Biomedical subjects

A D Friederici

Publications and source records attributed to A D Friederici.

At least 55 records · Page 3Linked to original sources

PubMed1999

Processing of syntactic information monitored by brain surface current density mapping based on MEG.

The cortical network subserving language processing is likely to exhibit a high spatial and temporal complexity. Studies using brain imaging methods, like fMRI or PET, succeeded in identifying a number of brain structures that seem to contribute to the processing of syntactic structures, while their dynamic interaction remains unclear due to the low temporal resolution of the methods. On the other hand, ERP studies have revealed a great deal of the temporal dimension of language processing without being able to provide more than very coarse information on the localisation of the underlying generators. MEG has a temporal resolution similar to EEG combined with a better spatial resolution. In this paper, Brain Surface Current Density (BSCD) mapping in a standard brain model was used to identify statistically significant differences between the activity of certain brain regions due to syntactically correct and incorrect auditory language input. The results show that the activity in the first 600 ms after violation onset is mainly concentrated in the temporal cortex and the adjacent frontal and parietal areas of both hemispheres. The statistical analysis reveals significantly different activity mainly in both frontal and temporal cortices. For longer latencies above 250 ms, the differential activity is more prominent in the right hemisphere. These findings confirm other recent results that suggest right hemisphere involvement in auditory language processing. One interpretation might be that right hemisphere regions play an important role in repair and re-analysis processes in order to free the specialised left hemisphere language areas for processing further input.

Adult↗

PubMed1999

Brain potentials indicate immediate use of prosodic cues in natural speech processing.

Spoken language, in contrast to written text, provides prosodic information such as rhythm, pauses, accents, amplitude and pitch variations. However, little is known about when and how these features are used by the listener to interpret the speech signal. Here we use event-related brain potentials (ERP) to demonstrate that intonational phrasing guides the initial analysis of sentence structure. Our finding of a positive shift in the ERP at intonational phrase boundaries suggests a specific on-line brain response to prosodic processing. Additional ERP components indicate that a false prosodic boundary is sufficient to mislead the listener's sentence processor. Thus, the application of ERP measures is a promising approach for revealing the time course and neural basis of prosodic information processing.

Brain↗

PubMed1999

Language related brain potentials in patients with cortical and subcortical left hemisphere lesions.

The role of the basal ganglia in language processing is currently a matter of discussion. Therefore, patients with left frontal cortical and subcortical lesions involving the basal ganglia as well as normal controls were tested in a language comprehension paradigm. Semantically incorrect, syntactically incorrect and correct sentences were presented auditorily. Subjects were required to listen to the sentences and to judge whether the sentence heard was correct or not. Event-related potentials and reaction times were recorded while subjects heard the sentences. Three different components correlated with different language processes were considered: the so-called N400 assumed to reflect processes of semantic integration; the early left anterior negativity hypothesized to reflect processes of initial syntactic structure building; and a late positivity (P600) taken to reflect second-pass processes including re-analysis and repair. Normal participants showed the expected N400 component for semantically incorrect sentences and an early anterior negativity followed by a P600 for syntactically incorrect sentences. Patients with left frontal cortical lesions displayed an attenuated N400 component in the semantic condition. In the syntactic condition only a late positivity was observed. Patients with lesions of the basal ganglia, in contrast, showed an N400 to semantic violations and an early anterior negativity as well as a P600 to syntactic violations, comparable to normal controls. Under the assumption that the early anterior negativity reflects automatic first-pass parsing processes and the P600 component more controlled second-pass parsing processes, the present results suggest that the left frontal cortex might support early parsing processes, and that specific regions of the basal ganglia, in contrast, may not be crucial for early parsing processes during sentence comprehension.

Adult↗

PubMed1999

The functional neuroanatomy of novelty processing: integrating ERP and fMRI results.

Recent research indicates that non-tonal novel events, deviating from an ongoing auditory environment, elicit a positive event-related potential (ERP), the novel P3. Although a variety of studies examined the neural network engaged in novelty detection, there is no complete picture of the underlying brain mechanisms. This experiment investigated these neural mechanisms by combining ERP and functional magnetic resonance imaging (fMRI). Hemodynamic and electrophysiological responses were measured in the same subjects using the same experimental design. The ERP analysis revealed a novel P3, while the fMRI responses showed bilateral foci in the middle part of the superior temporal gyrus. When subjects attended to the novel stimuli only identifiable novel sounds evoked a N4-like negativity. Subjects showing a strong N4-effect had additional fMRI activation in right prefrontal cortex (rPFC) as compared to subjects with a weak N4-effect. This pattern of results suggests that novelty processing not only includes the registration of deviancy but may also lead to a fast access and retrieval of related semantic concepts. The fMRI activation pattern suggests that the superior temporal gyrus is involved in novelty detection, whereas accessing and retrieving semantic concepts related to novel sounds additionally engages the rPFC.

