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P Hagoort

Publications and source records attributed to P Hagoort.

At least 19 recordsLinked to original sources
PubMed2001

Electrophysiological evidence for early contextual influences during spoken-word recognition: N200 versus N400 effects.

An event-related brain potential experiment was carried out to investigate the time course of contextual influences on spoken-word recognition. Subjects were presented with spoken sentences that ended with a word that was either (a) congruent, (b) semantically anomalous, but beginning with the same initial phonemes as the congruent completion, or (c) semantically anomalous beginning with phonemes that differed from the congruent completion. In addition to finding an N400 effect in the two semantically anomalous conditions, we obtained an early negative effect in the semantically anomalous condition where word onset differed from that of the congruent completions. It was concluded that the N200 effect is related to the lexical selection process, where word-form information resulting from an initial phonological analysis and content information derived from the context interact.

Adult↗
PubMed2001

A neural correlate of syntactic encoding during speech production.

Spoken language is one of the most compact and structured ways to convey information. The linguistic ability to structure individual words into larger sentence units permits speakers to express a nearly unlimited range of meanings. This ability is rooted in speakers' knowledge of syntax and in the corresponding process of syntactic encoding. Syntactic encoding is highly automatized, operates largely outside of conscious awareness, and overlaps closely in time with several other processes of language production. With the use of positron emission tomography we investigated the cortical activations during spoken language production that are related to the syntactic encoding process. In the paradigm of restrictive scene description, utterances varying in complexity of syntactic encoding were elicited. Results provided evidence that the left Rolandic operculum, caudally adjacent to Broca's area, is involved in both sentence-level and local (phrase-level) syntactic encoding during speaking.

Adult↗
PubMed2001

Syntactic processing in left prefrontal cortex is independent of lexical meaning.

In language comprehension a syntactic representation is built up even when the input is semantically uninterpretable. We report data on brain activation during syntactic processing, from an experiment on the detection of grammatical errors in meaningless sentences. The experimental paradigm was such that the syntactic processing was distinguished from other cognitive and linguistic functions. The data reveal that in syntactic error detection an area of the left dorsolateral prefrontal cortex, adjacent to Broca's area, is specifically involved in the syntactic processing aspects, whereas other prefrontal areas subserve general error detection processes.

Adult↗
PubMed2000

An event-related brain potential analysis of visual word priming effects.

Two experiments are reported that provide evidence on task-induced effects during visual lexical processing in a prime-target semantic priming paradigm. The research focuses on target expectancy effects by manipulating the proportion of semantically related and unrelated word pairs. In Experiment 1, a lexical decision task was used and reaction times (RTs) and event-related brain potentials (ERPs) were obtained. In Experiment 2, subjects silently read the stimuli, without any additional task demands, and ERPs were recorded. The RT and ERP results of Experiment 1 demonstrate that an expectancy mechanism contributed to the priming effect when a high proportion of related word pairs was presented. The ERP results of Experiment 2 show that in the absence of extraneous task requirements, an expectancy mechanism is not active. However, a standard ERP semantic priming effect was obtained in Experiment 2. The combined results show that priming effects due to relatedness proportion are induced by task demands and are not a standard aspect of online lexical processing.

Adult↗
PubMed2000

ERP effects of listening to speech: semantic ERP effects.

In this study, event-related brain potential effects of speech processing are obtained and compared to similar effects in sentence reading. In two experiments spoken sentences were presented with semantic violations in sentence-final or mid-sentence positions. For these violations N400 effects were obtained that were very similar to N400 effects obtained in reading. However, the N400 effects in speech were preceded by an earlier negativity (N250). This negativity is not commonly observed with written input. The early effect is explained as a manifestation of a mismatch between the word forms expected on the basis of the context, and the actual cohort of activated word candidates that is generated on the basis of the speech signal.

Adult↗
PubMed2000

ERP effects of listening to speech compared to reading: the P600/SPS to syntactic violations in spoken sentences and rapid serial visual presentation.

