Biomedical subjects

Thomas C Gunter

Publications and source records attributed to Thomas C Gunter.

17 recordsLinked to original sources

PubMed2005

Zooming into L2: global language context and adjustment affect processing of interlingual homographs in sentences.

In a semantic priming study, we investigated the processing of German-English homographs such as gift (German = "poison", English = "present") in sentence contexts using a joint reaction time (RT)/event-related brain potential (ERP) measure. Native German speakers with intermediate or advanced knowledge of English (N = 48) performed an all-L2 (English) experiment where sentences such as "The woman gave her friend an expensive gift" (control prime: item) were presented, followed by targets (i.e., boss) for lexical decision. To test the role of global task effects during sentence processing, we presented half the participants (N = 24) with a 20-min silent film narrated in German and half (N = 24) with the film in English before the experiment. To address the development of task effects over time, we analyzed the first and second blocks of the experiment. The results showed a significant interaction between semantic priming, movie version, and block in both the RTs and ERPs: there was significant semantic priming in the RTs and modulations in the N200 and N400 components only for participants who viewed the German movie, and only during the first block. Results suggest that in an all-L2 sentence task with L2 pre-task priming (English film), decision thresholds are raised high enough to eliminate measurable influence of the L1 on the L2. Despite identical material, participants who viewed the German film had to adjust, or zoom in, to the all-L2 task. Implications of this zooming in process in are discussed in terms of the recent Bilingual Interactive Activation (BIA+) model of bilingual word recognition [T. Dijkstra, W.J.B. Van Heuven, The architecture of the bilingual word recognition system: from identification to decision, Bilingualism: Lang. Cogn. 5 (2002) 175-197].

Adaptation, Psychological↗

PubMed2005

Action comprehension: deriving spatial and functional relations.

A perceived action can be understood only when information about the action carried out and the objects used are taken into account. It was investigated how spatial and functional information contributes to establishing these relations. Participants observed static frames showing a hand wielding an instrument and a potential target object of the action. The 2 elements could either match or mismatch, spatially or functionally. Participants were required to judge only 1 of the 2 relations while ignoring the other. Both irrelevant spatial and functional mismatches affected judgments of the relevant relation. Moreover, the functional relation provided a context for the judgment of the spatial relation but not vice versa. The results are discussed in respect to recent accounts of action understanding.

Adult↗

PubMed2005

Semantic memory retrieval: cortical couplings in object recognition in the N400 window.

To characterize the regional changes in neuronal couplings and information transfer related to semantic aspects of object recognition in humans we used partial-directed EEG-coherence analysis (PDC). We examined the differences of processing recognizable and unrecognizable pictures as reflected by changes in cortical networks within the time-window of a determined event-related potential (ERP) component, namely the N400. Fourteen participants performed an image recognition task, while sequentially confronted with pictures of recognizable and unrecognizable objects. The time-window of N400 as indicative of object semantics was defined from the ERP. Differences of PDC in the beta-band between these tasks were represented topographically as patterns of electrical couplings, possibly indicating changing degrees of functional cooperation between brain areas. Successful memory retrieval of picture meaning appears to be supported by networks comprising left temporal and parietal regions and bilateral frontal brain areas.

Adult↗

PubMed2005

Brain responses to segmentally and tonally induced semantic violations in Cantonese.

The present event-related potential (ERP) study examined the role of tone and segmental information in Cantonese word processing. To this end, participants listened to sentences that were either semantically correct or contained a semantically incorrect word. Semantically incorrect words differed from the most expected sentence completion at the tone level, at the segmental level, or at both levels. All semantically incorrect words elicited an increased frontal negativity that was maximal 300 msec following word onset and an increased centroparietal positivity that was maximal 650 msec following word onset. There were differences between completely incongruous words and the other two violation conditions with respect to the latency and amplitude of the ERP effects. These differences may be due to differences in the onset of acoustic deviation of the presented from the expected word and different mechanisms involved in the processing of complete as compared to partial acoustic deviations. Most importantly, however, tonally and segmentally induced semantic violations were comparable. This suggests that listeners access tone and segmental information at a similar point in time and that both types of information play comparable roles during word processing in Cantonese.

Acoustic Stimulation↗

PubMed2004

Communicating hands: ERPs elicited by meaningful symbolic hand postures.

