Biomedical subjects

Marta Kutas

Publications and source records attributed to Marta Kutas.

At least 19 recordsLinked to original sources

PubMed2007

Verb aspect and the activation of event knowledge.

The authors show that verb aspect influences the activation of event knowledge with 4 novel results. First, common locations of events (e.g., arena) are primed following verbs with imperfective aspect (e.g., was skating) but not verbs with perfect aspect (e.g., had skated). Second, people generate more locative prepositional phrases as completions to sentence fragments with imperfective than those with perfect aspect. Third, the amplitude of the N400 component to location nouns varies as a function of aspect and typicality, being smallest for imperfective sentences with highly expected locations and largest for imperfective sentences with less expected locations. Fourth, the amplitude of a sustained frontal negativity spanning prepositional phrases is larger following perfect than following imperfective aspect. Taken together, these findings suggest a dynamic interplay between event knowledge and the linguistic stream.

Brain↗

PubMed2006

Abnormal typicality of responses on a category fluency task in schizotypy.

Existing hypotheses about semantic processing in schizophrenia and schizotypy suggest that both conditions are associated with a less than normal difference in the degree to which some concept activates the mental representation of other concepts that are strongly versus weakly related to it in meaning. To seek further evidence for this, we examined response typicality on the Category Fluency Test (CFT) as a function of schizotypy. Individuals from a non-clinical population verbally generated as many exemplars as they could in 1 min for each of four categories (fruits, four-footed animals, articles of clothing, vehicles). Participants subsequently completed the Schizotypal Personality Questionnaire (SPQ). SPQ score was not significantly correlated with the total number of responses generated for any of the categories. Individuals with higher (as opposed to lower) SPQ scores, however, generated more atypical members of the fruit category both in their initial responses and overall (as indexed by the average ratio of each response's ordinal position to its position in population typicality norms). These results support the hypothesis that semantic memory organization in non-clinical individuals with higher schizotypy is functionally altered.

Adolescent↗

PubMed2006

Interplay between computational models and cognitive electrophysiology in visual word recognition.

In this article, we discuss the relevance of electrophysiological data to the enterprise of analyzing and understanding the reading process. Specifically, we detail how the event-related brain potential (ERP) technique (and its magnetic counterpart) can aid in development of models of visual word recognition. Any viable and accurate account of reading must take into account the temporal and anatomical constraints imposed by the fact that reading is a human brain function. We believe that neurophysiological (especially, although not limited to electrophysiological) data can serve an essential reference in the development of biologically realistic models of reading. We assess just how well extant electrophysiological data comport with specific predictions of existing computational models and offer some suggestions for the kinds of research that can address some of the remaining open questions.

Brain↗

PubMed2006

Multiple effects of sentential constraint on word processing.

Behavioral and electrophysiological studies have uncovered different patterns of constraint effects on the processing of words in sentences. Whereas response time measures have indicated a reduced scope of facilitation from strongly constraining contexts, event-related brain potential (ERP) measures have instead revealed enhanced facilitation for semantically related endings in such sentences. Given this disparity, and the concomitant possibility of functionally separable stages of context effects, the current study jointly examined expectancy (cloze probability) and constraint effects on the ERP response to words. Expected and unexpected (but plausible) words completed strongly and weakly constraining sentences; unexpected items were matched for contextual fit across the two levels of constraint and were semantically unrelated to the most expected endings. N400 amplitudes were graded by expectancy but unaffected by constraint and seemed to index the benefit of contextual information. However, a later effect, in the form of increased frontal positivity from 500 to 900 ms post-stimulus-onset, indicated a possible cost associated with the processing of unexpected words in strongly constraining contexts.

Adult↗

PubMed2006

Absent event-related potential (ERP) word repetition effects in mild Alzheimer's disease.

