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M Kutas

Publications and source records attributed to M Kutas.

At least 55 records · Page 3Linked to original sources
PubMed1997

Early brain potentials link repetition blindness, priming and novelty detection.

To study mechanisms of visual object identification in humans, event-related potentials (ERPs) were recorded during successful or unsuccessful identification of rapid, serially presented words (unrepeated or repeated). We observed 'repetition blindness' (RB): more repeated than unrepeated words were incorrectly reported. ERPs from repetition-blinded words exhibited little or none of the enhanced positivity found for correctly reported repeated words, resembling instead ERPs from any unrepeated sequence initially, but only incorrectly reported unrepeated sequences later. Thus it appears that in RB an early (220 ms) neural operation that normally initiates facilitated processing from immediate repetition priming erroneously processes a repeated item as novel. This operation (possibly in basotemporal neocortex) appears to induce differential subsequent processing of novel vs repeated information.

Adolescent↗
PubMed1997

Human temporal lobe potentials in verbal learning and memory processes.

Animal experiments and lesion studies have shown the importance of temporal lobe structures for language and memory. We recorded intracranial cognitive potentials from the human lateral and medial temporal lobe in 26 patients with temporal lobe epilepsy undergoing presurgical evaluation, using a word- and a picture-recognition paradigm. Neuropsychological testing included word fluency, verbal reasoning, sustained attention and a verbal learning memory test (VLMT), which was an adapted version of the Rey auditory verbal learning test. Word-specific N400-potentials elicited in the middle temporal gyrus of the dominant left hemisphere (LTL-N400) predicted immediate recall performance after learning, whereas N400s, elicited by words but not pictures in the left anterior medial temporal lobe (AMTL-N400), predicted delayed recall. The number of words that were learned but forgotten after a 30-min delay correlated only with N400s elicited by words in the left anterior medial temporal lobe. Thus, intracranial recordings indicated that different electrophysiological responses in different temporal lobe structures were linked to memory scores from specific neuropsychological tests.

Adolescent↗
PubMed1997

Event-related potentials elicited by spoken relative clauses.

Sentence-length event-related potential (ERP) waveforms were obtained from 23 scalp sites as 24 subjects listened to normally spoken sentences of various syntactic structures. The critical materials consisted of 36 sentences each containing one of two types of relative clauses that differ in processing difficulty, namely Subject Object (SO) and Subject Subject (SS) relative clauses. Sentence-length ERPs showed several differences in the slow scalp potentials elicited by SO and SS sentences that were similar in their temporal dynamics to those elicited by the same stimuli in a word-by-word reading experiment, although the effects in the two modalities have non-identical distributions. Just as for written sentences, there was a large, fronto-central negativity beginning at the linguistically defined "gap" in the SO sentences; this effect was largest for listeners with above-median comprehension rates and is hypothesized to index changes in on-line processing demands during comprehension.

Adolescent↗
PubMed1997

Views on how the electrical activity that the brain generates reflects the functions of different language structures.

Human language is what it is because of its function and its implementation. We are far from understanding how language comprehension is carried out by the human brain. This task can be made easier by considering that evidence for the what and how of language comes from the study of linguistics, psychology, and neuroscience. The approach outlined herein describes how these different sources of evidence can be combined in studies of written and spoken sentence processing by using a measure of the brain's electrical activity. The outcome is a more temporally precise view of the analysis of language structures in our minds and brains.

Brain↗
PubMed1997

An ERP analysis of implicit structured sequence learning.

When task exposure facilitates performance without producing corresponding changes in verbalizable knowledge, learning is said to be implicit. In Experiment 1, event-related potentials (ERPs) were recorded as individuals practiced an implicit structured sequence learning (ISSL) task wherein only some target events required a response. With practice, the ERPs to targets that obeyed the underlying grammar diverged from those that did not at around 200 ms; grammatical targets appeared to be more positive between 200 and 500 ms because a similar positivity for the ungrammatical targets was delayed. In Experiment 2, the grammar was simplified allowing a direct comparison to be made between an implicit learning group and an explicit group, who were taught the grammar prior to recording. The results of the comparison revealed a remarkable similarity but did implicate at least partially nonidentical neural mechanisms in implicit and explicit structured sequence learning.