In this study, event-related brain potential effects of speech processing are obtained and compared to similar effects in sentence reading. In two experiments sentences were presented that contained three different types of grammatical violations. In one experiment sentences were presented word by word at a rate of four words per second. The grammatical violations elicited a Syntactic Positive Shift (P600/SPS), 500 ms after the onset of the word that rendered the sentence ungrammatical. The P600/SPS consisted of two phases, an early phase with a relatively equal anterior-posterior distribution and a later phase with a strong posterior distribution. We interpret the first phase as an indication of structural integration complexity, and the second phase as an indication of failing parsing operations and/or an attempt at reanalysis. In the second experiment the same syntactic violations were presented in sentences spoken at a normal rate and with normal intonation. These violations elicited a P600/SPS with the same onset as was observed for the reading of these sentences. In addition two of the three violations showed a preceding frontal negativity, most clearly over the left hemisphere.

Adult↗
PubMed2000

Discourse before gender: an event-related brain potential study on the interplay of semantic and syntactic information during spoken language understanding.

A study is presented on the effects of discourse-semantic and lexical-syntactic information during spoken sentence processing. Event-related brain potentials (ERPs) were registered while subjects listened to discourses that ended in a sentence with a temporary syntactic ambiguity. The prior discourse-semantic information biased toward one analysis of the temporary ambiguity, whereas the lexical-syntactic information allowed only for the alternative analysis. The ERP results show that discourse-semantic information can momentarily take precedence over syntactic information, even if this violates grammatical gender agreement rules.

Adult↗
PubMed1999

The time course of grammatical and phonological processing during speaking: evidence from event-related brain potentials.

Motor-related brain potentials were used to examine the time course of grammatical and phonological processes during noun phrase production in Dutch. In the experiments, participants named colored pictures using a no-determiner noun phrase. On half of the trials a syntactic-phonological classification task had to be performed before naming. Depending on the outcome of the classifications, a left or a right push-button response was given (go trials), or no push-button response was given (no-go trials). Lateralized readiness potentials (LRPs) were derived to test whether syntactic and phonological information affected the motor system at separate moments in time. The results showed that when syntactic information determined the response-hand decision, an LRP developed on no-go trials. However, no such effect was observed when phonological information determined response hand. On the basis of the data, it can be estimated that an additional period of at least 40 ms is needed to retrieve a word's initial phoneme once its lemma has been retrieved. These results provide evidence for the view that during speaking, grammatical processing precedes phonological processing in time.

Brain↗
PubMed1999

Gender electrified: ERP evidence on the syntactic nature of gender processing.

The central issue of this study concerns the claim that the processing of gender agreement in on-line sentence comprehension is a syntactic rather than a conceptual/semantic process. This claim was tested for the grammatical gender agreement in Dutch between the definite article and the noun. Subjects read sentences in which the definite article and the noun had the same gender and sentences in which the gender agreement was violated. While subjects read these sentences, their electrophysiological activity was recorded via electrodes placed on the scalp. Earlier research has shown that semantic and syntactic processing events manifest themselves in different event-related brain potential (ERP) effects. Semantic integration modulates the amplitude of the so-called N400. The P600/SPS is an ERP effect that is more sensitive to syntactic processes. The violation of grammatical gender agreement was found to result in a P600/SPS. For violations in sentence-final position, an additional increase of the N400 amplitude was observed. This N400 effect is interpreted as resulting from the consequence of a syntactic violation for the sentence-final wrap-up. The overall pattern of results supports the claim that the on-line processing of gender agreement information is not a content driven but a syntactic-form driven process.

Adult↗
PubMed1999

Electrophysiological manifestations of open- and closed-class words in patients with Broca's aphasia with agrammatic comprehension. An event-related brain potential study.