Acoustic Stimulation↗

PubMed1999

Electrophysiological evidence for two steps in syntactic analysis. Early automatic and late controlled processes.

In this study we examined the properties of the processes involved in the structural analysis of sentences using event-related brain potential measures (ERP). Previous research had shown two ERP components to correlate with phrase structure violations: an early left anterior negativity (ELAN), which is assumed to reflect first-pass parsing processes, and a late parietally distributed positivity (P600), assumed to reflect second-pass parsing processes. We hypothesized that the first-pass parsing processes are highly automatic, whereas second-pass parsing processes are more controlled. To test this hypothesis we varied the proportion of correct sentences and sentences containing phrase structure violations with incorrect sentences being either of a low (20% violation) or a high (80% violation) proportion. Results showed that the early left anterior negativity was elicited and equally pronounced under both proportion conditions. By contrast, the late positivity was elicited for a low proportion of incorrect sentences only. This data pattern suggests that first-pass parsing processes are automatic, whereas second-pass parsing processes are under participants' strategic control.

Acoustic Stimulation↗

PubMed1999

Lexical integration: sequential effects of syntactic and semantic information.

Both semantic and syntactic context constraints can influence word processing at the level of lexical integration. In event-related brain potentials (ERPs), semantic integration is reflected by a negativity around 400 msec (N400), whereas phrase structure assignment and syntactic integration are assumed to be reflected by an early left anterior negativity and a late positivity (P600), respectively. An ERP study is presented in which participants read different types of sentences whose terminal verb was either congruent with the preceding context or incongruent due to a phrase structure violation, a semantic violation, or both. The main finding was that only the pure semantic violation condition, but not the combined semantic and syntactic violation condition, elicited a large N400. The two conditions containing phrase structure violations were predominantly characterized by a P600. Both semantic violation conditions, moreover, displayed a late negativity around 700 msec that overlapped with the P600 in the double violation condition. The absence of an N400 effect for elements that are syntactically as well as semantically incongruent with prior context suggests an early influence of phrase structure information on processes of lexical-semantic integration. The present data are discussed in comparison to previous ERP findings, and a new view of lexical integration processes is proposed.

Adult↗

PubMed1998

First-pass versus second-pass parsing processes in a Wernicke's and a Broca's aphasic: electrophysiological evidence for a double dissociation.

The present paper is a first attempt to integrate the classical brain lesion behavioral impairment approach of functional neuroanatomy and the electrophysiological brain mapping approach in the domain of syntactic processing. In a group of normal age-matched controls we identified three electrophysiological components previously observed in correlation with language comprehension processes: an early left anterior negativity normally seen in correlation with syntactic first-pass parsing processes (ELAN), a centroparietal negativity seen in correlation with processes of lexical-semantic integration (N400), and a late centroparietal positivity observed in correlation with secondary syntactic processes of reanalysis and repair (P600). The early left anterior negativity was absent in a patient with an extended lesion in the anterior part of the left hemisphere sparing the temporal lobe, although the late centroparietal positivity and the centroparietal N400 were present. In a patient with a left temporal-parietal lesion the early left anterior negativity was found to be present, whereas the N400 component was absent. These findings suggest that first-pass parsing and secondary processes are subserved by distinct brain systems.

Adult↗

PubMed1998

Structural prominence and agrammatic theta-role assignment: a reconsideration of linear strategies.

In this paper we examine the tendency for agrammatic aphasics to make thematic reversal errors in comprehension, e.g., a tendency for English-speaking agrammatics to assign a preposed object the subject role. Although this tendency has been argued to follow from either a linear (Grodzinsky, 1995) or a directionality (Hagiwara & Caplan, 1990) strategy, we show that such proposals can, at best, function as language-particular strategies. We examine data from English, Japanese, German and Dutch, and propose a Structural Prominence Hypothesis which captures the following cross-linguistic generalization: thematic reversal errors result from a tendency to assign thematic roles based on the relative structural prominence of the candidate NPs.

Aphasia, Broca↗

PubMed1998

Double dissociation of processing temporal and spatial information in working memory.

Based on the converging evidence supporting the view of domain specific object and spatial working memory processes, the question was addressed whether the property of domain specificity holds equally for temporal information. Using a selective interference paradigm the objective was to test a dissociation of the processing of temporal duration and spatial location information in working memory of intact human subjects. Subjects performed a temporal and a spatial memory task in which they were required to indicate whether the study and the test stimuli were the same or different in duration (temporal memory) or in location (spatial memory) as primary tasks. Both primary tasks were combined with three types of interference tasks, a spatial classification memory task, a temporal classification memory task and a non-interference baseline task--to be performed in-between the presentation of study and test stimuli. Memory for temporal duration was shown to be impaired by the temporal classification task but not by the spatial classification task; memory for spatial position showed the opposite pattern of impairment. These data thus provide evidence for the view that temporal and spatial working memory contents are subject to selective interference, reflecting a functional dissociation in the processing of temporal duration and spatial location information. The results are interpreted as evidence for the domain specificity in the processing of temporal information in working memory.