Meaningful and meaningless hand postures were presented to subjects who had to carry out a semantic discrimination task while electrical brain responses were recorded. Both meaningful and control sets of hand postures were matched as closely as possible. The ERPs elicited by meaningless hand postures showed an anteriorly distributed N300 and a centro-posteriorly distributed N400 component. The N300 probably reflects picture-specific processes, whereas the N400-effect probably reflects processing in an amodal semantic network. The scalp-distribution of the N400-effect, which is more posterior than usually reported in picture processing, suggests that the semantic representations of the concepts expressed by meaningful hand postures have similar properties to those of abstract words.

Adult↗

PubMed2004

Lexical memory search during N400: cortical couplings in auditory comprehension.

In this study, we applied partial-directed EEG-coherence analysis to assess regional changes in neuronal couplings and information transfer related to semantic processing. We tested the hypothesis whether (and which) processing differences between spoken words and pseudowords are reflected by changes in cortical networks within the time window of a specific event related potential (ERP) component, the N400. Fourteen native speaking German subjects performed a lexical decision paradigm, while being confronted sequentially with two-syllabic nouns and phonologically legal pseudowords. Using ERP analysis, we defined the time window of the N400 effect, known to reflect semantic processing, and, subsequently, we examined the coupling differences. Lexico-semantic memory search appears to be subserved by a network between temporal, parietal and frontal areas, particularly restricted to the left hemisphere.

Acoustic Stimulation↗

PubMed2004

Action-effect coupling in pianists.

Recent theories have stressed the role of effect anticipation in action control. Such a mechanism requires the prior acquisition of integrated action-effect associations. The strength of such associations should directly depend on the amount of learning, and therefore be most pronounced in motor experts. Using an interference paradigm, we investigated whether evidence of such representations can be demonstrated in expert pianists. Participants were required to play chords on a keyboard in response to imperative visual stimuli. Concurrently, task-irrelevant auditory stimuli ("potential" action effects) were presented that were congruent or incongruent with the chords to be played. In Experiment 1 we found evidence that expert pianists, compared with non-musicians, have acquired such action-effects representations. Response times were slower when the auditory stimulus was incongruent with the required response. In order to ascertain the locus of interference, we varied imperative stimuli and responses in Experiments 2 and 3. The results indicate that, for the most part, interference occurs on the response level rather than on an abstract level. However, the perception of action effects also evokes processing of abstract features, like the concept of major-minor mode.

Acoustic Stimulation↗

PubMed2004

Cooperation of different neuronal systems during hand sign recognition.

Hand signs with symbolic meaning can often be utilized more successfully than words to communicate an intention; however, the underlying brain mechanisms are undefined. The present study using magnetoencephalography (MEG) demonstrates that the primary visual, mirror neuron, social recognition and object recognition systems are involved in hand sign recognition. MEG detected well-orchestrated multiple brain regional electrical activity among these neuronal systems. During the assessment of the meaning of hand signs, the inferior parietal, superior temporal sulcus (STS) and inferior occipitotemporal regions were simultaneously activated. These three regions showed similar time courses in their electrical activity, suggesting that they work together during hand sign recognition by integrating information in the ventral and dorsal pathways through the STS. The results also demonstrated marked right hemispheric predominance, suggesting that hand expression is processed in a manner similar to that in which social signs, such as facial expressions, are processed.

Adult↗

PubMed2004

Determining inhibition: Individual differences in the 'lexicon context' trade-off during lexical ambiguity resolution in working memory.

The current experiment assessed the relation between inhibitory mechanisms underlying language processing in working memory (WM) and the influence of a postulated internal cognitive trade-off between lexicon and context factors driving inhibition in sentence processing. Participants with high and low WM span (Daneman & Carpenter, 1980) were presented with sentences that began with an ambiguous noun (being both homographic and homophonic). A cue towards the relevant meaning of the ambiguous word was presented three words later by another noun. Immediately after the cue, a verb was presented that finally disambiguated the ambiguous noun. In half of the cases, the final disambiguation was congruent with the disambiguation cue. In the other half, subjects had to realize that it was not the cued but the other meaning, which turned out to be relevant in the actual sentence. This experimental paradigm was identical to the one used in Gunter et al. (2003). In contrast to the original experiment, the filler items in the present study were unambiguous. Both groups showed a smaller N400 component for the cue related to the dominant as compared to the subordinate meaning, suggesting that the dominant meaning was more active in WM than the subordinate one. In the original experiment, only the high-span subjects manifested this effect. Thus, a change in the global experimental setting changed the use of WM-related inhibitory processes. Data also suggest that, as a default strategy, the lexicon-context trade-off of high-span subjects relies more on lexicon information than does that of low-span subjects.

