PubMed Health⌕ Search

Biomedical subjects

M Kutas

Publications and source records attributed to M Kutas.

At least 19 recordsLinked to original sources
PubMed1991

Influences of semantic and syntactic context on open- and closed-class words.

Event-related potentials (ERPs) were recorded as subjects read semantically meaningful, syntactically legal but nonsensical and random word strings. The constraints imposed by formal sentence structure alone did not reduce the amplitude of the N400 component elicited by open-class words, whereas semantic constraints did. Semantic constraints also eliminated the word-frequency effect of a larger N400 for low-frequency words. Responses to closed-class words exhibited reduced N400 amplitudes in syntactic and congruent sentences, indicating that formal sentence structure placed greater restrictions on closed-class words than it did on open-class words. However, unlike the open-class results, the impact of sentence context on closed-class words was stable across word positions, suggesting that these syntactic constraints were applied only locally. A second ERP component, distinct from the N400, was elicited primarily by congruent closed-class words.

Adolescent↗
PubMed1990

Interactions between sentence context and word frequency in event-related brain potentials.

Event-related brain potentials (ERPs) were recorded as subjects silently read a set of unrelated sentences. The ERP responses elicited by open-class words were sorted according to word frequency and the ordinal position of the eliciting word within its sentence. We observed a strong inverse correlation between sentence position and the amplitude of the N400 component of the ERP. In addition, we found that less frequent words were associated with larger N400s than were more frequent words, but only if the eliciting words occurred early in their respective sentences. We take this interaction between sentence position and word frequency as evidence that frequency does not play a mandatory role in word recognition, but can be superseded by the contextual constraint provided by a sentence.

Adolescent↗
PubMed1989

Human callosal function: MRI-verified neuropsychological functions.

A commissurotomy patient, with MRI-revealed sparing of some rostral and splenial fibers of the corpus callosum, judged whether pairs of words rhymed. We presented one word in each pair to her left visual field and the other to her right visual field. The 2 words in each pair either sounded and looked alike (R + L +), sounded alike but looked different (R + L -), sounded different but looked alike (R - L +), or both sounded and looked different (R - L -). Although in previous studies the patient has demonstrated little or no ability to transfer information between her brain hemispheres, she was able to perform the rhyming judgment significantly better than chance when the words both looked and sounded alike. However, her accuracy did not differ from chance in the other 3 conditions, or when she was asked to indicate if 2 letters presented to her opposing visual fields were the same or different. A second commissurotomy patient, with an MRI-verified full callosal section, performed at chance in all conditions, and normal control subjects were significantly better than chance in all conditions but R + L -. We discuss the results in terms of the specificity of the information carried by groups of callosal fibers.

Adult↗
PubMed1989

[A case presenting differential diagnostic difficulties in eosinophilic gastritis].

The diagnosis of eosinophilic gastritis in a 45 year old man was definitely established only through laparotomy, after inconclusive radiological, endoscopical and biopsy histological findings. The diagnostic difficulties in this particular case were characteristic for this condition, as evident from the literature.

Diagnosis, Differential↗
PubMed1988

Event-related potential asymmetries during the reading of sentences.

This report is an overview of the lateral distribution of event-related brain potentials (ERPs) recorded during silent reading in 7 different experiments. Both single word and cross-sentence averages revealed the presence of several ERP asymmetries. The P1, P2 and a negativity between 300 and 500 msec were found to be larger over the right than the left hemisphere. It was argued that this asymmetric negativity was due primarily to the contribution of the N400 elicited by all content words. The degree of N400 asymmetry was unaffected either by the rate of sentence presentation or the ratio of congruent to incongruent sentences but was quite sensitive to family history of left-handedness. In contrast, the P1 and P2 asymmetries were uninfluenced by lexical class or familial sinistrality.

Dominance, Cerebral↗
PubMed1988

Processing of semantic anomaly by right and left hemispheres of commissurotomy patients. Evidence from event-related brain potentials.