This paper presents electrophysiological data on the on-line processing of open- and closed-class words in patients with Broca's aphasia with agrammatic comprehension. Event-related brain potentials were recorded from the scalp when Broca patients and non-aphasic control subjects were visually presented with a story in which the words appeared one at a time on the screen. Separate waveforms were computed for open- and closed-class words. The non-aphasic control subjects showed clear differences between the processing of open- and closed-class words in an early (210-375 ms) and a late (400-700 ms) time-window. The early electrophysiological differences reflect the first manifestation of the availability of word-category information from the mental lexicon. The late differences presumably relate to post-lexical semantic and syntactic processing. In contrast to the control subjects, the Broca patients showed no early vocabulary class effect and only a limited late effect. The results suggest that an important factor in the agrammatic comprehension deficit of Broca's aphasics is a delayed and/or incomplete availability of word-class information.

Adult↗
PubMed1999

Electrophysiological signatures of visual lexical processing: open- and closed-class words.

This paper presents evidence of the disputed existence of an electrophysiological marker for the lexical-categorical distinction between open- and closed-class words. Event-related brain potentials were recorded from the scalp while subjects read a story. Separate waveforms were computed for open- and closed-class words. Two aspects of the waveforms could be reliably related to vocabulary class. The first was an early negativity in the 230- to 350-msec epoch, with a bilateral anterior predominance. This negativity was elicited by open- and closed-class words alike, was not affected by word frequency or word length, and had an earlier peak latency for closed-class words. The second was a frontal slow negative shift in the 350- to 500-msec epoch, largest over the left side of the scalp. This late negativity was only elicited by closed-class words. Although the early negativity cannot serve as a qualitative marker of the open- and closed-class distinction, it does reflect the earliest electrophysiological manifestation of the availability of categorical information from the mental lexicon. These results suggest that the brain honors the distinction between open- and closed-class words, in relation to the different roles that they play in on-line sentence processing.

Adult↗
PubMed1999

The neural circuitry involved in the reading of German words and pseudowords: A PET study.

Silent reading and reading aloud of German words and pseudowords were used in a PET study using (15O)butanol to examine the neural correlates of reading and of the phonological conversion of legal letter strings, with or without meaning. The results of 11 healthy, right-handed volunteers in the age range of 25 to 30 years showed activation of the lingual gyri during silent reading in comparison with viewing a fixation cross. Comparisons between the reading of words and pseudowords suggest the involvement of the middle temporal gyri in retrieving both the phonological and semantic code for words. The reading of pseudowords activates the left inferior frontal gyrus, including the ventral part of Broca's area, to a larger extent than the reading of words. This suggests that this area might be involved in the sublexical conversion of orthographic input strings into phonological output codes. (Pre)motor areas were found to be activated during both silent reading and reading aloud. On the basis of the obtained activation patterns, it is hypothesized that the articulation of high-frequency syllables requires the retrieval of their concomitant articulatory gestures from the SMA and that the articulation of low-frequency syllables recruits the left medial premotor cortex.

Adult↗
PubMed1999

Semantic integration in sentences and discourse: evidence from the N400.

In two ERP experiments we investigated how and when the language comprehension system relates an incoming word to semantic representations of an unfolding local sentence and a wider discourse. In Experiment 1, subjects were presented with short stories. The last sentence of these stories occasionally contained a critical word that, although acceptable in the local sentence context, was semantically anomalous with respect to the wider discourse (e.g., Jane told the brother that he was exceptionally slow in a discourse context where he had in fact been very quick). Relative to coherent control words (e.g., quick), these discourse-dependent semantic anomalies elicited a large N400 effect that began at about 200 to 250 msec after word onset. In Experiment 2, the same sentences were presented without their original story context. Although the words that had previously been anomalous in discourse still elicited a slightly larger average N400 than the coherent words, the resulting N400 effect was much reduced, showing that the large effect observed in stories depended on the wider discourse. In the same experiment, single sentences that contained a clear local semantic anomaly elicited a standard sentence-dependent N400 effect (e.g., Kutas &Hillyard, 1980). The N400 effects elicited in discourse and in single sentences had the same time course, overall morphology, and scalp distribution. We argue that these findings are most compatible with models of language processing in which there is no fundamental distinction between the integration of a word in its local (sentence-level) and its global (discourse-level) semantic context.

