Biomedical subjects
Publications and source records attributed to M Kutas.
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.
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.
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.
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.
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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.
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Visual-evoked potentials recorded from the scalp of congenitally deaf adults were significantly larger over both auditory and visual cortical areas than in normal hearing adults. Over temporal and frontal areas peripheral stimuli presented at long intervals elicited N150 components which were larger in deaf than in hearing subjects. Over occipital and parietal areas peripheral and foveal stimuli elicited larger P230 components in deaf than in hearing subjects. These results imply that early auditory experience influences the organization of the human brain for visual processing.
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Event-related brain potentials (ERPs) were recorded from adults as they read 160 different sentences, half of which ended with a semantically anomalous word. These deviant words elicited a broad, negative component (N400). Measured in the difference wave between ERPs to incongruous and congruous endings, the N400 was slightly larger and more prolonged over the right than the left hemisphere and diminished in amplitude over the course of the experiment. A left-greater-than-right asymmetry was again observed in the slow, positive ERP elicited by the first six words in the sentences, being most pronounced for subjects having no left-handers in their immediate family.
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