of electrophysiological brain mapping on specific linguistic problems observed in different aphasia types.
The study was aimed at further investigating electrophysiological evidence for the suggestion that spoken sentence comprehension problems in individuals with fluent and non-fluent aphasia are caused, at least partly, by breakdowns at different levels of language processing – lexical-semantic and morphosyntactic respectively. To test this, we performed a study in healthy and aphasic Russian individuals using the method of event-related potentials (ERPs) that has become a powerful tool in addressing temporal aspects of language processing.
Recent studies have shown that reference to the past is more problematic in aphasic individuals than reference to the present (Anjarningsih et al. 2009; Bastiaanse, 2008). A fundamental issue concerns the extent to which past time reference difficulties are specific to aphasia. The present experiment was aimed at testing universal differences in processing present and past reference. We hypothesized that if past time reference problems are specific to aphasia, the same ERP effects should be observed while healthy individuals process verbs referring to the present and verbs referring to the past. However, if differences between present and past are more universal, non-similar ERP effects should be found.
Processing present and past time reference expressed through verbs is different in healthy individuals. Violation of the previously set time frame with a present tensed verb elicits a clear P600 response time locked to the critical verb. It means that present time reference is started being decoded and integrated into the preceding time context as soon as such it is presented. In contrast, there is no response time locked to the target verb when time frame is violated with a past tensed verb. This could be due to the fact that the proper decoding of time frame from verbal morphology does not happen right after a past tensed verb is presented. Instead, processing past time reference is delayed. These findings are in line with aphasiological data and suggest that problems with past in aphasia are based on more universal differences between processing present and past time reference.