Adult↗
PubMed1996

What's in a name? Electrophysiological differences between spoken nouns, proper names and one's own name.

To investigate the neural processing of different word categories, we recorded event-related potentials (ERPs) from 32 individuals listening to sentences, beginning either with a proper name (first name), the subject's own name, or a common noun. Names and nouns both elicited ERP waveforms with the same early componentry, but the N1 and P2 components were larger for proper names than common nouns. The ERPs to the subject's own name also had a large N1/P2 plus a prominent negativity at parieto-central site peaking around 400 ms and a late positivity between 500-800 ms over left lateral-frontal sites. These findings are consistent with differential processing of people's first names within the category of nouns.

Acoustic Stimulation↗
PubMed1996

Electrophysiological insights into the nature of the semantic deficit in Alzheimer's disease.

Event-related brain potential (ERP) and reaction-time measures were used to determine if the specificity of a category prime differentially affects the amount of semantic priming seen in patients with dementia of the Alzheimer type (DAT) compared with normal elderly and young controls. Subjects were primed with an auditory category name followed by the visually presented name of an imageable object and indicated whether the object was a category member; the category was either superordinate to, at, or subordinate to the basic level. All groups showed similar priming effects in response to the category manipulation, as evidenced in both reaction time and the amplitude of the N400 component of the ERP. Overall, DAT subjects showed the smallest ERP priming effects and young controls the largest. The present study did not provide evidence for a strong version of a strictly "bottom-up" breakdown of the semantic networks in subjects with DAT, suggesting a role for factors such as task difficulty and memory search strategies in online categorization tasks of this type.

Adolescent↗
PubMed1996

Event-related brain potentials during semantic categorization in normal aging and senile dementia of the Alzheimer's type.

To assess the effects of normal aging and senile dementia of the Alzheimer's type (SDAT) on semantic analysis of words, we examined the N400 component of the event-related potential (ERP) elicited during the processing of highly constrained (opposites) and less constrained materials (category-category exemplars) in 12 young control subjects, 12 elderly control subjects and 12 patients with SDAT. We employed a priming paradigm in which a context phrase was spoken and a target word (congruent or incongruent) was presented visually. The N400 effect was reduced in amplitude and delayed in the elderly control group relative to that of the younger subjects, and was further attenuated in amplitude, delayed in latency and somewhat flatter in its distribution across the scalp in the SDAT patients. These findings are consistent with less efficient processing and integration of lexical items with semantic context in normal aging, which is further exacerbated by SDAT. Differences in the N400 range associated with the opposite and category conditions were observed only in the young subjects, suggesting less use of controlled attentional resources or perhaps weaker associative links with age.

Adult↗
PubMed1995

Semantic processing and memory for attended and unattended words in dichotic listening: behavioral and electrophysiological evidence.

Thirty-two Ss studied words presented to 1 ear, while ignoring a concurrent word list presented to the opposite ear. The N400 component of the event-related potentials elicited by attended words was modulated by semantic priming between successive words. The N400 elicited by unattended words was insensitive to semantic manipulation. Recognition memory was better for attended than for unattended words. However, the percentage of false positives was elevated equally for lures that were semantically related to "old" words, whether they had been attended or unattended. Words that were initially attended induced similar repetition effects in a lexical decision task as words that were initially unattended. Hence, both attended and unattended words are semantically processed and activate semantic representations. However, attended words from traces that are subsequently more available to conscious recollection than unattended words.

Adult↗
PubMed1994

Effects of aging on event-related brain potentials (ERPs) in a visual detection task.

Event-related brain potentials (ERPs) were recorded from 74 subjects (45 men) between 18 and 82 years of age in a simple visual detection task. On each trial the subject reported the location of a triangular flash of light presented briefly 20 degrees laterally to the left or right visual field or to both fields simultaneously. ERPs to targets exhibited a similar morphology including P1, N1, P2, N2, and P3 components across all age groups. The principal effects of advancing age were (1) a marked reduction in amplitude of the posterior P1 component (75-150 latency) together with an amplitude increase of an anterior positivity at the same latency; (2) an increase in amplitude of the P3 component that was most prominent over frontal scalp areas; and (3) a linear increase in P3 peak latency. These results extend the findings of age-related changes in P3 peak latency and distribution to a non-oddball task in the visual modality and raise the possibility that short-latency ERPs may index changes in visual attention in the elderly.