OBJECTIVE: We hypothesized that an ERP word repetition paradigm, which reliably elicits and modulates the P600 and N400 components, would be particularly sensitive to the memory deficits and altered synaptic plasticity in mild Alzheimer's disease (AD). The P600 (a late positive component, or 'LPC'), and the N400, are sensitive indices of memory encoding and semantic processing, respectively. METHODS: We studied 11 patients with mild AD (mean MMSE=22.9) and 11 elderly (mean age=77.1) normal controls (NC) on a paradigm in which semantically 'congruous' category statement/exemplar pairs (50%) and 'incongruous' category statement/non-exemplar pairs (50%) repeat at 10-140 s intervals. A minimum of 19 channels ERP data were recorded and submitted to split-plot ANOVAs. RESULTS: Normal ERP data showed: (1) a significant word repetition effect for congruous words, with a wide-spread late positivity between approximately 300 and 800 ms post-stimulus (P600) that is larger for New than Old words; (2) a significant N400 repetition effect for incongruous words, with a right posterior negativity that is reduced for Old relative to New words. By contrast, neither of these word repetition effects was reliably present in the mild AD group. Good group discrimination was achieved by requiring that both these repetition effects were > or = the 10th percentile, with 100% sensitivity and 82% specificity. CONCLUSIONS: We found significant abnormalities of the N400 and P600 in mild AD, with both potentials showing markedly reduced sensitivity to word repetition. SIGNIFICANCE: The absence of normal N400 and LPC/P600 word repetition effects suggests impaired functioning of their neural generators, several of which are located in medial temporal lobe predilection sites (e.g. anterior fusiform, parahippocampal gyrus, hippocampus) for AD/tau pathology.

Aged↗

PubMed2006

Interpreting event-related brain potential (ERP) distributions: implications of baseline potentials and variability with application to amplitude normalization by vector scaling.

Recent proposals regarding the purpose and validity of amplitude normalization by vector scaling including mitigation of baseline and noise problems in between-condition difference analyses are critically evaluated. In so doing, we elaborate on some of the points raised in regarding baselines and noise, especially as these impact amplitude normalization by vector scaling and discuss the motivation for measuring event-related brain potential (ERP) amplitudes relative to a pre-stimulus baseline and the implications of this for certain (but not all) inferences. Throughout, our focus is on the logic of interpreting ERP measurements with an emphasis on the importance of specific assumptions and consideration of what conclusions are and are not supported.

Brain↗

PubMed2006

Combined perception of emotion in pictures and musical sounds.

Evaluation of emotional scenes requires integration of information from different modality channels, most frequently from audition and vision. Neither the psychological nor neural basis of auditory-visual interactions during the processing of affect is well understood. In this study, possible interactions in affective processing were investigated via event-related potential (ERP) recordings during simultaneous presentation of affective pictures (from IAPS) and affectively sung notes that either matched or mismatched each other in valence. To examine the role of attention in multisensory affect-integration ERPs were recorded in two different rating tasks (voice affect rating, picture affect rating) as participants evaluated the affect communicated in one of the modalities, while that in the other modality was ignored. Both the behavioral and ERP data revealed some, although non-identical, patterns of cross-modal influences; modulation of the ERP-component P2 suggested a relatively early integration of affective information in the attended picture condition, though only for happy picture-voice pairs. In addition, congruent pairing of sad pictures and sad voice stimuli affected the late positive potential (LPP). Responses in the voice affect rating task were overall more likely to be modulated by the concomitant picture's affective valence than vice versa.

Adult↗

PubMed2005

Association of schizotypy with semantic processing differences: an event-related brain potential study.

Disorganized speech in both schizophrenia and schizotypy has been hypothesized to result from abnormalities in how concepts activate one another in semantic memory. To study whether schizotypy is associated with differences in how categories activate their exemplars, we examined the N400 component of the event-related brain potential (ERP) elicited during a category-verification task. ERPs were recorded in young adults from the general population while they viewed category definitions each followed by a target that was either a high-typicality exemplar, low-typicality exemplar, or non-exemplar; participants' task was to indicate whether or not the target belonged to the category. Schizotypy was assessed via the Schizotypal Personality Questionnaire (SPQ). Overall, N400 amplitude was largest for non-exemplars, smallest for high-typicality exemplars, and intermediate for low-typicality exemplars. SPQ score was associated with decreased N400 amplitude to non-exemplars, and increased amplitude to both types of exemplars. SPQ score was negatively correlated with the N400 amplitude difference between non-exemplars and both low- and high-typicality exemplars, but was not correlated with the amplitude difference between low- and high-typicality exemplars. N400 amplitude differences between non-exemplars and both types of exemplars were correlated with the SPQ Interpersonal factor, but not the Disorganized factor. The results are consistent with an association of schizotypy with decreased use of context to activate related items and inhibit unrelated items.

Adolescent↗

PubMed2005

Probabilistic word pre-activation during language comprehension inferred from electrical brain activity.

Despite the numerous examples of anticipatory cognitive processes at micro and macro levels in many animal species, the idea that anticipation of specific words plays an integral role in real-time language processing has been contentious. Here we exploited a phonological regularity of English indefinite articles ('an' precedes nouns beginning with vowel sounds, whereas 'a' precedes nouns beginning with consonant sounds) in combination with event-related brain potential recordings from the human scalp to show that readers' brains can pre-activate individual words in a graded fashion to a degree that can be estimated from the probability that each word is given as a continuation for a sentence fragment offline. These findings are evidence that readers use the words in a sentence (as cues to their world knowledge) to estimate relative likelihoods for upcoming words.