Adult↗

PubMed2004

Sequential effects of increasing propofol sedation on frontal and temporal cortices as indexed by auditory event-related potentials.

BACKGROUND: It is an open question whether cognitive processes of auditory perception that are mediated by functionally different cortices exhibit the same sensitivity to sedation. The auditory event-related potentials P1, mismatch negativity (MMN), and early right anterior negativity (ERAN) originate from different cortical areas and reflect different stages of auditory processing. The P1 originates mainly from the primary auditory cortex. The MMN is generated in or in the close vicinity of the primary auditory cortex but is also dependent on frontal sources. The ERAN mainly originates from frontal generators. The purpose of the study was to investigate the effects of increasing propofol sedation on different stages of auditory processing as reflected in P1, MMN, and ERAN. METHODS: The P1, the MMN, and the ERAN were recorded preoperatively in 18 patients during four levels of anesthesia adjusted with target-controlled infusion: awake state (target concentration of propofol 0.0 microg/ml), light sedation (0.5 microg/ml), deep sedation (1.5 microg/ml), and unconsciousness (2.5-3.0 microg/ml). Simultaneously, propofol anesthesia was assessed using the Bispectral Index. RESULTS: Propofol sedation resulted in a progressive decrease in amplitudes and an increase of latencies with a similar pattern for MMN and ERAN. MMN and ERAN were elicited during sedation but were abolished during unconsciousness. In contrast, the amplitude of the P1 was unchanged by sedation but markedly decreased during unconsciousness. CONCLUSION: The results indicate differential effects of propofol sedation on cognitive functions that involve mainly the auditory cortices and cognitive functions that involve the frontal cortices.

Acoustic Stimulation↗

PubMed2004

ERPs reflect lexical identification in word fragment priming.

Behavioral evidence suggests that spoken word recognition involves the temporary activation of multiple entries in a listener's mental lexicon. This phenomenon can be demonstrated in cross-modal word fragment priming (CMWP). In CMWP, an auditory word fragment (prime) is immediately followed by a visual word or pseudoword (target). Experiment 1 investigated ERPs for targets presented in this paradigm. Half of the targets were congruent with the prime (e.g., in the prime-target pair: AM-AMBOSS [anvil]), half were not (e.g., AM-PENSUM [pensum]). Lexical entries of the congruent targets should receive activation from the prime. Thus, lexical identification of these targets should be facilitated. An ERP effect named P350, two frontal negative ERP deflections, and the N400 were sensitive to prime-target congruency. In Experiment 2, the relation of the formerly observed ERP effects to processes in a modality-independent mental lexicon was investigated by presenting primes visually. Only the P350 effect could be replicated across different fragment lengths. Therefore, the P350 is discussed as a correlate of lexical identification in a modality-independent mental lexicon.

Adolescent↗

PubMed2003

Working memory and lexical ambiguity resolution as revealed by ERPs: a difficult case for activation theories.

This series of three event-related potential experiments explored the issue of whether the underlying mechanism of working memory (WM) supporting language processing is inhibitory or activational in nature. These different cognitive mechanisms have been proposed to explain the more efficient processing of subjects with a high WM span compared to those with a low WM span. Participants with high and low WM span were presented with sentences containing a homonym followed three words later by a nominal disambiguation cue and a final disambiguation using a verb. At the position of the disambiguation cue, inhibitory or activational WM mechanisms predict contrasting results. When activation is the underlying mechanism for efficient processing, the prediction is that high memory span persons activate both meanings of the homonym equally in WM, whereas low memory span persons only have one meaning present. When inhibition is the underlying mechanism, the predictions are the reverse. The ERP data, in particular, the variations of the meaning related N400 component, showed clear evidence for inhibition as the underlying cognitive mechanism in high-span readers. For low-span participants the cueing towards the dominant or the subordinate meaning elicited an equivalently large N400 component suggesting that both meanings are active in WM. In high-span subjects, the dominant disambiguation cue elicited a smaller N400 than the subordinate one, indicating that for these subjects particularly the dominant meaning is active. The experiments showed that inhibitory processes are probably underlying WM used during language comprehension in high-span subjects. Moreover, they demonstrate that these subjects can use their inhibition in a more flexible manner than low-span subjects. The effects that these processing differences have on the efficiency of language parsing are discussed.