The ability of 5 commissurotomized patients to appreciate semantic anomalies presented to their right and left hemispheres was tested using both electrophysiological and behavioural measures. In all cases, the patients heard sentence fragments that were completed either by semantically congruous or incongruous words briefly flashed to the left visual field, right visual field or to both fields simultaneously. A dissociation between behavioural and event-related brain potential (ERP) measures was observed. All 5 patients were able to indicate by a pointing response with greater than chance accuracy whether the terminal word of a sentence made sense (i.e., appropriate for the context) or was nonsensical. This was true regardless of the hemisphere receiving the terminal word. Likewise, all the patients responded to right visual field anomalies with a cerebral potential (N400) that was typically elicited by such words in control subjects. In contrast, only those 2 patients who developed an overt speech capability under the control of the right hemisphere produced N400 waves in response to left visual field anomalies. These findings were interpreted as suggesting possible relationships within language generation and semantic priming.

Adolescent↗
PubMed1988

The use of event-related potentials in the study of brain asymmetries.

The utility of event-related brain potentials (ERPs) in the study of hemispheric specialization is discussed in the context of three experimental cases: the application of motor potentials to the "continuous flow" model of human information processing, investigations of the role of early experience in cerebral organization, and hemispheric asymmetries in phonemic recoding during reading. The importance of the electrical reference in ERP records is stressed.

Brain↗
PubMed1987

Neural correlates of encoding in an incidental learning paradigm.

Event-related brain potentials (ERPs) were recorded during an incidental learning paradigm. Recall and recognition were better for words initially presented in tasks requiring semantic decisions (i.e., 'is it living?' or 'is it edible?') than for words in tasks requiring non-semantic decisions. ERPs elicited during performance of these tasks were predictive of subsequent memory performance. A late positive ERP elicited by words later recalled or recognized was larger than that elicited by words later forgotten. This enhanced positivity for to-be-remembered words could be accounted for, in part, by the fact that words in semantic tasks were remembered better and elicited larger ERPs than did words in non-semantic tasks. Similarly, words followed by affirmative rather than negative decisions were associated both with better recognition and with larger ERPs. However, ERPs were sensitive to processes that influenced later memory performance even within an individual semantic task and within the affirmative decision condition. In addition, results showed that the ERP differences based on later memory performance did not necessarily arise from amplitude variation in P3 waves that occurred at the same time.

Adolescent↗
PubMed1977

Augmenting mental chronometry: the P300 as a measure of stimulus evaluation time.

A technique for measuring the latency of the P300 component of event-related brain potentials on individual trials is described. Choice reaction times and the latency of the P300 were compared under speed-maximizing and under accuracy-mazimising instructions. The choice stimuli required different levels of semantic categorization. The data support the proposition that the latency of P300 corresponds to stimulus evaluation time and is independent of response selection.

Brain↗
PubMed1975

On the independence of the CNV and the P300 components of the human averaged evoked potential.

We report an experiment designed to assess the interactions between the CNV and the P300 components of human event-related potential. Eight subjects were each presented with series of experimental trials on all of which either a 1200 c/sec or an 800 c/sec tone was presented. There were three independent variables: (a) The presence or absence of a warning flash 1000 msec prior to the tone. (b) The task assigned to the subject--that is subjects were either to make a discriminative response to the tone or, on half the series, to predict prior to the tiral which of the two tones would be presented. (c) The predictability of the tone frequency. On half the series high and low tones alternated from trial to trial. On the other series, tones were chosen randomly on each trial. The data show that the amplitude of the P300 component is not affected by the presence or absence of a warning stimulus. Furthermore, the distributions of P300 and the CNV over the scalp are quite different. These conclusions are supported by a principal component and a discriminant analysis of the data. We conclude that the CNV and the P300 reflect the activity of functionally distinct cortical mechanisms.

Analysis of Variance↗