Adult↗

PubMed2005

Processing semantic anomalies in two languages: an electrophysiological exploration in both languages of Spanish-English bilinguals.

The latency of the brain response to semantic anomalies (N400 effect) has been found to be longer in a bilingual's second language (L2) than in their first language (L1) and/or to that seen in monolinguals. This has been explained in terms of late exposure to L2, although age of exposure and language proficiency are often highly correlated. We thus examined the relative contributions of these factors not only in L2 but also in L1 in a group of Spanish-English bilinguals for whom age of exposure and language proficiency were not highly correlated by recording event-related brain potentials (ERPs) to semantically congruous/incongruous words completing written sentences. We also divided our bilinguals into a Spanish-dominant subset who had late exposure and reduced vocabulary proficiency [as measured by Boston Naming Test (BNT) and Verbal Fluency Scores] in L2 (English) relative to L1 (Spanish) and an English-dominant group who had early exposure to both their languages although greater proficiency in English than in Spanish. In both groups, the N400 effect was significantly later in the nondominant than the dominant language. Although this slowing could be due to late exposure to English in the Spanish-dominant group, late exposure cannot explain the slowing in Spanish in the English-dominant group. Overall, we found that vocabulary proficiency and age of exposure are both important in determining the timing of semantic integration effects during written sentence processing--with vocabulary proficiency predicting the timing of semantic analysis in L1 and both age of exposure and language proficiency, although highly correlated, making additional small but uncorrelated contributions to the speed of semantic analysis/integration in L2.

Adult↗

PubMed2005

Right hemisphere sensitivity to word- and sentence-level context: evidence from event-related brain potentials.

Researchers using lateralized stimuli have suggested that the left hemisphere is sensitive to sentence-level context, whereas the right hemisphere (RH) primarily processes word-level meaning. The authors investigated this message-blind RH model by measuring associative priming with event-related brain potentials (ERPs). For word pairs in isolation, associated words elicited more positive ERPs than unassociated words with similar magnitudes and onset latencies in both visual fields. Embedded in sentences, these same pairs showed large sentential context effects in both fields. Small effects of association were observed, confined to incongruous sentences after right visual hemifield presentation but present for both congruous and incongruous sentences after left visual hemifield presentation. Results do not support the message-blind RH model but do suggest hemispheric asymmetries in the use of word and sentence context during real-time processing.

Adult↗

PubMed2005

Mismaking memories: neural precursors of memory illusions in electrical brain activity.

Memory illusions--vivid experiences of events that never occurred--could result from inaccuracies either in retrieving memories or in initially storing them. In two experiments, people studied lists of associated words that either did or did not induce later illusory (false) memories of associated but nonpresented lure words. The amplitude of the electrical brain activity during study of words (approximately 500-1,300 ms) that were themselves later correctly remembered reliably distinguished list words that led to such illusory memories from those that did not. This encoding difference associated with subsequent illusory memory (referred to as a DIM)--presumably reflecting item-specific encoding differences--is a neural precursor of memory illusions.

Brain↗

PubMed2005

Aging in context: age-related changes in context use during language comprehension.

Effects of normal aging on the use of sentence context information during language comprehension were examined by measuring younger and older adults' event-related potential (ERP) responses to congruent sentence-final words as a function of contextual constraint. Half of the sentence contexts were strongly constraining, rendering the target word very predictable, whereas the other half were weakly constraining. Both age groups elicited smaller N400 responses to target words in strongly than in weakly constrained contexts, but this effect was significantly smaller and later for older adults. Older adults with lower reading spans showed greater delays. Age-related changes were driven primarily by decreases in older adults' ability to make use of the richer information available from strongly constraining contexts to guide semantic processing, as word processing (N400s) in weak contexts was qualitatively and quantitatively similar in the two age groups.

Adolescent↗

PubMed2005

Event-related potential correlates of long-term memory for briefly presented faces.