Adult↗

PubMed2003

Children processing music: electric brain responses reveal musical competence and gender differences.

Numerous studies investigated physiological correlates of the processing of musical information in adults. How these correlates develop during childhood is poorly understood. In the present study, we measured event-related electric brain potentials elicited in 5- and 9-year-old children while they listened to (major-minor tonal) music. Stimuli were chord sequences, infrequently containing harmonically inappropriate chords. Our results demonstrate that the degree of (in)appropriateness of the chords modified the brain responses in both groups according to music-theoretical principles. This suggests that already 5-year-old children process music according to a well-established cognitive representation of the major-minor tonal system and according to music-syntactic regularities. Moreover, we show that, in contrast to adults, an early negative brain response was left predominant in boys, whereas it was bilateral in girls, indicating a gender difference in children processing music, and revealing that children process music with a hemispheric weighting different from that of adults. Because children process, in contrast to adults, music in the same hemispheres as they process language, results indicate that children process music and language more similarly than adults. This finding might support the notion of a common origin of music and language in the human brain, and concurs with findings that demonstrate the importance of musical features of speech for the acquisition of language.

Acoustic Stimulation↗

PubMed2003

Prosody-assisted head-driven access to spoken German compounds.

Auditory processing of German 2-noun compound words was investigated with 328 participants in 4 experiments by monitoring semantic priming effects of the left constituents of the compound words. The authors demonstrated that there is no primacy of the left constituents in accessing auditorily presented German compound words in the mental lexicon. A clear priming effect of left constituents occurred only for compound words with a transparent right constituent that is the head of compound words in Germanic languages. The data suggest that the access to German compounds in the auditory domain involves 2 temporally overlapping routes: direct and decompositional. The prosodic structure (i.e., the duration) of the first morphemes of compound words appears to be a determining factor for activation of the decompositional route.

Adult↗

PubMed2003

Let's face the music: a behavioral and electrophysiological exploration of score reading.

This experiment was carried out to determine whether reading diatonic violations in a musical score elicits similar endogenous ERP components when hearing such violations in the auditory modality. In the behavioral study, musicians were visually presented with 120 scores of familiar musical pieces, half of which contained a diatonic violation. The score was presented in a measure-by-measure manner. Self-paced reading was significantly delayed for measures containing a violation, indicating that sight reading a violation requires additional effort. In the ERP study, the musical phrases were presented in a "RSVP"-like manner. We predicted that diatonic violations would elicit a late positive component. However, the ERP associated with the measure where a violation was presented showed a negativity instead. The negativity started around 100 ms and lasted for the entire recording period. This long-lasting negativity encompassed at least three distinct effects that were possibly related to violation detection, working memory processing, and a further integration/interpretation process.

Adult↗

PubMed2002

Music matters: preattentive musicality of the human brain.

During listening to a musical piece, unexpected harmonies may evoke brain responses that are reflected electrically as an early right anterior negativity (ERAN) and a late frontal negativity (N5). In the present study we demonstrate that these components of the event-related potential can be evoked preattentively, that is, even when a musical stimulus is ignored. Both ERAN and N5 differed in amplitude as a function of music-theoretical principles. Participants had no special musical expertise; results thus provide evidence for an automatic processing of musical information in onmusicians."

Adolescent↗

PubMed2002

Bach speaks: a cortical "language-network" serves the processing of music.

The aim of the present study was the investigation of neural correlates of music processing with fMRI. Chord sequences were presented to the participants, infrequently containing unexpected musical events. These events activated the areas of Broca and Wernicke, the superior temporal sulcus, Heschl's gyrus, both planum polare and planum temporale, as well as the anterior superior insular cortices. Some of these brain structures have previously been shown to be involved in music processing, but the cortical network comprising all these structures has up to now been thought to be domain-specific for language processing. To what extent this network might also be activated by the processing of non-linguistic information has remained unknown. The present fMRI-data reveal that the human brain employs this neuronal network also for the processing of musical information, suggesting that the cortical network known to support language processing is less domain-specific than previously believed.

Acoustic Stimulation↗