Adult↗

PubMed1998

Working memory constraints on syntactic ambiguity resolution as revealed by electrical brain responses.

Parsing strategies in temporarily ambiguous sentences were investigated in readers with different sentence memory capacities using event-related brain potentials (ERPs). Readers with a high memory span as well as readers with a low memory span were required to read subject and object relative sentences which were either ambiguous until the last word (late disambiguation) or were disambiguated by case marking either the clause initial pronoun (immediate disambiguation) or the noun phrase following it (early disambiguation). ERPs registered during sentence reading elicited the following effects: In the late disambiguation condition, high span readers, but not low span readers, displayed a more positive going wave at the disambiguating number marked auxiliary for the object relative sentences than for the subject relative sentences. This positivity is taken to reflect processes of revision that become necessary at the disambiguating element if the initial structure considered is a subject relative clause. When case marking was available in the clause initial at the relative pronoun, both high and low span readers showed a positivity at the disambiguating element for the object relative sentences, suggesting the immediate use of case marking information for revision. When case marking was available in the noun phrase following an ambiguous pronoun both groups showed no clear effect of revision at the disambiguating element, but only at the sentence final number marked auxiliary. This non-immediate use of the case marking information seems to be due to an inherent ambiguity in the German case marking system which interacts with the disambiguating element's position in the sentence. The combined data indicate that morphological information can be used immediately by high and low span readers to resolve syntactic ambiguity during sentence processing whenever the information given is clearly unambiguous. In addition they suggest that possible processing differences in ambiguity resolution between high and low span readers may only appear when the ambiguous regions are long.

Adult↗

PubMed1998

Magnetic field tomography analysis of continuous speech.

In this article we investigate MEG correlates of syntactic violations in continuous speech. An early left anterior negativity (ELAN) has been reported in previous EEG studies and has been related to syntactic processing. We used Magnetic Field Tomography (MFT) to extract a 3D estimate of the current density distribution J, from MEG data recorded while subjects listened to continuous speech. Separate estimates were obtained from the activity associated with the first word of the sentence, and the last words of the sentence which signified syntactic violation, semantic violation or correct sentences. In each case independent 3D MFT estimates of activity were obtained 2 ms apart. After converting the solutions into a PET-like format we perform a statistical analysis on a voxel-by-voxel basis. Visual inspection of the power of J at the time of the ELAN component and the statistical maps overlaid on the individual anatomical MRI suggests generators in the vicinity of the auditory cortex and in left frontal regions. Directional activation curves are computed to show the variation of activity as a function of time, from well circumscribed areas. The activation curve for the auditory cortex has a characteristic pattern consisting of three peaks, seen in the average time-locked to the onset of the first word, and the critical word of the syntactic violation. The left auditory cortex shows a delay of about 30 ms in the syntactic violation condition compared to the first word condition. No such delay is seen in the right auditory cortex.

Adult↗

PubMed1998

Context effects in visual word recognition: lexical relatedness and syntactic context.

In three experiments, we investigated how associative word-word priming effects in German depend on different types of syntactic context in which the related words are embedded. The associative relation always concerned a verb as prime and a noun as target. Prime word and target word were embedded in visually presented strings of words that formed either a correct sentence, a scrambled list of words, or a sentence in which the target noun and the preceding definite article disagreed in syntactic gender. In contrast to previous studies (O'Seaghdha, 1989; Simpson, Peterson, Casteel, & Burgess, 1989), associative priming effects were not only obtained in correct sentences but also in scrambled word lists. Associative priming, however, was not obtained when the definite article and the target noun disagreed in syntactic gender. The latter finding suggests that a rather local violation of syntactic coherence reduces or eliminates word-word priming effects. The results are discussed in the context of related work on the effect of gender dis-/agreement between a syntactic context and a target noun.

Adult↗

PubMed1997

Semantic aspects of novelty detection in humans.

The ability to detect unusual and novel events is an important prerequisite for storage of information in memory. Non-tonal novel sounds that deviate from an ongoing auditory environment elicit a positive event-related potential (ERP) component, the so-called novel P3. Though there is converging evidence on the neuronal network engaged in novelty detection, little attention has been paid to the properties of novel sounds, such as their typicality or relationship to mental concepts. Here we report the ERPs evoked by two types of generically novel stimuli, namely identifiable (meaningful) and non-identifiable (non-meaningful) novel sounds. The ERP analysis revealed a novel P3 for both types of sounds. However, when subjects actively attended to the stimuli only identifiable novel sounds evoked a right-lateralized negativity (N4) that peaked shortly after the novel P3. We conclude that novelty detection not only includes the registration of deviancy but also fast access and identification of related semantic concepts.