Adult↗
PubMed1998

Brain activity during speaking: from syntax to phonology in 40 milliseconds.

In normal conversation, speakers translate thoughts into words at high speed. To enable this speed, the retrieval of distinct types of linguistic knowledge has to be orchestrated with millisecond precision. The nature of this orchestration is still largely unknown. This report presents dynamic measures of the real-time activation of two basic types of linguistic knowledge, syntax and phonology. Electrophysiological data demonstrate that during noun-phrase production speakers retrieve the syntactic gender of a noun before its abstract phonological properties. This two-step process operates at high speed: the data show that phonological information is already available 40 milliseconds after syntactic properties have been retrieved.

Adult↗
PubMed1998

Understanding ambiguous words in sentence contexts: electrophysiological evidence for delayed contextual selection in Broca's aphasia.

This study investigates whether spoken sentence comprehension deficits in Broca's aphasics results from their inability to access the subordinate meaning of ambiguous words (e.g. bank), or alternatively, from a delay in their selection of the contextually appropriate meaning. Twelve Broca's aphasics and twelve elderly controls were presented with lexical ambiguities in three context conditions, each followed by the same target words. In the concordant condition, the sentence context biased the meaning of the sentence-final ambiguous word that was related to the target. In the discordant condition, the sentence context biased the meaning of the sentence-final ambiguous word that was incompatible with the target. In the unrelated condition, the sentence-final word was unambiguous and unrelated to the target. The task of the subjects was to listen attentively to the stimuli. The activational status of the ambiguous sentence-final words was inferred from the amplitude of the N400 to the targets at two inter-stimulus intervals (ISIs) (100 ms and 1250 ms). At the short ISI, the Broca's aphasics showed clear evidence of activation of the subordinate meaning. In contrast to elderly controls, however, the Broca's aphasics were not successful at selecting the appropriate meaning of the ambiguity in the short ISI version of the experiment. But at the long ISI, in accordance with the performance of the elderly controls, the patients were able to successfully complete the contextual selection process. These results indicate that Broca's aphasics are delayed in the process of contextual selection. It is argued that this finding of delayed selection is compatible with the idea that comprehension deficits in Broca's aphasia result from a delay in the process of integrating lexical information.

Aged↗
PubMed1997

Semantic priming in Broca's aphasics at a short SOA: no support for an automatic access deficit.

This study tests the recent claim that Broca's aphasics are impaired in automatic lexical access, including the retrieval of word meaning. Subjects are required to perform a lexical decision on visually presented prime target pairs. Half of the word targets are preceded by a related word, half by an unrelated word. Primes and targets are presented with a long stimulus-onset-asynchrony (SOA) of 1400 msec and with a short SOA of 300 msec. Normal priming effects are observed in Broca's aphasics for both SOAs. This result is discussed in the context of the claim that Broca's aphasics suffer from an impairment in the automatic access of lexical-semantic information. It is argued that none of the current priming studies provides evidence supporting this claim, since with short SOAs priming effects have been reliably obtained in Broca's aphasics. The results are more compatible with the claim that in many Broca's aphasics the functional locus of their comprehension deficit is at the level of postlexical integration processes.

Adult↗
PubMed1997

Equivalent responses to lexical and nonlexical visual stimuli in occipital cortex: a functional magnetic resonance imaging study.

Stimulus-related changes in cerebral blood oxygenation were measured using high-resolution functional magnetic resonance imaging sequentially covering visual occipital areas in contiguous sections. During dynamic imaging, healthy subjects silently viewed pseudowords, single false fonts, or length-matched strings of the same false fonts. The paradigm consisted of a sixfold alternation of an activation and a control task. With pseudowords as activation vs single false fonts as control, responses were seen mainly in medial occipital cortex. These responses disappeared when pseudowords were alternated with false font strings as the control and reappeared when false font strings instead of pseudowords served as activation and were alternated with single false fonts. The string-length contrast alone, therefore, is sufficient to account for the activation pattern observed in medial visual cortex when word-like stimuli are contrasted with single characters.

Adult↗