Adolescent↗
PubMed1994

Focusing on the N400: an exploration of selective attention during reading.

In a series of two experiments, subjects read sentences wherein words were flanked in the lower visual field by irrelevant words (i.e., flankers). The visual angle between the words in the sentence and the flanker words was manipulated (i.e., 0.57 degrees, 0.97 degrees, 1.37 degrees). Sentence endings were either congruent or incongruent; incongruent endings elicited a large N400 component. Flanker effects were observed for sentence final words on electrophysiological measures during the reading task and on subsequent recognition memory performance for sentence final and new words. For both measures, the flanker effect interacted with the congruency of the sentence ending as well as the visual angle between the sentence final word and its flanker. The largest and earliest flanker effects were observed for congruent endings at the smallest visual angle (0.57 degrees); congruent endings and flankers in intermediate visual angle (0.97 degrees) conditions displayed a similar flanker-related negativity but with a longer onset latency (490 vs. 280 ms). Congruent endings and their flankers in the largest visual angle (1.57 degrees) conditions revealed no flanker effect.

Adult↗
PubMed1993

The many facets of repetition: a cued-recall and event-related potential analysis of repeating words in same versus different sentence contexts.

Event-related potential (ERP) and cued-recall performance were used to investigate the influence of (a) context, (b) repeating a word's meaning to word repetition priming, and (c) repetition on the ERP difference related to memory (Dm). Sentences ended with either nonhomographs or homographs. For nonhomographs, either the sentence context, the final word, both, or neither were repeated. Homographs were repeated in their original context or in new sentences that biased the same or an alternative meaning. Large repetition effects were found for all words repeated in their original contexts; in contrast, changing contexts led to no repetition effects whether the meaning of the repeated words was preserved or not. These results favor an episodic contribution to word repetition priming and suggest a common process for Dm and repetition.

Adult↗
PubMed1993

Electrophysiological evidence for task effects on semantic priming in auditory word processing.

Event-related brain potentials (ERPs) associated with semantic relatedness were recorded in two auditory word recognition tasks. In the Memorize task, subjects listened to a list of words in anticipation of a subsequent recognition test. In the Count Nonwords task, subjects silently counted the number of nonwords occurring within a list of words. Within each list, target words were either semantically related or unrelated to the immediately preceding word. As in comparable visual tasks, the amplitude of a negative ERP component (N400) was significantly attenuated when targets were preceded by semantically related primes. This attenuation was greater in the Memorize than in the Count Nonwords task. These data are consistent with the view that the sensitivity of N400 amplitude to semantic relatedness is modulated by task variables that manipulate depth of processing.

Adult↗
PubMed1993

Effects of aging on event-related brain potentials and reaction times in an auditory oddball task.

Auditory event-related potentials (ERPs) were recorded from 71 healthy individuals between 18 and 82 years of age during performance of a disjunctive reaction time task in an auditory oddball paradigm. The effects of aging on reaction times and on the latencies, amplitudes, and distributions of each of the main ERP components were examined. No significant slowing of the reaction times of the elderly subjects was observed in relation to the younger ones. The peak latencies of both the N1 and P2 components elicited by standard tones were slightly but significantly slowed with age. In the ERPs of target tones, the later, endogenous components (N2, P3, and SW) showed linear increases in latency as a function of age; the later the component, the longer the age-related delay. In general, aging was associated with less negativity (both N2 and SW) and more positivity (P3) over the anterior scalp, together with a smaller P3 and a more pronounced N2 over posterior scalp areas. Most of the effects observed in target ERPs were also evident in the difference waves derived from subtraction of the standard from the target ERPs, although the slope of the age-related latency increase of N2 was shallower and that of the P3 was steeper in the difference ERPs. These findings are discussed in relation to previous accounts of ERP changes with aging.

Adult↗
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↗