Adult↗

PubMed1997

Electrophysiological correlates of temporal and spatial information processing.

In order to study the neurophysiological correlates of working memory for different types of information, event-related brain potentials (ERPs) were recorded during a visual spatial and visual as well as auditory duration memory tasks. From stimulus onset to 500 ms ERPs were distinguishable by allocation to visual or auditory modality. From 500 to 2000 ms after stimulus onset, the spatial task generated a parieto-occipital focused negative slow wave, while corresponding ERPs of the temporal task showed a negative slow wave with frontolateral focus. From 1200 to 5500 ms a large positivity was found for the auditory temporal task and for good performers of the visual temporal task. The data suggest a distinction of three processing phases: modality-specific encoding, information-specific encoding and retention in conjunction with modality-specific inhibition processes.

Acoustic Stimulation↗

PubMed1997

Neurophysiological aspects of language processing.

Neurophysiological studies of language processing in the intact brain have identified 3 major event-related potential (ERP) components correlating with different aspects of language: (1) an early left anterior negativity (ELAN) obtained in correlation with early syntactic processes, primarily processes of structuring the language input, (2) a centroparietal negativity around 400 ms (N400) reflecting lexicalsemantic integration processes, and (3) a late centroparietal positivity (P600) observed in correlation with secondary syntactic processes such as reanalysis and repair. These components manifest themselves approximately around 200 ms, 400 ms and 600 ms post onset of a critical word. Their variation in latency and magnitude can be used as a diagnostic criterion for language impairment.

Electroencephalography↗

PubMed1997

[Probability and strategy: an event-related potential study of processing syntactic anomalies].

Syntactic ambiguities requiring additional processing usually elicit positive going waveforms with onset latencies between 300 and 600 ms in the event-related potential (ERP). It is still unclear to what extent these components can be viewed either (a) as language specific in nature or (b) as members of the domain-unspecific P300 family of components. The present study investigates this question by means of probability manipulations applied to German sentences with subject-object ambiguities. Non-preferred object-subject (OS) word order requires structural revisions whereas the initially preferred subject-object (SO) word order does not. In the present experiment, the proportions of OS and SO structures were varied across experimental blocks (i.e., .25/.75 vs. .75/.25). The data of 20 participants reveal that ERP components were predominantly influenced when the subjects were explicitly informed about the actual proportions before each single block. In this case an early frontal positive component at about 400 ms and a subsequent posterior positivity were elicited by rare sentence structures irrespective of word order, suggesting that sentence processing was under strategic control. Conversely, participants that were not informed about sentence proportions showed larger positivities to the unpreferred OS sentences. Probability manipulations did not affect this pattern significantly. The data suggest that positivities evoked by syntactic ambiguities respond differently to probability manipulations than the P300 component.

Adult↗

PubMed1997

[Electrophysiologic dissociations in memory encoding of abstract and concrete words].

This study examined memory encoding of auditorily presented abstract and concrete nouns. 22 subjects performed various blocks of a free recall memory task in which lists of 22 either abstract or concrete words had to be memorized. Consistent with a large variety of memory studies, recall performance was better for concrete than for abstract words. When the event-related potentials (ERPs) recorded during study were selectively averaged for those words that were subsequently recalled and those subsequently not recalled, the ERPs were more positive going for words that were subsequently recalled. These Dm effects (Difference due to memory) started around 500 ms post-stimulus and differed in timing and scalp topography for both types of words: For abstract words, they were present in an early (i.e., 600 to 1100 ms) time interval at parieto-occipital electrodes only. In contrast, for concrete words, Dm effects were obtained with a broad topographic distribution in the 600 to 1000 ms time range and were also present in a late time interval (1100 to 1600 ms) at fronto-central recording sites. The topographical dissociations of the Dm effects in the early time interval are taken to reflect the larger distinctiveness of concrete words during encoding, whereas the late effects presumably play a functional role in elaborative processing of concrete words. The results do not agree with models of word concreteness that propose separate processing systems for the two types of words, and rather support those models that propose quantitative differences in the processing of abstract and concrete words.

Adult↗

PubMed1996

Syntactic parsing as revealed by brain responses: first-pass and second-pass parsing processes.

This paper reviews a series of electrophysiological experiments on syntactic processing against the background of a psycholinguistic two-stage model of parsing. The data reveal two event-related brain potential components in correlation with syntactic processes: an early left anterior negativity and a late centro-parietal positivity. It is argued that these two components can be correlated with two separate stages of syntactic processing: the early left anterior negativity reflecting first-pass parsing processes and the late positivity reflecting second-pass parsing processes possibly including processes of reanalyses.

Adult↗