Electrophysiological studies have investigated the nature of face recognition in a variety of paradigms; some have contrasted famous and novel faces in explicit memory paradigms, others have repeated faces to examine implicit memory/priming. If the general finding that implicit memory can last for up to several months also holds for novel faces, a reliable measure of it could have practical application for eyewitness testimony, given that explicit measures of eyewitness memory have at times proven fallible. The current study aimed to determine whether indirect behavioral and electrophysiological measures might yield reliable estimates of face memory over longer intervals than have typically been obtained with priming manipulations. Participants were shown 192 faces and then tested for recognition at four test delays ranging from immediately up to 1 week later. Three event-related brain potential components (e.g., N250r, N400f, and LPC) varied with memory measures although only the N250r varied regardless of explicit recognition, that is, with both repetition and recognition.

Adolescent↗

PubMed2005

Both sides get the point: hemispheric sensitivities to sentential constraint.

Behavioral studies have consistently reported striking differences in the impact of sentence-level information on the processing of words presented in the right (RVF) versus the left (LVF) visual field, with context effects apparent only for RVF items. The consistent lack of such effects in the LVF has been taken to mean that right hemisphere language comprehension is largely insensitive to message-level meaning. We used the functional specificity afforded by event-related potential measures to assess this claim. Target words completing strongly and weakly constraining sentence contexts, in which constraint arose at the sentence level rather than from lexical associations, were presented laterally in the LVF or RVF. Increased constraint significantly reduced N400 amplitudes with presentation in both VFs, with no differences in the timing or amplitude of these effects. These results are inconsistent with the view that the VF asymmetries found in behavioral measures reflect differential hemispheric capacities at the level of semantic analysis and integration, although VF-based differences on earlier components (P2) suggest asymmetries in the impact of sentential context on perceptual aspects of word processing in the two hemispheres.

Adolescent↗

PubMed2004

Syntactic processing with aging: an event-related potential study.

To assess age-related changes in simple syntactic processing with normal aging, event-related brain potentials (ERPs) elicited by grammatical number violations as individuals read sentences for comprehension were analyzed. Violations were found to elicit a P600 of equal amplitude and latency regardless of an individual's age. Instead, advancing age was associated with a change in the scalp distribution of the P600 effect, being less asymmetric and more frontal (though still with a parietal maximum) in older than younger adults. Our results thus show that the brain's response to simple syntactic violations, unlike those reported for simple binary categorizations and simple semantic violations, is neither slowed nor diminished in amplitude by age. At the same time, the brain's processing of these grammatical number violations did engage at least somewhat different brain regions as a function of age, suggesting a qualitative change rather than any simple quantitative change in speed of processing.

Adolescent↗

PubMed2004

Automatic removal of eye movement and blink artifacts from EEG data using blind component separation.

Signals from eye movements and blinks can be orders of magnitude larger than brain-generated electrical potentials and are one of the main sources of artifacts in electroencephalographic (EEG) data. Rejecting contaminated trials causes substantial data loss, and restricting eye movements/blinks limits the experimental designs possible and may impact the cognitive processes under investigation. This article presents a method based on blind source separation (BSS) for automatic removal of electroocular artifacts from EEG data. BBS is a signal-processing methodology that includes independent component analysis (ICA). In contrast to previously explored ICA-based methods for artifact removal, this method is automated. Moreover, the BSS algorithm described herein can isolate correlated electroocular components with a high degree of accuracy. Although the focus is on eliminating ocular artifacts in EEG data, the approach can be extended to other sources of EEG contamination such as cardiac signals, environmental noise, and electrode drift, and adapted for use with magnetoencephalographic (MEG) data, a magnetic correlate of EEG.

Algorithms↗

PubMed2004

Anticipating words and their gender: an event-related brain potential study of semantic integration, gender expectancy, and gender agreement in Spanish sentence reading.

Recent studies indicate that the human brain attends to and uses grammatical gender cues during sentence comprehension. Here, we examine the nature and time course of the effect of gender on word-by-word sentence reading. Event-related brain potentials were recorded to an article and noun, while native Spanish speakers read medium- to high-constraint Spanish sentences for comprehension. The noun either fit the sentence meaning or not, and matched the preceding article in gender or not; in addition, the preceding article was either expected or unexpected based on prior sentence context. Semantically anomalous nouns elicited an N400. Gender-disagreeing nouns elicited a posterior late positivity (P600), replicating previous findings for words. Gender agreement and semantic congruity interacted in both the N400 window--with a larger negativity frontally for double violations--and the P600 window--with a larger positivity for semantic anomalies, relative to the prestimulus baseline. Finally, unexpected articles elicited an enhanced positivity (500-700 msec post onset) relative to expected articles. Overall, our data indicate that readers anticipate and attend to the gender of both articles and nouns, and use gender in real time to maintain agreement and to build sentence meaning.

Adolescent↗